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Sample records for opalinus clay radionuclide

  1. Coupled Transport Phenomena in the Opalinus Clay: Implications for Radionuclide Transport

    International Nuclear Information System (INIS)

    Soler, J.M.

    1999-09-01

    Coupled phenomena (thermal and chemical osmosis, hyperfiltration, coupled diffusion, thermal diffusion, thermal filtration, Dufour effect) may play an important role in fluid, solute and heat transport in clay-rich formations, such as the Opalinus Clay (OPA), which are being considered as potential hosts for radioactive waste repositories. In this study, the potential effects of coupled phenomena on radionuclide transport in the vicinity of a repository for vitrified high-level radioactive waste (HLW) and spent nuclear fuel (SF) hosted by the Opalinus Clay, at times equal to or greater than the expected lifetime of the waste canisters (about 1000 years), have been addressed. Firstly, estimates of the solute fluxes associated with chemical osmosis, hyperfiltration, thermal diffusion and thermal osmosis have been calculated. Available experimental data concerning coupled transport phenomena in compacted clays, and the hydrogeological and geochemical conditions to which the Opalinus Clay is subject, have been used for these estimates. These estimates suggest that thermal osmosis is the only coupled transport mechanism that could have a strong impact on solute and fluid transport in the vicinity of the repository. Secondly, estimates of the heat fluxes associated with thermal filtration and the Dufour effect in the vicinity of the repository have been calculated. The calculated heat fluxes are absolutely negligible compared to the heat flux caused by thermal conduction. As a further step to obtain additional insight into the effects of coupled phenomena on solute transport, the solute fluxes associated with advection, chemical diffusion, thermal and chemical osmosis, hyperfiltration and thermal diffusion have been incorporated into a simple one-dimensional transport equation. The analytical solution of this equation, with appropriate parameters, shows again that thermal osmosis is the only coupled transport mechanism that could have a strong effect on repository

  2. Coupled Transport Phenomena in the Opalinus Clay: Implications for Radionuclide Transport

    Energy Technology Data Exchange (ETDEWEB)

    Soler, J.M.

    1999-09-01

    Coupled phenomena (thermal and chemical osmosis, hyperfiltration, coupled diffusion, thermal diffusion, thermal filtration, Dufour effect) may play an important role in fluid, solute and heat transport in clay-rich formations, such as the Opalinus Clay (OPA), which are being considered as potential hosts for radioactive waste repositories. In this study, the potential effects of coupled phenomena on radionuclide transport in the vicinity of a repository for vitrified high-level radioactive waste (HLW) and spent nuclear fuel (SF) hosted by the Opalinus Clay, at times equal to or greater than the expected lifetime of the waste canisters (about 1000 years), have been addressed. Firstly, estimates of the solute fluxes associated with chemical osmosis, hyperfiltration, thermal diffusion and thermal osmosis have been calculated. Available experimental data concerning coupled transport phenomena in compacted clays, and the hydrogeological and geochemical conditions to which the Opalinus Clay is subject, have been used for these estimates. These estimates suggest that thermal osmosis is the only coupled transport mechanism that could have a strong impact on solute and fluid transport in the vicinity of the repository. Secondly, estimates of the heat fluxes associated with thermal filtration and the Dufour effect in the vicinity of the repository have been calculated. The calculated heat fluxes are absolutely negligible compared to the heat flux caused by thermal conduction. As a further step to obtain additional insight into the effects of coupled phenomena on solute transport, the solute fluxes associated with advection, chemical diffusion, thermal and chemical osmosis, hyperfiltration and thermal diffusion have been incorporated into a simple one-dimensional transport equation. The analytical solution of this equation, with appropriate parameters, shows again that thermal osmosis is the only coupled transport mechanism that could have a strong effect on repository

  3. Time-dependent Flow and Transport Calculations for Project Opalinus Clay (Entsorgungsnachweis)

    International Nuclear Information System (INIS)

    Kosakowski, G.

    2004-07-01

    This report describes two specific assessment cases used in the safety assessment for a proposed deep geological repository for spent fuel, high level waste and long-lived intermediate-level waste, sited in the Opalinus Clay of the Zuercher Weinland in northern Switzerland (Project Entsorgungsnachweis, NAG RA, 2002d). In this study the influence of time dependent flow processes on the radionuclide transport in the geosphere is investigated. In the Opalinus Clay diffusion dominates the transport of radionuclides, but processes exist that can locally increase the importance of the advective transport for some time. Two important cases were investigated: (1) glaciation-induced flow due to an additional overburden in the form of an ice shield of up to 400 m thickness and (2) fluid flow driven by tunnel convergence. For the calculations the code FRAC3DVS (Therrien and Sudicky, 1996) was used. FRAC3DVS solves the three-dimensional flow and transport equation in porous and fractured media. For the case of glaciation-induced flow (1) a two-dimensional reference model without glaciations was calculated. During the glaciations the geosphere release-rates are up to a factor of about 1.7 higher compared to the reference model. The influence of glaciations on the transport of cations or neutral species is less than for anions, since the importance of the advective transport for anions is higher due to the lower accessible porosity for anions. The increase in the release rates during glaciations is lower for sorbing compared to non-sorbing radionuclides. The influence of the tunnel convergence (2) on the transport of radionuclides in the geosphere is very small. Due to the higher source term the geosphere release rates are slightly higher if tunnel convergence is considered. In addition to the two assessment cases this report investigates the applicability of the one-dimensional approximation for modelling transport through the Opalinus Clay. For the reference case of the safety

  4. Assessment of geomechanical properties of intact Opalinus Clay - Expert report

    International Nuclear Information System (INIS)

    Amann, F.; Vogelhuber, M.

    2015-11-01

    This comprehensive report published by the Swiss Federal Nuclear Safety Inspectorate ENSI presents an expert report published on the assessment of the geomechanical properties of intact Opalinus Clay. This review report addresses the conceptual constitutive framework for repositories in Opalinus Clay. The author addresses the geomechanical fundamentals that are necessary in order to adequately judge experiments on intact Opalinus Clay and the interpretation of the results. The report assesses in detail the various test series on intact Opalinus Clay carried out along with the interpretations made by experts and NAGRA. Further assessments are quoted including those on sample geometries tested, effective strength properties, undrained shear strength properties and elastic properties. The results of work done by other experts are also presented and discussed. The report is completed with a list of relevant literature

  5. Assessment of geomechanical properties of intact Opalinus Clay - Expert report

    Energy Technology Data Exchange (ETDEWEB)

    Amann, F. [Eidgenössische Technische Hochschule ETHZ, Zürich (Switzerland); Vogelhuber, M. [Dr. von Moos AG, Geotechnisches Büro, Zürich (Switzerland)

    2015-11-15

    This comprehensive report published by the Swiss Federal Nuclear Safety Inspectorate ENSI presents an expert report published on the assessment of the geomechanical properties of intact Opalinus Clay. This review report addresses the conceptual constitutive framework for repositories in Opalinus Clay. The author addresses the geomechanical fundamentals that are necessary in order to adequately judge experiments on intact Opalinus Clay and the interpretation of the results. The report assesses in detail the various test series on intact Opalinus Clay carried out along with the interpretations made by experts and NAGRA. Further assessments are quoted including those on sample geometries tested, effective strength properties, undrained shear strength properties and elastic properties. The results of work done by other experts are also presented and discussed. The report is completed with a list of relevant literature.

  6. Clay shale as host rock. A geomechanical contribution about Opalinus clay

    International Nuclear Information System (INIS)

    Lempp, Christof; Menezes, Flora; Sachwitz, Simon

    2016-01-01

    The Opalinuston is a prominent rock representing the type of organic clay shales or clay stones within the sequence of Triassic and Jurassic marine sediments in Southern Germany. The rock forms a homogenous unit some ten meters thick. The degree of consolidation of this type of pelitic rock depends mainly on the former load conditions, but is also dependent on the long-term weathering and even on the present exposition. The geomechanical parameters such as shear strength, tensional strength and permeability vary with the state of consolidation and become important when the use is discussed of such rocks for radioactive waste disposal. A tunneling project at the northern escarpment of the Swabian Alb (Southwest Germany) within the Opalinus clay offered the rare opportunity to obtain fresh unweathered rock samples in greater amounts compared to fresh drilling cores from which geomechanical investigations are usually undertaken. Consequently, the results of geomechanical laboratory testings are presented in order to compare here the results of multistep triaxial compression tests, of hydraulic fracturing laboratory tests and of some other tests for rock characterization with the corresponding results of Opalinus clay sites in Switzerland that were investigated by the Swiss Nagra Company for host rock characterization. After a discussion of the relevant state of fresh Opalinus clay, especially of suction pressure conditions and saturation state, the results of triaxial shear tests are presented. Increasing shear deformation at increasing pressure and unchanged water saturation do not result in a significant strength reduction of the Opalinus clay. The rock shows increasing cohesion and stiffness, if multiple loading has repeatedly reached the failure point. Thus there is no increased permeability with continued shearing. Only at the beginning of the shearing process is a temporarily increased permeability to be expected due to dilatation processes. An increased

  7. Physico-chemical characterisation and sorption measurements of Cs, Sr, Ni, Eu, Th, Sn and Se on Opalinus clay from Mont Terri

    International Nuclear Information System (INIS)

    Lauber, Matthias; Baeyens, Bart; Bradbury, Michael H.

    2000-12-01

    Opalinus Clay is currently under investigation as a potential host rock for the disposal of high level and long-lived intermediate radioactive waste. A throughout physico-chemical characterisation was carried out on a bore core sample from the underground rock laboratory Mont Terri (Canton Jura). The results of these investigations indicate that the major characteristics (mineralogy, cation exchange capacity, cation occupancies, selectivity coefficients, chloride and sulphate inventories) were very similar to a different core sample, previously used for pore water modelling studies. It was concluded that the pore water compositions derived in the earlier studies were reliable and could be used in this work. The organic matter which dissolved from the Opalinus Clay rock was not humic or fulvic acids and the concentration remaining in the liquid phase in the sorption experiments was < 0.5 ppm C. The organic matter is therefore considered to have little or no influence on the sorption behaviour of the studied radionuclides. Redox potential measurements of the Opalinus Clay/synthetic pore water system inside the glove boxes indicated anoxic conditions. The main focus of the experimental work presented here is on the sorption behaviour of Cs (I), Sr (II), Ni (II), Eu (III), Th (IV), Sn (IV) and Se (IV) on Opalinus Clay equilibrated with synthetic pore waters at pH 6.3 and 8. Sorption isotherms were measured for Cs, Ni, Eu, Th and Se. Single point data were measured for Sr and Sn. For all radionuclides studied the sorption kinetics were measured first. The times required to complete the sorption on the Opalinus Clay varied between one day for Th and one month for Ni and Se. Within the concentration ranges under study the uptake of Cs, Ni, Eu and Se on Opalinus Clay was non-linear, whereas for Th a linear sorption behaviour was observed. For Ni, Eu and Th the sorption increased with increasing pH. For Cs a pH independent sorption behaviour was observed. The concentration

  8. Influence of carbonate micro-fabrics on the failure strength of Callovo-Oxfordian clay stones and Opalinus Clay

    International Nuclear Information System (INIS)

    Klinkenberg, M.; Dohrmann, R.; Kaufhold, S.; Siegesmund, S.

    2010-01-01

    Document available in extended abstract form only. The potential use of clay stones as host rock for radioactive waste disposal is currently investigated. For this application, hydraulic conductivity, swelling properties, water uptake, rheological and mechanical properties are of great importance. The Opalinus Clay (Mont-Terri, Switzerland) and the Callovo- Oxfordian clay stone (France) are the most frequently studied clay stones. One goal is to develop a numerical model being able to predict the mechanical behaviour of clay stones under repository-like conditions. Experimental investigations reveal that Opalinus Clay and Callovo-Oxfordian clay stone behave different with respect to the dependence of mechanical strength on the carbonate content. The failure strength of Opalinus Clay decreases with increasing carbonate content, whereas it increases with increasing carbonate content when Callovo-Oxfordian clay stone is considered. To supply proper data and enable reliable model assumptions, the use of suitable experimental techniques for the description of the microstructure is indispensable. After mechanical testing, samples were taken perpendicular to the bedding and polished sections were prepared. The micro-fabrics were investigated using scanning electron microscopy (SEM) and image analysis. Backscattered electron (BSE) images were used for the image analysis because carbonates can be extracted by grey level analysis. The image analysis of the extracted particles provides the following parameters: area, longest and shortest axis of an ellipse (surrounding the particle), perimeter, the angle to horizontal (longest axis), and the aspect ratio (longest axis/shortest axis). Callovo-Oxfordian clay stone shows a homogenous distribution of fine-grained carbonates and dovetail connection of calcium carbonate with the clayey matrix. In contrast Opalinus Clay shows large elongated carbonate grains (high aspect ratios) of shell fragments. Cracks are mostly related to these

  9. Water Retention Curves of Opalinus Clay

    International Nuclear Information System (INIS)

    Villar, M. V.; Romero, F. J.

    2012-01-01

    The water retention curve of Opalinus clay samples was determined under different conditions: total and matric suction, stress or no-stress conditions, wetting and drying paths. Through the fitting of these results to the van Genuchten expression the P parameter, related to the air entry value (AEV), was obtained. The AEV is the suction value above which air is able to enter the pores of the sample, and consequently, above which 2-phase flow can take place in the soil pore structure. The samples used in this research came from two different boreholes, BHT-1 and BHG-D1, but the behaviour of them did not depend on their location, what was probably due to the fact that both were drilled in the shay facies of the Opalinus clay. There was not a distinct difference between the results obtained under total or matric suctions. In the drying paths, both the water contents and the degrees of saturation tended to be higher when total suction was applied, however the reverse trend was observed for the water contents reached in wetting paths. As well, no clear difference was observed in the water retention curves obtained in odometers under matric and total suctions, what points to the osmotic component of suction in Opalinus clay not being significant. Overall, the water contents were lower and the degrees of saturation higher when suction was applied under vertical stress, what would indicate that the water retention capacity was lower under 8 MPa vertical stress than under free volume conditions. This vertical stress value is slightly higher than the maximum in situ stress. Also, the samples showed hysteresis according to the expected behaviour, i.e. the water contents for a given suction were higher during a drying path than during a wetting path. The P values obtained were between 6 and 34 MPa, and tended to be higher for the samples tested under stress, in drying paths and when total suction was used. The air entry value calculated from the mercury intrusion porosimetry

  10. Water Retention Curves of Opalinus Clay

    Energy Technology Data Exchange (ETDEWEB)

    Villar, M. V.; Romero, F. J.

    2012-11-01

    The water retention curve of Opalinus clay samples was determined under different conditions: total and matric suction, stress or no-stress conditions, wetting and drying paths. Through the fitting of these results to the van Genuchten expression the P parameter, related to the air entry value (AEV), was obtained. The AEV is the suction value above which air is able to enter the pores of the sample, and consequently, above which 2-phase flow can take place in the soil pore structure. The samples used in this research came from two different boreholes, BHT-1 and BHG-D1, but the behaviour of them did not depend on their location, what was probably due to the fact that both were drilled in the shay facies of the Opalinus clay. There was not a distinct difference between the results obtained under total or matric suctions. In the drying paths, both the water contents and the degrees of saturation tended to be higher when total suction was applied, however the reverse trend was observed for the water contents reached in wetting paths. As well, no clear difference was observed in the water retention curves obtained in odometers under matric and total suctions, what points to the osmotic component of suction in Opalinus clay not being significant. Overall, the water contents were lower and the degrees of saturation higher when suction was applied under vertical stress, what would indicate that the water retention capacity was lower under 8 MPa vertical stress than under free volume conditions. This vertical stress value is slightly higher than the maximum in situ stress. Also, the samples showed hysteresis according to the expected behaviour, i.e. the water contents for a given suction were higher during a drying path than during a wetting path. The P values obtained were between 6 and 34 MPa, and tended to be higher for the samples tested under stress, in drying paths and when total suction was used. The air entry value calculated from the mercury intrusion porosimetry

  11. Anisotropic Behaviour of Opalinus Clay Through Consolidated and Drained Triaxial Testing in Saturated Conditions

    Science.gov (United States)

    Favero, Valentina; Ferrari, Alessio; Laloui, Lyesse

    2018-05-01

    This paper investigates the anisotropic hydro-mechanical behaviour of Opalinus Clay shale, the host material currently being considered for the construction of a nuclear waste repository in Switzerland. Consolidated and drained triaxial tests on Opalinus Clay from the Mont Terri URL have been conducted in order to derive information on its strength and stiffness properties. Opalinus Clay specimens were tested both parallel to bedding (P-specimens) and perpendicular to bedding (S-specimens). The considered effective confining stress range (from 2 to 12 MPa) has been selected in order to reproduce possible in situ stress conditions for the repository. In this work, particular attention has been paid to the experimental procedure in order to ensure consolidated conditions and avoid generation of unwanted excess pore water pressure during drained shearing. The Skempton B parameter has been determined for all the tested specimens in order to ensure saturation. Both single-stage and multistage triaxial testing procedures were adopted in the experimental campaign. The results of the triaxial tests highlight an anisotropic elastic response of Opalinus Clay: S-specimens present a more compliant behaviour than P-specimens. The values of the Young modulus are found to increase with the increase in mean effective stress. The analysis of the peak and ultimate shear strength results reveals that the material behaves in a similar manner regardless of the considered direction of loading (P and S directions) with respect to the bedding orientation. Peak and ultimate failure envelopes for Opalinus Clay were derived for the investigated stress range.

  12. Far Field Sorption Data Bases for Performance Assessment of a High-Level Radioactive Waste Repository in an Undisturbed Opalinus Clay Host Rock

    International Nuclear Information System (INIS)

    Bradburry, M.; Baeyens, B.

    2003-08-01

    An Opalinus Clay formation in the Zuercher Weinland is under consideration by Nagra as a potential location for a high-level and long-Iived intermediate-level radioactive waste repository. Performance assessment studies will be performed for this site and the purpose of this report is to describe the procedures used to develop sorption data bases appropriate for an undisturbed Opalinus Clay host rock which are required for such safety analysis calculations. In tight, low water content argillaceous rock formations such as Opalinus Clay, there is uncertainty concerning the in situ pH/P CO 2 . In order to take this intrinsic uncertainty into account porewater chemistries were calculated for a reference case, pH = 7.24, and for two other pH values, 6.3 and 7.8. Sorption data bases are given for the three cases. The basis for the sorption data bases is 'in-house' sorption measurements for Cs(I), Sr(II), Ni(II), Eu(III), Sn(IV), Se(IV), Th(IV) and I(-I) carried out on Opalinus Clay samples from Mont Terri (Canton Jura) since at the time the experiments were performed no core samples from the Benken borehole (Zuercher Weinland) were available. The Opalinus Clay at Mont Terri and Benken are part of the same geological formation . Despite having directly measured data for the above key radionuclides, some of the required distribution ratios (Rd) used to generate the sorption data bases still came from the open literature. An important part of this report is concerned with describing the procedures whereby these selected literature Rd values were modified so as to apply to the Benken Opalinus Clay mineralogy and groundwater chemistries calculated at the three pH values given above. The resulting Rd values were then further modified using so-called Lab→Field transfer factors to produce sorption values which were appropriate to the in situ bulk rock for the selected range of water chemistry conditions. Finally, it is important to have some appreciation of the uncertainties

  13. Clay shale as host rock. A geomechanical contribution about Opalinus clay; Tonstein als Wirtsgestein. Ein geomechanischer Beitrag ueber Opalinuston

    Energy Technology Data Exchange (ETDEWEB)

    Lempp, Christof; Menezes, Flora; Sachwitz, Simon [Halle-Wittenberg Univ., Halle (Saale) (Germany). Inst. fuer Geowissenschaften und Geographie

    2016-12-15

    The Opalinuston is a prominent rock representing the type of organic clay shales or clay stones within the sequence of Triassic and Jurassic marine sediments in Southern Germany. The rock forms a homogenous unit some ten meters thick. The degree of consolidation of this type of pelitic rock depends mainly on the former load conditions, but is also dependent on the long-term weathering and even on the present exposition. The geomechanical parameters such as shear strength, tensional strength and permeability vary with the state of consolidation and become important when the use is discussed of such rocks for radioactive waste disposal. A tunneling project at the northern escarpment of the Swabian Alb (Southwest Germany) within the Opalinus clay offered the rare opportunity to obtain fresh unweathered rock samples in greater amounts compared to fresh drilling cores from which geomechanical investigations are usually undertaken. Consequently, the results of geomechanical laboratory testings are presented in order to compare here the results of multistep triaxial compression tests, of hydraulic fracturing laboratory tests and of some other tests for rock characterization with the corresponding results of Opalinus clay sites in Switzerland that were investigated by the Swiss Nagra Company for host rock characterization. After a discussion of the relevant state of fresh Opalinus clay, especially of suction pressure conditions and saturation state, the results of triaxial shear tests are presented. Increasing shear deformation at increasing pressure and unchanged water saturation do not result in a significant strength reduction of the Opalinus clay. The rock shows increasing cohesion and stiffness, if multiple loading has repeatedly reached the failure point. Thus there is no increased permeability with continued shearing. Only at the beginning of the shearing process is a temporarily increased permeability to be expected due to dilatation processes. An increased

  14. Anisotropic modelling of Opalinus Clay behaviour: From triaxial tests to gallery excavation application

    Directory of Open Access Journals (Sweden)

    François Bertrand

    2017-06-01

    Full Text Available Deep repository in geological formations is the preferential solution considered in many countries to manage high-level nuclear wastes. In Switzerland, the Opalinus Clay is a candidate host rock. In this context, in situ and laboratory tests are conducted on Opalinus Clay to demonstrate the feasibility of deep disposal in this argillaceous formation. This paper presents a constitutive model able to fit the experimental data obtained from some triaxial tests conducted by Jahns (2013 on cores from borehole Schlattingen SLA-1. The elasto-plastic behaviour of Opalinus Clay is reproduced thanks to a Drucker-Prager model, taking into account the anisotropy behaviour of this sedimentary rock. The objective is to employ a single set of parameters representative of the material. In a second version of the model, the stress-dependence of the elastic properties and damage are taken into account. Finally, the parameters calibrated with experimental tests are used to simulate the excavation of a gallery with a second gradient approach.

  15. Mineralogical and Micro-fabric investigation of the Sandy Facies of Opalinus Clay (Mont Terri)

    International Nuclear Information System (INIS)

    Kaufhold, Annette; Siegesmund, Siegfried; Dohrmann, Reiner; Graesle, Werner; Plischke, Ingo

    2013-01-01

    In the field of geological disposal of radioactive waste in many countries argillaceous formations are considered as potential host rock. For the understanding of the long-term behaviour of clay host rock, it is important to understand the interaction between mechanical behaviour, micro-fabric, and mineral composition. Previous publications showed that particularly the carbonate content and the arrangement of the carbonate grains (as cement in the matrix or as shells) determines the mechanical strength of Opalinus Clay and Callovo-Oxfordian Clay specimens, respectively. Klinkenberg et al. (2009) studied the shaly facies of Opalinus Clay, however, the actual deposit is planned to be built in the sandy facies of Opalinus Clay. The aim of the present study is to investigate the relation between micro-fabric, mineral composition, and mechanical properties of different samples derived from the sandy facies (BLT-A2). Image analysis showed that the carbonates in the sandy facies mainly occur as 1) matrix which in turn acts as cement. Carbonates also occur 2) in the fine sand fraction and 3) biogenic carbonates as traces. The carbonates of the sandy facies, therefore, appear to be similar to the carbonates of the Callovo-Oxfordian Clay with respect to their possible influence on failure strength. The mechanical testing showed that the shear strength increases with increasing carbonate content. This phenomenon was also observed for the samples of the Callovo-Oxfordian Clay, while the opposite relation was found for the shaly facies of the Opalinus Clay. Preliminary results presented here, indicate that the sandy facies (drilling BLT-A2) and Callovo-Oxfordian Clay show similar mechanical properties - in detail: 1) Micro-fabric: carbonates predominate in the matrix, 2) Mineralogy: high carbonate content and 3) Mechanical testing: shear strength increases with increasing carbonate content, where the type of carbonates which controls the increase of strength has to be

  16. Self-sealing Faults in the Opalinus Clay - Evidence from Field Observations, Hydraulic Testing and Pore water Chemistry

    International Nuclear Information System (INIS)

    Gautschi, Andreas

    2001-01-01

    As part of the Swiss programme for high-level radioactive-waste, the National Cooperative for the Disposal of Radioactive Waste (Nagra) is currently investigating the Jurassic (Aalenian) Opalinus Clay as a potential host formation (Nagra 1988, 1994). The Opalinus Clay consists of indurated dark grey micaceous Clay-stones (shales) that are subdivided into several litho-stratigraphic units. Some of them contain thin sandy lenses, limestone concretions or siderite nodules. The clay mineral content ranges from 40-80 weight per cent (9-29% illite, 3-10% chlorite, 6-20% kaolinite and 4-22% illite/smectite mixed layers in the ratio 70/30). Other minerals are quartz (15-30%), calcite (6-40%), siderite (2-3%), ankerite (0-3%), feldspars (1-7%), pyrite (1-3%) and organic carbon (<1%). The total water content ranges from 4-19% (Mazurek 1999, Nagra 2001). Faults are mainly represented by fault gouge and fault breccias, partly associated with minor veins of calcite. A key question in safety assessment is, whether these faults may represent preferential pathways for radionuclide transport. An extensive hydrogeological data base - part of which derives from strongly tectonized geological environments - suggests that advective transport through faults in the Opalinus Clay at depth > 200 m is insignificant. This conclusion is also supported by independent evidence from clay pore water hydrochemical and isotopic data. The lack of hydrochemical anomalies and the lack of extensive mineral veining suggest that there was also no significant paleo-flow through such faults. These observations can only be reconciled with a strong self-sealing capacity of the faults. Therefore it is concluded, that reactivated existing faults or newly induced fractures will not act as pathways for significant fluid flow at anytime due to self-healing processes. These conclusions are supported by results from laboratory hydro-frac and flow-through tests, and from field-tests in the Mont Terri underground

  17. Microbial diversity in opalinus clay and interaction of dominant microbial strains with actinides

    International Nuclear Information System (INIS)

    Moll, Henry; Luetke, Laura; Bachvarova, Velina; Steudtner, Robin; Geissler, Andrea; Krawczyk-Baersch, Evelyn; Selenska-Pobell, Sonja; Bernhardt, Gert

    2013-01-01

    For the first time microbial tDNA could be isolated from 50 g unperturbed Mont Terri Opalinus Clay. Based on the analysis of the tDNA the bacterial diversity of the unperturbed clay is dominated by representatives of Firmicutes, Betaproteobacteria, and Bacteriodetes. Firmicutes also dominate after treatment of the clay with R2A medium. Bacteria isolated from Mont Terri Opalinus Clay on R2A medium were related to Sporomusa spp., Paenibacillus spp., and Clostridium spp. All further investigations are concentrated on the unique isolates Sporomusa sp. MT-2 and Paenibacillus sp. MT-2. Cells of the type Sporomusa sp. MT-2 and Paenibacillus sp. MT-2 were comprehensively analyzed in terms of growing, morphology, functional groups of the cell envelope, and cell membrane structure. Strong actinide(An)/lanthanide(Ln)-interactions with the Opalinus Clay isolates and the Aespoe-strain Pseudomonas fluorescens (CCUG 32456) could be determined within a broad pH range (2-8). The metals bind as a function of pH on protonated phosphoryl, carboxyl and deprotonated phosphoryl sites of the respective cell membrane. The thermodynamic surface complexation constants of bacterial An/Ln-species were determined and can be used in modeling programs. Depending on the used An different interaction mechanisms were found (U(VI): biosorption, partly biomineralisation; Cm(III): biosorption, indications for embedded Cm(III); Pu: biosorption, bioreduction and indications for embedded Pu). Different strategies of coping with U(VI) were observed comparing P. fluorescens planktonic cells and biofilms under the chosen experimental conditions. An enhanced capability of the biofilm to form meta-autunite in comparison to the planktonic cells was proven. Conclusively, the P. fluorescens biofilm is more efficient in U(VI) detoxification. In conclusion, Mont Terri Opalinus Clay contains bacterial communities, that may influence the speciation and hence the migration behavior of selected An/Ln under

  18. Microbial diversity in opalinus clay and interaction of dominant microbial strains with actinides

    Energy Technology Data Exchange (ETDEWEB)

    Moll, Henry; Luetke, Laura; Bachvarova, Velina; Steudtner, Robin; Geissler, Andrea; Krawczyk-Baersch, Evelyn; Selenska-Pobell, Sonja; Bernhardt, Gert

    2013-07-01

    For the first time microbial tDNA could be isolated from 50 g unperturbed Mont Terri Opalinus Clay. Based on the analysis of the tDNA the bacterial diversity of the unperturbed clay is dominated by representatives of Firmicutes, Betaproteobacteria, and Bacteriodetes. Firmicutes also dominate after treatment of the clay with R2A medium. Bacteria isolated from Mont Terri Opalinus Clay on R2A medium were related to Sporomusa spp., Paenibacillus spp., and Clostridium spp. All further investigations are concentrated on the unique isolates Sporomusa sp. MT-2 and Paenibacillus sp. MT-2. Cells of the type Sporomusa sp. MT-2 and Paenibacillus sp. MT-2 were comprehensively analyzed in terms of growing, morphology, functional groups of the cell envelope, and cell membrane structure. Strong actinide(An)/lanthanide(Ln)-interactions with the Opalinus Clay isolates and the Aespoe-strain Pseudomonas fluorescens (CCUG 32456) could be determined within a broad pH range (2-8). The metals bind as a function of pH on protonated phosphoryl, carboxyl and deprotonated phosphoryl sites of the respective cell membrane. The thermodynamic surface complexation constants of bacterial An/Ln-species were determined and can be used in modeling programs. Depending on the used An different interaction mechanisms were found (U(VI): biosorption, partly biomineralisation; Cm(III): biosorption, indications for embedded Cm(III); Pu: biosorption, bioreduction and indications for embedded Pu). Different strategies of coping with U(VI) were observed comparing P. fluorescens planktonic cells and biofilms under the chosen experimental conditions. An enhanced capability of the biofilm to form meta-autunite in comparison to the planktonic cells was proven. Conclusively, the P. fluorescens biofilm is more efficient in U(VI) detoxification. In conclusion, Mont Terri Opalinus Clay contains bacterial communities, that may influence the speciation and hence the migration behavior of selected An/Ln under

  19. In situ analysis of microbial reduction of a nitrate plume in Opalinus clay

    International Nuclear Information System (INIS)

    Bleyen, N.; Smets, S.; Valcke, E.; Albrecht, A.; De Canniere, P.; Schwyn, B.; Wittebroodt, C.

    2012-01-01

    Document available in extended abstract form only. In several countries, such as Belgium, France and Switzerland, clay formations are foreseen as the host rock for geological disposal of bituminized low-level and intermediate-level long-lived radioactive waste. Suitable clay formations exhibit favorable hydro-mechanical and geochemical characteristics, which are expected to retard the migration of leached radionuclides. Along with radionuclides, certain classes of bituminized radioactive waste may also contain high concentrations of NaNO 3 , dispersed into the hydrophobic bitumen matrix used to stabilize the waste. During and after saturation of the disposal gallery, this bituminized waste will start to take up water due to osmosis, resulting in the leaching of significant amounts of NaNO 3 and soluble organic bitumen degradation products (BDP) into the clay pore water. This nitrate plume could cause several geochemical and biochemical processes in the clay surrounding the waste disposal gallery, potentially affecting the barrier function of the host rock. To study these processes, an in situ experiment in the Opalinus Clay, named the Bitumen-Nitrate-Clay interaction (BN) experiment, is being performed at the Mont Terri Rock Laboratory (CH). The experiment consists of a vertical borehole rigged with a downhole equipment containing three packed-off intervals, each lined with a cylindrical sintered stainless steel filter screen to allow contact with the surrounding clay. Prior to the start of the tests, the intervals were injected with an artificial Opalinus Clay pore water, containing all major ions at pore water concentrations at Mont Terri, but no organic matter, and were equilibrated with the surrounding clay for ∼8 months. To ensure a continuous water flow during the tests, each interval is connected to a stainless steel water circulation unit, equipped with water sampling containers, circulation pumps and flow meters. In addition, to continuously monitor the

  20. Far Field Sorption Data Bases for Performance Assessment of a High-Level Radioactive Waste Repository in an Undisturbed Opalinus Clay Host Rock

    Energy Technology Data Exchange (ETDEWEB)

    Bradburry, M.; Baeyens, B

    2003-08-01

    An Opalinus Clay formation in the Zuercher Weinland is under consideration by Nagra as a potential location for a high-level and long-Iived intermediate-level radioactive waste repository. Performance assessment studies will be performed for this site and the purpose of this report is to describe the procedures used to develop sorption data bases appropriate for an undisturbed Opalinus Clay host rock which are required for such safety analysis calculations. In tight, low water content argillaceous rock formations such as Opalinus Clay, there is uncertainty concerning the in situ pH/P{sub CO{sub 2}}. In order to take this intrinsic uncertainty into account porewater chemistries were calculated for a reference case, pH = 7.24, and for two other pH values, 6.3 and 7.8. Sorption data bases are given for the three cases. The basis for the sorption data bases is 'in-house' sorption measurements for Cs(I), Sr(II), Ni(II), Eu(III), Sn(IV), Se(IV), Th(IV) and I(-I) carried out on Opalinus Clay samples from Mont Terri (Canton Jura) since at the time the experiments were performed no core samples from the Benken borehole (Zuercher Weinland) were available. The Opalinus Clay at Mont Terri and Benken are part of the same geological formation . Despite having directly measured data for the above key radionuclides, some of the required distribution ratios (Rd) used to generate the sorption data bases still came from the open literature. An important part of this report is concerned with describing the procedures whereby these selected literature Rd values were modified so as to apply to the Benken Opalinus Clay mineralogy and groundwater chemistries calculated at the three pH values given above. The resulting Rd values were then further modified using so-called Lab{yields}Field transfer factors to produce sorption values which were appropriate to the in situ bulk rock for the selected range of water chemistry conditions. Finally, it is important to have some

  1. Hydro-mechanical aspects: glacial loading/erosion - the opalinus clay study

    International Nuclear Information System (INIS)

    Marschall, P.; Kupfer, T.; Kuhlmann, U.

    2004-01-01

    In Nagra's high level waste programme the future geological evolution of the investigation area in the Zurcher Weinland (NE Switzerland) is considered over a time period of around 1 Ma. Uplift, erosion and climatic changes were identified as processes that may affect the long-term performance of a repository for spent fuel (SF), vitrified high-level waste (HLW) and long-lived intermediate-level waste (ILW). The possible impact of those long-term processes on the barrier function of the host rock formation (Opalinus Clay) comprises: (i) the change of the vertical hydraulic gradient caused by changing recharge/discharge conditions in the regional aquifer systems; (ii) permeability enhancement of the host rock formation due to the uplift process; and (iii) expulsion of contaminated pore water from the disposal area as a result of repeated glacial loading. Due to the fact that the discharge level of the regional aquifer systems is defined by the Rhine valley and the regional recharge areas are characterised by moderate elevations (typically 2 are not expected within the next several million years. Hence, the topography of NE Switzerland together with the favourable hydraulic properties of the host rock formation prevent efficiently the vertical exchange of groundwater between the regional aquifer systems. Even on geological time scales of millions of years the expected vertical pore water flow through the host rock formation is in the order of 10 -14 m/s and lower. At present, the Opalinus Clay forms a perfect hydraulic barrier. The process of ongoing uplift, however, may give rise to embrittlement of the rock, entailed by permeability enhancement. Evidence for permeability enhancement of Opalinus Clay in shallow depth was observed by Hekel (1994). On the other hand, regional studies confirmed the low permeability of the Opalinus Clay formation in greater depth even when fractured (Gautschi, 2001; Marschall et al., 2003). Such evidence, together with conceptual

  2. The Mont Terri rock laboratory: International research in the Opalinus Clay

    International Nuclear Information System (INIS)

    Bossart, P.

    2015-01-01

    This article reports on a visit made to the rock laboratory in Mont Terri, Switzerland, where research is being done concerning rock materials that can possibly be used for the implementation of repositories for nuclear wastes. Emphasis is placed on the project’s organisation, rock geology and on-going experiments. International organisations also involved in research on nuclear waste repositories are listed. The research facilities in tunnels built in Opalinus Clay at the Mont Terri site are described. The geology of Opalinus Clay and the structures found in the research tunnels are discussed, as is the hydro-geological setting. The research programme and various institutions involved are listed and experiments carried out are noted. The facilities are now also being used for research on topics related to carbon sequestration

  3. Comparative study of methods to estimate hydraulic parameters in the hydraulically undisturbed Opalinus Clay (Switzerland)

    Energy Technology Data Exchange (ETDEWEB)

    Yu, C.; Matray, J.-M. [Institut de Radioprotection et de Sûreté Nucléaire, Fontenay-aux-Roses, (France); Yu, C.; Gonçalvès, J. [Aix Marseille Université UMR 6635 CEREGE Technopôle Environnement Arbois-Méditerranée Aix-en-Provence, Cedex 4 (France); and others

    2017-04-15

    The deep borehole (DB) experiment gave the opportunity to acquire hydraulic parameters in a hydraulically undisturbed zone of the Opalinus Clay at the Mont Terri rock laboratory (Switzerland). Three methods were used to estimate hydraulic conductivity and specific storage values of the Opalinus Clay formation and its bounding formations through the 248 m deep borehole BDB-1: application of a Poiseuille-type law involving petrophysical measurements, spectral analysis of pressure time series and in situ hydraulic tests. The hydraulic conductivity range in the Opalinus Clay given by the first method is 2 × 10{sup -14}-6 × 10{sup -13} m s{sup -1} for a cementation factor ranging between 2 and 3. These results show low vertical variability whereas in situ hydraulic tests suggest higher values up to 7 × 10{sup -12} m s{sup -1}. Core analysis provides economical estimates of the homogeneous matrix hydraulic properties but do not account for heterogeneities at larger scale such as potential tectonic conductive features. Specific storage values obtained by spectral analysis are consistent and in the order of 10{sup -6} m{sup -1}, while formulations using phase shift and gain between pore pressure signals were found to be inappropriate to evaluate hydraulic conductivity in the Opalinus Clay. The values obtained are globally in good agreement with the ones obtained previously at the rock laboratory. (authors)

  4. Hydrochemical characterisation of the opalinus clay in the test interval of the BDI-B1 borehole and on site pH, Eh, Fe(II) and alkalinity measurements

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, A.M.; Turrero, M.J.; Yllera, A.; Melon, A.M.; Sanchez, M.D.; Pena, J.; Garralon, A.; Rivas, P. [Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT), Dpt. of Energy Environmental Impact, Madrid (Spain); Hernan, P. [ENRESA, Madrid (Spain)

    2005-07-01

    Clay formations are considered as a feasible option for the disposal of high-level radioactive wastes. In order to determine their suitability for this purpose, the evaluation of the hydro-geochemistry and transport mechanisms must be undertaken. In this sense, a general understanding of the basic physical and chemical processes that govern the solute transport together with a detailed site-characterization programme is required. To reach this goal, a number of activities have been developed in the Opalinus Clay formation at the Mont Terri Underground Research Laboratory (URL) at Switzerland. In the context of some experiments (WS-C, WS-D, WS-E, GM Task, DI, etc.), the Opalinus Clay formation has been comprehensively characterized to develop a conceptual, thermodynamic and transport model of solutes. The framework of these works is the need to know the mechanism of the possible migration of radionuclides and the pore water chemistry, as essential data for the performance assessment of such argillaceous systems. (authors)

  5. Diffusion Experiments with Opalinus and Callovo-Oxfordian Clays: Laboratory, Large-Scale Experiments and Microscale Analysis by RBS

    International Nuclear Information System (INIS)

    Garcia-Gutierrez, M.; Alonso, U.; Missana, T.; Cormenzana, J.L.; Mingarro, M.; Morejon, J.; Gil, P.

    2009-01-01

    Consolidated clays are potential host rocks for deep geological repositories for high-level radioactive waste. Diffusion is the main transport process for radionuclides (RN) in these clays. Radionuclide (RN) diffusion coefficients are the most important parameters for Performance Assessment (PA) calculations of clay barriers. Different diffusion methodologies were applied at a laboratory scale to analyse the diffusion behaviour of a wide range of RN. Main aims were to understand the transport properties of different RNs in two different clays and to contribute with feasible methodologies to improve in-situ diffusion experiments, using samples of larger scale. Classical laboratory essays and a novel experimental set-up for large-scale diffusion experiments were performed, together to a novel application of the nuclear ion beam technique Rutherford Backscattering Spectrometry (RBS), for diffusion analyses at the micrometer scale. The main experimental and theoretical characteristics of the different methodologies, and their advantages and limitations are here discussed. Experiments were performed with the Opalinus and the Callovo-Oxfordian clays. Both clays are studied as potential host rock for a repository. Effective diffusion coefficients ranged between 1.10 - 10 to 1.10 - 12 m 2 /s for neutral, low sorbing cations (as Na and Sr) and anions. Apparent diffusion coefficients for strongly sorbing elements, as Cs and Co, are in the order of 1.10-13 m 2 /s; europium present the lowest diffusion coefficient (5.10 - 15 m 2 /s). The results obtained by the different approaches gave a comprehensive database of diffusion coefficients for RN with different transport behaviour within both clays. (Author) 42 refs

  6. Diffusion Experiments with Opalinus and Callovo-Oxfordian Clays: Laboratory, Large-Scale Experiments and Microscale Analysis by RBS

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Gutierrez, M.; Alonso, U.; Missana, T.; Cormenzana, J.L.; Mingarro, M.; Morejon, J.; Gil, P.

    2009-09-25

    Consolidated clays are potential host rocks for deep geological repositories for high-level radioactive waste. Diffusion is the main transport process for radionuclides (RN) in these clays. Radionuclide (RN) diffusion coefficients are the most important parameters for Performance Assessment (PA) calculations of clay barriers. Different diffusion methodologies were applied at a laboratory scale to analyse the diffusion behaviour of a wide range of RN. Main aims were to understand the transport properties of different RNs in two different clays and to contribute with feasible methodologies to improve in-situ diffusion experiments, using samples of larger scale. Classical laboratory essays and a novel experimental set-up for large-scale diffusion experiments were performed, together to a novel application of the nuclear ion beam technique Rutherford Backscattering Spectrometry (RBS), for diffusion analyses at the micrometer scale. The main experimental and theoretical characteristics of the different methodologies, and their advantages and limitations are here discussed. Experiments were performed with the Opalinus and the Callovo-Oxfordian clays. Both clays are studied as potential host rock for a repository. Effective diffusion coefficients ranged between 1.10{sup -}10 to 1.10{sup -}12 m{sup 2}/s for neutral, low sorbing cations (as Na and Sr) and anions. Apparent diffusion coefficients for strongly sorbing elements, as Cs and Co, are in the order of 1.10-13 m{sup 2}/s; europium present the lowest diffusion coefficient (5.10{sup -}15 m{sup 2}/s). The results obtained by the different approaches gave a comprehensive database of diffusion coefficients for RN with different transport behaviour within both clays. (Author) 42 refs.

  7. Investigations for the influence of geochemical parameters on the sorption and desorption of lanthanides and uranium onto opalinus clay as potential host rock for a repository

    International Nuclear Information System (INIS)

    Moeser, Christina

    2010-01-01

    The development of a disposal in deep geological formations for radioactive waste is a very important task for the future. The safety assessment for more than a hundred thousand years needs a full understanding of all processes of interaction between the radioactive waste and the surrounded formations. This work contributes to this understanding. The interaction between lanthanides (homologues of the actinides americium, curium and berkelium) / uranium and the host rock opalinus clay under influence of organic substances (NOM) have been analyzed and discussed. The complex system was split into 3 binary basic systems with the following interactions - Interactions between lanthanides / uranium and NOM - Interactions between lanthanides / uranium and the opalinus clay - Interactions between NOM and opalinus clay All binary systems can be influenced by geological parameters like pH, ion strength and competing cations. The sorption / desorption of the lanthanides onto the opalinus clay is analyzed via inductively coupled plasma mass spectrometry. For the investigation of the complexation behavior of metals with NOM we used capillary electrophoresis coupled with inductively coupled plasma mass spectrometry. Under these conditions the chosen model organic humic acid affected the sorption of the lanthanides onto opalinus clay favorably. The smaller organic compounds, which dominate in the composition of the clay organics, remobilized the metals after sorption onto clay and the sorption can be inhibited by NOM. Due to the reduced metal sorption onto Opalinus clay by NOM, a migration through the clay may be possible.

  8. Ventilation test at Mont Terri. Geoelectric monitoring of the opalinus clay desaturation. Phase 2

    International Nuclear Information System (INIS)

    Wieczorek, Klaus; Zhang, Chun-Liang; Rothfuchs, Tilmann

    2008-04-01

    Between December 2001 and May 2004, a ventilation experiment (VE) was performed in the Mont Terri Underground Research Laboratory (URL) and co-financed by the Commission of the European Communities. The objective was to investigate the desaturation of consolidated clay formations in consequence of the ventilation of underground openings of a repository in such a formation. The results of the geoelectric measurements performed in the second phase of the Mont Terri ventilation test can be summarized as follows: Geoelectric tomography has been found suitable for monitoring ventilation-induced saturation changes in the Opalinus clay. During ventilation with dry air a desaturation down to below 50% could be detected in both desaturation cycles. The desaturated zone extends less than 0.5 m into the rock around the microtunnel. During the second resaturation phase, ventilation with humid air led to quick resaturation at the tunnel surface, while resaturation of the rock mass took months. The still ongoing third resaturation phase seems to imply that resaturation of the rock mass may take years with no air circulation in the tunnel. The laboratory investigations on the Opalinus clay included the determination of water retention capacity, swelling pressure, free swelling/shrinking strains induced by moisture changes, and response of normal and large hollow clay samples to the ventilation of the central boreholes at different air humidity values. The Opalinus clay has a high water absorption capacity. The amount of water uptake in unconstraint conditions is much higher than the water content in the naturally confined state, indicating that the pore water in the natural clay rock is predominantly bound on clay minerals. The swelling pressure induced by wetting with vapour is very close to the major lithostatic stress at the sampling location. Water uptake from vapour causes a large free expansion of up to 12% over 8 months and even a breakdown along bedding planes. Release of

  9. Project Opalinus clay Zuercher Weinland of Nagra. Evaluation of the geo-scientific data base and of the construction engineering aspects

    International Nuclear Information System (INIS)

    2005-02-01

    In this report the Commission for Nuclear Waste Management (KNE) assesses the geological and engineering aspects of the project Opalinus Clay, in which Nagra demonstrates the postclosure safety of geological disposal of spent fuel (SF), vitrified high-level wastes (HLW) and intermediate-level wastes (ILW) in a repository in the Opalinus Clay of the Zuercher Weinland in northern Switzerland. After in-depth examination of the geological database, KNE concludes that the demonstration of a suitable geological site for final disposal of SF, HLW and ILW in the Opalinus Clay of the Zuercher Weinland has been achieved. The geological assumptions Nagra uses for the assessment of long-term safety are based on data that have been carefully collected and interpreted. KNE acknowledges that Nagra interpreted the geological data correctly and adequately using state-of-the-art techniques. In case of lacking information, Nagra has used conservative or worst-case assumptions. The information documented by Nagra represents a good synthesis of field, laboratory and literature data. The tectonic situation of the Zuercher Weinland was examined in great details by Nagra. In the centre of the investigated region, where the Opalinus Clay occurs at 600 to 750 meters depth, the 3D-seismic data confirm its undisturbed stratification in an area of about 15 km 2 . Analysis and interpretation of the available information on the geological evolution provides no indication that erosion would expose the confining units above the Opalinus Clay within the next million years. The Opalinus Clay in the Zuercher Weinland is quite homogeneous and about 110 m thick. The properties of this rock are examined and found to be favourable for a repository. The dominance of the fine grain size and the high clay content indicate a very low hydraulic conductivity suitable for the isolation of radioactive wastes. Pore water extracted from drill-core samples is saline and has remained trapped for millions of years

  10. Litho- and biostratigraphy of the Opalinus Clay and bounding formations in the Mont Terri rock laboratory (Switzerland)

    International Nuclear Information System (INIS)

    Hostettler, B.; Reisdorf, A. G.; Jaeggi, D.

    2017-01-01

    A 250 m-deep inclined well, the Mont Terri BDB-1, was drilled through the Jurassic Opalinus Clay and its bounding formations at the Mont Terri rock laboratory (NW Switzerland). For the first time, a continuous section from (oldest to youngest) the topmost members of the Staffelegg Formation to the basal layers of the Hauptrogenstein Formation is now available in the Mont Terri area. We extensively studied the drill core for lithostratigraphy and biostratigraphy, drawing upon three sections from the Mont Terri area. The macropaleontological, micropaleontological, and palynostratigraphical data are complementary, not only spatially but they also cover almost all biozones from the Late Toarcian to the Early Bajocian. We ran a suite of geophysical logs to determine formational and intraformational boundaries based on clay content in the BDB-1 well. In the framework of an interdisciplinary study, analysis of the above-mentioned formations permitted us to process and derive new and substantial data for the Mont Terri area in a straightforward way. Some parts of the lithologic inventory, stratigraphic architecture, thickness variations, and biostratigraphic classification of the studied formations deviate considerably from occurrences in northern Switzerland that crop out further to the east. For instance, with the exception of the Sissach Member, no further lithostratigraphic subdivision in members is proposed for the Passwang Formation. Also noteworthy is that the ca. 130 m-thick Opalinus Clay in the BDB-1 core is 20 m thinner than that equivalent section found in the Mont Terri tunnel. The lowermost 38 m of the Opalinus Clay can be attributed chronostratigraphically solely to the Aalensis Zone (Late Toarcian). Deposition of the Opalinus Clay began at the same time farther east in northern Switzerland (Aalensis Subzone, Aalensis Zone), but in the Mont Terri area the sedimentation rate was two or three orders of magnitude higher. (authors)

  11. Litho- and biostratigraphy of the Opalinus Clay and bounding formations in the Mont Terri rock laboratory (Switzerland)

    Energy Technology Data Exchange (ETDEWEB)

    Hostettler, B. [Naturhistorisches Museum der Burgergemeinde Berne, Berne (Switzerland); Reisdorf, A. G. [Geologisch-Paläontologisches InstitutUniversität Basle, Basle (Switzerland); Jaeggi, D. [Swisstopo, Federal Office of Topography, Wabern (Switzerland); and others

    2017-04-15

    A 250 m-deep inclined well, the Mont Terri BDB-1, was drilled through the Jurassic Opalinus Clay and its bounding formations at the Mont Terri rock laboratory (NW Switzerland). For the first time, a continuous section from (oldest to youngest) the topmost members of the Staffelegg Formation to the basal layers of the Hauptrogenstein Formation is now available in the Mont Terri area. We extensively studied the drill core for lithostratigraphy and biostratigraphy, drawing upon three sections from the Mont Terri area. The macropaleontological, micropaleontological, and palynostratigraphical data are complementary, not only spatially but they also cover almost all biozones from the Late Toarcian to the Early Bajocian. We ran a suite of geophysical logs to determine formational and intraformational boundaries based on clay content in the BDB-1 well. In the framework of an interdisciplinary study, analysis of the above-mentioned formations permitted us to process and derive new and substantial data for the Mont Terri area in a straightforward way. Some parts of the lithologic inventory, stratigraphic architecture, thickness variations, and biostratigraphic classification of the studied formations deviate considerably from occurrences in northern Switzerland that crop out further to the east. For instance, with the exception of the Sissach Member, no further lithostratigraphic subdivision in members is proposed for the Passwang Formation. Also noteworthy is that the ca. 130 m-thick Opalinus Clay in the BDB-1 core is 20 m thinner than that equivalent section found in the Mont Terri tunnel. The lowermost 38 m of the Opalinus Clay can be attributed chronostratigraphically solely to the Aalensis Zone (Late Toarcian). Deposition of the Opalinus Clay began at the same time farther east in northern Switzerland (Aalensis Subzone, Aalensis Zone), but in the Mont Terri area the sedimentation rate was two or three orders of magnitude higher. (authors)

  12. Investigation of two-phase flow phenomena associated with corrosion in an SF/HLW repository in Opalinus Clay, Switzerland

    International Nuclear Information System (INIS)

    Senger, R.; Marschall, P.; Finsterle, S.

    2008-01-01

    Gas generation from corrosion of the waste canisters and gas accumulation in the backfilled emplacement tunnels is a key issue in the assessment of long-term radiological safety of the proposed repository for spent fuel and high-level waste (SF/HLW) sited in the Opalinus Clay formation of Northern Switzerland. Previous modeling studies indicated a significant pressure buildup in the backfilled emplacement tunnels for those sensitivity runs, where corrosion rates were high and the permeability of the Opalinus Clay was very low. As an extension to those studies, a refined process model of the canister corrosion phenomena has been developed, which accounts not only for the gas generation but also for the water consumption associated with the chemical reaction of corrosion of steel under anaerobic conditions. The simulations with the new process model indicate, that with increasing corrosion rates and decreasing host-rock permeability, pressure buildup increased, as expected. However, the simulations taking into account water consumption show that the pressure buildup is reduced compared to the simulation considering only gas generation. The pressure reduction is enhanced for lower permeability of the Opalinus Clay and for higher corrosion rates, which correspond to higher gas generations rates and higher water consumption rates. Moreover, the simulated two-phase flow patterns in the engineered barrier system (EBS) and surrounding Opalinus Clay show important differences at late time of the gas production phase as the generated gas continues to migrate outward into the surrounding host rock. For the case without water consumption, the water flow indicates overall downward flow due to a change in the overall density of the gas-fluid mixture from that based on the initially prescribed hydrostatic pressure gradient. For the case with water consumption, water flow converges toward the waste canister at a rate corresponding to the water consumption rate associated with the

  13. Geochemical signature of paleofluids in microstructures from Main Fault in the Opalinus Clay of the Mont Terri rock laboratory, Switzerland

    Energy Technology Data Exchange (ETDEWEB)

    Clauer, N. [Laboratoire d’Hydrologie et de Géochimie de Strasbourg (CNRS-UdS), Strasbourg (France); Techer, I. [Equipe Associée, Chrome, Université de Nîmes, Nîmes (France); Nussbaum, Ch. [Swiss Geological Survey, Federal Office of Topography Swisstopo, Wabern (Switzerland); Laurich, B. [Structural Geology, Tectonics and Geomechanics, RWTH Aachen University, Aachen (Germany); Laurich, B. [Federal Institute for Geosciences and Natural Resources BGR, Hannover (Germany)

    2017-04-15

    The present study reports on elemental and Sr isotopic analyses of calcite and associated celestite infillings of various microtectonic features collected mostly in the Main Fault of the Opalinus Clay from Mont Terri rock laboratory. Based on a detailed microstructural description of veins, slickensides, scaly clay aggregates and gouges, the geochemical signatures of the infillings were compared to those of the leachates from undeformed Opalinus Clay, and to the calcite from veins crosscutting Hauptrogenstein, Passwang and Staffelegg Formations above and below the Opalinus Clay. Vein calcite and celestite from Main Fault yield identical {sup 87}Sr/{sup 86}Sr ratios that are also close to those recorded in the Opalinus Clay matrix inside the Main Fault, but different from those of the diffuse Opalinus Clay calcite outside the fault. These varied {sup 87}Sr/{sup 86}Sr ratios of the diffuse calcite evidence a lack of interaction among the associated connate waters and the flowing fluids characterized by a homogeneous Sr signature. The {sup 87}Sr/{sup 86}Sr homogeneity at 0.70774 ± 0.00001 (2σ) for the infillings of most microstructures in the Main Fault, as well as of veins from nearby limestone layer and sediments around the Opalinus Clay, claims for an 'infinite' homogeneous marine supply, whereas the gouge infillings apparently interacted with a fluid chemically more complex. According to the known regional paleogeographic evolution, two seawater supplies were inferred and documented in the Delémont Basin: either during the Priabonian (38-34 Ma ago) from western Bresse graben, and/or during the Rupelian (34-28 Ma ago) from northern Rhine Graben. The Rupelian seawater that yields a mean {sup 87}Sr/{sup 86}Sr signature significantly higher than those of the microstructural infillings seems not to be the appropriate source. Alternatively, Priabonian seawater yields a mean {sup 87}Sr/{sup 86}Sr ratio precisely matching that of the leachates from diffuse

  14. Biogeochemical processes in a clay formation in situ experiment: Part E - Equilibrium controls on chemistry of pore water from the Opalinus Clay, Mont Terri Underground Research Laboratory, Switzerland

    Energy Technology Data Exchange (ETDEWEB)

    Pearson, F.J., E-mail: fjpearson@gmail.com [Ground-Water Geochemistry, 5108 Trent Woods Dr., New Bern, NC 28562 (United States); Tournassat, Christophe; Gaucher, Eric C. [BRGM, B.P. 36009, 45060 Orleans Cedex 2 (France)

    2011-06-15

    Highlights: > Equilibrium models of water-rock reactions in clay rocks are reviewed. > Analyses of pore waters of the Opalinus Clay from boreholes in the Mont Terri URL, Switzerland, are tabulated. > Results of modelling with various mineral controls are compared with the analyses. > Best agreement results with calcite, dolomite and siderite or daphnite saturation, Na-K-Ca-Mg exchange and/or kaolinite, illite, quartz and celestite saturation. > This approach allows calculation of the chemistry of pore water in clays too impermeable to yield water samples. - Abstract: The chemistry of pore water (particularly pH and ionic strength) is an important property of clay rocks being considered as host rocks for long-term storage of radioactive waste. Pore waters in clay-rich rocks generally cannot be sampled directly. Instead, their chemistry must be found using laboratory-measured properties of core samples and geochemical modelling. Many such measurements have been made on samples from the Opalinus Clay from the Mont Terri Underground Research Laboratory (URL). Several boreholes in that URL yielded water samples against which pore water models have been calibrated. Following a first synthesis report published in 2003, this paper presents the evolution of the modelling approaches developed within Mont Terri URL scientific programs through the last decade (1997-2009). Models are compared to the composition of waters sampled during dedicated borehole experiments. Reanalysis of the models, parameters and database enabled the principal shortcomings of the previous modelling efforts to be overcome. The inability to model the K concentrations correctly with the measured cation exchange properties was found to be due to the use of an inappropriate selectivity coefficient for Na-K exchange; the inability to reproduce the measured carbonate chemistry and pH of the pore waters using mineral-water reactions alone was corrected by considering clay mineral equilibria. Re

  15. Microbiological analysis of the in situ bitumen-nitrate-Opalinus clay interaction

    International Nuclear Information System (INIS)

    Moors, Hugo; Boven, Patrick; Leys, Natalie; Geissler, Andrea; Selenska-Pobell, Sonja

    2012-01-01

    Document available in extended abstract form only. Clay formations like the Opalinus Clay are foreseen to serve as the host rock for geological disposal of high and intermediate-level long-lived radioactive waste in several countries, because of their favourable properties to delay the migration of radionuclides over time. However, bituminized intermediate-level long-lived radioactive waste may physico-chemically perturb the clay barrier properties because in time it will leach substantial amounts of nitrate and organic bitumen degradation products (BDP). To study the physico-chemical impact of intermediate-level radioactive waste containing bitumen and nitrate, an in situ experiment in the Opalinus Clay (Saint Ursanne, Switzerland) named the Bitumen-Nitrate- Clay interaction (BN) experiment, is being performed at the Mont Terri Rock Laboratory. The in situ equipment of the BN-experiment consists of three separate packed-off intervals, supplied with a filter screen. Each interval is equipped with its own stainless steel water circulation unit. Such water circulation unit contains water sampling containers, circulation pumps and flow meters. One of the circulation units is equipped with an on-line UV spectrophotometer and pH electrode intervals, allowing a continuous monitoring of nitrate, nitrite concentrations, organic carbon level and pH. In a first series of tests, the microbial and biogeochemical effect of a nitrate and/or acetate perturbation is studied. Acetate is used as it a good representation of BDP. Hereto, nitrate was injected in interval 1 while a mixture of nitrate and acetate is injected in interval 2. As an active microbial community can have a significant impact on the physical and (geo)chemical conditions of the clay surrounding the disposal gallery, microbial analyses were performed on samples taken from the interval solutions before, during and after this first series of tests. Our microbial investigations which included Scanning Electron

  16. Microbiological analysis of the in situ bitumen-nitrate-Opalinus clay interaction

    Energy Technology Data Exchange (ETDEWEB)

    Moors, Hugo; Boven, Patrick; Leys, Natalie [SCK.CEN, Institute for Environment, Health and Safety, Laboratory for Molecular and Cellular Biology, Boeretang 200, B-2400 MOL (Belgium); Geissler, Andrea; Selenska-Pobell, Sonja [Helmholtz Zentrum Dresden Rossendorf, Institute of Radiochemistry, Biogeochemistry, Bautzner Landstr. 400, D-01328 Dresden (Germany)

    2012-10-15

    Document available in extended abstract form only. Clay formations like the Opalinus Clay are foreseen to serve as the host rock for geological disposal of high and intermediate-level long-lived radioactive waste in several countries, because of their favourable properties to delay the migration of radionuclides over time. However, bituminized intermediate-level long-lived radioactive waste may physico-chemically perturb the clay barrier properties because in time it will leach substantial amounts of nitrate and organic bitumen degradation products (BDP). To study the physico-chemical impact of intermediate-level radioactive waste containing bitumen and nitrate, an in situ experiment in the Opalinus Clay (Saint Ursanne, Switzerland) named the Bitumen-Nitrate- Clay interaction (BN) experiment, is being performed at the Mont Terri Rock Laboratory. The in situ equipment of the BN-experiment consists of three separate packed-off intervals, supplied with a filter screen. Each interval is equipped with its own stainless steel water circulation unit. Such water circulation unit contains water sampling containers, circulation pumps and flow meters. One of the circulation units is equipped with an on-line UV spectrophotometer and pH electrode intervals, allowing a continuous monitoring of nitrate, nitrite concentrations, organic carbon level and pH. In a first series of tests, the microbial and biogeochemical effect of a nitrate and/or acetate perturbation is studied. Acetate is used as it a good representation of BDP. Hereto, nitrate was injected in interval 1 while a mixture of nitrate and acetate is injected in interval 2. As an active microbial community can have a significant impact on the physical and (geo)chemical conditions of the clay surrounding the disposal gallery, microbial analyses were performed on samples taken from the interval solutions before, during and after this first series of tests. Our microbial investigations which included Scanning Electron

  17. Strengthening and stress relaxation of Opalinus Clay

    International Nuclear Information System (INIS)

    Schulze, Otto

    2010-01-01

    Document available in extended abstract form only. Full text follows: In the framework of the EU-project NF-PRO (e.g. RTDC-5, Synthesis Report, D-No 5.2.3), special emphasis was put on the investigation and modelling of near-field processes in a candidate host rock: http://project.nf-pro.org/workspaces/rtdc5/deliverables/d5_2_3_rtdc_5_synthesis_report_final_version. The coupled TMHC-processes under consideration mainly concern the interaction between the host rock in and near to the EDZ and the waste products in its immediate vicinity. With respect to long-term safety analyses, there is no doubt that a sound process understanding is required. However, safe disposal also requires a suitable multi-barrier-system. This has to consist of technical and geo-technical barriers (e.g. container and backfill) but also of a strong geological barrier. Comparing the self-sealing capacity of the candidate host rocks, i.e. salt, clay and crystalline rock formations, where underground rooms will be inevitably backfilled only in part for technical reasons, in a salt formation convergence by viscous deformation provokes the re-establishing of a tight system, whereas in a crystalline rock formation long-term isolation has to be guaranteed solely by the technical and geotechnical components. This work is concentrated on the question, whether convergence and reduction of open space by long-term creep will take place also in a clay-stone formation, where laboratory investigation on Opalinus Clay from the Mont Terri Rock Laboratory was performed for this purpose. Several results from the work on the long-term deformation behaviour of clay-stone exist already. Nevertheless, to the author's knowledge the sound proof of a time-dependent and non-dilatant viscous deformation in the undisturbed far-field of clay-stone is still missing. Results from the rock laboratory at the Mt. Terri site yield hints for an anisotropic state of in-situ stresses, which may continue to exist in the

  18. Speciation of neptunium after diffusion in Opalinus Clay

    Energy Technology Data Exchange (ETDEWEB)

    Reich, Tobias; Amayri, Samer; Drebert, Jakob; Froehlich, Daniel R.; Grolimund, Daniel; Rosemann, Jonathan [Mainz Univ. (Germany). Inst. of Nuclear Chemistry; Kaplan, Ugras [Paul Scherrer Institut, Villigen (Switzerland). Swiss Light Source

    2015-07-01

    Argillaceous rock formations are under consideration as a potential host rock for the construction of high-level nuclear waste repositories. Under environmental conditions the most stable oxidation states of {sup 237}Np (t{sub 1/2}=2.1 x 10{sup 6} a) are Np(IV) and Np(V). We have investigated the sorption and diffusion of the more mobile Np(V) in Opalinus Clay (OPA, Mont Terri, Switzerland) (Wu et al. 2009, Froehlich et al. 2011 and 2012 a). OPA, which is present in Switzerland and southern Germany, possesses a micro-scale heterogeneity and is composed of several types of clay minerals, but also of calcite, quartz and iron(II)-bearing minerals. In our previous diffusion (Wu et al. 2009) and anaerobic sorption experiments (Froehlich et al. 2011), we observed higher distribution coefficients, K{sub d}, than expected from batch experiments performed in air, indicating that a partial reduction of Np(V) to Np(IV) had occurred. To test this hypothesis, different sorption and diffusion samples with Np(V) were prepared at pH 7.6 for spatially resolved molecular-level investigations at the microXAS beamline at the Swiss Light Source (PSI, Villigen, Switzerland) (Froehlich et al. 2012 b). Elemental distributions of Ca, Fe and Np have been determined by μ-XRF mapping. Regions of high Np concentration were subsequently investigated by Np L{sub III}-edge μ-XANES. In most samples Np spots with considerable amounts of tetravalent Np could be found, even when the experiments were performed under ambient-air conditions. In some cases, almost pure Np(IV) L{sub III}-edge XANES spectra were recorded. In case of the anaerobic sorption sample, a clear correlation between Np and Fe was observed by μ-XRF, indicating that iron(II)-bearing minerals could be responsible for the reduction of Np(V). μ-XRD measurements of this sample showed that pyrite is at least one of the redox-active phases determining the speciation of Np in OPA. In this case, Np was accumulated on pyrite, indicating

  19. Diffusion Experiments in Opalinus Clay: Laboratory, Large-Scale Diffusion Experiments and Microscale Analysis by RBS.

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Gutierrez, M.; Alonso de los Rios, U.; Missana, T.; Cormenzana, J.L.; Mingarro, M.; Morejon, J.; Gil, P.

    2008-08-06

    The Opalinus Clay (OPA) formation in the Zurcher Weiland (Switzerland) is a potential host rock for a repository for high-level radioactive waste. Samples collected in the Mont Terri Underground Rock Laboratory (URL), where the OPA formation is located at a depth between -200 and -300 m below the surface, were used to study the radionuclide diffusion in clay materials. Classical laboratory essays and a novel experimental set-up for large-scale diffusion experiments were performed together to a novel application of the nuclear ion beam technique Rutherford Backscattering Spectrometry (RBS), to understand the transport properties of the OPA and to enhance the methodologies used for in situ diffusion experiments. Through-Diffusion and In-Diffusion conventional laboratory diffusion experiments were carried out with HTO, 36{sup C}l-, I-, 22{sup N}a, 75{sup S}e, 85{sup S}r, 233{sup U}, 137{sup C}s, 60{sup C}o and 152{sup E}u. Large-scale diffusion experiments were performed with HTO, 36{sup C}l, and 85{sup S}r, and new experiments with 60{sup C}o, 137{sup C}s and 152{sup E}u are ongoing. Diffusion experiments with RBS technique were done with Sr, Re, U and Eu. (Author) 38 refs.

  20. Microbial investigations in Opalinus clay from Mont Terri and in Callovo-Oxfordian argillite from Meuse/Haute-Marne

    International Nuclear Information System (INIS)

    Poulain, S.

    2006-12-01

    The subject of this Ph.D. thesis deals with research achieved in the context of the Axis 2 of the law Bataille voted on December 30, 1991 about the possibility of building a deep geological repository for medium or high activity and long living nuclear waste. Nearby such a site, some microorganisms may influence the mobility of radionuclides coming from the waste canisters. This work consisted in looking for autochthonous microorganisms in the Opalinus clay formation from Mont Terri (Switzerland) and in the Callovo-Oxfordian argillite from Meuse/Haute-Marne (France). Microbial Investigations in these unknown unperturbed environments suggested very low microbial densities in the clayey sediments. However, new bacterial species could be isolated from those samples. In addition, a part of the allochthonous population, which has been introduced by air and human activity, could be identified in the Meuse/Haute-Marne underground research laboratory. (author)

  1. Geomechanical behaviour of Opalinus Clay at multiple scales: results from Mont Terri rock laboratory (Switzerland)

    Energy Technology Data Exchange (ETDEWEB)

    Amann, F.; Wild, K.M.; Loew, S. [Institute of Geology, Engineering Geology, Swiss Federal Institute of Technology, Zurich (Switzerland); Yong, S. [Knight Piesold Ltd, Vancouver (Canada); Thoeny, R. [Grundwasserschutz und Entsorgung, AF-Consult Switzerland AG, Baden (Switzerland); Frank, E. [Sektion Geologie (GEOL), Eidgenössisches Nuklear-Sicherheitsinspektorat (ENSI), Brugg (Switzerland)

    2017-04-15

    The paper represents a summary about our research projects conducted between 2003 and 2015 related to the mechanical behaviour of Opalinus Clay at Mont Terri. The research summarized covers a series of laboratory and field tests that address the brittle failure behaviour of Opalinus Clay, its undrained and effective strength, the dependency of petro-physical and mechanical properties on total suction, hydro-mechanically coupled phenomena and the development of a damage zone around excavations. On the laboratory scale, even simple laboratory tests are difficult to interpret and uncertainties remain regarding the representativeness of the results. We show that suction may develop rapidly after core extraction and substantially modifies the strength, stiffness, and petro-physical properties of Opalinus Clay. Consolidated undrained tests performed on fully saturated specimens revealed a relatively small true cohesion and confirmed the strong hydro-mechanically coupled behaviour of this material. Strong hydro-mechanically coupled processes may explain the stability of cores and tunnel excavations in the short term. Pore-pressure effects may cause effective stress states that favour stability in the short term but may cause longer-term deformations and damage as the pore-pressure dissipates. In-situ observations show that macroscopic fracturing is strongly influenced by bedding planes and faults planes. In tunnel sections where opening or shearing along bedding planes or faults planes is kinematically free, the induced fracture type is strongly dependent on the fault plane frequency and orientation. A transition from extensional macroscopic failure to shearing can be observed with increasing fault plane frequency. In zones around the excavation where bedding plane shearing/shearing along tectonic fault planes is kinematically restrained, primary extensional type fractures develop. In addition, heterogeneities such as single tectonic fault planes or fault zones

  2. The shale gas potential of the Opalinus Clay and Posidonia Shale in Switzerland - A first assessment

    International Nuclear Information System (INIS)

    Leu, W.; Gautschi, A.

    2014-01-01

    There has been recent interest in the shale gas potential of the Opalinus Clay and Posidonia Shale (Middle and Lower Jurassic) below the Swiss Molasse Basin in the light of the future role of domestic gas production within the expected future energy shift of Switzerland and possible conflicts in underground use. The Opalinus Clay of northern Switzerland is a potential host rock for repositories of both high-level and low-to-intermediate level radioactive waste and the exploitation of shale gas resources within or below this formation would represent a serious conflict of use. Well data from northern Switzerland shows that these two formations are unsuitable for future shale gas recovery. They never reached the gas window during their burial history (maturity values are ≤ 0.6% R o ) and as a consequence never generated significant quantities of thermogenic gas. Geochemical data further shows that the average TOC values are in the range of 0.7%, i.e. clearly below accepted values of more than 1.5% for prospective shales. A review of available exploration data for the Opalinus Clay and Posidonia Shale in the deeper and western part of the Swiss Molasse Basin indicate that their shale gas potential may be substantial. The gross Posidonia Shale thickness increases from central Switzerland from less than 10 m to over 100 m in the Yverdon-Geneva area and is characterised by numerous bituminous intervals. A simplified shale gas resource calculation results for a geologically likely scenario in a technically recoverable gas volume of ∼120 billions m 3 . The current database for such estimates is small and as a consequence, the uncertainties are large. However, these first encouraging results support a more detailed exploration phase with specific geochemical and petrophysical analysis of existing rock and well log data. (authors)

  3. The shale gas potential of the Opalinus Clay and Posidonia Shale in Switzerland - A first assessment

    Energy Technology Data Exchange (ETDEWEB)

    Leu, W. [Geoform Ltd, Villeneuve (Switzerland); Gautschi, A. [NAGRA, Wettingen (Switzerland)

    2014-07-01

    There has been recent interest in the shale gas potential of the Opalinus Clay and Posidonia Shale (Middle and Lower Jurassic) below the Swiss Molasse Basin in the light of the future role of domestic gas production within the expected future energy shift of Switzerland and possible conflicts in underground use. The Opalinus Clay of northern Switzerland is a potential host rock for repositories of both high-level and low-to-intermediate level radioactive waste and the exploitation of shale gas resources within or below this formation would represent a serious conflict of use. Well data from northern Switzerland shows that these two formations are unsuitable for future shale gas recovery. They never reached the gas window during their burial history (maturity values are ≤ 0.6% R{sub o}) and as a consequence never generated significant quantities of thermogenic gas. Geochemical data further shows that the average TOC values are in the range of 0.7%, i.e. clearly below accepted values of more than 1.5% for prospective shales. A review of available exploration data for the Opalinus Clay and Posidonia Shale in the deeper and western part of the Swiss Molasse Basin indicate that their shale gas potential may be substantial. The gross Posidonia Shale thickness increases from central Switzerland from less than 10 m to over 100 m in the Yverdon-Geneva area and is characterised by numerous bituminous intervals. A simplified shale gas resource calculation results for a geologically likely scenario in a technically recoverable gas volume of ∼120 billions m{sup 3}. The current database for such estimates is small and as a consequence, the uncertainties are large. However, these first encouraging results support a more detailed exploration phase with specific geochemical and petrophysical analysis of existing rock and well log data. (authors)

  4. Mechanical properties, mineralogical composition, and micro fabric of Opalinus Clay. Sandy and shaly facies (Mont Terri, Switzerland)

    International Nuclear Information System (INIS)

    Kaufhold, Annette; Graesle, Werner; Plischke, Ingo

    2015-01-01

    For the safe disposal of high-level radioactive waste, different host rocks are currently considered. The favorable properties of claystone are low permeability, retention capacity for some radionuclides, and the ability to self-seal cracks, e.g. by swelling or time-dependent compaction creep. For the understanding of the long-term behavior of clay host rocks, the interaction between mechanical behavior, micro fabric, and mineral composition has to be understood (Bock et al., 2010). In the international research project Mont Terri (Switzerland) the Opalinus Clay (Jurassic Formation) is investigated in an underground rock laboratory (URL). In the present study the relationship between mechanical, mineralogical and micro fabric properties were studied on representative samples of the sandy and shaly facies of the Opalinus Clay (OPA) from Mont Terri. The mineral composition of all samples was analysed by using a complex mineral phase analysis. Therefore, the results of the X-ray diffraction, X-ray fluoreszence, organic and inorganic carbonate analysis (LECO) were adjusted with each other. In the case of the sandy facies (OPA) the mechanical strength inrcreases with increasing carbonate content. Here small carbonate particles form the matrix and act as stabilisator. The carbonates of the shaly facies (OPA), on the other hand, are mainly fossil fragments (e.g. shells) aligned parallel to bedding. These large carbonate particles are acting as predetermined breaking surfaces. Hence, in the case of shaly facies (OPA) the mechanical strength decreases with increasing carbonate content. Image Analyses (Fiji registered ) of scattering electron microscope images of polished sections proved the determined microstructural differences. Besides, carbonate particles in the sandy facies are mostly isometric, in contrast carbonates of the shaly facies show different shapes. This is explained further in terms of the aspect ratio. The mechanical tests were carried out as triaxial

  5. Mechanical properties, mineralogical composition, and micro fabric of Opalinus Clay. Sandy and shaly facies (Mont Terri, Switzerland)

    Energy Technology Data Exchange (ETDEWEB)

    Kaufhold, Annette; Graesle, Werner [BGR Hannover (Germany); Plischke, Ingo

    2015-07-01

    For the safe disposal of high-level radioactive waste, different host rocks are currently considered. The favorable properties of claystone are low permeability, retention capacity for some radionuclides, and the ability to self-seal cracks, e.g. by swelling or time-dependent compaction creep. For the understanding of the long-term behavior of clay host rocks, the interaction between mechanical behavior, micro fabric, and mineral composition has to be understood (Bock et al., 2010). In the international research project Mont Terri (Switzerland) the Opalinus Clay (Jurassic Formation) is investigated in an underground rock laboratory (URL). In the present study the relationship between mechanical, mineralogical and micro fabric properties were studied on representative samples of the sandy and shaly facies of the Opalinus Clay (OPA) from Mont Terri. The mineral composition of all samples was analysed by using a complex mineral phase analysis. Therefore, the results of the X-ray diffraction, X-ray fluoreszence, organic and inorganic carbonate analysis (LECO) were adjusted with each other. In the case of the sandy facies (OPA) the mechanical strength inrcreases with increasing carbonate content. Here small carbonate particles form the matrix and act as stabilisator. The carbonates of the shaly facies (OPA), on the other hand, are mainly fossil fragments (e.g. shells) aligned parallel to bedding. These large carbonate particles are acting as predetermined breaking surfaces. Hence, in the case of shaly facies (OPA) the mechanical strength decreases with increasing carbonate content. Image Analyses (Fiji {sup registered}) of scattering electron microscope images of polished sections proved the determined microstructural differences. Besides, carbonate particles in the sandy facies are mostly isometric, in contrast carbonates of the shaly facies show different shapes. This is explained further in terms of the aspect ratio. The mechanical tests were carried out as triaxial

  6. Concrete-Opalinus clay interaction

    International Nuclear Information System (INIS)

    Jenni, A.; Maeder, U.; Lerouge, C.; Gaboreau, S.; Schwyn, B.

    2012-01-01

    Document available in extended abstract form only. Designs for deep geologic disposal of radioactive waste foresee cementitious materials as structural elements, backfill or waste matrix. Therefore, studies of interactions between cement and all other materials involved are important. Interactions are mostly driven by chemical gradients in pore water and might lead to mineralogical alterations in the barrier system, which in turn influence properties like swelling pressure, permeability, or specific retention in case of clay materials. Existing laboratory and in-situ studies using clay-stone revealed significant alteration in both cement and clay-stone. Phase dissolution, precipitation, and carbonation, were found to cause an overall porosity increase in the cement with a possible decrease close to the interface, and clogging in the clay-stone [2]. Most of the work was done on cement pastes rather than concretes to avoid analytical complications caused by aggregates, and the scale of investigation was chosen in the range of centimetres rather than micrometers. The Cement-Clay Interaction (CI) experiment at the Mont Terri Underground Laboratory (St. Ursanne, Switzerland) aims at replicating some of the processes at interfaces to be expected.For this purpose, two vertical cylindrical boreholes (384 mm diameter, up to 10 m length) in Opalinus Clay (OPA) were filled with layers of three different concretes and bentonite. The concrete formulations are based on common aggregate content and grain size distributions, combined with three different cements: Portland cement (OPC), ESDRED cement especially designed for repository applications (40% of cement substituted with silica fume), and low alkali cement (LAC, containing slag and nano-silica).In this study, we present a characterisation of the three concrete-OPA interfaces after two years of alteration and deduce possible mechanisms. Backscattered electron (BE) imaging and energy dispersive spectrum (EDX) element mapping

  7. Experiments on thermo-hydro-mechanical behaviour of Opalinus Clay at Mont Terri rock laboratory, Switzerland

    Directory of Open Access Journals (Sweden)

    Paul Bossart

    2017-06-01

    Full Text Available Repositories for deep geological disposal of radioactive waste rely on multi-barrier systems to isolate waste from the biosphere. A multi-barrier system typically comprises the natural geological barrier provided by the repository host rock – in our case the Opalinus Clay – and an engineered barrier system (EBS. The Swiss repository concept for spent fuel and vitrified high-level waste (HLW consists of waste canisters, which are emplaced horizontally in the middle of an emplacement gallery and are separated from the gallery wall by granular backfill material (GBM. We describe here a selection of five in-situ experiments where characteristic hydro-mechanical (HM and thermo-hydro-mechanical (THM processes have been observed. The first example is a coupled HM and mine-by test where the evolution of the excavation damaged zone (EDZ was monitored around a gallery in the Opalinus Clay (ED-B experiment. Measurements of pore-water pressures and convergences due to stress redistribution during excavation highlighted the HM behaviour. The same measurements were subsequently carried out in a heater test (HE-D where we were able to characterise the Opalinus Clay in terms of its THM behaviour. These yielded detailed data to better understand the THM behaviours of the granular backfill and the natural host rock. For a presentation of the Swiss concept for HLW storage, we designed three demonstration experiments that were subsequently implemented in the Mont Terri rock laboratory: (1 the engineered barrier (EB experiment, (2 the in-situ heater test on key-THM processes and parameters (HE-E experiment, and (3 the full-scale emplacement (FE experiment. The first demonstration experiment has been dismantled, but the last two ones are on-going.

  8. Fifteen years of microbiological investigation in Opalinus Clay at the Mont Terri rock laboratory (Switzerland)

    Energy Technology Data Exchange (ETDEWEB)

    Leupin, O.X. [National Cooperative for the Disposal of Radioactive Waste (NAGRA), Wettingen (Switzerland); Bernier-Latmani, R.; Bagnoud, A. [Swiss Federal Office of Technology EPFL, Lausanne (Switzerland); Moors, H.; Leys, N.; Wouters, K. [Belgian Nuclear Research Centre SCK-CEN, Mol (Belgium); Stroes-Gascoyne, S. [University of Saskatchewan, Saskatoon (Canada)

    2017-04-15

    Microbiological studies related to the geological disposal of radioactive waste have been conducted at the Mont Terri rock laboratory in Opalinus Clay, a potential host rock for a deep geologic repository, since 2002. The metabolic potential of microorganisms and their response to excavation-induced effects have been investigated in undisturbed and disturbed claystone cores and in pore- (borehole) water. Results from nearly 15 years of research at the Mont Terri rock laboratory have shown that microorganisms can potentially affect the environment of a repository by influencing redox conditions, metal corrosion and gas production and consumption under favourable conditions. However, the activity of microorganisms in undisturbed Opalinus Clay is limited by the very low porosity, the low water activity, and the largely recalcitrant nature of organic matter in the claystone formation. The presence of microorganisms in numerous experiments at the Mont Terri rock laboratory has suggested that excavation activities and perturbation of the host rock combined with additional contamination during the installation of experiments in boreholes create favourable conditions for microbial activity by providing increased space, water and substrates. Thus effects resulting from microbial activity might be expected in the proximity of a geological repository i.e., in the excavation damaged zone, the engineered barriers, and first containments (the containers). (authors)

  9. Fifteen years of microbiological investigation in Opalinus Clay at the Mont Terri rock laboratory (Switzerland)

    International Nuclear Information System (INIS)

    Leupin, O.X.; Bernier-Latmani, R.; Bagnoud, A.; Moors, H.; Leys, N.; Wouters, K.; Stroes-Gascoyne, S.

    2017-01-01

    Microbiological studies related to the geological disposal of radioactive waste have been conducted at the Mont Terri rock laboratory in Opalinus Clay, a potential host rock for a deep geologic repository, since 2002. The metabolic potential of microorganisms and their response to excavation-induced effects have been investigated in undisturbed and disturbed claystone cores and in pore- (borehole) water. Results from nearly 15 years of research at the Mont Terri rock laboratory have shown that microorganisms can potentially affect the environment of a repository by influencing redox conditions, metal corrosion and gas production and consumption under favourable conditions. However, the activity of microorganisms in undisturbed Opalinus Clay is limited by the very low porosity, the low water activity, and the largely recalcitrant nature of organic matter in the claystone formation. The presence of microorganisms in numerous experiments at the Mont Terri rock laboratory has suggested that excavation activities and perturbation of the host rock combined with additional contamination during the installation of experiments in boreholes create favourable conditions for microbial activity by providing increased space, water and substrates. Thus effects resulting from microbial activity might be expected in the proximity of a geological repository i.e., in the excavation damaged zone, the engineered barriers, and first containments (the containers). (authors)

  10. Project Opalinus Clay: Sorption Data Bases For Opalinus Clay Influenced By A High pH Plume

    Energy Technology Data Exchange (ETDEWEB)

    Bradbury, M.H.; Baeyens, B

    2004-11-01

    The interaction of groundwater with the large quantities of cement/concrete used in the construction and backfilling of emplacement tunnels containing long-lived intermediate level radioactive waste may give rise to the release of a pulse of hyper alkaline fluid (pH plume) into the surrounding rock. Since the pH of this plume could remain in excess of 12.5 for tens of thousands of years, many minerals in a sedimentary host rock would be unstable leading to dissolution reactions, secondary mineral precipitation and changes in groundwater chemistry. An Opalinus day formation in the Zuercher Weinland, is under consideration by Nagra as a potential host rock for a repository of spent fuel (SF), vitrified high-level waste (HLW) from reprocessing of spent fuel and long-lived intermediate-Ievel radioactive waste (ILW). The purpose of this report is to assess the effects of the interactions between a pH plume and Opalinus day on the sorption properties of the formation and to provide appropriate sorption data bases. (author)

  11. Project Opalinus clay Zuercher Weinland of Nagra. Evaluation of the geo-scientific data base and of the construction engineering aspects; Projekt Opalinuston Zuercher Weinland der Nagra. Beurteilung der erdwissenschaftlichen Datengrundlagen und der bautechnischen Machbarkeit

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2005-02-15

    In this report the Commission for Nuclear Waste Management (KNE) assesses the geological and engineering aspects of the project Opalinus Clay, in which Nagra demonstrates the postclosure safety of geological disposal of spent fuel (SF), vitrified high-level wastes (HLW) and intermediate-level wastes (ILW) in a repository in the Opalinus Clay of the Zuercher Weinland in northern Switzerland. After in-depth examination of the geological database, KNE concludes that the demonstration of a suitable geological site for final disposal of SF, HLW and ILW in the Opalinus Clay of the Zuercher Weinland has been achieved. The geological assumptions Nagra uses for the assessment of long-term safety are based on data that have been carefully collected and interpreted. KNE acknowledges that Nagra interpreted the geological data correctly and adequately using state-of-the-art techniques. In case of lacking information, Nagra has used conservative or worst-case assumptions. The information documented by Nagra represents a good synthesis of field, laboratory and literature data. The tectonic situation of the Zuercher Weinland was examined in great details by Nagra. In the centre of the investigated region, where the Opalinus Clay occurs at 600 to 750 meters depth, the 3D-seismic data confirm its undisturbed stratification in an area of about 15 km{sup 2}. Analysis and interpretation of the available information on the geological evolution provides no indication that erosion would expose the confining units above the Opalinus Clay within the next million years. The Opalinus Clay in the Zuercher Weinland is quite homogeneous and about 110 m thick. The properties of this rock are examined and found to be favourable for a repository. The dominance of the fine grain size and the high clay content indicate a very low hydraulic conductivity suitable for the isolation of radioactive wastes. Pore water extracted from drill-core samples is saline and has remained trapped for millions of

  12. The opalinus clay project - disposal of medium and highly-active nuclear wastes

    International Nuclear Information System (INIS)

    Mueller, U.

    2003-01-01

    This article describes the project to demonstrate the feasibility of disposing of long-living medium-active and highly-radioactive nuclear wastes in sedimentary rock in Switzerland. The disposal tasks to be carried out are reviewed and the solutions proposed are described, including short-term handling, intermediate storage and final disposal of low, medium and highly-active wastes. The present state of affairs is described and, in particular, the feasibility of implementing a final storage facility in the opalinus clay beds to be found in northern Switzerland. The project for such a facility in the wine-growing area of the canton of Zurich is described in detail, including the storage concept, the technology to be used and operational aspects as well as questions of safety

  13. Microbial investigations in Opalinus clay from Mont Terri and in Callovo-Oxfordian argillite from Meuse/Haute-Marne; Caracterisation microbiologique de l'argile a opalinus du Mont Terri et de l'argilite du callovo-oxfordien de Meuse/Haute-Marne

    Energy Technology Data Exchange (ETDEWEB)

    Poulain, S

    2006-12-15

    The subject of this Ph.D. thesis deals with research achieved in the context of the Axis 2 of the law Bataille voted on December 30, 1991 about the possibility of building a deep geological repository for medium or high activity and long living nuclear waste. Nearby such a site, some microorganisms may influence the mobility of radionuclides coming from the waste canisters. This work consisted in looking for autochthonous microorganisms in the Opalinus clay formation from Mont Terri (Switzerland) and in the Callovo-Oxfordian argillite from Meuse/Haute-Marne (France). Microbial Investigations in these unknown unperturbed environments suggested very low microbial densities in the clayey sediments. However, new bacterial species could be isolated from those samples. In addition, a part of the allochthonous population, which has been introduced by air and human activity, could be identified in the Meuse/Haute-Marne underground research laboratory. (author)

  14. Three-dimensional FDEM numerical simulation of failure processes observed in Opalinus Clay laboratory samples

    Directory of Open Access Journals (Sweden)

    Omid Mahabadi

    2014-12-01

    Full Text Available This study presents the first step of a research project that aims at using a three-dimensional (3D hybrid finite-discrete element method (FDEM to investigate the development of an excavation damaged zone (EDZ around tunnels in a clay shale formation known as Opalinus Clay. The 3D FDEM was first calibrated against standard laboratory experiments, including Brazilian disc test and uniaxial compression test. The effect of increasing confining pressure on the mechanical response and fracture propagation of the rock was quantified under triaxial compression tests. Polyaxial (or true triaxial simulations highlighted the effect of the intermediate principal stress (σ2 on fracture directions in the model: as the intermediate principal stress increased, fractures tended to align in the direction parallel to the plane defined by the major and intermediate principal stresses. The peak strength was also shown to vary with changing σ2.

  15. Pore-water evolution and solute-transport mechanisms in Opalinus Clay at Mont Terri and Mont Russelin (Canton Jura, Switzerland)

    Energy Technology Data Exchange (ETDEWEB)

    Mazurek, M. [Institute of Geological Sciences, University of Berne, Berne (Switzerland); Haller de, A. [Earth and Environmental Sciences, University of Geneva, Geneva (Switzerland)

    2017-04-15

    Data pertinent to pore-water composition in Opalinus Clay in the Mont Terri and Mont Russelin anticlines have been collected over the last 20 years from long-term in situ pore-water sampling in dedicated boreholes, from laboratory analyses on drill cores and from the geochemical characteristics of vein infills. Together with independent knowledge on regional geology, an attempt is made here to constrain the geochemical evolution of the pore-waters. Following basin inversion and the establishment of continental conditions in the late Cretaceous, the Malm limestones acted as a fresh-water upper boundary leading to progressive out-diffusion of salinity from the originally marine pore-waters of the Jurassic low-permeability sequence. Model calculations suggest that at the end of the Palaeogene, pore-water salinity in Opalinus Clay was about half the original value. In the Chattian/Aquitanian, partial evaporation of sea-water occurred. It is postulated that brines diffused into the underlying sequence over a period of several Myr, resulting in an increase of salinity in Opalinus Clay to levels observed today. This hypothesis is further supported by the isotopic signatures of SO{sub 4}{sup 2-} and {sup 87}Sr/{sup 86}Sr in current pore-waters. These are not simple binary mixtures of sea and meteoric water, but their Cl{sup -} and stable water-isotope signatures can be potentially explained by a component of partially evaporated sea-water. After the re-establishment of fresh-water conditions on the surface and the formation of the Jura Fold and Thrust Belt, erosion caused the activation of aquifers embedding the low-permeability sequence, leading to the curved profiles of various pore-water tracers that are observed today. Fluid flow triggered by deformation events during thrusting and folding of the anticlines occurred and is documented by infrequent vein infills in major fault structures. However, this flow was spatially focussed and of limited duration and so did not

  16. Microbial investigations in Opalinus clay from Mont Terri and in Callovo-Oxfordian argillite from Meuse/Haute-Marne; Caracterisation microbiologique de l'argile a opalinus du Mont Terri et de l'argilite du callovo-oxfordien de Meuse/Haute-Marne

    Energy Technology Data Exchange (ETDEWEB)

    Poulain, S

    2006-12-15

    The subject of this Ph.D. thesis deals with research achieved in the context of the Axis 2 of the law Bataille voted on December 30, 1991 about the possibility of building a deep geological repository for medium or high activity and long living nuclear waste. Nearby such a site, some microorganisms may influence the mobility of radionuclides coming from the waste canisters. This work consisted in looking for autochthonous microorganisms in the Opalinus clay formation from Mont Terri (Switzerland) and in the Callovo-Oxfordian argillite from Meuse/Haute-Marne (France). Microbial Investigations in these unknown unperturbed environments suggested very low microbial densities in the clayey sediments. However, new bacterial species could be isolated from those samples. In addition, a part of the allochthonous population, which has been introduced by air and human activity, could be identified in the Meuse/Haute-Marne underground research laboratory. (author)

  17. Hydrogeology of a fractured shale (Opalinus Clay): Implications for deep geological disposal of radioactive wastes

    Science.gov (United States)

    Gautschi, Andreas

    2001-01-01

    As part of the Swiss programme for high-level radioactive-waste disposal, a Jurassic shale (Opalinus Clay) is being investigated as a potential host rock. Observations in clay pits and the results of a German research programme focusing on hazardous waste disposal have demonstrated that, at depths of 10-30 m, the permeability of the Opalinus Clay decreases by several orders of magnitude. Hydraulic tests in deeper boreholes (test intervals below 300 m) yielded hydraulic conductivities Las observaciones efectuadas en pozos en arcilla y los resultados de un programa de estudio alemán sobre eliminación de residuos peligrosos han demostrado que, a profundidades de entre 10 y 30 m, la permeabilidad de la Arcilla Opalina decrece en varios órdenes de magnitud. Los ensayos hidráulicos realizados en sondeos más profundos (en intervalos situados a más de 300 m) proporcionaron conductividades hidráulicas inferiores a 10-12 m/s, pese a que algunos de los intervalos interceptaban juntas y fallas. Estas medidas son coherentes con los datos hidrogeológicos de las secciones de Arcilla Opalina existentes en 10 túneles del Jurásico Plegado, al norte de Suiza. A pesar de las fallas extensivas, apenas se hallaron indicios de entrada de agua en los más de 6.600 m de túnel. Todos los flujos tenían lugar en secciones del túnel que soportan sobrecargas inferiores a 200 m. Los datos hidráulicos son coherentes con los datos hidroquímicos e isotópicos del agua intersticial de las arcillas. Los abundantes datos hidrogeológicos -parte de los cuales proceden de medios particularmente desfavorables desde el punto de vista geológico- proporcionan argumentos de que el transporte advectivo a través de fallas y juntas no es un aspecto crítico en lo que respecta a la idoneidad de la Arcilla Opalina como almacenamiento geológico profundo de residuos.

  18. Multistep triaxial strength tests: investigating strength parameters and pore pressure effects on Opalinus Clay

    International Nuclear Information System (INIS)

    Graesle, W.

    2010-01-01

    Document available in extended abstract form only. The impact of natural variability between rock samples from a single formation is a common problem for the characterisation of THM properties of rocks. Data variation arising from heterogeneity between samples often obscures details of material behaviour. Besides efforts to reduce this statistical noise by careful selection of samples, there are essentially two approaches to overcome this problem: - To generate very large data sets for better statistics. - To avoid the impact of natural variability by yielding an extensive data set from a single sample. The multistep strength test follows the latter approach to characterise the mechanical behaviour of Opalinus Clay from Mont Terri and the possible impact of pore pressure effects. The concept of the multistep strength test comprises three test sections, each focused on the investigation of one mechanical characteristic of Opalinus Clay. Any section is composed of a series of strain controlled load cycles at various levels of confining pressure. 1) The linear elastic limit, i.e. the onset of nonlinearity in the stress-strain-relationship σ dev (ε 1 ) during strain-controlled triaxial loading, is determined in section 1. It defines a lower limit for the onset of damage. Avoiding sample damage is essential during this test section to ensure that all measurements reflect the behaviour of undisturbed material. Therefore, a rather strict and well detectable criterion for the onset of nonlinearity is required to enable a timely termination of any load phase. 2) Section 2 is focused on shear strength. Any load cycle is stopped as soon as peak stress is detected. As progressive damage of the sample is unavoidable during this process, it must be expected that only very few measured peak stresses approximately represent properties of the undamaged material. 3) Test section 3 is a conventional test of residual strength. Tests are carried out on cylindrical samples (100 mm

  19. Sorption of radionuclides by tertiary clays

    International Nuclear Information System (INIS)

    Wagner, J.F.; Czurda, K.A.

    1990-01-01

    The sorption capacity of different clay types for some metals (Co, Cs, Sr and Zn), occurring as common radionuclides in radioactive waste deposits, had been analysed by a static (batch technique) and a dynamic method (percolation tests, in which the driving force is a hydraulic gradient). Sorption capacity generally increased with an increasing pH of solution. A decrease of sorption capacity had been observed in the order Zn > Cs ≥ Co > Sr for the batch and Cs > Zn > Sr > Co for the percolation tests. Clay marls showed a distinctly higher sorption respectively retention capacity as pure clays. Sorption capacity depends on solution parameters like type and concentration of radionuclide, pH, salt concentration, etc., and on rock parameters like mineral content (e.g. swelling clay minerals and carbonates), organic material, rock pH, micro fabric, etc. A third parameter of great influence is the contact time between clay and solution. The adsorption isotherms reflect two different adsorption mechanisms: a very rapid adsorption (a few minutes) on the external surfaces of clay minerals and a slow adsorption process (weeks and longer), due to the diffusion of metal ions into the interlayer space of clay minerals. 12 refs., 9 figs., 1 tab

  20. Thermal volume changes in clays and clay-stones

    International Nuclear Information System (INIS)

    Delage, P.; Sulem, J.; Mohajerani, M.; Tang, A.M.; Monfared, M.

    2012-01-01

    Document available in extended abstract form only. The disposal of high activity exothermic radioactive waste at great depth in clay host rocks will induce a temperature elevation that has been investigated in various underground research laboratories in Belgium, France and Switzerland through in-situ tests. Thermal effects are better known in clays (in particular Boom clay) than in clay-stone (e.g. Opalinus clay and Callovo-Oxfordian clay-stone). In terms of volume changes, Figure 1 confirms the findings of Hueckel and Baldi (1990) that volume changes depend on the over-consolidation ratio (OCR) of the clay. In drained conditions, normally consolidated clays exhibit plastic contraction when heated, whereas over-consolidated clay exhibit elastic dilation. The nature of thermal volume changes in heated clays obviously has a significant effect on thermally induced pore pressures, when drainage is not instantaneous like what occurs in-situ. Compared to clays, the thermal volume change behaviour of clay-stones is less well known than that of clays. clay-stone are a priori suspected to behave like over-consolidated clays. In this paper, a comparison of recent results obtained in the laboratory on the drained thermal volume changes of clay-stones is presented and discussed. It is difficult to run drained mechanical tests in clay-stones like the Opalinus clay and the Callovo-Oxfordian clay-stone because of their quite low permeability (10 -12 - 10 -13 m/s). This also holds true for thermal tests. Due to the significant difference in thermal expansion coefficient between minerals and water, it is necessary to adopt very slow heating rate (0.5 - 1 C/h) to avoid any thermal pressurization. To do so, a new hollow cylinder apparatus (100 mm external diameter, 60 mm internal diameter) with lateral drainages reducing the drainage length to half the sample thickness (10 mm) has been developed (Monfared et al. 2011). The results of a drained cyclic thermal test carried out on

  1. Impact of the electron donor on in situ microbial nitrate reduction in Opalinus Clay: results from the Mont Terri rock laboratory (Switzerland)

    Energy Technology Data Exchange (ETDEWEB)

    Bleyen, N.; Smets, S. [Belgian Nuclear Research Centre SCK-CEN, Mol (Belgium); Small, J. [National Nuclear Laboratory NLL, Warrington (United Kingdom); and others

    2017-04-15

    At the Mont Terri rock laboratory (Switzerland), an in situ experiment is being carried out to examine the fate of nitrate leaching from nitrate-containing bituminized radioactive waste, in a clay host rock for geological disposal. Such a release of nitrate may cause a geochemical perturbation of the clay, possibly affecting some of the favorable characteristics of the host rock. In this in situ experiment, combined transport and reactivity of nitrate is studied inside anoxic and water-saturated chambers in a borehole in the Opalinus Clay. Continuous circulation of the solution from the borehole to the surface equipment allows a regular sampling and online monitoring of its chemical composition. In this paper, in situ microbial nitrate reduction in the Opalinus Clay is discussed, in the presence or absence of additional electron donors relevant for the disposal concept and likely to be released from nitrate-containing bituminized radioactive waste: acetate (simulating bitumen degradation products) and H{sub 2} (originating from radiolysis and corrosion in the repository). The results of these tests indicate that - in case microorganisms would be active in the repository or the surrounding clay - microbial nitrate reduction can occur using electron donors naturally present in the clay (e.g. pyrite, dissolved organic matter). Nevertheless, non-reactive transport of nitrate in the clay is expected to be the main process. In contrast, when easily oxidizable electron donors would be available (e.g. acetate and H{sub 2}), the microbial activity will be strongly stimulated. Both in the presence of H{sub 2} and acetate, nitrite and nitrogenous gases are predominantly produced, although some ammonium can also be formed when H{sub 2} is present. The reduction of nitrate in the clay could have an impact on the redox conditions in the pore-water and might also lead to a gas-related perturbation of the host rock, depending on the electron donor used during denitrification

  2. Technetium migration in natural clays

    International Nuclear Information System (INIS)

    Luebke, Maria

    2015-01-01

    The present work was performed within the joint research project ''Retention of repository relevant radionuclides in argillaceous rocks and saline systems'' (contract no.: 02E10981), funded by the Federal Ministry for Economic Affairs and Energy (BMWi). The aim was to obtain first insights into the interaction of the long-lived fission product technetium and natural clay with regard to a repository for high-level nuclear waste. For this purpose Opalinus Clay from Mont Terri (northern Switzerland) was used as a reference material. The nuclide technetium-99 will contribute to the radiotoxicity of spent nuclear fuel for more than thousand years due to its long half-live. In case of a leakage of the storage vessels, the geochemistry of technetium is determined by its oxidation state, at which only the oxidation states +IV and +VII are relevant. Because of the high solubility and low affinity to sorption on surfaces of minerals, Tc(VII) is considered to be very mobile and thus the most hazardous species. The focuses of this study therefore are diffusion experiments with this mobile species and investigations of the effect of ferrous iron on the mobility and speciation of technetium.rnThe interaction of technetium and Opalinus Clay was studied in sorption and diffusion experiments varying several parameters (pH value, addition of reducing agents, effect of oxygen, diffusion pathways). In the course of this study spatially resolved investigations of the speciation have been performed on Opalinus Clay thin sections and bore cores for the first time. In addition to the speciation, further information regarding elemental distributions and crystalline phases near technetium enrichments were obtained. Supplementary investigations of powder samples allowed determining the molecular structure of technetium on the clay surface.rnBoth the combination of sorption experiments with spectroscopic investigations and the diffusion experiment exhibit a reduction of Tc

  3. Project Opalinus Clay: Radionuclide Concentration Limits in the Near-Field of a Repository for Spent Fuel and Vitrified High-Level Waste

    Energy Technology Data Exchange (ETDEWEB)

    Berner, U

    2002-10-01

    The disposal feasibility study currently performed by Nagra includes a succession of quantitative models, aiming at describing the fate of radionuclides potentially escaping from the repository system. In this chain of models the present report provides the so called 'solubility limits' (maximum expected concentrations) for safety relevant radionuclides from SF/HLW wastes, disposed of in a reducing clay (Opalinus Clay, bentonite) environment. Solubility and speciation calculations in bentonite pore waters were performed using the very recently updated Nagra/PSI Chemical Thermodynamic Data Base (TDB) for the majority of the 37 elements addressed as potentially relevant. Particularly for the most relevant actinides, the straightforward applications with this updated TDB yielded results in contradiction to chemical analogy considerations. This was a consequence of incomplete data and called for problem specific TDB extensions, which were evaluated in a separate study. However, a summary of these problem specific extensions is provided in section 4.1. The results presented in this report solely depend on geochemical model calculations. Thus, it is of utmost importance that the underlying data and assumptions are made clear to the reader. In order to ensure traceability, all thermodynamic data not included in the Nagra/PSI TDB are explicitly specified in the report, in order to provide complete documentation for quality assurance and for comprehensibility. In order to clearly distinguish between results derived from data carefully reviewed in the Nagra/PSI TDB and those calculated from 'other' data, the summary of expected maximum concentrations provided in Table 1 includes two columns. The heading CALCULATED provides maximum concentrations based on data fully documented in the updated TDB, whereas maximum concentrations, which include additional problem specific data and/or data from other sources, are given under the heading RECOMMENDED. The

  4. Project Opalinus Clay: Radionuclide Concentration Limits in the Near-Field of a Repository for Spent Fuel and Vitrified High-Level Waste

    International Nuclear Information System (INIS)

    Berner, U.

    2002-10-01

    The disposal feasibility study currently performed by Nagra includes a succession of quantitative models, aiming at describing the fate of radionuclides potentially escaping from the repository system. In this chain of models the present report provides the so called 'solubility limits' (maximum expected concentrations) for safety relevant radionuclides from SF/HLW wastes, disposed of in a reducing clay (Opalinus Clay, bentonite) environment. Solubility and speciation calculations in bentonite pore waters were performed using the very recently updated Nagra/PSI Chemical Thermodynamic Data Base (TDB) for the majority of the 37 elements addressed as potentially relevant. Particularly for the most relevant actinides, the straightforward applications with this updated TDB yielded results in contradiction to chemical analogy considerations. This was a consequence of incomplete data and called for problem specific TDB extensions, which were evaluated in a separate study. However, a summary of these problem specific extensions is provided in section 4.1. The results presented in this report solely depend on geochemical model calculations. Thus, it is of utmost importance that the underlying data and assumptions are made clear to the reader. In order to ensure traceability, all thermodynamic data not included in the Nagra/PSI TDB are explicitly specified in the report, in order to provide complete documentation for quality assurance and for comprehensibility. In order to clearly distinguish between results derived from data carefully reviewed in the Nagra/PSI TDB and those calculated from 'other' data, the summary of expected maximum concentrations provided in Table 1 includes two columns. The heading CALCULATED provides maximum concentrations based on data fully documented in the updated TDB, whereas maximum concentrations, which include additional problem specific data and/or data from other sources, are given under the heading RECOMMENDED. The present study also pays

  5. Characterisation of gas transport properties of the Opalinus clay, a potential host rock formation for radioactive waste disposal

    International Nuclear Information System (INIS)

    Marschall, P.; Horseman, S.; Gimmi, T.

    2005-01-01

    The Opalinus Clay in Northern Switzerland has been identified as a potential host rock formation for the disposal of radioactive waste. Comprehensive understanding of gas transport processes through this low-permeability formation forms a key issue in the assessment of repository performance. Field investigations and laboratory experiments suggest an intrinsic permeability of the Opalinus Clay in the order of 10 -20 to 10 -21 m 2 and a moderate anisotropy ratio ≤ 10. Porosity depends on clay content and burial depth; values of ∼ 0.12 are reported for the region of interest. Porosimetry indicates that about 10-30% of voids can be classed as macro-pores, corresponding to an equivalent pore radius > 25 nm. The determined entry pressures are in the range of 0.4-10 MPa and exhibit a marked dependence on intrinsic permeability. Both in situ gas tests and gas permeameter tests on drill-cores demonstrate that gas transport through the rock is accompanied by pore water displacement, suggesting that classical flow concepts of immiscible displacement in porous media can be applied when the gas entry pressure (i.e. capillary threshold pressure) is less than the minimum principal stress acting within the rock. Essentially, the pore space accessible to gas flow is restricted to the network of connected macro-pores, which implies a very low degree of desaturation of the rock during the gas imbibition process. At elevated gas pressures (i.e. when gas pressure approaches the level of total stress that acts on the rock body), evidence was seen for dilatancy controlled gas transport mechanisms. Further field experiments were aimed at creating extended tensile fractures with high fracture transmissivity (hydro- or gas-fractures). The test results lead to the conclusion that gas fracturing can be largely ruled out as a risk for post-closure repository performance. (authors)

  6. Effects of post-disposal gas generation in a repository for low- and intermediate-level waste sited in the Opalinus Clay of Northern Switzerland. Technical report--08-07

    International Nuclear Information System (INIS)

    2008-10-01

    In Switzerland, Opalinus Clay was proposed as a possible host rock for a repository for low- and intermediate level radioactive waste (L/ILW). This rock is characterised by a low permeability and is therefore an excellent barrier against radionuclide transport. Because significant amounts of gas are generated in the repository, a demonstration is required that despite the low gas permeability of the Opalinus Clay the gas can escape without compromising long-term safety. The present study provides a comprehensive assessment of the question how gas generation and transport in an L/ILW repository affects the system behaviour. A geological repository for L/ILW in the Opalinus Clay of Northern Switzerland with a depth of about 300-400 m below the surface was assumed. The results of model calculations were used to optimise the layout of the repository with respect to the effects of gas generation and transport. Specifically a design option was studied in which, by an appropriate choice of backfill and sealing materials, the gas can escape along the access ramp into the overlying rock formations without creating undue gas overpressures. The estimates of the gas generation rates are based on a waste inventory accounting for the existing nuclear power plants, with an assumed operation period of 50 years, and for wastes from medicine, industry and research with a collection period up to the year 2050. This inventory includes a total mass of approximately 40,000 tons of steel and other metals and about 2,200 tons of organic matter. Complete corrosion/degradation of all gas-generating materials yields a gas volume of approximately 20 to 30 million cubic meters (STP). The highest gas generation rates are expected in the early post-closure period up to several hundreds of years, followed by a steady decline. The expected total duration of the gas generation phase is in the order of 200,000 years. The total pore volume in the backfilled repository is in the order of 58,000 m 3

  7. Project Entsorgungsnachweis, 'Demonstration of disposal feasibility for SF/HLW/ILW in the Opalinus Clay of the Zuercher Weinland', Background, Objectives and Overview

    International Nuclear Information System (INIS)

    Schneider, Juerg; Zuidema, P.

    2004-01-01

    Juerg Schneider (Nagra, Switzerland) described the project on the Opalinus Clay (Project Entsorgungsnachweis, demonstration of disposal feasibility for SF/HLW/ILW in the Opalinus Clay of the Zuercher Weinland) for which the main objective is to demonstrate disposal feasibility and to provide input to the decision how to proceed. The report structure was described, the focus of the presentation being the report that aimed to provide a comprehensive assessment of long-term safety. The current situation was described in the presentation as follows: - The key need is to provide arguments for having proposed a good system for which there is sufficient understanding to allow a credible safety evaluation. - Alternative options exist, on which attention is maintained by a task-force. However, Nagra is confident in its results on Project Entsorgungsnachweis, given the knowledge base that currently exists, and has put forward a proposal, for consideration by the Swiss Government, to focus future work on the Opalinus Clay (OPA) of the Zuercher Weinland. - Making the safety case requires a proper integration of science, engineering and safety assessment. - Three key issues were identified in making a safety case: completeness, sufficient safety, and robustness to diminish the importance of uncertainties. - A safety case needs to be adequate to support a decision to proceed to the next stage in the programme, with multiple arguments including the existence of reserve FEP's. - The interacting functions of the relevant teams were viewed as a key component of the process of preparing a safety case: management; science; safety assessment; bias audit. During the discussion, the role of the bias team was recognised as being helpful to ensure completeness, as well as using the NEA FEP database as a check list. When speaking about sufficient safety, it should not imply predictive capability but rather that there is enough confidence in the current level of understanding to

  8. Performance of the Opalinus Clay under thermal loading: experimental results from Mont Terri rock laboratory (Switzerland)

    Energy Technology Data Exchange (ETDEWEB)

    Gens, A. [Universitat Politència de Catalunya, Barcelona (Spain); Wieczorek, K. [Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) GmbH, Braunschweig (Germany); Gaus, I. [National Cooperative for the Disposal of Radioactive Waste (NAGRA), Wettingen (Switzerland); and others

    2017-04-15

    The paper presents an overview of the behaviour of Opalinus Clay under thermal loading as observed in three in situ heating tests performed in the Mont Terri rock laboratory: HE-B, HE-D and HE-E. The three tests are summarily described; they encompass a broad range of test layouts and experimental conditions. Afterwards, the following topics are examined: determination of thermal conductivity, thermally-induced pore pressure generation and thermally-induced mechanical effects. The mechanisms underlying pore pressure generation and dissipation are discussed in detail and the relationship between rock damage and thermal loading is examined using an additional in situ test: SE-H. The paper concludes with an evaluation of the various thermo-hydro-mechanical (THM) interactions identified in the heating tests. (authors)

  9. Mont Terri Project - Ventilation experiment in Opalinus Clay for the disposal of radioactive waste in underground repositories

    Energy Technology Data Exchange (ETDEWEB)

    Mayor, J. C. [Empresa Nacional de Residuos Radioactivos SA (ENRESA), Madrid (Spain); Garcia-Sineriz, J. [Asociacion para la Investigacion y Desarollo Industrial de los Recursos Naturales (AITEMIN), Madrid (Spain); Velasco, M. [DM Iberia SA, Madrid (Spain); Gomez-Hernandez, J. [Ingenieria Hidraulica y Medio Ambiente, Escuela de Ingenieros de Caminos (UPV), Valencia (Spain); Lloret, A.; Matray, J.-M. [IRSN/DEI/SARG/LETS, Fontenay-aux-Roses (France); Coste, F. [Aradis ESG, Sevres Cedex (France); Giraud, A. [LAEGO-ENSG, Vandoeuvre les Nancy (France); Rothfuchs, T. [Gesellschaft fuer Anlagen und Reaktorsicherheit mbH (GRS), Braunschweig (Germany); Marschall, P. [National Cooperative for the Disposal of Radioactive Waste (Nagra), Wettingen (Switzerland); Roesli, U. [Solexperts AG, Moenchaltorf (Switzerland); Mayer, G. [Colenco Power Engineering Ltd, Baden (Switzerland)

    2007-07-01

    The ventilation of the underground drifts during the construction and operation of a radioactive waste repository could produce the partial desaturation of the rock around the drifts, modifying its thermo-hydro-mechanical properties, especially in clayey rocks. This change of rock properties may have an impact on the design of the repositories (drifts spacing and repository size), which depends on the thermal load that the clay barrier and the rock can accept. To evaluate 'in situ' and better understand the desaturation process of a hard clay formation, the Ventilation Experiment (VE) has been carried out at the Mont Terri underground laboratory (Switzerland), generating a flow of dry air during several months along a section of a microtunnel. Specifically, the VE test has been performed, under practically isothermal conditions (T {approx_equal} 15-16 {sup o}C), in a 10 m long section of a non-lined horizontal microtunnel (diameter = 1.3 m), excavated in 1999 in the shaly facies of the Opalinus Clay of Mont Terri. The microtunnel is oriented perpendicular to the bedding strike direction of the rock (mean value of the bedding dip {approx_equal} 25{sup o}). The VE experiment real data and its modelling have shown that the desaturation of clayey rocks of low hydraulic conductivity (K < 10{sup -12} m/s) due to ventilation is very small. Under real repository conditions, the thermal and hydro-mechanical rock characteristics will not be practically affected by the ventilation. Specifically, the monitoring of the VE test (mainly the hygrometer data, confirmed also by the geoelectrical measurements) indicates that, after about 5 months of ventilation with almost dry air, the rock relative humidity (and then the degree of saturation) was less than 95% only in a ring of thickness less than 40 cm. Nevertheless, a suction state (subatmospheric liquid pressures) developed up to a distance of about 2 m, but it should be kept in mind that a clayey rock such as the

  10. Mont Terri Project - Ventilation experiment in Opalinus Clay for the disposal of radioactive waste in underground repositories

    International Nuclear Information System (INIS)

    Mayor, J. C.; Garcia-Sineriz, J.; Velasco, M.; Gomez-Hernandez, J.; Lloret, A.; Matray, J.-M.; Coste, F.; Giraud, A.; Rothfuchs, T.; Marschall, P.; Roesli, U.; Mayer, G.

    2007-01-01

    The ventilation of the underground drifts during the construction and operation of a radioactive waste repository could produce the partial desaturation of the rock around the drifts, modifying its thermo-hydro-mechanical properties, especially in clayey rocks. This change of rock properties may have an impact on the design of the repositories (drifts spacing and repository size), which depends on the thermal load that the clay barrier and the rock can accept. To evaluate 'in situ' and better understand the desaturation process of a hard clay formation, the Ventilation Experiment (VE) has been carried out at the Mont Terri underground laboratory (Switzerland), generating a flow of dry air during several months along a section of a microtunnel. Specifically, the VE test has been performed, under practically isothermal conditions (T ≅ 15-16 o C), in a 10 m long section of a non-lined horizontal microtunnel (diameter = 1.3 m), excavated in 1999 in the shaly facies of the Opalinus Clay of Mont Terri. The microtunnel is oriented perpendicular to the bedding strike direction of the rock (mean value of the bedding dip ≅ 25 o ). The VE experiment real data and its modelling have shown that the desaturation of clayey rocks of low hydraulic conductivity (K -12 m/s) due to ventilation is very small. Under real repository conditions, the thermal and hydro-mechanical rock characteristics will not be practically affected by the ventilation. Specifically, the monitoring of the VE test (mainly the hygrometer data, confirmed also by the geoelectrical measurements) indicates that, after about 5 months of ventilation with almost dry air, the rock relative humidity (and then the degree of saturation) was less than 95% only in a ring of thickness less than 40 cm. Nevertheless, a suction state (subatmospheric liquid pressures) developed up to a distance of about 2 m, but it should be kept in mind that a clayey rock such as the Opalinus Clay is quasi-saturated for suction values up

  11. The safety case for a HLW repository in Opalinus clay: aims, methodology, first results

    International Nuclear Information System (INIS)

    Zuidema, Piet

    2002-01-01

    Piet Zuidema (Nagra, Switzerland) described the development of the safety case for a high level waste repository in Opalinus clay in which canisters would be placed in large vaults. The current phase of work was concerned with demonstrating the feasibility of the disposal concept. The Safety Case is taken to mean a set of arguments to support a statement that the proposed facility will meet relevant safety criteria and will include arguments giving the basis for confidence that those arguments are correct and properly taking account of uncertainties. The safety strategy was concerned both with the inherent robustness of the disposal concept and the adequacy of the assessment capability. As regards the former, the arguments being advanced were primarily qualitative. Key issues in terms of the documentation of the Safety Case were traceability and transparency of information, including how to ensure that key arguments did not become obscured because of the need to make available very large quantities of information

  12. Speciation of plutonium during sorption and diffusion in Opalinus clay

    International Nuclear Information System (INIS)

    Kaplan, Ugras

    2013-01-01

    The presented work was carried out in the framework of the BMWi-project ''Interaction and migration of actinides in natural clay rocks taking into account humic substances and clay organic matter - Interactions of neptunium and plutonium with natural clay rocks''. For the long-term safety assessments of nuclear repositories, the possible migration of the radiotoxic wastes into the environment must be considered. Due to its long half-life (T 1/2 = 24000 y) 239 Pu has a significant contribution to the radiotoxicity of spent nuclear fuel in a repository after long periods of storage. The redox-sensitive plutonium has a very complicated chemical behavior. In aqueous solution under environmental relevant conditions Pu can exist in oxidation states +III to +VI and it can exist in up to four oxidation states simultaneously in a solution. Clays are considered as a possible host rock formation for of high-level radioactive waste disposal. Therefore, detailed information on the mobilization and immobilization of plutonium through / into the groundwater from a repository are of special interest. In this work new insights into the interaction between Pu and natural Opalinus clay (OPA, Mont Terri, Switzerland) are obtained with regard to the disposal of heat-generating radioactive waste in a deep geological repository.rnThe focus of this work was on the determination of the speciation of Pu on the mineral surface after sorption and diffusion process by different synchrotron based techniques (μ-XRF, μ-XANES/-EXAFS, μ-XRD, and EXAFS/XANES). The interaction between Pu and OPA was studied in batch sorption and diffusion experiments in dependence of various experimental parameters (e.g. pH, Pu oxidation state). Sorption experiments showed that some experimental parameters (e.g. temperature, humic acid) have a significant impact on the sorption of Pu on OPA. Speciation studies were performed as a function of various chemical parameters on powder samples form batch experiments as

  13. Monitoring water content in Opalinus Clay within the FE-Experiment: Test application of dielectric water content sensors

    Science.gov (United States)

    Sakaki, T.; Vogt, T.; Komatsu, M.; Müller, H. R.

    2013-12-01

    The spatiotemporal variation of water content in the near field rock around repository tunnels for radioactive waste in clay formations is one of the essential quantities to be monitored for safety assessment in many waste disposal programs. Reliable measurements of water content are important not only for the understanding and prediction of coupled hydraulic-mechanic processes that occur during tunnel construction and ventilation phase, but also for the understanding of coupled thermal-hydraulic-mechanical (THM) processes that take place in the host rock during the post closure phase of a repository tunnel for spent fuel and high level radioactive waste (SF/HLW). The host rock of the Swiss disposal concept for SF/HLW is the Opalinus Clay formation (age of approx. 175 Million years). To better understand the THM effects in a full-scale heater-engineered barrier-rock system in Opalinus Clay, a full-scale heater test, namely the Full-Scale Emplacement (FE) experiment, was initiated in 2010 at the Mont Terri underground rock laboratory in north-western Switzerland. The experiment is designed to simulate the THM evolution of a SF/HLW repository tunnel based on the Swiss disposal concept in a realistic manner during the construction, emplacement, backfilling, and post-closure phases. The entire experiment implementation (in a 50 m long gallery with approx. 3 m diameter) as well as the post-closure THM evolution will be monitored using a network of several hundred sensors. The sensors will be distributed in the host rock, the tunnel lining, the engineered barrier, which consists of bentonite pellets and blocks, and on the heaters. The excavation is completed and the tunnel is currently being ventilated. Measuring water content in partially saturated clay-rich high-salinity rock with a deformable grain skeleton is challenging. Therefore, we use the ventilation phase (before backfilling and heating) to examine the applicability of commercial water content sensors and to

  14. Heater test in the Opalinus Clay of the Mont Terri URL. Gas release and water redistribution - Contribution to heater experiment (HE); Rock and bentonite thermo-hydro-mechanical (THM) processes in the nearfield

    International Nuclear Information System (INIS)

    Jockwer, N.; Wieczorek, K.

    2006-06-01

    Beside salt and granite, clay formations are investigated as potential host rocks for disposing radioactive waste. In Switzerland in the canton Jura close to the city of St. Ursanne, an underground laboratory was built in the vicinity of the reconnaissance gallery of a motorway tunnel. Since 1995, a consortium of 12 international organisations is running this laboratory for investigating the suitability of the Opalinus clay formation with regard to disposal of radioactive waste. In 1999, the Heater Experiment B (HE-B) was started for investigating the coupled thermo-hydro-mechanical (THM) processes of the Opalinus clay in interaction with the bentonite buffer. The principal contractors of this project were the Bundesanstalt fuer Geowissenschaften und Rohstoffe (BGR), the Empresa Nacional de Residuos Radiactivos S. A. (ENRESA), the Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH, and the National Cooperative for the Disposal of Radioactive Waste (NAGRA). GRS participated in that experiment for determining the subjects of gas generation, gas release, water content, and water redistribution in the Opalinus clay during heating. This was achieved by analysing gas and water samples from the test field before, during, and after the heating period and by performing geoelectric tomography measurements in the heated region. The in-situ measurements were supported by an additional laboratory programme. This report deals with the work of GRS performed in this project during the years 1999 to 2005. All the results obtained in the frame of the project are presented. Additional laboratory measurements conducted by the Pore Water Laboratory at CIEMAT in Madrid are also presented. The participation of GRS was funded by German Ministry of Economics and Labour (BMWA) under the contract No. 02 E 9602 and by the Commission of the European Communities under the contract No. FIKW.CT-2001-00132. (orig.)

  15. Effects of post-disposal gas generation in a repository for spent fuel, high-level waste and long-lived intermediate level waste sited in opalinus clay

    International Nuclear Information System (INIS)

    Johnson, L.; Marschall, P.; Zuidema, P.; Gribi, P.

    2004-07-01

    This comprehensive report issued by the Swiss National Cooperative for the Disposal of Radioactive Waste NAGRA takes a look at post-disposal gas generation in a repository for spent fuel and highly radioactive wastes in Opalinus clay strata. This study provides a comprehensive treatment of the issue of gas generation in a repository for spent fuel (SF), vitrified high-level waste (HLW) and long-lived intermediate-level waste (ILW), sited in the Opalinus clay of the Zuercher Weinland in northern Switzerland. The issue of how gas generation in and transport from waste repositories may influence disposal system performance has been under study for many years, both at Nagra and internationally. The report consists of three main parts: (i) A synthesis of basic information on the host rock and on details of repository construction; (ii) A discussion on gas transport characteristics of the engineered barrier system and the geosphere; (iii) A discussion on the effects of gas on system performance, based on the available information on gas generation, gas transport properties and gas pathways provided in the previous parts of the report. Simplified model calculations based on a mass balance approach for the gas generated within the repository are presented and discussed

  16. Clay as a barrier to radionuclide migration: a review

    International Nuclear Information System (INIS)

    Higgo, J.J.W.

    1986-05-01

    Because of their low permeability, high sorption capacity and plasticity, clay bodies are potentially suitable repositories for radioactive waste. The paper discusses the factors that influence radionuclide mobility in natural clay materials. Methods for determining radionuclide migration rates are described and compared. Data requirements necessary to establish whether or not a particular site is suitable for waste disposal are discussed. Suggestions are made as to the most important generic research that needs to be carried out. In the appendix, some of the most relevant, published, sorption and diffusion data are summarised and compared. (author)

  17. Coupled thermo-hydro-mechanical processes around a bentonite buffer embedded in Opalinus Clay - Comparison between measurements and calculations

    Energy Technology Data Exchange (ETDEWEB)

    Goebel, Ingeborg; Alheid, Hans-Joachim [BGR Hannover, Stilleweg 2, D-30655 Hannover (Germany); Jockwer, Norbert [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH, Theodor-Heuss-Str. 4, 38122 Braunschweig (Germany); Mayor, Juan Carlos [ENRESA, Emilio Vargas 7, E-Madrid (Spain); Garcia-Sineriz, Jose Luis [AITEMIN, c/ Alenza, 1 - 28003 Madrid (Spain); Alonso, Eduardo; Munoz, Juan Jorge [International Center for Numerical Methods in Engineering, CIMNE, Edificio C-1, Campus Norte UPC, C/Gran Capitan, s/n, 08034 Barcelona (Spain); Weber, Hans Peter [NAGRA, Hardstrasse 73, CH-5430 Wettingen (Switzerland); Ploetze, Michael [ETHZ, Eidgenoessische Technische Hochschule Zuerich, ETH Zentrum, HG Raemistrasse 101, CH-8092 Zuerich (Switzerland); Klubertanz, Georg [COLENCO Power Engineering Ltd, CPE, Taefern Str. 26, 5405 Baden-Daettwil (Switzerland); Ammon, Christian [Rothpletz, Lienhard, Cie AG, Schifflaendestrasse 35, 5001 Aarau (Switzerland)

    2004-07-01

    The Heater Experiment at the Mont Terri Underground Laboratory consists of an engineered barrier system composed of compacted bentonite blocks around a heater. The bentonite barrier is embedded in Opalinus Clay. The aim of the project is improved understanding of thermo-hydro mechanically (THM) coupled processes. Calculations are performed by 2 Finite-Element programs, CODE-BRIGHT and MHERLIN, the former for the near-field modeling and the latter for the rock modeling. Numerical modeling is carried out during all phases of the project to give input for design tasks such as cooling and dismantling, and to finally produce verified models of the THM coupled engineered barrier system. Results of both programs are discussed in the light of the experimental findings. (authors)

  18. Technetium migration in natural clays; Migration von Technetium in natuerlichem Tongestein

    Energy Technology Data Exchange (ETDEWEB)

    Luebke, Maria

    2015-10-01

    The present work was performed within the joint research project ''Retention of repository relevant radionuclides in argillaceous rocks and saline systems'' (contract no.: 02E10981), funded by the Federal Ministry for Economic Affairs and Energy (BMWi). The aim was to obtain first insights into the interaction of the long-lived fission product technetium and natural clay with regard to a repository for high-level nuclear waste. For this purpose Opalinus Clay from Mont Terri (northern Switzerland) was used as a reference material. The nuclide technetium-99 will contribute to the radiotoxicity of spent nuclear fuel for more than thousand years due to its long half-live. In case of a leakage of the storage vessels, the geochemistry of technetium is determined by its oxidation state, at which only the oxidation states +IV and +VII are relevant. Because of the high solubility and low affinity to sorption on surfaces of minerals, Tc(VII) is considered to be very mobile and thus the most hazardous species. The focuses of this study therefore are diffusion experiments with this mobile species and investigations of the effect of ferrous iron on the mobility and speciation of technetium.rnThe interaction of technetium and Opalinus Clay was studied in sorption and diffusion experiments varying several parameters (pH value, addition of reducing agents, effect of oxygen, diffusion pathways). In the course of this study spatially resolved investigations of the speciation have been performed on Opalinus Clay thin sections and bore cores for the first time. In addition to the speciation, further information regarding elemental distributions and crystalline phases near technetium enrichments were obtained. Supplementary investigations of powder samples allowed determining the molecular structure of technetium on the clay surface.rnBoth the combination of sorption experiments with spectroscopic investigations and the diffusion experiment exhibit a reduction of Tc

  19. Frictional Properties of Opalinus Clay: Implications for Nuclear Waste Storage

    Science.gov (United States)

    Orellana, L. F.; Scuderi, M. M.; Collettini, C.; Violay, M.

    2018-01-01

    The kaolinite-bearing Opalinus Clay (OPA) is the host rock proposed in Switzerland for disposal of radioactive waste. However, the presence of tectonic faults intersecting the OPA formation put the long-term safety performance of the underground repository into question due to the possibility of earthquakes triggered by fault instability. In this paper, we study the frictional properties of the OPA shale. To do that, we have carried out biaxial direct shear experiments under conditions typical of nuclear waste storage. We have performed velocity steps (1-300 μm/s) and slide-hold-slide tests (1-3,000 s) on simulated fault gouge at different normal stresses (4-30 MPa). To establish the deformation mechanisms, we have analyzed the microstructures of the sheared samples through scanning electron microscopy. Our results show that peak (μpeak) and steady state friction (μss) range from 0.21 to 0.52 and 0.14 to 0.39, respectively, thus suggesting that OPA fault gouges are weak. The velocity dependence of friction indicates a velocity strengthening regime, with the friction rate parameter (a - b) that decreases with normal stress. Finally, the zero healing values imply a lack of restrengthening during interseismic periods. Taken together, if OPA fault reactivates, our experimental evidence favors an aseismic slip behavior, making the nucleation of earthquakes difficult, and long-term weakness, resulting in stable fault creeping over geological times. Based on the results, our study confirms the seismic safety of the OPA formation for a nuclear waste repository.

  20. Geomechanical analysis of excavation-induced rock mass behavior of faulted Opalinus clay at the Mont Terri underground rock laboratory (Switzerland)

    International Nuclear Information System (INIS)

    Thoeny, R.

    2014-01-01

    Clay rock formations are potential host rocks for deep geological disposal of nuclear waste. However, they exhibit relatively low strength and brittle failure behaviour. Construction of underground openings in clay rocks may lead to the formation of an excavation damage zone (EDZ) in the near-field area of the tunnel. This has to be taken into account during risk assessment for waste-disposal facilities. To investigate the geomechanical processes associated with the rock mass response of faulted Opalinus Clay during tunnelling, a full-scale ‘mine-by’ experiment was carried out at the Mont Terri Underground Rock Laboratory (URL) in Switzerland. In the ‘mine-by’ experiment, fracture network characteristics within the experimental section were characterized prior to and after excavation by integrating structural data from geological mapping of the excavation surfaces and from four pre- and post-excavation boreholes.The displacements and deformations in the surrounding rock mass were measured using geo-technical instrumentation including borehole inclinometers, extensometers and deflectometers, together with high-resolution geodetic displacement measurements and laser scanning measurements on the excavation surfaces. Complementary data was gathered from structural and geophysical characterization of the surrounding rock mass. Geological and geophysical techniques were used to analyse the structural and kinematic relationships between the natural and excavation-induced fracture network surrounding the ‘mine-by’ experiment. Integrating the results from seismic refraction tomography, borehole logging, and tunnel surface mapping revealed that spatial variations in fault frequency along the tunnel axis alter the rock mass deformability and strength. Failure mechanisms, orientation and frequency of excavation-induced fractures are significantly influenced by tectonic faults. On the side walls, extensional fracturing tangential to the tunnel circumference was the

  1. Geomechanical analysis of excavation-induced rock mass behavior of faulted Opalinus clay at the Mont Terri underground rock laboratory (Switzerland)

    Energy Technology Data Exchange (ETDEWEB)

    Thoeny, R.

    2014-07-01

    Clay rock formations are potential host rocks for deep geological disposal of nuclear waste. However, they exhibit relatively low strength and brittle failure behaviour. Construction of underground openings in clay rocks may lead to the formation of an excavation damage zone (EDZ) in the near-field area of the tunnel. This has to be taken into account during risk assessment for waste-disposal facilities. To investigate the geomechanical processes associated with the rock mass response of faulted Opalinus Clay during tunnelling, a full-scale ‘mine-by’ experiment was carried out at the Mont Terri Underground Rock Laboratory (URL) in Switzerland. In the ‘mine-by’ experiment, fracture network characteristics within the experimental section were characterized prior to and after excavation by integrating structural data from geological mapping of the excavation surfaces and from four pre- and post-excavation boreholes.The displacements and deformations in the surrounding rock mass were measured using geo-technical instrumentation including borehole inclinometers, extensometers and deflectometers, together with high-resolution geodetic displacement measurements and laser scanning measurements on the excavation surfaces. Complementary data was gathered from structural and geophysical characterization of the surrounding rock mass. Geological and geophysical techniques were used to analyse the structural and kinematic relationships between the natural and excavation-induced fracture network surrounding the ‘mine-by’ experiment. Integrating the results from seismic refraction tomography, borehole logging, and tunnel surface mapping revealed that spatial variations in fault frequency along the tunnel axis alter the rock mass deformability and strength. Failure mechanisms, orientation and frequency of excavation-induced fractures are significantly influenced by tectonic faults. On the side walls, extensional fracturing tangential to the tunnel circumference was the

  2. Investigations of Near-Field Thermal-Hydrologic-Mechanical-Chemical Models for Radioactive Waste Disposal in Clay/Shale Rock

    Energy Technology Data Exchange (ETDEWEB)

    Liu, H.H.; Li, L.; Zheng, L.; Houseworth, J.E.; Rutqvist, J.

    2011-06-20

    Clay/shale has been considered as potential host rock for geological disposal of high-level radioactive waste throughout the world, because of its low permeability, low diffusion coefficient, high retention capacity for radionuclides, and capability to self-seal fractures. For example, Callovo-Oxfordian argillites at the Bure site, France (Fouche et al., 2004), Toarcian argillites at the Tournemire site, France (Patriarche et al., 2004), Opalinus Clay at the Mont Terri site, Switzerland (Meier et al., 2000), and Boom clay at the Mol site, Belgium (Barnichon and Volckaert, 2003) have all been under intensive scientific investigation (at both field and laboratory scales) for understanding a variety of rock properties and their relationships to flow and transport processes associated with geological disposal of radioactive waste. Figure 1-1 presents the distribution of clay/shale formations within the USA.

  3. Investigations of Near-Field Thermal-Hydrologic-Mechanical-Chemical Models for Radioactive Waste Disposal in Clay/Shale Rock

    International Nuclear Information System (INIS)

    Liu, H.H.; Li, L.; Zheng, L.; Houseworth, J.E.; Rutqvist, J.

    2011-01-01

    Clay/shale has been considered as potential host rock for geological disposal of high-level radioactive waste throughout the world, because of its low permeability, low diffusion coefficient, high retention capacity for radionuclides, and capability to self-seal fractures. For example, Callovo-Oxfordian argillites at the Bure site, France (Fouche et al., 2004), Toarcian argillites at the Tournemire site, France (Patriarche et al., 2004), Opalinus Clay at the Mont Terri site, Switzerland (Meier et al., 2000), and Boom clay at the Mol site, Belgium (Barnichon and Volckaert, 2003) have all been under intensive scientific investigation (at both field and laboratory scales) for understanding a variety of rock properties and their relationships to flow and transport processes associated with geological disposal of radioactive waste. Figure 1-1 presents the distribution of clay/shale formations within the USA.

  4. Hydro-mechanical analysis of results acquired by video-observations and deformation measurements performed in boreholes in the Opalinus clay of the URL Mont Terri supported by laboratory investigations on the hydro-mechanical behaviour of Opalinus clay

    International Nuclear Information System (INIS)

    Seeska, R.; Rutenberg, M.; Lux, K.H.

    2012-01-01

    Document available in extended abstract form only. Seven different boreholes in the Opalinus Clay formation of the Mont Terri Underground Rock Laboratory (URL Mont Terri) have been investigated by the Clausthal University of Technology (TUC) in cooperation with different partners with time, namely the National Cooperative for the Disposal of Radioactive Waste (NAGRA), the Federal Institute for Geosciences and Natural Resources (BGR) as well as the Swiss Federal Institute of Technology Zurich (ETHZ) and the Swiss Federal Nuclear Safety Inspectorate (ENSI). Aim of the investigations was to gain a large amount of high-quality and significant information on rock mass behaviour that can be used to increase knowledge about and improve understanding of time-dependent load-bearing and deformation behaviour of Opalinus Clay including pore water influences. For this purpose, an axial borehole camera and a three-arm calliper have been used. High-quality information on the load-bearing and deformation behaviour of the investigated boreholes was generated by the measurement and monitoring techniques used in the research project. The recordings reveal great as well as occasionally unexpected differences regarding the load-bearing behaviour as well as differences regarding the hydro-mechanical behaviour of the observed boreholes. While most of the boreholes have proved to be rather stable with only partial failure of the borehole wall in some areas, a complete borehole wall collapse occurred in two of the observed boreholes. The differences regarding the borehole wall stability and also the differences between the appearances of the occurring failure mechanisms are very likely due to the different orientation, the different locations within the URL Mont Terri, and the different facies the boreholes are located in. Figure 1 shows the time-dependent development of a borehole wall instability in one of the observed boreholes in a borehole section where an increase of moisture could

  5. Large scale laboratory diffusion experiments in clay rocks

    International Nuclear Information System (INIS)

    Garcia-Gutierrez, M.; Missana, T.; Mingarro, M.; Martin, P.L.; Cormenzana, J.L.

    2005-01-01

    ' experiments without any modification. The diffusion of neutral (HTO), anionic ( 36 Cl), and slightly sorbing ( 85 Sr) radionuclides in the Opalinus clay from Mont Terri (Switzerland) was studied using the proposed experimental set-up. (authors)

  6. Monitoring the Excavation Damaged Zone in Opalinus clay by three dimensional reconstruction of the electrical resistivity in the Mont Terri gallery G-04

    Science.gov (United States)

    Lesparre, N.; Adler, A.; Nicollin, F.; Gibert, D.; Nussbaum, C.

    2012-04-01

    The characteristics of opalinus clay have been studied in the last years for its capacity to retain radionuclide transport as a low permeable rock. This formation presents thereby suitable properties for hosting repository sites of radioactive waste. The Mont Terri underground rock laboratory (Switzerland) has been excavated in opalinus clay layer in order to develop experiences improving the knowledge on the physico-chemical properties of the rock. The study of electrical properties furnishes information on the rock structure, its anisotropy and the changes of these properties with time (Nicollin et al., 2010 ; Thovert et al., 2011). Here the three dimensional reconstruction of the electrical resistivity aims at monitoring the temporal evolution of the excavation damaged zone. Three rings of electrodes have been set-up around the gallery and voltage is measured between two electrodes while a current is injected between two others (Gibert et al., 2006). Measurements have been achieved from July 2004 until April 2008 before, during and after the excavation of the gallery 04. In this study we develop a computational approach to reconstruct three dimensional images of the resistivity in the vicinity of the electrodes. A finite element model is used to represent the complex geometry of the gallery. The measurements inferred from a given resistivity distribution are estimated using the software EIDORS (Adler and Lionheart, 2006), this constitutes the forward problem. The reconstruction of the media resistivity is then implemented by fitting the estimated to the measured data, via the resolution of an inverse problem. The parameters of this inverse problem are defined by mapping the forward problem elements into a coarser mesh. This allows to reduce drastically the number of unknowns and so increases the robustness of the inversion. The inversion is executed with the conjugate gradient method regularised by an analysis of the Jacobian singular values. The results show an

  7. Excavation induced damage evolution during a mine-by experiment in Opalinus Clay

    International Nuclear Information System (INIS)

    Vietor, T.; Armand, G.; Nyonoya, S.; Schuster, K.; Wieczorek, K.

    2010-01-01

    Document available in extended abstract form only. In Switzerland Opalinus Clay, a potential host rock formation for a nuclear waste repository, is intensively studied in the Mont Terri Underground Rock Laboratory (URL) in North-Western Switzerland. During the 2008 extension of the URL, the construction works were repeatedly interrupted to implement monitoring systems for a mine-by experiment. The future position of a 24 m long tunnel was instrumented with 36 different monitoring systems comprising approximately 200 sensors. Key features of this tunnel were chosen similar to the current Swiss concept for emplacement tunnels for High Level Radioactive Waste: circular section, full-face excavation following the geological bedding, support by a thin layer of shotcrete and 6 anchors every 1.3 m. For a mine-by experiment 26 boreholes were equipped with 7 multipoint extensometers, two multi segment inclinometer chains and 26 pore pressure chambers. The data acquisition system recorded 12 data sets per hour. For seismic transmission and acoustic emission monitoring, 8 piezo-electric emitters and 15 piezo-electric receivers were installed in 5 boreholes. The excavation of the instrumented tunnel took place in October/November 2008. The activities on the site were monitored with a web cam to separate spontaneous and excavation induced rock mass reactions. Daily mappings of the tunnel face and the sidewalls revealed the fracture pattern that was generated ahead of the advancing excavation. Three sets of excavation activated discontinuities could be clearly identified. These three sets develop within the framework of the pre-existing tectonic micro-faults that generally have a half-meter spacing. Where their density is high the intensity of excavation induced new slip planes apparently drops. Despite the presence of micro-faults the deformation monitoring around the advancing tunnel face showed a remarkably homogenous response to the excavation. Inclinometer chain segments

  8. Characterisation of gas transport properties of the Opalinus clay, a potential host rock formation for radioactive waste disposal; Caracterisation des proprietes des argiles d'Opalinus (roche d'accueil potentielle pour un stockage de dechets radioactifs) relatives au transport des gaz

    Energy Technology Data Exchange (ETDEWEB)

    Marschall, P. [Nagra - National Cooperative for the Disposal of Radioactive Waste, Wettingen (Switzerland); Horseman, S. [British Geological Survey, Kingsley Dunham Centre, Keyworth (United Kingdom); Gimmi, T. [Bern Univ. (Switzerland); Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    2005-07-01

    The Opalinus Clay in Northern Switzerland has been identified as a potential host rock formation for the disposal of radioactive waste. Comprehensive understanding of gas transport processes through this low-permeability formation forms a key issue in the assessment of repository performance. Field investigations and laboratory experiments suggest an intrinsic permeability of the Opalinus Clay in the order of 10{sup -20} to 10{sup -21} m{sup 2} and a moderate anisotropy ratio {<=} 10. Porosity depends on clay content and burial depth; values of {approx} 0.12 are reported for the region of interest. Porosimetry indicates that about 10-30% of voids can be classed as macro-pores, corresponding to an equivalent pore radius > 25 nm. The determined entry pressures are in the range of 0.4-10 MPa and exhibit a marked dependence on intrinsic permeability. Both in situ gas tests and gas permeameter tests on drill-cores demonstrate that gas transport through the rock is accompanied by pore water displacement, suggesting that classical flow concepts of immiscible displacement in porous media can be applied when the gas entry pressure (i.e. capillary threshold pressure) is less than the minimum principal stress acting within the rock. Essentially, the pore space accessible to gas flow is restricted to the network of connected macro-pores, which implies a very low degree of desaturation of the rock during the gas imbibition process. At elevated gas pressures (i.e. when gas pressure approaches the level of total stress that acts on the rock body), evidence was seen for dilatancy controlled gas transport mechanisms. Further field experiments were aimed at creating extended tensile fractures with high fracture transmissivity (hydro- or gas-fractures). The test results lead to the conclusion that gas fracturing can be largely ruled out as a risk for post-closure repository performance. (authors)

  9. Studying the migration behaviour of radionuclides in boom clay by electromigration

    Energy Technology Data Exchange (ETDEWEB)

    Norbert Maes, H.; Moors, H.; Dierckx, A.; Aertsens, M.; Wang, L.; Canniere, P. de; Put, M. [SCK-CEN, Belgian Nuclear Research Centre, Waste and Disposal - R and D Geological Disposal Mol (Belgium)

    2001-07-01

    Migration studies are an important part in the assessment of the performance of the Boom Clay Formation as a candidate for geological disposal of High-Level radwaste in Belgium. However, classical diffusion experiments take a long time because of the excellent retention characteristics of the Boom Clay. Electrical fields can be used to move ionic species. Especially for low permeability soils/sediments (such as clays), this driving force is far more efficient than a hydraulic gradient. As a consequence, the experimental time can be reduced drastically. This paper gives an overview on the quantitative and qualitative use of electromigration as a powerful technique to study radionuclides migration in clays. The enormous time gain in the determination of migration parameters for strongly retarded radionuclides as {sup 137}Cs{sup +} and {sup 226}Ra{sup 2+} is first demonstrated. Secondly, we want to demonstrate that electromigration has some useful features to study the behaviour of radionuclides with a more complex chemistry like the redox sensitive element uranium and Am-Organic Matter (OM) complexes. In the case of uranium, electromigration provides information on the speciation of the migrating species while for the Am-organic Matter complexes the role of OM as a possible carrier of actinides is investigated. (orig.)

  10. Studying the migration behaviour of radionuclides in boom clay by electromigration

    International Nuclear Information System (INIS)

    Norbert Maes, H.; Moors, H.; Dierckx, A.; Aertsens, M.; Wang, L.; Canniere, P. de; Put, M.

    2001-01-01

    Migration studies are an important part in the assessment of the performance of the Boom Clay Formation as a candidate for geological disposal of High-Level radwaste in Belgium. However, classical diffusion experiments take a long time because of the excellent retention characteristics of the Boom Clay. Electrical fields can be used to move ionic species. Especially for low permeability soils/sediments (such as clays), this driving force is far more efficient than a hydraulic gradient. As a consequence, the experimental time can be reduced drastically. This paper gives an overview on the quantitative and qualitative use of electromigration as a powerful technique to study radionuclides migration in clays. The enormous time gain in the determination of migration parameters for strongly retarded radionuclides as 137 Cs + and 226 Ra 2+ is first demonstrated. Secondly, we want to demonstrate that electromigration has some useful features to study the behaviour of radionuclides with a more complex chemistry like the redox sensitive element uranium and Am-Organic Matter (OM) complexes. In the case of uranium, electromigration provides information on the speciation of the migrating species while for the Am-organic Matter complexes the role of OM as a possible carrier of actinides is investigated. (orig.)

  11. Microbial analyses of clay and water from different samples from the Mont Terri Rock Laboratory (RL), Switzerland

    International Nuclear Information System (INIS)

    Sergeant, C.; Vesvres, M.H.; Barsotti, V.; Stroes-Gascoyne, S.; Hamon, C.J.; Neble, S.; Shippers, A.; Le Marrec, C.; Vinsot, A.; Schwyn, B.

    2010-01-01

    Document available in extended abstract form only. Exploration of deep subsurface microbial life has increased for very diverse motives. One of them is that these environments are potential host rocks for radioactive waste repositories and that microorganisms may influence geochemical conditions around such sites and migration properties of radionuclides. The pore water Chemistry experiment (PC) was conducted at the Mont Terri-RL to measure in situ the pH, Eh, and other geochemical parameters within the pore water of the Opalinus Clay formation. The borehole for PC was drilled with N 2 under clean but not aseptic conditions, filled immediately with synthetic pore water, which was circulated and monitored for five years. Soon after initiation of PC it was evident that microbial activity affected the borehole water geochemistry. Microbial analyses, including molecular biology and culturing methods, were performed repeatedly during PC (2003-2006), with detailed analysis of water and over-core clay upon termination in 2007. Results indicated the presence of heterotrophic aerobes and anaerobes, nitrate-reducers, iron-reducers, sulphate-reducers and Archaea, which together with geochemical data suggested a reducing environment with sulphate reduction in the water and adjacent clay. A black precipitate containing pyrite and a strong H 2 S smell confirmed the occurrence of sulphate reduction. Specific species identified (> 98% similarity) in PC water included Pseudomonas stutzeri, Bacillus licheniformis, and Desulfosporosinus sp., with similar and additional species (e.g., Trichococcus sp.; Koccuria sp.) in the clay. The origin of these (mostly anaerobic) species cannot be determined with certainty. Some species likely resulted from contamination, but others could be revived species indigenous in the Opalinus Clay. The microbial processes that occurred in PC are not representative of the processes in the undisturbed formation but illustrate the potential for microbial

  12. Transport of oxidants and radionuclides through a clay barrier

    International Nuclear Information System (INIS)

    Neretnieks, I.

    1978-02-01

    The masstransfer rate for oxidants to, and radionuclides from a capsule in a repository has been computed. The capsule which is 0.75 m in diameter is surrounded by Montmorillonite clay. The hole is 1.5 m in diameter. For one capsule about 1220g copper will corrode due to oxygen corrosion in 10 000 years. If the fissures in the rock nearest the hole are filled with clay, the corrosion will decrease significantly. This is valid for a case where the groundwater is in equilibrium with oxygen of 0.2 bar pressure (normal air pressure). Measurements of the oxygen content in groundwater at large depths show a more than 1 000 times smaller values. The transport rate will then be correspondingly smaller. Corrosion due to sulphate/sulphide corrosion may reach some 590 g in the same time if there is 10 mg/l of the least abundant component. The radionuclides Sr 90 , Cs 137 , Am 241 and Am 243 will decay totally in the clay barriers. Pu 240 will be seriously hindered. The total dissolution of the uranium oxide in a capsule takes at least 1.8 million years. Nuclides with high solubilities decrease in about 2 000 years to half their original concentration. The sodium in the Montmorillonite clay in the fissures is exchanged for calcium in about 20 000 years. The exchange of the sodium in the clay in the hole takes millions of years

  13. Diffusion of HTO, {sup 36}Cl{sup -}, {sup 125}I{sup -} and {sup 22}Na{sup +} in Opalinus Clay: Effect of Confining Pressure, Sample Orientation, Sample Depth and Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Van Loon, L.R.; Soler, J.M

    2004-02-01

    Effective diffusion coefficients (D{sub e}), rock capacity factors ({alpha}) and diffusion-accessible porosities ({epsilon}) were measured using the through-diffusion technique. Transport (diffusion) was measured both perpendicular and parallel to the bedding. Special cells that allowed the application of an axial confining pressure were designed. The pressures applied ranged from 1 to 5 MPa for Mont Terri samples and between 4 and 15 MPa for Benken samples, the upper values representing the in-situ confining pressure at both locations. The test solutions used in the experiments were synthetic Opalinus Clay pore water, which has Na and Cl as main components (Mont Terri: I = 0.39 M; Benken: I = 0.20 M). Pressure only had a small effect on the value of the effective diffusion coefficients. In the case of Mont Terri samples, increasing the pressure from 1 to 5 MPa resulted in a decrease of the effective diffusion coefficient of 20% for HTO, 27% for {sup 36}Cl{sup -}, 29% for {sup 125}I{sup -} and 17 % for {sup 22}Na{sup +}. In the case of Benken samples, increasing the pressure from 4 to 15 MPa resulted in a decrease of D{sub e} of 17% for HTO, 22% for {sup 36}Cl{sup -}, 32% for {sup 125}I{sup -} and 17 % for {sup 22}Na{sup +}. Moreover, the effective diffusion coefficients for for {sup 36}Cl{sup -}are smaller than for HTO, which is consistent with an effect arising from anion exclusion. This ion exclusion effect is smaller in samples from Mont Terri than in samples from Benken, which can be explained by the higher ionic strength of the Mont Terri water used in the experiments. The diffusion of {sup 22}Na{sup +} is similar to that of HTO in the case of Mont Terri OPA. For Benken OPA, the D{sub e} value of {sup 22}Na{sup +} is a factor of 2 higher than that of HTO. This last observation cannot be explained so far but is comparable to experimental data from ANDRA (1999) on Callovo-Oxfordian claystones from the Meuse/Haute Same site. {sup 125}I{sup -} is retarded with

  14. Mont Terri project, cyclic deformations in the Opalinus Clay

    International Nuclear Information System (INIS)

    Moeri, A.; Bossart, P.; Matray, J.M.; Mueller, H.; Frank, E.

    2010-01-01

    Document available in extended abstract form only. Shrinkage structures in the Opalinus Clay, related to seasonal changes in temperature and humidity, are observed on the tunnel walls of the Mont Terri Rock Laboratory. The structures open in winter, when relative humidity in the tunnel decreases to 65%. In summer the cracks close again because of the increase in the clay volume when higher humidity causes rock swelling. Shrinkage structures are monitored in the Mont Terri Rock Laboratory at two different sites within the undisturbed rock matrix and a major fault zone. The relative movements of the rock on both sides of the cracks are monitored in three directions and compared to the fluctuations in ambient relative humidity and temperature. The cyclic deformations (CD) experiment aims to quantify the variations in crack opening in relation to the evolution of climatic conditions and to identify the processes underlying these swell and shrinkage cycles. It consists of the following tasks: - Measuring and quantifying the long-term (now up to three yearly cycles) opening and closing and, if present, the associated shear displacements of selected shrinkage cracks along an undisturbed bedding plane as well as within a major fault zone ('Main Fault'). The measurements are accompanied by temperature and humidity records as well as by a long-term monitoring of tunnel convergence. - Analysing at the micro-scale the surfaces of the crack planes to identify potential relative movements, changes in the rock fabric on the crack surfaces and the formation of fault gouge material as observed in closed cracks. - Processing and analysing measured fluctuations of crack apertures and rock deformation in the time series as well as in the hydro-meteorological variables, in particular relative humidity Hr(t) and air temperature. - Studying and reconstructing the opening cycles on a drill-core sample under well-known laboratory conditions and observing potential propagation of

  15. Expertise on the provision of evidence with respect to Nagra's disposal concept for spent fuel assemblies, vitrified high-level radioactive waste as well as for long-living intermediate-level wastes (Opalinus clay project)

    International Nuclear Information System (INIS)

    2005-08-01

    Mankind has been living in a field of natural radiation; in Switzerland, the natural dose is around 3 mSv per year. It can be assumed that an artificial dose smaller than the natural one is harmless and can therefore be tolerated. However, nuclear power plants, medicine, industry and research produce radioactive wastes whose radioactivity is mostly higher than the natural level. These wastes must therefore be concentrated and enclosed until the decay reduces the dose rate to a harmless level. For this, it is foreseen that the radioactive wastes will be disposed of in deep-lying geological strata. The enclosure must be guarantied in such a way that, at any time, the radiation suffered by mankind and environment due to the radioactive wastes stays under the statutory limit of 1 mSv/a. The judgement of the quality of the deep underground repository is divided into 3 chapters: a) based on the geological and hydro-geological properties of the host rock, the proof of safety shows that the chosen repository site is safe for the long term; b) the proof of site guaranties that the repository needed can be built in the chosen host rock; c) the proof of implementation demonstrates that the repository can be built with the actual technical means proposed. The forecast for the development of the safety of the repository in the long term is fairly inaccurate, the most difficult factor being the developments in mankind's way of life. Therefore, conservative assumptions must be taken into account to cover even the most unlikely cases. The former project 'Gewaehr' presented by the National Co-operative for the Disposal of Nuclear Wastes (NAGRA) in 1978 was based on crystalline rock; it was rejected because it was not possible to find a sufficiently large area without geologic faults for the repository. In new investigations, NAGRA found a suitable layer of Opalinus clay in Zurich's Weinland. In the neighbourhood of the layer discovered, there are neither noticeable beds of other

  16. Biogeochemical processes in a clay formation in situ experiment: Part G - Key interpretations and conclusions. Implications for repository safety

    Energy Technology Data Exchange (ETDEWEB)

    Wersin, P., E-mail: paul.wersin@gruner.ch [NAGRA, Hardstrasse 73, 5430 Wettingen (Switzerland)] [Gruner Ltd., Gellertstrasse 55, 4020 Basel (Switzerland); Stroes-Gascoyne, S. [Atomic Energy of Canada Limited (AECL), Whiteshell Laboratories, Pinawa, Manitoba, Canada R0E 1L0 (Canada); Pearson, F.J. [Ground-Water Geochemistry, 5108 Trent Woods Drive, New Bern, NC 28562 (United States); Tournassat, C. [BRGM, French Geological Survey, 3 Avenue Claude Guillemin, B.P. 36009, 45060 Orleans Cedex 2 (France); Leupin, O.X.; Schwyn, B. [NAGRA, Hardstrasse 73, 5430 Wettingen (Switzerland)

    2011-06-15

    Highlights: > From the results of the PC experiment it can be inferred that degradation of organic compounds may induce. > Changes in pH and Eh which may affect the mobility of radionuclides eventually released from the waste. > Such changes will be limited in space and time because of large buffering capacity and low permeability of clay. > Nevertheless, amount of organic material in high level waste repositories should be kept small. > This will ensure achievement of background concentrations within short time period after repository closure. - Abstract: The in situ porewater chemistry (PC) experiment carried out in the Opalinus Clay formation at the Mont Terri Rock Laboratory, Switzerland for a period of 5 a allowed the identification and quantification of the biogeochemical processes resulting from and affected by an anaerobic microbial disturbance. The unintentional release of degradable organic compounds (mainly glycerol) induced microbially-mediated SO{sub 4} reduction in the borehole with concomitant significant geochemical changes in the circulating water and the adjacent porewater. These changes included a decrease in SO{sub 4}{sup 2-} concentration and pH and an increase in pCO{sub 2} and alkalinity relative to the non-affected formation water. However, the cation composition of the water and the mineralogy of the clay close to the borehole wall showed very little change. This is explained by (1) the strong chemical buffering processes in the clay and (2) by the diffusion-limited flux of solutes. With the aid of a reactive transport model with a minimum set of kinetic parameters for the hypothesised degradation reactions, the evolution of solutes in the borehole could be modelled adequately. The model was also applied to the prediction of restoration times upon depletion of the C source and results indicated restoration times to undisturbed conditions of about 15 a, but also highlighted the rather large uncertainties inherent in the geochemical model

  17. Radionuclide sorption studies on abyssal red clays

    International Nuclear Information System (INIS)

    Erickson, K.L.

    1979-01-01

    The radionuclide sorption properties of a widely distributed abyssal red clay are being experimentally investigated using batch equilibration techniques. This paper summarizes sorption equilibrium data obtained when 0.68 N NaCl solutions containing either Tc, U, Pu, Am or Cm were contacted with samples of the red clay and also summarizes some initial results from experiments designed to determine the relative selectivity of the clay for various nuclides. Under mildly oxidizing conditions, the sorption equilibrium distribution coefficients for technetium were essentially zero. At solution-phase nuclide concentrations on the order of 10 -6 M and less and at solution pH values of about 6.9, the distribution coefficients for plutonium were about 3 x 10 3 m1/gm and for uranium, americium, and curium were about 10 5 ml/gm or greater. However, at solution pH values of about 2.7, the distribution coefficients for each of the nuclides were greatly diminished. Initial experiments conducted in order to determine the relative selectivity of the clay for cesium, barium, and cerium, indicated that the silicate phases in the clay were selective for cesium over barium and cerium. These experiments also indicated that the hydrous oxide phases were selective for cerium over barium and for barium over cesium

  18. Field studies about radionuclide migration natural analogues and faults in clays

    International Nuclear Information System (INIS)

    Williams, G.M.; Hooker, P.J.; Brightman, M.A.

    1990-01-01

    This report puts together final reports of CEC contracts about the following topics: in situ determination of the effects of organics on the mobility of radionuclides in controlled conditions of groundwater flow (Drigg site); natural analogue studies of radionuclide migration (Loch Lomond, Broubster, Needle's Eye); faults in clays: their detection and characterization (Down Ampney site)

  19. Concrete - Opalinus clay interaction: in-situ experiment and technique for coring undisturbed interfaces

    International Nuclear Information System (INIS)

    Maeder, U.; Dolder, F.; Jenni, A.; Schwyn, B.; Frieg, B.; Eul, A.

    2012-01-01

    Document available in extended abstract form only. Designs for deep geologic disposal of radioactive waste foresee cementitious materials as structural elements, backfill or waste matrix. Interactions near interfaces are driven by chemical gradients in pore water and resultant diffusive transport, and are predicted to lead to mineralogical alterations in the barrier system, which in turn influences properties like swelling pressure, permeability, or specific retention in case of clay materials. Reactive transport modelling predictions and laboratory and in situ studies revealed significant alteration in both cement and clay-stone. An increase in porosity in the cement close to the interface, and clogging in the clay-stone adjacent to the interface is commonly predicted and observed. The Cement-Clay Interaction (CI) Experiment at the Mont Terri Underground Laboratory (St. Ursanne, Switzerland) aims at demonstrating some of the processes at interfaces to be expected at a realistic spatial scale and under saturated conditions. A duration of 20 years is foreseen during which reaction progress should become measurable and thus comparable to laboratory experiments and modelling predictions. Companion studies address cement hydration, and develop new high-resolution techniques for phase identification using μ-X-ray diffraction at the Paul Scherrer Institut. The field experiment at Mont Terri comprises two vertical boreholes (384 mm diameter, up to 9 m length) in Opalinus Clay (OPA) filled with layers of three different concretes and bentonite. The concrete formulations are based on three different binders: Portland cement (OPC), ESDRED cement designed for repository applications (40% of cement substituted by silica fume), and low alkali cement (LAC, containing slag and nano-silica). The characterisation of the three concrete-OPA interfaces after 2 years of alteration are presented in a companion contribution (Jenni et al.). A key issue is the repeat recovery of

  20. Modelling of natural organic matter-linked radionuclide transport in Boom clay

    International Nuclear Information System (INIS)

    Govaerts, J.; Maes, N.

    2012-01-01

    Document available in extended abstract form only. In the framework of the Belgian research program on long term management of high-level and/or long-lived radioactive wastes coordinated by ONDRAF/NIRAS, Boom Clay is investigated for its potential to host a deep geological disposal repository. In order to demonstrate the suitability of the Boom Clay as a host rock, the mobility of critical radionuclides in this clay layer has been the subject of research during many years. As actinides, lanthanides and transition metals are known to form strong complexes with organic substances, the influence of the Natural Organic Matter (NOM) present in Boom Clay on the mobility of these critical radionuclides is of crucial importance. Interaction of radionuclides with OM present in Boom Clay could on the one hand retard the migration due to complexation/colloid interaction with the immobile OM, and on the other hand the mobility and solubility of the radionuclide can be enhanced by the formation of complexes/colloids with the mobile OM. The conceptual understanding (and its numerical modelling) of the kinetic stability and transport of these complexes/colloids is therefore regarded as highly important for the the long-term safety assesment of the geological disposal. This can be broken down into two subproblems: 1. Describing the transport behaviour of mobile OM in Boom Clay; 2. Describing the interaction of RN with mobile OM and the transport behaviour of the resulting complexes in Boom Clay. The first part of this paper revolves around the first subproblem, where a robust model for the description of the migration behaviour of Natural Organic Matter (NOM) is derived based on data from column migration experiments using 14 C-labelled NOM Tracer solution, obtained in the framework of the EC TRANCOM-II project. Clay plugs of different lengths and different Darcy velocities were used. Inverse modelling with the MATLAB and COMSOL numerical code was done in order to identify the

  1. Anisotropic Diffusion In Layered Argillaceous Rocks: A Case Study With Opalinus Clay

    International Nuclear Information System (INIS)

    Van Loon, L.R.; Soler, J.; Mueller, W.; Bradbury, M.H.

    2003-01-01

    Anisotropic diffusion was studied in Opalinus Clay, a potential host rock for the disposal of spent fuel, vitrified high-level waste and intermediate-level waste. Diffusion parallel to the bedding was measured using a radial through-diffusion technique, while diffusion perpendicular to the bedding was measured using the classical (planar) through-diffusion method. The materials used were samples from Mont Terri (MT) and Benken (BE), respectively. Diffusion of Tritiated Water (HTO), parallel and perpendicular to the bedding, was studied under confining pressures of 7 MPa (MT) and 14 MPa (BE), respectively. The effective diffusion coefficient for diffusion parallel to the bedding, D e , was found to be 3.20(±0.26)x10 11 m 2 s -1 and for the Benken 5.39(±0.43)x10 -11 m 2 s-1 for the Mont Terri samples. The diffusion accessible porosity was ∼ 0.15(±0.02) in both cases. For diffusion perpendicular to the bedding, the effective diffusion coefficient was 5.44(±0.35)x10 -12 m 2 s-1 and 1.37(±0.08)x10 -11 m 2 s -1 for the Benken and Mont Terri samples, respectively. The diffusion accessible porosity was also ∼0.15(±0.02) in both cases. These first results indicate that diffusion parallel to bedding is larger than that perpendicular to the bedding by a factor of 4 to 6. This might be explained in terms of smaller path lengths (tortuosity) for species diffusing parallel to the fabric. (author)

  2. Anisotropic Diffusion In Layered Argillaceous Rocks: A Case Study With Opalinus Clay

    Energy Technology Data Exchange (ETDEWEB)

    Van Loon, L.R.; Soler, J.; Mueller, W.; Bradbury, M.H

    2003-03-01

    Anisotropic diffusion was studied in Opalinus Clay, a potential host rock for the disposal of spent fuel, vitrified high-level waste and intermediate-level waste. Diffusion parallel to the bedding was measured using a radial through-diffusion technique, while diffusion perpendicular to the bedding was measured using the classical (planar) through-diffusion method. The materials used were samples from Mont Terri (MT) and Benken (BE), respectively. Diffusion of Tritiated Water (HTO), parallel and perpendicular to the bedding, was studied under confining pressures of 7 MPa (MT) and 14 MPa (BE), respectively. The effective diffusion coefficient for diffusion parallel to the bedding, D{sub e}, was found to be 3.20({+-}0.26)x10{sup 11} m{sup 2}s{sup -1} and for the Benken 5.39({+-}0.43)x10{sup -11} m{sup 2}s-1 for the Mont Terri samples. The diffusion accessible porosity was {approx} 0.15({+-}0.02) in both cases. For diffusion perpendicular to the bedding, the effective diffusion coefficient was 5.44({+-}0.35)x10{sup -12} m{sup 2}s-1 and 1.37({+-}0.08)x10{sup -11} m{sup 2}s{sup -1} for the Benken and Mont Terri samples, respectively. The diffusion accessible porosity was also {approx}0.15({+-}0.02) in both cases. These first results indicate that diffusion parallel to bedding is larger than that perpendicular to the bedding by a factor of 4 to 6. This might be explained in terms of smaller path lengths (tortuosity) for species diffusing parallel to the fabric. (author)

  3. Sorption of neptunium(V) on opalinus clay under aerobic/anaerobic conditions

    International Nuclear Information System (INIS)

    Froehlich, D.R.; Amayri, S.; Drebert, J.; Reich, T.

    2011-01-01

    The interaction between neptunium(V) and a natural argillaceous rock (Opalinus Clay (OPA), Mont Terri, Switzerland) has been investigated in batch sorption experiments by varying pH (6-10), Np(V) concentration (10 -12 -10 -4 M), solid-to-liquid ratio (2-20 g/L), and partial pressure of CO 2 (10 -3.5 and 10 -2.3 atm) under aerobic/anaerobic conditions in saturated calcite solution. All batch experiments were carried out using well characterized aerobic and anaerobic dry powders of OPA. The results show a great influence of pH on Np(V) sorption. Under aerobic conditions sorption increases with increasing pH until maximum sorption is reached between pH 8-9. At pH > 9 sorption decreases due to the formation of negatively charged Np(V)-carbonate complexes. By increasing p CO 2 from 10 -3.5 to 10 -2.3 atm, the sorption edge is shifted ∼ 0.5 units to lower pH values. Under anaerobic conditions stronger sorption of 8 x 10 -6 M Np(V) was found, possibly due to partial reduction of Np(V) to Np(IV). The sorption of 8 x 10 -6 M Np(V) under aerobic conditions at pH 8.2 in saturated calcite solution increases continuously with increasing solid-to-liquid ratio of OPA in the range of 2-20 g/L with a constant K d value of 126 ± 13 L/kg. The sorption isotherm was measured over seven orders of magnitude in Np(V) concentration using 239 Np as tracer. The sorption isotherm could be divided in a part of linear sorption behaviour between 10 -13 -10 -9 M Np(V) and non-linear behaviour in the range of 10 -9 -10 -4 M Np(V). (orig.)

  4. Study of the Boom clay layer as a geochemical barrier for long-lived radionuclides

    International Nuclear Information System (INIS)

    Baetsle, L.H.; Henrion, P.; Put, M.; Cremers, A.

    1985-01-01

    The Boom clay layer below the nuclear site of Mol, Belgium has been thoroughly investigated on its geohydrologic and physicochemical characteristics as well as by laboratory experiments and in situ tests in the underground laboratory. Hydraulic permeabilities have been measured in situ; the chemical composition of the interstitial clay water is related to the mineralogical composition. Radionuclide sorption data and sorption mechanisms are given for Cs, Sr, Eu, Tc, Am, Pu and Np; experimental diffusion coefficients were determined by clay plug migration tests in representative conditions. Results of model calculations for the migration of radionuclides in dense porous media are given for Cs, Sr, Pu and Np

  5. Geochemical porosity values obtained in core samples from different clay-rocks

    International Nuclear Information System (INIS)

    Fernandez, A.M.

    2010-01-01

    Document available in extended abstract form only. Argillaceous formations of low permeability are considered in many countries as potential host rocks for the disposal of high level radioactive wastes (HLRW). In order to determine their suitability for waste disposal, evaluations of the hydro-geochemistry and transport mechanisms from such geologic formations to the biosphere must be undertaken. One of the key questions about radionuclide diffusion and retention is to know the chemistry and chemical reactions and sorption processes that will occur in the rock and their effects on radionuclide mobility. In this context, the knowledge of the pore water chemistry is essential for performance assessment purposes. This information allows to establish a reliable model for the main water-rock interactions, which control the physico-chemical parameters and the chemistry of the major elements of the system. An important issue in order to model the pore water chemistry in clayey media is to determine the respective volume accessible to cations and anions, i.e, the amount of water actually available for chemical reactions/solute transport. This amount is usually referred as accessible porosity or geochemical porosity. By using the anion inventories, i.e. the anion content obtained from aqueous leaching, and assuming that all Cl - , Br - and SO4 2- leached in the aqueous extracts originates from pore water, the concentration of a conservative ion can be converted into the real pore water concentration if the accessible porosity is known. In this work, the accessible porosity or geochemical porosity has been determined in core samples belonging to four different formations: Boom Clay from Hades URL (Belgium, BE), Opalinus Clay from Mont Terri (Switzerland, CH), and Callovo-Oxfordian argillite from Bure URL (France, FR). The geochemical or chloride porosity was defined as the ratio between the pore water volume containing Cl-bearing pore water and the total volume of a sample

  6. A review of materials and corrosion issues regarding canisters for disposal of spent fuel and high-level waste in Opalinus clay

    International Nuclear Information System (INIS)

    Landolt, D.; Davenport, A.; Payer, J.; Shoesmith, D.

    2009-01-01

    The project 'Entsorgungsnachweis' presented by NAGRA to the Swiss Federal Government in December 2002 assessed the feasibility of disposal of spent fuel (SF), vitrified high level waste (HLW) from reprocessing and long-lived intermediate level waste in an Opalinus Clay repository site in Northern Switzerland. NAGRA proposed the use of carbon steel canisters for disposal of SF/HLW and it also put forward an alternative concept of copper canisters with cast iron insert. In its reply the Federal Government acknowledged that NAGRA had successfully demonstrated the technical feasibility of disposal of SF/HLW. However, some of its experts raised a number of questions related to the choice of steel as canister material. Among others, it was questioned whether hydrogen formed by corrosion of steel in contact with saturated bentonite might adversely affect the barrier function of the Opalinus clay. It was also recommended that alternative canister materials and/or design concepts should be evaluated. To deal with these concerns NAGRA convened an international group of experts, the Canister Materials Review Board (CMRB), who were to review the existing information on canister materials that could be suitable for the proposed repository environment. Based on present knowledge of materials science, the CMRB was to recommend to NAGRA the most suitable material(s) for meeting the performance requirements for SF/HLW canisters. Specifically, the CMRB was to consider corrosion, including hydrogen generation, and stress-assisted failure processes that could affect the integrity and projected life time of SF/HLW canisters or impede the functioning of geological barriers while keeping in mind the overall feasibility of manufacturing, sealing and inspecting the canisters. The CMRB was further asked to identify the needs and provide advice for further studies by NAGRA on the long term performance and safety of SF/HLW canisters in the Swiss repository concept. For the assessment of the

  7. From clay bricks to deep underground storage

    International Nuclear Information System (INIS)

    2012-05-01

    This booklet issued by the Swiss National Cooperative for the Disposal of Radioactive Waste NAGRA takes a look at the use of clay strata for the storage of radioactive wastes in deep-lying repositories. First of all, a geological foray is made concerning the history of the use of clay and its multifarious uses. The characteristics of clay and its composition are examined and its formation in the geological past is explained. In particular Opalinus clay is looked at and the structures to be found are discussed. The clay's various properties and industrial uses are examined and its sealing properties are examined. Also, Bentonite clay is mentioned and work done by Nagra and co-researchers is noted

  8. Facts and features of radionuclide migration in Boom Clay

    International Nuclear Information System (INIS)

    De Regge, P.; Henrion, P.; Monsecour, M.; Put, M.

    1988-01-01

    The evolution which took place during ten years of research on the behaviour of radionuclides in Boom Clay is described. Initially, the Boom Clay was regarded as a chemically inert exchanger and the radiochemical research aimed at determining the distribution of cations between the clay and some liquid phases. The observation that Boom Clay deteriorates in contact with air and loses important intrinsic properties formed a major breakthrough in the research and led to a careful examination of the real in-situ conditions. Efforts devoted to the understanding of the chemical factors pertaining to the pH, the redox potential, the extent of the buffering capacity of FeS 2 and CaCO 3 in equilibrium with the interstitial aqueous phase are reviewed. Also emerging from the overall picture was the role of the organic material present in the Boom Clay. In contrast to the water percolating fractured formations which may not be in equilibrium with the rock, the interstitial aqueous phase is completely in equilibrium with Boom Clay mainly because of its low permeability and the large excesses of buffering components. As the retention mechanisms are better understood, a more coherent picture is obtained from distribution and diffusion experiments and the effects of consolidation are being investigated in detail. 23 refs.; 4 figs.; 3 tabs

  9. Constitutive relationships for elastic deformation of clay rock: Data Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Liu, H.H.; Rutqvist, J.; Birkholzer, J.T.

    2011-04-15

    Geological repositories have been considered a feasible option worldwide for storing high-level nuclear waste. Clay rock is one of the rock types under consideration for such purposes, because of its favorable features to prevent radionuclide transport from the repository. Coupled hydromechanical processes have an important impact on the performance of a clay repository, and establishing constitutive relationships for modeling such processes are essential. In this study, we propose several constitutive relationships for elastic deformation in indurated clay rocks based on three recently developed concepts. First, when applying Hooke's law in clay rocks, true strain (rock volume change divided by the current rock volume), rather than engineering strain (rock volume change divided by unstressed rock volume), should be used, except when the degree of deformation is very small. In the latter case, the two strains will be practically identical. Second, because of its inherent heterogeneity, clay rock can be divided into two parts, a hard part and a soft part, with the hard part subject to a relatively small degree of deformation compared with the soft part. Third, for swelling rock like clay, effective stress needs to be generalized to include an additional term resulting from the swelling process. To evaluate our theoretical development, we analyze uniaxial test data for core samples of Opalinus clay and laboratory measurements of single fractures within macro-cracked Callovo-Oxfordian argillite samples subject to both confinement and water reduced swelling. The results from this evaluation indicate that our constitutive relationships can adequately represent the data and explain the related observations.

  10. Constitutive relationships for elastic deformation of clay rock: Data Analysis

    International Nuclear Information System (INIS)

    Liu, H.H.; Rutqvist, J.; Birkholzer, J.T.

    2011-01-01

    Geological repositories have been considered a feasible option worldwide for storing high-level nuclear waste. Clay rock is one of the rock types under consideration for such purposes, because of its favorable features to prevent radionuclide transport from the repository. Coupled hydromechanical processes have an important impact on the performance of a clay repository, and establishing constitutive relationships for modeling such processes are essential. In this study, we propose several constitutive relationships for elastic deformation in indurated clay rocks based on three recently developed concepts. First, when applying Hooke's law in clay rocks, true strain (rock volume change divided by the current rock volume), rather than engineering strain (rock volume change divided by unstressed rock volume), should be used, except when the degree of deformation is very small. In the latter case, the two strains will be practically identical. Second, because of its inherent heterogeneity, clay rock can be divided into two parts, a hard part and a soft part, with the hard part subject to a relatively small degree of deformation compared with the soft part. Third, for swelling rock like clay, effective stress needs to be generalized to include an additional term resulting from the swelling process. To evaluate our theoretical development, we analyze uniaxial test data for core samples of Opalinus clay and laboratory measurements of single fractures within macro-cracked Callovo-Oxfordian argillite samples subject to both confinement and water reduced swelling. The results from this evaluation indicate that our constitutive relationships can adequately represent the data and explain the related observations.

  11. Radionuclide solubilities in boom clay. Final report, part 2 : a report produced for ONDRAF/NIRAS

    International Nuclear Information System (INIS)

    Baker, S.; Baston, G.M.N.; Boult, K.A.

    2000-01-01

    The release of radionuclides from a High Level Radioactive Waste repository situated in the Boom Clay at Mol would depend, in part, on their retardation within the Boom Clay. A number of parameters are required to assess such retardation; these include the solubilities of key radionuclides and their sorption behaviour. ONDRAF/NIRAS has identified neptunium, technetium, selenium, uranium and plutonium as elements for study. AEA Technology plc was requested to undertake a joint experimental and modelling study to determine the solubilities of these five elements under conditions representative of those in the Boom Clay (the in situ chemical conditions are pH∼8, Eh ∼ -230 mV). The work programme was carried out over three years, and for completeness this final report includes all the results

  12. Measurement of natural radionuclides in bricks and brick-making clays from Cuddalore district, Tamilnadu, India

    International Nuclear Information System (INIS)

    Viruthagirl, G.; Rajamanan, B.; Ravisankar, R.; Thilaivelavan, K.; Chandrasekaran, A.; Meenkshisundram, V.

    2010-01-01

    In India, bricks as building materials are mainly prepared by clay using the deposited sediments of rivers, and the radionuclide contents in bricks and brick-making clays should vary with origin and geological condition. In this paper, the radionuclide contents of these materials from river bank areas of Cuddalore district, Tamilnadu India are measured by gamma ray spectrometer using NaI (Tl) detector, and compared with those of other countries. The radiation hazard indices, which are evaluated by radium-equivalent (Raeq) activity, are lower than that of NEA-OECD. (authors)

  13. Using of clay-salt slimes of 'Belaruskali' factory as a sorbents of radionuclide

    International Nuclear Information System (INIS)

    Maskalchuk, L.

    2010-01-01

    Document available in extended abstract form only. The effective sorbents for decrease of radionuclide migration in soil and prevention of pollution risk of soil and underground water by radionuclide, according to available practical experience on minimization of consequences of the Chernobyl NPP accident, are: clay minerals of layered structure of type 2:1, potash fertilizers for 137 Cs and potassium rocks for 90 Sr. The analysis of literary data shows, those there two base kinds of industrial waste are formed at sylvinite ore processing almost at all potassium plants of the world: - Solid halite rejects material - Liquid waste in the form of clay-salt slimes. There is about 9 % of halite waste from annual formation using in Belarus, clay-salt slimes (CSS) are not used in general and all the volume goes to slime storage. Clay-salt slimes are the waste products of potassium production being formed in the course of sylvinite ore conversion at processing plants of the Industrial centre 'Belaruskali'. Up to the present moment about 80 millions of tones of clay-salt slimes have been accumulated in Soligorsk industrial zone, and their annual formation makes up about 2.0-2.5 millions of tones. The volume of industrial waste collected in Republic of Belarus allows considering CSS as a possible source of low-cost raw material for reception of products with different functions. On the other hand by estimation of national and international experts such quantity of industrial waste, especially liquid, represents ecological danger. Taking into account this circumstance the situation with industrial waste disposal in Soligorsk industrial area of Belarus which was estimated by international experts as critical one and it needs the cardinal measures for further environment pollution prevention. There is considerable volume of liquid radioactive waste is formed at the Nuclear Power Plant operation. Modern tendencies of radioactive waste disposal are directed on

  14. Joint project. Retention of radionuclides relevant for final disposal in natural clay rock and saline systems. Subproject 2. Geochemical behavior and transport of radionuclides in saline systems in the presence of repository-relevant organics. Final report

    International Nuclear Information System (INIS)

    Schmeide, Katja; Fritsch, Katharina; Lippold, Holger

    2016-01-01

    The objective of this project was to study the influence of increased salinities on interaction processes in the system radionuclide - organics - clay - aquifer. For this purpose, complexation, redox, sorption, and diffusion studies were performed under variation of the ionic strength (up to 4 mol kg -1 ) and the background electrolyte. The U(VI) complexation by propionate was studied in dependence on ionic strength (up to 4 mol kg -1 NaClO 4 ) by TRLFS, ATR FT-IR spectroscopy, and DFT calculations. An influence of ionic strength on stability constants was detected, depending on the charge of the respective complexes. The conditional stability constants, determined for 1:1, 1:2, and 1:3 complexes at specific ionic strengths, were extrapolated to zero ionic strength. The interaction of the bacteria Sporomusa sp. MT-2.99 and Paenibacillus sp. MT-2.2 cells, isolated from Opalinus Clay, with Pu was studied. The experiments can be divided into such without an electron donor where biosorption is favored and such with addition of Na-pyruvate as an electron donor stimulating also bioreduction processes. Moreover, experiments were performed to study the interactions of the halophilic archaeon Halobacterium noricense DSM-15987 with U(VI), Eu(III), and Cm(III) in 3 M NaCl solutions. Research for improving process understanding with respect to the mobility of multivalent metals in systems containing humic matter was focused on the reversibility of elementary processes and on their interaction. Kinetic stabilization processes in the dynamics of humate complexation equilibria were quantified in isotope exchange studies. The influence of high salinity on the mobilizing potential of humic-like clay organics was systematically investigated and was described by modeling. The sorption of Tc(VII)/Tc(IV) onto the iron(II)-containing minerals magnetite and siderite was studied by means of batch sorption experiments, ATR FT-IR and X-ray absorption spectroscopy. The strong Tc retention at

  15. Joint project. Retention of radionuclides relevant for final disposal in natural clay rock and saline systems. Subproject 2. Geochemical behavior and transport of radionuclides in saline systems in the presence of repository-relevant organics. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Schmeide, Katja; Fritsch, Katharina; Lippold, Holger [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Inst. of Ressource Ecology; and others

    2016-08-01

    The objective of this project was to study the influence of increased salinities on interaction processes in the system radionuclide - organics - clay - aquifer. For this purpose, complexation, redox, sorption, and diffusion studies were performed under variation of the ionic strength (up to 4 mol kg{sup -1}) and the background electrolyte. The U(VI) complexation by propionate was studied in dependence on ionic strength (up to 4 mol kg{sup -1} NaClO{sub 4}) by TRLFS, ATR FT-IR spectroscopy, and DFT calculations. An influence of ionic strength on stability constants was detected, depending on the charge of the respective complexes. The conditional stability constants, determined for 1:1, 1:2, and 1:3 complexes at specific ionic strengths, were extrapolated to zero ionic strength. The interaction of the bacteria Sporomusa sp. MT-2.99 and Paenibacillus sp. MT-2.2 cells, isolated from Opalinus Clay, with Pu was studied. The experiments can be divided into such without an electron donor where biosorption is favored and such with addition of Na-pyruvate as an electron donor stimulating also bioreduction processes. Moreover, experiments were performed to study the interactions of the halophilic archaeon Halobacterium noricense DSM-15987 with U(VI), Eu(III), and Cm(III) in 3 M NaCl solutions. Research for improving process understanding with respect to the mobility of multivalent metals in systems containing humic matter was focused on the reversibility of elementary processes and on their interaction. Kinetic stabilization processes in the dynamics of humate complexation equilibria were quantified in isotope exchange studies. The influence of high salinity on the mobilizing potential of humic-like clay organics was systematically investigated and was described by modeling. The sorption of Tc(VII)/Tc(IV) onto the iron(II)-containing minerals magnetite and siderite was studied by means of batch sorption experiments, ATR FT-IR and X-ray absorption spectroscopy. The strong Tc

  16. Natural gas extraction and artificial gas injection experiments in Opalinus Clay, Mont Terri rock laboratory (Switzerland)

    Energy Technology Data Exchange (ETDEWEB)

    Vinsot, A.; Lundy, M. [Agence Nationale pour la Gestion des Déchets Radioactifs ANDRA, Meuse Haute-Marne Center, Bure (France); Appelo, C.A.J. [Dr C.A.J. Appelo, Hydrochemical Consultant, Amsterdam (Netherlands); and others

    2017-04-15

    Two experiments have been installed at Mont Terri in 2004 and 2009 that allowed gas circulation within a borehole at a pressure between 1 and 2 bar. These experiments made it possible to observe the natural gases that were initially dissolved in pore-water degassing into the borehole and to monitor their content evolution in the borehole over several years. They also allowed for inert (He, Ne) and reactive (H{sub 2}) gases to be injected into the borehole with the aim either to determine their diffusion properties into the rock pore-water or to evaluate their removal reaction kinetics. The natural gases identified were CO{sub 2}, light alkanes, He, and more importantly N{sub 2}. The natural concentration of four gases in Opalinus Clay pore-water was evaluated at the experiment location: N{sub 2} 2.2 mmol/L ± 25%, CH{sub 4} 0.30 mmol/L ± 25%, C{sub 2}H{sub 6} 0.023 mmol/L ± 25%, C{sub 3}H{sub 8} 0.012 mmol/L ± 25%. Retention properties of methane, ethane, and propane were estimated. Ne injection tests helped to characterize rock diffusion properties regarding the dissolved inert gases. These experimental results are highly relevant towards evaluating how the fluid composition could possibly evolve in the drifts of a radioactive waste disposal facility. (authors)

  17. Radionuclide solubilities in boom clay. Final report, part 2 : a report produced for ONDRAF/NIRAS

    Energy Technology Data Exchange (ETDEWEB)

    Baker, S.; Baston, G.M.N.; Boult, K.A. [and others

    2000-07-01

    The release of radionuclides from a High Level Radioactive Waste repository situated in the Boom Clay at Mol would depend, in part, on their retardation within the Boom Clay. A number of parameters are required to assess such retardation; these include the solubilities of key radionuclides and their sorption behaviour. ONDRAF/NIRAS has identified neptunium, technetium, selenium, uranium and plutonium as elements for study. AEA Technology plc was requested to undertake a joint experimental and modelling study to determine the solubilities of these five elements under conditions representative of those in the Boom Clay (the in situ chemical conditions are pH{approx}8, Eh {approx} -230 mV). The work programme was carried out over three years, and for completeness this final report includes all the results.

  18. Excavation Induced Hydraulic Response of Opalinus Clay - Investigations of the FE-Experiment at the Mont Terri URL in Switzerland

    Science.gov (United States)

    Vogt, T.; Müller, H. R.; Garitte, B.; Sakaki, T.; Vietor, T.

    2013-12-01

    The Full-Scale Emplacement (FE) Experiment at the Mont Terri underground research laboratory in Switzerland is a full-scale heater test in a clay-rich formation (Opalinus Clay). Based on the Swiss disposal concept it simulates the construction, emplacement, backfilling, and post-closure thermo-hydro-mechanical (THM) evolution of a spent fuel / vitrified high-level waste (SF / HLW) repository tunnel in a realistic manner. The main aim of this experiment is to investigate SF / HLW repository-induced THM coupled effects mainly in the host rock but also in the engineered barrier system (EBS), which consists of bentonite pellets and blocks. A further aim is to gather experience with full-scale tunnel construction and associated hydro-mechanical (HM) processes in the host rock. The entire experiment implementation (in a 50 m long gallery with approx. 3 m diameter) as well as the post-closure THM evolution will be monitored using a network of several hundred sensors (state-of-the-art sensors and measurement systems as well as fiber-optic sensors). The sensors are distributed in the host rock's near- and far-field, the tunnel lining, the EBS, and on the heaters. The heater emplacement and backfilling has not started yet, therefore only the host rock instrumentation is installed at the moment and is currently generating data. We will present the instrumentation concept and rationale as well as the first monitoring results of the excavation and ventilation phase. In particular, we investigated the excavation induced hydraulic response of the host rock. Therefore, the spatiotemporal evolution of porewater-pressure time series was analyzed to get a better understanding of HM coupled processes during and after the excavation phase as well as the impact of anisotropic geomechanic and hydraulic properties of the clay-rich formation on its hydraulic behavior. Excavation related investigations were completed by means of inclinometer data to characterize the non-elastic and time

  19. Mont Terri rock laboratory, 20 years of research: introduction, site characteristics and overview of experiments

    International Nuclear Information System (INIS)

    Bossart, P.; Bernier, F.; Birkholzer, J.

    2017-01-01

    Geologic repositories for radioactive waste are designed as multi-barrier disposal systems that perform a number of functions including the long-term isolation and containment of waste from the human environment, and the attenuation of radionuclides released to the subsurface. The rock laboratory at Mont Terri (canton Jura, Switzerland) in the Opalinus Clay plays an important role in the development of such repositories. The experimental results gained in the last 20 years are used to study the possible evolution of a repository and investigate processes closely related to the safety functions of a repository hosted in a clay rock. At the same time, these experiments have increased our general knowledge of the complex behaviour of argillaceous formations in response to coupled hydrological, mechanical, thermal, chemical, and biological processes. After presenting the geological setting in and around the Mont Terri rock laboratory and an overview of the mineralogy and key properties of the Opalinus Clay, we give a brief overview of the key experiments that are described in more detail in the following research papers to this Special Issue of the Swiss Journal of Geosciences. These experiments aim to characterise the Opalinus Clay and estimate safety-relevant parameters, test procedures, and technologies for repository construction and waste emplacement. Other aspects covered are: bentonite buffer emplacement, high-pH concrete-clay interaction experiments, anaerobic steel corrosion with hydrogen formation, depletion of hydrogen by microbial activity, and finally, release of radionuclides into the bentonite buffer and the Opalinus Clay barrier. In the case of a spent fuel/high-level waste repository, the time considered in performance assessment for repository evolution is generally 1 million years, starting with a transient phase over the first 10,000 years and followed by an equilibrium phase. Experiments dealing with initial conditions, construction, and waste

  20. Mont Terri rock laboratory, 20 years of research: introduction, site characteristics and overview of experiments

    Energy Technology Data Exchange (ETDEWEB)

    Bossart, P. [Swisstopo, Federal Office of Topography, Wabern (Switzerland); Bernier, F. [Federal Agency for Nuclear Control FANC, Brussels (Belgium); Birkholzer, J. [Lawrence Berkeley National Laboratory, Berkeley (United States); and others

    2017-04-15

    Geologic repositories for radioactive waste are designed as multi-barrier disposal systems that perform a number of functions including the long-term isolation and containment of waste from the human environment, and the attenuation of radionuclides released to the subsurface. The rock laboratory at Mont Terri (canton Jura, Switzerland) in the Opalinus Clay plays an important role in the development of such repositories. The experimental results gained in the last 20 years are used to study the possible evolution of a repository and investigate processes closely related to the safety functions of a repository hosted in a clay rock. At the same time, these experiments have increased our general knowledge of the complex behaviour of argillaceous formations in response to coupled hydrological, mechanical, thermal, chemical, and biological processes. After presenting the geological setting in and around the Mont Terri rock laboratory and an overview of the mineralogy and key properties of the Opalinus Clay, we give a brief overview of the key experiments that are described in more detail in the following research papers to this Special Issue of the Swiss Journal of Geosciences. These experiments aim to characterise the Opalinus Clay and estimate safety-relevant parameters, test procedures, and technologies for repository construction and waste emplacement. Other aspects covered are: bentonite buffer emplacement, high-pH concrete-clay interaction experiments, anaerobic steel corrosion with hydrogen formation, depletion of hydrogen by microbial activity, and finally, release of radionuclides into the bentonite buffer and the Opalinus Clay barrier. In the case of a spent fuel/high-level waste repository, the time considered in performance assessment for repository evolution is generally 1 million years, starting with a transient phase over the first 10,000 years and followed by an equilibrium phase. Experiments dealing with initial conditions, construction, and waste

  1. Deformation mechanisms and evolution of the microstructure of gouge in the Main Fault in Opalinus Clay in the Mont Terri rock laboratory (CH)

    Science.gov (United States)

    Laurich, Ben; Urai, Janos L.; Vollmer, Christian; Nussbaum, Christophe

    2018-01-01

    We studied gouge from an upper-crustal, low-offset reverse fault in slightly overconsolidated claystone in the Mont Terri rock laboratory (Switzerland). The laboratory is designed to evaluate the suitability of the Opalinus Clay formation (OPA) to host a repository for radioactive waste. The gouge occurs in thin bands and lenses in the fault zone; it is darker in color and less fissile than the surrounding rock. It shows a matrix-based, P-foliated microfabric bordered and truncated by micrometer-thin shear zones consisting of aligned clay grains, as shown with broad-ion-beam scanning electron microscopy (BIB-SEM) and optical microscopy. Selected area electron diffraction based on transmission electron microscopy (TEM) shows evidence for randomly oriented nanometer-sized clay particles in the gouge matrix, surrounding larger elongated phyllosilicates with a strict P foliation. For the first time for the OPA, we report the occurrence of amorphous SiO2 grains within the gouge. Gouge has lower SEM-visible porosity and almost no calcite grains compared to the undeformed OPA. We present two hypotheses to explain the origin of gouge in the Main Fault: (i) authigenic generation consisting of fluid-mediated removal of calcite from the deforming OPA during shearing and (ii) clay smear consisting of mechanical smearing of calcite-poor (yet to be identified) source layers into the fault zone. Based on our data we prefer the first or a combination of both, but more work is needed to resolve this. Microstructures indicate a range of deformation mechanisms including solution-precipitation processes and a gouge that is weaker than the OPA because of the lower fraction of hard grains. For gouge, we infer a more rate-dependent frictional rheology than suggested from laboratory experiments on the undeformed OPA.

  2. A minimalistic microbial food web in an excavated deep subsurface clay rock.

    Science.gov (United States)

    Bagnoud, Alexandre; de Bruijn, Ino; Andersson, Anders F; Diomidis, Nikitas; Leupin, Olivier X; Schwyn, Bernhard; Bernier-Latmani, Rizlan

    2016-01-01

    Clay rocks are being considered for radioactive waste disposal, but relatively little is known about the impact of microbes on the long-term safety of geological repositories. Thus, a more complete understanding of microbial community structure and function in these environments would provide further detail for the evaluation of the safety of geological disposal of radioactive waste in clay rocks. It would also provide a unique glimpse into a poorly studied deep subsurface microbial ecosystem. Previous studies concluded that microorganisms were present in pristine Opalinus Clay, but inactive. In this work, we describe the microbial community and assess the metabolic activities taking place within borehole water. Metagenomic sequencing and genome-binning of a porewater sample containing suspended clay particles revealed a remarkably simple heterotrophic microbial community, fueled by sedimentary organic carbon, mainly composed of two organisms: a Pseudomonas sp. fermenting bacterium growing on organic macromolecules and releasing organic acids and H2, and a sulfate-reducing Peptococcaceae able to oxidize organic molecules to CO(2). In Opalinus Clay, this microbial system likely thrives where pore space allows it. In a repository, this may occur where the clay rock has been locally damaged by excavation or in engineered backfills. © FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  3. Radionuclide transport in the Neogene aquifer system located in the environment of the Boom clay

    International Nuclear Information System (INIS)

    Gedeon, M.; Marivoet, J.; Vandersteen, K.

    2012-01-01

    Document available in extended abstract form only. In the framework the Belgian research program on the long term management of high-level and/or long-lived radioactive waste coordinated by ONDRAF/NIRAS, the Boom Clay is considered as a reference host rock for the geological disposal of high-level radioactive waste in NE-Belgium (Campine area). In the frame of the performance assessments of a disposal system located in the Boom Clay Formation, the transport of radionuclides diffusing through the clay barrier into the aquifers located above is modelled. The transport model for the Neogene aquifer is based on a series of groundwater flow models simulating the aquifer systems in the surroundings of the Boom Clay. This series of groundwater models include the regional north-eastern Belgium model simulating flow both above and below the Boom Clay, the recently updated deep-aquifer pumping model, simulating transient flow in the over-exploited aquifers below the Boom Clay and finally the catchment-scale Neogene aquifer model, simulating flow in the aquifer system above the Boom Clay. The Neogene aquifer system consists of two main aquifers. The Pliocene aquifer is located at the top, separated from the underlying Miocene aquifer by the Kasterlee Clay aquitard. The Miocene aquifer consists of three hydrostratigraphic units: the Diest, Berchem and Voort Formations; with the last two having a lower hydraulic conductivity than the Diest unit. The transport model for the Neogene aquifer represents a fraction of the catchment-scale Neogene aquifer model. It stretches from the local divide between the Grote and Kleine Nete Rivers up to the Kleine Nete River, representing the main model sink. The boundary conditions and the sources/sinks in the Pliocene aquifer are defined mostly by the surface water features, such as the rivers, brooks, lakes and canals. In the partially confined Miocene aquifer, the effect of the surface water features is dampened and the heads at the model

  4. Microbiologically mediated processes in a repository sited in a clay host rock

    International Nuclear Information System (INIS)

    Schwyn, B.; Leupin, O. X.; Bagnoud, A.; Bernier-Latmani, R.

    2012-01-01

    Document available in extended abstract form only. Because of their favourable retention properties for radionuclides, clay-rich sediments are being considered in Switzerland as host rocks for the geological disposal of high, intermediate- and low-level radioactive waste. Compacted bentonite is foreseen as backfill material in the high level waste repository whereas for intermediate- and low-level waste the near field will mainly consist of cementitious material. The evolution of both types of repositories, which includes re-saturation, heat generation (only high level waste), near field degradation, gas production and radionuclide release may be impacted by microbial activity and vice versa. In this respect questions arise such as: - Are microorganisms present in a repository and its host rock? - Under which condition are microorganisms active in and around a repository? - In which processes are microorganisms involved? Various in situ experiments in a wide range of geological environments have evidenced the presence of microorganisms. Whether the microorganisms found in these in situ experiments are indigenous or introduced by drilling or/and excavation activities is still controversial. However, recent findings suggest the presence of indigenous microorganisms in Opalinus Clay. To conclusively answer the question about the origin of microorganisms, an international investigation programme has been launched to probe rock samples from the Underground Rock Laboratory at Mont Terri. So far, no metabolic activity has been observed in undisturbed clay rocks. Such activity may have ceased during diagenetic compaction of the sediment as suggested by the pore water composition measured in the Callovian-Oxfordian clayey formation of Bure (France). For the safety case of a repository the origin of microorganisms is of minor importance compared to the understanding of the conditions under which they might be metabolically active. Pore size distribution and connectivity can

  5. Considering clay rock heterogeneity in radionuclide retention

    International Nuclear Information System (INIS)

    Grambow, B.; Montavon, G.; Tournassat, C.; Giffaut, E.; Altmann, S.

    2010-01-01

    Document available in extended abstract form only. The Callovo-Oxfordian clay rock formation has a strong retention capacity for radionuclides, a favorable condition for the implementation of a nuclear waste repository. Principal retaining minerals are illite, and inter-stratified illite/smectite (I/S). Radionuclide retention has been studied on illite, illite/smectite and on clay rock obtained from different locations and data for retention on bentonite (80% smectite) are available. Sorption depends on the type of mineral, composition of mineralogical assemblages, individual mineral ion exchange capacities, ion distribution on exchange sites, specific surface areas, surface site types and densities for surface complexation as well as on water/rock ratios, temperature etc. As a consequence of mineralogical and textural variations, radionuclide retention properties are expected to vary with depth in the Callovo-Oxfordian formation. Using a simple additivity approach for the case of sorption of Cs and Ni it is shown that models and databases for illite and bentonite can be used to describe sorption in heterogeneous clay rock systems. A surface complexation/ion-exchange model as proposed by Bradbury and Baeyens without electrostatic contributions, was used directly as far as acid base properties are concerned but was modified with respect to sorption constants, in order to describe Na-, Ca, and Cs montmorillonite and bentonite MX-80 with a single set of surface complexation constants and also to account for carbonate and sulphate concentrations in groundwater. The model is integrated into the geochemical code PHREEQC considering dissolution/ precipitation/solubility constraints of accessory minerals (calcite, illite, celestite, quartz). Site densities for surface complexation and ion exchange are derived from the mass fractions of illite and of smectite in illite/smectite obtained from an overall fit of measured CEC data from all samples of the EST205 drill core

  6. Mont Terri Project - Engineered barrier emplacement experiment in Opalinus Clay for the disposal of radioactive waste in underground repositories

    International Nuclear Information System (INIS)

    Mayor, J. C.; Garcia-Sineriz, J.; Alonso, E.; Alheid, H.-J.; Bluemling, P.

    2007-01-01

    The Engineered Barrier (EB) experiment was a full-scale test for the demonstration, in a horizontal drift, of an emplacement technics of the clay barrier, using a granular bentonite material in the upper part of this barrier and bentonite blocks at the bottom. The test has been carried out in a 6 m long section of a niche excavated in Opalinus Clay of the Mont Terri underground laboratory. A steel dummy canister, with the same dimensions and weight as the real reference canisters, was placed on top of a bed of highly compacted bentonite blocks (in turn lying on a concrete bed), and the rest of the clay barrier volume was backfilled with a Granular Bentonite Material (GBM), made of very highly compacted pellets of different sizes. Hydro-mechanical instrumentation and an artificial hydration system (to accelerate the saturation of the clay barrier) were installed, and the test section sealed with a concrete plug. The evolution of the hydro-mechanical parameters along the hydration, both in the barrier and in the clayey rock formation, has been monitored during about 1.5 years, and modelled using the CODE-BRIGHT code. The EB experiment has proved that fully automated production of a Granular Bentonite Material (GBM) is possible and large quantities can be produced in due time in the required quality. Only minor modifications of existing production lines in industry for other applications were necessary to achieve this result. In the EB test section, a dry density of 1.36 g/cm 3 of the emplaced GBM has been obtained. With this value it is estimated that the hydraulic conductivity of this material is lower than 5 x 10 -12 m/s and the swelling pressure is about 1.3 MPa. Even though the EB test section conditions are now not considered as representative of a true demonstration, it is deemed that the model emplacement testing results (dry density of about 1.40 g/cm 3 ) serve well to demonstrate the achievable densities expected in the real world setting. The artificial

  7. Mont Terri Project - Engineered barrier emplacement experiment in Opalinus Clay for the disposal of radioactive waste in underground repositories

    Energy Technology Data Exchange (ETDEWEB)

    Mayor, J. C. [Empresa Nacional de Residuos Radioactivos SA (ENRESA), Madrid (Spain); Garcia-Sineriz, J. [Asociacion para la Investigacion y Desarollo Industrial de los Recursos Naturales (AITEMIN), Madrid (Spain); Alonso, E. [Centre Internacional de Metodos Numerics en Ingenyeria (CIMNE), Barcelona (Spain); Alheid, H.-J. [Bundesanstalt fuer Geowissenschaften und Rohstoffe (BGR), Hannover (Germany); Bluemling, P. [National Cooperative for the Disposal of Radioactive Waste (Nagra), Wettingen (Switzerland)

    2007-07-01

    The Engineered Barrier (EB) experiment was a full-scale test for the demonstration, in a horizontal drift, of an emplacement technics of the clay barrier, using a granular bentonite material in the upper part of this barrier and bentonite blocks at the bottom. The test has been carried out in a 6 m long section of a niche excavated in Opalinus Clay of the Mont Terri underground laboratory. A steel dummy canister, with the same dimensions and weight as the real reference canisters, was placed on top of a bed of highly compacted bentonite blocks (in turn lying on a concrete bed), and the rest of the clay barrier volume was backfilled with a Granular Bentonite Material (GBM), made of very highly compacted pellets of different sizes. Hydro-mechanical instrumentation and an artificial hydration system (to accelerate the saturation of the clay barrier) were installed, and the test section sealed with a concrete plug. The evolution of the hydro-mechanical parameters along the hydration, both in the barrier and in the clayey rock formation, has been monitored during about 1.5 years, and modelled using the CODE-BRIGHT code. The EB experiment has proved that fully automated production of a Granular Bentonite Material (GBM) is possible and large quantities can be produced in due time in the required quality. Only minor modifications of existing production lines in industry for other applications were necessary to achieve this result. In the EB test section, a dry density of 1.36 g/cm{sup 3} of the emplaced GBM has been obtained. With this value it is estimated that the hydraulic conductivity of this material is lower than 5 x 10{sup -12} m/s and the swelling pressure is about 1.3 MPa. Even though the EB test section conditions are now not considered as representative of a true demonstration, it is deemed that the model emplacement testing results (dry density of about 1.40 g/cm{sup 3}) serve well to demonstrate the achievable densities expected in the real world setting. The

  8. Radionuclides sorption in clay soils

    International Nuclear Information System (INIS)

    Siraky, G.; Lewis, C.; Hamlat, S.; Nollmann, C.E.

    1987-01-01

    The sorption behaviour of clay soils is examined through a parametric study of the distribution coefficient (Kd) for the radionuclides of interest, Cs and Sr. This work is a preliminary stage of the migration studies of these nuclides in a porous medium (ground of Ezeiza, Argentina) and the evaluation of radiologic impact of the removal of low and intermediate activity wastes in shallow trenches. The determination of Kd is performed by a static technique or batch. The phases are separated by centrifugation at 20000 g during 1 hour. The activity of supernatant solution of Cs-137 and Sr-85 is measured in a detecting system of I Na(Tl) well-type. Two types of parameters were changed: a) those related to the determination method: phase separation (centrifugation vs. centrifugation plus filtration); equilibrium period, ratio solid/liquid; b) those related to the geochemical system: pH of contact solution, carrier concentration, competitive ions, ionic strength, desorption. It was observed that the modification of parameters in the Kd-measurement does not change the order of magnitude of results. (Author)

  9. Applying squeezing technique to clay-rocks: lessons learned from ten years experiments at Mont Terri

    International Nuclear Information System (INIS)

    Fernandez, A. M.; Melon, A.; Sanchez-Ledesma, D.M.; Tournassat, C.; Gaucher, E.; Astudillo, J.; Vinsot, A.

    2012-01-01

    Document available in extended abstract form only. Argillaceous formations of low permeability are considered in several countries as potential host rocks for the disposal of high level radioactive wastes (HLRW). In order to determine their suitability for waste disposal, evaluations of the hydro-geochemistry and transport mechanisms from such geologic formations to the biosphere must be undertaken. The migration of radionuclides through the geosphere will occur predominantly in the aqueous phase, and hence the pore water chemistry plays an important role in determining ion diffusion characteristics in argillaceous formations. Consequently, a great effort has been made to characterise the pore water chemistry in clay-rocks formations. In the last 10 years various techniques were developed for determining pore water composition of clay-rocks including both direct and indirect methods: 1) In situ pore water sampling (water and gas) from sealed boreholes (Pearson et al., 2003; Vinsot et al. 2008); 2) Laboratory pore water sampling from unaltered core samples by the squeezing technique at high pressures (Fernandez et al., 2009); and 3) Characterization of the water chemistry by geochemical modelling (Gaucher et al. 2009). Pore water chemistry in clay-rocks and extraction techniques were documented and reviewed in different studies (Sacchi et al., 2001). Recovering pristine pore water from low permeable and low water content systems is very difficult and sometimes impossible. Besides, uncertainties are associated to each method used for the pore water characterization. In this paper, a review about the high pressure squeezing technique applied to indurate clay-rocks was performed. For this purpose, the experimental work on Opalinus Clay at the Mont Terri Research Laboratory during the last ten years was evaluated. A complete discussion was made about different issues such as: a) why is necessary to obtain the pore water by squeezing in the context of radioactive waste

  10. Ageing effect on deep-buried argillites stored after coring: study cases of Opalinus Clays and Callovo-Oxfordian argillites

    International Nuclear Information System (INIS)

    Techer, I.; Clauer, N.; Liewig, N.

    2010-01-01

    Document available in extended abstract form only. A petrophysical and geochemical study of deep-seated sediments requires either shaft excavation for in situ investigations or core drilling and storage for laboratory measurements and observations. In both cases, measured and observed data should be as representative as possible of the intrinsic characteristics of the rocks before human interference, which is especially critical for potential host-rocks of deep nuclear-waste storage. Almost instantaneous alteration processes were described due to interactions with the atmosphere by supply of O 2 , CO 2 , and water in some cases. Chemical exchanges and reactions were reported in conditioned and stored samples, despite all the care taken for treatment. The imprint of such processes remains to be very limited and therefore difficult to identify, especially by routine analyses. To provide further information about these limited modifications and to discuss the evolution of the geochemical records in deep clayed rocks when exposed to atmosphere, a coupled mineralogical and geochemical study was performed on two argillaceous rocks: the Opalinus Clays collected in the Mont-Terri URL (Switzerland) and the Callovo-Oxfordian Clays sampled in the Bure URL (France). A ∼8-m long core was drilled perpendicular to an experimental niche or gallery in each underground laboratory. Several core sections were selected as a function of distance to the wall of the niche/gallery and were analyzed repetitively relative to storage time. The samples were stored in Al-bags under vacuum, or not, and at ambient temperature or subjected to temperatures of 95 deg. C and 150 deg. C over varied periods of time, in order to enhance the reactions. The objective was the evaluation of the storage effect on the chemical and Sr isotopic compositions by leaching the rock powders with dilute acetic acid and analyzing the leachates for elemental and 87 Sr/ 86 Sr compositions. The study was complemented

  11. Sorption of radionuclides on London clay

    International Nuclear Information System (INIS)

    Berry, J.A.; Bourke, P.J.; Green, A.; Littleboy, A.K.

    1989-02-01

    Techniques for studying the sorption of radionuclides on London clay have been investigated. This work involved the use of through-diffusion, in-diffusion, high-pressure convection and batch methods to study the sorption of iodide, strontium, caesium and americium. Through-diffusion and high-pressure convection methods were found to be most useful for investigating weakly and moderately sorbing nuclides and give realistic values for sorptivity. The batch technique remains the most practical method of obtaining large quantities of data within a relatively short timescale but gives very high sorptivity values. It is however very useful for intercomparisons of nuclides or geological media. The in-diffusion method requires further refinement for use with strongly sorbing nuclides. Good agreement between through-diffusion and high-pressure convection methods was obtained for the sorptivity of strontium, whilst trends observed for caesium by through-diffusion were confirmed by batch measurements. (author)

  12. The geological evolution of opalinus clay in the Zurcher Weinland Area (ne Switzerland): learning from the past to predict future evolution and stability

    International Nuclear Information System (INIS)

    Gautschi, A.; Mazurek, M.

    2004-01-01

    A number of safety-relevant issues need to be addressed when considering long-term evolution of a radioactive waste repository, out of which uplift/erosion, fault activity, and changes in the geochemical and hydrogeological environment are particularly important. Among the strongest arguments in the prediction of future evolution is the extrapolation of events and processes that occurred over a long period of time in the geological past (e.g. 10 Ma) to a shorter period in the future. The future long-term evolution of Opalinus Clay in a potential siting area for a high-level waste repository in the Zurcher Weinland (NE Switzerland) is considered over a time period of around l Ma. The geological evolution or geological stability, respectively, can be predicted plausibly within reasonable limits over such a time period based on a detailed analysis of geological history. Predictions extending beyond this time period are feasible but contain an increasing element of uncertainty. This paper summarises the project-related conclusions, which are presented in greater detail in Nagra (2002a). (author)

  13. Modelling of radionuclide migration and heat transport from an High-Level-Radioactive-Waste-repository (HLW) in Boom clay

    International Nuclear Information System (INIS)

    Put, M.; Henrion, P.

    1992-01-01

    For the modelling of the migration of radionuclides in the Boom clay formation, the analytical code MICOF has been updated with a 3-dimensional analytical solution for discrete sources. the MICOF program is used for the calculation of the release of α and β emitters from the HIGH LEVEL RADIOACTIVE WASTES (HLW). A coherent conceptual model is developed which describes all the major physico-chemical phenomena influencing the migration of radionuclides in the Boom clay. The concept of the diffusion accessible porosity is introduced and included in the MICOF code. Different types of migration experiments are described with their advantages and disadvantages. The thermal impact of the HLW disposal in the stratified Boom clay formation has been evaluated by a finite element simulation of the coupled heat and mass transport equation. The results of the simulations show that under certain conditions thermal convection cells may form, but the convective heat transfer in the clay formation is negligible. 6 refs., 19 figs., 2 tabs., 5 appendices

  14. Association of actinides with microorganisms and clay: Implications for radionuclide migration from waste-repository sites

    International Nuclear Information System (INIS)

    Ohnuki, T.; Francis, A.; Kozai, N.; Sakamoto, F.; Ozaki, T.; Nankawa, T.; Suzuki, Y.

    2010-01-01

    We conducted a series of basic studies on the microbial accumulation of actinides to elucidate their migration behavior around backfill materials used in the geological disposal of radioactive wastes. We explored the interactions of U(VI) and Pu(VI) with Bacillus subtilis, kaolinite clay, and within a mixture of the two, directly analyzing their association with the bacterium in the mixture by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The accumulation of U by the mixture rose as the numbers of B. subtilis cells increased. Treating the kaolinite with potassium acetate (CH 3 COOK) removed approximately 80% of the associated uranium while only 65% was removed in the presence of B. subtilis. TEM-EDS analysis confirmed that most of the U taken from solution was associated with B. subtilis. XANES analyses revealed that the oxidation state of uranium associated with B. subtilis, kaolinite, and with the mixture containing both was U(VI). The amount of Pu sorbed by B. subtilis increased with time, but did not reach equilibrium in 48 h; in kaolinite alone, equilibrium was attained within 8 h. After 48 h, the oxidation state of Pu in the solutions exposed to B. subtilis and to the mixture had changed to Pu(V), whereas the oxidation state of the Pu associated with both was Pu(IV). In contrast, there was no change in the oxidation state of Pu in the solution nor on kaolinite after exposure to Pu(VI). SEM-EDS analysis indicated that most of the Pu in the mixture was associated with the bacteria. These results suggest that U(VI) and Pu(VI) preferentially are sorbed to bacterial cells in the presence of kaolinite clay, and that the mechanism of accumulation of U and Pu differs. U(VI) is sorbed directly to the bacterial cells, whereas Pu(VI) first is reduced to Pu(V) and then to Pu(IV), and the latter is associated with the cells. These results have important implications on the migrations of radionuclides around the repository sites of

  15. Expertise on the provision of evidence with respect to Nagra's disposal concept for spent fuel assemblies, vitrified high-level radioactive waste as well as for long-living intermediate-level wastes (Opalinus clay project); Gutachten zum Entsorgungsnachweis der Nagra fuer abgebrannte Brennelemente, verglaste hochaktive sowie langlebige mittelaktive Abfaelle (Projekt Opalinuston)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2005-08-15

    Mankind has been living in a field of natural radiation; in Switzerland, the natural dose is around 3 mSv per year. It can be assumed that an artificial dose smaller than the natural one is harmless and can therefore be tolerated. However, nuclear power plants, medicine, industry and research produce radioactive wastes whose radioactivity is mostly higher than the natural level. These wastes must therefore be concentrated and enclosed until the decay reduces the dose rate to a harmless level. For this, it is foreseen that the radioactive wastes will be disposed of in deep-lying geological strata. The enclosure must be guarantied in such a way that, at any time, the radiation suffered by mankind and environment due to the radioactive wastes stays under the statutory limit of 1 mSv/a. The judgement of the quality of the deep underground repository is divided into 3 chapters: a) based on the geological and hydro-geological properties of the host rock, the proof of safety shows that the chosen repository site is safe for the long term; b) the proof of site guaranties that the repository needed can be built in the chosen host rock; c) the proof of implementation demonstrates that the repository can be built with the actual technical means proposed. The forecast for the development of the safety of the repository in the long term is fairly inaccurate, the most difficult factor being the developments in mankind's way of life. Therefore, conservative assumptions must be taken into account to cover even the most unlikely cases. The former project 'Gewaehr' presented by the National Co-operative for the Disposal of Nuclear Wastes (NAGRA) in 1978 was based on crystalline rock; it was rejected because it was not possible to find a sufficiently large area without geologic faults for the repository. In new investigations, NAGRA found a suitable layer of Opalinus clay in Zurich's Weinland. In the neighbourhood of the layer discovered, there are neither

  16. Organic matter linked radionuclide transport in Boom clay - Phenomenological understanding and abstraction to PA

    International Nuclear Information System (INIS)

    Maes, N.; Bruggeman, C.; Liu, D.J.; Salah, S.; Van Laer, L.; Wang, L.; Weetjens, E.; Govaerts, J.; Marivoet, J.; Brassinnes, S.

    2012-01-01

    Document available in extended abstract form only. In the frame of the Belgian research program on long term management of high-level and/or long-lived radioactive wastes coordinated by ONDRAF/NIRAS, plastic clays (i.e., Boom Clay and Ypresian clays) are investigated for their potential to host a deep geological disposal repository for radioactive waste because of, among others, their ability to significantly retard radionuclide releases to the biosphere. The Boom Clay is characterised by the presence of a relatively high amount of dissolved organic matter (DOM, humic substances) which show a strong interaction with a suite of radionuclides (RN) like lanthanides, actinides and transition metals. This interaction with DOM leads in general to an increased mobility of the radionuclide as the OM can act as a colloidal carrier for the radionuclide. Therefore, the quantification and the understanding of the underlying processes are needed for the demonstration of confidence in the host formation to act as a suitable barrier. However, this is not an easy task, given the multitude of processes involved: complexation/colloid formation, sorption, kinetics, filtration, -. In this presentation, we will provide an overview of the research work that leads to a straightforward reactive transport model capturing fairly well the experimental observations. The model can be considered as an intermediate model providing a good basis for further safety abstraction on the one hand and the way to a more detailed phenomenological understanding on the other hand. The research is focussed on the underlying processes that govern speciation, sorption and transport. These underlying processes are investigated in a bottom-up approach, from simple systems to more complex systems. Interpretation is done using thermodynamic based models. Whereas the contribution of Bruggeman et al. focusses mainly on (batch) sorption studies (of trivalent RN), this presentation will provide more details on the

  17. Project Opalinus Clay: Radionuclide Concentration Limits in the Cementitious Near-Field of an ILW Repository

    International Nuclear Information System (INIS)

    Berner, U.

    2003-05-01

    The disposal feasibility study currently performed by Nagra includes a succession of quantitative models, aiming at describing the fate of radionuclides potentially escaping from the repository system. In this chain of models the present report provides the so called 'solubility limits' (maximum expected concentrations) for safety relevant radionuclides from ILW wastes, disposed of in a chemically reducing, cementitious environment. From a chemical point of view, the pore waters of hydrated cement matrices provide an exceptional environment. Compared with usual ground waters exhibiting pH-values of around 8, cement pore waters are strongly alkaline with pH-values from 12.5 to 13.5 and contain nearly no carbonate and only little sulfate. Oxides and hydroxides mainly determine solubility and speciation of the elements. Solubility and speciation calculations in cementitious pore waters were performed using the very recently updated Nagra/PSI Chemical Thermodynamic Data Base (TDB) for the majority of the 36 elements addressed as potentially relevant. Wherever possible, maximum concentrations compiled in this report were based on geochemical calculations. In order to ensure full traceability, all thermodynamic data not included in the TDB are explicitly specified in the document. For similar reasons the compilation of results (Table 1) clearly distinguishes between calculated and recommended items. The heading 'CALCULATED' lists maximum concentrations based on data fully documented in the TDB; results under the heading 'RECOMMENDED' include data from other sources. The pH sensitivity of the results was examined by performing calculations at pH 13.4, in accordance with the pH of non-altered cement pore water. Solubility increases predominantly for elements that tend to form anionic hydroxide complexes (Sn, Pd, Zr, Ni, Eu, Cd, Mo, Co). Oxidizing conditions around +350 mV might be expected in the environment of nitrate-containing wastes. In this case, significant

  18. Project Opalinus Clay: Radionuclide Concentration Limits in the Cementitious Near-Field of an ILW Repository

    Energy Technology Data Exchange (ETDEWEB)

    Berner, U

    2003-05-01

    The disposal feasibility study currently performed by Nagra includes a succession of quantitative models, aiming at describing the fate of radionuclides potentially escaping from the repository system. In this chain of models the present report provides the so called 'solubility limits' (maximum expected concentrations) for safety relevant radionuclides from ILW wastes, disposed of in a chemically reducing, cementitious environment. From a chemical point of view, the pore waters of hydrated cement matrices provide an exceptional environment. Compared with usual ground waters exhibiting pH-values of around 8, cement pore waters are strongly alkaline with pH-values from 12.5 to 13.5 and contain nearly no carbonate and only little sulfate. Oxides and hydroxides mainly determine solubility and speciation of the elements. Solubility and speciation calculations in cementitious pore waters were performed using the very recently updated Nagra/PSI Chemical Thermodynamic Data Base (TDB) for the majority of the 36 elements addressed as potentially relevant. Wherever possible, maximum concentrations compiled in this report were based on geochemical calculations. In order to ensure full traceability, all thermodynamic data not included in the TDB are explicitly specified in the document. For similar reasons the compilation of results (Table 1) clearly distinguishes between calculated and recommended items. The heading 'CALCULATED' lists maximum concentrations based on data fully documented in the TDB; results under the heading 'RECOMMENDED' include data from other sources. The pH sensitivity of the results was examined by performing calculations at pH 13.4, in accordance with the pH of non-altered cement pore water. Solubility increases predominantly for elements that tend to form anionic hydroxide complexes (Sn, Pd, Zr, Ni, Eu, Cd, Mo, Co). Oxidizing conditions around +350 mV might be expected in the environment of nitrate-containing wastes. In

  19. Interactions of radionuclides and CO2 with clays: elucidating mechanisms at nano-scale level

    International Nuclear Information System (INIS)

    Yang, Wei

    2014-01-01

    In order to predict and regulate the environmental impact of human activities such as uranium mining and radioactive waste disposal, it is necessary to understand the behavior of actinides in the environment because their interaction with clay mineral is an important factor to control the migration of radionuclide in the environment. The behavior of actinides in the soil is mainly the surface adsorption interactions, which change the forms of radioactive elements and reduces the mobility of actinides in the natural systems. Therefore, it is important to search how the actinides interact with clay mineral such as the fundamental process of surface precipitation. Uranium is the predominant heavy metal content of the final waste in the nuclear fuel cycle (≥95% UO 2 ). In addition, uranium is a major contaminant in the soil, subsurface and groundwater as a result of human activity. Under standard environmental conditions, the most stable chemical form of U(VI) is the uranyl ion UO 2 2+ , which is potentially very mobile and readily complexes with organic and inorganic matter. On the other hand, carbon dioxide is an important greenhouse gas, warming the earth's surface to a higher temperature by reducing outward radiation. However, problems may occur when the atmospheric concentration of greenhouse gases increases. Amounts of carbon dioxide were produced since the industrial revolution, which is behind the significant global warming and rising sea level. Clay minerals are of great practical importance here, in storage of carbon dioxide due to its hydraulic permeability and ability to retain mobile species. We have chosen kaolinite and montmorillonite as prototypes of clay minerals of 1:1 and 2:1. Classical Monte Carlo (MC) and molecular dynamics (MD) methods have been used in this work in order to understand the adsorption behaviour of radionuclide and carbon dioxide in clays surface. In this thesis, we will investigate first the adsorption of uranyl on kaolinite

  20. From clay bricks to deep underground storage; vom lehmziegel bis zum tiefenlager -- anwendung von ton

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2012-05-15

    This booklet issued by the Swiss National Cooperative for the Disposal of Radioactive Waste NAGRA takes a look at the use of clay strata for the storage of radioactive wastes in deep-lying repositories. First of all, a geological foray is made concerning the history of the use of clay and its multifarious uses. The characteristics of clay and its composition are examined and its formation in the geological past is explained. In particular Opalinus clay is looked at and the structures to be found are discussed. The clay's various properties and industrial uses are examined and its sealing properties are examined. Also, Bentonite clay is mentioned and work done by Nagra and co-researchers is noted.

  1. Multi-technical approach to characterize the dissolved organic matter from clay-stone

    International Nuclear Information System (INIS)

    Blanchart, Pascale; Michels, Raymond; Faure, Pierre; Parant, Stephane; Bruggeman, Christophe; De Craen, Mieke

    2012-01-01

    Document available in extended abstract form only. Currently, different clay formations (Boom Clay, Callovo-Oxfordian argilites, Opalinus Clay, Toarcian shales...) are studied as reference host rocks for methodological studies on the geological disposal of high-level and long-lived radioactive waste. While a significant effort is being done on the characterization of the mineral composition and the reactivity of the clays as barriers, the occurrence of organic matter, even in low proportion cannot be neglected. The organic matter appears as gas (C 1 -C 4 as identified in the Bure underground facilities), as solid (kerogen), as hydrocarbon liquids (free hydrocarbons within the kerogen or adsorbed on minerals) as well as in the aqueous phase (Dissolved Organic Matter - DOM). DOM raises specific interest, as it may have complexation properties towards metals and rare earth elements and is potentially mobile. Therefore, it is important to characterize the DOM as part of a study of feasibility of geological disposal. In this study, four host rocks were studied: - The Callovo-Oxfordian shales of Bure Underground Research Laboratory (Meuse, France); - The Opalinus Clay of Mont Terri Underground Research Laboratory (Switzerland); - The Toarcian shales of Tournemire (Aveyron, France); - The Boom Clay formation studied in The HADES Underground Research Laboratory (Mol, Belgium). Organic matter characteristics vary upon formation in terms of (i) origin (mainly marine type II; mixtures of marine type II and higher plants type III organic matter often poorly preserved), (ii) TOC contents, (iii) thermal maturity (for instance, Opalinus Clay and Toarcian shales are more mature and have poor oxygen content compare to Callovo-Oxfordian shales and Boom Clay). These differences in organic matter quality may have an influence on the quantity and the quality of DOM. The DOM of the rocks was isolated by Soxhlet extraction using pure water. A quantitative and qualitative multi

  2. Geochemical of clay formations : study of Spanish clay REFERENCE

    International Nuclear Information System (INIS)

    Turrero, M. J.; Pena, J.

    2003-01-01

    Clay rocks are investigated in different international research programs in order to assess its feasibility for the disposal of high level radioactive wastes. This is because different sepcific aspects: they have low hydraulic conductivity (10''-11-10''-15 m/s), a high sorption capacity, self-sealing capacity of facults and discontinuities and mechanical resistance. Several research programs on clay formations are aimed to study the chemistry of the groundwater and the water-rock reactions that control it: e. g. Boom Clay (Mol, Belgium), Oxford Clay /Harwell, United Kingdom), Toarcian Clay (Tournemire, France), Palfris formation (Wellenberg, Switzerland), Opalinus Clay (Bure, France). Based on these studies, considerable progress in the development of techniques for hydrologic, geochemical and hydrogeochemical characterization of mudstones has been accomplished (e. g. Beaufais et al. 1994, De Windt el al. 1998. Thury and Bossart 1999, Sacchi and Michelot 2000) with important advances in the knowledge of geochemical process in these materials (e. g. Reeder et al. 1993, Baeyens and Brandbury 1994, Beaucaire et al. 2000, Pearson et al., 2003).Furtermore, geochemical modeling is commonly used to simulate the evolution of water chemistry and to understand quantitatively the processes controlling the groundwater chemistry (e. g. Pearson et al. 1998, Tempel and Harrison 2000, Arcos et al., 2001). The work presented here is part of a research program funded by Enresa in the context of its R and D program. It is focused on the characterization of a clay formation (reference Argillaceous Formation, RAF) located within the Duero Basin (north-centralSpain). The characterisation of th ephysical properties,, fluid composition, mineralogy, water-rock reaction processes, geochemical modelling and sorption properties of the clays from the mentioned wells is the main purpose of this work. (Author)

  3. A preliminary study on titanium-clay interactions

    International Nuclear Information System (INIS)

    Wersin, P.; Grolimund, D.; Kumpulainen, S.; Brendle, J.; Snellman, M.

    2010-01-01

    bentonite, Opalinus Clay, Illite du Puy) were characterized by XAS. Preliminary results can be summarized as: (1) Natural clay materials contain significant but variable amounts of Ti. The standard purification procedure for bentonites to remove accessories does not or only barely removes Ti. (2) The Ti in the natural clays materials Rokle bentonite, Opalinus Clay, Illite du Puy occurs as microcrystalline TiO 2 (presumably as anatase). On the other hand, the Ti spectra in MX-80 suggest the presence of structural Ti in the smectite, but the evidence is not conclusive so far. (3) The exposure of purified MX-80 to titanium powder at room temperature within a period of five months did not lead to measurable additional Ti in the clay. This was even true for samples exposed to acidic or alkaline conditions where corrosion rates and solubility of Ti are known to be higher. Thereof, the following preliminary conclusions can be drawn: - The Ti content in natural bentonites is concentrated mainly in the so-called clay fraction. Ti occurs therein either as separate small TiO 2 particles (Rokle, Opalinus Clay, Illite du Puy) or as structural Ti. As indicated by the study of Karnland et al. (2006), the properties of natural bentonites are not affected by the presence of Ti. In that study, the bulk properties (swelling pressure, hydraulic conductivity) were very similar for the different bentonites containing variable Ti content, ranging from 0.1 to 4.8 weight % TiO 2 in the purified clay fractions. The transfer rates of Ti from the metallic source, even in reactive powder form, to the clay are very low and no enrichment above background concentrations after several months could be observed. In order to obtain measurable effects, both the corrosion process must be increased and the background concentration must be reduced. Tests with Ti-free clay material at increased temperature are still ongoing and will hopefully enable identification of reacted Ti species. (authors)

  4. Biogeochemical processes in a clay formation in situ experiment: Part B - Results from overcoring and evidence of strong buffering by the rock formation

    Energy Technology Data Exchange (ETDEWEB)

    Koroleva, M. [Institute of Geological Sciences, University of Bern, Baltzerstrasse 3, CH-3012 Bern (Switzerland); Lerouge, C. [BRGM, French Geological Survey, 3 Avenue Claude Guillemin, B.P. 36009, 45060 Orleans Cedex 2 (France); Maeder, U., E-mail: urs.maeder@geo.unibe.ch [Institute of Geological Sciences, University of Bern, Baltzerstrasse 3, CH-3012 Bern (Switzerland); Claret, F.; Gaucher, E. [BRGM, French Geological Survey, 3 Avenue Claude Guillemin, B.P. 36009, 45060 Orleans Cedex 2 (France)

    2011-06-15

    Highlights: > A 5-year in situ porewater chemistry experiment in Opalinus Clay was overcored and examined. > A microbial perturbation induced sulfate reduction, pH decrease and alkalinity / P{sub CO2} increase. > Changes to mineralogy, isotopic composition and bulk properties could not be detected. > Precipitation of Fe-sulfides and carbonate occurred at the interface of the test interval. > The chemical perturbation was effectively buffered by the claystone's large capacity. - Abstract: An in situ Porewater Chemistry (PC) experiment in the Opalinus Clay formation was carried out at the Mont Terri underground rock laboratory (Jura Mountains, Switzerland) for a period of 5 a. A traced water with a composition close to that expected in the formation was continuously circulated and monitored in a packed-off borehole to achieve diffusive equilibration. An unwanted microbial perturbation changed the water composition, characterized by reduction of SO{sub 4} combined with increasing sulfide, increasing alkalinity, decreasing pH and increasing P(CO{sub 2}). In contrast, the main cations (Na, Ca, Mg) remained remarkably constant during the experiment, thus indicating the strong buffering of the formation via cation and proton exchange as well as carbonate dissolution/precipitation reactions. After 5 a, the 4.5 m long vertical test interval was overcored and Opalinus Clay samples were analyzed along ca. 15 cm long radial profiles. The analytical investigations included mineralogy (XRD, SEM-EDX), bulk parameters (water content, density, C, S), cation exchange capacity and occupancy, aqueous leachates for Cl{sup -}, Br{sup -}, SO{sub 4}{sup 2-} and water and carbonate stable isotopes. Emphasis was put on best sample preparation and conservation techniques. Results show that the distribution of non-reactive tracers (Br{sup -} and {sup 2}H) follows the expected out/in-diffusion profiles compatible with the time-dependent boundary conditions in the test interval of the

  5. Near Field sorption Data Bases for Compacted MX-80 Bentonite for Performance Assessment of a High-Level Radioactive Waste Repository in Opalinus Clay Host Rock

    Energy Technology Data Exchange (ETDEWEB)

    Bradbury, M.; Baeyens, B

    2003-08-01

    Bentonites of various types and compacted forms are being investigated in many countries as backfill materials in high-level radioactive waste disposal concepts. Nagra is currently considering an Opalinus clay (OPA) formation in the Zuercher Weinland as a potential location for a high-level radioactive waste repository. A compacted MX-80 bentonite is foreseen as a potential backfill material. Performance assessment studies will be performed for this site and one of the requirements for such an assessment are sorption data bases (SDB) for the bentonite near-field. The purpose of this report is to describe the procedures used to develop the SDB. One of the pre-requisites for developing a SDB is a water chemistry for the compacted bentonite porewater. For a number of reasons mentioned in the report, and discussed in more detail elsewhere, this is not a straightforward task. There are considerable uncertainties associated with the major ion concentrations and in particular with the system pH and Eh. The MX-80 SDB was developed for a reference bentonite porewater (pH = 7.25) which was calculated using the reference OPA porewater. In addition, two further SDBs are presented for porewaters calculated at pH values of 6.9 and 7.9 corresponding to lower and upper bound values calculated for the range of groundwater compositions anticipated for the OPA host rock. 'In house' sorption isotherm data were measured for Cs(I), Ni(II), Eu(III), Th(IV), Se(IV) and 1(-1) on the 'as received' MX-80 material equilibrated with a simulated porewater composition. Complementary 'in house' sorption edge and isotherm measurements on conditioned Na/Ca montmorillonites were also available for many of these radionuclides. These data formed the core of the SDB. Nevertheless, some of the required sorption data still had to be obtained from the open literature. An important part of this report is concerned with describing selection procedures and the modifications

  6. Corrosion of carbon steel under anaerobic conditions in a repository for SF and HLW in Opalinus Clay. Technical report 08-12

    International Nuclear Information System (INIS)

    King, F.

    2008-10-01

    Nagra is considering carbon steel as one of the canister material options for the disposal of high level waste and spent fuel in a deep geological repository in Opalinus Clay. Following a brief period of aerobic conditions, the canister will be exposed to an anaerobic environment for much of its service life. Knowledge of the rate of anaerobic corrosion is important not only for estimating the canister lifetime but also for determining the rate of hydrogen generation. This report describes a critical review of the anaerobic corrosion behaviour of carbon steel under environmental conditions similar to those expected in the repository. The aims of the report are: 1. to recommend a (range of) long-term anaerobic corrosion rate(s) for carbon steel canisters, and 2. to justify the use of this rate in safety assessments based on a mechanistic understanding of the structure and properties of the protective corrosion product films. The review is based on selected studies from various national nuclear waste management programs, supplemented where appropriate with studies from other applications and with evidence from archaeological analogues. The corrosion rate of carbon steel decreases with time because of the formation of a protective surface film. There are differences in behaviour in bulk solution and in the presence of compacted bentonite. In bulk solution, the corrosion rate decreases to an apparent steady-state rate after a period of approximately six months, with a long-term rate of the order of 0.1 μm·.yr -1 . The surface film comprises a duplex structure, with a magnetite outer layer and a spinel-type inner layer. In compacted clay systems the rate of decrease in corrosion rate is slower, with steady state not being reached after several years of exposure. There is a significant body of evidence from apparently well-conducted experiments that indicate an anaerobic corrosion rate of the order of 1-2 μm·yr -1 in systems containing compacted clay and the

  7. Activation energies of the self-diffusion of HTO, 22Na+ and 36Cl- in a highly compacted argillaceous rock (Opalinus Clay)

    International Nuclear Information System (INIS)

    Loon, L.R. van; Mueller, W.; Iijima, K.

    2005-01-01

    The temperature dependence of the self-diffusion of HTO, 22 Na + and 36 Cl - in Opalinus Clay (OPA) was studied using a through-diffusion technique, in which the temperature was gradually increased in the steady state phase of the diffusion. The measurements were done on samples from two different geological locations. The dependence of the effective diffusion coefficient on temperature was found to be of an Arrhenius type in the temperature range between 0 and 70 deg. C. A slight difference between the two locations could be observed. The average value of the activation energy of the self-diffusion of HTO in OPA was 21.1 ± 1.6 kJ mol -1 , and 21.0 ± 3.5 and 19.4 ± 1.5 kJ mol -1 for 22 Na + and 36 Cl - , respectively. The measured values for HTO are slightly higher than the values found for the bulk liquid water (HTO: 18.8 ± 0.4 kJ mol -1 ). This indicates that the structure of the confined water in OPA might be slightly different from that of bulk liquid water. Also for Na + and Cl - , slightly higher values than in bulk liquid water (Na + : 18.4 kJ mol -1 ; Cl - : 17.4 kJ mol -1 ) were observed. The Stokes-Einstein relationship, based on the temperature dependency of the viscosity of bulk water, could not be used to describe the temperature dependence of the diffusion of HTO in OPA. This additionally indicates the slightly different structure of the pore water in OPA

  8. Study of Different Argillaceous Formations Performed in the Context of the FUNMIG project

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, A. M.; Melon, A.; Sanchez, D. M.; Gaucher, E.; Tournassat, C.; Altmann, S.C.; Vinsot, A.; Maes, N.; Craen, M. de; Leupin, O.; Wersin, P.; Astudillo, J.

    2010-07-01

    Argillaceous Rock Formations of low permeability have been selected in several countries as potential geological host rock for the disposal of high level radioactive wastes (HLRW). The general barrier function of the host rock is to retard and attenuate the migration of radionuclides to the biosphere, and the properties of clay minerals sustain this barrier functions. Nowadays, a number of Underground Research Laboratories (URL) have been constructed for a more in depth investigation of the indurated as well as plastic clay rock formations indifferent countries. The HADES under ground research facility (URF) was constructed at Mol (Belgium), where the Boom Clay formation is being studied as a reference host rock formation. The Opalinus Clay formation has been studied in the Mont Terri Rock Laboratory (Switzerland). The Callovo- Oxfordian clayrock is being characterised in the Meuse/Haute-Marne Site at Bure (France). The Boda Claystone is being analysed at Mecsek in Hungary. The knowledge on biogeochemical processes which affect the transport of radionuclides through the geosphere is a key parameter for the safety case of a HLRW repository, which was the aim of the EC Project FUNMIG: Fundamental Processes of Radionuclide Migration. The main factors controlling the mobility of the radionuclides are the chemistry of the pore water, the chemical reactions involving the radionuclides and the sorption processes on clay minerals. There fore, the pore water chemistry plays an important role in determining radionuclide migration characteristics in clay-rock formations. (Author)

  9. Sorption data bases for argillaceous rocks and bentonite for the provisional safety analyses for SGT-E2

    International Nuclear Information System (INIS)

    Baeyens, B.; Thoenen, T.; Bradbury, M. H.; Marques Fernandes, M.

    2014-11-01

    In Stage 1 of the Sectoral Plan for Deep Geological Repositories, four rock types have been identified as being suitable host rocks for a radioactive waste repository, namely, Opalinus Clay for a high-level (HLW) and a low- and intermediate-level (L/ILW) repository, and 'Brauner Dogger', Effingen Member and Helvetic Marls for a L/ILW repository. Sorption data bases (SDBs) for all of these host rocks are required for the provisional safety analyses, including all of the bounding porewater and mineralogical composition combinations. In addition, SDBs are needed for the rock formations lying below Opalinus Clay (lower confining units) and for the bentonite backfill in the HLW repository. In some previous work Bradbury et al. (2010) have described a methodology for developing sorption data bases for argillaceous rocks and compacted bentonite. The main factors influencing the sorption in such systems are the phyllosilicate mineral content, particular the 2:1 clay mineral content (illite/smectite/illite-smectite mixed layers) and the water chemistry which determines the radionuclide species in the aqueous phase. The source sorption data were taken predominantly from measurements on illite (or montmorillonite in the case of bentonite) and converted to the defined conditions in each system considered using a series of so called conversion factors to take into account differences in mineralogy, in pH and in radionuclide speciation. Finally, a Lab → Field conversion factor was applied to adapt sorption data measured in dispersed systems (batch experiments) to intact rock under in-situ conditions. This methodology to develop sorption data bases has been applied to the selected host rocks, lower confining units and compacted bentonite taking into account the mineralogical and porewater composition ranges defined. Confidence in the validity and correctness of this methodology has been built up through additional studies: (i) sorption values obtained in the manner

  10. Sorption data bases for argillaceous rocks and bentonite for the provisional safety analyses for SGT-E2

    Energy Technology Data Exchange (ETDEWEB)

    Baeyens, B.; Thoenen, T.; Bradbury, M. H.; Marques Fernandes, M.

    2014-11-15

    In Stage 1 of the Sectoral Plan for Deep Geological Repositories, four rock types have been identified as being suitable host rocks for a radioactive waste repository, namely, Opalinus Clay for a high-level (HLW) and a low- and intermediate-level (L/ILW) repository, and 'Brauner Dogger', Effingen Member and Helvetic Marls for a L/ILW repository. Sorption data bases (SDBs) for all of these host rocks are required for the provisional safety analyses, including all of the bounding porewater and mineralogical composition combinations. In addition, SDBs are needed for the rock formations lying below Opalinus Clay (lower confining units) and for the bentonite backfill in the HLW repository. In some previous work Bradbury et al. (2010) have described a methodology for developing sorption data bases for argillaceous rocks and compacted bentonite. The main factors influencing the sorption in such systems are the phyllosilicate mineral content, particular the 2:1 clay mineral content (illite/smectite/illite-smectite mixed layers) and the water chemistry which determines the radionuclide species in the aqueous phase. The source sorption data were taken predominantly from measurements on illite (or montmorillonite in the case of bentonite) and converted to the defined conditions in each system considered using a series of so called conversion factors to take into account differences in mineralogy, in pH and in radionuclide speciation. Finally, a Lab → Field conversion factor was applied to adapt sorption data measured in dispersed systems (batch experiments) to intact rock under in-situ conditions. This methodology to develop sorption data bases has been applied to the selected host rocks, lower confining units and compacted bentonite taking into account the mineralogical and porewater composition ranges defined. Confidence in the validity and correctness of this methodology has been built up through additional studies: (i) sorption values obtained in the manner

  11. Biogeochemical processes in a clay formation in situ experiment: Part F - Reactive transport modelling

    Energy Technology Data Exchange (ETDEWEB)

    Tournassat, Christophe, E-mail: c.tournassat@brgm.fr [BRGM, French Geological Survey, Orleans (France); Alt-Epping, Peter [Rock-Water Interaction Group, Institute of Geological Sciences, University of Bern (Switzerland); Gaucher, Eric C. [BRGM, French Geological Survey, Orleans (France); Gimmi, Thomas [Rock-Water Interaction Group, Institute of Geological Sciences, University of Bern (Switzerland)] [Laboratory for Waste Management, Paul Scherrer Institut, Villigen (Switzerland); Leupin, Olivier X. [NAGRA, CH-5430 Wettingen (Switzerland); Wersin, Paul [Gruner Ltd., CH-4020 Basel (Switzerland)

    2011-06-15

    Highlights: > Reactive transport modelling was used to simulate simultaneously solute transport, thermodynamic reactions, ion exchange and biodegradation during an in-situ experiment in a clay-rock formation. > Opalinus clay formation has a high buffering capacity in terms of chemical perturbations caused by bacterial activity. > Buffering capacity is mainly attributed to the carbonate system and to the reactivity of clay surfaces (cation exchange, pH buffering). - Abstract: Reactive transport modelling was used to simulate solute transport, thermodynamic reactions, ion exchange and biodegradation in the Porewater Chemistry (PC) experiment at the Mont Terri Rock Laboratory. Simulations show that the most important chemical processes controlling the fluid composition within the borehole and the surrounding formation during the experiment are ion exchange, biodegradation and dissolution/precipitation reactions involving pyrite and carbonate minerals. In contrast, thermodynamic mineral dissolution/precipitation reactions involving alumo-silicate minerals have little impact on the fluid composition on the time-scale of the experiment. With the accurate description of the initial chemical condition in the formation in combination with kinetic formulations describing the different stages of bacterial activities, it has been possible to reproduce the evolution of important system parameters, such as the pH, redox potential, total organic C, dissolved inorganic C and SO{sub 4} concentration. Leaching of glycerol from the pH-electrode may be the primary source of organic material that initiated bacterial growth, which caused the chemical perturbation in the borehole. Results from these simulations are consistent with data from the over-coring and demonstrate that the Opalinus Clay has a high buffering capacity in terms of chemical perturbations caused by bacterial activity. This buffering capacity can be attributed to the carbonate system as well as to the reactivity of

  12. Microorganisms in potential host rocks for geological disposal of nuclear waste and their interactions with radionuclides

    Energy Technology Data Exchange (ETDEWEB)

    Cherkouk, A.; Liebe, M.; Luetke, L.; Moll, H.; Stumpf, T. [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Inst. of Resource Ecology

    2015-07-01

    The long-term safety of nuclear waste in a deep geological repository is an important issue in our society. Microorganisms indigenous to potential host rocks are able to influence the oxidation state, speciation and therefore the mobility of radionuclides as well as gas generation or canister corrosion. Therefore, for the safety assessment of such a repository it is necessary to know which microorganisms are present in the potential host rocks (e.g. clay, salt) and if these microorganisms can influence the performance of a repository. Microbial diversity in potential host rocks for geological disposal of nuclear waste was analyzed by culture-independent molecular biological methods (e.g. 16S rRNA gene retrieval) as well as enrichment and isolation of indigenous microbes. Among other isolates, a Paenibacillus strain, as a representative of Firmicutes, was recovered in R2A media under anaerobic conditions from Opalinus clay from the Mont Terri in Switzerland. Accumulation experiments and potentiometric titrations showed a strong interaction of Paenibacillus sp. cells with U(VI) within a broad pH range (3-7). Additionally, the interactions of the halophilic archaeal strain Halobacterium noricense DSM 15987, a salt rock representative reference strain, with U(VI) at high ionic strength was investigated. After 48 h the cells were still alive at uranium concentrations up to 60 μM, which demonstrates that Halobacterium noricense can tolerate uranium concentrations up to this level. The formed uranium sorption species were examined with time-resolved laser-induced fluorescence spectroscopy (TRLFS). The results about the microbial communities present in potential host rocks for nuclear waste repositories and their interactions with radionuclides contribute to the safety assessment of a prospective nuclear waste repository.

  13. Microorganisms in potential host rocks for geological disposal of nuclear waste and their interactions with radionuclides

    International Nuclear Information System (INIS)

    Cherkouk, A.; Liebe, M.; Luetke, L.; Moll, H.; Stumpf, T.

    2015-01-01

    The long-term safety of nuclear waste in a deep geological repository is an important issue in our society. Microorganisms indigenous to potential host rocks are able to influence the oxidation state, speciation and therefore the mobility of radionuclides as well as gas generation or canister corrosion. Therefore, for the safety assessment of such a repository it is necessary to know which microorganisms are present in the potential host rocks (e.g. clay, salt) and if these microorganisms can influence the performance of a repository. Microbial diversity in potential host rocks for geological disposal of nuclear waste was analyzed by culture-independent molecular biological methods (e.g. 16S rRNA gene retrieval) as well as enrichment and isolation of indigenous microbes. Among other isolates, a Paenibacillus strain, as a representative of Firmicutes, was recovered in R2A media under anaerobic conditions from Opalinus clay from the Mont Terri in Switzerland. Accumulation experiments and potentiometric titrations showed a strong interaction of Paenibacillus sp. cells with U(VI) within a broad pH range (3-7). Additionally, the interactions of the halophilic archaeal strain Halobacterium noricense DSM 15987, a salt rock representative reference strain, with U(VI) at high ionic strength was investigated. After 48 h the cells were still alive at uranium concentrations up to 60 μM, which demonstrates that Halobacterium noricense can tolerate uranium concentrations up to this level. The formed uranium sorption species were examined with time-resolved laser-induced fluorescence spectroscopy (TRLFS). The results about the microbial communities present in potential host rocks for nuclear waste repositories and their interactions with radionuclides contribute to the safety assessment of a prospective nuclear waste repository.

  14. Diffusion of Radionuclides in Bentonite Clay - Laboratory and in situ Studies

    International Nuclear Information System (INIS)

    Jansson, Mats

    2002-12-01

    the bentonite. However, at some spots in the clay, the Tc activity was considerably higher. We ascribe these activity peaks to iron-containing minerals in the bentonite, by which Tc(VII) has been reduced to Tc(IV) and precipitated. The cations Sr 2+ , Cs + and Co 2+ , as well as the anion I-, behaved in the CHEMLAB experiments as expected from laboratory studies. Three experiments in the LOT series are completed. The first two diffusion experiments in LOT were less successful, the first due to the fact that saturation of the bentonite was not obtained during the experimental period and the radionuclides did not move at all. In the second, the uptake of the bentonite parcel was less successful. Water from the drilling flushed away large pieces of the top part of the bentonite and the lower part of the test parcel was super-saturated with water and expanded when released from the rock. The activity distribution in the second experiment was analysed. The Co 2+ profile looked as we had expected, while Cs + had spread more than our calculations indicated. However, the third experiment was successful from emplacement, water saturation and heating to uptake. The activity distribution for both cations was as expected from laboratory studies. Altogether the three different types of experiments give a uniform picture of radionuclide diffusion in bentonite clay for the ions investigated

  15. Study of radionuclide migration in clay formations

    International Nuclear Information System (INIS)

    Antonioli, F.; Bocola, W.

    1985-01-01

    This paper reports the studies on the migration of Cs, Sr and I in clay formations, which are presently considered for the geological disposal of radioactive wastes. The distribution and diffusion coefficients were evaluated by means of experimental techniques and computer procedures, which are presented in this report. The natural clays tested in the laboratory experiments were sampled from the most representative italian basins and from the zone of Mol (Belgium). In addition tests were performed on monomineral clays artificially remade in edometer. The experimental results are in accordance with data found in the literature and show the existence of a good correlation between the observed migration properties and the granulometric and mineralogic characteristics of the natural clays

  16. Sorption of long-lived radionuclides in clay and rock

    International Nuclear Information System (INIS)

    Allard, B.; Kipatsi, H.; Rydberg, J.

    1977-10-01

    The mechanism of sorption of water soluble species in the natural environment has been discussed. The radiochemical and radiobiological properties of the elements in spent nuclear fuel have been briefly discussed, and 14 of the radioactive products have been selected for studies of the sorption behaviour in contact with natural rock and clay minerals. These 14 elements are Sr, Zr, Tc, I, Cs, Ce, Nd, Eu, Ra, Th, U, Np, Pu and Am. From data available concerning composition and equilibria in natural subsoil waters two standard water compositions have been suggested for the laboratory measurements. Suitable concentrations of the radionuclides and experimental temperatures have been proposed. A batch technique has been used for determination of distribution coefficients for powdered solid materials. Measurements have been performed for all of the 14 elements with granite and bentonite/quartz mixture (10:90) with variation of water composition, nuclide concentration and temperature. Moreover, the effect of variation of the particle size has been studied for granite with Sr, Cs and Am, as well as the sorption in powdered granodiorite, chlorite and silt and on fresh and old rock surfaces (granite). The presence of organic components in bentonite has been confirmed and a preliminary complex formation study with these organics has been performed. An estimation of the valencestate of the actinides U, Np and Pu has been suggested using reasonable assumptions regarding the hydrolysis of the actinides and the presence of Fe(IIE/Fe(IE in natural waters. Using measured or calculated distribution coefficients and considering the chemical properties of the natural water system, relevant retention factors of the radionuclides have been proposed. (author)

  17. The use of clays as sorbents and catalysts

    International Nuclear Information System (INIS)

    McCabe, R.W.

    1998-01-01

    The paper attempts to show the structural, physical and chemical properties of clay minerals relate to their laboratory, industrial and environmental uses as sorbents and catalysts. A brief review of the formulae and structures of clays and their relationship to their chemical and physical properties follows. Clay minerals are also useful in environmental protection as they can adsorb crude oils from spills and they are used, sometimes mixed into concrete, as containment barriers for radionuclides caesium 137 and strontium 90. Clay soils can also act as natural barriers to the migration of radionuclides in the environment

  18. Naturally occurring radionuclides in agricultural products: An overview

    International Nuclear Information System (INIS)

    Hanlon, E.A.

    1994-01-01

    Low levels of naturally occurring radionuclides exist in phosphatic clays, a by-product of phosphatic mining and beneficiation processes. Concerns about these radionuclides entering the human food chain were an immediate research priority before the phosphate clays could be reclaimed for intensive agricultural purposes. Efforts included the assembly of a large body of data from both sons and plants, part of which were produced by the Polk County (Florida) Mined Lands Agricultural Research/Demonstration Project MLAR/DP. Additional detailed studies involving dairy and beef cattle (Bos taurus) were conducted by researchers working with the MLAR/DP. A national symposium was conducted in which data concerning the MLAR/DP work and other research projects also dealing with naturally occurring radionuclides in agriculture could be discussed. The symposium included invited review papers dealing with the identification of radionuclide geological origins, the geochemistry and movement of radionuclides within the environment, mechanisms of plant uptake, entry points into the food chain, and evaluation of dose and risk assessment to the consumer of low levels of radionuclides. The risk to human health of an individual obtaining 0.1 of his or her dietary intake from crops produced on phosphatic clays increased by 1 in 5 x 10 6 /yr above a control individual consuming no food grown on phosphatic clays. Leaf tissues were found to be generally higher than fruit, grain, or root tissues. The natural range in radionuclide content among various food types was greater than the difference in radionuclides content between the same food produced on phosphatic clays vs. natural soils. 19 refs

  19. Do scaly clays control seismicity on faulted shale rocks?

    Science.gov (United States)

    Orellana, Luis Felipe; Scuderi, Marco M.; Collettini, Cristiano; Violay, Marie

    2018-04-01

    One of the major challenges regarding the disposal of radioactive waste in geological formations is to ensure isolation of radioactive contamination from the environment and the population. Shales are suitable candidates as geological barriers. However, the presence of tectonic faults within clay formations put the long-term safety of geological repositories into question. In this study, we carry out frictional experiments on intact samples of Opalinus Clay, i.e. the host rock for nuclear waste storage in Switzerland. We report experimental evidence suggesting that scaly clays form at low normal stress (≤20 MPa), at sub-seismic velocities (≤300 μm/s) and is related to pre-existing bedding planes with an ongoing process where frictional sliding is the controlling deformation mechanism. We have found that scaly clays show a velocity-weakening and -strengthening behaviour, low frictional strength, and poor re-strengthening over time, conditions required to allow the potential nucleation and propagation of earthquakes within the scaly clays portion of the formation. The strong similarities between the microstructures of natural and experimental scaly clays suggest important implications for the slip behaviour of shallow faults in shales. If natural and anthropogenic perturbations modify the stress conditions of the fault zone, earthquakes might have the potential to nucleate within zones of scaly clays controlling the seismicity of the clay-rich tectonic system, thus, potentially compromising the long-term safeness of geological repositories situated in shales.

  20. Characterization of the porosity in Boom (Mol site, Belgium) and Opalinus (Mont Terri, Switzerland) clays - about the benefit of using ion beam milling tools and CRYO-SEM

    International Nuclear Information System (INIS)

    Desbois, G.; Houben, M.E.; Sholokhova, Y.; Urai, J.L.; Kukla, P.A.

    2010-01-01

    imaging of pore space at high resolution. The first of them is to use ion beam milling tools able to prepare smooth, damage free cross-sectioned surfaces. Two main ion source are available: (1) a broad ion beam (BIB, up to 3.5 mA) is suitable to produce large polished cross-sections area of few mm 2 , while the focused ion beam (FIB, 1 pA - 45 nA) is better used for fine and precise polished cross-sections area of about few μm 2 . The second alternative is to preserve the in-situ nanostructures of wet clay-stones by using cryogenic techniques in order to stabilize in-situ fluids at temperature of liquid nitrogen. A FIB/BIB-cryo- SEM instrument combines cryo-techniques to preserve wet samples, in-situ sample preparation by ion beam cross-sectioning (BIB or FIB) and observations of the stabilized microstructure at high resolution (SEM). Since the ion beam is directly embedded into the SEM, this instrument offers a unique way to get a direct access of the pore space in 3D by using a 'slice and view' procedure equivalent to nano-serial sectioning. This procedure allows us investigating the natural in-situ pore space as a 3D matrix. This contribution reports on a study of Boom and Opalinus clays from reference sites for research (respectively at Mol site, Belgium and Mont Terri, Switzerland) using cryo-SEM at cryogenic temperature, with ion beam cross-sectioning to prepare smooth, damage free surfaces. Pores commonly have crack-like tips, preferred orientation parallel to bedding and power law size distribution. We define a number of pore types depending on shape and location in the microstructure. 3-D reconstruction by serial cross-sectioning shows 3-D connectivity of the pore space and provide natural pore matrix for simulation of permeability using Lattice Boltzmann method. These findings offer a new insight into the morphology of pores and quantification of porosity down to nano-scale and provide the basis for microstructure-based models of transport in clays

  1. Mobility and Bioavailability of Radionuclides in Soils

    International Nuclear Information System (INIS)

    Iurian, A.; Olufemi Phaneuf, M.; Mabit, L.

    2016-01-01

    It is crucial to understand the behavior of radionuclides in the environment, their potential mobility and bioavailability related to long-term persistence, radiological hazards, and impact on human health. Such key information is used to develop strategies that support policy decisions. The environmental behavior of radionuclides depends on ecosystem characteristics. A given soil’s capacity to immobilize radionuclides has been proved to be the main factor responsible for their resulting activity concentrations in plants. The mobility and bioavailability of radionuclides in soils is complex, depending on clay-sized soil fraction, clay mineralogy, organic matter, cation exchange capacity, pH and quantities of competing cations. Moreover, plant species have different behaviors regarding radionuclide absorption depending on soil and plan characteristics

  2. Biogeochemical processes in a clay formation in situ experiment: Part A - Overview, experimental design and water data of an experiment in the Opalinus Clay at the Mont Terri Underground Research Laboratory, Switzerland

    International Nuclear Information System (INIS)

    Wersin, P.; Leupin, O.X.; Mettler, S.; Gaucher, E.C.; Maeder, U.; De Canniere, P.; Vinsot, A.; Gaebler, H.E.; Kunimaro, T.; Kiho, K.; Eichinger, L.

    2011-01-01

    Highlights: → The composition was affected by the complex interplay of diffusion, mineral and surface reactions. → The 13 C signals for carbon species showed significant variations which could only be partly explained. → The main cations remained remarkably constant during the experiment. → This underlines the strong buffering via cation exchange and carbonate dissolution/precipitation. - Abstract: An in situ test in the Opalinus Clay formation, termed porewater chemistry (PC) experiment, was carried out for a period of 5 years. It was based on the concept of diffusive equilibration whereby a traced water with a composition close to that expected in the formation was continuously circulated and monitored in a packed-off borehole. The main original focus was to obtain reliable data on the pH/pCO 2 conditions of the porewater, but because of unexpected microbiologically-induced redox reactions, the objective was extended to elucidate the biogeochemical processes occurring in the borehole and to understand their impact on pH/pCO 2 and porewater chemistry in the low permeability clay formation. The behaviour of the conservative tracers 2 H and Br - could be explained by diffusive dilution in the clay and moreover the results showed that diffusive equilibration between the borehole water and the formation occurred within about 3 year's time. However, the composition and pH/pCO 2 conditions differed considerably from those of the in situ porewater. Thus, pH was lower and pCO 2 was higher than indicated by complementary laboratory investigations. The noted differences are explained by microbiologically-induced redox reactions occurring in the borehole and in the interfacial wall area which were caused by an organic source released from the equipment material. The degradation of this source was accompanied by sulfate reduction and - to a lesser extent - by methane generation, which induced a high rate of acetogenic reactions corresponding to very high acetate

  3. Organic material in clay-based buffer materials and its potential impact on radionuclide transport

    International Nuclear Information System (INIS)

    Vilks, P.; Goulard, M.; Stroes-Gascoyne, S.; Haveman, S.A.; Bachinski, D.B.; Hamon, C.J.; Comba, R.

    1997-03-01

    AECL has submitted an Environmental Impact Statement (EIS) to evaluate the concept of nuclear fuel disposal at depth in crystalline rock of the Canadian Shield. In this disposal concept used fuel would be emplaced in corrosion-resistant containers which would be surrounded by clay-based buffer and backfill materials. Once groundwater is able to penetrate the buffer and corrosion-resistant container, radionuclides could be transported from the waste form to the surrounding geosphere, and eventually to the biosphere. The release of radionuclides from the waste form and their subsequent transport would be determined by the geochemistry of the disposal vault and surrounding geosphere. Organic substances affect the geochemistry of radionuclides through complexation reactions that increase solubility and alter mobility, by affecting the redox of certain radionuclides and by providing food for microbes. The purpose of this study was to determine whether the buffer and backfill materials proposed for use in a disposal vault contain organics that could be leached by groundwater in large enough quantities to complex with radionuclides and affect their mobility within the disposal vault and surrounding geosphere. Buffer material, made from a mixture of 50 wt.% Avonlea sodium bentonite and 50 wt.% silica sand, was extracted with deionized water to determine the release of dissolved organic carbon, humic acid and fulvic acid. The effect of radiation and heat from the used fuel was simulated by treating samples of buffer before leaching to various amounts of heat (60 deg C and 90 deg C) for periods of 2, 4 and 6 weeks, and to ionizing radiation with doses of 25 kGy and 50 kGy. Humic substances were isolated from the leachates to determine the concentrations of humic and fulvic acids and to determine their functional group content by acid-base titrations. The results showed that groundwater would leach significant amounts of organics that would complex with radionuclides such as

  4. Modeling Coupled Processes in Clay Formations for Radioactive Waste Disposal

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Hui-Hai; Rutqvist, Jonny; Zheng, Liange; Sonnenthal, Eric; Houseworth, Jim; Birkholzer, Jens

    2010-08-31

    As a result of the termination of the Yucca Mountain Project, the United States Department of Energy (DOE) has started to explore various alternative avenues for the disposition of used nuclear fuel and nuclear waste. The overall scope of the investigation includes temporary storage, transportation issues, permanent disposal, various nuclear fuel types, processing alternatives, and resulting waste streams. Although geologic disposal is not the only alternative, it is still the leading candidate for permanent disposal. The realm of geologic disposal also offers a range of geologic environments that may be considered, among those clay shale formations. Figure 1-1 presents the distribution of clay/shale formations within the USA. Clay rock/shale has been considered as potential host rock for geological disposal of high-level nuclear waste throughout the world, because of its low permeability, low diffusion coefficient, high retention capacity for radionuclides, and capability to self-seal fractures induced by tunnel excavation. For example, Callovo-Oxfordian argillites at the Bure site, France (Fouche et al., 2004), Toarcian argillites at the Tournemire site, France (Patriarche et al., 2004), Opalinus clay at the Mont Terri site, Switzerland (Meier et al., 2000), and Boom clay at Mol site, Belgium (Barnichon et al., 2005) have all been under intensive scientific investigations (at both field and laboratory scales) for understanding a variety of rock properties and their relations with flow and transport processes associated with geological disposal of nuclear waste. Clay/shale formations may be generally classified as indurated and plastic clays (Tsang et al., 2005). The latter (including Boom clay) is a softer material without high cohesion; its deformation is dominantly plastic. For both clay rocks, coupled thermal, hydrological, mechanical and chemical (THMC) processes are expected to have a significant impact on the long-term safety of a clay repository. For

  5. Modeling Coupled Processes in Clay Formations for Radioactive Waste Disposal

    International Nuclear Information System (INIS)

    Liu, Hui-Hai; Rutqvist, Jonny; Zheng, Liange; Sonnenthal, Eric; Houseworth, Jim; Birkholzer, Jens

    2010-01-01

    As a result of the termination of the Yucca Mountain Project, the United States Department of Energy (DOE) has started to explore various alternative avenues for the disposition of used nuclear fuel and nuclear waste. The overall scope of the investigation includes temporary storage, transportation issues, permanent disposal, various nuclear fuel types, processing alternatives, and resulting waste streams. Although geologic disposal is not the only alternative, it is still the leading candidate for permanent disposal. The realm of geologic disposal also offers a range of geologic environments that may be considered, among those clay shale formations. Figure 1-1 presents the distribution of clay/shale formations within the USA. Clay rock/shale has been considered as potential host rock for geological disposal of high-level nuclear waste throughout the world, because of its low permeability, low diffusion coefficient, high retention capacity for radionuclides, and capability to self-seal fractures induced by tunnel excavation. For example, Callovo-Oxfordian argillites at the Bure site, France (Fouche et al., 2004), Toarcian argillites at the Tournemire site, France (Patriarche et al., 2004), Opalinus clay at the Mont Terri site, Switzerland (Meier et al., 2000), and Boom clay at Mol site, Belgium (Barnichon et al., 2005) have all been under intensive scientific investigations (at both field and laboratory scales) for understanding a variety of rock properties and their relations with flow and transport processes associated with geological disposal of nuclear waste. Clay/shale formations may be generally classified as indurated and plastic clays (Tsang et al., 2005). The latter (including Boom clay) is a softer material without high cohesion; its deformation is dominantly plastic. For both clay rocks, coupled thermal, hydrological, mechanical and chemical (THMC) processes are expected to have a significant impact on the long-term safety of a clay repository. For

  6. Applying Squeezing Technique to Clayrocks: Lessons Learned from Experiments at Mont Terri Rock Laboratory

    International Nuclear Information System (INIS)

    Fernandez, A. M.; Sanchez-Ledesma, D. M.; Tournassat, C.; Melon, A.; Gaucher, E.; Astudillo, E.; Vinsot, A.

    2013-01-01

    Knowledge of the pore water chemistry in clay rock formations plays an important role in determining radionuclide migration in the context of nuclear waste disposal. Among the different in situ and ex-situ techniques for pore water sampling in clay sediments and soils, squeezing technique dates back 115 years. Although different studies have been performed about the reliability and representativeness of squeezed pore waters, more of them were achieved on high porosity, high water content and unconsolidated clay sediments. A very few of them tackled the analysis of squeezed pore water from low-porosity, low water content and highly consolidated clay rocks. In this work, a specially designed and fabricated one-dimensional compression cell two directional fluid flow was used to extract and analyse the pore water composition of Opalinus Clay core samples from Mont Terri (Switzerland). The reproducibility of the technique is good and no ionic ultrafiltration, chemical fractionation or anion exclusion was found in the range of pressures analysed: 70-200 MPa. Pore waters extracted in this range of pressures do not decrease in concentration, which would indicate a dilution of water by mixing of the free pore water and the outer layers of double layer water (Donnan water). A threshold (safety) squeezing pressure of 175 MPa was established for avoiding membrane effects (ion filtering, anion exclusion, etc.) from clay particles induced by increasing pressures. Besides, the pore waters extracted at these pressures are representative of the Opalinus Clay formation from a direct comparison against in situ collected borehole waters. (Author)

  7. Applying Squeezing Technique to Clayrocks: Lessons Learned from Experiments at Mont Terri Rock Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, A. M.; Sanchez-Ledesma, D. M.; Tournassat, C.; Melon, A.; Gaucher, E.; Astudillo, E.; Vinsot, A.

    2013-07-01

    Knowledge of the pore water chemistry in clay rock formations plays an important role in determining radionuclide migration in the context of nuclear waste disposal. Among the different in situ and ex-situ techniques for pore water sampling in clay sediments and soils, squeezing technique dates back 115 years. Although different studies have been performed about the reliability and representativeness of squeezed pore waters, more of them were achieved on high porosity, high water content and unconsolidated clay sediments. A very few of them tackled the analysis of squeezed pore water from low-porosity, low water content and highly consolidated clay rocks. In this work, a specially designed and fabricated one-dimensional compression cell two directional fluid flow was used to extract and analyse the pore water composition of Opalinus Clay core samples from Mont Terri (Switzerland). The reproducibility of the technique is good and no ionic ultrafiltration, chemical fractionation or anion exclusion was found in the range of pressures analysed: 70-200 MPa. Pore waters extracted in this range of pressures do not decrease in concentration, which would indicate a dilution of water by mixing of the free pore water and the outer layers of double layer water (Donnan water). A threshold (safety) squeezing pressure of 175 MPa was established for avoiding membrane effects (ion filtering, anion exclusion, etc.) from clay particles induced by increasing pressures. Besides, the pore waters extracted at these pressures are representative of the Opalinus Clay formation from a direct comparison against in situ collected borehole waters. (Author)

  8. Biogeochemical processes in a clay formation in situ experiment: Part A - Overview, experimental design and water data of an experiment in the Opalinus Clay at the Mont Terri Underground Research Laboratory, Switzerland

    Energy Technology Data Exchange (ETDEWEB)

    Wersin, P., E-mail: paul.wersin@gruner.ch [NAGRA, Hardstrasse 73, 5430 Wettingen (Switzerland)] [Gruner Ltd., Gellertstrasse 55, 4020 Basel (Switzerland); Leupin, O.X. [NAGRA, Hardstrasse 73, 5430 Wettingen (Switzerland); Mettler, S. [NAGRA, Hardstrasse 73, 5430 Wettingen (Switzerland)] [Solexperts Ltd., Mettlenbachstrasse 25, 8617 Moenchaltorf (Switzerland); Gaucher, E.C. [BRGM, 3 avenue Claude Guillemin, B.P. 36009, 45060 Orleans Cedex 2 (France); Maeder, U. [University of Bern, Institute of Geological Sciences, Baltzerstrasse 3, CH-3012 Bern (Switzerland); De Canniere, P. [SCK.CEN, Waste and Disposal Project, Boeretang 200, 2400 Mol (Belgium); Vinsot, A. [ANDRA, Laboratoire de Recherche Souterrain de Meuse/Haute-Marne, RD960 BP9, 55290 Bure (France); Gaebler, H.E. [BGR, Stilleweg 2, 30655 Hannover (Germany); Kunimaro, T. [JAEA, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Kiho, K. [CRIEPI, 1646 Abiko, Abiko-city Chiba 270-1194 (Japan); Eichinger, L. [Hydroisotop, 85301 Schweitenkirchen (Germany)

    2011-06-15

    Highlights: > The composition was affected by the complex interplay of diffusion, mineral and surface reactions. > The {sup 13}C signals for carbon species showed significant variations which could only be partly explained. > The main cations remained remarkably constant during the experiment. > This underlines the strong buffering via cation exchange and carbonate dissolution/precipitation. - Abstract: An in situ test in the Opalinus Clay formation, termed porewater chemistry (PC) experiment, was carried out for a period of 5 years. It was based on the concept of diffusive equilibration whereby a traced water with a composition close to that expected in the formation was continuously circulated and monitored in a packed-off borehole. The main original focus was to obtain reliable data on the pH/pCO{sub 2} conditions of the porewater, but because of unexpected microbiologically-induced redox reactions, the objective was extended to elucidate the biogeochemical processes occurring in the borehole and to understand their impact on pH/pCO{sub 2} and porewater chemistry in the low permeability clay formation. The behaviour of the conservative tracers {sup 2}H and Br{sup -} could be explained by diffusive dilution in the clay and moreover the results showed that diffusive equilibration between the borehole water and the formation occurred within about 3 year's time. However, the composition and pH/pCO{sub 2} conditions differed considerably from those of the in situ porewater. Thus, pH was lower and pCO{sub 2} was higher than indicated by complementary laboratory investigations. The noted differences are explained by microbiologically-induced redox reactions occurring in the borehole and in the interfacial wall area which were caused by an organic source released from the equipment material. The degradation of this source was accompanied by sulfate reduction and - to a lesser extent - by methane generation, which induced a high rate of acetogenic reactions

  9. Safety-relevant hydrogeological properties of the claystone barrier of a Swiss radioactive waste repository: An evaluation using multiple lines of evidence

    Science.gov (United States)

    Gautschi, Andreas

    2017-09-01

    In Switzerland, the Opalinus Clay - a Jurassic (Aalenian) claystone formation - has been proposed as the first-priority host rock for a deep geological repository for both low- and intermediate-level and high-level radioactive wastes. An extensive site and host rock investigation programme has been carried out during the past 30 years in Northern Switzerland, comprising extensive 2D and 3D seismic surveys, a series of deep boreholes within and around potential geological siting regions, experiments in the international Mont Terri Rock Laboratory, compilations of data from Opalinus Clay in railway and motorway tunnels and comparisons with similar rocks. The hydrogeological properties of the Opalinus Clay that are relevant from the viewpoint of long-term safety are described and illustrated. The main conclusions are supported by multiple lines of evidence, demonstrating consistency of conclusions based on hydraulic properties, porewater chemistry, distribution of natural tracers across the Opalinus Clay as well as small- and large-scale diffusion models and the derived conceptual understanding of solute transport.

  10. Determination of sorption mechanisms of radionuclides onto clay minerals using extended x-ray absorption fine structure (EXAFS) spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Daehn, R.; Scheidegger, A.; Baeyens, B.; Bradbury, M.H

    2001-03-01

    Much of the experimental work in the Waste Management Laboratory at PSI concentrates on trying to understand the processes and mechanisms which govern the release of safety-relevant radionuclides from waste matrices, and their transport through engineered barrier systems and the surrounding geosphere. For this reason, detailed sorption studies of radionuclides (Cs, Sr, Ni, Zn, Eu, Am, Th and Se) in clay and cement systems are being conducted. The sorption and modelling studies are combined with kinetic investigations and advanced spectroscopic and microscopic methods in order to understand the sorption mechanism on an atomic level. This approach is part of a new multidisciplinary research field called Molecular Environmental Science (MES). In this paper, a case study of Ni sorption on montmorillonite is presented to illustrate how EXAFS can be used successfully to better understand sorption processes. (author)

  11. Determination of sorption mechanisms of radionuclides onto clay minerals using extended x-ray absorption fine structure (EXAFS) spectroscopy

    International Nuclear Information System (INIS)

    Daehn, R.; Scheidegger, A.; Baeyens, B.; Bradbury, M.H.

    2001-01-01

    Much of the experimental work in the Waste Management Laboratory at PSI concentrates on trying to understand the processes and mechanisms which govern the release of safety-relevant radionuclides from waste matrices, and their transport through engineered barrier systems and the surrounding geosphere. For this reason, detailed sorption studies of radionuclides (Cs, Sr, Ni, Zn, Eu, Am, Th and Se) in clay and cement systems are being conducted. The sorption and modelling studies are combined with kinetic investigations and advanced spectroscopic and microscopic methods in order to understand the sorption mechanism on an atomic level. This approach is part of a new multidisciplinary research field called Molecular Environmental Science (MES). In this paper, a case study of Ni sorption on montmorillonite is presented to illustrate how EXAFS can be used successfully to better understand sorption processes. (author)

  12. In situ determination of anisotropic permeability of clay

    International Nuclear Information System (INIS)

    Shao, H.; Soennke, J.; Morel, J.; Krug, S.

    2011-01-01

    Argillaceous formations are being considered as potential host rocks for repositories of radioactive waste in many countries. For this purpose, the thermal, hydraulic, mechanical, and chemical properties of the clay stone are being widely investigated in the laboratories and in situ. However, clay stone behaves, due to its tectonic evolution of the formation, hydraulically and mechanically transversal isotropic. Argillite bedding or layering structure has been observed in the underground laboratories Mont Terri in the Switzerland and Meuse/Haute-Marne at Bure site in France. Conventional packer systems used for the borehole hydraulic characterisation cannot distinguish the difference between the properties parallel and perpendicular to the bedding. For this purpose, a new 'slot packer' system has been developed by the BGR. This type of new packer system is intensively tested in the BGR laboratory and the Mont Terri Rock Laboratory to judge the feasibility. The anisotropic ratio of the Opalinus clay defined by permeability value parallel to the bedding/permeability value perpendicular to the bedding is evaluated up to eight times to one order of magnitude within the HG-B experiment in the Mont Terri Rock Laboratory. Within the cooperation between BGR and ANDRA, the 'slot packer' will be used for the measurement of anisotropic permeability of the Callovo-Oxfordian formation at the Bure site. (authors)

  13. Monte Carlo simulations of GeoPET experiments: 3D images of tracer distributions (18F, 124I and 58Co) in Opalinus clay, anhydrite and quartz

    Science.gov (United States)

    Zakhnini, Abdelhamid; Kulenkampff, Johannes; Sauerzapf, Sophie; Pietrzyk, Uwe; Lippmann-Pipke, Johanna

    2013-08-01

    Understanding conservative fluid flow and reactive tracer transport in soils and rock formations requires quantitative transport visualization methods in 3D+t. After a decade of research and development we established the GeoPET as a non-destructive method with unrivalled sensitivity and selectivity, with due spatial and temporal resolution by applying Positron Emission Tomography (PET), a nuclear medicine imaging method, to dense rock material. Requirements for reaching the physical limit of image resolution of nearly 1 mm are (a) a high-resolution PET-camera, like our ClearPET scanner (Raytest), and (b) appropriate correction methods for scatter and attenuation of 511 keV—photons in the dense geological material. The latter are by far more significant in dense geological material than in human and small animal body tissue (water). Here we present data from Monte Carlo simulations (MCS) reflecting selected GeoPET experiments. The MCS consider all involved nuclear physical processes of the measurement with the ClearPET-system and allow us to quantify the sensitivity of the method and the scatter fractions in geological media as function of material (quartz, Opalinus clay and anhydrite compared to water), PET isotope (18F, 58Co and 124I), and geometric system parameters. The synthetic data sets obtained by MCS are the basis for detailed performance assessment studies allowing for image quality improvements. A scatter correction method is applied exemplarily by subtracting projections of simulated scattered coincidences from experimental data sets prior to image reconstruction with an iterative reconstruction process.

  14. SORPTION AND DISPERSION OF STRONTIUM RADIONUCLIDE IN THE BENTONITE-QUARTZ-CLAY AS BACKFILL MATERIAL CANDIDATE ON RADIOACTIVE WASTE REPOSITORY

    Directory of Open Access Journals (Sweden)

    Herry Poernomo

    2010-12-01

    Full Text Available The experiment of sorption and dispersion characteristics of strontium in the mixture of bentonite-quartz, clay-quartz, bentonite-clay-quartz as candidate of raw material for backfill material in the radioactive waste repository has been performed. The objective of this research is to know the grain size effect of bentonite, clay, and quartz on the weight percent ratio of bentonite to quartz, clay to quartz, bentonite to clay to-quartz can be gives physical characteristics of best such as bulk density (rb, effective porosity (e, permeability (K, best sorption characteristic such as distribution coefficient (Kd, and best dispersion characteristics such as dispersivity (a and effective dispersion coefficient (De of strontium in the backfill material candidate. The experiment was carried out in the column filled by the mixture of bentonite-quartz, clay-quartz, bentonite-clay-quartz with the weight percent ratio of bentonite to quartz, clay to quartz, bentonite to clay to quartz of 100/0, 80/20, 60/40, 40/60, 20/80, 0/100 respectively at saturated condition of water, then flowed 0.1 N Sr(NO32 as buffer solution with tracer of 0.05 Ci/cm3 90Sr as strontium radionuclide simulation was leached from immobilized radioactive waste in the radioactive waste repository. The concentration of 90Sr in the effluents represented as Ct were analyzed by Ortec b counter every 30 min, then by using profile concentration of Co and Ct, values of Kd, a and De of 90Sr in the backfill material was determined. The experiment data showed that the best results were -80+120 mesh grain size of bentonite, clay, quartz respectively on the weight percent ratio of bentonite to clay to quartz of 70/10/20 with physical characteristics of rb = 0.658 g/cm3, e = 0.666 cm3/cm3, and K = 1.680x10-2 cm/sec, sorption characteristic of Kd = 46.108 cm3/g, dispersion characteristics of a = 5.443 cm, and De = 1.808x10-03 cm2/sec can be proposed as candidate of raw material of backfill material

  15. Procedures and apparatus for measuring diffusion and distribution coefficients in compacted clays

    Energy Technology Data Exchange (ETDEWEB)

    Hume, H B

    1993-12-01

    Diffusion and distribution coefficients are needed to assess the migration of radionuclides through the compacted clay-based buffer and backfill materials proposed for use in a nuclear fuel waste disposal vault. This report describes the techniques used to measure these coefficients. Both steady-state and transient diffusion experiments are discussed. The procedures used to prepare the clay plug, assemble the cell, conduct the experiment and calculate the results are described. In addition, methods for obtaining distribution coefficients for radionuclides on both loose and compacted clays are discussed. (author). 18 refs., 3 tabs., 16 figs.

  16. Procedures and apparatus for measuring diffusion and distribution coefficients in compacted clays

    International Nuclear Information System (INIS)

    Hume, H.B.

    1993-12-01

    Diffusion and distribution coefficients are needed to assess the migration of radionuclides through the compacted clay-based buffer and backfill materials proposed for use in a nuclear fuel waste disposal vault. This report describes the techniques used to measure these coefficients. Both steady-state and transient diffusion experiments are discussed. The procedures used to prepare the clay plug, assemble the cell, conduct the experiment and calculate the results are described. In addition, methods for obtaining distribution coefficients for radionuclides on both loose and compacted clays are discussed. (author). 18 refs., 3 tabs., 16 figs

  17. A desk study of surface diffusion and mass transport in clay

    International Nuclear Information System (INIS)

    Cook, A.J.

    1988-09-01

    The concept of a geological barrier to radionuclide migration from theoretical radioactive waste repositories has drawn attention to the physico-chemical properties of clays, which are traditionally regarded as retarding media. This report addresses the different mechanisms of transport of radionuclides through clay and in particular focuses on the surface diffusion movement of sorbed cations. The relative contributory importance of the different transport mechanisms is governed by the pore size distributions and interconnections within the clay fabric. Surface diffusion data in the literature have been from experiments using compacted montmorillonite and biotite gneiss. A possible programme of laboratory work is outlined, based on diffusion experiments, which describes the way of measuring the effect of surface diffusion more accurately in clays, mudstones and shales. (author)

  18. Diffusion, sorption and stability of radionuclide-organic complexes in clays and clay-organic complexes

    International Nuclear Information System (INIS)

    Staunton, S.; Rees, L.V.C.

    1991-01-01

    The dependence on various parameters of the diffusion coefficient of neptunium (V) in clay systems has been studied. The effect of the clay mineralogy, the charge compensating cation in the clay, the ionic strength of a background perchlorate solution and the presence of three organic ligands have been investigated. The diffusion coefficients were compared to those predicted if diffusion occurred only in the liquid phase and adsorption was reversible; agreement was fairly good. An approximation to the diffusion coefficient can thus be obtained from readily measured experimental parameters. There is no evidence of surface phase diffusion. The most significant factor in determining the diffusion coefficient is the magnitude of the distribution ratio, itself highly dependent on the nature of the clay. Neither EDTA nor citrate modified the diffusion coefficient. Although the presence of 1 or 100 mg dm -3 of Aldrich humic acid had little effect on the distribution ratio of neptunium, it caused a lowering of the measured diffusion coefficient. This is interpreted in terms of the limiting liquid phase diffusion coefficient and the true liquid phase impedance factor of neptunium-humic acid complexes. 21 figs; 3 tabs; 20 refs

  19. Studying the Effect of Crystal Size on Adsorption Properties of Clay

    International Nuclear Information System (INIS)

    Abdellatif, M.M.

    2012-01-01

    Sorption of radionuclides on mineral surfaces strongly affects their fate and mobility in the geosphere. Therefore using of clay minerals as a barrier In LLW repositories can delay the dispersion of radionuclides into environment. That is of fundamental importance for maintaining environmental quality and for the safety and long-term performance of waste repositories. In this study XRD analysis was applied to investigate three different types of clay minerals for quantitative analysis of each type and the Mud Master program for the measurement of the crystallite thickness distribution (CTD) according to of the BWA (Bertaut-Warren Averbach) technique. Six sample s of the three types of clay (Kaolin, Aswan clay and Ball clay) were studied. XRD and Mud Master were used to investigate the relation between CTD and Cs -137 uptake mechanism onto the clay. It was found that the best adsorption capacity related to the kaolinite content and the lowest CTD

  20. Cementitious Near-Field Sorption Data Base for Performance Assessment of an ILW Repository in Opalinus Clay

    Energy Technology Data Exchange (ETDEWEB)

    Wieland, E.; Van Loon, L. R

    2003-08-01

    The present report describes a cement sorption database (SDB) for the safety-relevant radionuclides to be disposed of in the planned Swiss repository for long-lived intermediate-level radioactive wastes (ILW). This report is an update on earlier SDBs, which were compiled for the cementitious near field of a repository for low- and intermediate-level radioactive wastes (L/ILW) by BRADBURY + SAROTT (1995) and BRADBURY + VAN LOON (1998). The radionuclide inventories are determined by the waste streams to be disposed of in the ILW repository. A list of the safety-relevant radionuclides was provided based on the currently available information on ILW inventories. The compositions of the cement porewaters in the near fields of the L/ILW and ILW repositories, which had been calculated using well-established codes for modelling cement degradation, were compared to identify any differences in the near-field conditions and to assess their influence on radionuclide sorption. Sorption values were selected based on the previously reported SDBs for the near field of the L/ILW repository. Sorption values were revised if new information and/or data were available which allowed changes to or re-appraisals of the data to be made. The sorption values recommended in this report were either selected on the basis of data from in-house experimental studies or from literature data. For some key radioelements, i.e., Cs(l), Sr(II), Ni(II), Eu(lll), Th(IV) and Sn(IV), new data were available from in-house measurements. These elements had been selected for experimental studies due to their relevance to safety assessment and/or their importance as appropriate chemical analogues. Degradation products of bitumen and cellulose, concrete admixtures and cement-derived near-field colloids were taken into account as the main potential perturbations, which could reduce radionuclide sorption in the near field. Possible impacts of the perturbing factors on radionuclide mobility were considered and

  1. Conditions and processes affecting radionuclide transport

    Science.gov (United States)

    Simmons, Ardyth M.; Neymark, Leonid A.

    2012-01-01

    Characteristics of host rocks, secondary minerals, and fluids would affect the transport of radionuclides from a previously proposed repository at Yucca Mountain, Nevada. Minerals in the Yucca Mountain tuffs that are important for retarding radionuclides include clinoptilolite and mordenite (zeolites), clay minerals, and iron and manganese oxides and hydroxides. Water compositions along flow paths beneath Yucca Mountain are controlled by dissolution reactions, silica and calcite precipitation, and ion-exchange reactions. Radionuclide concentrations along flow paths from a repository could be limited by (1) low waste-form dissolution rates, (2) low radionuclide solubility, and (3) radionuclide sorption onto geological media.

  2. Understanding Radionuclide Interactions with Layered Materials

    Science.gov (United States)

    Wang, Y.

    2015-12-01

    Layered materials play an important role in nuclear waste management and environmental cleanup. Better understanding of radionuclide interactions with those materials is critical for engineering high-performance materials for various applications. This presentation will provide an overview on radionuclide interactions with two general categories of layered materials - cationic clays and anionic clays - from a perspective of nanopore confinement. Nanopores are widely present in layered materials, either as the interlayers or as inter-particle space. Nanopore confinement can significantly modify chemical reactions in those materials. This effect may cause the preferential enrichment of radionuclides in nanopores and therefore directly impact the mobility of the radionuclides. This effect also implies that conventional sorption measurements using disaggregated samples may not represent chemical conditions in actual systems. The control of material structures on ion exchange, surface complexation, and diffusion in layered materials will be systematically examined, and the related modeling approaches will be discussed. This work was performed at Sandia National Laboratories, which is a multiprogram laboratory operated by Sandia Corporation, a Lockheed-Martin Company, for the DOE under contract DE-AC04-94AL8500.

  3. Evaluation of radionuclide migration in the homogeneous system of a geological repository

    International Nuclear Information System (INIS)

    Prvakova, S.; Duran, J.; Necas, V.

    2005-01-01

    The aim of this paper is to study radionuclide migration and release from a deep underground repository situated in a clay formation. An insight into the processes influencing the radionuclide transport in the near field and far field will be presented. For the calculation, a set of radionuclides has been chosen, considering the half-life, decay chains, capacity of the sorption, solubility limits and diffusion coefficients. The migration of radionuclides is dependent on transport properties of the particular nuclide. Due to the low hydraulic conductivity of the backfill material and clay geological formation, the transport in the repository occurs mainly by diffusion. The migration rate will be influenced by the water chemistry, solubility, retardation and diffusive properties of the nuclides, and the water flow rate in the clay. The release rates of radionuclides from the geosphere to the biosphere will be converted into the indicative dose rates using dose conversion factors for ingestion. The impact of the critical group is considered via consumption of meat, root vegetables and drinking water from wells. (author)

  4. Radionuclide transport in clay during climate change

    NARCIS (Netherlands)

    Wildenborg, A.F.B.; Orlic, B.; Thimus, J.F.; De Lange, G.; De Cock, S.; De Leeuwe, C.S.; Veling, E.J.M.

    2002-01-01

    The Dutch national research programme into the feasibility of retrievable storage of radioactive waste (CORA Programme Phase I; CORA: Comité Opslag Radioactief Afval = Committee on Radioactive Waste Disposal) examined the suitability of Tertiary clay deposits for such storage. Long-term isolation –

  5. Radionuclide transport in clay during climate change

    NARCIS (Netherlands)

    Wildenborg, A.F.B.; Orlic, B.; Thimus, J.F.; Lange, G.de; Cock, S. de; Leeuw, C.S. de; Veling, E.J.M.

    2003-01-01

    The Dutch national research programme into the feasibility of retrievable storage of radioactive waste (CORA Programme Phase I; CORA: Comité Opslag Radioactief Afval = Committee on Radioactive Waste Disposal) examined the suitability of Tertiary clay deposts for such storage. Long-term isolation -

  6. Chemical processes at the surface of various clays on acid-base titration

    International Nuclear Information System (INIS)

    Park, K. K.; Park, Y. S.; Jung, E. C.

    2010-01-01

    The chemical reaction of radionuclides at the interface between groundwater and geological mineral is an important process determining their retardation of transport through groundwater flow in a nuclear waste disposal. Clay minerals are major components of soil and argillaceous rock, and some of them are considered to be important base materials in the design of high-level nuclear waste repository due to their large swelling, low-permeability, large surface area, and strong and large sorption of radionuclides. Clay materials are phyllosilicates containing accessory minerals such as metal oxides, hydroxides, oxyhydroxides. Their structures are condensed 1:1 or 2:1 layers of tetrahedral SiO 3/2 OH and octahedral Al(OH) 6/2 sheets. An accurate knowledge about the properties of clay surface is required as a parameter for a long-term estimation of radionuclide retardation effects. Electric surface charge is a primary property determining ion exchange and surface complexation of radionuclides on its surface. The sources of electric surface charge are a permanent structural negative charge on a basal plane and a dissociable charge at an edge surface. Investigation of proton sorption is a prerequisite to the understanding of radionuclide sorption. The reactions on a permanently charged site and on an edge site are measured by an electrokinetic measurement and by potentiometric titration, respectively. However, side reactions such as complexation, proton/cation exchange, dissolution, hydrolysis, precipitation and re adsorption, and the reaction of secondary minerals hinder an experimental measurement of accurate acid-base properties. This presentation describes the pH change on dispersing various clays in water and adding acid, base or Eu(III) ion to these solutions, and the effect of Eu(III) ion on acid-base titration of clay solutions

  7. Chemical processes at the surface of various clays on acid-base titration

    Energy Technology Data Exchange (ETDEWEB)

    Park, K. K.; Park, Y. S.; Jung, E. C. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2010-10-15

    The chemical reaction of radionuclides at the interface between groundwater and geological mineral is an important process determining their retardation of transport through groundwater flow in a nuclear waste disposal. Clay minerals are major components of soil and argillaceous rock, and some of them are considered to be important base materials in the design of high-level nuclear waste repository due to their large swelling, low-permeability, large surface area, and strong and large sorption of radionuclides. Clay materials are phyllosilicates containing accessory minerals such as metal oxides, hydroxides, oxyhydroxides. Their structures are condensed 1:1 or 2:1 layers of tetrahedral SiO{sub 3/2}OH and octahedral Al(OH){sub 6/2} sheets. An accurate knowledge about the properties of clay surface is required as a parameter for a long-term estimation of radionuclide retardation effects. Electric surface charge is a primary property determining ion exchange and surface complexation of radionuclides on its surface. The sources of electric surface charge are a permanent structural negative charge on a basal plane and a dissociable charge at an edge surface. Investigation of proton sorption is a prerequisite to the understanding of radionuclide sorption. The reactions on a permanently charged site and on an edge site are measured by an electrokinetic measurement and by potentiometric titration, respectively. However, side reactions such as complexation, proton/cation exchange, dissolution, hydrolysis, precipitation and re adsorption, and the reaction of secondary minerals hinder an experimental measurement of accurate acid-base properties. This presentation describes the pH change on dispersing various clays in water and adding acid, base or Eu(III) ion to these solutions, and the effect of Eu(III) ion on acid-base titration of clay solutions

  8. The application of small-angle neutron scattering to the study of mass transfer in clays

    International Nuclear Information System (INIS)

    Allen, A.J.; Baston, A.H.; Bourke, P.J.; Jefferies, N.L.

    1990-01-01

    An extensive study using small angle neutron scattering (SANS) has been made of the pore structures in London Clay and in Ca-montmorillonite. Using SANS contrast variation techniques, the accessibilities of the pores to D 2 O by diffusion and permeation have been studied. Characterisation of the accessibility to different parts of the pore structure is intended to provide input data for models of radionuclide transport through clay geological barriers, and to improve interpretation of laboratory experiments that measure sorption of radionuclides on clays. (author)

  9. Clay colloid formation and release from MX-80 buffer

    International Nuclear Information System (INIS)

    Pusch, R.

    1999-12-01

    Flowing groundwater can tear off clay colloids from buffer clay that has penetrated into fractures and transport them and bring sorbed radionuclides up to the biosphere. The colloids are 2-50 μm particle aggregates that are liberated from expanded, softened buffer if the water flow rate in the fractures exceeds a few centimeters per second. Except for the first few months or years after application of the buffer in the deposition holes the flow rate will not be as high as that. The aperture of the fractures will not hinder transport of colloids but most of the fractures contain clastic fillings, usually chlorite, that attract and immobilize them. This condition and the flow rate criterion combine to reduce the chance of radionuclide-bearing clay colloids to reach the biosphere to practically zero except for certain cases that need to be considered

  10. Interpretation of reflection seismics in the area North of Laegeren - Zurich Weinland

    International Nuclear Information System (INIS)

    Naef, H.; Birkhaeuser, P.; Roth, P.

    1995-05-01

    The investigations of potential siting areas for a repository for high-level radioactive waste which are concentrated in the crystalline basement of Northern Switzerland have been expanded since the late 1980s to include suitable sedimentary units. After extensive desk study evaluation, the approximately 100 m thick Opalinus Clay of the Tabular Jura east of the Aare river was chosen as the most promising sedimentary option. In this area not only the Opalinus Clay but also the over- and underlying units are clay-rich, in contrast to the tabular Jura west of the Aare river. In the area North of Laegeren - Zurich Weinland, where the Opalinus Clay is situated in the optimum depth range of 400 to 1000 m below surface, approximately 220 km of new high-resolution seismic profiles were recorded and interpreted together with existing seismic lines. Due to thorough field work and data processing, a very good quality of seismic lines was obtained. This allowed precise mapping of the marker horizons in general and the Opalinus Clay in detail. The goal of this study was to determine and delineate the most important tectonic units as well as to describe the potential host rocks in these units. By way of interactive interpretation of all available seismic lines, borehole data and surface data from the investigation area, depth maps of the most prominent marker horizons have been calculated and geological cross-sections constructed along the new seismic lines. The regional seismic character of the Middle Mesozoic units was modelled using borehole data from Weiach and Herdern. From this model the thickness of the Opalinus Clay along the new seismic lines was determined. The results indicate a relatively constant thickness of 95 to 120 m in the investigation area. (author) figs., tabs., refs

  11. The release of organic material from clay based buffer materials and its potential implications for radionuclide transport

    International Nuclear Information System (INIS)

    Vilks, P.; Stroes-Gascoyne, S.; Goulard, M.; Haveman, S.A.; Bachinski, D.B.

    1998-01-01

    In the Canadian nuclear fuel waste disposal concept used fuel would be placed in corrosion resistant containers which would be surrounded by clay-based buffer and backfill materials in an engineered vault excavated at 500 to 1000 m depth in crystalline rock formations in the Canadian shield. Organic substances could affect radionuclide mobility due to the effects of redox and complexation reactions that increase solubility and alter mobility. The purpose of this study was to determine whether the buffer and backfill materials, proposed for use in a disposal vault, contain organics that could be leached by groundwater in large enough quantities to affect radionuclide mobility within the disposal vault and surrounding geosphere complex. Buffer material, made from a mixture of 50 wt.% Avonlea sodium bentonite and 50 wt.% silica sand, was extracted with deionized water to determine the release of dissolved organic carbon (DOC), humic acid and fulvic acid. The effect of radiation and heat from the used fuel was simulated by treating samples of buffer before leaching to various amounts of heat (60 and 90 C) for periods of 2, 4 and 6 weeks, and to ionizing radiation with doses of 25 kGy and 50 kGy. The results showed that groundwater would leach significant amounts of organics from buffer that complex with radionuclides such as the actinides, potentially affecting their solubility and transport within the disposal vault and possibly the surrounding geosphere. In addition, the leached organics would likely stimulate microbial growth by several orders of magnitude. Heating and radiation affect the amount and nature of leachable organics. (orig.)

  12. Modeling of Cation Binding in Hydrated 2:1 Clay Minerals - Final Report

    International Nuclear Information System (INIS)

    Smith, David E.

    2000-01-01

    Hydrated 2:1 clay minerals are high surface area, layered silicates that play a unique role in determining the fate of radionuclides in the environment. This project consisted of developing and implementing computer simulation methods for molecular characterization of the swelling and ion exchange properties of Hydrated 2:1 clay minerals, and the subsequent analysis and theoretical modeling with a view toward improving contaminant transport modeling as well as soil remediation and radionuclide containment strategies. Project results included the (a) development of simulation methods to treat clays under environmentally relevant conditions of variable water vapor pressure; (b) calculation of clay swelling thermodynamics as a function of interlayer ion size and charge (calculated quantities include immersion energies, free energies, and entropies of swelling); and (c) calculation of ion exchange free energies, including contributions from changing interlayer water contents and layer spacing

  13. Final Report (BMWi Project No.: 02 E 10971): Joint project: Retention of radionuclides relevant for final disposal in natural clay rock and saline systems - Subproject 2: Geochemical behavior and transport of radionuclides in saline systems in the prese

    Energy Technology Data Exchange (ETDEWEB)

    Schmeide, Katja [Helmholtz-Zentrum Dresden, (Germany). Inst. of Resource Ecology; Fritsch, Katharina [Helmholtz-Zentrum Dresden, (Germany). Inst. of Resource Ecology; Lippold, Holger [Helmholtz-Zentrum Dresden, (Germany). Inst. of Resource Ecology; Poetsch, Maria [Helmholtz-Zentrum Dresden, (Germany). Inst. of Resource Ecology; Kulenkampff, Johannes [Helmholtz-Zentrum Dresden, (Germany). Inst. of Resource Ecology; Lippmann-Pipke, Johanna [Helmholtz-Zentrum Dresden, (Germany). Inst. of Resource Ecology; Jordan, Norbert [Helmholtz-Zentrum Dresden, (Germany). Inst. of Resource Ecology; Joseph, Claudia [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Helmholtz-Zentrum Dresden, (Germany). Inst. of Resource Ecology; Moll, Henry [Helmholtz-Zentrum Dresden, (Germany). Inst. of Resource Ecology; Cherkouk, Andrea [Helmholtz-Zentrum Dresden, (Germany). Inst. of Resource Ecology; Bader, Miriam [Helmholtz-Zentrum Dresden, (Germany). Inst. of Resource Ecology

    2016-02-29

    The objective of this project was to study the influence of increased salinities on interaction processes in the system radionuclide – organics – clay – aquifer. For this, complexation, redox, sorption, and diffusion studies were performed under variation of the ionic strength (up to 4 mol kg-1) and the background electrolyte (NaCl, CaCl2, MgCl2).

  14. Naturally Occurring Radionuclides in Pottery, Ceramic and Glasswares Produced in Bangladesh

    International Nuclear Information System (INIS)

    Chowdhury, M.I.; Reaz, Rafia; Kamal, M.; Alam, M.N.; Mustafa, M.N.

    2005-01-01

    The concentrations of naturally occurring radionuclides were measured using gamma spectrometry in the finished products of pottery, glass, ceramic and tiles. Ceramic and pottery utensils, tiles, basin and glassware contained naturally occurring radionuclides. Pottery is produced from local clay materials, but ceramic, tiles, basin and glassware's are made from both local and imported raw materials. Radium and thorium radionuclides are concentrated during the making of pottery from the clay materials due to calcination. Radionuclides concentrated more in the highly calcined pottery products than the low calcined products. Glassware products contained very low quantities of radionuclides comparing with the ceramic and pottery products. Study on radioactivity in the pottery, ceramic and glassware products is important in the assessment of possible radiological hazards to human health. The knowledge is essential for the development of standards and guidelines for the use and management of these materials. (author)

  15. Results of laboratory and in-situ measurements for the description of coupled thermo-hydro-mechanical processes in clays

    Energy Technology Data Exchange (ETDEWEB)

    Goebel, Ingeborg; Alheid, Hans-Joachim [BGR Hannover, Stilleweg 2, D-30655 Hannover (Germany); Jockwer, Norbert [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH, Theodor-Heuss-Str. 4, 38122 Braunschweig (Germany); Mayor, Juan Carlos [ENRESA, Emilio Vargas 7, E-Madrid (Spain); Garcia-Sineriz, Jose Luis [AITEMIN, c/ Alenza, 1 - 28003 Madrid (Spain); Alonso, Eduardo [International Center for Numerical Methods in Engineering, CIMNE, Edificio C-1, Campus Norte UPC, C/Gran Capitan, s/n, 08034 Barcelona (Spain); Weber, Hans Peter [NAGRA, Hardstrasse 73, CH-5430 Wettingen (Switzerland); Ploetze, Michael [ETHZ, Eidgenoessische Technische Hochschule Zuerich, ETH Zentrum, HG Raemistrasse 101, CH-8092 Zuerich (Switzerland); Klubertanz, Georg [COLENCO Power Engineering Ltd, CPE, Taefern Str. 26, 5405 Baden-Daettwil (Switzerland); Ammon, Christian [Rothpletz, Lienhard, Cie AG, Schifflaendestrasse 35, 5001 Aarau (Switzerland)

    2004-07-01

    The Heater Experiment at the Mont Terri Underground Laboratory aims at producing a validated model of thermo-hydro-mechanically (THM) coupled processes. The experiment consists of an engineered barrier system where in a vertical borehole, a heater is embedded in bentonite blocks, surrounded by the host rock, Opalinus Clay. The experimental programme comprises permanent monitoring before, during, and after the heating phase, complemented by geotechnical, hydraulic, and seismic in-situ measurements as well as laboratory analyses of mineralogical and rock mechanics properties. After the heating, the experiment was dismantled for further investigations. Major results of the experimental findings are outlined. (authors)

  16. Disposal of radioactive waste into clay layers the most natural option

    International Nuclear Information System (INIS)

    Baetsle, L.H.; Bonne, A.

    1990-01-01

    Among the geological formations suitable for the disposal of radioactive waste, the clay formations provide outstanding opportunities : impermeable for water, self-healing, strongly absorbing for ions, widespread in nature. The self-healing properties of large clay deposits have been demonstrated by their auto-sealing and plastic response to tectonic stress and magmatic intrusion. The discovery of fossil trees preserved after geologic periods of burial in clay is one of the most dramatic illustrations of their entombment ability. The physicochemical and hydrologic characteristics of the Boom clay are very favorable for the confinement of migrating radionuclides within the layer. Except for the extremely long half-lives ( 237 Np, 129 I,...) no radionuclide can escape from the clay body. The effects of heat, metal corrosion, material interaction and biochemical degradation on the natural properties of the clay layer are discussed in some detail and related to the natural properties of the clay formation which have to stay unaltered for geologic periods. The first Safety Assessment Report, established by NIRAS-ONDRAF in close collaboration with SCK-CEN, has been submitted to a multi-disciplinary task force which is to advise the Belgian Government on the suitability of the Boom clay layer below the Nuclear Research site of Mol as a potential host formation for nuclear waste coming from the electronuclear program. 13 refs., 2 figs., 1 tab

  17. Speciation of uranium in surface-modified, hydrothermally treated, (UO2)2+-exchanged smectite clays

    International Nuclear Information System (INIS)

    Giaquinta, D.M.; Soderholm, L.; Yuchs, S.E.; Wasserman, S.R.

    1997-01-01

    A successful solution to the problem of disposal and permanent storage of water soluble radioactive species must address two issues: exclusion of the radionuclides from the environment and the prevention of leaching from the storage media into the environment. Immobilization of radionuclides in clay minerals has been studied. In addition to the use of clays as potential waste forms, information about the interactions of radionuclides with clays and how such interactions affect their speciations is crucial for successful modeling of actinide-migration. X-ray absorption spectroscopy (XAS) is used to determine the uranium speciation in exchanged and surface-modified clays. The XAS data from uranyl-loaded bentonite clay are compared with those obtained after the particle surfaces have been coated with alkylsilanes. These silane films, which render the surface of the clay hydrophobic, are added in order to minimize the ability of external water to exchange with the water in the clay interlayer, thereby decreasing the release rate of the exchanged-uranium species. Mild hydrothermal conditions are used in an effort to mimic potential geologic conditions that may occur during long-term radioactive waste storage. The XAS spectra indicate that the uranyl monomer species remain unchanged in most samples, except in those samples that were both coated with an alkylsilane and hydrothermally treated. When the clay was coated with an organic film, formed by the acidic deposition of octadecyltrimethoxysilane, hydrothermal treatment results in the formation of aggregated uranium species in which the uranium is reduced from U VI to U IV

  18. 5-year chemico-physical evolution of concrete-claystone interfaces, Mont Terri rock laboratory (Switzerland)

    Energy Technology Data Exchange (ETDEWEB)

    Mäder, U.; Jenni, A. [Institute of Geological Sciences, University of Berne, Berne (Switzerland); Lerouge, C. [French Geological Survey BRGM, Orléans (France); and others

    2017-04-15

    The Cement-Opalinus Clay Interaction (CI) Experiment at the Mont Terri rock laboratory is a long-term passive diffusion-reaction experiment between contrasting materials of relevance to engineered barrier systems/near-field for deep disposal of radioactive waste in claystone (Opalinus Clay). Reaction zones at interfaces of Opalinus Clay with two different types of concrete (OPC and 'low-pH'/ESDRED) were examined by sampling after 2.2 and 4.9 years. Analytical methods included element mapping (SEM, EPMA), select spot analysis (EDAX), 14C-MMA impregnation for radiography, and powder methods (IR, XRD, clay-exchanger characterisation) on carefully extracted miniature samples (mm). The presence of aggregate grains in concrete made the application of all methods difficult. Common features are a very limited extent of reaction within claystone, and a distinct and regularly zoned reaction zone within the cement matrix that is more extensive in the low-alkali cement (ESDRED). Both interfaces feature a de-calcification zone and overprinted a carbonate alteration zone thought to be mainly responsible for the observed porosity reduction. While OPC shows a distinct sulphate enrichment zone (indicative of ingress from Opalinus Clay), ESDRED displays a wide Mg-enriched zone, also with claystone pore-water as a source. A conclusion is that substitution of OPC by low-alkali cementitious products is not advantageous or necessary solely for the purpose of minimizing the extent of reaction between claystone and cementitious materials. Implications for reactive transport modelling are discussed. (authors)

  19. Radionuclide adsorption characteristics around coastal water

    International Nuclear Information System (INIS)

    Song, Young Il; Chung, Yang Geun; Hong, Sung Yul; Lee, Gab Bock

    1999-01-01

    The adsorption capacity of radionuclides onto suspended sediment was experimented on each of the coastal seawater sampled around the Kori and the Wolsung nuclear power plant. During the experiment the quantity and size fraction of suspended sediment were adjusted and the seawater and sediment chemistry is approximated to the expected field condition. Because the sorption capacity depends on the specific minerals, ocean chemistry and radionuclide involved, it is necessary to analyze sediment mineralogy. Clay mineral is dominant in seabed mineral and suspended sediment as the result of x-ray diffraction. Radionuclide sorbed to silty-clay mineral can be rather transported to ocean than scavenged to seabed because of low quantity and fine grained suspended sediment in the coast around the Kori and the Wolsung. The result of adsorption examinations shows that 139 Ce and 51 Cr and 110m Ag are strongly sorbed to suspended particle, while 137 Cs is less sorbed and 60 Co uptake is varied with experiment condition, which can be inferred from various biological factors. (author). 9 refs., 2 tabs., 7 figs

  20. Radioanalytical procedures used to study the release of radionuclides from spent nuclear fuel and the diffusion into bentonite clay

    International Nuclear Information System (INIS)

    Ramebaeck, H.; Albinsson, Yngve; Skaalberg, M.; Eklund, U.B.

    1999-12-01

    This report presents radio-analytical procedures for the assay of 90 Sr, 99 Tc, 237 Np, 239 Pu, 241 Am and 244 Cm. These analytical procedures were used in a project studying the release and diffusion of radionuclides from spent nuclear fuel into bentonite clay. The main task was to use methods giving a high specificity in the detection combined with a low detection limit. A high specificity will eliminate errors caused by interferences, yielding errors in the analysis. A low detection limit was necessary since the release was often very low. Solvent extraction was used in order to remove interferences. The detection methods, radiometric or mass spectrometric, were chosen to give the lowest detection limit

  1. Technetium migration in Boom Clay - Assessing the role of colloid-facilitated transport in a deep clay formation

    International Nuclear Information System (INIS)

    Bruggeman, C.; Martens, E.; Maes, N.; Jacops, E.; Van Gompel, M.; Van Ravestyn, L.

    2010-01-01

    Document available in extended abstract form only. The role of colloids - mainly dissolved natural organic matter (NOM, 50-150 mg/l) - in the transport of radionuclides in the Boom Clay formation (Mol, Belgium), has long since been a matter of (heavy) debate. For more than 20 years, batch experiments with Boom Clay suspensions showed a pronounced influence of the dissolved organic carbon concentration on the aqueous concentrations of different radionuclides like Tc, Np, Am and U. Moreover, small fractions of these radionuclides were also observed to elute almost un-retarded out of confined clay cores in percolation experiments. In the past years, a new conceptual model for the speciation of the long-lived fission product Technetium- 99 ( 99 Tc) under Boom Clay conditions has been drafted. In brief, the stable oxidation state of 99 Tc in these conditions is +IV, and, therefore, Tc solution concentrations are limited by the solubility of TcO 2 .nH 2 O(s). However, during reduction of TcVII (in the TcO 4 - form) to TcIV, precursor TcO 2 .nH 2 O colloids are formed, which are stabilised by the dissolved organic matter present in Boom Clay interstitial pore water, and in supernatants of Boom Clay batch suspensions. Moreover, this stabilisation process occurs in such a systematic way, that (conditional) interaction constants could be established, and the behaviour was described as a 'hydrophobic sorption', or, more accurately, a 'colloid-colloid' interaction. This conceptual model was implemented into PHREEQC geochemical and Hydrus transport code to come to a reactive transport model that was used to simulate both the outflow and the tracer profile in several long-term running percolation experiments (both in lab and under in situ conditions). To account for slow dissociation kinetics of Tc from the NOM colloid, a first-order kinetic rate equation was also added to the model. In order to describe the migration of colloidal particles (NOM), an

  2. Exploring diffusion and sorption processes at the Mont Terri rock laboratory (Switzerland): lessons learned from 20 years of field research

    Energy Technology Data Exchange (ETDEWEB)

    Leupin, O.X. [National Cooperative for the Disposal of Radioactive Waste (NAGRA), Wettingen (Switzerland); Van Loon, L.R. [Paul Scherrer Institute PSI, Villigen (Switzerland); Gimmi, T. [Institute of Geological Sciences, University of Berne, Berne (Switzerland); Gimmi, T. [Institute of Environmental Assessment and Water Research IDAEA-CSIC, Barcelona (Spain); and others

    2017-04-15

    Transport and retardation parameters of radionuclides, which are needed to perform a safety analysis for a deep geological repository for radioactive waste in a compacted claystone such as Opalinus Clay, must be based on a detailed understanding of the mobility of nuclides at different spatial scales (laboratory, field, geological unit). Thanks to steadily improving experimental designs, similar tracer compositions in different experiments and complementary small laboratory-scale diffusion tests, a unique and large database could be compiled. This paper presents the main findings of 20 years of diffusion and retention experiments at the Mont Terri rock laboratory and their impact on safety analysis. (authors)

  3. Association of radionuclides with streambed sediments in White Oak Creek watershed

    International Nuclear Information System (INIS)

    Spalding, B.P.; Cerling, T.E.

    1979-09-01

    Radionuclides are found in much higher concentrations on streambed sediment than in the water of White Oak Creek. Selective extraction of sediments demonstrates that 60 Co is immobilized in a nonexchangeable form in the ferromanganese hydrous oxide coatings on the sediments; 90 Sr occurs predominantly in an exchangeable form on clay, iron oxides, and ferromanganese hydrous oxides; 137 Cs occurs in a nonexchangeable and strongly bound form on clays which compose the dominant rock (Conasauga shale) in the watershed. The fine-gravel to coarse-sand size fraction of streambed sediments is the most suitable fraction for radionuclide analysis because of its abundance in the sediment and its high concentration of radionuclides compared to larger and smaller size fractions. A preliminary survey of all major tributes in White Oak Creek shows that radionuclide analysis of streambed sediments is a very useful technique to locate sources of radioactive contamination

  4. Hydrogeologische Untersuchungen im oberflächennahen Opalinuston (Bohrloch Lausen, Schweiz)

    Science.gov (United States)

    Vogt, Tobias; Hekel, Uwe; Ebert, Andreas; Becker, Jens K.; Traber, Daniel; Giger, Silvio; Brod, Monika; Häring, Christian

    2017-09-01

    In Switzerland, the Opalinus Clay is being investigated in detail as a host rock for disposal of radioactive waste. To complement and improve existing data on near-surface decompaction effects, hydraulic-hydrochemical characterization of the Opalinus Clay from the weathering zone into the unweathered rock below was performed. For these investigations, one borehole of a borehole heat-exchanger field in Lausen (Canton Basel-Landschaft, Switzerland), which penetrates the near-surface Opalinus Clay, was completely cored. The hydraulic conductivity was determined by means of hydraulic tests in different depths and shows an decrease from 10-4 m/s at the very shallow weathered zone to 10-13 m/s starting at a depth of 28 m below the decompaction zone. In addition, different groundwater types could be identified. Moreover, the structural investigations indicate the end of the weathering zone at a depth of 18 m and that decompaction has no influence on hydraulic conductivity from 28 m onwards.

  5. Self-sealing of excavation induced fractures in clay host rock

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Chun-Liang [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH, Braunschweig (Germany)

    2015-07-01

    Excavation of an underground repository for disposal of radioactive waste in clay formations generates fractures around the openings, which may act as pathways for water transport and radionuclides migration. Because of the favorable properties of the clay rocks such as the rheological deformability and swelling capability, a recovery process of the excavation damaged zone (EDZ) can be expected due to the combined impact of rock compression, backfill resistance, and clay swelling during the post-closure phase. Another important issue is the impact of gases produced from anoxic corrosion of waste containers and other metallic components within the repository. The EDZ may act as a conduit for preferential gas flow, depending on the extent of the recovery process. For the safety assessment of a repository, the self-sealing behaviour and impact on water and gas transport through the EDZ have to be characterized, understood, and predicted. Recently, GRS has extensively investigated these important issues with various kinds of laboratory and in- situ experiments under relevant repository conditions. Test samples were taken from the Callovo-Oxfordian argillite at Bure in France and the Opalinus clay (shaly facies) at Mont Terri in Switzerland. Major findings are summarized as follows. As observed in laboratory and in-situ, the gas permeabilities of the claystones increase with stress-induced damage by several orders of magnitude from the impermeable state up to high levels of 10{sup -12}-10{sup -13} m{sup 2}. When hydrostatic confining stress is applied and increased, the fractures in the claystones tend to close up, leading to a decrease in gas permeability down to different levels of 10{sup -16}-10{sup -21} m{sup 2} at stresses in a range of 10 to 20 MPa. As water enters and flows through fractures, the clay matrix can take up a great amount of the water and expand into the interstices. Consequently, the hydraulic conductivity decreases dramatically by several orders of

  6. Monitoring and modelling of thermo-hydro-mechanical processes - main results of a heater experiment at the Mont Terri underground rock laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Ingeborg, G.; Alheid, H.J. [BGR - Federal Institute for Geosciences and Natural Resources, Hannover (Germany); Jockwerz, N. [Gesellschaft fur Anlagen- und Reaktorsicherheit (GRS) - Final Repository Research Division, Braunschweig (Germany); Mayor, J.C. [ENRESA - Empresa Nacional des Residuos Radioactivos, Madrid (Spain); Garcia-Siner, J.L. [AITEMIN -Asociacion para la Investigacion y Desarrollo Industrial de los Recursos Naturales, Madrid, (Spain); Alonso, E. [CIMNE - Centre Internacional de Metodos Numerics en Ingenyeria, UPC, Barcelona (Spain); Weber, H.P. [NAGRA - National Cooperative for the Disposal of Radioactive Waste, Wettingen (Switzerland); Plotze, M. [ETHZ - Swiss Federal Institute of Technology Zurich, IGT, Zurich, (Switzerland); Klubertanz, G. [COLENCO Power Engineering Ltd., Baden (Switzerland)

    2005-07-01

    The long-term safety of permanent underground repositories relies on a combination of engineered and geological barriers, so that the interactions between the barriers in response to conditions expected in a high-level waste repository need to be identified and fully understood. Co-financed by the European Community, a heater experiment was realized on a pilot plant scale at the underground laboratory in Mont Terri, Switzerland. The experiment was accompanied by an extensive programme of continuous monitoring, experimental investigations on-site as well as in laboratories, and numerical modelling of the coupled thermo-hydro-mechanical processes. Heat-producing waste was simulated by a heater element of 10 cm diameter, held at a constant surface temperature of 100 C. The heater element (length 2 m) operated in a vertical borehole of 7 m depth at 4 to 6 m depth. It was embedded in a geotechnical barrier of pre-compacted bentonite blocks (outer diameter 30 cm) that were irrigated for 35 months before the heating phase (duration 18 months) began. The host rock is a highly consolidated stiff Jurassic clay stone (Opalinus Clay). After the heating phase, the vicinity of the heater element was explored by seismic, hydraulic, and geotechnical tests to investigate if the heating had induced changes in the Opalinus Clay. Additionally, rock mechanic specimens were tested in the laboratory. Finally, the experiment was dismantled to provide laboratory specimens of post - heating buffer and host rock material. The bentonite blocks were thoroughly wetted at the time of the dismantling. The volume increase amounted to 5 to 9% and was thus below the bentonite potential. Geo-electrical measurements showed no decrease of the water content in the vicinity of the heater during the heating phase. Decreasing energy input to the heater element over time suggests hence, that the bentonite dried leading to a decrease of its thermal conductivity. Gas release during the heating period occurred

  7. Natural gamma-ray emitters in clays used for therapeutic purposes

    International Nuclear Information System (INIS)

    Maduar, Marcelo F.; Silva, Paulo S.C. da; Ponciano, Ricardo

    2013-01-01

    The use of minerals for therapeutic purposes is an ancient practice, especially clay minerals topically employed in the therapy of skin disorders and rheumatic processes. In Brazil, an example of such application is the use of a clay-based mineral extracted from a deposit in Peruibe, a resort town in the country southeast. Such mineral has been used both in raw form, after a washing process or as an active component of cosmetics. Currently, a comprehensive characterization of samples from this deposit is underway. As a part of this work, this paper presents preliminary results of the determination of natural radionuclides in samples of this clay and its derived preparations, in order to evaluate the radiological implications of such practice. The raw samples, after preparation, were analyzed by gamma-ray spectrometry. Self-attenuation corrections for the 210 Pb gamma radiation were applied. The radionuclide concentrations in dried samples varied in the ranges: for 226 Ra, 15.3 ± 0.5 to 18.4 ± 0.7 Bq-kg -1 ; for 228 Ra, 31.2 ± 0.5 to 37.8 ± 0.9 Bq-kg -1 ; for 210 Pb, 18 ± 5 to 32 ± 6 Bq-kg -1 ; for 40 K, 373 ± 14 to 454 ± 20 Bq-kg -1 . The concentrations obtained are consistent with previously ones reported for clays. For the cosmetics, none of the target radionuclides were detected above the minimum detectable activities of the counting system, which are 2.5, 2.0, 10 and 20 Bq-kg -1 respectively for 226 Ra, 228 Ra, 210 Pb, and 40 K. An estimation of the effective dose on the skin due to the clay application by a modelling tool, with conservative parameters, led to an effective dose of 0.8 microsievert, indicating that the studied practice causes no significant radiation dose increment to the public. (author)

  8. Radionuclides retention: from macroscopic to microscopic

    International Nuclear Information System (INIS)

    Simoni, E.

    2002-01-01

    In order to determine the radionuclides' sorption constants on solid natural minerals, both thermodynamic and structural investigations, using spectroscopic techniques, are presented. The natural clays, that could be used as engineering barriers in the nuclear waste geological repository, are rather complex minerals. Therefore, in order to understand how these natural materials retain the radionuclides, it is necessary first to perform these studies on simple substrates such as single crystal, oxides and silicates, and then extrapolate the obtained results on the natural minerals. We examine in this paper the sorption processes of the hexavalent uranium on zircon (ZrSiO 4 ) and the trivalent curium on a natural clay (bentonite). The corresponding sorption curves are simulated using the results obtained with the following spectroscopic techniques: laser induced spectro-fluorimetry, X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (EXAFS), diffuse reflectance infrared Fourier transform (DRIFT). (authors)

  9. Laboratory and field tests for radionuclide migration and high flow paths in clay

    International Nuclear Information System (INIS)

    Bourke, P.J.; Jefferies, N.L.; Lineham, T.R.; Nesirky, P.

    1991-01-01

    Two investigations have been undertaken in this programme. The principal investigation was at Culham Laboratory, England, where water flow within the Kimmeridge clay was measured. A subsidiary investigation at SCK/CEN was undertaken at the Underground Research Laboratory SCK/CEN Mol, Belgium, where an in situ measurement of solute transport by diffusion was attempted. The in situ migration experiment at the Underground Research Laboratory at SCK/CEN Mol, Belgium, was unsuccessful, due to problems with the engineering installation. These difficulties caused significant disturbance to the Boom clay which was to be tested. Nevertheless the laboratory test proved the feasibility of the experiment. The field measurements at Culham Laboratory, Oxfordshire, were completed with the flow testing of a very silty clay horizon in the Kimmeridge clay. This layer was proved to be laterally continuous after drilling three exploratory boreholes. The hydraulic conductivity of the layer was ≥ 10 -8 ms -1 and comparative tests in the clay showed the conductivity of the clay to be at least 50 times less. 12 figs

  10. The role of natural organic matter in the migration behaviour of americium in the Boom clay - Part II: analysis of migration experiments

    International Nuclear Information System (INIS)

    Hicks, T.; Bennett, D.; Maes, N.; Wang, L.; Warwick, P.; Hall, T.; Walker, G.; Dierckx, A.

    2005-01-01

    Full text of publication follows: In demonstrating the suitability of Boom Clay as a potential site for the disposal of radioactive waste in Belgium, the role of the relatively high amount of Natural Organic Matter (NOM) present in the Boom Clay on the mobility of critical radionuclides needs investigation. Trivalent actinides and lanthanides form strong complexes with humic substances. Complexation of these trivalent radionuclides with NOM present in the Boom Clay may have opposing effects. If complexed by the aqueous phase (mobile) NOM, radionuclide transport will be governed by the mobility of these dissolved radionuclide-NOM species. If complexed by the solid phase (immobile) NOM, migration will be retarded. One of the aims of the EC projects TRANCOM-Clay and TRANCOM-II was to investigate the role of mobile NOM as radionuclide carrier with the objective of deriving conceptual models that can be implemented in repository performance assessment (PA) models. A separate paper describes the results of column migration experiments involving the transport of 241 Am- 14 C-NOM complexes through Boom Clay cores. This paper describes the transport model, POPCORN, that was developed to describe and evaluate the influence of NOM on radionuclide transport in clay, taking into account attachment/detachment rates of NOM to clay surfaces and the kinetics of RN complexation to, and destabilization from, NOM. The POPCORN model was used to evaluate diffusion experiments involving injection of 14 C-labelled NOM in Boom Clay cores. Model fits were obtained by varying the rates of filtration of NOM by attachment to the surface of the clay matrix. POPCORN was then used to analyse the 241 Am- 14 C-NOM migration experiments. The stability properties of the 241 Am-NOM were characterised by kinetic constants, and good matches to the migration data were achieved for the experiments. The findings suggest that a small sub-population of the original 241 Am-OM is the most stable, and that this

  11. Geophysical monitoring of the EDZ during a gallery excavation in the Opalinus clay of the Mont Terri URL: anomalies of noble gases and self-potential associated with fractures and fluid dynamics in a horizontal borehole

    International Nuclear Information System (INIS)

    Maineult, A.; Mahiouz, K.; Lesparre, N.; Thomas, B.; Lavielle, B.; Nussbaum, C.; Wieczorek, K.; Gibert, D.; Kergosien, B.; Nicollin, F.

    2012-01-01

    Document available in extended abstract form only. The research underground rock laboratory (URL) of Mont Terri (Switzerland) was established in 1996 in a Mesozoic clay-stone formation (Opalinus Clay). It is aimed at studying the hydro-mechanical, thermal, geochemical and geophysical behaviour of argillaceous formations in the context of radioactive waste disposal. The EZ-G experiments were designed to monitor the EDZ evolution. The EZ-G08 experiment started in September 2007 to study the EDZ changes at different time scales during the tunnelling of gallery Ga08 starting from the northern part of the URL toward the end-face of the gallery Ga04. Before the excavation process started, we characterized the petrology and the structural properties of the core of the horizontal, 12-m long borehole BEZ-G5 drilled in the end-face of gallery Ga04 (first 2 meters in the shaly facies, the rest in the sandy facies). We quantified its noble gas content for studying gas transport processes in rocks and connected fracture networks. Depletion in He can be observed in the EDZ and other noble gases can also increase as desaturation processes occur. Inflows of water occurred in the borehole few weeks after its drilling until the junction of galleries Ga08 and Ga04. Water amounts of few litres were commonly released in other boreholes in the URL. We recorded the natural electrical potentials (self-potentials - SP), in BEZ-G5. SP originate from the movement of fluid, the diffusion of concentration or temperature gradients, and are sensitive to any change occurring in them. Borehole BEZ-G5 was equipped with a specific device, on which custom-made electrodes were fixed every 15 cm. The signals showed coherent perturbations during the drilling operations in the boreholes BEZ-G12 and in the end-face of the gallery Ga04. Afterwards, an early, strong but rather smooth increase of a few tens of mV, followed by a very slow decrease of much smallest amplitude, can be observed in some signals

  12. Evaluation of elemental composition of clays from Campos Gerais (MG)

    International Nuclear Information System (INIS)

    Martins, Joao P.M.; Maduar, Marcelo F.; Silva, Paulo S.C da

    2013-01-01

    There are numerous applications given to clays including oil and water adsorbent, ceramic, whitening of beverages, porcelain, waste treatment, organic carrier molecules in cosmetics and pharmaceuticals, support for catalysts. In the pharmaceutical industry, the clays are used as excipients, diluents, desiccants, emulsifiers, to mask undesirable flavors, isotonic agent such as charger and delivery of active substances. These characteristics have contributed to the expansion of the search for applications of clay minerals in the cosmetic industry. The aim of this study was to determine the elemental composition of clays from Campos Gerais, Minas Gerais, with a view to their applicability in the production of cosmetics. The elements As, Ba, Br, Ce, Cl, Co, Cr, Cs, Eu, Fe, Hf, K, La, Lu, Na, Nd, Rb, Sb, Sc, Sm, Ta, Tb, Th,U, Yb and Zn were determined by neutron activation analysis and radionuclide activity concentration of 226 Ra, 228 Ra, 210 Pb and 40 K were determined by gamma spectrometry. It was verified that the activity concentration of radionuclides was in the same concentration as the global average, indicating that these samples do not present a risk of increased radiation exposure. The concentration of most elements determined is less than or equal to the overall mean concentrations, indicated by the values of Continental Upper Crust. (author)

  13. Experimental analysis of plastic materials containing radionuclides for decontamination viability

    International Nuclear Information System (INIS)

    Tazaki, Kazue; Nakano, Mikio; Takehara, Teruaki; Ishigaki, Yasuhito; Nakagawa, Hideaki

    2015-01-01

    After the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident on 11 March, 2011, the high radioactive dosage was found in polluted water for agriculture use at Baba, Haramachi, Minami-Soma, Fukushima Prefecture, Japan. Field experiment for decontamination of water had been studied by using commercial plastic materials. The agricultural water comes from Tetsuzan dam is full of radioactive-contaminated water. Experimental analysis showed that the plastic materials can take up radioactive elements for several months soaked in the polluted agricultural water. The quantitative analyses using X-ray fluorescence analysis, Ge semiconductor and scanning electron microscopy equipped with energy dispersive X-ray spectrometer (SEM-EDS), revealed the detection of the radionuclides on the plastic materials with diatom and clays. The results suggest the adsorption of radionuclides on the surface of plastic materials due to FDNPP accident. The plastic materials associated with clays and diatoms could be stronger carriers of radionuclides in the polluted water. Adherence of diatoms to the plastic fiber in the water for 7 months suggested that some plastic materials were taking up heavy metals (Zn, Ba, Pb, Sb) with radioactive elements (Cs etc.). Mechanisms by which radioactive pollutants and microorganisms are adsorbed onto and desorbed from clays at aqueous interface can be understood by combining chemical analysis with electron microscopy observation. (author)

  14. Natural analogues and evidence of long-term isolation capacity of clays occurring in Italy

    International Nuclear Information System (INIS)

    Benvegnu, F.; Brondi, A.; Polizzano, C.

    1988-01-01

    This work concerns the results of the studies conducted at many sites in Italy aimed at collecting information on natural evidences of the isolation capacity of clay. Field observations allow to get the opportunity to know directly or infer the evolutive geological processes which are of concern for the waste disposal problems. As a major advantage such observations concern natural phenomena acting at the same, or at a greater, time-space scale involved in the geological disposal of wastes. The explored situations regard the secondary permeability of clay, detected by means of natural tracers (Hg, He, hydrothermal and geothermal fluids, ....) at the ground surface or directly studied in deep civilian tunnels. Another treated topic is the meaning of the oxido-reduction front as a control factor of the physico-chemical environment of clay as well as of the radionuclides migration. The mechanical and thermal effects which accompany the intrusion of a subvolcanic body within clay represent an extreme worst case for a comparison of the effects on clay due to heat developed by radionuclide decay. Finally the case of a fossil forest maintained almost inaltered by the clay cover for over 1,500,000 years is described. All the results of the geological researches point univocally to an almost total and long lasting isolation capacity of clay formations

  15. Mass Transfer and Porous Media (MTPM)

    Energy Technology Data Exchange (ETDEWEB)

    Rotenberg, B.; Marry, V.; Malikova, N.; Vuilleumier, R.; Giffaut, E.; Turq, P.; Robinet, J.C.; Diaz, N.; Sardini, P.; Goutelard, F.; Menut, D.; Parneix, J.C.; Sammartino, S.; Pret, D.; Coelho, D.; Jougnot, D.; Revil, A.; Boulin, P.F.; Angulo-Jaramillo, R.; Daian, J.F.; Talandier, J.; Berne, P.; Cochepin, B.; Trotignon, L.; Bildstein, O.; Steefel, C.; Lagneau, V.; Van der Lee, J.; Birchall, D.J.; Harrington, J.F.; Noy, D.J.; Sellin, P.; Bildstein, O.; Piault, E.; Trotignon, L.; Montarnal, P.; Deville, E.; Genty, A.; Le Potier, C.; Imbert, C.; Semete, P.; Desgree, P.; Fevrier, B.; Courtois, A.; Touze, G.; Sboui, A.; Roberts, J.E.; Jaffre, J.; Glaus, M.A.; Rosse, R.; Van Loon, L.R.; Matray, J.M.; Parneix, J.C.; Tinseau, E.; Pret, D.; Mayor, J.C.; Ohkubo, T.; Kikuchi, H.; Yamaguchi, M.; Alonso, U.; Missana, T.; Garcia-Gutierrez, M.; Patelli, A.; Siitari-Kauppi, M.; Leskinen, A.; Rigato, V.; Samper, J.; Dewonck, S.; Zheng, L.; Yang, Q.; Naves, A.; Dai, Z.; Samper, J.; Wolfsberg, A.; Levitt, D.; Cormenzana, J.L.; Missana, T.; Mingarro, M.; Schampera, B.; Dultz, S.; Riebe, B.; Samper, J.; Yang, Q.; Genty, A.; Perraud, D.; Poller, A.; Mayer, G.; Croise, J.; Marschall, P.; Krooss, B.; Matray, J.M.; Tanaka, T.; Vogel, P.; Lavanchy, J.M.; Enssle, C.P.; Cruchaudet, M.; Dewonck, S.; Descostes, M.; Blin, V.; Radwan, J.; Poinssot, C.; Mibus, J.; Sachs, S.; Devol-Brown, I.; Motellier, S.; Tinseau, E.; Thoby, D.; Marsal, F.; DeWindt, L.; Tinseau, E.; Pellegrini, D.; Bauer, A.; Fiehn, B.; Marquardt, Ch.; Romer, J.; Gortzen, A.; Kienzler, B

    2007-07-01

    This session gathers 48 articles (posters) dealing with: interlayer / micro-pore exchange of water and ions in clays: a molecular dynamics study; the multi-scale characterisation of mineral and textural spatial heterogeneities in Callovo-Oxfordian argilite and its consequence on solute species diffusion modelling; the diffusion of ions in unsaturated clay rocks: Theory and application to the Callovo- Oxfordian argillite; the porous media characterization with respect to gas transfer in Callovo Oxfordian argillite; the predictions on a 2-D cementation experiment in porous medium: intercomparison on the Comedie project; the large-scale gas injection test (LASGIT) at the Aespoe hard rock laboratory in Sweden; simulating the geochemical coupling between vitrified waste, canister and near-field on the alliances platform; toward radionuclide transport calculations on whole radioactive waste disposal with CAST3M platform; the experimental study of the water permeability of a partially saturated argillite; a mixed hexahedral finite elements for Darcy flow calculation in clay porous media; the diffusive properties of stainless steel filter discs before and after use in diffusion experiments with compacted clays; the structural organization of porosity in the Opalinus clay at the Mont Terri Rock Laboratory under saturated and unsaturated conditions; the evaluation of pore structure in compacted saturated Bentonite using NMR relaxometry; diffusion coefficients measurement in consolidated clays: a combination of micro-scale profiling and solid pore structure analyses; the numerical interpretation of in-situ DIR diffusion experiments on the Callovo- Oxfordian clay at the Meuse/Haute-Marne URL the identification of relative conductivity models for water flow and solute transport in unsaturated compacted Bentonite; diffusion experiments in Callovo- Oxfordian clay from the Meuse/Haute-Marne URL, France: experimental setup and data analyses; the transport in organo

  16. First assessment of the pore water composition of Rupel Clay in the Netherlands and the characterisation of its reactive solids

    NARCIS (Netherlands)

    Behrends, T.; Veen, I. van der; Hoving, A.; Griffioen, J.

    2016-01-01

    The Rupel Clay member in the Netherlands largely corresponds to the Boom Formation in Belgium, and this marine, clay-rich deposit is a potential candidate to host radioactive waste disposal facilities. Prediction of the speciation of radionuclides in Rupel Clay pore water and their retardation by

  17. Physicochemical characteristics of radionuclides associated with sediment from a contaminated fresh water stream

    International Nuclear Information System (INIS)

    Murdock, R.N.; Hemingway, J.D.; Jones, S.R.

    1993-01-01

    The relationships between concentrations of 241 Am, 137 Cs and 239,240 Pu and sediment particle size and geochemical species were examined for sediments taken from a freshwater stream contaminated by radioactive effluent from a low-level waste disposal site. Both 137 Cs and gross alpha concentrations were strongly correlated with the silt and clay content of the sediment, radionuclide concentrations following the order: clay>silt>sand. Positive correlations with organic content were also observed for both 137 Cs and gross alpha activity. These relationships, together with erosional and depositional characteristics obtained from streamflow data, largely explained the spatial variation in radionuclide concentrations in streambed sediments. Sequential extraction experiments showed that 137 Cs was mostly ''irreversibly'' bound to sediment particle, principally illitic clays, whereas 241 Am and 239,240 Pu were associated primarily with organic and oxy-hydroxy species within the sediments. (Author)

  18. Numerical analysis of thermo-hydro-mechanical (THM) processes in the clay based material

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xuerui

    2016-10-06

    conductivity on the degree of water saturation, the dependency of the thermal effects on the water retention behaviour, and the dependency of the effects of the pore pressure variation on the permeability and the anisotropic swelling/shrinkage behaviour have been intensively analysed and the corresponding numerical models to consider those coupling effects have been developed. The developed numerical model has been applied to simulate the laboratory and in situ heating experiments on the bentonite and clay rock at different scales. Firstly the laboratory heating experiment on Callovo-Oxfordian Clay (COX) and the laboratory long-term heating and hydration experiment on MX80 pellets were simulated. Based on the knowledge from the numerical analysis of the laboratory experiments, a 1:2 scale in situ heating experiment of an integrated system of the bentonite engineered barrier system (EBS) in the Opalinus Clay host rock was simulated. All the relevant operation phases were considered in the modelling. Besides, the modelling was extended to 50 years after the heat shut-down with the aim of predicting the long-term behaviours. Additionally, variation calculations were carried out to investigate the effects of the storage capacity of the Opalinus Clay on the thermally induced hydraulic response. In the long-term modelling, the effects of different saturated water permeabilities of buffer material on the resaturation process were analysed. Based on the current researches and model developments, the observed THM behaviours of the bentonite buffer and the clay rock, that is, the measured evolution of temperature, pore pressure, humidity, swelling pressure, and so on in the laboratory and in situ experiments can be reproduced and interpreted well. It is proved that by using both a non-isothermal multiphase flow model and a non-isothermal Richards flow model combined with the corresponding thermal and mechanical models, the major THM behaviours can be captured. It is validated that the

  19. Numerical analysis of thermo-hydro-mechanical (THM) processes in the clay based material

    International Nuclear Information System (INIS)

    Wang, Xuerui

    2016-01-01

    conductivity on the degree of water saturation, the dependency of the thermal effects on the water retention behaviour, and the dependency of the effects of the pore pressure variation on the permeability and the anisotropic swelling/shrinkage behaviour have been intensively analysed and the corresponding numerical models to consider those coupling effects have been developed. The developed numerical model has been applied to simulate the laboratory and in situ heating experiments on the bentonite and clay rock at different scales. Firstly the laboratory heating experiment on Callovo-Oxfordian Clay (COX) and the laboratory long-term heating and hydration experiment on MX80 pellets were simulated. Based on the knowledge from the numerical analysis of the laboratory experiments, a 1:2 scale in situ heating experiment of an integrated system of the bentonite engineered barrier system (EBS) in the Opalinus Clay host rock was simulated. All the relevant operation phases were considered in the modelling. Besides, the modelling was extended to 50 years after the heat shut-down with the aim of predicting the long-term behaviours. Additionally, variation calculations were carried out to investigate the effects of the storage capacity of the Opalinus Clay on the thermally induced hydraulic response. In the long-term modelling, the effects of different saturated water permeabilities of buffer material on the resaturation process were analysed. Based on the current researches and model developments, the observed THM behaviours of the bentonite buffer and the clay rock, that is, the measured evolution of temperature, pore pressure, humidity, swelling pressure, and so on in the laboratory and in situ experiments can be reproduced and interpreted well. It is proved that by using both a non-isothermal multiphase flow model and a non-isothermal Richards flow model combined with the corresponding thermal and mechanical models, the major THM behaviours can be captured. It is validated that the

  20. Fixation of radioactive waste by reaction with clays: progress report

    International Nuclear Information System (INIS)

    Delegard, C.H.; Barney, G.S.

    1975-07-01

    Reactions of clay with Hanford-type radioactive wastes (liquids, salt cake, and sludge) were studied as a means of immobilization of radionuclides contained in the waste. Products of these reactions were identified as the crystalline sodium aluminosilicates, cancrinite and nepheline. Radionuclides are entrapped in these crystalline minerals. Conceptual flow diagrams for conversion of high-salt wastes to cancrinite and nepheline were defined and tested. The mineral products were evaluated for use as forms for long-term storage of radioactive waste

  1. Influence of Iltization on the Ion-sorbing Capacity of Smectitic Clay

    International Nuclear Information System (INIS)

    Lee, Jae Owan; Cho, Won Jin

    2008-01-01

    A high-level waste(HLW) repository uses smectitic clay as a buffer material to inhibit the penetration of groundwater and to retard the release of radionuclides from the radioactive wastes to the surrounding environment. However, when the smectitic clay is exposed to an elevated temperature due to radioactive decay heat and geochemical conditions for a long time, its physicochemical and mineralogical properties may be degradated and thus lose its barrier functions. It has been known in literature that the degradation of these properties of the smectitic clay occurs by a illitization in which the smectite transforms into illite. Therefore, an understanding of the illitization is essential to evaluate the long-term barrier performance of smectitic clay for the buffer of a HLW repository. This paper will carry out hydrothermal reaction tests with domestic smectitic clay which will be favorably considered for the buffer material of a Korean HLW repository, and also investigate the influence of illization on the ion-sorbing capacity of the smectitic clay

  2. Particle size and radionuclide levels in some west Cumbrian soils

    International Nuclear Information System (INIS)

    Livens, F.R.

    1988-01-01

    Four west Cumbrian soils of contrasting types, together with an estuarine silt sample, were separated into different particle size fractions by a combination of sieving and settling techniques. These sub-samples were analysed by quantitative gamma-ray spectrometry for several nuclides, principally 137 Cs, 106 Ru and 241 Am, followed by chemical separation and alpha spectrometric determination of 238,239,240 Pu. A simple empirical method of correction for differing sample sizes, and hence counting geometries, was developed for gamma spectrometry and found to give good results. The radionuclides were concentrated into the finer size fractions, with clay-sized ( 137 Cs from 3 to 35 times. The enhancement was greatest for all radionuclides in a sandy soil with a very low clay content (0.2% by weight) and it was found that, as the abundance of fine particles increased, so the concentration effect decreased. No evidence was found for a simple relationship between organic content and radionuclide activity, although the organic matter does have some effect. 17 refs.; 3 figs.; 6 tabs

  3. Predicting the uptake of Cs, Co, Ni, Eu, Th and U on argillaceous rocks using sorption models for illite

    International Nuclear Information System (INIS)

    Marques Fernandes, Maria; Vér, Nóra; Baeyens, Bart

    2015-01-01

    Highlights: • Contaminant retention in argillaceous rocks controlled by sorption on clay minerals. • Cs, Ni, Co, Eu, Th and UO 2 sorption isotherm measurements on Boda and Opalinus Clay. • Boda and Opalinus Clay exhibit different mineralogies and porewater compositions. • Blind predictions using quasi-mechanistic sorption models developed for illite. • Good agreement between measurements and blind predictions. - Abstract: Reliable predictions of radiocontaminant migration are a requirement for the establishment of radioactive waste repositories. Parametrization of the necessary sorption models seems to be, however, extremely challenging given the multi-mineralic composition of the lithosphere. In this study it is shown for two argillaceous rocks – Boda and Opalinus Clay relevant for the Hungarian and Swiss repository concepts, respectively – that this task can be substantially simplified by taking into account only the most sorptive mineral fraction, namely the 2:1 clay minerals illite and illite/smectite mixed layers. Two different models were required to blind predict the sorption isotherms of Cs, Co, Ni, Eu, Th and UO 2 measured on the two clay rock samples in a synthetic porewater. Cs sorption was modelled with the generalised Cs (GCs) sorption model and the sorption of the other cations with the 2site protolysis non electrostatic surface complexation and cation exchange (2SPNE SC/CE) model. The 2SPNE SC/CE model for illite was extended with surface complexation reactions on weak sites for Co, Ni, Eu, UO 2 and on strong sites for Eu-carbonato complexes. Complementary to the sorption measurements and modelling, extended X-ray absorption fine structure (EXAFS) spectroscopy was used to probe the retention mechanism of Ni on illite, Boda and Opalinus Clay at higher loadings. The reliable blind predictions of the selected metal cations, which are representative for monovalent alkaline metals, divalent transition metals, lanthanides, and trivalent

  4. A Preliminary Study of Two Different Clays for Separation of Some Artificial Radionuclides in Stimulated Waste

    International Nuclear Information System (INIS)

    Lasheen, Y.F.; Seliman, A.F.; Shehata, F.A.; Youssef, M.A.; Abo-Aly, M.

    2016-01-01

    The removal of long lived radionuclides, such as 134 Cs(I), 133 Ba(II), 90 Sr(II) and 152 Eu(III) by bentonite (W-Bent) and kaolin (S-Kaol) was studied as a function of different parameters using a batch technique. The results showed that the optimum ph was selected to be 6. Kinetically in case of W-Bent, the adsorption is heterogeneous for 134 Cs, 133 Ba and homogenous for 90 Sr and 152 Eu. The distribution coefficient values follow the order of 1 '5 2 Eu> 134 Cs> 90 Sr> 133 Ba. Langmuir, Freundlish, Dubinin-Raduskevich (D-R) and Temkin isotherm models were applied. According to the D-R model, W-Bent showed a high affinity to 152 Eu with a maximum capacity (q m = 0.43 mol/Kg) in comparison with S-Kaol (q m =0.023 mol/Kg). Also according to D-R model the adsorption energy (E> 8.0 KJ mol -1 ) that means the adsorption reaction is expected to be chemisorption. Finally both clays are cost-effective sorbent materials with an excellent adsorption capacity, but some surface modification for S-Kaol is recommended to be more effective than its natural form

  5. Chemical and mineralogical aspects of clay-salt slimes of 'Belaruskali' using for the preparation of nano-structured sorbents of radionuclides

    Energy Technology Data Exchange (ETDEWEB)

    Maskalchuk, L.; Baklay, A.; Leontieva, T. [Joint Institute for Power and Nuclear Research - Sosny, NAS of Belarus, Minsk, P.O.Box 119, 220109 (Belarus)

    2016-07-01

    n the context of intensive nuclear-power engineering development there is an urgent need to solve a range of technological and environmental challenges associated with generation, treatment and disposal of radioactive waste. In this regards, the problems of radioactive waste safe management and rehabilitation of radioactively contaminated soils in the result of the radiation accidents at the Chernobyl and Fukushima Daiichi NPPs are especially significant. Concerning that, investigation of effective and low cost sorption materials for radionuclides immobilization has a special relevance. In order to solve the above mentioned problems, it is supposed to develop a resource-saving technology for production of multi-purpose nano-structured sorbents of radionuclides ({sup 137}Cs, {sup 90}Sr) with predetermined physicochemical properties based on the waste of potash industry - clay-salt slimes (CSS) of the JSC 'Belaruskali'. The performed research has shown that the CSS samples have a high fixing ability in relation to {sup 137}Cs. The main sorption-active minerals in CSS are illite and montmorillonite. The degree of sorption is 99.6%, K{sub d} is 1.2*10{sup 5} l/kg, RIP(K) is 6343 mmol/kg. The modification of the S-1 sample allows to enlarge the content of sorption-active minerals tentatively in 3.5 times, thereafter RIP(K) for the S-3 sample may be significantly increased. Based on the obtained experimental data, CSS of the JSC 'Belaruskali' can be estimated as a perspective initial material for production of multi-purpose nano-structured sorbents of radionuclides. (authors)

  6. Plant uptake of radionuclides and rhizosphere factors

    International Nuclear Information System (INIS)

    Arie, Tsutomu; Gouthu, S.; Ambe, Shizuko; Yamaguchi, Isamu; Hirata, Hiroaki

    1999-01-01

    Influence of soil factors such as nuclide availability, pH, organic carbon, cation exchange capacity (CEC), exchangeable cations (Ca 2+ , Mg 2+ , and K + ), phosphate absorption coefficient (PAC), physical composition of soil (coarse sand, fine sand, silt, and clay), soil texture, and rhizosphere microbes on uptake of radionuclides by plants are studied. (author)

  7. Environmental degradation of Opalinus Clay with cyclic variations in relative humidity

    Science.gov (United States)

    Wild, Katrin; Walter, Patric; Madonna, Claudio; Amann, Florian

    2016-04-01

    Clay shales are considered as favorable host rocks for nuclear waste repositories due to their low permeability, high sorption capacity and the potential for self-sealing. However, the favorable characteristics of the rock mass may change during tunnel excavation. Excavation is accompanied by stress redistribution and the development of an excavation damage zone. Furthermore, unloading and exposure to atmospheric conditions with a lower relative humidity (RH) causes desaturation of the rock mass close to the tunnel. This leads to shrinkage and the formation of desiccation cracks. During the open drift stage, seasonal atmospheric changes, especially RH variations, may alter the rock mass and influence the long-term crack evolution. This contribution discusses the influence of RH variation on the mechanical behavior of OPA. A series of specimens were exposed to short-term and long-term, stepwise cyclic RH variations between about 60 and 95% at constant temperature. Strains were measured using strain gauges to monitor the volumetric response during RH cycles. After each applied RH cycle, Brazilian tensile strength (BTS) tests were performed to identify whether there is a change in tensile strength due to environmental damage caused by the change in RH. Swelling and shrinkage of the specimens accompanied by irreversible volumetric expansion was observed as a consequence of the exposure to RH cycles. However, the irreversible strain was limited to the direction normal to bedding suggesting that internal damage is restricted along the bedding planes. No significant effect of cyclic RH variations on the BTS of the specimens was observed. The strength parallel to bedding remained constant over several cycles while the strength normal to bedding shows a slightly decreasing trend after 2 cycles. Furthermore, the water retention characteristics of the specimens were not altered significantly during stepwise RH cycling as the evolution of the water content was reversible

  8. Role of soil micro-organisms in the sorption of radionuclides in organic systems

    International Nuclear Information System (INIS)

    Parekh, N.R.; Potter, E.D.; Poskitt, J.M.; Dodd, B.A.; Sanchez, A.

    2004-01-01

    Although the fraction of radionuclides linked to soil organic matter and soil microorganisms may be relatively small when compared to the amount bound to the mineral constituents, (mostly irreversibly bound), this fraction is of great importance as it remains readily exchangeable and is thus available for plant uptake. Many studies have measured the uptake of radionuclides by organic soils but the role of soil micro-organisms may have been masked by the presence of even small amounts of clay minerals occurring in these soils. We have carried out a series of experiments using a biologically active, 'mineral-free' organic soil produced under laboratory conditions, to determine the potential of soil micro-organisms to accumulate radionuclides Cs-134 and Sr-85. Biological uptake and release was differentiated from abiotic processes by comparing experimental results with inoculated and non-inoculated sterile organic material. We have investigated the role of different clay minerals, competing potassium and calcium ions, and changes in temperature on the sorption of Cs and Sr isotopes. The results from studies so far show conclusively that living components of soil systems are of primary importance in the uptake of radionuclides in organic material, microorganisms also influence the importance of chemical factors (e.g. adsorption to clay minerals) which may play a secondary role in these highly organic systems. In further experiments we hope to define the precise role of specific soil micro-organisms in these organic systems. (author)

  9. Movement of radionuclides through unsaturated soils

    International Nuclear Information System (INIS)

    de Sousa, F.N.C.

    1985-01-01

    The advantages of the disposal of low-level radioactive wastes in the unsaturated zone above the fluctuations of the water table have been recognized for some time. However, most the numerical models used to simulate the environmental impact of a shallow land burial site assume that the soils surrounding the waste forms are saturated; this assumption may lead, in many cases, to unrealistic large leach and water flow rates. The main purpose of this study was the development of a procedure which could give a reliable prediction on the movement of radionuclides from shallow land burial sites located in the unsaturated zone. In order to accomplish this objective three different soils having different sand, silt, and clay fractions were selected and characterized. These soils were then used to fill a number of flow columns that were used in tests designed to provide input data for the flow and transport models. A one-dimensional finite element model was developed in order to simulate the water flow and radionuclide transport through unsaturated soils. The results obtained showed that the model accurately described the transport of radionuclides through saturated-unsaturated soils. Simulations were done, for all three soils, involving different degrees of soil saturation, and the results showed that assuming the soils are always saturated may lead to nuclide transport times which are orders of magnitude larger than the real ones, depending on the clay percentage present in the soil

  10. The role of particulates in radionuclide transport

    International Nuclear Information System (INIS)

    Vilks, P.; Bachinski, D.B.; Vandergraaf, T.T.

    1991-01-01

    The colloid program at AECL Research is focused on characterizing natural particles in groundwater to evaluate their potential role in radiocolloid formation and to form a database for particle migration studies. The main objective of this program has been the study of colloids (1 to 450 nm) and suspended particles (> 450 nm) in fractured granites and sandstone in various locations in Canada and Switzerland. Groundwater particles were found to consist of clay minerals, micas, quartz, feldspar, iron-silica oxides and organic material. In groundwaters from granite, sandstone and clay-rich rock colloid concentrations were less than 5 mg/L. Some of these groundwaters may contain up to 260 mg/L of suspended particles. However, these particles are not expected to be mobile under the natural flow regimes of deep groundwaters. Provided radiocolloid formation is reversible, it is shown that the colloid concentrations observed in groundwaters from granites will have a negligible effect on radionuclide transport even when making the conservative assumption that these particles travel with the velocity of groundwater. For the case of irreversible radiocolloid formation, an equation is presented to calculate the fraction of total radionuclides in the geosphere which will form radiocolloids. The significance of these radiocolloids will depend upon the total amount of radionuclides released to the geosphere and on particle migration properties. (author)

  11. Fracture transmissivity as a function of normal and shear stress: first results in Opalinus Clay

    International Nuclear Information System (INIS)

    Cuss, R.J.; Milodowski, A.; Noy, D.J.; Harrington, J.F.

    2010-01-01

    Document available in extended abstract form only. Rock-mass failure around openings is usually observed in the form of a highly complex fracture network (EDZ), which is heterogeneous in distribution around a circular tunnel opening because of the heterogeneous stress distribution. The orientation of stress with respect to the fracture network is known to be important. The complex heterogeneous stress trajectory and heterogeneous fracture network results in a broad range of stresses and stress directions acting on the open fracture network. During the open stage of a repository, stress will slowly alter as shear movements occur along the fractures, as well as other time-dependent phenomena. As the repository is back filled, the stress field is further altered as the backfill settles and changes volume because of re-saturation. Therefore, a complex and wide ranging stress regime and stress history will result. In a purely mechanical sense, fracture transmissivity is a function of normal stress, shear stress, and fracture aperture. The Selfrac test from Mont Terri showed the change in transmissivity with effective normal stress. This work showed that fracture transmissivity decreased with increasing normal load and that an effective normal stress of 2.5 MPa is sufficient to yield a transmissivity similar to that seen in intact Opalinus clay (OPA). Therefore fracture closure because of normal stresses has been proven to be a quite efficient mechanism in OPA. A new shear rig was designed to investigate the detail of fracture transmissivity in OPA. The experimental configuration uses two prepared blocks that are 60 x 60 mm in size and approximately 20 mm thick. The first test sample had machine ground surfaces in contact with each other, with pore fluid being delivered through the centre of the top block directly to the fracture surface. The experimental programme included two distinct stages. In the first normal load was altered to investigate fracture transmissivity

  12. Fully coupled modeling of radionuclide migration in a clayey rock disturbed by alkaline plume

    International Nuclear Information System (INIS)

    Pellegrni, D.; Windt, L. de; Lee, J.V.D.

    2002-03-01

    The disposal of radioactive wastes in clayey formations may require the use of large amounts of concrete and cement as a barrier to minimize corrosion of steel containers and radionuclide migration and for supporting drifts and disposal vaults. In this context, reactive transport modeling of the interactions between cement or concrete and the argillaceous host rock aims at estimating the evolution in time of the containment properties of the multi-barriers system. The objectives of the paper are to demonstrate that integrating radionuclides migration in the modeling of strongly coupled geochemical processes of cement-clay stone interactions is feasible and that it represents an efficient way to assess the sensitivity and modification of the classical Kd and solubility parameters with respect to the chemical evolutions. Two types of modeling are considered in the paper: i): calculation of intrinsic solubility limits and Kd values backing up on the results of modeling of cement/clay stone interactions (radionuclides are assumed to be present over the whole domain at any time whatever the scenario), ii) full mechanistic modeling which explicitly introduces radionuclides in the calculation with ad hoc assumptions on radionuclide inventory, canister failure, migration pathway, etc. The reactive transport code HYTEC, based on the geochemical code CHESS, is used to simulate both the cement-clay stone interaction processes and the radionuclide migration in 1-D and 2-D configurations. Convective/dispersive and diffuse transport can be simulated for solutes and colloids. A wide range of processes such as aqueous chemistry, redox, dissolution/precipitation, surface complexation and ion exchange can be modeled at equilibrium or with kinetic control. In addition, HYTEC is strongly coupled, i.e. the hydrology (flow and diffusion) may change when mineral precipitation or dissolution changes the local porosity. (authors)

  13. The effect of organic matter in clay sealing materials on the performance of a nuclear fuel waste disposal vault

    International Nuclear Information System (INIS)

    Oscarson, D.W.; Stroes-Gascoyne, S.; Cheung, S.C.H.

    1986-12-01

    The potential effect of organic matter in clay sealing materials on the performance of a nuclear fuel waste disposal vault was examined. The available data indicate that the engineering properties of clays are not significantly affected by the relatively low levels of organic matter (< 1.2 wt.%) present in the clay sealing materials. Complexing of radionuclides by organic substances that are released from the clay sealing materials or produced by microorganisms will likely inhibit rather than promote radionuclide mobility in the compacted sealing materials because of the relatively large size of organic complexing species. Decreasing the level of organic matter in the clay sealing materials will not eliminate microorganisms, and perhaps not decrease their numbers significantly, because chemolithotrophic microorganisms (microorganisms that utilize inorganic forms of C) will be present in a disposal vault. Furthermore, an examination of the nutrient budget in a disposal vault indicates that N, rather than C, will likely be the limiting nutrient for microbial growth. Finally, there is not suitable, proven method for decreasing the level of organic matter in the large amounts of clay needed to seal a vault. It is concluded that the organic matter present in the clay sealing material will not adversely affect the performance of a disposal vault

  14. Chemical buffering capacity of clay rock

    International Nuclear Information System (INIS)

    Beaucaire, C.; Pearson, F.J.; Gautschi, A.

    2004-01-01

    The long-term performance of a nuclear waste repository is strongly dependent on the chemical properties of the host rock. The host rock establishes the chemical environment that determines such important performance attributes as radionuclide solubilities from the waste and the transport rates from the repository to the accessible environment. Clay-rich rocks are especially favourable host rocks because they provide a strong buffering capacity to resist chemical changes prompted either internally, by reactions of the waste itself and emplacement materials, or externally, by changes in the hydrologic systems surrounding the host rock. This paper will focus on three aspects of the stability of clay-rich host rocks: their ability to provide pCO 2 and redox buffering, and to resist chemical changes imposed by changes in regional hydrology and hydro-chemistry. (authors)

  15. Plant uptake of radionuclides and rhizosphere factors

    Energy Technology Data Exchange (ETDEWEB)

    Arie, Tsutomu; Gouthu, S.; Ambe, Shizuko; Yamaguchi, Isamu [Institute of Physical and Chemical Research, Wako, Saitama (Japan); Hirata, Hiroaki

    1999-03-01

    Influence of soil factors such as nuclide availability, pH, organic carbon, cation exchange capacity (CEC), exchangeable cations (Ca{sup 2+}, Mg{sup 2+}, and K{sup +}), phosphate absorption coefficient (PAC), physical composition of soil (coarse sand, fine sand, silt, and clay), soil texture, and rhizosphere microbes on uptake of radionuclides by plants are studied. (author)

  16. Thermal effects on clay rocks for deep disposal of high-level radioactive waste

    Directory of Open Access Journals (Sweden)

    Chun-Liang Zhang

    2017-06-01

    Full Text Available Thermal effects on the Callovo-Oxfordian and Opalinus clay rocks for hosting high-level radioactive waste were comprehensively investigated with laboratory and in situ experiments under repository relevant conditions: (1 stresses covering the range from the initial lithostatic state to redistributed levels after excavation, (2 hydraulic drained and undrained boundaries, and (3 heating from ambient temperature up to 90 °C–120 °C and a subsequent cooling phase. The laboratory experiments were performed on normal-sized and large hollow cylindrical samples in various respects of thermal expansion and contraction, thermally-induced pore water pressure, temperature influences on deformation and strength, thermal impacts on swelling, fracture sealing and permeability. The laboratory results obtained from the samples are consistent with the in situ observations during heating experiments in the underground research laboratories at Bure and Mont-Terri. Even though the claystones showed significant responses to thermal loading, no negative effects on their favorable barrier properties were observed.

  17. The UK contribution to the CEC PACOMA Project: far-field modelling of radioactive waste disposal in clay

    International Nuclear Information System (INIS)

    Winters, K.H.; Jackson, C.P.; Clark, C.M.

    1990-06-01

    This document describes a study of groundwater flow and radionuclide migration in the far field of a hypothetical repository located in the clay beneath Harwell Laboratory. The work forms part of the assessment of the radiological impact of disposal in a clay formation, carried out as the UK contribution to the CEC PACOMA project. (Author)

  18. The long term geochemical evolution of the nearfield of the HLW repository

    Energy Technology Data Exchange (ETDEWEB)

    Bradbury, M. H.; Berner, U.; Curti, E.; Hummel, W.; Kosakowski, G.; Thoenen, T.

    2014-11-15

    The work presented in this report focuses on the spatial and temporal evolution of the near-field of the high level radioactive waste repository situated in the Opalinus Clay formation. The major components of the near-field of such a repository are spent fuel, vitrified high-level waste, canisters (assumed for the purposes of the present report to be made of carbon steel), compacted bentonite and a concrete liner. Over the one million year time period considered in safety analysis, these components will chemically interact with one another and potentially change their retention characteristics. As a starting reference point the 'initial' (unreacted) states of the Opalinus Clay, bentonite, concrete liner (mineralogies and water chemistries) and the canister are briefly described. The main processes considered to influence the evolution of the repository in time and space, and which often operate over different time scales, are: interactions of the concrete tunnel liner with compacted bentonite and Opalinus Clay, temperature gradients caused by the heat generating high level waste, mineralogical changes to the compacted bentonite through interactions with the corrosion products of the iron canisters, and finally, the dissolution of the spent fuel and vitrified high-level waste. The consequences of these processes (as a function of time) on the long term barrier performance of the near-field have been estimated, particularly with respect to radionuclide solubilities and the sorption, diffusion and swelling characteristics of the bentonite. The main conclusions drawn are as follows: The alteration depth into the bentonite due to the interaction with the concrete liner (assumed to be 15 cm thick) is likely to be much less than 13 cm over a one million year time scale, with the main reaction products being clays (illite), hydroxides, carbonates, calcium silicate hydrates, and aluminosilicates. The swelling pressure and the sorption capacity of the bentonite in

  19. The long term geochemical evolution of the nearfield of the HLW repository

    International Nuclear Information System (INIS)

    Bradbury, M. H.; Berner, U.; Curti, E.; Hummel, W.; Kosakowski, G.; Thoenen, T.

    2014-11-01

    The work presented in this report focuses on the spatial and temporal evolution of the near-field of the high level radioactive waste repository situated in the Opalinus Clay formation. The major components of the near-field of such a repository are spent fuel, vitrified high-level waste, canisters (assumed for the purposes of the present report to be made of carbon steel), compacted bentonite and a concrete liner. Over the one million year time period considered in safety analysis, these components will chemically interact with one another and potentially change their retention characteristics. As a starting reference point the 'initial' (unreacted) states of the Opalinus Clay, bentonite, concrete liner (mineralogies and water chemistries) and the canister are briefly described. The main processes considered to influence the evolution of the repository in time and space, and which often operate over different time scales, are: interactions of the concrete tunnel liner with compacted bentonite and Opalinus Clay, temperature gradients caused by the heat generating high level waste, mineralogical changes to the compacted bentonite through interactions with the corrosion products of the iron canisters, and finally, the dissolution of the spent fuel and vitrified high-level waste. The consequences of these processes (as a function of time) on the long term barrier performance of the near-field have been estimated, particularly with respect to radionuclide solubilities and the sorption, diffusion and swelling characteristics of the bentonite. The main conclusions drawn are as follows: The alteration depth into the bentonite due to the interaction with the concrete liner (assumed to be 15 cm thick) is likely to be much less than 13 cm over a one million year time scale, with the main reaction products being clays (illite), hydroxides, carbonates, calcium silicate hydrates, and aluminosilicates. The swelling pressure and the sorption capacity of the bentonite in this

  20. The connectivity of pore space in mudstones: insights from high-pressure Wood's metal injection, BIB-SEM imaging, and mercury intrusion porosimetry

    NARCIS (Netherlands)

    Klaver, J.; Hemes, S.; Houben, M.; Desbois, G.; Radi, Z.; Urai, J.L.

    2015-01-01

    Study of the pore space in mudstones by mercury intrusion porosimetry is a common but indirect technique and it is not clear which part of the pore space is actually filled with mercury. We studied samples from the Opalinus Clay, Boom Clay, Haynesville Shale, and Bossier Shale Formations using

  1. Geochemistry and mineralogy

    Energy Technology Data Exchange (ETDEWEB)

    Plecas, I.; Dimovic, S.; Orta, M.M.; Alba, M.D.; Alvero, R.; Becerro, A.I.; Castro, M.A.; Chain, P.; Escudero, A.; Naranjo, M.; Pavon, E.; Trillo, J.M.; Vejsada, J.; Vokal, A.; Zadvernyuk, H.P.; Fedorenko, Y.G.; Zlobenko, B.P.; Koromyslichenko, T.I.; Battaglia, S.; Cervelli, M.; Millot, R.; Girard, J.P.; Missana, T.; Garcia-Gutierrez, M.; Alonso, U.; Muurinen, A.; Carlsson, T.; Chain, P.; Alba, M.D.; Becerro, A.I.; Castro, M.A.; Escudero, A.; Gonzalez-Carrascosa, T.; Hurtado, S.; Pavon, E.; Villa, M.; Bourg, I.C.; Sposito, G.; Bourg, A.C.M.; Marques Fernandes, M.; Rabung, Th.; Dahn, R.; Baeyens, B.; Bradbury, M.H.; Breynaert, E.; Maes, A.; Bruggeman, C.; Maes, I.A.; Vancluysen, J.; Credoz, A.; Bildstein, O.; Jullien, M.; Raynal, J.; Petronin, J.C.; Trotignon, L.; Pokrovsky, O.; Jacquier, P.; Beaucaire, C.; Vuillaume, A.L.; Wittebroodt, Ch.; Ly, J.; Page, J.; Savoye, S.; Pitsch, H.; Jacques, D.; Wang, L.; Galunin, E.; Chain, P.; Alba, M.D.; Vidal, M.; Grandia, F.; Domenech, C.; Arcos, D.; Duro, L.; Bruno, J.; Andre, L.; Pauwels, H.; Azaroual, M.; Albrecht, A.; Romero, M.A.; Aerts, S.; Boven, P.; Van Geet, M.; Boever, P. de; Alonso, U.; Albarran, N.; Missana, T.; Garcia-Gutierrez, M.; Truche, L.; Berger, G.; Guillaume, D.; Jacquot, E.; Tournassat, Ch.; Lerouge, C.; Brendle, J.; Greneche, J.M.; Touzelet, St.; Blanc, Ph.; Gaucher, E.C.; Thoenen, T.; Klinkenberg, M.; Kaufhold, S.; Dohrmann, R.; Siegesmund, S.; Liu, D.J.; Bruggeman, C.; Maes, N.; Weber, T.; Trotignon, L.; Pozo, C.; Bildstein, O.; Combarieu, G. de; Frugier, P.; Menut, D

    2007-07-01

    This session gathers 52 articles (posters) dealing with: the influence of natural sorbents immobilization of spent ion exchange resins in cement; the chemical stability of rare-earth silicate; the mineralogical heterogeneity of Rokle bentonite and radionuclide adsorption: A case study for cesium; the rheological and sorption properties of clay-polymer composites; the clay mineral interactions with leachate solutions in landfills; the lithium isotope fractionation during adsorption onto mineral surfaces; the sorption of Sr{sup 2+} onto mixed smectite / illite clays; Eh and pH in the pore water of compacted bentonite; the chemical interaction of {sup 152}Eu with the clay barrier; the modeling of the acid-base surface chemistry of Montmorillonite; a time resolved laser fluorescence and X-ray absorption spectroscopy study of lanthanide/actinide sorption on clay minerals: influence of carbonate complexation; the structure elucidation and occurrence of Tc(IV) pyrogallol complexes; the geochemistry of Se(0) under boom clay conditions; an experimental and modelling study of pure secondary silicate minerals reactivity in geological CO{sub 2} sequestration conditions; an experimental evaluation of a retention model for major groundwater elements on the Tournemire argillite; modelling the long term interaction of cementitious pore water with Boom clay; the sorption-desorption of radionuclides and analogues in clays suitable for barriers; the modelling of the Redox evolution in the tunnel backfill of a high level nuclear waste repository; the reactivity of nitrates in the different storage compartments of type-b wastes; an investigation into the biodiversity of sulphate reducing bacteria in Boom clay; the colloid generation mechanisms from compacted bentonite under different geochemical conditions; the experimental reduction of aqueous sulphate by hydrogen in the context of the Callovo-Oxfordian argillite; cation exchanged Fe(II) and Sr as compared to other divalent cations

  2. H, HM, and THM-C processes in natural barriers

    Energy Technology Data Exchange (ETDEWEB)

    Javeri, V.; Le, T.T.; Cui, Y.J.; Delage, P.; Li, X.J.; Wieczorek, K.; Jockwer, N.; Romero, E.; Lima, A.; Gens, A.; Li, X.L.; Francois, B.; Nuth, M.; Laloui, L.; Chen, W.; Jia, S.; Yu, H.; Wu, G.; Li, X.; Bernier, F.; Tan, X.; Wu, G.; Jia, S.; Giot, R.; Hoxha, D.; Giraud, A.; Homand, F.; Su, K.; Chavant, C.; Duveau, G.; Jia, Y.; Shao, J.F.; Peron, H.; Laloui, L.; Hueckel, T.; Hu, L.B.; Auvray, C.; Lequiller, B.; Cuisinier, O.; Ferber, V.; Cui, Y.J.; Deneele, D.; Uhlig, L.; Jobmann, M.; Polster, M.; Vaunat, J.; Garrite, B.; Wileveau, Y.; Sato, H.; Jacinto, A.; Sanchez, M.; Ledesma, A.; Morel, J.; Balland, C.; Armand, G.; Nguyen Minh, D.; Vales, F.; Pham, Q.T.; Gharbi, H.; Mokni, N.; Olivella, S.; Li, X.; Smets, St.; Valcke, E.; Karnland, O.; Nilsson, U.; Olsson, S.; Sellin, P.; Fernandez, A.M.; Melon, A.M.; Villar, M.V.; Turrero, M.J.; Garitte, B.; Guimaraes, L.D.N.; Gens, A.; Mayor, J.C.; Koliji, A.; Laloui, L.; Vulliet, L.; Hamdi, N.; Marzouki, A.; Srasra, E.; Cuss, R.J.; Harrington, J.F.; Noy, D.J.; Birchall, D.J.; Marschall, P.; Mallet, A.; Ababou, R.; Matray, J.M.; Renaud, V.; Maison, T.; Enachescu, C.; Frieg, B.; Rohs, St.; Paris, B.; Robinet, J.C.; Bui, T.D.; Barnichon, J.D.; Plas, F.; Klubertanz, G.; Folly, M.; Hufschmied, P.; Frank, E

    2007-07-01

    This session gathers 30 articles (posters) dealing with: the three Dimensional analyses of combined gas, heat and nuclide transport in a repository considering coupled thermo-hydro geomechanical processes; the experimental study on the thermo-hydro-mechanical behaviour of boom clay; hydraulic in-situ measurements in the Opalinus clay in the frame of a heater test performed at the Mont Terri URL; the hydro-mechanical behaviour of natural boom clay in controlled-suction tests; a constitutive approach to address the thermal and hydric impacts in the concept of deep radioactive waste repositories; the numerical analysis on stability of boom clay tunnel by shield construction; a thermo-hydro-mechanical model for clay in unsaturated conditions; the 3D modelling of TER experiment accounting for fully anisotropic thermo-poro-elastic behaviour; the hydro-mechanical modeling of shaft excavation in Meuse/Haute-Marne laboratory; the modelling of drying damage in engineered and natural clay barriers for nuclear waste disposal; the elasto-viscoplastic behaviour of Meuse/Haute-Marne argillite: laboratory tests and modelling; the long-term behaviour of a lime treated soil under percolation conditions; the stress redistribution and hydro-mechanical effects due to excavation and drilling operations in TER experiment; a thermodynamic model on swelling of bentonite buffer and backfill materials; the 3D analysis of a heating test in the Opalinus clay; the THM analysis of a 'mock-up' laboratory experiment using a double-structure expansive model; the measurement of the effect of re-confinement on rock properties around a slot; a laboratory Study of desaturation - re-saturation effects on a clay-stone; the deformation induced by dissolution of salts in porous media; the bentonite swelling pressure in pure water and saline solutions; the mineralogy and sealing properties of various bentonites and smectite-rich clay materials; the evaluation of the geochemical processes occurring

  3. Titanium alloys as alternative material for the supercontainer shell in the KBS-3H concept. A preliminary Ti-clay interaction study

    Energy Technology Data Exchange (ETDEWEB)

    Wersin, Paul (Gruner Ltd (Switzerland)); Grolimund, Daniel (Paul Scherrer Institute (Switzerland)); Kumpulainen, Sirpa; Kiviranta, Leena (BandTech Oy (Finland)); Brendle, Jocelyne (University of Mulhouse (France)); Snellman, Margit (Saanio and Riekkola Oy (Finland))

    2010-12-15

    to shed more light on Ti-clay interaction processes and on the Ti species resulting from these interactions. Purified MX-80 bentonite was mixed with metallic Ti nano powder and foil at different pH and temperature conditions. After several months, solid and solute samples from the first set of tests were analyzed by wet chemistry and quantitative X-ray fluorescence analysis. The chemical speciation of Ti was analyzed with XAS. In addition to reacted samples, a number of reference and starting materials (e.g. MX-80, Rokle bentonite, Opalinus Clay, Illite du Puy) were characterized by XRF and XAS. Preliminary results can be summarized as: - Natural clay materials contain significant but variable amounts of Ti. The standard purification procedure for bentonites to remove accessories does not or only barely remove Ti. - The Ti in the natural clay materials Rokle bentonite, Opalinus Clay and Illite du Puy occurs as microcrystalline TiO{sub 2} (presumably as anatase). On the other hand, the Ti spectra in MX-80 suggest the presence of structural Ti in the smectite, but the evidence is not conclusive so far. - The exposure of purified MX-80 to titanium powder at room temperature within a period of five months did not lead to measurable additional Ti in the clay. A second series of experiments with synthetic 'Ti-free' montmorillonite at higher temperatures (80 deg C) was conducted for a period of 4.5 months in order to increase Ti transfer rates from the metal surfaces to the clay. As revealed from spectroscopic analysis (micro-XRF and XANES) on the reacted materials, the use of synthetic montmorillonite combined with the increase of temperature allowed to partly overcome the experimental problems noted in the first series. Thus, Ti background concentrations were effectively very low and Ti transfer to the clay could be identified with spectroscopic analysis. On the other hand, the spectroscopic data highlighted further weaknesses in the setup. Thus the use of Ti

  4. Titanium alloys as alternative material for the supercontainer shell in the KBS-3H concept. A preliminary Ti-clay interaction study

    Energy Technology Data Exchange (ETDEWEB)

    Wersin, Paul [Gruner Ltd (Switzerland); Grolimund, Daniel [Paul Scherrer Institute (Switzerland); Kumpulainen, Sirpa; Kiviranta, Leena [BandTech Oy (Finland); Brendle, Jocelyne [University of Mulhouse (France); Snellman, Margit [Saanio and Riekkola Oy (Finland)

    2010-12-15

    more light on Ti-clay interaction processes and on the Ti species resulting from these interactions. Purified MX-80 bentonite was mixed with metallic Ti nano powder and foil at different pH and temperature conditions. After several months, solid and solute samples from the first set of tests were analyzed by wet chemistry and quantitative X-ray fluorescence analysis. The chemical speciation of Ti was analyzed with XAS. In addition to reacted samples, a number of reference and starting materials (e.g. MX-80, Rokle bentonite, Opalinus Clay, Illite du Puy) were characterized by XRF and XAS. Preliminary results can be summarized as: - Natural clay materials contain significant but variable amounts of Ti. The standard purification procedure for bentonites to remove accessories does not or only barely remove Ti. - The Ti in the natural clay materials Rokle bentonite, Opalinus Clay and Illite du Puy occurs as microcrystalline TiO{sub 2} (presumably as anatase). On the other hand, the Ti spectra in MX-80 suggest the presence of structural Ti in the smectite, but the evidence is not conclusive so far. - The exposure of purified MX-80 to titanium powder at room temperature within a period of five months did not lead to measurable additional Ti in the clay. A second series of experiments with synthetic 'Ti-free' montmorillonite at higher temperatures (80 deg C) was conducted for a period of 4.5 months in order to increase Ti transfer rates from the metal surfaces to the clay. As revealed from spectroscopic analysis (micro-XRF and XANES) on the reacted materials, the use of synthetic montmorillonite combined with the increase of temperature allowed to partly overcome the experimental problems noted in the first series. Thus, Ti background concentrations were effectively very low and Ti transfer to the clay could be identified with spectroscopic analysis. On the other hand, the spectroscopic data highlighted further weaknesses in the setup. Thus the use of Ti nano powder is not

  5. Airborne remote sensing of estuarine intertidal radionuclide concentrations

    International Nuclear Information System (INIS)

    Rainey, M.P.

    1999-08-01

    The ability to map industrial discharges through remote sensing provides a powerful tool in environmental monitoring. Radionuclide effluents have been discharged, under authorization, into the Irish Sea from BNFL (British Nuclear Fuels Pic.) sites at Sellafield and Springfields since 1952. The quantitative mapping of this anthropogenic radioactivity in estuarine intertidal zones is crucial for absolute interpretations of radionuclide transport. The spatial resolutions of traditional approaches e.g. point sampling and airborne gamma surveys are insufficient to support geomorphic interpretations of the fate of radionuclides in estuaries. The research presented in this thesis develops the use of airborne remote sensing to derive high-resolution synoptic data on the distribution of anthropogenic radionuclides in the intertidal areas of the Ribble Estuary, Lancashire, UK. From multidate surface sediment samples a significant relationship was identified between the Sellafield-derived 137 Cs and 241 Am and clay content (r 2 = 0.93 and 0.84 respectively). Detailed in situ, and laboratory, reflectance (0.4-2.5μm) experiments demonstrated that significant relationships exist between Airborne Thematic Mapper (ATM) simulated reflectance and intertidal sediment grain-size. The spectral influence of moisture on the reflectance characteristics of the intertidal area is also evident. This had substantial implications for the timing of airborne image acquisition. Low-tide Daedalus ATM imagery (Natural Environmental Research Council) was collected of the Ribble Estuary on May 30th 1997. Preprocessing and linear unmixing of the imagery allowed accurate sub-pixel determinations of sediment clay content distributions (r 2 = 0.81). Subsequently, the established relationships between 137 Cs and 241 Am and sediment grain-size enabled the radionuclide activity distributions across the entire intertidal area (92 km 2 ) to be mapped at a geomorphic scale (1.75 m). The accuracy of these maps

  6. In situ and laboratory migration experiments through boom clay at Mol

    International Nuclear Information System (INIS)

    Preter, P. de; Put, M.; Canniere, P. de

    1993-01-01

    Physico-chemical characterization and migration studies in the Boom clay, envisaged as a potential host sediment for high level waste disposal in Belgium, were started some 15 years ago. A synthesis study of this experimental work has recently been conducted to compile all available data. From a comparison of the available migration data and the data requirements as derived from the performance assessment studies PAGIS (1988) and PACOMA (1991) the new migration programme (1991-1995) was defined. The critical radionuclides, both with relation to dose rates to man and to missing or unreliable migration data, turned out to be 14 C, 99 Tc. 135 Cs and 237 Np. A second group of radionuclides was found to be possibly critical: 79 Se, 93 Zr, 107 Pd, U - , Am - , Cm - , and Pu-isotopes. This report concentrates on the experimental results as obtained from the migration experiments started in the previous migration programme. Some of the reported radionuclides e.g. 90 Sr) have lost their critical character and will not be further studied within the new programme. New experimental data from laboratory tests have become available for Np, Cs, Sr and C (as HC0 3 - ) and the first results on the migration of organic molecules dissolved in the interstitial Boom clay water are reported. The hydraulic parameters (the hydraulic conductivity K and the storage coefficient S o ) were calculated from both laboratory percolation experiments and in situ piezometric measurements. Conclusions concerning Boom clay anisotropy are drawn. Finally, a short description of the ongoing in situ HTO injection experiment is given and the experimental data are analyzed and discussed. 10 refs., 4 figs., 1 tab

  7. Clay-based materials for engineered barriers: a review

    International Nuclear Information System (INIS)

    Lajudie, A.; Raynal, J.; Petit, J.C.; Toulhoat, P.

    1994-01-01

    The potential importance of backfilling and plugging in underground radioactive waste repositories has led different research institutions to carry out extensive studies of swelling clay materials for the development of engineered barriers in underground conditions. These materials should combine a variety of hydro-thermo-mechanical and geochemical properties: impermeability, swelling ability in order to fill all void space, heat transfer and retention capacity for the most noxious radionuclides. Smectite clays best exhibit these properties and most of the research effort has been devoted to this type of materials. In this paper, mineralogical composition, sodium or calcium content, thermo-hydro-mechanical properties, swelling pressure, hydraulic and thermal conductivity, and chemical properties of five smectite clays selected by five major nuclear countries are reviewed: Avonseal montmorillonite (Canada), MX 80 montmorillonite (Sweden), Montigel montmorillonite (Switzerland), S-2 montmorillonite (Spain), and Fo-Ca inter stratified kaolinite/beidellite (France). (J.S.). 29 refs., 5 figs., 3 tabs

  8. Engineered barrier emplacement experiment in Opalinus clay for the disposal of radioactive waste in underground repositories

    International Nuclear Information System (INIS)

    Mayor, J. C.; Garcia-Sineriz, J. L.; Alonso, E.; Alheid, H. J.; Blumbling, P.

    2005-01-01

    The EB project aims at demonstrating the technical feasibility and studying the behaviour of near field components of a high level radioactive waste repository in clay rock. The project consists of an in situ test, a series of complementary laboratory tests as well as modelling work. The project is coordinated by ENRESA (Spain) and the work is being executed by the following organizations: AITEMIN and UPC-DIT (Spain) NAGRA (Switzerland) BGR (Germany) The project is co-funded by the European Commission (contract FIKW-CT-2000-00017) and by the Swiss Federal Office for Education and Science. This report includes a synthesized description of the project from its conception until approximately one and a half years after completion of the installation of the large-scale test (October 2000 to November 30, 2003). The project is described in detail in a series of specific reports. Chapter 9, References, includes the titles of these reports. Although each participating group wrote the sections on their particular work, this report is the result of the technical review, and editing carried out by M. Velasco and J. Farias (Technical Secretariat, ST) under the direction of J.C. Mayor (Project Director, ENRESA). In addition to this preface, and the following executive summary, the report is structured on the basis of nine chapters, the general contents of which are indicated below. Chapter 1 describes, in general terms, the different parts of the project, as well as the justification, objectives, expected results, and anticipated uncertainties. This chapter has been written by the ST, but the ideas are those of all the participating groups. Chapter 2 refers to the in situ test, describing the different test components and systems. Exception is made of the Granular Bentonite Material (GBM), which is described in Chapter 3, and of the geophysical systems for the seismic and electric characterization of near field of the clay rock, which are described in Chapter 4. Chapter 3 is

  9. Engineered barrier emplacement experiment in opalinus clay for the disposal of radioactive waste in underground repositories

    International Nuclear Information System (INIS)

    Mayor, J. C.; Garcia-Sineriz, J. L.; Alonso, E.; Alheid, H. J.; Blumbling, P.

    2005-01-01

    The EB project aims at demonstrating the technical feasibility and studying the behaviour of near field components of a high level radioactive waste repository in clay rock. The project consists of an in situ test, a series of complementary laboratory tests as well as modelling work. The project is coordinated by ENRESA (Spain) and the work is being executed by the following organizations:AITEMIN and UPC-DIT (Spain) NAGRA (Switzerland) BGR (Germany) The project is co-funded by the European Commission (contract FIKW-CT-2000-00017) and by the Swiss Federal Office for Education and Science. This report includes a synthesized description of the project from its conception until approximately one and a half years after completion of the installation of the large-scale test (October 2000 to November 30, 2003). The project is described in detail in a series of specific reports. Chapter 9, References, includes the titles of these reports. Although each participating group wrote the sections on their particular work, this report is the result of the technical review, and editing carried out by M. Velasco and J. Farias (Technical Secretariat, ST) under the direction of J.C. Mayor (Project Director, ENRESA). In addition to this preface, and the following executive summary, the report is structured on the basis of nine chapters, the general contents of which are indicated below. Chapter 1 describes, in general terms, the different parts of the project, as well as the justification, objectives, expected results, and anticipated uncertainties. This chapter has been written by the ST, but the ideas are those of all the participating groups. Chapter 2 refers to the in situ test, describing the different test components and systems. Exception is made of the Granular Bentonite Material (GBM), which is described in Chapter 3, and of the geophysical systems for the seismic and electric characterization of near field of the clay rock, which are described in Chapter 4. Chapter 3 is

  10. Titanium alloys as alternative material for the supercontainer shell in the KBS-3H concept: A preliminary Ti-clay interaction study

    Energy Technology Data Exchange (ETDEWEB)

    Wersin, P. [Gruner Ltd, Basel (Switzerland); Grolimund, D. [Paul Scherrer Inst., Villigen (Switzerland); Kumpulainen, S.; Kiviranta, L. [B and Tech Oy, Helsinki (Finland); Brendle, J. [Mulhouse Univ. (France); Snellman, M. [Saanio and Riekkola Oy, Helsinki (Finland)

    2011-12-15

    to shed more light on Ticlay interaction processes and on the Ti species resulting from these interactions. Purified MX-80 bentonite was mixed with metallic Ti nanopowder and foil at different pH and temperature conditions. After several months, solid and solute samples from the first set of tests were analyzed by wet chemistry and quantitative X-ray fluorescence analysis. The chemical speciation of Ti was analyzed with XAS. In addition to reacted samples, a number of reference and starting materials (e.g. MX-80, Rokle bentonite, Opalinus Clay, Illite du Puy) were characterized by XRF and XAS. Preliminary results can be summarized as: Natural clay materials contain significant but variable amounts of Ti. The standard purification procedure for bentonites to remove accessories does not or only barely remove Ti. The Ti in the natural clay materials Rokle bentonite, Opalinus Clay and Illite du Puy occurs as microcrystalline TiO{sub 2} (presumably as anatase). On the other hand, the Ti spectra in MX-80 suggest the presence of structural Ti in the smectite, but the evidence is not conclusive so far. The exposure of purified MX-80 to titanium powder at room temperature within a period of five months did not lead to measurable additional Ti in the clay. A second series of experiments with synthetic 'Ti-free' montmorillonite at higher temperatures (80 deg C) was conducted for a period of 4.5 months in order to increase Ti transfer rates from the metal surfaces to the clay. As revealed from spectroscopic analysis (micro-XRF and XANES) on the reacted materials, the use of synthetic montmorillonite combined with the increase of temperature allowed to partly overcome the experimental problems noted in the first series. Thus, Ti background concentrations were effectively very low and Ti transfer to the clay could be identified with spectroscopic analysis. On the other hand, the spectroscopic data highlighted further weaknesses in the setup. Thus the use of Ti nanopowder

  11. Influence of radiation-dose pattern from inhaled beta--gamma-emitting radionuclides on canine peripheral lymphocytes

    International Nuclear Information System (INIS)

    Jones, R.K.; Boecker, B.B.; Pickrell, J.A.; Hobbs, C.H.; McClellan, R.O.

    1976-01-01

    As part of studies assess the biological hazards associated with inhaled radionuclides, periodic hematologic evaluations were performed on beagle dogs given a single nose-only exposure to aerosols of beta--gamma-emitting isotopes. The physical form and specific radionuclides selected produced radiation-dose patterns representative of those which might be encountered in the event of human accidental exposures. Dogs received graded lung burdens of either 90 Y, 91 Y, 144 Ce, or 90 Sr, each in fused clay. Differences in the effective half-lives of these radionuclides resulted in a spectrum of cumulative radiation doses to lung delivered at a variety of dose rates. Since the form in which the radionuclides were inhaled was relatively insoluble, the lung and intrathoracic tissues represented the primary recipient of the dose. Regardless of the effective half-life of radionuclide retention, a dose-related depression of peripheral lymphocytes was observed at various times after inhalation exposure. The time at which maximum depression and subsequent recovery occurred, however, was most directly related to the effective half-life of the radionuclide. Of special interest was the persistence of lymphopenia through 2 1 / 2 years after exposure to 144 Ce and 90 Sr in fused clay where, other than tracheobronchial lymph nodes, the lymphoid tissue received very little radiation dose. The possible mechanisms responsible for lymphocyte depression from these various radiation-dose patterns are discussed

  12. Sediment and radionuclide transport in rivers: radionuclide transport modeling for Cattaraugus and Buttermilk Creeks, New York

    International Nuclear Information System (INIS)

    Onishi, Y.; Yabusaki, S.B.; Kincaid, C.T.; Skaggs, R.L.; Walters, W.H.

    1982-12-01

    SERATRA, a transient, two-dimensional (laterally-averaged) computer model of sediment-contaminant transport in rivers, satisfactorily resolved the distribution of sediment and radionuclide concentrations in the Cattaraugus Creek stream system in New York. By modeling the physical processes of advection, diffusion, erosion, deposition, and bed armoring, SERATRA routed three sediment size fractions, including cohesive soils, to simulate three dynamic flow events. In conjunction with the sediment transport, SERATRA computed radionuclide levels in dissolved, suspended sediment, and bed sediment forms for four radionuclides ( 137 Cs, 90 Sr, 239 240 Pu, and 3 H). By accounting for time-dependent sediment-radionuclide interaction in the water column and bed, SERATA is a physically explicit model of radionuclide fate and migration. Sediment and radionuclide concentrations calculated by SERATA in the Cattaraugus Creek stream system are in reasonable agreement with measured values. SERATRA is in the field performance phase of an extensive testing program designed to establish the utility of the model as a site assessment tool. The model handles not only radionuclides but other contaminants such as pesticides, heavy metals and other toxic chemicals. Now that the model has been applied to four field sites, including the latest study of the Cattaraugus Creek stream system, it is recommended that a final model be validated through comparison of predicted results with field data from a carefully controlled tracer test at a field site. It is also recommended that a detailed laboratory flume be tested to study cohesive sediment transport, deposition, and erosion characteristics. The lack of current understanding of these characteristics is one of the weakest areas hindering the accurate assessment of the migration of radionuclides sorbed by fine sediments of silt and clay

  13. Determining redox properties of clay-rich sedimentary deposits in the context of performance assessment of radioactive waste repositories : Conceptual and practical aspects

    NARCIS (Netherlands)

    Behrends, T.; Bruggeman, Christophe

    Redox reactions play a key factor controlling the mobility of redox sensitive radionuclides in clay-rich sediments which might serve as host formations for radioactive waste repositories. Assessing the redox speciation of radionuclides requires information about the redox conditions in the formation

  14. Sediment characteristics of the 2800 meter Atlantic nuclear waste disposal site: Radionuclide retention potential

    Energy Technology Data Exchange (ETDEWEB)

    Neiheisel, James

    1979-09-01

    The sediments of the abandoned 2800 meter Atlantic nuclear waste dumpsite have been analyzed for texture mineral composition, physical properties, cation exchange capacity and factors effecting sediment deposition, as part of an extensive program by the Environmental Protection Agency to evaluate ocean disposal as an alternative nuclear waste disposal method. The sediments physical and chemical properties are evaluated in the light of the geologic setting for their potential role in retarding radionuclide leachate migration from the waste drums to the water column. The sediments are relatively uniform silty clays and clayey silts comprised of approximately one-third biogenous carbonate materials, one-third terrigenous materials and one-third clay minerals. The biogenous materials in the sand and upper silt-size fraction are predominantly foraminifera with minor amounts of diatoms while coccoliths dominate the finer silt and clay size fractions. The terrigenous materials in the course sediment fractions are predominantly quartz and feldspar with minor amounts of mica, glauconite, and heavy minerals. Clay minerals, of the clay-size fraction, in order of abundance, include illite, kaolinite, chlorite and montmorillonite. Relatively high cation exchange capacity in the sediment (15.2-25.4 meq/100g) is attributed to the clay minerals comprising approximately one-third of the sediment. Correspondingly high Kd values might also be expected as a result of sorption of radionuclides onto clay minerals with most favorable conditions related to pH, Eh, and other environmental factors. The biogenous fraction might also be expected to retain some strontium-90 by isomorphous substitution of this radionuclide for calcium. Diagnostic heavy minerals in the sand-size fraction reflect the source areas as predominantly the adjacent continental shelf, and provide important clues concerning the mechanisms effecting transport and deposition of the sediment. Longshore currents along the

  15. Radionuclide transport behavior in a generic geological radioactive waste repository.

    Science.gov (United States)

    Bianchi, Marco; Liu, Hui-Hai; Birkholzer, Jens T

    2015-01-01

    We performed numerical simulations of groundwater flow and radionuclide transport to study the influence of several factors, including the ambient hydraulic gradient, groundwater pressure anomalies, and the properties of the excavation damaged zone (EDZ), on the prevailing transport mechanism (i.e., advection or molecular diffusion) in a generic nuclear waste repository within a clay-rich geological formation. By comparing simulation results, we show that the EDZ plays a major role as a preferential flowpath for radionuclide transport. When the EDZ is not taken into account, transport is dominated by molecular diffusion in almost the totality of the simulated domain, and transport velocity is about 40% slower. Modeling results also show that a reduction in hydraulic gradient leads to a greater predominance of diffusive transport, slowing down radionuclide transport by about 30% with respect to a scenario assuming a unit gradient. In addition, inward flow caused by negative pressure anomalies in the clay-rich formation further reduces transport velocity, enhancing the ability of the geological barrier to contain the radioactive waste. On the other hand, local high gradients associated with positive pressure anomalies can speed up radionuclide transport with respect to steady-state flow systems having the same regional hydraulic gradients. Transport behavior was also found to be sensitive to both geometrical and hydrogeological parameters of the EDZ. Results from this work can provide useful knowledge toward correctly assessing the post-closure safety of a geological disposal system. © 2014, National Ground Water Association.

  16. On the role of clay and its mineralogic components in low- and intermediary-level radioactive waste disposal

    International Nuclear Information System (INIS)

    Craciun, C.; Balan, V.

    2001-01-01

    In site selection for radioactive waste disposal a special attention is paid to clay and its mineralogic components as it has an important potential of retarding for both the radionuclides in radioactive wastes and fluid dynamics in the disposal site. The most frequent reaction implied in the radioisotope migration from liquid to solid phase is the cationic exchange. This work aimed at finding the relationship of clay and its mineralogic components, on one hand, and the exchange properties of the deposits, on the other hand. These relationships are based on the data obtained from about 50 cores sampled in 5 drillings performed in Saligny site, selected for radioactive waste disposal. Four levels different from physical, chemical and mineralogical properties were evidenced. The ionic exchange rate, with values within 5 to 30 me/100 g, has a trend of reflecting the clay contents. The relations between the cationic exchange rate and the clay contents appears to be linear with correlation coefficients varying within 0.81 - 0.97. The mineralogical composition of clay includes smectite (predominantly), illite and kaolin. Close, linear relations between the cationic exchange rate and the smectite fraction in clay and deposits were established with correlation coefficients within 0.74-0.76 and 0.85-0.95, respectively. These results show that the potential of the investigated deposits of acting as natural barriers with retarding effects on both radionuclides and the fluids in the disposal zone is strongly correlated to the amount and the content of the clay in these deposits

  17. Clays in natural and engineered barriers for radioactive waste confinement

    International Nuclear Information System (INIS)

    2007-01-01

    The meeting covers all topics concerning natural argillaceous geological barriers and the clay material based engineered barrier systems, investigated by means of: laboratory experiments on clay samples (new analytical developments), in situ experiments in underground research laboratories, mock-up demonstrations, natural analogues, as well as numerical modelling and global integration approaches (including up-scaling processes and treatment of uncertainties). The works presented deal with: examples of broad research programs (national or international) on the role of natural and artificial clay barriers for radionuclide confinement; clay-based repository concepts: repository designs, including technological and safety issues related to the use of clay for nuclear waste confinement; geology and clay characterisation: mineralogy, sedimentology, paleo-environment, diagenesis, dating techniques, discontinuities in rock clay, fracturing, self sealing processes, role of organic matter and microbiological processes; geochemistry: pore water geochemistry, clay thermodynamics, chemical retention, geochemical modelling, advanced isotopic geochemistry; mass transfer: water status and hydraulic properties in low permeability media, pore space geometry, water, solute and gas transfer processes, colloid mediated transport, large scale movements, long-term diffusion; alteration processes: oxidation effects, hydration-dehydration processes, response to thermal stress, iron-clay interactions, alkaline perturbation; geomechanics: thermo-hydro-mechanical behaviour of clay, rheological models, EDZ characterisation and evolution, coupled behaviour and models (HM, THM, THMC). A particular interest is given to potential contributions coming from fields of activities other than radioactive waste management, which take advantage of the confinement properties of the clay barrier (oil and gas industries, gas geological storage, CO 2 geological sequestration, chemical waste isolation

  18. Clays in natural and engineered barriers for radioactive waste confinement

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2007-07-01

    The meeting covers all topics concerning natural argillaceous geological barriers and the clay material based engineered barrier systems, investigated by means of: laboratory experiments on clay samples (new analytical developments), in situ experiments in underground research laboratories, mock-up demonstrations, natural analogues, as well as numerical modelling and global integration approaches (including up-scaling processes and treatment of uncertainties). The works presented deal with: examples of broad research programs (national or international) on the role of natural and artificial clay barriers for radionuclide confinement; clay-based repository concepts: repository designs, including technological and safety issues related to the use of clay for nuclear waste confinement; geology and clay characterisation: mineralogy, sedimentology, paleo-environment, diagenesis, dating techniques, discontinuities in rock clay, fracturing, self sealing processes, role of organic matter and microbiological processes; geochemistry: pore water geochemistry, clay thermodynamics, chemical retention, geochemical modelling, advanced isotopic geochemistry; mass transfer: water status and hydraulic properties in low permeability media, pore space geometry, water, solute and gas transfer processes, colloid mediated transport, large scale movements, long-term diffusion; alteration processes: oxidation effects, hydration-dehydration processes, response to thermal stress, iron-clay interactions, alkaline perturbation; geomechanics: thermo-hydro-mechanical behaviour of clay, rheological models, EDZ characterisation and evolution, coupled behaviour and models (HM, THM, THMC). A particular interest is given to potential contributions coming from fields of activities other than radioactive waste management, which take advantage of the confinement properties of the clay barrier (oil and gas industries, gas geological storage, CO{sub 2} geological sequestration, chemical waste isolation

  19. Sorption of radioscesium from liquid radioactive waste on clay and immobilization by baking the clay at elevated temperature

    Energy Technology Data Exchange (ETDEWEB)

    Rashid, F.; Ghaffar, A. [Pakistan Inst. of Nuclear Science and Technology, Islamabad (Pakistan)

    2011-07-01

    The cesium-137 is the most problematic radionuclide in the radioactive wastes. It belongs to the IA group of the periodic table, highly reactive towards water and has very high mobility. Due to beta and gamma radiation hazards of radiocesium its decontamination and disposal requires some special tools and techniques. In this study globules of clay material was used for the removal of cesium from low level liquid radioactive wastes and further processed for immobilization. The aim of this study was to assess the solidification and immobilization of secondary waste. The secondary waste, after sorption of cesium from the liquid radioactive waste generated at this institute, was found compatible to the cement matrix used for the cementation process. The procedure for immobilization of low level radioactive waste with cementation using vitreous clay material as an additive was developed. (orig.)

  20. Sorption of radioscesium from liquid radioactive waste on clay and immobilization by baking the clay at elevated temperature

    International Nuclear Information System (INIS)

    Rashid, F.; Ghaffar, A.

    2011-01-01

    The cesium-137 is the most problematic radionuclide in the radioactive wastes. It belongs to the IA group of the periodic table, highly reactive towards water and has very high mobility. Due to beta and gamma radiation hazards of radiocesium its decontamination and disposal requires some special tools and techniques. In this study globules of clay material was used for the removal of cesium from low level liquid radioactive wastes and further processed for immobilization. The aim of this study was to assess the solidification and immobilization of secondary waste. The secondary waste, after sorption of cesium from the liquid radioactive waste generated at this institute, was found compatible to the cement matrix used for the cementation process. The procedure for immobilization of low level radioactive waste with cementation using vitreous clay material as an additive was developed. (orig.)

  1. Quantitative assessment of radionuclide retention in the near-surface system at Forsmark. Development of a reactive transport model using Forsmark 1.2 data

    International Nuclear Information System (INIS)

    Grandia, Fidel; Sena, Clara; Arcos, David; Molinero, Jorge; Duro, Lara; Bruno, Jordi

    2007-12-01

    The main objective of this work is to assess the migration behaviour of selected long-lived radionuclides through the near-surface system of Forsmark, with special focus on the evaluation of the capacity of the Quaternary deposits and sediments for radionuclide retention. The work reported here is based on data and information from Forsmark Site Descriptive Model version 1.2. From the geological point of view, the near-surface systems in the Forsmark area consist of Quaternary deposits and sediments that overlay the granitic bedrock. Glacial till is the more abundant outcropping Quaternary deposit and the remainder is made of clayey deposits. These types of near-surface sediments show distinctive hydraulic and geochemical features. The main reactive mineral in the till deposits, for the time horizons considered in this work, is calcium carbonate together with minor amounts of clay minerals (e.g. illite). The till deposits forms aquifers with relatively high hydraulic conductivities. In contrast, glacial and post-glacial clays are basically composed of illite with low to very low amounts of calcium carbonate, and containing organic matter-rich layers (gyttja), which can promote reducing conditions in the porewaters. All these clays exhibits relatively low hydraulic conductivity values. Five radionuclides have been selected for conceptualization and qualitative evaluation of retention process: U as an actinide, Se as a redox-sensitive radionuclide, Cs as a monovalent cation, Sr as a divalent cation, and I as an anion radionuclide. Overall, radionuclide retention capacity in the surface systems at Forsmark can be provided by sorption on charged surfaces of clays and oxyhydroxides, co-precipitation with sulphates, sulphides, oxyhydroxides and carbonates, and sorption on organic matter. Two-dimensional coupled hydrogeological and reactive solute transport models have been developed to simulate the geochemical behaviour of U, Cs and Sr. These three radionuclides have

  2. Quantitative assessment of radionuclide retention in the near-surface system at Forsmark. Development of a reactive transport model using Forsmark 1.2 data

    Energy Technology Data Exchange (ETDEWEB)

    Grandia, Fidel; Sena, Clara; Arcos, David; Molinero, Jorge; Duro, Lara; Bruno, Jordi (Amphos XXI Consulting S.L., Barcelona (Spain))

    2007-12-15

    The main objective of this work is to assess the migration behaviour of selected long-lived radionuclides through the near-surface system of Forsmark, with special focus on the evaluation of the capacity of the Quaternary deposits and sediments for radionuclide retention. The work reported here is based on data and information from Forsmark Site Descriptive Model version 1.2. From the geological point of view, the near-surface systems in the Forsmark area consist of Quaternary deposits and sediments that overlay the granitic bedrock. Glacial till is the more abundant outcropping Quaternary deposit and the remainder is made of clayey deposits. These types of near-surface sediments show distinctive hydraulic and geochemical features. The main reactive mineral in the till deposits, for the time horizons considered in this work, is calcium carbonate together with minor amounts of clay minerals (e.g. illite). The till deposits forms aquifers with relatively high hydraulic conductivities. In contrast, glacial and post-glacial clays are basically composed of illite with low to very low amounts of calcium carbonate, and containing organic matter-rich layers (gyttja), which can promote reducing conditions in the porewaters. All these clays exhibits relatively low hydraulic conductivity values. Five radionuclides have been selected for conceptualization and qualitative evaluation of retention process: U as an actinide, Se as a redox-sensitive radionuclide, Cs as a monovalent cation, Sr as a divalent cation, and I as an anion radionuclide. Overall, radionuclide retention capacity in the surface systems at Forsmark can be provided by sorption on charged surfaces of clays and oxyhydroxides, co-precipitation with sulphates, sulphides, oxyhydroxides and carbonates, and sorption on organic matter. Two-dimensional coupled hydrogeological and reactive solute transport models have been developed to simulate the geochemical behaviour of U, Cs and Sr. These three radionuclides have

  3. The long-term behaviour of cemented research reactor waste under the geological disposal conditions of the Boom Clay Formation: results from leach experiments

    International Nuclear Information System (INIS)

    Sneyers, A.; Fays, J.; Iseghem, P. van

    2001-01-01

    The Belgian Nuclear Research Centre SCK-CEN has carried out a number of studies to evaluate the long-term behaviour of cemented research reactor waste under the geological disposal conditions of the Boom Clay Formation. Static leach experiments in synthetic clay water were performed on active samples of cemented research reactor waste. The leach experiments were carried out under anaerobic conditions at two testing temperatures (23 and 85 o C). Leach rates of seven radionuclides ( 60 Co, 90 Sr, 134 Cs, 137 Cs, 144 Ce, 154 Eu and 241 Am) were measured. Most investigated radionuclides are well retained within the cement matrix over a 280 days testing period. Results on the source term of radionuclides were complemented with data on the leaching behaviour of cement matrix constituents as Ca, Si, Al, Na, K, Mg and SO 4 as well as with data from performance assessment calculations and in situ tests. Despite limitations inherent to short-term experiments, combined results from these investigations indicate only limited interactions of disposed research reactor waste with the near field of a geological repository in clay. (author)

  4. Damage-induced permeability changes around underground excavations; Endommagement des roches argileuses et permeabilite induite au voisinage d'ouvrages souterrains

    Energy Technology Data Exchange (ETDEWEB)

    Coll, C

    2005-07-15

    The storage of nuclear waste in deep geological formations is now considered more and more as a potential solution. During excavation, a disturbed zone develops in which damaging can be important and which can lead eventually to the failure of the rock. Fluid flow and permeability in the rock mass can be significantly modified producing a possible security risk. Our work consisted in an experimental study of the hydro-mechanical coupling of two argillaceous rocks: Boom clay (Mol, Belgium) and Opalinus clay (Mont-Terri, Switzerland). Triaxial tests were performed in a saturated state to study the permeability evolution of both clays with isotropic and deviatoric stresses. Argillaceous rocks are geo-materials with complex behaviour governed by numerous coupled processes. Strong physico-chemical interactions between the fluid and the solid particles and their very low permeability required the modification of the experimental set up. Moreover, specific procedures were developed to measure permeability and to detect strain localisation in shear bands. We show that for Boom Clay, permeability is not significantly influenced by strain localisation. For Opalinus clay, fracturing can induce an increase of the permeability at low confining pressure. (author)

  5. Damage-induced permeability changes around underground excavations

    International Nuclear Information System (INIS)

    Coll, C.

    2005-07-01

    The storage of nuclear waste in deep geological formations is now considered more and more as a potential solution. During excavation, a disturbed zone develops in which damaging can be important and which can lead eventually to the failure of the rock. Fluid flow and permeability in the rock mass can be significantly modified producing a possible security risk. Our work consisted in an experimental study of the hydro-mechanical coupling of two argillaceous rocks: Boom clay (Mol, Belgium) and Opalinus clay (Mont-Terri, Switzerland). Triaxial tests were performed in a saturated state to study the permeability evolution of both clays with isotropic and deviatoric stresses. Argillaceous rocks are geo-materials with complex behaviour governed by numerous coupled processes. Strong physico-chemical interactions between the fluid and the solid particles and their very low permeability required the modification of the experimental set up. Moreover, specific procedures were developed to measure permeability and to detect strain localisation in shear bands. We show that for Boom Clay, permeability is not significantly influenced by strain localisation. For Opalinus clay, fracturing can induce an increase of the permeability at low confining pressure. (author)

  6. Damage-induced permeability changes around underground excavations; Endommagement des roches argileuses et permeabilite induite au voisinage d'ouvrages souterrains

    Energy Technology Data Exchange (ETDEWEB)

    Coll, C

    2005-07-15

    The storage of nuclear waste in deep geological formations is now considered more and more as a potential solution. During excavation, a disturbed zone develops in which damaging can be important and which can lead eventually to the failure of the rock. Fluid flow and permeability in the rock mass can be significantly modified producing a possible security risk. Our work consisted in an experimental study of the hydro-mechanical coupling of two argillaceous rocks: Boom clay (Mol, Belgium) and Opalinus clay (Mont-Terri, Switzerland). Triaxial tests were performed in a saturated state to study the permeability evolution of both clays with isotropic and deviatoric stresses. Argillaceous rocks are geo-materials with complex behaviour governed by numerous coupled processes. Strong physico-chemical interactions between the fluid and the solid particles and their very low permeability required the modification of the experimental set up. Moreover, specific procedures were developed to measure permeability and to detect strain localisation in shear bands. We show that for Boom Clay, permeability is not significantly influenced by strain localisation. For Opalinus clay, fracturing can induce an increase of the permeability at low confining pressure. (author)

  7. Towards an assessment of colloid transport in undisturbed clay stone

    International Nuclear Information System (INIS)

    Durce, D.; Landesman, C.; Grambow, B.; Giffaut, E.

    2010-01-01

    Document available in abstract form only. Full text of publication follows: Colloids are known as a potentially important transport vector for sparingly soluble radionuclides in natural water environments. For assessing the mass transfer resistance of the Callovo-Oxfordian clay rock formation for colloid transport, a series of percolation experiments have been performed, using high pressure stainless steel advection cells of different diameters containing clay cores machined to about 50 μm of accuracy to the inner diameter of the cells. Synthetic clay pore water was pushed by a high pressure syringe pump across the clay core. In order to assess the cut-off size for colloid transport, molecules of different molecular weight were injected. C 14 labeled polymaleic acid (PMA) of sizes of 2 and 50 kDa were used. The effect of clay permeability, of water flow rate (injection pressure) and of ionic strength was studied. Low ionic strength experiments (I = 0.001) were realized by replacing the pore water by advective displacement with the required composition. Clay rock permeabilities were between 10 -12 and 10 -14 m/s. Hydrodynamic parameters were determined by HTO and 36 Cl injection. The results show already at 2 kDa and a permeability of 10 -12 m/s strong retention by partial filtration. The experimental results were modeled using simple chromatographic theory. (authors)

  8. Sorption of Cesium on smectite-rich clays from the Bohemian Massif (Czech Republic) and their mixtures with sand.

    Science.gov (United States)

    Vejsada, J; Jelínek, E; Randa, Z; Hradil, D; Prikryl, R

    2005-01-01

    Sorption is an important process for the transport of radionuclides through backfill materials in a radioactive waste underground repository. Within this study, sorption of Cs on selected Czech clay materials and their mixtures with sand was investigated by batch tests. The experiments were performed under oxic conditions at 25 degrees C. Synthetic groundwater as a liquid phase and unconditioned clays (as they were provided by their producer) were used to reach the natural conditions as close as possible. Distribution ratios (Rds) of Cs for all selected clays rise with increase of the clay fraction in clay/sand mixtures in agreement with previous works studying sorption behaviour of such mixtures. The rise of Rds is from 10(2) cm3 g(-1) for mixtures with 80% of sand to 10(3) cm3 g(-1) for pure clays. There are significant differences between natural and technologically modified clays.

  9. Effect of Organic Pollutants on Migration of Radionuclides in Soil

    International Nuclear Information System (INIS)

    Nasr, R.G.A.

    2012-01-01

    The aim of this thesis is to study the effect of organic pollutants on the mobility of selected heavy metal (pb 2+ ) and radionuclide ( 60 Co) in an Egyptian agricultural soil and in a clay fraction separated from the soil. The effect of presence of natural organic compounds such as humic acid is also studied

  10. Natural-analog studies for partial validation of conceptual models of radionuclide retardation at the Waste Isolation Pilot Plant (WIPP)

    International Nuclear Information System (INIS)

    Ward, D.B.; Brookins, D.G.

    1990-01-01

    Transport by groundwater within the Culebra Dolomite, an aquifer above the Waste Isolation Pilot Plant (WIPP), is the most probable mechanism for long-term release of radionuclides to the accessible environment. Radionuclides could be retarded by sorption if the groundwater is exposed to sufficient amounts of fracture-lining clays. In this natural-analog study, distributions of U and trace metals have been examined to constrain the strength of clay/solute interactions within the Culebra. Uranium solid/liquid distribution ratios, calculated from U concentrations of groundwaters and consanguineous fracture-filling clays, range from ∼80 to 800 m ell/g and imply retardation factors of 60 to 500 using a fracture-flow model. Retardation factors inferred from uranium-series disequilibria and 14 C ages in Culebra groundwaters alone are much lower (∼10), implying that clays may contain a significant unreactive component of U. Such a possibility is corroborated by Rb/Sr ages; these imply long-term stability of the clays,with resetting occurring more than 250 Ma ago. Factor analysis and mass-balance calculations suggest, however, that Mg-rich clays are dissolving in Pleistocene-age groundwaters and/or are converting to Na-rich smectites, and that B and Li are taken up from the water by the clays. Apparently, the solution chemistry reflects gradual equilibration of clays with groundwater, but thus far the bulk of the clays remain structurally intact. Measurements of the distribution of U in the Culebra will be more meaningful if the inert and exchangeable components of the U content of the clays can be quantified. 26 refs., 3 figs., 2 tabs

  11. Presence and evolution of natural organic matter in the boom clay

    International Nuclear Information System (INIS)

    Van Geet, M.; Deniau, I.; Largeau, C.; Bruggeman, C.; Maes, A.; Dierckx, A.

    2004-01-01

    Because of its very low hydraulic conductivity, reducing conditions, slightly alkaline pH, high specific surface, high cation exchange capacity and high plasticity, the Boom Clay is studied as a reference host formation for the deep disposal of high-level long-lived radioactive waste (NIRAS/ONDRAF, 1989). However, Boom Clay also contains up to 5% wt. of organic matter (OM). As radionuclides can form complexes with this organic matter, a detailed characterisation and knowledge of the evolution of the organic matter is necessary. An overview of the characteristics of the organic matter present in Boom Clay is given by Van Geet et al., (2003). The solid phase OM can be up to 5%. The dissolved OM fraction is around 200 mg C per liter of Boom Clay pore water. Both kinds of OM will be discussed. Concerning the solid phase OM the focus will be on the past evolution and its possible future evolution due to a thermal stress. For the dissolved OM, the focus will be on its origin. (author)

  12. Gonadossomatic relation and reproductive strategy of Brycon opalinus (Cuvier, 1819 in the Serra do Mar State Park - Núcleo Santa Virgínia, Atlantic Forest, Brazil

    Directory of Open Access Journals (Sweden)

    LM Gomiero

    Full Text Available The objective of this study was to analyze the gonadossomatic relation of males and females of Brycon opalinus (the Pirapitinga do Sul in the Serra do Mar State Park-Núcleo Santa Virgínia. The study area included three rivers: Paraibuna, Ipiranga, and Grande. From the gonadossomatic relation, it was possible to determine the reproductive season and strategy of this species. The gonadossomatic relation was high throughout the year for both males and females. Sperm competition and dilution of the ejaculate in the spawning locations favored substantial development of the testicles. The sex ratio of Brycon opalinus was always in favor of females. The existence of sexual dimorphism in this species was confirmed from the larger size of the females.

  13. Conceptual and Numerical Modeling of Radionuclide Transport and Retention in Near-Surface Systems

    International Nuclear Information System (INIS)

    Pique, Angels; Arcos, David; Grandia, Fidel; Molinero, Jorge; Duro, Lara; Berglund, Sten

    2013-01-01

    Scenarios of barrier failure and radionuclide release to the near-surface environment are important to consider within performance and safety assessments of repositories for nuclear waste. A geological repository for spent nuclear fuel is planned at Forsmark, Sweden. Conceptual and numerical reactive transport models were developed in order to assess the retention capacity of the Quaternary till and clay deposits for selected radionuclides, in the event of an activity release from the repository. The elements considered were carbon (C), chlorine (Cl), cesium (Cs), iodine (I), molybdenum (Mo), niobium (Nb), nickel (Ni), radium (Ra), selenium (Se), strontium (Sr), technetium (Tc), thorium (Th), and uranium (U). According to the numerical predictions, the repository-derived nuclides that would be most significantly retained are Th, Ni, and Cs, mainly through sorption onto clays, followed by U, C, Sr, and Ra, trapped by sorption and/or incorporation into mineral phases

  14. Radionuclide partitioning in environmental systems: a critical analysis

    International Nuclear Information System (INIS)

    Cremers, A.; Maes, A.

    1986-01-01

    A survey is given of some of the important processes involved in the solid-liquid distribution behaviour of radionuclides in both well-defined adsorbents and multicomponent natural systems. The thermodynamic significance of distribution coefficients is analyzed and the various parameters affecting partition behaviour are discussed in relation to possible retention mechanisms. Attention is being given to factors such as solid/liquid ratio, pH-Eh, reversibility, liquid phase composition and speciation effects. Various processes are discussed such as ion exchange and complex formation involving clays, oxides, humic acids. It is shown that, only in rare cases, Ksub(D) values can be rationalized in terms of process mechanistics. In addition, it is indicated that, in general, radionuclide distribution coefficients cannot be considered as constants unless the conditions are restricted to very small loading intervals. It is furthermore suggested that, in order to produce meaningful data on radionuclide partitioning behaviour, efforts should be made to operate under conditions which are representative for the 'in situ' situation. (author)

  15. Processes of cation migration in clay-rocks: Final Scientific Report of the CatClay European Project

    International Nuclear Information System (INIS)

    Altmann, S.; Aertsens, M.; Appelo, T.; Bruggeman, C.; Gaboreau, S.; Glaus, M.; Jacquier, P.; Kupcik, T.; Maes, N.; Montoya, V.; Rabung, T.; Robinet, J.-C.; Savoye, S.; Schaefer, T.; Tournassat, C.; Van Laer, L.; Van Loon, L.

    2015-07-01

    illite and clay rocks, even though some assumptions made have to be verified. In parallel, actual 3D geometrical pore size distributions of compacted illite, and in less extent, clay rock samples, were successfully determined by combining TEM and FIB-nt analyses on materials maintained in a water-like saturation state by means of an extensive impregnation step. Based on this spatial distribution of pores, first numerical diffusion experiments were carried at the pore scale through virtual illite, enabling a better understanding of how transfer pathways are organized in the porous media. Finally, the EC CatClay project allowed a better understanding of the migration of strongly sorbing tracers through low permeability 'clay rock' formations, increasing confidence in our capacity to demonstrate that the models used to predict radionuclide migration through these rocks are scientifically sound. (authors)

  16. Changes in the Expandability, Layer charge, and CEC of Smectitic Clay due to a Illitization

    International Nuclear Information System (INIS)

    Lee, Jae Owan; Cho, Won Jin

    2007-01-01

    In a high-level waste(HLW) repository, the major fucntions of the smectitic clay for use as a buffer material are to inhibit the penetration of groundwater and to retard the release of radionuclides from the radioactive wastes to the surrounding environment. However, when the smectite clay is exposed to an elevated temperature due to radioactive decay heat and geochemical conditions for a long time, its physicochemical and mineralogical properties may be degradated and thus lose its barrier functions. It has been known in literature that the degradation of these properties of the smectitic clay occurs by a illitization in which the smectite transforms into illite. Therefore, an understanding of the illitization is essential to evaluate the long-term barrier performance of smectitic clay for the buffer of a HLW repository. This paper will carry out hydrothermal reaction tests with domestic smectitic clay which will be favorably considered for the buffer material of a Korean HLW repository, and investigate changes in the expandibility, layer charge and cation exchange capacity(CEC) of the smectitic clay due to a illitization

  17. Use of the mixture of clay and crushed rock as a backfill material for low and intermediate level radioactive waste repository. Appendix 10: Republic of Korea

    International Nuclear Information System (INIS)

    Cho, W.J.; Lee, J.O.; Hahn, P.S.; Chun, K.S.

    2001-01-01

    At the time of the CRP, a repository for low and intermediate level radioactive wastes arising from nuclear power plant operation and radioisotope application in the Republic of Korea was to be constructed in the bedrock below ground surface. As the intermediate level waste cavern would contain the major part of radionuclide inventory in the cavern, the radionuclide release from the intermediate level waste cavern was therefore important from the viewpoint of disposal facility performance. The then current design concept suggested that the intermediate level waste would be emplaced into the compartment made of reinforced concrete, and the space between the concrete wall and cavern surface would be backfilled with a clay-based material. As compacted clay-based materials have a low hydraulic conductivity and the hydraulic gradient in a disposal cavern was expected to be relatively low, molecular diffusion was considered to be the principal mechanism by which radionuclides would migrate through the backfill. The mixture of calcium bentonite and crushed rock was being suggested as a candidate backfill material. This appendix summarises the KAERI research activities on the evaluation of hydraulic conductivity, radionuclide diffusion coefficient, and mechanical properties of the candidate clay-based backfill material for the intermediate level waste cavern

  18. Self-sealing of fractures in argillaceous formations - Evidence, mechanisms and implications for performance assesment (an NEA Clay Club project)

    International Nuclear Information System (INIS)

    Bock, H.; Dehandschutter, B.; Martin, C.D.; Mazurek, M.; Haller, A. de; Skoczylas, F.; Davy, C.

    2010-01-01

    Document available in extended abstract form only. After some earlier attempts dating back to the year 1999, the Self-Sealing Project of the Clay Club of the NEA/OECD was re-launched in 2007 and recently completed with the publication of NEA monograph No. 6184 (Bock et al., 2010). The project aimed at providing an overview and synthesis of the current understanding of, and conceptual approaches to, the processes that lead to self-sealing of natural and man-induced fractures in argillaceous formations at typical repository depths. The term 'self-sealing' relates to a phenomenon that fractured argillaceous formations tend to become, with the passage of time, less conductive to groundwater and finally hydraulically insignificant. It directly addresses the long-term functionality of the host rock as a migration barrier to radio-nuclides and it is often considered as one of the decisive factors favouring the choice of argillaceous formations as host rocks for deep disposals. In its outcome the project has significantly consolidated the evidence on self-sealing in argillaceous formations. It reconfirmed that self-sealing is a common phenomenon in a wide variety of argillaceous formations which are currently considered in context with deep geological repositories; from plastic clays (Boom Clay in the HADES URF) to moderately indurated clays (Opalinus Clay at Mont Terri and Callovo- Oxfordian argillites at the Meuse-Haute Marne URL). One of the most compelling evidence stems from the fact that self-sealing is observed over a large spread of scales in terms of length and time: At the millimetre to metre scale in laboratory testing, at the repository scale (10 m to 100 m range) in URL field tests and at the kilometre scale in geologic and geotechnical analogues such as traffic tunnels and hydrocarbon reservoirs. Over geological time scales, it is, for example, evidenced in the existence of hydraulically and geochemically inactive geological faults, in the existence

  19. Comparison studies adsorption of thorium and uranium on pure clay minerals and local Malaysian soil sediments

    International Nuclear Information System (INIS)

    Syed, H.S.

    1999-01-01

    Adsorption studies of thorium and uranium radionuclides on 9 different pure clay minerals and 4 local Malaysian soil sediments were conducted. Solution containing dissolved thorium and uranium at pH 4.90 was prepared from concentrate sludges from a long term storage facility at a local mineral processing plant. The sludges are considered as low level radioactive wastes. The results indicated that the 9 clay minerals adsorbed more uranium than thorium at pH ranges from 3.74 to 5.74. Two local Malaysian soils were observed to adsorb relatively high concentration of both radionuclides at pH 3.79 to 3.91. The adsorption value 23.27 to 27.04 ppm for uranium and 33.1 to 50.18 ppm for thorium indicated that both soil sediments can be considered as potential enhanced barrier material for sites disposing conditioned wastes containing uranium and thorium. (author)

  20. Comparison of sorption measurements on argillaceous rocks and bentonite with predictions using the SGT-E2 approach to derive sorption data bases

    Energy Technology Data Exchange (ETDEWEB)

    Bradbury, M. H.; Baeyens, B; Marques Fernandes, M.

    2014-11-15

    In Stage 1 of the Sectoral Plan for Deep Geological Repositories, four rock types have been identified as being suitable host rocks for a radioactive waste repository, namely, Opalinus Clay for a high-level (HLW) and a low- and intermediate-level (L/ILW) repository, and 'Brauner Dogger', Effingen Member and Helvetic Marls for a L/ILW repository. Sorption data bases (SDBs) for all of these host rocks are required for the provisional safety analyses, including all of the bounding porewater and mineralogical composition combinations. In addition, SDBs are needed for the rock formations lying below Opalinus Clay (lower confining units) and for the bentonite backfill in the HLW repository. A detailed procedure was developed for deriving SDBs for argillaceous rocks (and bentonite) based on sorption edge measurements on illite (and montmorillonite), the hypothesis that 2:1 clay minerals are the dominant sorbents and a series of so called conversion factors which take into account the different radionuclide speciations in the different porewaters. Since this methodology for generating SDBs is relatively new, a validation and demonstration of the robustness and reliability of the sorption values derived was required. This report describes an extensive piece of work in which blind predictions of sorption values were compared with measured ones. Sorption isotherms were measured for the following metal ions Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI) in a range of realistic porewater chemistries for a range of host rock mineralogies. In the end 53 isotherm data sets were measured. For each of these isotherms a prediction was made of the sorption at trace concentrations using the SDB derivation methodology. A comparison between measured and predicted values for each case was then made. This validation study shows that the methodology used for the derivation of the sorption data bases for argillaceous rocks and bentonite produces reliable sorption values. (authors)

  1. A Study of Clay-Epoxy Nanocomposites Consisting of Unmodified Clay and Organo Clay

    Directory of Open Access Journals (Sweden)

    Graham Edward

    2006-04-01

    Full Text Available Clay-epoxy nanocomposites were synthesized from DGEBA resin and montmorillonite clay with an in-situ polymerization. One type of untreated clay and two types of organo clay were used to produce the nanocompsoites. The aims of this study were to examine the nanocomposite structure using different tools and to compare the results between the unmodified clay and modified clays as nanofillers. Although diffractogram in reflection mode did not show any apparent peak of both types of materials, the transmitted XRD (X-Ray Difraction graphs, DSC (Differential Scanning Calorimeter analysis and TEM (Transmission Electron Microscope images revealed that the modified clay-epoxy and unmodified clay-epoxy provides different results. Interestingly, the micrographs showed that some of the modified clay layers possessed non-exfoliated layers in the modified clay-epoxy nanocomposites. Clay aggregates and a hackle pattern were found from E-SEM images for both types of nanocomposite materials. It is shown that different tools should be used to determine the nanocomposite structure.

  2. In situ determination of anisotropic permeability of clay

    International Nuclear Information System (INIS)

    Shao, H.; Soennke, J.; Morel, J.; Krug, S.

    2010-01-01

    in clay stone is generally considered to have a depth of approximately 2 metres. Therefore, a 3-m borehole can also be used for both objects. Ail boreholes are drilled by using dry air technique and oriented parallel to the bedding plane, so that the permeability parallel and perpendicular to the bedding plane can be tested only by turning the 'slot'. Hydraulic tests using gas as test medium are carried out immediately after the drilling of the holes. For evaluation of the measured data, the finite element program RockFlow has been used. The packer 'slot' with a width of 1 cm can also be simulated in the numerical model. Most of the measurements show a clear hydraulic anisotropy due to the bedding structure. As summary, following statements can be made: - Hydraulic anisotropy of clay medium can be determined using the developed 'slot packer' system with orientated applications. - The anisotropic ratio of the Opalinus Clay at Mont Terri (permeability parallel to the bedding/permeability perpendicular to the bedding) may be evaluated up to eight times to one order of magnitude. - Fractures in the excavation damaged zone around the underground opening in clay formations can be identified and especially the orientations of the fractures can be determined using the 'slot packer'. - The fracture permeability has a significant importance for the hydraulic characterisation of the near field. A double packer is sufficient to determine the permeability for this purpose. This tool can also be applied in fractured rock (e.g. granite) to determine the fracture orientation. (authors)

  3. Radionuclide transport from near-surface repository for radioactive waste - The unsaturated zone approach

    Energy Technology Data Exchange (ETDEWEB)

    Jakimaviciute-Maseliene, V. [Vilnius University (Lithuania); Mazeika, J. [Nature Research Centre (Lithuania); Motiejunas, S. [Radioactive Waste Management Agency (Lithuania)

    2014-07-01

    About 100 000 m{sup 3} of solid conditioned Low and Intermediate Level Waste (LILW), generated during operation and decommissioning of the Ignalina nuclear power plant (INPP), are to be disposed of in a near-surface repository (NSR) - a 'hill'-type repository with reinforced concrete vaults and with engineered and natural barriers. The northeastern Lithuania and the environment of the INPP in particular were recognized as the areas most suitable for a near-surface repository (Stabatiske Site). The engineered barriers of the repository consist of concrete cells surrounded by clay-based material of low permeability with about the same isolating capacity in all directions. The clay materials must be effectively compactable so that required hydraulic conductivity is reached. The Lithuanian Triassic clay turned out to be sufficiently rich in smectites and was proposed as main candidate for sealing of the repository. When the concrete vaults are filled, the repository cover will be constructed. The surface of the mound will be planted with grass. In this study a computer code FEFLOW 5.0 was applied for simulating the transport of the most mobile radionuclides ({sup 3}H, {sup 14}C, {sup 59}Ni and {sup 94}Nb) with moisture through an unsaturated vault of the near-surface repository in Stabatiske Site. The HYDRUS-1D analysis was used to assess the radionuclide transport in the repository and to estimate initial activity concentrations of radionuclides transported from the cemented waste matrix. Radionuclide release from the vault in the unsaturated conditions after closure of the repository and consequent contaminant plume transport has been assessed taking into account site-specific natural and engineering conditions and based on a normal evolution scenario. The highest peak radionuclide activity concentrations were estimated applying the FEFLOW code. The highest value of {sup 14}C activity concentration(about 1.3x10{sup 8} Bq/m{sup 3}) at the groundwater table

  4. Leaching of U, 230Th and 226Ra from Saskatchewan uranium ore after removing clay

    International Nuclear Information System (INIS)

    Muthuswami, S.V.; Mohd Yunus, M.Z.; Mohamad Nor, M.I.; Kassim, Z.A.; Nirdosh, I.

    1993-01-01

    Distribution of U, 230 Th and 226 Ra in various size fractions in a typical Saskatchewan uranium ore and its resultant mill tailings indicated that less than 4% of these radionuclides were present in the fine ≤ 45 μm) size fraction in the ore whereas their concentration in the similar size fraction in the tailings was > 80%. Removal of clay minerals from the ore by flotation was unsuccessful whereas sedimentation gave nearly complete removal. Leaching of 230 Th from the ore before and after removing clay minerals indicated that dissolution of 230 Th was mproved at higher E h and acidity of the leaching medium and that it was independent of the presence of clay minerals in the ore. (orig.) [de

  5. Simulation of the long term alteration of clay minerals in engineered bentonite barriers: nucleation and growth of secondary clay particles

    International Nuclear Information System (INIS)

    Fritz, B.; Clement, A.; Zwingmann, H.; Noguera, C.

    2010-01-01

    Document available in extended abstract form only. The long term stability of clay rich rocks used as barriers to the migration of radionuclides in the environment of nuclear wastes has been intensively studied, looking at the geochemical interactions between clay minerals and aqueous solutions. These studies combine experimental approaches for the short term and numerical modellings for the long term extrapolations, in the frame of the research supported by ANDRA in the French design for High Level Waste (HLW) repository. The main objective of the geochemical numerical tools devoted to clay-solutions interaction processes was to predict the feed-back effects of mineralogical and chemical transformations of clay mineral, in repository conditions as defined by Andra, on their physical and transport properties (porosity, molecular diffusion, permeability). The 1D transport-reaction coupled simulation was done using the code KIRMAT, at 100 deg. C for 100000 years. The fluid considered is that of the Callovo-Oxfordian geological formation (COX) and assumed to diffuse into the clay barrier from one side. On the other side, ferrous iron, is provided by the steel overpack corrosion. Under these conditions, montmorillonite of the clay barrier is only partially transformed into illite, chlorite, and saponite. The simulation shows that only outer parts of the clay barrier is significantly modified, mainly at the interface with the geological environment. These modifications correspond to a closure of the porosity, followed by a decrease of mass transport by molecular diffusion. Near the COX, the swelling pressure of the clays from the barrier is predicted to decrease, but in its major part, the engineered barrier seems to keep its initial physical properties (porosity, molecular diffusion, permeability, swelling pressure). In this modelling approach, the very important role of secondary clay minerals has to be taken into account with relevant kinetic rate laws; particularly

  6. Research over the extraction process in order to simulate 226Ra and Unat radionuclides migration in uranium waste dumps

    International Nuclear Information System (INIS)

    Bragea, Mihaela; Toro, Laszlo; Cristache, Carmen

    2008-01-01

    To simulate the phenomenon of migration availability of radioactive elements in uranium waste product from waste dump into the environment it was taken into account the Ciudanovita, Romania area with its uranium waste dumps. It were made studies through experiments of static extraction in agitation pot (static regime), which allow to pursue the evolution of contaminants along a specific period of time. It was accomplish a study about sorption and adsorption process on the geological environment (clay). It was observed that 226 Ra and U nat transition through the sorption and adsorption processes were induced by the type of clay (due to variable solubility of clay and the physics and chemical status of 226 Ra and U nat into the clay) and the time interval until the water contacts the clay. The concentration measurements of radionuclides into different dimension of clay particles were made to give pertinent information about the way of chosen the repair strategies for the studied site. The present work is based mainly on this research direction: optimization and improvement of the performances obtained from the geo-chemical processes investigation methods in the waste dumps and the surrounding geological structures to isolate them, in order to reduce the negative environmental impact. Measurements of the two radionuclides concentrations in particles with different dimensions were made to supply accurate information regarding the selection of remediation strategies for the dumpsite in study. (author)

  7. Bentonite erosion: effects on the long term performance of the engineered barrier and radionuclide transport - The BELBAR project

    International Nuclear Information System (INIS)

    Sellin, P.; Sundman, D.; Bailey, L.; Missana, T.; Schaefer, T.; Cervinka, R.; Koskinen, K.

    2012-01-01

    Document available in extended abstract form only. BELBaR is a Collaborative Project within the Seventh Framework Programme of the European Atomic Energy Community (Euratom) for nuclear research and training activities. The main aim of BELBaR is to increase knowledge of the processes that control clay colloid stability, generation and its ability to transport radionuclides. The overall purpose of the project is to come up with a new way of treating issues in long-term safety/performance assessment. The project started March 1, 2012 and has a duration of 48 months. The project has 14 partners from seven European countries. The main aim of BELBaR is to reduce the uncertainties in the description of the effect of clay colloids on the long term performance of the engineered barrier and on radionuclide transport as illustrated in Figure 1. This is done by: - Improving the understanding on when bentonite colloids are unstable. For a given site/site evolution, this is critical information, since it determines whether or not clay colloids need to be included in the long-term assessment. - Improving the quantitative models for erosion on the bentonite barrier for the cases when the colloids are stable - Improving the understanding of how radionuclides attach to clay colloids. This information will be used to formulate improved transport models for the assessment of radionuclide transport in the geosphere. To meet the main aim a number of experimental and modelling activities will be undertaken within the project. BELBaR consists of six RTD (research and technical development) work packages and one project management work package. WP1 will have the responsibility to ensure that that the type and values of the parameters selected for experimental and modelling work are those that represent as much as possible the full range of conditions and situations that can be expected in a repository. Drawing on the work undertaken in WP 2 to 5, the general objective of this work package

  8. Organic migration forms of radionuclides and performance assessment

    International Nuclear Information System (INIS)

    Xu Gouqing

    2010-01-01

    Much attention is paid to inorganic migration forms of radionuclides in groundwater during performance assessment before and organic migration forms, are seldom noted. Therefore some question may come into confidence level in performance assessment. This paper mainly discusses the distribution of organic substances in groundwater and their potential effect on performance assessment. The results obtained in recent years show that clay rocks are generally impermeable to water, but in some cases the interstitial water may be observed in them and the concentration of DOC, HA and FA is rather higher than that in granitic groundwater. The concentration of DOC is relatively low in granitic groundwater, but up to now the effect of organic migration forms of radionuclides in granitic groundwater on performance assessment is not finally determined, it is necessary to make further investigations. (authors)

  9. Two approaches for sequential extraction of radionuclides in soils: batch and column methods

    International Nuclear Information System (INIS)

    Vidal, M.; Rauret, G.

    1993-01-01

    A three-step sequential extraction designed by Community Bureau of Reference (BCR) is applied to two types of soil (sandy and sandy-loam) which had been previously contaminated with a radionuclide aerosol containing 134 Cs, 85 Sr and 110m Ag. This scheme is applied using both batch and column methods. The radionuclide distribution obtained with this scheme depends both on the method and on soil type. Compared with the batch method, column extraction is an inadvisable method. Kinetic aspects seem to be important, especially in the first and third fractions. The radionuclide distribution shows that radiostrontium has high mobility, radiocaesium is highly retained by clay minerals whereas Fe/Mn oxides and organic matter have an important role in radiosilver retention. (Author)

  10. R and D programme on radioactive waste disposal into a clay formation

    International Nuclear Information System (INIS)

    Heremans, R.

    1984-01-01

    The present report presents the main results obtained during the period 1980-82 in the Belgian R and D work on geological disposal of conditioned radioactive waste in the boom clay beneath the Mol site. Multiple research projects have been continued: both experimental research in the field and in the laboratory and theoretical studies. A regional hydrological observation network has been set up which permitted an assessment of the hydrogeological system over- and underlying the Boom clay as well as the modelling of groundwater flow in the area. Clay samples collected during the drilling campaigns were submitted to a number of analyses with a view to chemical characterization and determination of geotechnical properties. Various studies were performed concerning the migration of radionuclides through the clay and an analytical computer model was developed. The corrosion behaviour of various candidate materials for HLW containers and repository linings were tested under different conditions possibly encountered in the clay formation. Furthermore, various backfill and sealing materials and mixtures have been selected and are being tested. Finally, the activities deployed for the safety analysis were continued, mainly concentrated upon two approaches: the probabilistic risk assessment and the performance assessment of a mined repository under normal evolution conditions

  11. Measurement and modelling of reactive transport in geological barriers for nuclear waste containment.

    Science.gov (United States)

    Xiong, Qingrong; Joseph, Claudia; Schmeide, Katja; Jivkov, Andrey P

    2015-11-11

    Compacted clays are considered as excellent candidates for barriers to radionuclide transport in future repositories for nuclear waste due to their very low hydraulic permeability. Diffusion is the dominant transport mechanism, controlled by a nano-scale pore system. Assessment of the clays' long-term containment function requires adequate modelling of such pore systems and their evolution. Existing characterisation techniques do not provide complete pore space information for effective modelling, such as pore and throat size distributions and connectivity. Special network models for reactive transport are proposed here using the complimentary character of the pore space and the solid phase. This balances the insufficient characterisation information and provides the means for future mechanical-physical-chemical coupling. The anisotropy and heterogeneity of clays is represented using different length parameters and percentage of pores in different directions. Resulting networks are described as mathematical graphs with efficient discrete calculus formulation of transport. Opalinus Clay (OPA) is chosen as an example. Experimental data for the tritiated water (HTO) and U(vi) diffusion through OPA are presented. Calculated diffusion coefficients of HTO and uranium species are within the ranges of the experimentally determined data in different clay directions. This verifies the proposed pore network model and validates that uranium complexes are diffusing as neutral species in OPA. In the case of U(vi) diffusion the method is extended to account for sorption and convection. Rather than changing pore radii by coarse grained mathematical formula, physical sorption is simulated in each pore, which is more accurate and realistic.

  12. Modelling of radionuclide transport along the underground access structures of deep geological repositories

    Energy Technology Data Exchange (ETDEWEB)

    Poller, A. [National Cooperative for the Disposal of Radioactive Waste (NAGRA), Wettingen (Switzerland); Smith, P. [SAM Switzerland GmbH, Zuerich (Switzerland); Mayer, G.; Hayek, M. [AF-Consult Switzerland AG, Baden (Switzerland)

    2014-08-15

    The arrangement and sealing of the access routes to a deep geological repository for radioactive waste should ensure that any radionuclide release from the emplacement rooms during the post closure phase does not by-pass the geological barriers of the repository system to a significant extent. The base case of the present study, where realistic values for the hydraulic properties of the seals and the associated excavation damage zones were assumed, assesses to what extent this is actually the case for different layout variants (ramp and shaft access and shaft access only). Furthermore, as a test of robustness of system performance against uncertainties related to such seals and the associated excavation damage zones, the present study also considers a broad spectrum of calculation cases including the hypothetical possibility that the seals perform much more poorly than expected and to check whether, consequently, the repository tunnel system and the access structures may provide significant release pathways. The study considers a generic repository system for high-level waste (HLW repository) and for low- and intermediate-level waste (L/ILW repository), both with Opalinus Clay as the host rock. It also considers the alternative possibilities of a ramp or a shaft as the access route for material transport (waste packages, etc.) to the underground facilities. Additional shafts, e.g. for the transport of persons and for ventilation, are included in both cases. The overall modelling approach consists of three broad steps: (a) the network of tunnels and access structures is implemented in a flow model, which serves to calculate water flow rates along the tunnels and through the host rock; (b) all relevant transport paths are implemented in a radionuclide release and transport model, the water flow rates being obtained from the preceding flow model calculations; (c) individual effective dose rates arising from the radionuclides released from the considered repository

  13. Effects of microstructure of clay on diffusion behavior of radionuclides in buffer materials

    International Nuclear Information System (INIS)

    Ohashi, Hiroshi; Sato, Seichi; Kozaki, Tamotsu

    2001-03-01

    Diffusion behavior of radionuclides in compacted bentonite plays an important role in the performance assessment of bentonite buffer material in geological disposal of high-level radioactive waste. Microstructure of bentonite is considered to be one of the key parameters to affect on the diffusion behavior. In this study, therefore, two kinds of montmorillonite (major clay mineral of bentonite) with different particle sizes were prepared, and characterized with several methods. In addition, the apparent and effective diffusion coefficients of HTO, Cl - , and Cs + were determined using the montmorillonite samples with different particle sizes and dry densities. In the sample characterization, the specific surface areas of montmorillonite samples with different particle sizes were determined by the BET and the EGME methods, and the particle size distributions of each sample were analyzed by laser diffraction/scattering particle size analysis. Microstructure of the samples was also observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The BET method gave a higher specific surface area of the fine grained sample than of the coarse sample, while the EGME method gave same values for both samples. The laser diffraction/scattering particle size analysis using ethanol as a dispersion medium gave different particle size distributions, but when the samples were dispersed in water with Na 6 (PO 3 ) 6 , the particle size distributions were similar. These findings indicate that the montmorillonite layers, which compose the montmorillonite particles, have the same size, even if the particle sizes of the samples are different. In the diffusion experiments, it was found that the apparent diffusion coefficients of HTO and Cl - for the fine grained sample were higher than for the coarse grained sample at two dry densities, 1.0 and 1.8 Mg m -3 , while the opposite particle size effect was observed for Cs + ions. These findings cannot be explained by changes

  14. The UK contribution to the CEC PACOMA Project: far-field modelling of radioactive waste disposal in clay

    International Nuclear Information System (INIS)

    Winters, K.H.; Jackson, C.P.; Clark, C.M.

    1990-06-01

    PACOMA (Performance Assessment of Confinement for Medium-active and Alpha-bearing wastes) is a multinational project supported as part of the Commission of the European Community's R and D programme on radioactive waste management and storage. The aim of the project is to assess the radiological impact of deep geological disposal of intermediate level waste in three different types of geological formation: clay, granite and salt. The contribution of AEA Technology is a study of the groundwater flow and radionuclide migration in the far field. This report describes the far-field modelling. The three-stratum model used in previous hydrogeological studies of the Harwell region is used as a basis for the far-field two-dimensional section through the chalk, clay and Corallian strata underlying Harwell. Each of the three layers is represented as a continuous porous medium with an assumed best-estimate value of permeability, and the groundwater flow is predicted by solving the Darcy equations over the complete section using the NAMMU finite-element code. Two-dimensional transport equations describing the migration of radionuclides in the groundwater are solved, also using NAMMU. The fluxes of radionuclides normal to the surface of the water table are calculated as a function of space and time. The most significant result of the calculations of radionuclide transport through the geosphere is the prediction of multiple pathways for radionuclide movement in the geological strata, and hence multiple release points into the biosphere. Particular attention is paid in the study to the performance and appropriation of the numerical methods and the physical models used for the far-field calculations. (author)

  15. R and D programme on radioactive waste disposal into geological formations (study of a clay formation)

    International Nuclear Information System (INIS)

    Centre d'Etude de l'Energie Nucleaire, Mol

    1987-01-01

    This report deals with the R and D activities performed by the Belgian Nuclear Research Establishment (SCK/CEN) and its subcontractors concerning the disposal of high-level and long-life conditioned wastes in a deep clay formation, the Boom clay. The studies reported concern equally experimental as theoretical work spread over the following research issues: geochemical characterization of the Boom clay, modelling of radionuclide migration in the clay environment, irradiation effects and corrosion behaviour of candidate canister materials in the Boom clay, geomechanical, construction, backfilling and sealing studies related to underground facilities, regional hydrological investigations of the Mol site and safety and risk analysis. The geomechanical and construction-related studies are to a large extent focused on in situ research, performed along the construction of the underground Hades laboratory. The corrosion studies are also dealing with the preparation of in situ experiments in the same underground laboratory. These various research issues are meant to contribute to the assessment of the technical feasibility and safety of the geological disposal in an argillaceous host formation

  16. Radionuclide release from high level waste forms under repository conditions in clay or granite

    International Nuclear Information System (INIS)

    Godon, N.; Lanza, F.

    1990-01-01

    The behaviour of both fully active and simulated vitrified high level waste (HLW) has been studied under conditions that are likely to occur in future repositories in clay and granite. The simulated HLW was doped with Cs, Sr, Tc and the actinides and the leaching of these elements from the glass has been measured together with their concentrations in the water of the near-field and their distribution between the various components of the repository. The diffusion coefficients of several elements in Boom clay has also been measured. The results show that the concentrations of Tc and the actinides in the near-field of a repository will be very low and that the actinides will only diffuse very slowly away from the vicinity of the glass. 24 refs., 1 figs., 7 tabs

  17. Determination of radionuclides and elemental composition of clay soils by gamma and X-ray spectrometry

    International Nuclear Information System (INIS)

    Isinkaye, O. M.; Shitta, O. M. B.; Oderinde, O. M.

    2011-01-01

    Radiochemical and elemental analysis of clay soils collected from different locations within Ekiti State have been performed in this study using gamma and XRF spectrometric measurements. The results of this study show that the mean concentration of 238 U ranged from 2.2±1.0ppm to 3.2±1.1ppm, 232 Th ranged from 4.0±0.5ppm to 5.7±1.7ppm, while 40 K presented in percent by weight ranged from 0.4±0.2 to 1.3±0.3. The XRF analysis revealed 4 major elements and 11 minor or trace elements present in the clay samples. The distribution of the various major and trace elements in all the sampling sites do not follow any systematic trend but vary from point to point. To assess the level of contamination and the possible anthropogenic impact in the clay soils, the enrichment factor (EF) and the geoaccumulation index (Igeo) were estimated for some potential hazardous elements. The results indicate that Cu, Zn, Ni and Mn have EF<2 indicating minimal or no enrichment while Pb is moderately enriched in all the locations.

  18. Effect of carbonate content on the mechanical behaviour of clay fault-gouges

    Science.gov (United States)

    Bakker, Elisenda; Niemeijer, André; Hangx, Suzanne; Spiers, Chris

    2015-04-01

    -rich caprock material we used Opalinus Claystone (Mont Terri, Switserland), which is considered to be an analogue for many shaly caprocks in Europe. We performed rotary shear experiments at in-situ reservoir conditions (T = 20-150˚C, σneff = 50 MPa, Pp = 25 MPa) at shear velocities of 0.22 -100 μm/s. Preliminary results show that the frictional strength of the carbonate-free, natural clay-rich caprock samples is 40-50% lower than for the pure calcite samples. Typical steady-state friction coefficient values obtained for the carbonate-free clay samples are ~0.3-0.4. These values are significantly smaller than the values of ~0.6-0.7 obtained for pure calcite. The friction coefficient values obtained for the mixture plot between the carbonate-free and pure calcite values. The samples show predominantly velocity-strengthening behaviour. However, the 90% pure calcite (and 10% clay-rich caprock) and 100% pure calcite samples show velocity-weakening behaviour at 100-150°C. This suggests that large amounts of carbonates, and thus significant carbonate precipitation as a result of CO2-exposure, are required to cause a transition from aseismic to seismic behaviour, at least under the experimental conditions investigated here.

  19. Treatment and Conditioning of Radioactive Waste Solution by Natural Clay Minerals

    International Nuclear Information System (INIS)

    El-Dessouky, M.I.; Abdel-Raouf, M.W.; El-Massry, E.H.; Khalifa, S.M.; Aly, H.F.

    1999-01-01

    Chemical precipitation processes have been used for the treatment of radioactive elements from aqueous solution. The volume reduction is not very great and storage facilities are expensive. There are some radionuclides which are so difficult to be precipitated by this common method, so they may be precipitated by adding solid materials such as natural inorganic exchangers. In this woek, improvement the removal of caesium, cobalt and europium with zinc sulfate as coagulant and different clay minerals have been investigated. These include, Feldespare, Aswanly, Bentionite, Hematite, Mud, Calcite, Basalt, Magnetite, Kaoline, Sand stone, Limonite and Sand. The parameters affecting the precipitation process such as pH, particle size, temperature and weight of the clay have been studied. The results indicate that, the highest removal for Cs-137, Co-60 and Eu-152 and154 by Asswanly, Bentonite and Sand stone is more than the other clays. Removal of Cs-137 from low level waste solution with these three natural clays took the sequence, Aswanly (85.5%) > Bentonite (82.2%) > Sandstone (65.4%). Solidified cement products have been evaluated to determine mechanical strength and leaching rates of the waste products. The solidified waste forms were found more acceptable for handling ,storage and ultimate disposal

  20. Evaluation of elemental composition of clays from Campos Gerais (MG); Avaliacao da composicao elementar de argilas de Campos Gerais (MG)

    Energy Technology Data Exchange (ETDEWEB)

    Martins, Joao P.M.; Maduar, Marcelo F.; Silva, Paulo S.C da, E-mail: jpmm0697@hotmail.com [Instituto de Pesquisas Energeticas e nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2013-07-01

    There are numerous applications given to clays including oil and water adsorbent, ceramic, whitening of beverages, porcelain, waste treatment, organic carrier molecules in cosmetics and pharmaceuticals, support for catalysts. In the pharmaceutical industry, the clays are used as excipients, diluents, desiccants, emulsifiers, to mask undesirable flavors, isotonic agent such as charger and delivery of active substances. These characteristics have contributed to the expansion of the search for applications of clay minerals in the cosmetic industry. The aim of this study was to determine the elemental composition of clays from Campos Gerais, Minas Gerais, with a view to their applicability in the production of cosmetics. The elements As, Ba, Br, Ce, Cl, Co, Cr, Cs, Eu, Fe, Hf, K, La, Lu, Na, Nd, Rb, Sb, Sc, Sm, Ta, Tb, Th,U, Yb and Zn were determined by neutron activation analysis and radionuclide activity concentration of {sup 226}Ra, {sup 228} Ra, {sup 210}Pb and {sup 40}K were determined by gamma spectrometry. It was verified that the activity concentration of radionuclides was in the same concentration as the global average, indicating that these samples do not present a risk of increased radiation exposure. The concentration of most elements determined is less than or equal to the overall mean concentrations, indicated by the values of Continental Upper Crust. (author)

  1. Interaction and transport of actinides in natural clay rock with consideration of humic substances and clay organics. Characterization and quantification of the influence of clay organics on the interaction and diffusion of uranium and americium in the clay. Joint project

    International Nuclear Information System (INIS)

    Bernhard, Gert; Schmeide, Katja; Joseph, Claudia; Sachs, Susanne; Steudtner, Robin; Raditzky, Bianca; Guenther, Alix

    2011-01-01

    and entropy-driven. In contrast, the complex stability constants determined for U(VI) humate complexation at 20 and 40 C are comparable, however, decrease at 60 C. For aqueous U(IV) citrate, succinate, mandelate and glycolate species stability constants were determined. These ligands, especially citrate, increase solubility and mobility of U(IV) in solution due to complexation. The U(VI) sorption onto crushed Opalinus Clay (OPA, Mont Terri, Switzerland) was studied in the absence and presence of HA or low molecular weight organic acids, in dependence on temperature and CO2 presence using OPA pore water as background electrolyte. Distribution coefficients (K d ) were determined for the sorption of U(VI) and HA onto OPA with (0.0222 ± 0.0004) m 3 /kg and (0.129 ± 0.006) m 3 /kg, respectively. The U(VI) sorption is not influenced by HA (≤50 mg/L), however, decreased by low molecular weight organic acids (≥ 1 x 10 -5 M), especially by citrate and tartrate. With increasing temperature, the U(VI) sorption increases both in the absence and in the presence of clay organics. The U(VI) diffusion in compacted OPA is not influenced by HA at 25 and 60 C. Predictions of the U(VI) diffusion show that an increase of the temperature to 60 C does not accelerate the migration of U(VI). With regard to uranium-containing waste, it is concluded that OPA is suitable as host rock for a future nuclear waste repository since OPA has a good retardation potential for U(VI). (orig.)

  2. Interaction and transport of actinides in natural clay rock with consideration of humic substances and clay organics. Characterization and quantification of the influence of clay organics on the interaction and diffusion of uranium and americium in the clay. Joint project

    Energy Technology Data Exchange (ETDEWEB)

    Bernhard, Gert [Helmholtz-Zentrum Dresden-Rossendorf e.V. (Germany). Inst. of Radiochemistry; Schmeide, Katja; Joseph, Claudia; Sachs, Susanne; Steudtner, Robin; Raditzky, Bianca; Guenther, Alix

    2011-07-01

    , was found to be endothermic and entropy-driven. In contrast, the complex stability constants determined for U(VI) humate complexation at 20 and 40 C are comparable, however, decrease at 60 C. For aqueous U(IV) citrate, succinate, mandelate and glycolate species stability constants were determined. These ligands, especially citrate, increase solubility and mobility of U(IV) in solution due to complexation. The U(VI) sorption onto crushed Opalinus Clay (OPA, Mont Terri, Switzerland) was studied in the absence and presence of HA or low molecular weight organic acids, in dependence on temperature and CO2 presence using OPA pore water as background electrolyte. Distribution coefficients (K{sub d}) were determined for the sorption of U(VI) and HA onto OPA with (0.0222 {+-} 0.0004) m{sup 3}/kg and (0.129 {+-} 0.006) m{sup 3}/kg, respectively. The U(VI) sorption is not influenced by HA ({<=}50 mg/L), however, decreased by low molecular weight organic acids ({>=} 1 x 10{sup -5} M), especially by citrate and tartrate. With increasing temperature, the U(VI) sorption increases both in the absence and in the presence of clay organics. The U(VI) diffusion in compacted OPA is not influenced by HA at 25 and 60 C. Predictions of the U(VI) diffusion show that an increase of the temperature to 60 C does not accelerate the migration of U(VI). With regard to uranium-containing waste, it is concluded that OPA is suitable as host rock for a future nuclear waste repository since OPA has a good retardation potential for U(VI). (orig.)

  3. Conceptual and numerical modelling of radionuclide transport in near-surface systems at Forsmark. SR-Site Biosphere

    International Nuclear Information System (INIS)

    Pique, Angels; Grandia, Fidel; Sena, Clara; Arcos, David; Molinero, Jorge; Duro, Lara; Bruno, Jordi

    2010-11-01

    In the framework of the SR-Site safety assessment, a conceptual and numerical modelling of radionuclide reactive transport in near-surface systems (including till and clay systems) at Forsmark has been carried out. The objective was to evaluate the retention capacity of the near-surface systems, composed of Quaternary deposits, which would be the last natural barrier for an eventual radionuclide release from the deep repository prior to reaching the biosphere. The studied radionuclides are 14 C, 129 I, 36 Cl, 94 Nb, 59 Ni, 93 Mo, 79 Se, 99 Tc, 230 Th, 90 Sr, 226 Ra, 135 Cs and U. Conceptual description and numerical simulations of radionuclide reactive transport show that cation exchange and surface complexation on illite are active processes for the retention of several radionuclides (U, Th, Ni, Cs, Sr, Ra). Surface complexation on iron hydroxide is an active process in the till system, able to effectively retain U and Ni. Another retention process of importance is the incorporation of the radionuclides into mineral phases, either by the precipitation of pure phases or solid solutions. Quantitative modelling has been useful to illustrate the incorporation of C and Sr in the carbonate solid solution in the considered model domains (till and clay), as well as the precipitation of uraninite in the clay sediments and the precipitation of native selenium and radiobarite in the till. Other mineral phases that could, a priori, retain U, Se, Nb and Tc do not precipitate in the simulations, either due to the pH-Eh conditions and/or because the dissolved concentration of the element is not high enough under the considered simulation conditions. It is important to keep in mind that changes in these parameters and in the boundary conditions could modify the predicted behaviour of these elements. The radionuclides that are most significantly retarded are Th, Ni and Cs, mainly through sorption onto illite. Therefore, if the amount of illite (or available sorption sites

  4. Conceptual and numerical modelling of radionuclide transport in near-surface systems at Forsmark. SR-Site Biosphere

    Energy Technology Data Exchange (ETDEWEB)

    Pique, Angels; Grandia, Fidel; Sena, Clara; Arcos, David; Molinero, Jorge; Duro, Lara; Bruno, Jordi (Amphos21 Consulting S.L., Barcelona (Spain))

    2010-11-15

    In the framework of the SR-Site safety assessment, a conceptual and numerical modelling of radionuclide reactive transport in near-surface systems (including till and clay systems) at Forsmark has been carried out. The objective was to evaluate the retention capacity of the near-surface systems, composed of Quaternary deposits, which would be the last natural barrier for an eventual radionuclide release from the deep repository prior to reaching the biosphere. The studied radionuclides are 14C, 129I, 36Cl, 94Nb, 59Ni, 93Mo, 79Se, 99Tc, 230Th, 90Sr, 226Ra, 135Cs and U. Conceptual description and numerical simulations of radionuclide reactive transport show that cation exchange and surface complexation on illite are active processes for the retention of several radionuclides (U, Th, Ni, Cs, Sr, Ra). Surface complexation on iron hydroxide is an active process in the till system, able to effectively retain U and Ni. Another retention process of importance is the incorporation of the radionuclides into mineral phases, either by the precipitation of pure phases or solid solutions. Quantitative modelling has been useful to illustrate the incorporation of C and Sr in the carbonate solid solution in the considered model domains (till and clay), as well as the precipitation of uraninite in the clay sediments and the precipitation of native selenium and radiobarite in the till. Other mineral phases that could, a priori, retain U, Se, Nb and Tc do not precipitate in the simulations, either due to the pH-Eh conditions and/or because the dissolved concentration of the element is not high enough under the considered simulation conditions. It is important to keep in mind that changes in these parameters and in the boundary conditions could modify the predicted behaviour of these elements. The radionuclides that are most significantly retarded are Th, Ni and Cs, mainly through sorption onto illite. Therefore, if the amount of illite (or available sorption sites) decreases, the

  5. R7T7 nuclear waste glass behavior in moist clay: role of the clay mass/glass surface area ratio

    International Nuclear Information System (INIS)

    Godon, N.; Vernaz, E.

    1989-01-01

    R7T7 glass alteration was investigated in the presence of various moist clays. In contact with smectite 4a, selected in France as a potential engineered barrier material, the glass was significantly corroded: after 6 months the glass corrosion rate was practically the same as the initial alteration rate in double-distilled water. Substantially lower alteration was observed in contact with bentonite 6 activated by sodium carbonate. Smectite 4a consumes silicon released by glass corrosion, and thus retards the rise to high silicon concentrations in solution at which the glass corrosion rate diminishes. Glass can therefore in some cases be altered as much in moist clay as in water with high renewal rates. Other experiments with smaller quantities of smectite 4a showed that the phenomenon becomes less important in time: its duration is proportional to the ratio between the clay mass (C) and the glass surface area (SA). Comparing the results of studies at different C/SA ratios indicates that low glass corrosion rates are obtained more slowly at higher C/SA ratios. Tests with 239 Pu-doped R7T7 glass also showed that the radionuclide retention factor in the alteration film at the glass surface is only 6, compared with a factor of nearly 50 in double-distilled water

  6. Use of swelling clays to reduce permeability and its potential application to nuclear waste repository sealing

    International Nuclear Information System (INIS)

    Moore, D.E.; Morrow, C.A.; Byerlee, J.D.

    1982-01-01

    The injection of swelling-clay slurries into joints or faults at a deep-burial nuclear waste disposal site may result in signficant permeability reductions for the effective containment of radioactive wastes. In an experiment conducted to illustrate the permeability change accompanying clay swelling, a coarse stone with interconnected pore spaces was injected with a clay-electrolyte slurry, modelling the pressure-grouting of a fractured repository rock. Subsequently, solutions with lower electroylte concentrations were driven through the clay-filled stone, corresponding to migration of lower salinity ground-waters through the clay-grouted fracture. The initial injection procedure reduced the permeability of the stone from 1--10 darcies to 700 nanodarcies; the changes in solution composition decreased permeability by more than 2 additional orders of magnitude to 3 nanodarcies. For application at a nuclear waste repository, the electrolyte concentration of the injected clay slurry should be made higher than that of the ground-water in the host rock. Subesquent interaction of the ground-water with the clays would initiate swelling and create the additional, post-injection permeability reductions that may be important in preventing the escape of buried radioactive wastes. The measured permeability of the clay filling is considerably lower than that of cement tested for borehole plugging. Clays also have the advantage over cement and chemical grouts in that they are geologically stable at relatively low temperatures and have a high capacity for radionuclide adsorption

  7. Mechanisms controlling radionuclide mobility in forest soils

    International Nuclear Information System (INIS)

    Delvaux, B.; Kruyts, N.; Maes, E.; Agapkina, G.I.; Kliashtorin, A.; Bunzl, K.; Rafferty, B.

    1996-01-01

    Soil processes strongly influence the radionuclide mobility in soils. The mobility of radionuclides in forest soils is governed by several processes involving both abiotic and biotic factors. The sorption-desorption process chiefly governs the activity of radionuclides in the soil solution, hence thereby their mobility and biological availability. Radiocaesium exhibits a very low mobility in mineral soils. Both mobility and bioavailability however increase as the thickness of organic layers and their content in organic matter increases. Clay minerals of micaceous origin strongly act as slinks for radiocaesium in forest soils. The magnitude of cesium mineral fixation in topsoils is expected to be the highest in mineral soils of Eutric cambisol type, and, to a lesser extent, of type of Distric cambisol and Podzoluvisol. A low mobility of radiocaesium in the surface horizons of forest soils may also be partially explained by a biological mobilization: fungi absorb radiocaesium and transport it to upper layers, thereby contributing to constantly recycle the radioelement in the organic horizons. This mechanism is probably important in soils with thick organic layers (Podsol, Histosol, and, to a lesser extent, Distric cambisol and Podzoluvisol). Radionuclides can be associated with soluble organic anions in the soil solution of forest acid soils. Such associations are highly mobile: they are stable in conditions of poor biological activity (low temperatures, acid soil infertility, water excess, etc.). Their magnitude is expected to be the highest in thick acid organic layers (soils of type Podzol and Histosol)

  8. Public Health Goal for Naturally Occurring Radionuclides in Groundwater

    International Nuclear Information System (INIS)

    Kamel, N.H.M.; Omar, H.A.; El-Baset, L.A.

    2008-01-01

    Naturally occurring and man-made radionuclide in groundwater may have a health hazardous to some residents. The objective of this work is to provide criteria for safety of drinking-water with respect to the chemical parameters and the radionuclide content. The annual effective dose for the consumption of drinking water was considered. Ground water samples were selected from different sites in Egypt, that have the most population, it were taken from aquifer regions along Giza sites in Egypt. Chemical analyses for the major anions, cations, and the radiological analyses were tested . Activity concentrations (Bq/l) of the gross alpha and the gross beta activities of our investigated samples were compared with the maximum contaminant level (MCL) of the world health organization (WHO). Some of the water samples were found to have a higher of gross beta and alpha particles than the MCL. Alpha activity were found depending on to the total dissolved solids (TDS) content of the water samples. Gamma activity concentrations were analyzed using low background germanium detector, the higher of activity values was found in some investigated samples is due to increasing of 226 Ra and 228 Ra activities. Tritium activity concentrations also were measured using soft beta liquid scintillation counter, it was found lower than the MCL. Our investigated samples were found to have a higher concentrations of the phosphate, nitrites, iron, and manganese contents than the maximum permissible limit, all the ground water samples were found to have a higher of silica and alumina content. Commercial carbon powder and natural clay materials were tested as ion exchangers for the removal of inorganic contaminants in the ground water samples. Clay materials was found to have a higher selectivity than activated carbon for the removal of radionuclides, phosphates, nitrites, and manganese content at the ground water samples

  9. Natural gamma-emitting radionuclides in egyptian cement

    International Nuclear Information System (INIS)

    El Arabi, A.M.; Abbady, A.; El Kamel, A.H.; Nosier, A.; Moustafa, A.

    2005-01-01

    Samples of cement manufactured in Egypt and the various raw materials, which compose the product, have been analyzed using gamma-spectroscopy, in order to determine the concentration of natural radionuclides and associated radiological hazard. The mean of specific activity due to all the three radionuclides (226 R a, 232 T h and 40 K ) were found to be 20±4 , 11± 2, 320 ± 18 (gypsum), 41 ±8, 27± 5, 410± 27 (clay), 58 ± 11, 18 3, 321± 20 (Iron ore) and 37.6 ± 6, 11.8 ± 3, 178.6 ± 15 Bq.kg-1 (Portland cement), respectively. 40 K concentration could not be detected in Slag; limestone; Sulphate resistant cement; Clinker and White cement, while the mean activity concentrations of 226 R a and 232 T h are 239 ± 16, 48.7 ± 7; 31.5 ±5, 10 ± 2; 47 ± 7, 20 ± 4; 23 ± 5, 10.4 ± 3 and 23 ± 5, 11 ±3 Bq.kg-1, respectively. The measured activity concentrations of these natural radionuclides were compared with data of some countries. The present values are in the same range and sometimes less than those in other countries

  10. Natural gamma-emitting radionuclides in egyptian cement

    International Nuclear Information System (INIS)

    El-Arabi, A.M.; Abbady, A.; El-Kamel, A.H.; Nosier, A.; Moustafa, A.

    2005-01-01

    Samples of cement manufactured in Egypt and the various raw materials, which compose the product, have been analyzed using gamma-spectroscopy, in order to determine the concentration of natural radionuclides and associated radiological hazard. The mean of specific activity due to all the three radionuclides (226 R a, 232 T h and 40 K ) were found to be 20 ± 4 , 11 ± 2, 320 ± 18 (gypsum), 41 ± 8, 27 ± 5, 410 ± 27 (clay), 58 ± 11, 18 3, 321 ± 20 (Iron ore) and 37.6 ± 6, 11.8 ± 3, 178.6 ± 15 Bq.kg-1 (Portland cement), respectively. 40 K concentration could not be detected in Slag; limestone; Sulphate resistant cement; Clinker and White cement, while the mean activity concentrations of 226 R a and 232 T h are 239 ± 16, 48.7 ± 7; 31.5 ± 5, 10 ± 2; 47 3 ± 7, 20 ± 4; 23 ± 5, 10.4 ± 3 and 23 ± 5, 11 ± 3 Bq.kg-1, respectively. The measured activity concentrations of these natural radionuclides were compared with data of some countries. The present values are in the same range and sometimes less than those in other countries

  11. Interaction of selected actinides (U, Cm) with bacteria relevant to nuclear waste disposal

    Energy Technology Data Exchange (ETDEWEB)

    Luetke, Laura

    2013-07-01

    To assess the safety of a site destined for storage of nuclear waste enhanced research effort is demanded to investigate the complex interactions of released radionuclides with parts of the environment that includes indigenous microorganisms. This work aimed at assessing the interactions of two bacterial strains with the actinides uranium and curium with a focus on thermodynamics to provide stability constants of the actinide bacteria species formed usable for modelling the distribution of these actinides in the environment. The influences of Pseudomonas fluorescens (CCUG 32456A) isolated from the granitic aquifers at Aespoe(Sweden) and a novel isolate from Mont Terri Opalinus clay (Switzerland), Paenibacillus sp. MT-2.2, were investigated. A combined approach using microbiological and spectroscopic techniques as well as potentiometry was employed to characterize the U(VI) and Cm(III) binding onto the cell surface functional groups structurally and thermodynamically. Further, due to its similar ionic radius to Cm(III) also Eu(III) was studied as non-radioactive analog.

  12. Synthesis and characterization of surfactant immobilised layered hydrotalcite clays for the adsorption of thorium (IV) from aqueous phase: kinetics and equilibrium study

    International Nuclear Information System (INIS)

    Rijith, S.; Renju, K.; Sumi, V.S.; Shibli, S.M.A.; Anirudhan, T.S.

    2014-01-01

    Thorium is a naturally occurring radioactive element widely distributed over the earth's crust with nuclear significance. The toxic nature of this radionuclide, even at trace levels, has been a public health problem for many years. Removal of thorium (IV) from aqueous solutions with surfactant immobilised calcined hydrotalcite clays (HTS) was investigated using batch adsorption technique. Based on cost effectiveness, availability, adsorptive and regenerative properties, layered clays are reported to be excellent materials for heavy metal ions adsorption

  13. High-level waste repository-induced effects

    Energy Technology Data Exchange (ETDEWEB)

    Leupin, O.X.; Marschall, P.; Johnson, L.; Cloet, V.; Schneider, J. [National Cooperative for the Disposal of Radioactive Waste (NAGRA), Wettingen (Switzerland); Smith, P. [Safety Assessment Management Ltd, Henley-On-Thames, Oxfordshire (United Kingdom); Savage, D. [Savage Earth Associates Ltd, Bournemouth, Dorset (United Kingdom); Senger, R. [Intera Inc., Ennetbaden (Switzerland)

    2016-10-15

    by restricting the size of the excavations and the depth of the repository, using a low-deformation, controlled construction and excavation method and by the fact that the excavations will be backfilled relatively soon after construction with a swelling backfill material. At expected repository depths, the rooms will need to be supported to ensure stability and worker protection; this will prevent rock falls and further extension of the EDZ. Based on the modelling results, it can be concluded that the extent of the EDZ around the HLW emplacement rooms will not exceed a thickness of one room diameter and that the average hydraulic conductance of the EDZ around emplacement rooms, access tunnels and shafts will not exceed a value of 10{sup -7} m{sup 3}/s. Self-sealing of the EDZ and low hydraulic gradients along the tunnels will result in negligible radionuclide transport by the EDZ pathway. The relevant chemical interactions are taken into account when designing and assessing the performance of a HLW repository. In the current reference design, tunnel support is provided by a concrete liner. It is expected that degradation of the liner and corrosion of the steel canister and other supporting structures will lead to some alteration of the bentonite buffer and Opalinus Clay. These detrimental effects are taken into account in dose calculations and have been found not to have a significant impact on the calculated dose rates. For the reference gas generation rates, the gas transport capacity of the Opalinus Clay is sufficiently high to dispel gas without invoking pathway dilation as a gas transport mechanism and without causing damage to the rock. Even if potential transport pathways for gas along the excavations and EDZ are disregarded, overpressures that would lead to the onset of pathway dilation are reached only in cases combining conservative gas generation rates with a low-permeability host rock, and these overpressures are still insufficient to cause rock damage

  14. High-level waste repository-induced effects

    International Nuclear Information System (INIS)

    Leupin, O.X.; Marschall, P.; Johnson, L.; Cloet, V.; Schneider, J.; Smith, P.; Savage, D.; Senger, R.

    2016-10-01

    by restricting the size of the excavations and the depth of the repository, using a low-deformation, controlled construction and excavation method and by the fact that the excavations will be backfilled relatively soon after construction with a swelling backfill material. At expected repository depths, the rooms will need to be supported to ensure stability and worker protection; this will prevent rock falls and further extension of the EDZ. Based on the modelling results, it can be concluded that the extent of the EDZ around the HLW emplacement rooms will not exceed a thickness of one room diameter and that the average hydraulic conductance of the EDZ around emplacement rooms, access tunnels and shafts will not exceed a value of 10 -7 m 3 /s. Self-sealing of the EDZ and low hydraulic gradients along the tunnels will result in negligible radionuclide transport by the EDZ pathway. The relevant chemical interactions are taken into account when designing and assessing the performance of a HLW repository. In the current reference design, tunnel support is provided by a concrete liner. It is expected that degradation of the liner and corrosion of the steel canister and other supporting structures will lead to some alteration of the bentonite buffer and Opalinus Clay. These detrimental effects are taken into account in dose calculations and have been found not to have a significant impact on the calculated dose rates. For the reference gas generation rates, the gas transport capacity of the Opalinus Clay is sufficiently high to dispel gas without invoking pathway dilation as a gas transport mechanism and without causing damage to the rock. Even if potential transport pathways for gas along the excavations and EDZ are disregarded, overpressures that would lead to the onset of pathway dilation are reached only in cases combining conservative gas generation rates with a low-permeability host rock, and these overpressures are still insufficient to cause rock damage. It is

  15. Clay membrane made of natural high plasticity clay

    DEFF Research Database (Denmark)

    Foged, Niels; Baumann, Jens

    1998-01-01

    Leachate containment in Denmark has through years been regulated by the DIF Recommendation for Sanitary Landfill Liners (DS/R 466). It states natural clay deposits may be used for membrane material provided the membrane and drainage system may contain at least 95% of all leachate created throughout...... ion transport as well as diffusion.Clay prospection for clays rich in smectite has revealed large deposits of Tertiary clay of very high plasticity in the area around Rødbyhavn on the Danish island Lolland. The natural clay contains 60 to 75% smectite, dominantly as a sodium-type. The clay material...... has been evaluated using standardised methods related to mineralogy, classification, compaction and permeability, and initial studies of diffusion properties have been carried out. Furthermore, at a test site the construction methods for establishing a 0.15 to 0.3m thick clay membrane have been tested...

  16. Clay membrane made of natural high plasticity clay:

    DEFF Research Database (Denmark)

    Foged, Niels; Baumann, Jens

    1999-01-01

    Leachate containment in Denmark has throughout the years been regulated by the DIF Recommendation for Sanitary Landfill Liners (DS/R4669. It states that natural clay deposits may be used as membrane material provided the membrane and drainage system contains at least 95% of all leachate created...... into account advective ion transport as well as diffusion. Clay prospecting for clays rich in smectite has revealed large deposits of Tertiary clay of very high plasticity in the area around Rødbyhavn on the Danish island of Lolland. The natural clay contains 60-75% smectite, dominantly as a sodium......-type. The clay material has been evaluated using the standardized methods related to mineralogy, classification, compaction and permeability, and initial studies of diffusion properties have been carried out. Furthermore, at a test site the construction methods for establishing a 0.15-0.3 m thick clay membrane...

  17. The redox properties of the natural iron-bearing clay mineral ferruginous smectite SWA-1: a combined electrochemical and spectroscopic study

    International Nuclear Information System (INIS)

    Gorski, Christopher A.; Voegelin, Andreas; Sander, Michael; Hofstetter, Thomas B.

    2012-01-01

    Document available in extended abstract form only. Iron-bearing clay minerals are ubiquitous in the environment and clay-mineral-based materials have been proposed to be part of backfill material in nuclear waste repositories. Laboratory and field studies have confirmed that structural iron (Fe) in clay minerals participates in redox reactions with organic pollutants, metals, and radionuclides, thus influencing their transport and reactivity. Knowledge of the redox properties of Fe-bearing clay minerals is therefore essential for understanding and predicting the fate, mobility, and bioavailability subsurface contaminants. A quantitative understanding of clay mineral redox behavior remains lacking, however, due to constraints in previous experimental approaches and the complex structural changes that accompany changes in the Fe oxidation state. This work provides a quantitative means for measuring the redox properties of Fe-bearing clay minerals, which can be applied to both field and laboratory studies tracking radionuclide-clay mineral redox reactions. Here we use mediated electrochemical reduction and oxidation to determine the electron accepting and donating capacities of several natural Fe-bearing clay minerals with different structural Fe content (2.3 to 21 wt-%) and varied redox histories. Results indicate that the fraction of redox-active Fe in clay minerals is mineral-dependent, and is linked to the thermodynamics of reduction and oxidation as well as to the ability of clay minerals to conduct electrons and facilitate structural re-arrangements required to maintain charge balance. The reduction potential (E H ) characteristics of a natural ferruginous smectite (SWa-1) were further characterized as a function of solution conditions and repeated Fe reduction and oxidation cycles. SWa-1 samples were analyzed with Moessbauer spectroscopy (MS) and X-ray absorption spectroscopy (XAS) to link observed redox potential behavior to structural properties and changes

  18. Migration of 137Cs artificial radionuclide in the valley of the Takhtakushuk river of the Degelen massif

    International Nuclear Information System (INIS)

    Panitskij, A.V.

    2005-01-01

    Study of horizontal and vertical radionuclide distribution in the valley of the Takhtakushuk River of the 'Degelen' Massif is carried out in the framework of ecological and biological investigations of soil and plant cover within radioactive contaminated areas, and radionuclide migration in biological chain 'soil - plant - animal'. For the first time, the pool-type method was used in the studies of soil of the valley that allows tracing solid and liquid substances migrating by means of surface and soil drainage from its head to final part. This paper presents some physical and chemical properties of the study landscape's soils, radionuclide content in soil genetic horizons of the valley. The study results showed that major mass of 137 Cs radionuclide is sorbed by soil humus and fine-dispersed clay particles of grass soils within the valley. (author)

  19. Natural radionuclides in meadow and pasture land in the Nordic countries

    International Nuclear Information System (INIS)

    Rosen, K.; Gutierrez Villanueva, J.-L.; Sundell-Bergman, S.

    2012-06-01

    different soil types such as sandy, organic and/or clay soil was investigated. The use of fertilizers at some of the investigated farms has been considered but no analysis was performed on the content of natural radionuclides in fertilisers. (Author)

  20. Natural radionuclides in meadow and pasture land in the Nordic countries

    Energy Technology Data Exchange (ETDEWEB)

    Rosen, K.; Gutierrez Villanueva, J.-L.; Sundell-Bergman, S. [Swedish Univ. of Agricultural Sciences (SLU) (Sweden)] [and others

    2012-06-15

    different soil types such as sandy, organic and/or clay soil was investigated. The use of fertilizers at some of the investigated farms has been considered but no analysis was performed on the content of natural radionuclides in fertilisers. (Author)

  1. Coupled transport and chemistry in clay stone studied by advective displacement: experiments and model

    International Nuclear Information System (INIS)

    Landesman, C.; Grambow, B.; Bailly, C.; Ribet, S.; Perrigaud, K.; Baty, V.; Giffaut, E.

    2010-01-01

    Document available in extended abstract form only. Full text of publication entered in this record. For assessing the mass transfer resistance of the Callovo-Oxfordian clay rock formation in case of implementing a nuclear waste repository, various strongly coupled processes need to be understood and quantified both in near and far field: multi-species diffusion/advection, mineral/pore water interaction, interaction with the waste matrix and engineered barrier material, radionuclide retention, colloid transport, pore water chemistry evolution etc. To study many of these processes in their interrelationship simultaneously, a series of high pressure stainless steel advection cell was designed and clay cores from different locations of different calcite and clay contents were machined to fit the inner diameter of the cells with a precision of 50 μm. After assembling, simulated oxygen free clay pore water with bromine tracer was pushed by a High Pressure pump through the reactor by a pressure of up 100 bars at temperatures between 20 and 90 deg. C and the out-flowing water was collected, protected from air and analyzed by ICP-MS, COT meter and ion chromatography in regular time intervals. The water flow rate was between 0.02 and 1.2 mL/ d, corresponding to a clay rock permeabilities between 10 -12 and 10 -14 m/s at 25 deg. C. Permeabilities increase with temperature as expected due to reduction of viscosity of water. The experiments last up to 2 years. The first drops of out flowing allow estimating the initial pore water composition. This is particular useful to assess mobile natural organic matter contents, Se concentrations and temperature effect on clay water composition. Results show that only very small organic molecules are mobile. Temperature had only little effect on water composition. After few months both tritiated (HTO) water and 36 Cl were added and from the evolution of the activities in the out flowing water dispersion coefficients and accessible

  2. Clay Play

    Science.gov (United States)

    Rogers, Liz; Steffan, Dana

    2009-01-01

    This article describes how to use clay as a potential material for young children to explore. As teachers, the authors find that their dialogue about the potential of clay as a learning medium raises many questions: (1) What makes clay so enticing? (2) Why are teachers noticing different play and conversation around the clay table as compared to…

  3. Hydro-mechanical properties of the red salt clay (T4) - Natural analogue of a clay barrier

    International Nuclear Information System (INIS)

    Minkley, W.; Popp, T.; Salzer, K.; Gruner, M.; Boettge, V.

    2010-01-01

    -scale proof of final disposal safety of bedded salt repository covered by a Salt Clay layer was performed by numerical back-analyses of rock bursts occurred in several potash and rock salt mines. Despite of dynamical loadings with magnitudes of M L = 3...5.6 and overburden subsidence of several decimetres to a few meters the geological barrier consisting of rock salt and salt clay in direct vicinity to aquiferous layers remained its tightness. Our study confirms the favourable properties of argillaceous clay formations for storage of radioactive waste but it becomes also clear that a combination of the advantages of both host rocks, i.e. the unique isolation capacity of rock salt as well with the water tightness and absorption capacity of clay formations against radionuclides, can significantly improve the barrier properties. The flat bedded Zechstein salt deposits in Germany represent already a natural geological multi-barrier-system consisting of rock salt and clay horizons. In case of a site selection procedure for a final disposal site for heat-generating radioactive waste in Germany, according to AkEnd, such geological situations should be preferred. (authors)

  4. The petrography of the Jurassic core from the Harwell research site. Part 1: Kimmeridge Clay, Corallian Beds and Oxford Clay

    International Nuclear Information System (INIS)

    Milodowski, A.E.

    1983-06-01

    Detailed examination by mineralogical and petrological techniques has enabled a detailed characterisation of the lithologies of the Oxford Clay, Corallian Beds and the Kimmeridge Clay beneath the Harwell Research Site. Information obtained has revealed the nature of the bulk mineralogy, pore-types, pore-surface mineralogy and post-depositional alteration of the rocks. Diagenesis has played an important part in determining the mineralogy, porosity and fabric of the rocks and has had the greatest variation of effects in the Corallian Beds, determining the phases now in contact with groundwater. It is these authigenic phases that are of key interest in assessing the behaviour of radionuclides which may be released into the local groundwater systems. The importance of the different pore-types characterised during this investigation and of the mineral phases lining these potential pathways for groundwater movement are discussed in detail at the end of this report. Diagenesis has reduced primary porosity in many of the Corallian rocks by calcite precipitation. In such rocks where a cohesive cement is present, groundwater flow must occur along large-scale fractures and more slowly along intercrystalline grain-boundary cracks. (author)

  5. Retention and radionuclide migration mechanisms in the environment of a radioactive waste repository in granitic formation

    International Nuclear Information System (INIS)

    Rancon, D.; Miara, P; Vinson, J.M.; Petronin, J.C.; Dozol, J.F.

    1986-01-01

    A laboratory pre-determination of retention mechanisms of radionuclides migrating outside the primary waste containers in repository surroundings was started up. Backfillings materials (clay and sand) as well as granite and its weathering products are concerned here. A method allowing the evaluation of the sorption and desorption of radionuclides of the surfaces of fractures by measuring surface retention coefficients, had initially been started up as well as a laboratory device developed for experiments in a reducing environment. The experiments have consisted of studying the sorbing properties of granite minerals of Auriat and its weathering products and of determining the retention of Np, Pu, AM, CS and Sr on the surface fractures of this granite. The influence of a reducing environment on the behaviour of activities has been studied. Complementary percolation tests have also been carried out on clays, at raised temperature and under irradiation. These experiments have enabled a deeper knowledge of retention mechanisms, the taking of parametric sensitivity measurements and the preparation of elaborating more performing experimental devices which included the parameters needed for a realistic simulation of transfer phenomena

  6. Probabilistic safety assessment for a generic deep geological repository for high-level waste and long-lived intermediate-level waste in clay

    International Nuclear Information System (INIS)

    Resele, G.; Holocher, J.; Mayer, G.; Hubschwerlen, N.; Niemeyer, M.; Beushausen, M.; Wollrath, J.

    2010-01-01

    probabilistic safety assessment, including the probabilities of the scenarios. - Evaluation of the significance of the results. Probabilistic calculations of the radionuclide release from the wastes and the transport through the host rock formation and overlying rock are the basis for the derivation of indicator values that weight the resulting radiologic consequences of the radionuclide release in the biosphere. These indicator values will be used to perform the comparison of the safety assessments of the repositories at the clay site and at the salt site. For the clay site, using the Monte Carlo simulation software GoldSim as platform for the system-level probabilistic simulations, the radionuclide release and transport is modelled in two steps: First, the 2-phase flow considering gas generation in the repository due to anaerobic steel corrosion is calculated using TOUGH2-MP. Besides the flow, the propagation of an ideal tracer that is released from the waste forms is simulated. In a second step, the resulting water flow out of the emplacement caverns is used as input in corresponding radionuclide transport calculations with the numerical code VPAC. VPAC simulates groundwater flow and radionuclide release and transport in fully saturated heterogeneous media in 3D, considering radioactive decay and ingrowth for the total set of safety-relevant radionuclides, solubility limitations, time-dependent hydraulic conductivities, time-dependent diffusion and time-dependent sorption. Besides the gas-induced water flow from the repository, the distribution of the tracer as calculated with TOUGH2-MP is used as input to the VPAC calculations. Due to the large and complex architecture of the repository, a detailed 3D modeling of the radionuclide transport in the repository system and the entire host rock and overlying rock would require a tremendous computational effort. Therefore, only the transport along the dominating pathway is simulated using VPAC. This dominating pathway is

  7. Radium equivalent in clays extracted in Northeast cities of Brazil and used in civil construction

    International Nuclear Information System (INIS)

    Araujo, Eduardo E.N.; Junior, Jose Araujo S.; Amaral, Romilton S.; Santos, Josineide M.N.; Rojas, Lino A.V.; Fernandez, Zahily H.

    2017-01-01

    The Earth's crust may have different levels of natural radioactivity as a consequence of the different types of minerals that form its composition. Exploration activities of natural sources may have a high radiometric impact for the radionuclides of the natural series and contributes to radionuclides transitions to others areas. The distribution of natural radioactive elements 226 Ra, 232 Th, and 40 K in rock and soil is not uniform and as a consequence all building materials contain amounts of natural radioactive substances. This study aimed to establish the calculation of the Equivalent Radium Activity (Ra Eq ) in brickwork's clays in the adjacent area to the uranium deposits in Northeast Brazil cities in the states of Paraiba and Rio Grande do Norte. The analyses were performed using the non-destructive method HPGe-Be gamma spectrometry. Twenty-eight samples were collected from ten brickworks in the cities of Sao Jose do Sabugi and Santa Luzia, in Paraiba State and Santana do Serido and Parelhas, in Rio Grande do Norte State. The activities of RaEq ranged from 84.5 to 747.8 Bq/kg with an average of 334.0 Bq/kg. Approximately 29% of the analyzed samples had activities of RaEq above the limit defined by UNSCEAR (the limit is 370 Bq/kg), where the clays must have its sources of extraction monitored, respecting the radioecological protection rules. From the qualification of the samples, it has been certified that the radionuclides present in this study are exclusively of natural origin. (author)

  8. Radium equivalent in clays extracted in Northeast cities of Brazil and used in civil construction

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, Eduardo E.N.; Junior, Jose Araujo S.; Amaral, Romilton S.; Santos, Josineide M.N.; Rojas, Lino A.V.; Fernandez, Zahily H., E-mail: eduardo.eudes@ufpe.br, E-mail: jaraujo@ufpe.br, E-mail: romilton@ufpe.br, E-mail: josineide.santos@ufpe.br, E-mail: lino.valcarcel@ufpe.br, E-mail: zahily1985@gmail.com [Universidade Federal de Pernambuco (DEN/UFPE), Recife, PE (Brazil). Departamento de Energia Nuclear

    2017-11-01

    The Earth's crust may have different levels of natural radioactivity as a consequence of the different types of minerals that form its composition. Exploration activities of natural sources may have a high radiometric impact for the radionuclides of the natural series and contributes to radionuclides transitions to others areas. The distribution of natural radioactive elements {sup 226}Ra, {sup 232}Th, and {sup 40}K in rock and soil is not uniform and as a consequence all building materials contain amounts of natural radioactive substances. This study aimed to establish the calculation of the Equivalent Radium Activity (Ra{sub Eq}) in brickwork's clays in the adjacent area to the uranium deposits in Northeast Brazil cities in the states of Paraiba and Rio Grande do Norte. The analyses were performed using the non-destructive method HPGe-Be gamma spectrometry. Twenty-eight samples were collected from ten brickworks in the cities of Sao Jose do Sabugi and Santa Luzia, in Paraiba State and Santana do Serido and Parelhas, in Rio Grande do Norte State. The activities of RaEq ranged from 84.5 to 747.8 Bq/kg with an average of 334.0 Bq/kg. Approximately 29% of the analyzed samples had activities of RaEq above the limit defined by UNSCEAR (the limit is 370 Bq/kg), where the clays must have its sources of extraction monitored, respecting the radioecological protection rules. From the qualification of the samples, it has been certified that the radionuclides present in this study are exclusively of natural origin. (author)

  9. Ball clay

    Science.gov (United States)

    Virta, R.L.

    2001-01-01

    Part of the 2000 annual review of the industrial minerals sector. A general overview of the ball clay industry is provided. In 2000, sales of ball clay reached record levels, with sanitary ware and tile applications accounting for the largest sales. Ball clay production, consumption, prices, foreign trade, and industry news are summarized. The outlook for the ball clay industry is also outlined.

  10. Influence of clay mineralogy on clay based ceramic products

    International Nuclear Information System (INIS)

    Radzali Othman; Tuan Besar Tuan Sarif; Zainal Arifin Ahmad; Ahmad Fauzi Mohd Noor; Abu Bakar Aramjat

    1996-01-01

    Clay-based ceramic products can either be produced directly from a suitable clay source without the need further addition or such products can be produced from a ceramic body formulated by additions of other raw materials such as feldspar and silica sand. In either case, the mineralogical make-up of the clay component plays a dominating role in the fabrication and properties of the ceramic product. This study was sparked off by a peculiar result observed in one of five local ball clay samples that were used to reformulate a ceramic body. Initial characterisation tests conducted on the clays indicated that these clays can be classified as kaolinitic. However, one of these clays produced a ceramic body that is distinctively different in terms of whiteness, smoothness and density as compared to the other four clays. Careful re-examination of other characterisation data, such as particle size distribution and chemical analysis, failed to offer any plausible explanation. Consequently, the mineralogical analysis by x-ray diffraction was repeated by paying meticulous attention to specimen preparation. Diffraction data for the clay with anomalous behaviour indicated the presence of a ∼ 10A peak that diminished when the same specimen was re-tested after heating in an oven at 12O degree C whilst the other four clays only exhibit the characteristic kaolinite (Al sub 2 O sub 3. 2SiO sub 2. 2H sub 2 0) and muscovite peaks at ∼ 7A and ∼ 10A before and after heat treatment. This suggests the presence of the mineral halloysite (A1 sub 2 0 sub 3. 2SiO sub 2.4H sub 2 0) in that particular clay. This difference in mineralogy can be attributed to account for the variations in physical properties of the final product. Consequently, this paper reviews in general the precautionary measures that must be adhered to during any mineralogical investigation of clay minerals or clay-based materials. The common pitfalls during specimen preparation, machine settings and interpretation of

  11. Humic substances in natural waters and their complexation with trace metals and radionuclides: a review

    International Nuclear Information System (INIS)

    Boggs, S. Jr.; Livermore, D.; Seitz, M.G.

    1985-07-01

    Dissolved humic substances (humic and fulvic acids) occur in surface waters and groundwaters in concentrations ranging from less than 1 mg(C)/L to more than 100 mg(C)/L. Humic substances are strong complexing agents for many trace metals in the environment and are also capable of forming stable soluble complexes or chelates with radionuclides. Concentrations of humic materials as low as 1 mg(C)/L can produce a detectable increase in the mobility of some actinide elements by forming soluble complexes that inhibit sorption of the radionuclides onto rock materials. The stability of trace metal- or radionuclide-organic complexes is commonly measured by an empirically determined conditional stability constant (K'), which is based on the ratio of complexed metal (radionuclide) in solution to the product concentration of uncomplexed metal and humic complexant. Larger values of stability constants indicate greater complex stability. The stability of radionuclide-organic complexes is affected both by concentration variables and envionmental factors. In general, complexing is favored by increased of radionuclide, increased pH, and decreased ionic strength. Actinide elements are generally most soluble in their higher oxidation states. Radionuclides can also form stable, insoluble complexes with humic materials that tend to reduce radionuclide mobility. These insoluble complexes may be radionuclide-humate colloids that subsequently precipitate from solution, or complexes of radionuclides and humic substances that sorb to clay minerals or other soil particulates strongly enough to immobilize the radionuclides. Colloid formation appears to be favored by increased radionuclide concentration and lowered pH; however, the conditions that favor formation of insoluble complexes that sorb to particulates are still poorly understood. 129 refs., 25 figs., 19 tabs

  12. Radionuclides in milk of dairy heifers raised on forages harvested from phosphatic clay soils on reclaimed mined land

    International Nuclear Information System (INIS)

    Staples, C.R.; Umana, R.; Hayen, M.J.

    1994-01-01

    Alfalfa (AR; Medicago sativa L.) and corn (CSR; Zea mays L.) were grown in phosphatic clay soils on phosphate-mined reclaimed land in central Florida. Corn (CSC) also was grown on unmined land and served as a control forage. Upon harvesting, plants were chopped and ensiled. Concentrations of 226 Ra averaged 2.44, 0.26 and 0.15; 210 Pb averaged 1.04, 0.63, and 0.52; and 210 Po averaged 1.59, 0.59, and 1.26 Bq kg -1 DM for AR, CSR, and CSC, respectively. These forages were fed separately to Holstein dairy replacement heifers (Bos taurus) (n=15 per forage) from approximately 9 to 25 mo of age. Heifers gave birth to calves at approximately 24 mo of age. Samples of milk were collected on d 1, 15, and 30 of lactation and analyzed for radionuclides. Averaged across sampling days, heifers fed AR had greater milk concentrations of 226 Ra compared with those fed CSR (0.27 vs. 0.22 Bq kg -1 DM; P -1 DM; P 210 Po compared with heifers fed CSR (0.58 vs. 0.30 Bq kg -1 DM; P -1 DM). Lead-210 was greater in milk from heifers fed CSR compared with those fed AR or CSC (1.38 vs. 0.94 and 0.92 Bq kg -1 DM; P < 0.13), respectively. Plasma S and Cu concentrations suggested subclinical molybdenosis in heifers fed AR. However, all heifers grew at an acceptable rate, conceived normally, had normal gestation periods, gave high quality colostrum at calving, and produced similar amounts of milk. 17 refs., 9 tabs

  13. Characterization of Heat-treated Clay Minerals in the Context of Nuclear Waste Disposal

    Science.gov (United States)

    Matteo, E. N.; Wang, Y.; Kruichak, J. N.; Mills, M. M.

    2015-12-01

    Clay minerals are likely candidates to aid in nuclear waste isolation due to their low permeability, favorable swelling properties, and high cation sorption capacities. Establishing the thermal limit for clay minerals in a nuclear waste repository is a potentially important component of repository design, as flexibility of the heat load within the repository can have a major impact on the selection of repository design. For example, the thermal limit plays a critical role in the time that waste packages would need to cool before being transferred to the repository. Understanding the chemical and physical changes, if any, that occur in clay minerals at various temperatures above the current thermal limit (of 100 °C) can enable decision-makers with information critical to evaluating the potential trade-offs of increasing the thermal limit within the repository. Most critical is gaining understanding of how varying thermal conditions in the repository will impact radionuclide sorption and transport in clay materials either as engineered barriers or as disposal media. A variety of repository-relevant clay minerals (illite, mixed layer illite/smectite, and montmorillonite), were heated for a range of temperatures between 100-1000 °C. These samples were characterized to determine surface area, mineralogical alteration, and cation exchange capacity (CEC). Our results show that for conditions up to 500 °C, no significant change occurs, so long as the clay mineral remains mineralogically intact. At temperatures above 500 °C, transformation of the layered silicates into silica phases leads to alteration that impacts important clay characteristics. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's Nation Nuclear Security Administration under contract DE-AC04-94AL85000. SAND Number: SAND2015-6524 A

  14. Influence of natural mobile organic matter on europium retention on Bure clay rock

    International Nuclear Information System (INIS)

    Vu-Do, Laurence

    2013-01-01

    Bure clay rock (CR) was chosen as host rock for the French high and intermediate level long lived radioactive waste repository. This choice is mostly explained by the retention ability of the Callovo-Oxfordian rock (COx). Bure clay rock contains natural organic matter (OM) that could have an influence on radionuclide retention. The aim of this work is to assess the influence of natural mobile OM on the retention of Eu on clay rock. Eu was chosen as a chemical model for trivalent actinides contained in vitrified waste. Three organic molecules were studied: suberic, sorbic and tiglic acids, small organic acids identified in COx pore water. All the experiments were carried out in an environment recreating COx water (pH=7.5; I=0.1 mol/L; PCO 2 =10 -2 bar).Clay rock sample characterization showed that the sample used in this work was similar to those previously extracted from the area of interest and that it was necessary to maintain pH at 7.5 to avoid altering the clay rock. The Eu-OM system study indicated that organic acids had no influence on Eu speciation in COx water. The Eu-CR system experimental study confirmed that retention implied sorption on CR (C(Eu)≤6.10 -6 mol/L) and precipitation in COx water (C(Eu)≥6.10 -6 mol/L). Distribution coefficient Rd (quantifying sorption) was estimated at 170 ± 30 L/g. This high value is consistent with literature values obtained on clay rocks. The ternary Eu-OM-CR system study showed a slight increase of sorption in the presence of organic matter. This synergistic effect is very satisfactory in terms of storage security: the presence of small organic acids in clay rock does not question retention properties with respect to europium and trivalent actinides. (author)

  15. In situ study of radionuclide diffusion into clays with specific device: Autolab probe

    International Nuclear Information System (INIS)

    Porcheron, J.

    1993-01-01

    The aim of this shared cost contract between the French Atomic Energy Commissariat, Nuclear Safety and Protection Institute and the Commission of the European Communities was to build and use an experimental drilling probe, the AUTOLAB prob, which was designed to measure the diffusion into clay of radioactive pollutants originating from a high activity waste storage. The measurement was carried out in-situ during drilling. The probe is equipped a new operating mode which involves using the pressure of the drilling water as its source of energy. The probe is autonomous and can stay in the bore hole for an extensive period of time without requiring any monitoring and without introducing any pollution. The diffusion experiment was carried out in a bore-hole at the JRC in ISPRA (ITALY). Two diffusion experiments were carried out in identical conditions (clay, 85Sr tracer, water samples), one in Laboratory, (ISPRA JRC Radiochemistry Laboratory, ITALY), and the other in-situ. The results displayed that 85Sr diffusion was considerably faster in the in-situ experiment than in that conducted in Laboratory. The explanation for this phenomenon, which could be due to the balance of carbonates, has not yet been clearly established. This test shows the value of comparing laboratory tests with in-situ tests conducted accurately using well adapted equipment. 9 refs., 10 figs

  16. Sealing performance of fractured claystone and clay-based materials. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Chun-Liang

    2017-03-15

    The geological disposal concepts for radioactive waste are generally based on a multibarrier system comprising the natural geological formations and engineered barriers. After waste emplacement, disposal cells, access drifts and shafts will be backfilled and sealed with suitable materials to prevent release of radionuclides into the biosphere. In the framework of the THM-TON project during the last ten years from 2007 to 2016, which was funded by the German Federal Ministry for Economic Affairs and Energy (BMWi) under contract number 02E10377, GRS investigated the thermo-hydro-mechanical properties and responses of clay rocks and clay-based backfill/seal materials. The results obtained during the first time period of 2007 to 2013 are summarized in the GRS report ''Thermo-Hydro-Mechanical Processes in the Nearfield around a HLW Repository in Argillaceous Formations'' with two volumes: Volume I - Laboratory Investigations (GRS-312) /ZHA 13a/ and Volume II - In-situ-Investigations and Interpretative Modelling (GRS-313) /ZHA 14a/.

  17. CHEMLAB. A probe for in-situ radionuclide experiments. Diffusion studies

    International Nuclear Information System (INIS)

    Jansson, Mats; Eriksen, Trygve E.

    2001-06-01

    CHEMLAB is a borehole laboratory built into a probe, in which in situ experiments can be carried out under ambient conditions with respect to pressure and temperature with the use of natural groundwater from the surrounding rock. The first CHEMLAB experiments, diffusion of cations and anions in compacted bentonite clay, have been carried out in borehole KA2512A at a depth of 320 m in Aespoe Hard Rock Laboratory. Diffusant solutions of Co 2+ , Sr 2+ , Cs + , I - and TcO 4- with 57 Co, 85 Sr, 134 Cs, 131 I and 99 Tc as tracers were used. measured profiles for the radionuclides in the bentonite are in good agreement with profiles predicted from modelling based on apparent diffusivities and sorption coefficients obtained in laboratory experiments with clay compacted to corresponding dry density and synthetic ground water with the same composition as in borehole KA2512A

  18. Sedimentation Deposition Patterns on the Chukchi Shelf Using Radionuclide Inventories

    Science.gov (United States)

    Cooper, L. W.; Grebmeier, J. M.

    2016-02-01

    Sediment core collections and assays of the anthropogenic and natural radioisotopes, 137Cs and 210Pb, respectively, are providing long-term indications of sedimentation and current flow processes on the Chukchi and East Siberian sea continental shelf. This work, which has been integrated into interdisciplinary studies of the Chukchi Sea supported by both the US Bureau of Ocean Energy Management (COMIDA Hanna Shoal Project) and the National Oceanic and Atmospheric Administration (Russian-US Long Term Census of the Arctic, RUSALCA) includes studies of total radiocesium inventories, sedimentation rate determinations, where practical, and depths of maxima in radionuclide deposition. Shallow maxima in the activities of the anthropogenic radionuclide in sediment cores reflect areas with higher current flow (Barrow Canyon and Herald Canyon; 3-6 cm) or low sedimentation (Hanna Shoal; 1-3 cm). The first sedimentation studies from Long Strait are consistent with quiescent current conditions and steady recent sedimentation of clay particles. Elsewhere, higher and more deeply buried radionuclide inventories (> 2 mBq cm-2 at 15-17 cm depth) in the sediments correspond to areas of high particle deposition north of Bering Strait where bioturbation in productive sediments is also clearly an important influence. Radiocesium activities from bomb fallout dating to 1964 are now present at low levels (20 cm. Independent sedimentation rate measurements with the natural radionuclide 210Pb are largely consistent with the radiocesium measurements.

  19. Establishment of characterizing parameters of clay as a filling material and coverage for repository

    International Nuclear Information System (INIS)

    Santos, Daisy M.M. dos; Tello, Cledola Cassia Oliveira de

    2015-01-01

    The multiple barriers of a repository should be able to provide adequate containment of radionuclides during all the previewed time for the operation and institutional control. One of these barriers is the backfill layer, located between the waste packages and other barriers. Furthermore, after shutting the disposal units with concrete, various materials are used to compose the final coverage of the deposition area. The backfill and the cover layer can be composed of clay or clay mixed with cement, with soil or with rocks. The last layer is a vegetation cover. The selection of the best clay should take into consideration some physical-chemical and mechanical properties. Bentonite is a clay with high absorption capacity, and large volume change in moistening and drying processes, being also effective in the contaminant retention. Additionally, it presents unique properties, such as high swelling potential. Some bentonite characterization works have been developed in the Laboratory of Cementation at CDTN/CNEN (LABCIM/CDTN). The sequence of experiments was: granulometric analysis, moisture, compaction test, hydraulic conductivity and cation exchange capacity. Some initial characterization results are presented and discussed. The paper summarizes these previous studies in order to have the basis for creating a protocol for characterization of a bentonite as a reference material. (author)

  20. Establishment of characterizing parameters of clay as a filling material and coverage for repository

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Daisy M.M. dos; Tello, Cledola Cassia Oliveira de, E-mail: dmms@cdtn.br, E-mail: tellocc@cdtn.br [Centro de Desenvolvimento da Tecnologia Nucelar (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2015-07-01

    The multiple barriers of a repository should be able to provide adequate containment of radionuclides during all the previewed time for the operation and institutional control. One of these barriers is the backfill layer, located between the waste packages and other barriers. Furthermore, after shutting the disposal units with concrete, various materials are used to compose the final coverage of the deposition area. The backfill and the cover layer can be composed of clay or clay mixed with cement, with soil or with rocks. The last layer is a vegetation cover. The selection of the best clay should take into consideration some physical-chemical and mechanical properties. Bentonite is a clay with high absorption capacity, and large volume change in moistening and drying processes, being also effective in the contaminant retention. Additionally, it presents unique properties, such as high swelling potential. Some bentonite characterization works have been developed in the Laboratory of Cementation at CDTN/CNEN (LABCIM/CDTN). The sequence of experiments was: granulometric analysis, moisture, compaction test, hydraulic conductivity and cation exchange capacity. Some initial characterization results are presented and discussed. The paper summarizes these previous studies in order to have the basis for creating a protocol for characterization of a bentonite as a reference material. (author)

  1. 222Rn and CO2 soil-gas geochemical characterization of thermally altered clays at Orciatico (Tuscany, Central Italy)

    International Nuclear Information System (INIS)

    Voltattorni, N.; Lombardi, S.; Rizzo, S.

    2010-01-01

    Research highlights: → Soil-gas technique is applied to study gas permeability of Orciatico clay units. → Clay permeability depends on thermal and mechanical alteration degree. → Soil-gas distributions are due to shallow fracturing of clays. → Rn and CO 2 soil-gas anomalies highlight secondary permeability in clay sequence. → Soil-gas results are supported by detailed geoelectrical surveys. - Abstract: The physical properties of clay allow argillaceous formations to be considered geological barriers to radionuclide migration in high-level radioactive-waste isolation systems. As laboratory simulations are short term and numerical models always involve assumptions and simplifications of the natural system, natural analogues are extremely attractive surrogates for the study of long-term isolation. The clays of the Orciatico area (Tuscany, Central Italy), which were thermally altered via the intrusion of an alkali-trachyte laccolith, represent an interesting natural model of a heat source which acted on argillaceous materials. The study of this natural analogue was performed through detailed geoelectrical and soil-gas surveys to define both the geometry of the intrusive body and the gas permeability of a clay unit characterized by different degrees of thermal alteration. The results of this study show that gas permeability is increased in the clay sequences subjected to greater heat input from the emplacement of the Orciatico intrusion, despite the lack of apparent mineral and geotechnical variations. These results, which take into consideration long time periods in a natural, large-scale geological system, may have important implications for the long-term safety of underground storage of nuclear waste in clay formations.

  2. Investigations on self-sealing of indurated clay - Part of the NF-PRO project. Final report

    International Nuclear Information System (INIS)

    Zhang, Chun-Liang; Rothfuchs, T.; Dittrich, J.; Mueller, J.

    2008-03-01

    The self-sealing potential of the Callovo-Oxfordian argillite and the Opalinus clay was investigated on strongly damaged samples. Gas permeability as a function of the confining stress before and after water resaturation was measured. Not only normally-sized but also large-scale and cylindrical ring-shaped samples were tested. Each test lasted over a time period of 5 to 16 months. The experimental findings are: 1. The permeability of the pre-damaged samples decreased significantly with a concurrent increase of the confining stress due to fracture closure. The permeability measured in radial direction on a hollow sample decreased from 10 -15 m 2 at a low confining stress of 1 MPa to 10 -21 m 2 at 28 MPa. The compression of the sample led to plastic closure of pre-existing fractures, leading to a significantly lower permeability after unloading. A similar permeability reduction with increasing confining stress was also observed in axial direction, parallel to the bedding plane. But, at low confining stresses below 10 MPa, the axial permeability parallel to the bedding was about one to two orders of magnitude higher than the radial one perpendicular to the bedding. The hydraulic anisotropy vanishes off with increasing the confining stress. 2. The permeability of fractured clay rocks was dominated by the confining stress normal to the fracture plane. This was validated by gas permeability measurements on a large sample (D=260 mm/L=616 mm) with fractures oriented parallel to the sample axis. The increase of the lateral stress from 3 to 18 MPa at 19 MPa axial stress led to a decrease of axial permeability from 10 -13 to 10 -19 m 2 . 3. The permeability od damaged clay rocks decreased also with time due to the time-dependent compaction of pores and fractures. On the pre-damaged samples, a permeability reduction by a factor of 4 to 8 was observed over two months at a low confining stress of 1.5 MPa. 4. The high swelling potential of the studied clay rocks led to the

  3. Microstructural interactions of geologic media with waste radionuclides

    International Nuclear Information System (INIS)

    Hinkebein, T.E.; Hlava, P.F.

    1977-01-01

    A preliminary investigation of the microstructure of four geologic media was undertaken to examine the interaction of Cs, Sr, Gd and U with those media. Since K/sub D/ measurements often vary by more than an order of magnitude on rocks of the same strata separated by several feet, it was probable that minor rock components play an important role in radionuclide sorption. A qualitative analysis of the rock surfaces after equilibration with solutions of Cs + , Sr ++ , Gd +++ and UO 2 ++ revealed that clay minerals are responsible for all important sorption that takes place on the rocks studied (Magenta dolomite, Bell Canyon silt stone, Eleana shale and clay bearing halite). Thus it is concluded that a relatively small portion of these rocks is actively responsible for sorption characteristics. Gd was bound on all samples, probably as Fe bearing chlorites. Cs was strongly held on the Eleana shale, probably by an illite. Although uranium was associated with an unidentified clay in the halite sample, uranium sorption probably occurred as UO 2 CO 3 , which would not significantly retard uranium movement at trace concentrations. Similarly Sr was retained only as SrSO 4 on Magenta and this mechanism is not significant at trace levels. These analyses were performed by correlating electron microprobe elemental distribution photomicrographs with x-ray analyses of the four rocks. 13 figs., 2 tables

  4. Predictive modelling of an excavation test in indurated clay

    International Nuclear Information System (INIS)

    Garitte, B.; Vaunat, J.; Gens, A.; Vietor, T.

    2010-01-01

    Document available in extended abstract form only. This Abstract presents the predictive hydro-mechanical (HM) modelling of an excavation performed in Opalinus clay in the Mont Terri underground laboratory. Niche 2 was excavated in the shaly facies of Opalinus clay from gallery 08. The area surrounding the gallery was intensively instrumented. The geology of Mont Terri is described in Thury and Bosssart (1999) and the parameters used in the analysis were taken from Bock (2009). The stress state is derived from Martin and Lanyion (2003). Gallery 08 is horseshoe shaped and has a mean radius of 2.25 m. It was excavated with a road header at a mean velocity of 1 m/day starting on January 30, 2008 (Gallery chainage 43.8) and ending on June 30, 2008 (Gallery chainage 123.8) with a stop from March 18, to April 24, to instrument the area of niche 2. Niche 2 was excavated by successive blastings 1.3 m deep until reaching a distance of 24 m from the gallery 08 wall. Advance was continuous from October 13, to November 7 with the exception of three stops of 3, 5 and 4 days. The niche has an average diameter of 4.5 m and has a slight upward slope of 0.98%. The excavation of gallery 08 from chainage 43.8 to chainage 123.8 and of the niche was simulated by relaxing the normal total stress and water pressure from the value before excavation to 0. The gallery advance rate was simulated in an approximate manner by applying successively the excavation procedure to 9 m long gallery sections. In the case of the niche, the blasting scheme and the application of the shotcrete was closely reproduced. The three dimensional geometry used in the simulation is shown. The coupled hydro-mechanical formulation used for the analysis is based on the simultaneous solution of the balance equation for solid mass, water mass and momentum (equilibrium). In accordance with field observations, it has been assumed that the medium remains saturated throughout. The formulation was completed with a number of

  5. M-S-H precipitation in low-pH concretes in clayey environment

    International Nuclear Information System (INIS)

    Dauzeres, A.; Achiedo, G.; Nied, D.; L'Hopital, E.; Alahrache, S.; Lothenbach, B.

    2015-01-01

    In the framework of the CI-project (Cement Clay Interaction Experiment), two different low-pH cements were emplaced at Mont Terri rock laboratory to study their interactions with the surrounding Opalinus Clay (OPA): ESDRED (shotcrete mixture: 60% of CEM-I 42.5 N + 40% of silica fume + aluminium sulphate salt as accelerator) and LAC composed of CEM-III/B 42.5 L (60% of blast furnace slag + 10% nano silica). After 5 years of interactions in the Mont Terri rock laboratory, SEM-EDS analyses show a systematic Mg-perturbation associated with a high decalcification near the surface of both cementitious materials. TGA (Thermogravimetric Analysis) and XRD (X-ray diffraction) investigations associate this Mg-enrichment to the possible formation of M-S-H. This result is confirmed by 29 Si NMR analyses, showing a high polymerisation degree of the Si-network in the Mg-enriched zone typical of a sheet-like structure. Tem/EDS investigations of a FIB section carried out in the Mg zone of both LAC and ESDRED concretes indicate that the Mg phase exhibits a gel-like structure similar to C-S-H gel. This experimentally observed Mg-enrichment in the interaction zone is well reproduced by reactive transport modelling of the LAC/Opalinus clay with the HYTEC code. (authors)

  6. Effect of temperature on damage and permeability of clayey soils and rocks

    International Nuclear Information System (INIS)

    Monfared, M.

    2011-04-01

    Storage of exothermic radioactive waste in deep low permeability geological formations such as clayey rocks and plastic clays is a solution considered for long term repositories. However the excavation of underground galleries creates a damaged zone (EDZ). The effect of the damage zone on the transport properties of the geological barrier has been widely studied. Within the framework of the TIMODAZ European project, emphasis has been put on the effect of temperature. As a partner of this project, the current work is performed to investigate the coupling effect between temperature, damage and permeability on Boom clay and Opalinus clay through an experimental study. View to the experimental difficulties related to the low permeability materials, a new hollow cylinder triaxial cell with short drainage path specifically designed to study the thermo-hydro-mechanical behaviour of very low permeable materials is developed during this work. The tests and the numerical analysis show that the short sample drainage path reduces significantly the time needed to re-saturate an initially unsaturated sample and it also permits to achieve drained conditions (i.e. negligible excess pore pressure during testing) with a higher loading rate. For Boom clay, the effect of the pore water thermal pressurisation on a sample with a pre-existing shear band is investigated. The undrained heating under shear stress decreases the effective stress on the sample which leads to its failure. An existing failure plane in the sample behaves like a preferential weakness plane which can be reactivated by pore water thermal pressurisation. The estimated shearing resistance along the sheared plane is smaller than that of the intact material. For the Opalinus clay-stone, drained heating on a saturated sample shows that this clay-stone behaves like a slightly over consolidated material (thermo-elasto-plastic behaviour) with transition from expansion to contraction at 65 C. The decrease of the permeability

  7. Molecular Basis of Clay Mineral Structure and Dynamics in Subsurface Engineering Applications

    Science.gov (United States)

    Cygan, R. T.

    2015-12-01

    Clay minerals and their interfaces play an essential role in many geochemical, environmental, and subsurface engineering applications. Adsorption, dissolution, precipitation, nucleation, and growth mechanisms, in particular, are controlled by the interplay of structure, thermodynamics, kinetics, and transport at clay mineral-water interfaces. Molecular details of these processes are typically beyond the sensitivity of experimental and analytical methods, and therefore require accurate models and simulations. Also, basal surfaces and interlayers of clay minerals provide constrained interfacial environments to facilitate the evaluation of these complex processes. We have developed and used classical molecular and quantum methods to examine the complex behavior of clay mineral-water interfaces and dynamics of interlayer species. Bulk structures, swelling behavior, diffusion, and adsorption processes are evaluated and compared to experimental and spectroscopic findings. Analysis of adsorption mechanisms of radionuclides on clay minerals provides a scientific basis for predicting the suitability of engineered barriers associated with nuclear waste repositories and the fate of contaminants in the environment. Similarly, the injection of supercritical carbon dioxide into geological reservoirs—to mitigate the impact of climate change—is evaluated by molecular models of multi-fluid interactions with clay minerals. Molecular dynamics simulations provide insights into the wettability of different fluids—water, electrolyte solutions, and supercritical carbon dioxide—on clay surfaces, and which ultimately affects capillary fluid flow and the integrity of shale caprocks. This work is supported as part of Center for Frontiers of Subsurface Energy Security, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science and by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Geosciences Research Program

  8. Molecular dynamics of interfacial water and cations associated with clay minerals

    International Nuclear Information System (INIS)

    Cygan, Randall T.; Greathouse, Jeffery A.; Teich-McGoldrick, Stephanie L.; Nenoff, Tina M.; Daemen, Luke L.

    2012-01-01

    Document available in extended abstract form only. Clay mineral interfaces, including interlayer and external surfaces, play an essential role in many geochemical processes. Adsorption, dissolution, precipitation, nucleation, and growth mechanisms, in particular, are controlled by the interplay of structure, thermodynamics, kinetics, and transport at clay mineral-water interfaces. Molecular details of these geochemical processes are especially important in evaluating the fate of radionuclide waste in the environment. Such details are typically beyond the sensitivity of experimental and analytical methods and therefore require accurate models and simulations. Also, the basal surfaces and interlayers of clay minerals offer structurally constrained interfacial environments to better evaluate the local molecular chemistry. We have developed and used classical and quantum methods to examine the complex behavior of clay mineral-water interfaces and dynamics of interlayer species. Bulk structures, swelling behavior, diffusion, and adsorption processes are evaluated and compared to experimental and spectroscopic findings. In particular, inelastic neutron scattering methods provide a successful probe of vibrational behavior of interlayer species to help guide the simulations. Librations involving rock, wag, and twist motions of water molecules are particularly sensitive to the interlayer environment of smectite minerals such as montmorillonite and beidellite. Trends in librational modes for interlayer water as a function of clay structure and cation hydration energy are readily explained using structural and vibrational analysis derived from molecular simulation. Molecular dynamics simulations of virtual phases, including hydrated pyrophyllite, help to explain the behavior of interlayer water that is not associated with cation species. Additionally, we use large-scale molecular dynamics simulations of other layered minerals, such as muscovite, to evaluate adsorption

  9. CHEMLAB. A probe for in-situ radionuclide experiments. Diffusion studies

    Energy Technology Data Exchange (ETDEWEB)

    Jansson, Mats; Eriksen, Trygve E. [Royal Inst. of Technology, Stockholm (Sweden). Dept. of Chemistry

    2001-06-01

    CHEMLAB is a borehole laboratory built into a probe, in which in situ experiments can be carried out under ambient conditions with respect to pressure and temperature with the use of natural groundwater from the surrounding rock. The first CHEMLAB experiments, diffusion of cations and anions in compacted bentonite clay, have been carried out in borehole KA2512A at a depth of 320 m in Aespoe Hard Rock Laboratory. Diffusant solutions of Co{sup 2+}, Sr{sup 2+}, Cs{sup +}, I{sup -} and TcO{sup 4-} with {sup 57}Co, {sup 85}Sr, {sup 134}Cs, {sup 131}I and {sup 99}Tc as tracers were used. measured profiles for the radionuclides in the bentonite are in good agreement with profiles predicted from modelling based on apparent diffusivities and sorption coefficients obtained in laboratory experiments with clay compacted to corresponding dry density and synthetic ground water with the same composition as in borehole KA2512A.

  10. Sorption of activation products on London clay and Dungeness aquifer gravel

    International Nuclear Information System (INIS)

    Baston, G.M.N.; Berry, J.A.; Littleboy, A.K.; Pilkington, N.J.

    1992-01-01

    The sortpion of a series of activation-product radionuclides onto London clay and Dungeness aquifer gravel from the nuclear reactor sites at Bradwell and Dungeness, has been examined. Batch sorption and through-diffusion experiments with clay determined chlorine as the chloride ion to be effectively non-sorbing; calcium to be weakly sorbing, whereas cobalt, nickel, niobium and samarium were moderately to strongly sorbing and silver was strongly sorbing. Distribution ratios (R D values) for Nb, Sm and Ag were found to have a strong dependence on the liquid-solid separation technique employed. The presence of high concentrations of calcium hydroxide led to lower values of R D for radioactive Ca but higher R D values for Sm and Ag. The sorption of Ni showed no apparent dependence on groundwater composition at low levels of dissolved organic carbon (DOC). The values of R D for Co decreased as the DOC content was increased by addition of humic materials. Batch sorption studies with aquifer gravel demonstrated that Ca is weakly sorbing whereas Nb, Ag and Eu are moderately to strongly sorbing. R D values for Ca and for Ag under neutral pH conditions show little sensitivity to the liquid/solid separation technique used. However, R D values for Nb and Eu under neutral pH conditions and for Ag in alkaline solution (pH = 11 - 12) show a marked effect. The aquifer gravel was found to be highly inhomogeneous unlike the clay and sorption was greatest on samples with a high proportion of sand, reflecting the clay mineral content. (orig.)

  11. Strategy for a consistent selection of radionuclide migration parameters for the Belgian safety and feasibility case-1

    International Nuclear Information System (INIS)

    Bruggeman, C.; Maes, N.; Salah, S.; Brassinnes, S.; Van Geet, M.

    2010-01-01

    Document available in extended abstract form only. The purpose of this presentation is to describe the strategy for the selection of retention and migration parameters for safety-relevant nuclides that was developed in the framework of the Belgian Safety and Feasibility Case SFC-1. A geochemical database containing state-of-the-art retention and migration parameters of all safety-relevant radionuclides, is ideally based on a thermodynamic understanding and an ability to accurately describe the geochemical and transport behaviour of all these radionuclides under the geochemical conditions that are considered for a reference host formation. In Belgium, this reference formation is Boom Clay. The parameters will be used in Performance Assessment (PA) calculations, and therefore must also be adapted to PA models. Since these models currently use only a four parameters for every radionuclide, the whole geochemical and transport behaviour must be comprised to a very limited parameter set that describe on the one hand chemical retention within the Boom Clay formation, and on the other hand transport through the Boom Clay formation. Chemical retention considers two concepts: 1) a concentration limit (S), which represents the mobile concentration of a nuclide present in the aqueous phase under undisturbed far field Boom Clay conditions; 2) a retardation (R/Kd) factor, which represents the uptake of a mobile nuclide by the inorganic and organic phases present in the Boom Clay formation. For mobility/migration two additional concepts are introduced: 3) the diffusion accessible porosity (η), which is the total physical space available for transport of a nuclide. The maximum value of η is limited by the water content of the formation; 4) the pore diffusion coefficient (Dp), which represents the transport velocity of a nuclide in a diffusion-dominated system. Within the framework of SFC-1, primary focus is laid on the compilation of parameter ranges, instead of individual &apos

  12. Diffusion of radionuclides in concrete/bentonite systems

    International Nuclear Information System (INIS)

    Albinsson, Y.; Boerjesson, S.; Andersson, K.; Allard, B.

    1993-02-01

    In a repository for nuclear waste, different construction materials will be used. Two important materials among these are concrete and bentonite clay. These will act as mechanical barriers, preventing convective water flow and also retard transport due to diffusion of dissolved radionuclides by a combination of mechanical constraints and chemical interactions with the solid. An important issue is the possible change of the initial sodium bentonite into the calcium form due to ion exchange with calcium from the cement. The initial leaching of the concrete has been studied using radioactive spiked concrete in contact with compacted bentonite. The diffusion of Cs, Am and Pu into 5 different types of concrete in contact with porewater have been measured. The measured diffusivity for Cs agrees reasonable well with data found in literature. For Am and Pu no movement could be measured (less than 0.2 mm) even though the contact times were extremely long (2.5 y and 5 y, respectively). This report gives also a summary of the previously published results about sorption and diffusion of radionuclides in cement performed in Prav/KBS/SKB projects 1980-1990. 25 refs

  13. Investigation of radionuclide distribution in soil particles in different landscapes

    Science.gov (United States)

    Shkinev, V. M.; Korobova, E. M.; Linnik, V. G.

    2012-04-01

    Russian and foreign publications have been analyzed for understanding the role of micro- and nano- particles in distribution and migration of technogenic elements in soils in different landscape conditions. A technique for application of various fractionation methods to separate and study -particles of different size down to micro- and nano-level has been developed. The dry sit method on the first stage of particle separation is recommend to be followed by the membrane filtration method. For obtaining more comprehensive information, combinations of fractionation technique should be chosen taking into account that (1) the efficiency of particles' separation using subsequent technique would be higher than using the preceding one; (2) separation methods should preferably be based on different principles (separation according size, density, charge etc.); (3) initial fractionation should separate particles according to their size, that makes possible to create an even scale for various samples. A study of distribution and balance of technogenic radionuclides' in soil particles of the size intervals 1.0—0.25, 0.25-0.1, 0.1-0.05, 0.05-0.01, 0.01-0.005, 0.005-0.001 and soil layers. Contribution of the silt particles (0,05-0,01 mm) to Cs-137 contamination ranged from 26 to 33,8%, 45% maximum due to "optimal" combination of both factors. Clay fraction was responsible for approximately 30% of Cs-137 contained in soil horizons due to higher sorption capacity. Relatively high correlation between the activity of 152,154Eu and 60 and the content of silt and clay allowed suggesting their incorporation mainly in clay fraction. Selected experimental plots near the Kola NPP (northern taiga) were used to compare soil particles (fractions 140-71; 71-40 and radioactivity found in soil litter appeared to be related to the Chernobyl contamination. Concentration of s-137 was higher in small size fractions. Obtained results were considered to be useful for understanding of radionuclide

  14. Clay Houses

    Science.gov (United States)

    Pedro, Cathy

    2011-01-01

    In this article, the author describes a project designed for fourth-graders that involves making clay relief sculptures of houses. Knowing the clay houses will become a family heirloom makes this lesson even more worth the time. It takes three classes to plan and form the clay, and another two to underglaze and glaze the final products.

  15. Humic substances in natural waters and their complexation with trace metals and radionuclides: a review. [129 references

    Energy Technology Data Exchange (ETDEWEB)

    Boggs, S. Jr.; Livermore, D.; Seitz, M.G.

    1985-07-01

    Dissolved humic substances (humic and fulvic acids) occur in surface waters and groundwaters in concentrations ranging from less than 1 mg(C)/L to more than 100 mg(C)/L. Humic substances are strong complexing agents for many trace metals in the environment and are also capable of forming stable soluble complexes or chelates with radionuclides. Concentrations of humic materials as low as 1 mg(C)/L can produce a detectable increase in the mobility of some actinide elements by forming soluble complexes that inhibit sorption of the radionuclides onto rock materials. The stability of trace metal- or radionuclide-organic complexes is commonly measured by an empirically determined conditional stability constant (K'), which is based on the ratio of complexed metal (radionuclide) in solution to the product concentration of uncomplexed metal and humic complexant. Larger values of stability constants indicate greater complex stability. The stability of radionuclide-organic complexes is affected both by concentration variables and envionmental factors. In general, complexing is favored by increased of radionuclide, increased pH, and decreased ionic strength. Actinide elements are generally most soluble in their higher oxidation states. Radionuclides can also form stable, insoluble complexes with humic materials that tend to reduce radionuclide mobility. These insoluble complexes may be radionuclide-humate colloids that subsequently precipitate from solution, or complexes of radionuclides and humic substances that sorb to clay minerals or other soil particulates strongly enough to immobilize the radionuclides. Colloid formation appears to be favored by increased radionuclide concentration and lowered pH; however, the conditions that favor formation of insoluble complexes that sorb to particulates are still poorly understood. 129 refs., 25 figs., 19 tabs.

  16. The impacts of pore-scale physical and chemical heterogeneities on the transport of radionuclide-carrying colloids

    Energy Technology Data Exchange (ETDEWEB)

    WU, Ning

    2018-04-24

    Independent of the methods of nuclear waste disposal, the degradation of packaging materials could lead to mobilization and transport of radionuclides into the geosphere. This process can be significantly accelerated due to the association of radionuclides with the backfill materials or mobile colloids in groundwater. The transport of these colloids is complicated by the inherent coupling of physical and chemical heterogeneities (e.g., pore space geometry, grain size, charge heterogeneity, and surface hydrophobicity) in natural porous media that can exist on the length scale of a few grains. In addition, natural colloids themselves are often heterogeneous in their surface properties (e.g., clay platelets possess opposite charges on the surface and along the rim). Both physical and chemical heterogeneities influence the transport and retention of radionuclides under various groundwater conditions. However, the precise mechanisms how these coupled heterogeneities influence colloidal transport are largely elusive. This knowledge gap is a major source of uncertainty in developing accurate models to represent the transport process and to predict distribution of radionuclides in the geosphere.

  17. Cicatrization of the damaged zone around a tunnel in low permeable rocks; Cicatrisation de la zone endommagee autour du tunnel dans des roches peu permeables

    Energy Technology Data Exchange (ETDEWEB)

    Hamza, R.O

    2005-12-15

    Three types of clays have been studied in this work: the Mol clay (plastic clay), the Mont Terri clay (opalinus clay) and the East clay (stiff clay). This work is divided into three parts: an experimental part which has allowed to identify the cicatrization phenomenon and the cracks closing. Through several tests has been determined the evolution of the permeability of the clayey samples which are undamaged or damaged with time and according to the different applied hydro-mechanical loadings. In order to describe the cicatrization phenomenon, a rheological law has been developed from the experimental observations and under some hypotheses. The parameters of the cicatrization model have been determined by numerical simulation. In order to take into account the structures effects at a large scale, the modelling of a tunnel has allowed to better identify the cicatrization phenomenon and to analyze the long term stability of this work. (O.M.)

  18. Cicatrization of the damaged zone around a tunnel in low permeable rocks

    International Nuclear Information System (INIS)

    Hamza, R.O.

    2005-12-01

    Three types of clays have been studied in this work: the Mol clay (plastic clay), the Mont Terri clay (opalinus clay) and the East clay (stiff clay). This work is divided into three parts: an experimental part which has allowed to identify the cicatrization phenomenon and the cracks closing. Through several tests has been determined the evolution of the permeability of the clayey samples which are undamaged or damaged with time and according to the different applied hydro-mechanical loadings. In order to describe the cicatrization phenomenon, a rheological law has been developed from the experimental observations and under some hypotheses. The parameters of the cicatrization model have been determined by numerical simulation. In order to take into account the structures effects at a large scale, the modelling of a tunnel has allowed to better identify the cicatrization phenomenon and to analyze the long term stability of this work. (O.M.)

  19. Geochemical study of evaporite and clay mineral-oxyhydroxide samples from the Waste Isolation Pilot Plant site

    International Nuclear Information System (INIS)

    Brookins, D.G.

    1993-06-01

    Samples of clay minerals, insoluble oxyhydroxides, and their host evaporites from the WIPP site have been studied for their major and minor elements abundances, x-ray diffraction characteristics, K-Ar ages, and Rb-Sr ages. This study was undertaken to determine their overall geochemical characteristics and to investigate possible interactions between evaporates and insoluble constituents. The evaporite host material is water-soluble, having Cl/Br ratios typical of marine evaporites, although the Br content is low. Insoluble material (usually a mixture of clay minerals and oxyhydroxide phases) yields very high Cl/Br ratios, possibly because of Cl from admixed halide minerals. This same material yields K/Rb and Th/U ratios in the normal range for shales; suggesting little, if any, effect of evaporite-induced remobilization of U, K, or Rb in the insoluble material. The rare-earth element (REE) data also show normal REE/chondrite (REE/CHON) distribution patterns, supporting the K/Rb and Th/U data. Clay minerals yield K-Ar dates in the range 365 to 390 Ma and a Rb-Sr isochron age of 428 ± 7 Ma. These ages are well in excess of the 220- to 230-Ma formational age of the evaporites, and confirm the detrital origin of the clays. The ages also show that any evaporite or clay mineral reactions that might have occurred at or near the time of sedimentation and diagenesis were not sufficient to reset the K-Ar and Rb-Sr systematics of the clay minerals. Further, x-ray data indicate a normal evaporitic assemblage of clay minerals and Fe-rich oxyhydroxide phases. The clay minerals and other insoluble material appear to be resistant to the destructive effects of their entrapment in the evaporites, which suggests that these insoluble materials would be good getters for any radionuclides (hypothetically) released from the storage of radioactive wastes in the area

  20. The systems containing clays and clay minerals from modified drug release: a review.

    Science.gov (United States)

    Rodrigues, Luís Alberto de Sousa; Figueiras, Ana; Veiga, Francisco; de Freitas, Rivelilson Mendes; Nunes, Lívio César Cunha; da Silva Filho, Edson Cavalcanti; da Silva Leite, Cleide Maria

    2013-03-01

    Clays are materials commonly used in the pharmaceutical industry, either as ingredients or as active ingredients. It was observed that when they are administered concurrently, they may interact with drugs reducing their absorption. Therefore, such interactions can be used to achieve technological and biopharmaceutical advantages, regarding the control of release. This review summarizes bibliographic (articles) and technological (patents) information on the use of systems containing clays and clay minerals in modified drug delivery. In this area, formulations such natural clay, commercial clay, synthetic clay, composites clay-polymers, nanocomposites clay-polymers, films and hidrogels composites clay-polymers are used to slow/extend or vectorize the release of drugs and consequently they increase their bioavailability. Finally, this review summarizes the fields of technology and biopharmaceutical applications, where clays are applied. Copyright © 2012 Elsevier B.V. All rights reserved.

  1. Status of radionuclide sorption-desorption studies performed by the WRIT program

    International Nuclear Information System (INIS)

    Serne, R.J.; Relyea, J.F.

    1981-01-01

    This paper focuses on interactions between dissolved radionuclides in groundwater and rocks and sediments away from the nearfield repository. Two approaches were used to study the primary mechanism, adsorption-desorption. Empirical studies rely on distribution coefficient measurements, and mechanism studies strive to identify, differentiate, and quantify the processes that control nuclide retardation. The status of sorption mechanism studies is discussed, with emphasis on delineating the usefulness of ideal ion-exchange, site-binding electrical double-layer, and redox-controlled sorption constructs. Since studies to date show greater potential for site-binding electrical double-layer models, future efforts will concentrate on this construct. Laboratory studies are discussed which corroborate the importance of redox reactions in causing nuclide retardation for multivalent elements, such as Tc, Np, Pu, and U. Results suggest that both solution-mediated reduction, such as the Fe(II)-Fe(III) couple, and solid-solution heterogeneous reduction reactions, such as reduction of solution Pu(VI) at the mineral surface by structural Fe(II), occur. Coupled microscopy, microprobe, and autoradiography studies have determined actual sorption sites for radionuclides on polymineralic rocks. The studies show that it is possible for minor phases to completely dominate the mass of radionuclides adsorbed. The most active minerals are typically alternation products (clays and zeolites). Several exercises are discussed which rank radionuclides according to their potential dose hazards. In each of the analyses discussed, the top four radionuclides are I, Tc, Np, and Ra. Other elements that rank high in potential hazards are Pu, U, Am, Th, Pb, Sn, Pd, and Se

  2. {sup 222}Rn and CO{sub 2} soil-gas geochemical characterization of thermally altered clays at Orciatico (Tuscany, Central Italy)

    Energy Technology Data Exchange (ETDEWEB)

    Voltattorni, N., E-mail: nunzia.voltattorni@ingv.it [Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, 00143 Rome (Italy); Lombardi, S. [Earth Science Department, University ' La Sapienza' , Piazzale A. Moro 5, 00185 Rome (Italy); Rizzo, S. [Via Tito, 1/A, 00061 Anguillara Sabazia, Rome (Italy)

    2010-08-15

    Research highlights: {yields} Soil-gas technique is applied to study gas permeability of Orciatico clay units. {yields} Clay permeability depends on thermal and mechanical alteration degree. {yields} Soil-gas distributions are due to shallow fracturing of clays. {yields} Rn and CO{sub 2} soil-gas anomalies highlight secondary permeability in clay sequence. {yields} Soil-gas results are supported by detailed geoelectrical surveys. - Abstract: The physical properties of clay allow argillaceous formations to be considered geological barriers to radionuclide migration in high-level radioactive-waste isolation systems. As laboratory simulations are short term and numerical models always involve assumptions and simplifications of the natural system, natural analogues are extremely attractive surrogates for the study of long-term isolation. The clays of the Orciatico area (Tuscany, Central Italy), which were thermally altered via the intrusion of an alkali-trachyte laccolith, represent an interesting natural model of a heat source which acted on argillaceous materials. The study of this natural analogue was performed through detailed geoelectrical and soil-gas surveys to define both the geometry of the intrusive body and the gas permeability of a clay unit characterized by different degrees of thermal alteration. The results of this study show that gas permeability is increased in the clay sequences subjected to greater heat input from the emplacement of the Orciatico intrusion, despite the lack of apparent mineral and geotechnical variations. These results, which take into consideration long time periods in a natural, large-scale geological system, may have important implications for the long-term safety of underground storage of nuclear waste in clay formations.

  3. The role of colloids and suspended particles in radionuclide transport in the Canadian concept for nuclear fuel waste disposal

    International Nuclear Information System (INIS)

    Vilks, P.

    1994-02-01

    AECL Research is developing a concept for the permanent disposal of nuclear fuel waste in a deep engineered vault in plutonic rock of the Canadian Shield and is preparing an Environmental Impact Statement (EIS) to document its case for the acceptability of the disposal concept. This report, one in a series of supporting documents for the EIS, addresses the role of particles in radionuclide transport. It summarizes our studies of natural particles in groundwater and presents the arguments used to justify the omission of particle-facilitated transport in the geosphere model that is based on the Whiteshell Research Area (WRA) and used in the postclosure assessment study case. Because radiocolloids formed in the vault will not be able to migrate through the clay buffer, radiocolloid formation in the geosphere will be determined by the sorption of radionuclides onto particles in groundwater. These particles consist of typical fracture-lining minerals, such as clays, micas and quartz; precipitated particles, such as colloidal silica and Fe-Si oxyhydroxides; and organic particles. In groundwater from the WRA, the average concentrations of colloids and suspended particles are 0.34 and 1.4 mg/L respectively. Particle-facilitated transport is not included in the geosphere model because the concentrations of particles in groundwater from the WRA are too low to have a significant impact on radionuclide transport. (author). 92 refs., 11 tabs., 13 figs

  4. Time evolution of the Clay Barrier Chemistry in a HLW deep geological disposal in granite

    International Nuclear Information System (INIS)

    Font, I.; Miguel, M. J.; Juncosa, R.

    2000-01-01

    The main goal of a high level waste geological disposal is to guarantee the waste isolation from the biosphere, locking them away into very deep geological formations. The best way to assure the isolation is by means of a multiple barrier system. These barriers, in a serial disposition, should assure the confinement function of the disposal system. Two kinds of barriers are considered: natural barriers (geological formations) and engineered barriers (waste form, container and backfilling and sealing materials). Bentonite is selected as backfilling and sealing materials for HLW disposal into granite formations, due to its very low permeability and its ability to fill the remaining spaces. bentonite has also other interesting properties, such as, the radionuclide retention capacity by sorption processes. Once the clay barrier has been placed, the saturation process starts. The granite groundwater fills up the voids of the bentonite and because of the chemical interactions, the groundwater chemical composition varies. Near field processes, such as canister corrosion, waste leaching and radionuclide release, strongly depends on the water chemical composition. Bentonite pore water composition is such a very important feature of the disposal system and its determination and its evolution have great relevance in the HLW deep geological disposal performance assessment. The process used for the determination of the clay barrier pore water chemistry temporal evolution, and its influence on the performance assessment, are presented in this paper. (Author)

  5. Radionuclides migration or isolation?

    International Nuclear Information System (INIS)

    Toulhoat, P.; Grambow, B.; Simoni, E.

    2005-01-01

    After 20 years of research, the chemical behaviour of actinides and fission products in nuclear waste disposal environments is much better understood. Consistent thermodynamic data have been gathered and allow much more accurate previsions. Through the considerable development of analytical spectroscopy, including time resolved laser fluorescence and X ray absorption, a better understanding of the chemical reactivity (complexation, sorption) of actinides and fission products at a molecular scale has been possible. Chemically reducing conditions are found in most selected disposal host rock formations, generally chosen for their high sorption capacity (clays); such conditions favour the chemical confinement of most radionuclides through precipitation or sorption. Low permeability host rocks participate to this confinement, as convective fluxes are lower than diffusive fluxes. The most recent performance assessment exercises have taken into account the recent progress of knowledge in the chemical evolution of the near field. They show that the dose rates at the outlet are far lower than existing recommendations for normal and most altered evolution scenarios. (authors)

  6. Radionuclide content in the Upper Vistula River sediments in a coal mining region in Poland (east-central Europe)

    International Nuclear Information System (INIS)

    Jasinska, M.; Mietelski, J.W.; Pociask-Karteczka, J.

    1998-01-01

    Hard coal mining activity is one of the Technologically Enhanced Natural Radiation sources introduced more than a hundred years ago in the southern part of Poland. This study of radionuclides (K-40, Ra-226, Ra-228) in river sediments showed the principal factors determining the specific activity of radionuclides are distance from mines and sorption by clay particles in river sediments. The K-40 specific activity varies between 185 and 595 Bq/kg. The highest Ra-228 and Ra-226 specific activities, 280-610 and 205-415 Bq/kg, respectively, were detected in sediments of the Vistula in the vicinity of Silesia region. 7 refs., 1 fig., 3 tabs

  7. Performance assessment of the disposal of vitrified high-level waste in a clay layer

    International Nuclear Information System (INIS)

    Mallants, Dirk; Marivoet, Jan; Sillen, Xavier

    2001-01-01

    Deep disposal is considered a safe solution to the management of high-level radioactive waste. The safety is usually demonstrated by means of a performance assessment. This paper discusses the methodological aspects and some of the results obtained for the performance assessment of the disposal of vitrified high-level waste in a clay layer in Belgium. The calculations consider radionuclide migration through the following multi-barrier components, all of which contribute to the overall safety: (1) engineered barriers and the host clay layer, (2) overlying aquifer, and (3) biosphere. The interfaces between aquifers and biosphere are limited to the well and river pathway. Results of the performance assessment calculations are given in terms of the time evolution of the dose rates of the most important fission and activation products and actinides. The role of the glass matrix in the overall performance of the repository is also discussed

  8. Complementary modelling of radionuclide retention in the near-surface system at Forsmark. Development of a reactive transport model using Forsmark 1.2 data

    Energy Technology Data Exchange (ETDEWEB)

    Sena, Clara; Grandia, Fidel; Arcos, David; Molinero, Jorge; Duro, Lara (Amphos XXI Consulting S.L., Barcelona (Spain))

    2008-10-15

    The Swedish Nuclear Fuel and Waste Management Company (SKB) is conducting a comprehensive geoscientific characterization of two alternative sites to allocate a deep geological repository of high level nuclear waste. The Site Characterization Program also includes the near-surface systems, which are expected to constitute the last geological barrier between the repository system and the earth's surface. The evaluation of the retention capacity of the near surface systems is, therefore, very relevant for the site characterization program. From the geological point of view, near-surface systems in the Forsmark area consist of Quaternary deposits that overlay a granitic bedrock. Glacial till is the most abundant outcropping Quaternary deposit (approx75% of surface extension) and the remainder is made up of clayey materials (glacial and post-glacial clays). These types of near-surface sediments show distinctive hydraulic and geochemical features. The main reactive mineral in the till deposits, for the time scale considered in this work, is calcium carbonate (calcite). This mineral is found along with clay minerals (e.g. illite) and Fe(III) hydroxides. In contrast, glacial and post-glacial clays are basically composed of illite with minor amounts of calcium carbonate, and containing organic matter-rich levels (gyttja) which can promote reducing conditions in the system. The assessment of the migration behaviour of selected long-lived radionuclides through the near-surface system of Forsmark was developed in an earlier work, that focused on the evaluation of the capacity of the Quaternary deposits for radionuclide retention. The work reported here is an improvement of the geochemical conceptual and numerical model already presented, based on data available in the Site Descriptive Model v 1.2 (Forsmark). Regarding the geochemical variability of the Quaternary deposits present at Forsmark and its implications on radionuclide mobility through the near-surface systems, a

  9. In-situ nanoscale imaging of clay minerals with atomic force microscopy

    International Nuclear Information System (INIS)

    Bosbach, D.

    2010-01-01

    Document available in extended abstract form only. Clay minerals play a key role in many concepts for high-level nuclear waste repository systems in deep geological formations. Various aspects related to the long-term safety of nuclear disposal are linked to their fundamental physical-chemical properties, in particular with respect to their reactivity in aqueous environments. Atomic Force Microscopy (AFM) allows high resolution imaging of clay minerals in-situ while they are exposed to an aqueous solution. The presentation is intended to provide an overview of examples of AFM studies on clay minerals: 1. AFM is an ideal tool to visualize the shape of individual clay particles down to molecular scales including a quantitative description of for example their aspect ratio. Furthermore, the particle size can be easily extracted from AFM data for individual particles as well as particle size distribution. 2. Surface area of clay minerals is a key issue when discussing heterogeneous reactions such as dissolution, adsorption or (surface) precipitation - total surface area, BET surface area, reactive surface area need to be distinguished. In particular reactive surface area is linked to specific reactive surface sites. AFM is of course able to identify such sites and consequently AFM data allow to characterize and to quantify reactive surface area. 3. The reactivity of clay mineral surfaces in aqueous environments controls the behaviour of clay minerals under repository conditions and also affects the migration/retention of radionuclides. It could be shown that the dissolution of smectite particles under acidic conditions at room temperature primarily occurs at (hk0) particle edges, whereas the reactivity of the (001) basal surfaces is very limited. The heterogeneous (surface) precipitation of secondary iron (hydr)oxides phase could be unraveled by AFM observations. Surface precipitation occurs preferentially at (hk0) edges surfaces. Ignoring the surface site specific

  10. Determination of geochemical characters of insterstitial waters of pleistocene Italian clay formations

    International Nuclear Information System (INIS)

    Fontanive, A.; Gragnani, R.; Mignuzzi, C.; Spat, G.

    1985-01-01

    The geochemical characters of clay formations and of their pore water are fundamental with regards to the mobility of the radionuclides as well as to the corrosion processes on enginered barriers. Experimental researches have been carried out in different types of clay, which represent Italian formations, for the characterization of pore water. A squeezer system, which reaches 1500 Kg/cm 2 in pressure, and an analytical micro-scale methodology, for the determination of dissolved constituents in pore water, were set up. The extracted pore water ranges from 60% to 85% in relation to consolidation state of clay. The chemical composition of the extracted fluid has been checked during the squeezing. During this step the observed variations were smaller than those between the different specimens of the same sample. The comparison between the results obtained by squeezing and by a multiple washing technique, using increasing water/sediment ratios, shows that the last one does not give reliable results on the chemical composition of pore water. This is due to the presence of easily weatherable minerals and to the exchange processes between the clayey minerals and the solution. Nevertheless both these techniques have supplied complementary information about geochemical processes in water-rock interaction. The salinity of pore water ranges from 0.45 g/l to 24.5 g/l and the chemism always shows a high content of calcium-magnesium sulfate, or sodium chloride or calcium-magnesium-sulfate with sodium chloride. The correlation between geochemical composition of pore water and mineralogical composition of clay is not significant

  11. Toxicity of inhaled 144Ce fused clay particles in beagle dogs. VII

    International Nuclear Information System (INIS)

    Hahn, F.F.; Boecker, B.B.; Hobbs, C.H.; Jones, R.K.; Mauderly, J.L.; McClellan, R.O.; Pickrell, J.A.

    1974-01-01

    The metabolism, dosimetry, and effects of inhaled 144 Ce in fused clay particles are being investigated in the Beagle dog to aid in assessing the biological consequences of release of 144 Ce in a relatively insoluble form such as might occur in certain types of nuclear accidents. The toxicity of inhaled 144 Ce fused clay is also of general interest since it is representative of intermediate-lived beta-emitting radionuclides. Two major studies with young adult dogs (12 to 14 months of age at exposure) are involved: (1) a metabolism and dosimetry study in which 24 dogs were serially sacrificed over an extended period of time, and (2) a longevity study with 2 series of dogs; Series I with 15 dogs exposed to aerosols of 144 Ce in fused clay particles to yield initial lung burdens of 11 to 210 μCi/kg body weight and 3 control dogs exposed to nonradioactive fused clay particles and Series II with 96 dogs exposed to aerosols of 144 Ce in fused clay particles to yield initial lung burdens of 0.0024 to 66 μCi/kg body weight and 12 control dogs exposed to nonradioactive fused clay particles. Twenty-eight dogs died or were euthanized at 143 to 2396 days after inhalation of 144 Ce. The prominent findings were radiation pneumonitis in 17 dogs that died or were euthanized at early time periods and neoplastic disease in 10 of the 11 dogs that died or were euthanized at 750 days or later; 5 with hemangiosarcoma of the lung, 1 with both a hemangiosarcoma and a fibrosarcoma of the lung, 1 with both a bronchiolo-alveolar carcinoma and a hemangiosarcoma of lung, 1 with a hemangiosarcoma of lung, bronchiolo-alveolar carcinoma, and a bronchiogenic adenocarcinoma, and 1 each with a hemangiosarcoma of the mediastinum and of the spleen. The cumulative radiation dose to the lung at time of death has ranged from 22,000 to 140,000 rads. Serial observations are continuing on the 83 survivors and 15 controls. (U.S.)

  12. Incorporation of low and intermediate level wastes into ceramic clay matrices

    International Nuclear Information System (INIS)

    Kuznetsov, A.S.; Kuznetzov, B.S.; Kuznetzov, B.S.; Na, R.

    1995-01-01

    Conditions for the production of chemically stable high-strength ceramics based on clay are developed using wastes of three types: ashes from radioactive waste burning, hydroxide pulp formed during precipitations in radiochemical technology, suspensions of spent filtering material (filter perlite). The properties of wastes and ceramics are studied by emission spectrography, X-ray phase analysis, mechanical strength and chemical stability of end products are determined. It is shown that the ceramics incorporating 30-50 % wt. of wastes have the apparent density 2.1-2.5 g/cm 3 , the compression strength 40-70 MPa; the radionuclide leaching rate is comparable with the values obtained for borosilicate glasses. (authors)

  13. Performance assessment of an alpha waste deposit in a clay formation

    International Nuclear Information System (INIS)

    Quercia, F.; D'Alessandro, M.; Saltelli, A.

    1987-01-01

    The probabilistic code LISA (Long term Isolation Safety Assessment) has been used to assess the risk related to the disposal of alpha waste in a geological formation. The code has been modified to take into account waste form properties and leaching processes pertinent to alpha waste produced at fuel reprocessing plants. The exercise refers to a repository in a deep clay formation located at Harwell (U.K.) where some hydrogeological data were available. Radionuclide migration through repository and geological barriers has been simulated together with biosphere contamination. Results of the assessment are presented as dose rate (or risk) distributions; a sensitivity analysis on input parameters has been performed

  14. Sorption of activation products on London clay and Dungeness aquifer gravel

    Energy Technology Data Exchange (ETDEWEB)

    Baston, G.M.N.; Berry, J.A.; Littleboy, A.K.; Pilkington, N.J. (AEA Decommissioning and Radwaste, Harwell Lab. (United Kingdom))

    1992-01-01

    The sortpion of a series of activation-product radionuclides onto London clay and Dungeness aquifer gravel from the nuclear reactor sites at Bradwell and Dungeness, has been examined. Batch sorption and through-diffusion experiments with clay determined chlorine as the chloride ion to be effectively non-sorbing; calcium to be weakly sorbing, whereas cobalt, nickel, niobium and samarium were moderately to strongly sorbing and silver was strongly sorbing. Distribution ratios (R[sub D] values) for Nb, Sm and Ag were found to have a strong dependence on the liquid-solid separation technique employed. The presence of high concentrations of calcium hydroxide led to lower values of R[sub D] for radioactive Ca but higher R[sub D] values for Sm and Ag. The sorption of Ni showed no apparent dependence on groundwater composition at low levels of dissolved organic carbon (DOC). The values of R[sub D] for Co decreased as the DOC content was increased by addition of humic materials. Batch sorption studies with aquifer gravel demonstrated that Ca is weakly sorbing whereas Nb, Ag and Eu are moderately to strongly sorbing. R[sub D] values for Ca and for Ag under neutral pH conditions show little sensitivity to the liquid/solid separation technique used. However, R[sub D] values for Nb and Eu under neutral pH conditions and for Ag in alkaline solution (pH = 11 - 12) show a marked effect. The aquifer gravel was found to be highly inhomogeneous unlike the clay and sorption was greatest on samples with a high proportion of sand, reflecting the clay mineral content. (orig.).

  15. The geochemical behaviour of selenium in the Boom Clay system - a XANES and EXAFS study

    International Nuclear Information System (INIS)

    2S, KULeuven, B-3001Leuven (Belgium))" data-affiliation=" (Center for surface Chemistry and Catalysis - M2S, KULeuven, B-3001Leuven (Belgium))" >Breynaert, Eric; 2S, KULeuven, B-3001Leuven (Belgium))" data-affiliation=" (Center for surface Chemistry and Catalysis - M2S, KULeuven, B-3001Leuven (Belgium))" >Dom, Dirk; 2S, KULeuven, B-3001Leuven (Belgium))" data-affiliation=" (Center for surface Chemistry and Catalysis - M2S, KULeuven, B-3001Leuven (Belgium))" >Vancluysen, Jacqueline; 2S, KULeuven, B-3001Leuven (Belgium))" data-affiliation=" (Center for surface Chemistry and Catalysis - M2S, KULeuven, B-3001Leuven (Belgium))" >Kirschhock, Christine E.A.; 2S, KULeuven, B-3001Leuven (Belgium))" data-affiliation=" (Center for surface Chemistry and Catalysis - M2S, KULeuven, B-3001Leuven (Belgium))" >Maes, Andre; Scheinost, Andreas C.

    2010-01-01

    Document available in extended abstract form only. In Belgium, the Boom Clay formation is studied as a reference host formation for the geological disposal of high-level and long-lived radioactive waste for more than 30 years. This formation mainly consists of mixed clay minerals (illite, inter-stratified illite-smectite), pyrite and immobile and dissolved natural organic matter. Since it provides good sorption capacities, very low permeability, and chemically reducing conditions due to the presence of pyrite (FeS 2 ), the Boom clay formation itself is considered to be the main barrier preventing radionuclide migration from the geological repository. Within this concept for geological storage Se 79 has been identified as one of the critical elements contributing to the final dose to man. Although the sorption and migration behaviour of Se in the Boom Clay system has been thoroughly studied, the speciation of Se in the Boom Clay system has never been identified spectroscopically. In all previous studies, the interpretation of the behaviour of Se in Boom Clay conditions has always been based on circumstantial evidence such as solubility measurements or comparison with the spectroscopically identified speciation of Se in model systems. Based on the XANES analysis, selenite is transformed into Se 0 confirming the previously proposed reduction of selenite in the Boom Clay system. Combination of the mass-balance for Se with the results from linear combination analysis of the XANES spectra provided new evidence for the sorption-reduction mechanism proposed to explain the interaction between Se(IV) and the BC solid phase. In addition, evidence was found that that the fate of Se(IV) in the BC system is completely dominated by its interaction with pyrite present in the Boom Clay. The combined EXAFS analysis of Se in Se 0 reference phases (hexagonal, monoclinic, Se-loaded pyrite) allowed to elucidate further details on the short-range structure of the reaction products formed

  16. 2. Annual Workshop Proceedings of the Integrated Project 'Fundamental Processes of Radionuclide Migration' - 6. EC FP IP FUNMIG

    International Nuclear Information System (INIS)

    Buckau, Gunnar; Kienzler, Bernhard; Duro, Lara; Montoya, Vanessa

    2007-06-01

    This Workshop combined various types of activities and meetings with the following objectives: Inform about the scientific progress; Inform about the administrative status; Inform/agree upon forthcoming reporting; Discuss various topics of interest (for example, various aspects of Integration ); Inform about and discuss training; Agree upon the forthcoming work program. Emphasis was on scientific-technical topics with administrative issues kept to the minimum necessary. The proceedings are divided into the following sections: Research, Technology and Development Components activity overviews, with summaries where scientific highlights were presented. These were: RTDC1: Influence of inorganic carbon of Ni(II) and Co(II) sorption on Na-illite and Opalinus clay; Adsorption of humics to iron oxides and its effects on ion adsorption. RTDC2: Sorption of Uranium onto granite and altered material from Aespoe HRL; Sorption and reduction of uranyl by Fe(II) minerals; Mobility of uranium during the reductive dissolution of iron oxides by sulfide; U(VI/IV) adsorption mechanism on biotite surfaces and clarification of the influence of redox reactions on the U(VI) adsorption. RTDC3: Interlayer hydration H 2 O 'paradigm' (mono-porosity model); Porosity/mineral distribution characterisation (mm-cm scale), GIS system for CO x 'transport pertinent' data sets. A topical session was held around subjects associated with performance assessment/the Safety Case, especially relevant for geologic disposal in crystalline rock. The topics were: Role of biogeochemical processes on radionuclide migration; Characterization of geochemical conditions in crystalline rock/ Process identification and verification by real system analysis; Fluid flow system characterization in crystalline rock (Effects of the heterogeneity and up-scaling). Individual Scientific and Technical Contributions, containing reviewed scientific and technical manuscripts: European OBservatory for Long-term Governance on

  17. 2. Annual Workshop Proceedings of the Integrated Project 'Fundamental Processes of Radionuclide Migration' - 6. EC FP IP FUNMIG

    Energy Technology Data Exchange (ETDEWEB)

    Buckau, Gunnar; Kienzler, Bernhard [FZK - Inst. fuer Nukleare Entsorgung, Ka rlsruhe (Germany); Duro, Lara; Montoya, Vanessa [Enviros Spain S.L., Barcelona (Spai n)

    2007-06-15

    This Workshop combined various types of activities and meetings with the following objectives: Inform about the scientific progress; Inform about the administrative status; Inform/agree upon forthcoming reporting; Discuss various topics of interest (for example, various aspects of Integration ); Inform about and discuss training; Agree upon the forthcoming work program. Emphasis was on scientific-technical topics with administrative issues kept to the minimum necessary. The proceedings are divided into the following sections: Research, Technology and Development Components activity overviews, with summaries where scientific highlights were presented. These were: RTDC1: Influence of inorganic carbon of Ni(II) and Co(II) sorption on Na-illite and Opalinus clay; Adsorption of humics to iron oxides and its effects on ion adsorption. RTDC2: Sorption of Uranium onto granite and altered material from Aespoe HRL; Sorption and reduction of uranyl by Fe(II) minerals; Mobility of uranium during the reductive dissolution of iron oxides by sulfide; U(VI/IV) adsorption mechanism on biotite surfaces and clarification of the influence of redox reactions on the U(VI) adsorption. RTDC3: Interlayer hydration H{sub 2}O 'paradigm' (mono-porosity model); Porosity/mineral distribution characterisation (mm-cm scale), GIS system for CO{sub x} 'transport pertinent' data sets. A topical session was held around subjects associated with performance assessment/the Safety Case, especially relevant for geologic disposal in crystalline rock. The topics were: Role of biogeochemical processes on radionuclide migration; Characterization of geochemical conditions in crystalline rock/ Process identification and verification by real system analysis; Fluid flow system characterization in crystalline rock (Effects of the heterogeneity and up-scaling). Individual Scientific and Technical Contributions, containing reviewed scientific and technical manuscripts: European OBservatory for Long-term Governance

  18. Experimental Studies of Engineered Barrier Systems Conducted at Los Alamos National Laboratory (FY16)

    Energy Technology Data Exchange (ETDEWEB)

    Caporuscio, Florie Andre [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Norskog, Katherine Elizabeth [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Maner, James [Univ. of Oklahoma, Norman, OK (United States). School of Geology and Geophysics; Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Palaich, Sarah [Univ. of California, Los Angeles, CA (United States). Dept. of Earth, Planetary, and Space Sciences; Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Cheshire, Michael C. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-08-04

    Over the past five years the Used Fuel Campaign has investigated Engineered Barrier Systems (EBS) at higher heat loads (up to 300°C) and pressure (150 bar). This past year experimental work was hindered due to a revamping of the hydrothermal lab. Regardless, two experiments were run this past year, EBS-18 and EBS-19. EBS-18 was run using Low Carbon Steel (LCS) and opalinus clay in addition to the bentonite and opalinus brine. Many of the past results were confirmed in EBS-18, such as the restriction of illite formation due to the bulk chemistry, pyrite degradation, and zeolite formation dependent on the bentonite and opalinus clay. The LCS show vast amounts of pit corrosion (over 100μm of corrosion in six weeks), leading a corrosion rate of 1083 μm/year. In addition, a mineral goethite, an iron-bearing hydroxide, formed in the pits of the LCS. Preliminary results from EBS-19 water chemistry are included but SEM imaging, micro probe and XRD are still needed for further results. Copper corrosion was investigated further and over 850 measurements were taken. It was concluded that pitting and pyrite degradation drastically increase the corrosion rate from 0.12 to 0.39 μm/day. However, the growth of a layer of the mineral chalcocite is thought to subdue the corrosion rate to 0.024 μm/day as observed in the EBS-13, a sixth month experiment. This document presents the findings of this past year.

  19. Imaging techniques in clay sciences: a key tool to go a step further

    International Nuclear Information System (INIS)

    Robinet, J.C.; Michau, N.; Schaefer, T.

    2012-01-01

    Document available in extended abstract form only. Clay-rocks and clay based materials are greatly considered in nuclear waste geological repository due to their multiple favourable properties (low permeability, low diffusion coefficients, high retention capacity for radionuclides, swelling...). In this context, the study of clays and clay rocks covers a large variety of scientific disciplines such as geology, mineralogy, geomechanics, geochemistry or hydrodynamics. These disciplines are linked together by a common issue which is the understanding and the predicting of clay and clay-rock behaviors and properties under various thermal-hydrological-mechanical- chemical (THMC) conditions. Linking the fundamental forces to macroscopic (from millimeter to several meters) behaviors and properties is nevertheless not straightforward for porous media such as clay-rocks and clay based materials. Currently, it remains a key challenge for the scientific community. Imaging techniques offer solutions to face up this challenge by characterizing the internal microstructure of material and rocks at different levels of resolution. Due to the reactivity of clay minerals with water (swelling, mechanical deformation) or with repository components (mineral transformations at iron, copper or concrete interfaces) and the multi-scale distribution of pore and mineral sizes, classically ranged from nano-meter to millimeter, imaging clay based materials and clay-rocks itself is unanimously recognized as a challenging task. In the 80's, despite several constraints and limits, the microstructure of clays had been intensively imaged using conventional 2D imaging techniques such as optical microscopy, X-ray radiography, scanning electron microscopy or transmission electron microscopy [1]. The images acquired using these techniques have given us a pictorial frame of reference of the internal structures of clay rocks and clay based materials at various resolution levels. They have also highlighted

  20. Characterization of groundwater flow in the environment of the Boom Clay (Campine, Belgium)

    International Nuclear Information System (INIS)

    Gedeon, M.; Labat, S.; Wemaere, I.; Wouters, L.

    2010-01-01

    Document available in extended abstract form only. In Belgium, the Boom Clay formation is considered as reference host rock for the geological disposal of radioactive waste. Aquifers surrounding the Boom Clay play a passive role in the context of the disposal safety whereby the radionuclides are diluted by groundwater flow. The groundwater flow in these aquifers has been studied since decades. This research involves observations of groundwater levels in the regional and local piezo-metric networks, several site investigations including geophysics and core-drilled boreholes and groundwater modelling. In this context, groundwater modelling represents the integration of the site characterization efforts and provides a comprehensive tool for constraining the models used in the safety assessment of the geological disposal. Since 1985, groundwater levels are observed monthly in the regional piezo-metric network. It consists of 142 filters monitoring the groundwater levels at 45 sites. Along with the observed groundwater levels from the local piezo-metric network (concentrated around the Mol-Dessel site for surface disposal), these data provide an excellent insight into the evolution of the groundwater levels. Moreover, they represent a calibration (validation) dataset for groundwater flow modelling. The groundwater system forming the environment of the Boom Clay host rock was characterized during several site investigation campaigns, within which seven core-drilled boreholes were realized, whereby hydraulic parameters and hydro-stratigraphy of the groundwater system could be collected. The dataset obtained from the above mentioned campaigns was complemented by archived data on hydraulic testing in the aquifers in order to build a comprehensive groundwater model integrating these data into a single numerical representation of the groundwater system. Three regional groundwater models have been developed integrating the site characterization data collected in the north

  1. Study of strontium sorption in Brazilian clays for their use as a barrier in repository of radioactive wastes

    International Nuclear Information System (INIS)

    Freire, Carolina Braccini; Tello, Cledola Cassia Oliveira de

    2008-01-01

    Wastes in general should be properly treated and stored. The the radioactive wastes also require suitable and safe management beginning in their generation until the storage in repository. The objective of this research was to characterize some Brazilian clays in order to evaluate the viability of their use in the backfill layer, one of the radioactive waste repository barriers. The main function of this barrier is to contribute in the delay of the radionuclides movement, and to prevent their release into the environment. Four clays provided by national suppliers were selected for the research: Ca-Bentonite (Dol 01), Na-Bentonite (Dol 02), Kaolinite (Ind 01) and Vermiculite (Ubm 04.) Their physical, chemical and mineralogical characteristics were determined, and also their sorption potential of Strontium cation. It was confirmed through theses results a direct relationship among their specific surface (SS), the capacity of cationic exchange (CCE) and pH. The CCE results followed this increasing order: Ind 01, Dol 01, and Dol 02. In accordance with the models of Freundlich (K f ) and Langmuir (M), the clays Dol 01 and Dol 02 were the best sorbers of Sr 2+ . The Gibbs free energy change (ΔG deg) was calculated for the sorption reactions between the clays and the cations, and it was negative for all clays, confirming the sorption reaction spontaneity. (author)

  2. Three-dimensional simulation of flow, salinity, sediment, and radionuclide movements in the Hudson River estuary

    International Nuclear Information System (INIS)

    Onishi, Y.; Trent, D.S.

    1985-04-01

    The three-dimensional, finite difference model, FLESCOT simulates time-varying movements of flow, turbulent kinetic energy, salinity, water temperature, sediment, and contaminants in estuarine, coastal, and ocean waters. The model was applied to a 106-km (66-mi) reach of the Hudson River estuary in New York between Chelsea and the mouth of the river. It predicted the time-varying, three-dimensional distributions of tidal flow, salinity, three separate groups of sediments (i.e., sand, silt, and clay), and a radionuclide ( 137 Cs) in both dissolved and particulate (those sorbed by sediments) forms for over 40 days. The model also calculated riverbed elevation changes caused by sediment deposition and bed erosion, bed sediment size distribution and armoring, and distributions of the particulate 137 Cs sorbed by sand, silt, and clay in the bed

  3. Usability of Clay Mixed Red Mud as Building Material in Transdanubian (Hungary) Region

    International Nuclear Information System (INIS)

    Sas, Z.; Somlai, J.J.; Szeiler, G.; Kovacs, T.

    2014-01-01

    The most commonly used building materials in Hungary and in numerous country of the world are the bricks, which made from clays. Due to the congenial internal structure properties of the clays these raw materials can be mixed with other materials, provides great possibility to reuse industrial by-products as additive material. The production and inbuilt of new types of synthetic building materials based on NORM (naturally occurring radioactive materials) by-products is raising concerns among authorities, public and scientists. Several NORM residues produced in large quantity, such as: phospogypsum (phosphate industry), red mud (aluminium processing industry), fly ash, coal slag (coal burning and steelworks) and so on are presently under investigation. The aluminum manufacturing in Ajka (Hungary) started in 1943. As a result of the bauxite refining activities up to now approximately 30 Mt of red mud has been produced in Hungary, stored in reservoirs. The radionuclide content of the bauxite usually exceeds the world average in soils (WA), which entirely remains in the by-product during Bayer process. The exposure pathways in case of application of NORM residues have to be explored in order to reveal the potential risks of NORMs on residents. The gamma radiation originated from the primordial radionuclides (K-40; U-238; Th-232) and their daughter elements found in nature and in building materials as well increase the external dose of the human body. In the EU the Radiation Protection 112 (RP 112) guideline serves for classification of building material, wherein the gamma exposure is limited by I-index

  4. Characterization of clay (bentonite)/crushed granite mixtures to build barriers against the migration of radionuclides: diffusion studies and physical properties

    International Nuclear Information System (INIS)

    Mingarro, E.; Rivas, P.; Villar, L.P. del; Cruz, B. de la; Gomez, P.; Hernandez, A.; Turrero, M.J.; Villar, M.V.; Campos, R.; Cozar, J.

    1991-01-01

    In Spain, the possibility is being considered of storage of radioactive waste in granitic rocks, using Spanish clays as backfill and sealing materials. The study and selection of these materials is the objective of the project, accomplished with Community financial support under CEC contract No Fl1W-0191-E (TT). With the aim of minimizing the chemical-mineralogical disequilibrium between the granitic rock and the artificial barrier, the possibility has been studied of using molten granite as an additive and illite as clayish material, instead of the normal use of smectite (montmorillonite). The studies have been carried out on 30 commercial Spanish clays and two kinds of granite and have been orientated to the selection of materials and the optimization of the clay-granite mixtures, chemical characterization, mechanics and physics of the mixtures and compacted blocks, determination of their behaviour in the gradient fields of temperature, pressure and chemical potentials and to the determination of the migration parameters. 59 Figs.; 6 Micrograph; 52 Tabs.; 30 Refs

  5. Protocol for characterization of clay as a backfill and coverage layers for surface repository

    International Nuclear Information System (INIS)

    Santos, Daisy M.M.; Tello, Clédola C.O.

    2017-01-01

    The Radioactive Waste Management includes the operations since generation of the waste until its storage in repository, ensuring the protection of human beings and the environment from the possible negative impacts. The radioactive waste is segregated, treated, conditioned in suitable packages for posterior storage or disposal in repository. The 'RBMN Project' objective is to implement the repository for the disposal of low and intermediate level radioactive wastes generated by nuclear activities in Brazil, proposing a definitive solution for their storage. Engineered and natural barriers as the backfill and coverage layers will compose the disposal system of a near surface repository, concept proposed by the 'RBMN Project'. The use of these barriers aims to avoid or restrict the release of radionuclides from the waste to the human beings and environment. The waterproofing barriers are composed of clays. Certainly, for the national repository, will be used those clays existing in the place where it will be constructed. Them some basic tests will have to be carried out to verify the suitability of these clays as barriers. These tests were determined and performed with reference clay, a Brazilian bentonite constituted of 67.2% montmorillonite. The results were compared with national and international literature of materials with similar mineralogical features. The values found with 95% of confidence interval were 9.73±0,35 μm for granulometric size; 13,3±0,6% for the moisture content and 816±9 mmol.kg -1 for the capacity of cationic exchange. A protocol for characterization of clay was elaborated presenting these tests for it future use. (author)

  6. Protocol for characterization of clay as a backfill and coverage layers for surface repository

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Daisy M.M.; Tello, Clédola C.O., E-mail: marymarchezini@gmail.com, E-mail: tellocc@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2017-07-01

    The Radioactive Waste Management includes the operations since generation of the waste until its storage in repository, ensuring the protection of human beings and the environment from the possible negative impacts. The radioactive waste is segregated, treated, conditioned in suitable packages for posterior storage or disposal in repository. The 'RBMN Project' objective is to implement the repository for the disposal of low and intermediate level radioactive wastes generated by nuclear activities in Brazil, proposing a definitive solution for their storage. Engineered and natural barriers as the backfill and coverage layers will compose the disposal system of a near surface repository, concept proposed by the 'RBMN Project'. The use of these barriers aims to avoid or restrict the release of radionuclides from the waste to the human beings and environment. The waterproofing barriers are composed of clays. Certainly, for the national repository, will be used those clays existing in the place where it will be constructed. Them some basic tests will have to be carried out to verify the suitability of these clays as barriers. These tests were determined and performed with reference clay, a Brazilian bentonite constituted of 67.2% montmorillonite. The results were compared with national and international literature of materials with similar mineralogical features. The values found with 95% of confidence interval were 9.73±0,35 μm for granulometric size; 13,3±0,6% for the moisture content and 816±9 mmol.kg{sup -1} for the capacity of cationic exchange. A protocol for characterization of clay was elaborated presenting these tests for it future use. (author)

  7. Comprehensive review of geosynthetic clay liner and compacted clay liner

    Science.gov (United States)

    Shankar, M. Uma; Muthukumar, M.

    2017-11-01

    Human activity inevitably produces waste materials that must be managed. Some waste can be reused. However many wastes that cannot be used beneficially must be disposed of ensuring environmental safety. One of the common methods of disposal is landfilling. The most common problems of the landfill site are environmental degradation and groundwater contamination caused by leachate produced during the decomposition process of organic material and rainfall. Liner in a landfill is an important component which prevent leachate migration and prevent groundwater contamination. Earthen liners have been widely used to contain waste materials in landfill. Liners and covers for municipal and hazardous waste containment facilities are often constructed with the use of fine-grained, low plasticity soils. Because of low permeability geosynthetic clay liners and compacted clay liners are the main materials used in waste disposal landfills. This paper summaries the important geotechnical characteristics such as hydraulic conductivity, liquid limit and free swell index of geosynthetic clay liner and compacted clay liner based on research findings. This paper also compares geosynthetic clay liner and compacted clay liner based on certain criteria such as thickness, availability of materials, vulnerability to damage etc.

  8. JOINTS AND SYN-SEDIMENTARY FAULTS NETWORKS IN MARINE CLAYS AND MUDSTONES. Importance for Radwaste storage

    Science.gov (United States)

    Arnould, M.

    2009-12-01

    material with rather small throws are difficult to identify. Their number increases wifh accuracy of geophysical research. Conclusions for underground storage of radioactive waste . There are four underground laboratories on duty in mudstones and clays in Western Europe. No natural discontinuities, joints or faults have been observed during their excavation rapidly followed by lining.This draw some people to the imprudent conclusion that there were no natural discontinuities. In accordance to the very low permeabilities measured by in situ tests all natural discontinuities are closed up at depth by the stresss field. They are sealed but not healed because the temperature of diagenesis remained below 50°C. They can reopen by relaxation of stresses and by desiccation, as in Tournemire tunnel /URL in toarcian mudstones and at Mont Terri URL in Opalinus Clay. Open fissures visible in non lined parts of galleries appear weeks or months after the excavation. After the change of concept from burial to storage and retrievability the problem should not be underestimated. References : Arnould M (2006) Discontinuity networks in mudstones : a geological approach. Bull Eng Geol Environ. Springer ed 65:413-422 Skempton & al (1969) Joints and fissures in the London Clay at Wraysbury and Edgware Geotechnique 19 : 205-217.

  9. Clay dispersibility and soil friability – testing the soil clay-to-carbon saturation concept

    OpenAIRE

    Schjønning, P.; de Jonge, L.W.; Munkholm, L.J.; Moldrup, P.; Christensen, B.T.; Olesen, J.E.

    2011-01-01

    Soil organic carbon (OC) influences clay dispersibility, which affects soil tilth conditions and the risk of vertical migration of clay colloids. No universal lower threshold of OC has been identified for satisfactory stabilization of soil structure. We tested the concept of clay saturation with OC as a predictor of clay dispersibility and soil friability. Soil was sampled three years in a field varying in clay content (~100 to ~220 g kg-1 soil) and grown with different crop rotations. Clay ...

  10. The study of the migration of the radionuclide Am-241 in unsaturated soil from in Saligny area

    International Nuclear Information System (INIS)

    Toma, Alexandru Dan

    2005-01-01

    The functioning of the Cernavoda Nuclear Power Plant will generate low and medium radioactive waste contaminated with long-lived fission products (from U, Pu, Np, Am fission or decay), radioactive carbon (C-14) and tritium (H-3), which by their radiochemical characteristics and their influence upon the environment and people, request special attention regarding their storage and disposal. Based on the geological and mineralogical researches regarding the location of a repository for low and medium active waste, Saligny area near the Cernavoda Nuclear Power Plant was chosen. The repository will be located in loess, seated on sedimentary formations with insertions of clay patches. The main target of the research is to obtain some experimental data necessary for the evaluation of the migration of the radionuclide Am-241 (resulted from Cernavoda Nuclear Power Plant) in unsaturated soils in Saligny area, which will be the host of the Final Repository for Low and Medium Active Waste. The analysis of the test data obtained in the laboratory for the determination of the migration parameters of the radionuclide Am-241 in the material of the geological formation of Saligny area showed that there is a direct correlation between the values of these parameters and the basic mineralogical component - clay - of the soil sample. (author)

  11. Geological modeling of a fault zone in clay rocks at the Mont-Terri laboratory (Switzerland)

    Science.gov (United States)

    Kakurina, M.; Guglielmi, Y.; Nussbaum, C.; Valley, B.

    2016-12-01

    Clay-rich formations are considered to be a natural barrier for radionuclides or fluids (water, hydrocarbons, CO2) migration. However, little is known about the architecture of faults affecting clay formations because of their quick alteration at the Earth's surface. The Mont Terri Underground Research Laboratory provides exceptional conditions to investigate an un-weathered, perfectly exposed clay fault zone architecture and to conduct fault activation experiments that allow explore the conditions for stability of such clay faults. Here we show first results from a detailed geological model of the Mont Terri Main Fault architecture, using GoCad software, a detailed structural analysis of 6 fully cored and logged 30-to-50m long and 3-to-15m spaced boreholes crossing the fault zone. These high-definition geological data were acquired within the Fault Slip (FS) experiment project that consisted in fluid injections in different intervals within the fault using the SIMFIP probe to explore the conditions for the fault mechanical and seismic stability. The Mont Terri Main Fault "core" consists of a thrust zone about 0.8 to 3m wide that is bounded by two major fault planes. Between these planes, there is an assembly of distinct slickensided surfaces and various facies including scaly clays, fault gouge and fractured zones. Scaly clay including S-C bands and microfolds occurs in larger zones at top and bottom of the Mail Fault. A cm-thin layer of gouge, that is known to accommodate high strain parts, runs along the upper fault zone boundary. The non-scaly part mainly consists of undeformed rock block, bounded by slickensides. Such a complexity as well as the continuity of the two major surfaces are hard to correlate between the different boreholes even with the high density of geological data within the relatively small volume of the experiment. This may show that a poor strain localization occurred during faulting giving some perspectives about the potential for

  12. Multiscale Micromechanical Modeling of Polymer/Clay Nanocomposites and the Effective Clay Particle

    Science.gov (United States)

    Sheng, Nuo; Boyce, Mary C.; Parks, David M.; Manovitch, Oleg; Rutledge, Gregory C.; Lee, Hojun; McKinley, Gareth H.

    2003-03-01

    Polymer/clay nanocomposites have been observed to exhibit enhanced mechanical properties at low weight fractions (Wp) of clay. Continuum-based composite modeling reveals that the enhanced properties are strongly dependent on particular features of the second-phase ¡°particles¡+/-; in particular, the particle volume fraction (fp), the particle aspect ratio (L/t), and the ratio of particle mechanical properties to those of the matrix. However, these important aspects of as-processed nanoclay composites have yet to be consistently and accurately defined. A multiscale modeling strategy was developed to account for the hierarchical morphology of the nanocomposite: at a lengthscale of thousands of microns, the structure is one of high aspect ratio particles within a matrix; at the lengthscale of microns, the clay particle structure is either (a) exfoliated clay sheets of nanometer level thickness or (b) stacks of parallel clay sheets separated from one another by interlayer galleries of nanometer level height. Here, quantitative structural parameters extracted from XRD patterns and TEM micrographs are used to determine geometric features of the as-processed clay ¡°particles¡+/-, including L/t and the ratio of fp to Wp. These geometric features, together with estimates of silicate lamina stiffness obtained from molecular dynamics simulations, provide a basis for modeling effective mechanical properties of the clay particle. The structure-based predictions of the macroscopic elastic modulus of the nanocomposite as a function of clay weight fraction are in excellent agreement with experimental data. The adopted methodology offers promise for study of related properties in polymer/clay nanocomposites.

  13. 2. Annual Workshop Proceedings of the Integrated Project 'Fundamental Processes of Radionuclide Migration' - 6. EC FP IP FUNMIG

    Energy Technology Data Exchange (ETDEWEB)

    Buckau, Gunnar; Kienzler, Bernhard [FZK - Inst. fuer Nukleare Entsorgung, Ka rlsruhe (Germany); Duro, Lara; Montoya, Vanessa [Enviros Spain S.L., Barcelona (Spai n)] (eds.)

    2007-06-15

    This Workshop combined various types of activities and meetings with the following objectives: Inform about the scientific progress; Inform about the administrative status; Inform/agree upon forthcoming reporting; Discuss various topics of interest (for example, various aspects of Integration ); Inform about and discuss training; Agree upon the forthcoming work program. Emphasis was on scientific-technical topics with administrative issues kept to the minimum necessary. The proceedings are divided into the following sections: Research, Technology and Development Components activity overviews, with summaries where scientific highlights were presented. These were: RTDC1: Influence of inorganic carbon of Ni(II) and Co(II) sorption on Na-illite and Opalinus clay; Adsorption of humics to iron oxides and its effects on ion adsorption. RTDC2: Sorption of Uranium onto granite and altered material from Aespoe HRL; Sorption and reduction of uranyl by Fe(II) minerals; Mobility of uranium during the reductive dissolution of iron oxides by sulfide; U(VI/IV) adsorption mechanism on biotite surfaces and clarification of the influence of redox reactions on the U(VI) adsorption. RTDC3: Interlayer hydration H{sub 2}O 'paradigm' (mono-porosity model); Porosity/mineral distribution characterisation (mm-cm scale), GIS system for CO{sub x} 'transport pertinent' data sets. A topical session was held around subjects associated with performance assessment/the Safety Case, especially relevant for geologic disposal in crystalline rock. The topics were: Role of biogeochemical processes on radionuclide migration; Characterization of geochemical conditions in crystalline rock/ Process identification and verification by real system analysis; Fluid flow system characterization in crystalline rock (Effects of the heterogeneity and up-scaling). Individual Scientific and Technical Contributions, containing reviewed scientific and technical manuscripts: European OBservatory for

  14. Clay intercalation and influence on crystallinity of EVA-based clay nanocomposites

    International Nuclear Information System (INIS)

    Chaudhary, D.S.; Prasad, R.; Gupta, R.K.; Bhattacharya, S.N.

    2005-01-01

    Various polymer clay nanocomposites (PCNs) were prepared from ethylene vinyl acetate copolymer (EVA) with 9, 18 and 28% vinyl acetate (VA) content filled with different wt.% (2.5, 5 and 7.5) of a Montmorillonite-based organo-modified clay (Cloisite[reg] C15A and C30B). The PCNs were prepared using melt blending techniques. Morphological information regarding intercalation and exfoliation were determined by using wide-angle X-ray scattering (WAXS) and transmission electron microscopy (TEM). WAXS and TEM confirmed that increasing the VA content was necessary to achieve greater clay-polymer interaction as seen from the comparatively higher intercalation of clay platelets with 28% VA. The effect of addition of clay on the development and the modification of crystalline morphology in EVA matrix was also studied using WAXS and temperature-modulated differential scanning calorimetry (MDSC). Results are presented showing that the addition of clay platelets does not increase the matrix crystallinity but the morphology was significantly modified such that there was an increase in the 'rigid' amorphous phase. Mechanical properties were also evaluated against the respective morphological information for each specimen and there are indications that the level of clay-polymer interaction plays a significant role in such morphological modification, and in such a way that affects the final PCN mechanical properties which has wide and significant applications in the packaging industries

  15. Clay Dispersibility and Soil Friability-Testing the Soil Clay-to-Carbon Saturation Concept

    DEFF Research Database (Denmark)

    Schjønning, Per; de Jonge, Lis Wollesen; Munkholm, Lars Juhl

    2012-01-01

    Soil organic carbon (OC) influences clay dispersibility, which affects soil tilth conditions and the risk of vertical migration of clay colloids. No universal lower threshold of OC has been identified for satisfactory stabilization of soil structure. We tested the concept of clay saturation with OC...... as a predictor of clay dispersibility and soil friability. Soil was sampled 3 yr in a field varying in clay content (∼100 to ∼220 g kg−1 soil) and grown with different crop rotations. Clay dispersibility was measured after end-over-end shaking of field-moist soil and 1- to 2-mm sized aggregates either air......-dried or rewetted to −100 hPa matric potential. Tensile strength of 1- to 2-, 2- to 4-, 4- to 8-, and 8- to 16-mm air-dried aggregates was calculated from their compressive strength, and soil friability estimated from the strength–volume relation. Crop rotation characteristics gave only minor effects on clay...

  16. SBR Brazilian organophilic/clay nanocomposites

    International Nuclear Information System (INIS)

    Guimaraes, Thiago R.; Valenzuela-Diaz, Francisco R.; Morales, Ana Rita; Paiva, Lucilene B.

    2009-01-01

    The aim of this work is the obtaining of SBR composites using a Brazilian raw bentonite and the same bentonite treated with an organic salt. The clays were characterized by XRD. The clay addition in the composites was 10 pcr. The composites were characterized by XRD and had measured theirs tension strength (TS). The composite with Brazilian treated clay showed TS 233% higher than a composite with no clay, 133% higher than a composite with Cloisite 30B organophilic clay and 17% lower than a composite with Cloisite 20 A organophilic clay. XRD and TS data evidence that the composite with Brazilian treated clay is an intercalated nanocomposite. (author)

  17. Atrazine biodegradation modulated by clays and clay/humic acid complexes

    International Nuclear Information System (INIS)

    Besse-Hoggan, Pascale; Alekseeva, Tatiana; Sancelme, Martine; Delort, Anne-Marie; Forano, Claude

    2009-01-01

    The fate of pesticides in the environment is strongly related to the soil sorption processes that control not only their transfer but also their bioavailability. Cationic (Ca-bentonite) and anionic (Layered Double Hydroxide) clays behave towards the ionisable pesticide atrazine (AT) sorption with opposite tendencies: a noticeable sorption capacity for the first whereas the highly hydrophilic LDH showed no interactions with AT. These clays were modified with different humic acid (HA) contents. HA sorbed on the clay surface and increased AT interactions. The sorption effect on AT biodegradation and on its metabolite formation was studied with Pseudomonas sp. ADP. The biodegradation rate was greatly modulated by the material's sorption capacity and was clearly limited by the desorption rate. More surprisingly, it increased dramatically with LDH. Adsorption of bacterial cells on clay particles facilitates the degradation of non-sorbed chemical, and should be considered for predicting pesticide fate in the environment. - The biodegradation rate of atrazine was greatly modulated by adsorption of the pesticide and also bacterial cells on clay particles.

  18. Influence of Polymer-Clay Interfacial Interactions on the Ignition Time of Polymer/Clay Nanocomposites.

    Science.gov (United States)

    Zope, Indraneel S; Dasari, Aravind; Yu, Zhong-Zhen

    2017-08-11

    Metal ions present on smectite clay (montmorillonite) platelets have preferential reactivity towards peroxy/alkoxy groups during polyamide 6 (PA6) thermal decomposition. This changes the decomposition pathway and negatively affects the ignition response of PA6. To restrict these interfacial interactions, high-temperature-resistant polymers such as polyetherimide (PEI) and polyimide (PI) were used to coat clay layers. PEI was deposited on clay by solution-precipitation, whereas PI was deposited through a solution-imidization-precipitation technique before melt blending with PA6. The absence of polymer-clay interfacial interactions has resulted in a similar time-to-ignition of PA6/PEI-clay (133 s) and PA6/PI-clay (139 s) composites as neat PA6 (140 s). On the contrary, PA6 with conventional ammonium-based surfactant modified clay has showed a huge drop in time-to-ignition (81 s), as expected. The experimental evidences provided herein reveal the role of the catalytic activity of clay during the early stages of polymer decomposition.

  19. Uptake of radionuclides by plants growing on Brazilian soil: the effect of soil ageing

    International Nuclear Information System (INIS)

    Wasserman, Maria A.; Rochedo, Elaine R.R.; Ferreira, Ana C.M.; Vidal Perez, Daniel

    2008-01-01

    The behaviour of radionuclides in soil is governed by several mechanisms that can vary significantly according to the specific reactivity of each element and soil properties. The 137 Cs is one of radionuclides that generally reduces with time its mobility and phytoavailability due to irreversible fixation in high activity clay mineral such as illite, vermiculite and montmorilonite. A long-term experimental essay using Brazilian soils was done in order to determine the effect of ageing of contamination on 137 Cs mobility in soils and transfer to plants. To perform this study, 4 different soils with different properties were contaminated with 137 Cs at different period: The older contamination refers to an urban soil contaminated at the Goiania accident (1987). A similar type of Goiania's soil (Ferralsol rich in Gibbsite) was artificially contaminated with 137 Cs in 1993. A subtropical class of soil (Nitisol) was contaminated in 1996 and two other tropical soils were contaminated in 2000 (Acrisol and Ferralsol rich in Goethite). The time's effect was studied by characterizing the evolution of soil properties and the changes in the distribution of radionuclides between phases till 2006. In addition, the phytoavailability was evaluated by carrying out experiments in lysimeters where radish was sowed at different periods:1996, 2000 and 2004. These results showed that the phytoavailability changed with time only in 2 situations: after changes in some soil properties such as pH or due to Cs fixation in high activity clay mineral when it was present in the soils even as trace mineral. The 137 Cs distribution in soil showed that Fe oxides are the main sink for this element in all type of soil and 14 years after contamination, the 137 Cs was still available for plants in the Ferralsol Gbbiste rich. In the Nitisol, 5 years after contamination, the 137 Cs was not detected as in the slightly acidic phase of sequential extraction neither detectable in radish roots or leaves

  20. Phosphonium modified clay/polyimide nanocomposites

    International Nuclear Information System (INIS)

    Ceylan, Hatice; Çakmakçi, Emrah; Beyler-Çiǧil, Asli; Kahraman, Memet Vezir

    2014-01-01

    In this study, octyltriphenylphosphonium bromide [OTPP-Br] was prepared from the reaction of triphenylphosphine and 1 -bromooctane. The modification of clay was done by ion exchange reaction using OTPP-Br in water medium. Poly(amic acid) was prepared from the reaction of 3,3',4,4'-Benzophenonetetracarboxylic dianhydride (BTDA) and 4,4'-Oxydianiline (ODA). Polyimide(PI)/clay hybrids were prepared by blending of poly(amic acid) and organically modified clay as a type of layered clays. The morphology of the Polyimide/ phosphonium modified clay hybrids was characterized by scanning electron microscopy (SEM). Chemical structures of polyimide and Polyimide/ phosphonium modified clay hybrids were characterized by FTIR. SEM and FTIR results showed that the Polyimide/ phosphonium modified clay hybrids were successfully prepared. Thermal properties of the Polyimide/ phosphonium modified clay hybrids were characterized by thermogravimetric analysis (TGA)

  1. Radionuclide toxicity

    International Nuclear Information System (INIS)

    Galle, P.

    1982-01-01

    The aim of this symposium was to review the radionuclide toxicity problems. Five topics were discussed: (1) natural and artificial radionuclides (origin, presence or emission in the environment, human irradiation); (2) environmental behaviour of radionuclides and transfer to man; (3) metabolism and toxicity of radionuclides (radioiodine, strontium, rare gas released from nuclear power plants, ruthenium-activation metals, rare earths, tritium, carbon 14, plutonium, americium, curium and einsteinium, neptunium, californium, uranium) cancerogenous effects of radon 222 and of its danghter products; (4) comparison of the hazards of various types of energy; (5) human epidemiology of radionuclide toxicity (bone cancer induction by radium, lung cancer induction by radon daughter products, liver cancer and leukaemia following the use of Thorotrast, thyroid cancer; other site of cancer induction by radionuclides) [fr

  2. Natural and active chemical remediation of toxic metals and radionuclides in the aquatic environment

    International Nuclear Information System (INIS)

    McPherson, G.; Pintauro, P.; O'Connor, S.; Zhang, J.; Gonzales, R.; Flowers, G.

    1993-01-01

    The focus of this research is the non-biological, chemical remediation of toxic heavy metals and radionuclides in aquatic environments. This Tulane/Xavier group includes researchers from Chemistry, Chemical Engineering, and Geology. Active methods using novel zeolites and ion exchange membranes are currently being evaluated for use in removing heavy metals from natural waters. In addition, field and laboratory studies of metal ion exchange reactions and competitive, heavy metal adsorption on clay substrates are underway to determine sediment metal sequestering capacity. A summary of progress to date and future work is presented

  3. Toxicity of inhaled 90Sr fused clay particles in beagle dogs. V

    International Nuclear Information System (INIS)

    Snipes, M.B.; Boecker, B.B.; Hahn, F.F.; Hobbs, C.H.; Mauderly, J.L.; McClellan, R.O.; Pickrell, J.A.

    1974-01-01

    Studies on the metabolism, dosimetry, and biological effects of 90 Sr in fused clay particles in Beagle dogs have continued with a view toward defining the biological consequences of inhaling this important radionuclide in a relatively insoluble form. Seventy-two dogs were exposed to a polydisperse aerosol (AMAD 1.4 to 2.8 μm and sigma/sub g/ 1.4 to 2.7) of fused montmorillonite clay particles labeled with 90 Sr to achieve graded initial lung burdens (ILB) of 3.7 to 94 μCi/kg body weight; 12 control dogs were exposed to an aerosol of stable strontium in fused clay particles. These 84 dogs were assigned to the 90 Sr fused clay longevity study. An additional 26 dogs were exposed similarly (AMAD 1.9 to 2.5 μm and sigma/sub g/ 1.6 to 2.0) and assigned for sacrifice (Series II) at intervals after exposure to define metabolism and dosimetry of this aerosol in Beagle dogs. Of the 72 longevity dogs, 32 dogs having ILBs of 29 to 94 μCi/kg and cumulative doses to lung to death of 40,000 to 96,000 rads have died from radiation pneumonitis and/or pulmonary fibrosis from 159 to 477 days post-exposure. Fourteen dogs with ILBs of 15 to 36 μCi/kg and cumulative doses to lung to death of 34,000 to 68,000 rads have died from primary pulmonary hemangiosarcomas between 644 and 1214 days post-exposure. In addition, one dog developed a bronchiolo-alveolar carcinoma, another epidermoid carcinoma of the lung and a third, a squamous cell carcinoma in the nasal cavity. The remaining 26 exposed dogs and 12 controls of the longevity study are surviving at 1070 to 1707 days post-exposure. Dogs in the sacrifice series have been sacrificed to 1536 days post-exposure. (U.S.)

  4. Distribution functions to estimate radionuclide solid-liquid distribution coefficients in soils: the case of Cs

    Energy Technology Data Exchange (ETDEWEB)

    Ramirez-Guinart, Oriol; Rigol, Anna; Vidal, Miquel [Analytical Chemistry department, Faculty of Chemistry, University of Barcelona, Mart i Franques 1-11, 08028, Barcelona (Spain)

    2014-07-01

    In the frame of the revision of the IAEA TRS 364 (Handbook of parameter values for the prediction of radionuclide transfer in temperate environments), a database of radionuclide solid-liquid distribution coefficients (K{sub d}) in soils was compiled with data coming from field and laboratory experiments, from references mostly from 1990 onwards, including data from reports, reviewed papers, and grey literature. The K{sub d} values were grouped for each radionuclide according to two criteria. The first criterion was based on the sand and clay mineral percentages referred to the mineral matter, and the organic matter (OM) content in the soil. This defined the 'texture/OM' criterion. The second criterion was to group soils regarding specific soil factors governing the radionuclide-soil interaction ('cofactor' criterion). The cofactors depended on the radionuclide considered. An advantage of using cofactors was that the variability of K{sub d} ranges for a given soil group decreased considerably compared with that observed when the classification was based solely on sand, clay and organic matter contents. The K{sub d} best estimates were defined as the calculated GM values assuming that K{sub d} values were always log-normally distributed. Risk assessment models may require as input data for a given parameter either a single value (a best estimate) or a continuous function from which not only individual best estimates but also confidence ranges and data variability can be derived. In the case of the K{sub d} parameter, a suitable continuous function which contains the statistical parameters (e.g. arithmetical/geometric mean, arithmetical/geometric standard deviation, mode, etc.) that better explain the distribution among the K{sub d} values of a dataset is the Cumulative Distribution Function (CDF). To our knowledge, appropriate CDFs has not been proposed for radionuclide K{sub d} in soils yet. Therefore, the aim of this works is to create CDFs for

  5. Common clay and shale

    Science.gov (United States)

    Virta, R.L.

    2000-01-01

    Part of the 1999 Industrial Minerals Review. The clay and shale market in 1999 is reviewed. In the U.S., sales or use of clay and shale increased from 26.4 million st in 1998 to 27.3 million st in 1999, with an estimated 1999 value of production of $143 million. These materials were used to produce structural clay products, lightweight aggregates, cement, and ceramics and refractories. Production statistics for clays and shales and for their uses in 1999 are presented.

  6. Methods of separating short half-life radionuclides from a mixture of radionuclides

    International Nuclear Information System (INIS)

    Bray, L.A.; Ryan, J.L.

    1998-01-01

    The present invention is a method of obtaining a radionuclide product selected from the group consisting of 223 Ra and 225 Ac, from a radionuclide ''cow'' of 227 Ac or 229 Th respectively. The method comprises the steps of (a) permitting ingrowth of at least one radionuclide daughter from said radionuclide ''cow'' forming an ingrown mixture; (b) insuring that the ingrown mixture is a nitric acid ingrown mixture; (c) passing the nitric acid ingrown mixture through a first nitrate form ion exchange column which permits separating the ''cow'' from at least one radionuclide daughter; (d) insuring that the at least one radionuclide daughter contains the radionuclide product; (e) passing the at least one radionuclide daughter through a second ion exchange column and separating the at least one radionuclide daughter from the radionuclide product and (f) recycling the at least one radionuclide daughter by adding it to the ''cow''. In one embodiment the radionuclide ''cow'' is the 227 Ac, the at least one daughter radionuclide is a 227 Th and the product radionuclide is the 223 Ra and the first nitrate form ion exchange column passes the 227 Ac and retains the 227 Th. In another embodiment the radionuclide ''cow'' is the 229 Th, the at least one daughter radionuclide is a 225 Ra and said product radionuclide is the 225 Ac and the 225 Ac and nitrate form ion exchange column retains the 229 Th and passes the 225 Ra/Ac. 8 figs

  7. Effects of modified Clay on the morphology and thermal stability of PMMA/clay nanocomposites

    International Nuclear Information System (INIS)

    Tsai, Tsung-Yen; Lin, Mei-Ju; Chuang, Yi-Chen; Chou, Po-Chiang

    2013-01-01

    The potential to improve the mechanical, thermal, and optical properties of poly(methyl methacrylate) (PMMA)/clay nanocomposites prepared with clay containing an organic modifier was investigated. Pristine sodium montmorillonite clay was modified using cocoamphodipropionate, which absorbs UVB in the 280–320 nm range, via ion exchange to enhance the compatibility between the clay platelets and the methyl methacrylate polymer matrix. PMMA/clay nanocomposites were synthesized via in situ free-radical polymerization. Three types of clay with various cation-exchange capacities (CEC) were used as inorganic layered materials in these organic–inorganic hybrid nanocomposites: CL42, CL120, and CL88 with CEC values of 116, 168, and 200 meq/100 g of clay, respectively. We characterized the effects of the organoclay dispersion on UV resistance, effectiveness as an O 2 gas barrier, thermal stability, and mechanical properties of PMMA/clay nanocomposites. Gas permeability analysis demonstrated the excellent gas barrier properties of the nanocomposites, consistent with the intercalated or exfoliated morphologies observed. The optical properties were assessed using UV–Visible spectroscopy, which revealed that these materials have good optical clarity, UV resistance, and scratch resistance. The effect of the dispersion capability of organoclay on the thermal properties of PMMA/clay nanocomposites was investigated by thermogravimetric analysis and differential scanning calorimetry; these analyses revealed excellent thermal stability of some of the modified clay nanocomposites. - Highlights: ► We control the dispersion morphology by protonation of K2 into the clay. ► The CL120 and CL88, with the higher CEC, are more random intercalated by K2. ► We report these materials have good optical clarity, and UV resistance

  8. Selective Clay Placement Within a Silicate-Clay Epoxy Blend Nanocomposite

    Science.gov (United States)

    Miller, Sandi G (Inventor)

    2013-01-01

    A clay-epoxy nanocomposite may be prepared by dispersing a layered clay in an alkoxy epoxy, such as a polypropylene oxide based epoxide before combining the mixture with an aromatic epoxy to improve the nanocomposite's thermal and mechanical properties.

  9. Radionuclide migration in non-saline rock formations - status and perspectives

    International Nuclear Information System (INIS)

    Kienzler, B.; Geckeis, H.; Fanghaenel, T.

    2002-01-01

    The article is a condensed version of a paper presented at a workshop on 'Final Storage in Non-saline Rock Formations - Previous and Future German R and D Activities' at the Karlsruhe Research Center on April 8-9, 2002. The objectives, methods, and results of the research work performed at the Institute for Nuclear Waste Management (INE) of the Karlsruhe Research Center on the migration of radionuclides, in particular of the actinides, and the perspectives derived from these activities are described. The R and D work presented comprises laboratory studies of granite and clay as well as in situ experiments at the underground laboratories of Aespoe, Sweden, and Grimsel, Switzerland. An exemplary overview is presented of the findings about actinide migration in fractures, colloid migration in the shear zone of a granite formation, and the sorption of actinides and lanthanides onto clay and various argillaceous materials. Fundamental studies by INE of the problems outlined here include the elucidation of the structures and binding patterns of species sorbed onto surfaces, the stability and characteristics of colloids, the relevant basic thermodynamic features, and methodological developments. (orig.) [de

  10. Clay nanoparticles for regenerative medicine and biomaterial design: A review of clay bioactivity.

    Science.gov (United States)

    Mousa, Mohamed; Evans, Nicholas D; Oreffo, Richard O C; Dawson, Jonathan I

    2018-03-01

    Clay nanoparticles, composites and hydrogels are emerging as a new class of biomaterial with exciting potential for tissue engineering and regenerative medicine applications. Clay particles have been extensively explored in polymeric nanocomposites for self-assembly and enhanced mechanical properties as well as for their potential as drug delivery modifiers. In recent years, a cluster of studies have explored cellular interactions with clay nanoparticles alone or in combination with polymeric matrices. These pioneering studies have suggested new and unforeseen utility for certain clays as bioactive additives able to enhance cellular functions including adhesion, proliferation and differentiation, most notably for osteogenesis. This review examines the recent literature describing the potential effects of clay-based nanomaterials on cell function and examines the potential role of key clay physicochemical properties in influencing such interactions and their exciting possibilities for regenerative medicine. Copyright © 2018 Elsevier Ltd. All rights reserved.

  11. Thixotropic Properties of Latvian Clays

    OpenAIRE

    Lakevičs, Vitālijs; Stepanova, Valentīna; Ruplis, Augusts

    2015-01-01

    This research studies Latvia originated Devon (Tūja, Skaņkalne), quaternary (Ceplīši), Jurassic, (Strēļi) and Triassic (Vadakste) deposit clays as well as Lithuania originated Triassic (Akmene) deposit clays. Thixotropic properties of clay were researched by measuring relative viscosity of clay in water suspensions. Relative viscosity is measured with a hopper method. It was detected that, when concentration of suspension is increased, clay suspension’s viscosity also increases. It happens un...

  12. Methods of separating short half-life radionuclides from a mixture of radionuclides

    Science.gov (United States)

    Bray, Lane A.; Ryan, Jack L.

    1998-01-01

    The present invention is a method of obtaining a radionuclide product selected from the group consisting of .sup.223 Ra and .sup.225 Ac, from a radionuclide "cow" of .sup.227 Ac or .sup.229 Th respectively. The method comprises the steps of a) permitting ingrowth of at least one radionuclide daughter from said radionuclide "cow" forming an ingrown mixture; b) insuring that the ingrown mixture is a nitric acid ingrown mixture; c) passing the nitric acid ingrown mixture through a first nitrate form ion exchange column which permits separating the "cow" from at least one radionuclide daughter; d) insuring that the at least one radionuclide daughter contains the radionuclide product; e) passing the at least one radionuclide daughter through a second ion exchange column and separating the at least one radionuclide daughter from the radionuclide product and f) recycling the at least one radionuclide daughter by adding it to the "cow". In one embodiment the radionuclide "cow" is the .sup.227 Ac, the at least one daughter radionuclide is a .sup.227 Th and the product radionuclide is the .sup.223 Ra and the first nitrate form ion exchange column passes the .sup.227 Ac and retains the .sup.227 Th. In another embodiment the radionuclide "cow"is the .sup.229 Th, the at least one daughter radionuclide is a .sup.225 Ra and said product radionuclide is the .sup.225 Ac and the .sup.225 Ac and nitrate form ion exchange column retains the .sup.229 Th and passes the .sup.225 Ra/Ac.

  13. A new and improved methodology for qualitative and quantitative mineralogical analysis of Boom Clay

    International Nuclear Information System (INIS)

    Zeelmaekers, E.; Vandenberghe, N.; Honty, M.; De Craen, M.; Derkowski, A.; Van Geet, M.

    2010-01-01

    Document available in extended abstract form only. A good knowledge of the mineralogy of any host formation studied for geological disposal of high-level radioactive waste, is a prerequisite for understanding the geochemical environment which will determine the migration and retention behaviour of radionuclides. In this respect, the Boom Clay mineralogical composition has been extensively studied last decades as reference host formation (e.g. ARCHIMEDEARGILE project, OECD-NEA clay catalogue report) with the aim to provide reliable data for a safety assessment. However, a comparison of the available literature data clearly showed a serious discrepancy among studies, not only in the quantitative, but also in the qualitative mineralogical composition of the Boom Clay (SAFIR II). The reason for such a huge disagreement could be related, among others, to variable grain size distributions of the studied samples (sample heterogeneity) and differences in the methodological approaches. In particular, the unambiguous characterisation of clay minerals and the quantification of mixed-layer phases appeared as an everlasting problem. This study is aimed at achieving a consensus on the qualitative and quantitative mineralogical data of the Boom Clay using the most advanced techniques currently available in the clay science. A new sampling campaign was performed in such a way that samples are (20 in total) more or less regularly distributed over Boom Clay Formation, ensuring that variations in the grain size distributions due to silty clay-clayey silt layers alternations are accounted for. The novel concept based on an analysis at two levels was applied: (1) bulk rock and (2) clay fraction analysis. (1) A bulk rock analysis consists of conventional XRD analysis with the identification of the principal mineral phases. As a next step, the bulk rock was mixed with a ZnO internal standard and experimental diffraction patterns of randomly oriented powders were analyzed using &apos

  14. Clays in natural and engineered barriers for radioactive waste confinement - 5. International meeting. Book of abstracts

    International Nuclear Information System (INIS)

    2012-10-01

    The purpose of this fifth international meeting is to bring again together specialists in the different disciplines related to clays and clay minerals, with scientists from organizations engaged in disposal of radioactive waste in order to evaluate the progress of the research conducted in that field. Multidisciplinary approaches including geology, mineralogy, geochemistry, rheology, physics and chemistry of clay minerals and assemblages are required in order to provide a detailed characterization of the geological host formations considered for the disposal of radioactive waste and to assess the behaviour of engineered and natural barriers when submitted to various types of perturbations induced by such facilities. The evaluation of the performances of the natural barrier as well as of the impact of repository-induced disturbances upon the confinement properties of clay-rich geological formations constitute major objectives for the experimental programs being and/or to be conducted in underground research laboratories, for interpreting the subsequent scientific results, for modelling the long-term behaviour of radioactive waste repositories and carrying out safety assessment exercises. The meeting covers all the aspects of clay characterization and behaviour considered at various times and space scales relevant to confinement of radionuclides in clay from basic phenomenological processes description, to the global understanding of the performance and safety at repository and geological scales. Special emphasis will be put on the modelling of processes occurring at the mineralogical level within the clay barriers. The topics covered by the program of the meeting are also supposed to be coherent with the general objectives proposed within the Strategic Research Agenda elaborated through the Implementing Geological Disposal of Radioactive Waste Technology Platform (IGD-TP). In this context, the meeting will also offer a particular opportunity to present the more

  15. Clay minerals behaviour in thin sandy clay-rich lacustrine turbidites (Lake Hazar, Turkey)

    Science.gov (United States)

    El Ouahabi, Meriam; Hubert-Ferrari, Aurelia; Lamair, Laura; Hage, Sophie

    2017-04-01

    Turbidites have been extensively studied in many different areas using cores or outcrop, which represent only an integrated snapshot of a dynamic evolving flow. Laboratory experiments provide the missing relationships between the flow characteristics and their deposits. In particular, flume experiments emphasize that the presence of clay plays a key role in turbidity current dynamics. Clay fraction, in small amount, provides cohesive strength to sediment mixtures and can damp turbulence. However, the degree of flocculation is dependent on factors such as the amount and size of clay particles, the surface of clay particles, chemistry and pH conditions in which the clay particles are dispersed. The present study focuses on thin clayey sand turbidites found in Lake Hazar (Turkey) occurring in stacked thin beds. Depositional processes and sources have been previously studied and three types were deciphered, including laminar flows dominated by cohesion, transitional, and turbulence flow regimes (Hage et al., in revision). For the purpose of determine the clay behavior in the three flow regimes, clay mineralogical, geochemical measurements on the cores allow characterising the turbidites. SEM observations provide further information regarding the morphology of clay minerals and other clasts. The study is particularly relevant given the highly alkaline and saline water of the Hazar Lake. Clay minerals in Hazar Lake sediments include kaolinite (1:1-type), illite and chlorite (2:1-type). Hazar lake water is alkaline having pH around 9.3, in such alkaline environment, a cation-exchange reaction takes place. Furthermore, in saline water (16‰), salts can act as a shield and decrease the repulsive forces between clay particle surfaces. So, pH and salt content jointly impact the behaviour of clays differently. Since the Al-faces of clay structures have a negative charge in basic solutions. At high pH, all kaolinite surfaces become negative-charged, and then kaolinite

  16. Migration of uranium in the presence of clay colloids in a sandy aquifer

    International Nuclear Information System (INIS)

    Le Cointe, P.; Grambow, B.; Piscitelli, A.; Montavon, G.; Van der Lee, J.; Giffaut, E.; Schneider, V.

    2010-01-01

    Document available in extended abstract form only. In France, low and medium level radioactive waste of short period (nuclides with a half-life less than 31 years and an activity ranging from 100 to 1,000,000 Bq/g) is stored in concrete constructions on a surface site in Soulaines-Dhuys (Aube). The site was chosen for its simple geology: it entirely lays on an aquifer formation, the Upper Aptian sands, above a Lower Aptian impermeable clay formation. The site is surrounded by the Noues d'Amance stream, which serves as the single outlet of the groundwater on the site. The objective of this study is to improve knowledge of radionuclides migration in the aquifer formation to improve safety, using U(VI) as an example and focusing on colloids, capable of transporting U(VI) on long distances. The sediment is composed of two main phases: quartz and clay minerals (glauconite, with a small fraction of kaolinite and smectite), with relative amounts of 91 and 6% in weight, respectively. The aquifer water contains clay colloids, invisible to the eye though observed with SEM and TEM in a non disturbed sample. No signal was measured with usual light diffusion techniques and Asymmetric Flow Field-Flow Fractionation (AF4). Only the Laser Induced Breakdown Detection (LIBD) technique could characterize the size (between 30 and 70 nm) and the concentration (around 10 ppb) of the clay colloids. Batch experiments were carried out to define U(VI)-Quartz and U(VI)-Clay interactions, with U(VI) concentration, pH and pCO 2 being the studied variables. The data were modelled with the Chess geochemistry code developed at the Paris School of Mines and compared to literature. Davis applied model for U(VI)-Quartz interaction and Bradbury and Baeyens applied model for U(VI)-Illite interaction adequately describe the experimental data. To know if clay colloids can move freely in the groundwater, pore size was measured using X-ray microtomography. Nanoparticles tracing was done with

  17. Migration of uranium in the presence of clay colloids in a sandy aquifer

    Energy Technology Data Exchange (ETDEWEB)

    Le Cointe, P. [Laboratoire SUBATECH, UMR 6457 Ecole des Mines/CNRS/Universite, 4 rue A. Kastler, BP 20722, 44307 Nantes Cedex 03 (France); Centre de Geosciences, Ecole des Mines de Paris, 35 rue St-Honore, 77305 Fontainebleau Cedex (France); ANDRA 1/7 rue Jean Monnet - 92298 Chatenay Malabry Cedex (France); Grambow, B.; Piscitelli, A.; Montavon, G. [Laboratoire SUBATECH, UMR 6457 Ecole des Mines/CNRS/Universite, 4 rue A. Kastler, BP 20722, 44307 Nantes Cedex 03 (France); Van der Lee, J. [EDF R ete D, Site des Renardieres, Route de Sens - Ecuelles, 77250 Moret sur Loing (France); Giffaut, E.; Schneider, V. [ANDRA 1/7 rue Jean Monnet - 92298 Chatenay Malabry Cedex (France)

    2010-07-01

    Document available in extended abstract form only. In France, low and medium level radioactive waste of short period (nuclides with a half-life less than 31 years and an activity ranging from 100 to 1,000,000 Bq/g) is stored in concrete constructions on a surface site in Soulaines-Dhuys (Aube). The site was chosen for its simple geology: it entirely lays on an aquifer formation, the Upper Aptian sands, above a Lower Aptian impermeable clay formation. The site is surrounded by the Noues d'Amance stream, which serves as the single outlet of the groundwater on the site. The objective of this study is to improve knowledge of radionuclides migration in the aquifer formation to improve safety, using U(VI) as an example and focusing on colloids, capable of transporting U(VI) on long distances. The sediment is composed of two main phases: quartz and clay minerals (glauconite, with a small fraction of kaolinite and smectite), with relative amounts of 91 and 6% in weight, respectively. The aquifer water contains clay colloids, invisible to the eye though observed with SEM and TEM in a non disturbed sample. No signal was measured with usual light diffusion techniques and Asymmetric Flow Field-Flow Fractionation (AF4). Only the Laser Induced Breakdown Detection (LIBD) technique could characterize the size (between 30 and 70 nm) and the concentration (around 10 ppb) of the clay colloids. Batch experiments were carried out to define U(VI)-Quartz and U(VI)-Clay interactions, with U(VI) concentration, pH and pCO{sub 2} being the studied variables. The data were modelled with the Chess geochemistry code developed at the Paris School of Mines and compared to literature. Davis applied model for U(VI)-Quartz interaction and Bradbury and Baeyens applied model for U(VI)-Illite interaction adequately describe the experimental data. To know if clay colloids can move freely in the groundwater, pore size was measured using X-ray microtomography. Nanoparticles tracing was done with

  18. Fe(0)-clays interactions at 90°C under anoxic conditions: a comparative study between clay fraction of Callovo-Oxfordian and other purified clays

    International Nuclear Information System (INIS)

    Rivard, C.; Pelletier, M.; Villieras, F.; Barres, O.; Galmiche, M.; Ghanbaja, J.; Kohler, A.; Michau, N.

    2010-01-01

    Document available in extended abstract form only. In the context of the geological disposal of high-level radioactive waste it is of prime importance to understand the interactions between the saturated clay formation and steel containers. This can be achieved through an in-depth analysis of iron-clay interactions. Previous studies on the subject investigated the influence of solid/liquid ratio, iron/clay ratio, temperature and reaction time. The aim of the present study is to explain Callovo-Oxfordian-Fe(0) interactions by determining the role of each mineral phases present in the Callovo-Oxfordian (clay minerals, quartz, carbonates and pyrite) on the mechanisms of interaction between metal iron and clay particles. In that context, it is especially important to understand in detail the influence of clay nature and to obtain some insight about the relationships between interaction mechanisms at the molecular scale and crystallographic properties (particle size, TO or TOT layers, amount of edge faces...). The influence of the combination of different clays and the addition of other minerals must also be studied. In a first step, the Callovo-Oxfordian argillite from the Andra's underground research laboratory was purified to extract the clay fraction (illite, illite-smectite, kaolinite and chlorite). Batch experiments were carried out in anoxic conditions at 90 deg. C in the presence of background electrolyte (NaCl 0.02 M.L -1 , CaCl 2 0.04 M.L -1 ) for durations of one, three or nine months in the presence of metallic iron powder. Experiments without iron were used as control. The iron/clay ratio was fixed at 1/3 with a solid/liquid ratio of 1/20. The above mentioned experiments were also carried out in parallel on other purified clays: two smectites (Georgia bentonite and SWy2 from the Clay Minerals Society), one illite (illite du Puy) and one kaolinite (KGa2, from the Clay Minerals society). At the end of the experiments, solid and liquid phases were

  19. Euroclay 95. Clays and clay materials sciences. Book of abstracts

    Energy Technology Data Exchange (ETDEWEB)

    Elsen, A; Grobet, P; Keung, M; Leeman, H; Schoonheydt, R; Toufar, H [eds.

    1995-08-20

    The document contains the abstracts of the invited lecturers (18) and posters (247) presented at EUROCLAY `95. Clays and clay materials sciences. 13 items (4 from the invited lecturers and 12 from posters) have been considered within the INIS Subject Scope and indexed separately.

  20. Euroclay 95. Clays and clay materials sciences. Book of abstracts

    International Nuclear Information System (INIS)

    Elsen, A.; Grobet, P.; Keung, M.; Leeman, H.; Schoonheydt, R.; Toufar, H.

    1995-01-01

    The document contains the abstracts of the invited lecturers (18) and posters (247) presented at EUROCLAY '95. Clays and clay materials sciences. 13 items (4 from the invited lecturers and 12 from posters) have been considered within the INIS Subject Scope and indexed separately

  1. Clay particles as binder for earth buildings materials: a fresh look into rheology of dense clay suspensions

    Science.gov (United States)

    Landrou, Gnanli; Brumaud, Coralie; Habert, Guillaume

    2017-06-01

    In the ceramic industry and in many sectors, clay minerals are widely used. In earthen construction technique, clay plays a crucial role in the processing. The purpose of this research is to understand and modify the clay properties in earth material to propose an innovative strategy to develop a castable earth-based material. To do so, we focused on the modification of clay properties at fresh state with inorganic additives. As the rheological behaviour of clays is controlled by their surface charge, the addition of phosphate anion allows discussing deep the rheology of concentrated clay suspensions. We highlighted the thixotropic and shear thickening behaviour of a dispersed kaolinite clay suspensions. Indeed, by adding sodium hexametaphosphate the workability of clay paste increases and the behaviour is stable during time after a certain shear is applied. Moreover, we stress that the aging and the shift in critical strain in clay system are due to the re-arrangement of clay suspension and a decrease of deformation during time. The understanding of both effect: thixotropy and aging are crucial for better processing of clay-based material and for self-compacting clay concrete. Yet, studies need to pursue to better understand the mechanism.

  2. Radionuclide trap

    International Nuclear Information System (INIS)

    McGuire, J.C.

    1978-01-01

    The deposition of radionuclides manganese-54, cobalt-58 and cobalt-60 from liquid sodium coolant is controlled by providing surfaces of nickel or high nickel alloys to extract the radionuclides from the liquid sodium, and by providing surfaces of tungsten, molybdenum or tantalum to prevent or retard radionuclide deposition

  3. Clay particles as binder for earth buildings materials: a fresh look into rheology of dense clay suspensions

    Directory of Open Access Journals (Sweden)

    Landrou Gnanli

    2017-01-01

    Full Text Available In the ceramic industry and in many sectors, clay minerals are widely used. In earthen construction technique, clay plays a crucial role in the processing. The purpose of this research is to understand and modify the clay properties in earth material to propose an innovative strategy to develop a castable earth-based material. To do so, we focused on the modification of clay properties at fresh state with inorganic additives. As the rheological behaviour of clays is controlled by their surface charge, the addition of phosphate anion allows discussing deep the rheology of concentrated clay suspensions. We highlighted the thixotropic and shear thickening behaviour of a dispersed kaolinite clay suspensions. Indeed, by adding sodium hexametaphosphate the workability of clay paste increases and the behaviour is stable during time after a certain shear is applied. Moreover, we stress that the aging and the shift in critical strain in clay system are due to the re-arrangement of clay suspension and a decrease of deformation during time. The understanding of both effect: thixotropy and aging are crucial for better processing of clay-based material and for self-compacting clay concrete. Yet, studies need to pursue to better understand the mechanism.

  4. Cadastral valuation of land contaminated with radionuclides

    Science.gov (United States)

    Ratnikov, A. N.; Sapozhnikov, P. M.; Sanzharova, N. I.; Sviridenko, D. G.; Zhigareva, T. L.; Popova, G. I.; Panov, A. V.; Kozlova, I. Yu.

    2016-01-01

    The methodology and procedure for cadastral valuation of land in the areas contaminated with radionuclides are presented. The efficiency of rehabilitation measures applied to decrease crop contamination to the levels satisfying sanitary-hygienic norms is discussed. The differentiation of cadastral value of radioactively contaminated agricultural lands for the particular farms and land plots is suggested. An example of cadastral valuation of agricultural land contaminated during the Chernobyl Nuclear Power Plant accident is given. It is shown that the use of sandy and loamy sandy soddy-podzolic soils with the 137Cs contamination of 37-185 and >185 kBq/m2 for crop growing is unfeasible. The growing of grain crops and potatoes on clay loamy soddy-podzolic soils with the 137Cs contamination of 555-740 kBq/m2 is unprofitable. The maximum cadastral value of radioactively contaminated lands is typical of leached chernozems.

  5. Synthesis of templated carbons starting from clay and clay-derived zeolites for hydrogen storage applications

    CSIR Research Space (South Africa)

    Musyoka, Nicholas M

    2014-10-01

    Full Text Available 57 58 59 60 For Peer Review 1 Synthesis of templated carbons starting from clay and clay-derived zeolites for hydrogen storage applications N. M. Musyoka1*, J. Ren1, H. W. Langmi1, D. E. C. Rogers1, B. C. North1, M. Mathe1 and D. Bessarabov2... clear (filtered) extract of cloisite clay, SNC for zeolite from unfiltered cloisite clay extract and SBC for zeolite from unfiltered South African bentonite clay extract. Furfuryl alcohol (Sigma Aldrich, C5H6O2, 98%) and Ethylene gas were used...

  6. ENSI's view on NTB 08-02 'Report on how to handle the recommendations in expert reports and statements of views on the demonstration of the nuclear waste disposal programme'

    International Nuclear Information System (INIS)

    2012-03-01

    In the framework of a review of the project Opalinus clay for the disposal of spent fuel assemblies, high-level radioactive waste and long living intermediate-level waste, a team of experts worked out numerous recommendations to be considered in the future. In 2006, the Swiss Federal Council stated that the realization of a radioactive waste disposal had been demonstrated to be possible. At the same time, the operators of the Swiss nuclear power plants were instructed to answer the open questions and to decide how they would proceed in the future. Similarly, the National Cooperative for the Disposal of Radioactive Waste (NAGRA) presented a report which ENSI had to review and evaluate. This review is reported in the present document. The NAGRA report, as well as ENSI's comments, is structured in accordance with the 200 recommendations made by the experts' team. ENSI states that the recommendations and all open questions of the experts' team were treated completely and transparently by NAGRA; they were considered in the elaboration of proposals for underground storage sites. ENSI declares that the recommendations for the demonstration of the feasibility of the waste disposal were given the correct priority. An important mile stone for more precise indications about site specific data will be the future request for the granting of the framework license, at the end of the site selection process, according to the Sectoral Plan for Geologic Deep Repositories. The recommendations about Opalinus clay as host rock are of general nature. They concern a repository for high-level (HLW) waste as well as for low- and intermediate-level (ILW) wastes. They also concern techniques independent of the host rock, like how to handle filling and sealing material. In step 1 of the Sectoral Plan, besides the Opalinus clay NAGRA proposed exclusively clay-rich host rocks with similar properties. Opalinus clay was proposed for 5 of the 6 potential disposal sites for a ILW repository. Some

  7. Radionuclide cisternography

    International Nuclear Information System (INIS)

    Song, H.H.

    1980-01-01

    The purpose of this thesis is to show that radionuclide cisternography makes an essential contribution to the investigation of cerebrospinal fluid (CSF) dynamics, especially for the investigation of hydrocephalus. The technical details of radionuclide cisternography are discussed, followed by a description of the normal and abnormal radionuclide cisternograms. The dynamics of CFS by means of radionuclide cisternography were examined in 188 patients in whom some kind of hydrocephalus was suspected. This study included findings of anomalies associated with hydrocephalus in a number of cases, such as nasal liquorrhea, hygromas, leptomeningeal or porencephalic cysts. The investigation substantiates the value of radionuclide cisternography in the diagnosis of disturbances of CSF flow. The retrograde flow of radiopharmaceutical into the ventricular system (ventricular reflux) is an abnormal phenomenon indicating the presence of communicating hydrocephalus. (Auth.)

  8. Research of Deformation of Clay Soil Mixtures Mixtures

    OpenAIRE

    Romas Girkontas; Tadas Tamošiūnas; Andrius Savickas

    2014-01-01

    The aim of this article is to determine clay soils and clay soils mixtures deformations during drying. Experiments consisted from: a) clay and clay mixtures bridges (height ~ 0,30 m, span ~ 1,00 m); b) tiles of clay and clay, sand and straw (height, length, wide); c) cylinders of clay; clay and straw; clay, straw and sand (diameter; height). According to the findings recommendations for clay and clay mixtures drying technology application were presented. During the experiment clay bridge bear...

  9. Experimental Studies to Evaluate the Role of Colloids on the Radionuclide Migration in a Crystalline Medium

    International Nuclear Information System (INIS)

    Albarran, Nairoby; Missana, Tiziana; Alonso, Ursula; Garcia-Gutierrez, Miguel; Mingarro, Manuel; Lopez, Trinidad

    2008-01-01

    In a deep geological repository (DGR) of high level radioactive waste, all the possible phenomena affecting radionuclide migration have to be studied to assess its security over time. Colloids can play an important role for contaminant transport if the following conditions are fulfilled: colloids exist in a non negligible concentration, they are mobile and stable in the environment of interest, and they are able to adsorb radionuclides irreversibly. In this study, different transport experiments where performed to improve the knowledge on the main mechanisms affecting the radionuclide migration in the presence of colloids in a crystalline medium. Firstly, colloid stability was analysed and then transport experiments in an artificial granite longitudinal fracture were carried out. Synthetic colloids of different size and bentonite clay colloids were used to evaluate the effects of colloid size, charge, and water flow rate on their mobility. Results showed that both major importance of the water flow rate on the mobility of colloids and their recovery and a higher interaction of smaller particles with the surface. Finally, the migration behaviour of Sr, and Sr adsorbed onto bentonite colloids was compared. The elution curves of Sr adsorbed onto colloid were significantly different from the ones of Sr alone, pointing out that sorption/desorption mechanisms must be taken into account to understand the radionuclide migration in the fracture in the presence of colloids. (authors)

  10. Geology of Northwestern Switzerland - with special emphasis on Opalinus Clay

    International Nuclear Information System (INIS)

    Burkhard, M.

    2007-01-01

    This report describes the variations of the geological structures of Northwestern Switzerland during about the last 200 million years. This gives an explanation for the present partition of the different rock layers in the studied domain. The geology of Switzerland is dominated by the formation of the Alps. The Mont Terri geology is best explained within the framework of the tectonic Wilson cycle: assembly of Pangea in Late Paleozoic times culminating in the Variscan orogeny, collapse and decay of this earlier mountain chain, peneplanation and new rifting leading to the opening of the alpine Tethys Ocean during the Mesozoic, followed by plate convergence, subduction, collision and new mountain-building in the Neogene. The Mont Terri geology bears witness to the same suite of events as the Alps; tectonically speaking, Mont Terri is part of the Alps. Africa continues to push Apulia against the larger European plate and the question arises as to what the geological future has in store for our hills and mountains. Recent GPS (Global Positioning System) data Iead to believe that it will be just erosion and decay

  11. HDPE/clay hybrids: the effect of clay modified with poly(diphenyl siloxanes) on thermal and rheological properties

    Energy Technology Data Exchange (ETDEWEB)

    Monasterio, Fernanda E.; Carrera, Maria C.; Erdmann, Eleonora; Destefanis, Hugo A., E-mail: ferelenakq@gmail.co [Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Buenos Aires (Argentina). Inst. de Investigaciones para la Industria Quimica; Pita, Victor J.R.R.; Dias, Marcos L. [Universidade Federal do Rio de Janeiro (IMA/UFRJ), RJ (Brazil). Inst. de Macromoleculas Profa. Eloisa Mano

    2009-07-01

    Poly(diphenyl siloxanes) (PDPhS) were synthesized in presence of organophilic clay in order to modify its nano structure. Two silane monomers were used: dimethoxydiphenylsilane and dichlorodiphenylsilane. The following characterizations were performed for all clays: XRD, FTIR and TGA/DTG. These siloxane-modified clays were more hydrophobic and had enhanced thermal stability. Solvent extraction was carried out in the siloxane-modified clays and the PDPhS soluble fraction analyzed according the molecular weight via GPC. The presence of free and grafted oligomers on clay surface was identified. The modified clays were added to HDPE by melt processing to obtain HDPE/clay hybrids which exhibited marked differences in the rheological behavior when compared with neat HDPE. (author)

  12. HDPE/clay hybrids: the effect of clay modified with poly(diphenyl siloxanes) on thermal and rheological properties

    International Nuclear Information System (INIS)

    Monasterio, Fernanda E.; Carrera, Maria C.; Erdmann, Eleonora; Destefanis, Hugo A.; Pita, Victor J.R.R.; Dias, Marcos L.

    2009-01-01

    Poly(diphenyl siloxanes) (PDPhS) were synthesized in presence of organophilic clay in order to modify its nano structure. Two silane monomers were used: dimethoxydiphenylsilane and dichlorodiphenylsilane. The following characterizations were performed for all clays: XRD, FTIR and TGA/DTG. These siloxane-modified clays were more hydrophobic and had enhanced thermal stability. Solvent extraction was carried out in the siloxane-modified clays and the PDPhS soluble fraction analyzed according the molecular weight via GPC. The presence of free and grafted oligomers on clay surface was identified. The modified clays were added to HDPE by melt processing to obtain HDPE/clay hybrids which exhibited marked differences in the rheological behavior when compared with neat HDPE. (author)

  13. Crystallite size distribution of clay minerals from selected Serbian clay deposits

    Directory of Open Access Journals (Sweden)

    Simić Vladimir

    2006-01-01

    Full Text Available The BWA (Bertaut-Warren-Averbach technique for the measurement of the mean crystallite thickness and thickness distributions of phyllosilicates was applied to a set of kaolin and bentonite minerals. Six samples of kaolinitic clays, one sample of halloysite, and five bentonite samples from selected Serbian deposits were analyzed. These clays are of sedimentary volcano-sedimentary (diagenetic, and hydrothermal origin. Two different types of shape of thickness distribution were found - lognormal, typical for bentonite and halloysite, and polymodal, typical for kaolinite. The mean crystallite thickness (T BWA seams to be influenced by the genetic type of the clay sample.

  14. Aspects of clay/concrete interactions

    International Nuclear Information System (INIS)

    Oscarson, D.W.; Dixon, D.A.; Onofrei, M.

    1997-01-01

    In the Canadian concept for nuclear fuel waste management, both clay-based materials and concrete are proposed for use as barriers, seals or supporting structures. The main concern when clays and concrete are in proximity is the generation of a high-pH environment by concrete since clay minerals are relatively unstable at high pH. Here we examine the OH - -generating capacity of two high-performance concretes when in contact with several solutions. We also investigate various aspects of claylconcrete interactions. They are: (1) the alkalimetric titration of clay suspensions, (2) the effect of Ca(OH) 2 (portlandite) on the swelling and hydraulic properties of compacted bentonite, and (3) the influence of cement grout on a backfill clay retrieved from the 900-d Buffer/Container Experiment at the Underground Research Laboratory of AECL. The results indicate that although high-performance concretes establish significantly lower poresolution pH (9 to 10) than does ordinary portland cement, the pH is still somewhat higher than that of clay/groundwater systems of about pH 8. Hence, even if high-performance concrete is used in a disposal vault, the potential still exists for clay minerals to alter over long periods of time if in contact with this concrete. The data show, however, that clays have a substantial buffering capacity, and clay-based barriers can thus neutralize much of the OH - potentially released from concrete in a vault. Moreover, even after reacting for 120 d at 85 o C with up to 5 wt.% Ca(OH) 2 , compacted bentonite (dry density = 1.2 Mg/m 3 ) retains much of its swelling capacity and has a permeability low enough (hydraulic conductivity ≤ 10 -11 m/s) to ensure that molecular diffusion will be the main transport mechanism through compacted clay-based barriers. Furthermore, according to X-ray diffractometry, the clay mineral component of backfill was not altered by contact with a cement grout for 900 d in the Buffer/Container Experiment

  15. Physical Properties of Latvian Clays

    OpenAIRE

    Jurgelāne, I; Stepanova, V; Ločs, J; Mālers, J; Bērziņa-Cimdiņa, L

    2012-01-01

    Physical and chemical properties of clays mostly depends on its mineral and chemical composition, particle size and pH value. The mutual influence of these parameters is complex. Illite is the most abundant clay mineral in Latvia and usually used in building materials and pottery. The viscosity and plasticity of Latvian clays from several deposits were investigated and correlated with mineral composition, particle size and pH value. Fractionated and crude clay samples were used. The p...

  16. Enchanted Clays: 44th Annual Meeting of the Clay Minerals Society (June 2007)

    Energy Technology Data Exchange (ETDEWEB)

    Randall T. Cygan

    2007-06-01

    “Enchanted Clays: 44th Annual Meeting of the Clay Minerals Society” was held in early June 2007 in beautiful and historic Santa Fe, New Mexico, USA. Santa Fe provided an idyllic location in the southwestern United States for the attendees to enjoy technical and social sessions while soaking up the diverse culture and wonderful climate of New Mexico—The Land of Enchantment. The meeting included a large and varied group of scientists, sharing knowledge and ideas, benefitting from technical interactions, and enjoying the wonderful historic and enchanted environs of Santa Fe. Including significant number of international scientists, the meeting was attended by approximately two hundred participants. The meeting included three days of technical sessions (oral and poster presentations), three days of field trips to clay and geological sites of northern New Mexico, and a full day workshop on the stabilization of carbon by clays. Details can be found at the meeting web site: www.sandia.gov/clay.

  17. Evaluation of the bleaching flux in clays containing hematite and different clay minerals

    International Nuclear Information System (INIS)

    Silva Junior, E.M.; Lusa, T.; Silva, T.M.; Medeiros, B.B.; Santos, G.R. dos; Morelli, M.R.

    2016-01-01

    Previous studies have shown that the addition of a synthetic flux in a clay mineral constituted by illite phase in the presence of iron oxide with the hematite, promotes color change of the firing products, making the reddish color firing into whiteness. This flow is constituted of a vitreous phase of the silicates family obtained by fusion/solidification of oxides and carbonates. Thus, the objective of this work was that of studying the interaction of the iron element in the final color mechanism of the different types of mineral crystal phase of the clays. In order to study the phenomenon, we obtained different compositions between the select clays and the synthetic flow, and characterization using X-ray diffraction (XRD) and visual analysis. The results showed that the action of the synthetic flow as a modifying agent for color depends on the mineral crystal phase of the clays. The color firing modification does not occur in the clays content high levels of kaolinite mineral phase. (author)

  18. Columns in Clay

    Science.gov (United States)

    Leenhouts, Robin

    2010-01-01

    This article describes a clay project for students studying Greece and Rome. It provides a wonderful way to learn slab construction techniques by making small clay column capitols. With this lesson, students learn architectural vocabulary and history, understand the importance of classical architectural forms and their influence on today's…

  19. Laboratory and field studies related to the Radionuclide Migration Project: Progress report, October 1, 1985-September 30, 1986

    International Nuclear Information System (INIS)

    Thompson, J.L.

    1987-08-01

    In this report we describe the work done at Los Alamos in support of the Radionuclide Migration project during fiscal year 1986. We have continued to monitor the transport of tritium and 85 Kr from the Cambric explosion zone to the satellite well, which is pumped at 600 gal/min. Corresponding movement of cationic radionuclides such as 137 Cs and 90 Sr has not yet been observed after 12 yr of pumping, nor have we seen evidence that these strongly sorbing ions move in conjunction with colloids. We have analyzed more data from the Cheshire study site but have not resolved the uncertainties regarding the distribution and movement of radioactive materials at this location. Our attempts to improve our analytical capability for 36 Cl and 99 Tc have resulted in some progress. Similarly, we have increased our understanding of radionuclide transport phenomena such as channeling in fracture flow and anion exclusion in zeolites and clays. A sample exchange with Lawrence Livermore National Laboratory has helped us identify critical steps in our procedures for collecting and analyzing large-volume water samples. We have surveyed potential sites on Pahute Mesa at the Nevada Test Site for future radionuclide migration studies and conclude that there are none other than Cheshire presently available, and none are likely to be created in the near future. The Laboratory has engaged recently in radionuclide migration studies sponsored by our weapons program; we reviewed this work in an appendix to the annual report

  20. Study of Cesium and Strontium sorption in Brazilian clays for their use as a barrier in repositories of radioactive wastes

    International Nuclear Information System (INIS)

    Freire, Carolina Braccini

    2007-01-01

    Wastes in general should be properly treated and stored. Then the radioactive wastes also require suitable and safe management beginning in their generation until the storage in repository. The main purpose of the radioactive waste management is to preserve the human beings and the environment. The objective of this research was to characterize some Brazilian clays in order to evaluate the viability of their use in the backfill layer, one of the radioactive waste repository barriers. The main function of this barrier is to contribute in the delay of the radionuclides movement, and to prevent their release into the environment. Four clays provided by national suppliers were selected for the research: Ca-Montmorillonite (Dol 01), Na-Montmorillonite (Dol 02), Kaolinite (Ind 01) and Vermiculite (Ubm 04). Their physical, chemical and mineralogical characteristics were determined, and also their sorption potential of Cesium and Strontium cations. It was confirmed through these results a direct relationship among their specific surface (SS), the capacity of cationic exchange (CCE) and pH. The CCE results followed this increasing order: Ind 01, Dol 01, and Dol 02. In accordance with the models of Freundlich (KJ) and Langmuir (M), the clays Dol 01 and Dol 02 were the best sorbers of Sr 2+ . The Ind 01 and Ubm 04 were the best ones in the case of Cs + . The Gibbs free energy change (ΔG deg) was calculated for the sorption reactions between the clays and the cations, and it was negative for all clays, confirming the sorption reaction spontaneity. (author)

  1. Effects of Different Types of Clays and Maleic Anhydride Modified Polystyrene on Polystyrene/Clay Nanocomposites

    Directory of Open Access Journals (Sweden)

    M. Mehrabzadeh

    2013-01-01

    Full Text Available Polymer/clay nanocomposites are considered as a new subject of research in Iran and the world. Addition of a minimum amount of clay (2-5wt% can improve the mechanical properties, enhance barrier properties and reduce flammability dramatically. Polystyrene (PS exhibits high strength, high modulus and excellent dimensional stability, but it has poor ductility, elongation, and flexural modulus. By incorporating clay into polystyrene these properties can be improved. In this study preparation of polystyrene/clay nanocomposite, effects of different types of clays (Cloisite 10A andNanomer I.30TC and maleic anhydride modified polystyrene on mechanical properties of the prepared polystyrene/clay nanocomposites were evaluated. Samples were prepared by a twin screw extruder. Transmission electron microscopy (TEM and X-ray diffraction (XRD techniques were employed to evaluate the extent of intercalation and exfoliation of silicate layers in the nanocomposites. Mechanical tests show that by addition of clay and maleic anhydride modified polystyrene the flexural modulus (~30% and elongation-at-break (~40% of prepared nanocomposites have been improved. XRD and TEM results show that nanocomposite have an intercalated structure with ability to change to further exfoliation structure.

  2. Thixotropic Properties of Latvian Illite Containing Clays

    OpenAIRE

    Lakevičs, Vitālijs; Stepanova, Valentīna; Niedra, Santa; Dušenkova, Inga; Ruplis, Augusts

    2015-01-01

    Thixotropic properties of Latvian Devonian and Quaternary clays were studied. Dynamic viscosity of the water clay suspensions were measured with a rotating viscometer. Influence of concentration, pH and modifiers on the thixotropic clay properties was analyzed. It was found that Latvian clays have thixotropic properties. Stability of clay suspensions is described with the thixotropy hysteresis loop. Increasing the speed of the viscometer rotation, dynamic viscosity of the clay suspension decr...

  3. Clay exfoliation and polymer/clay aerogels by supercritical carbon dioxide

    Directory of Open Access Journals (Sweden)

    Simona eLongo

    2013-11-01

    Full Text Available Supercritical carbon dioxide (scCO2 treatments of a montmorillonite (MMT intercalated with ammonium cations bearing two long hydrocarbon tails (organo-modified MMT, OMMT led to OMMT exfoliation, with loss of the long-range order in the packing of the hydrocarbon tails and maintenance of the long-range order in the clay layers. The intercalated and the derived exfoliated OMMT have been deeply characterized, mainly by X-ray diffraction analyses. Monolithic composite aerogels, with large amounts of both intercalated and exfoliated OMMT and including the nanoporous-crystalline δ form of syndiotactic polystyrene (s-PS, have been prepared, by scCO2 extractions of s-PS-based gels. Also for high OMMT content, the gel and aerogel preparation procedures occur without re-aggregation of the exfoliated clay, which is instead observed for other kinds of polymer processing. Aerogels with the exfoliated OMMT have more even dispersion of the clay layers, higher elastic modulus and larger surface area than aerogels with the intercalated OMMT. Extremely light materials with relevant transport properties could be prepared. Moreover, s-PS-based aerogels with exfoliated OMMT could be helpful for the handling of exfoliated clay minerals.

  4. Natural sorbents as barriers against migration of radionuclides from radioactive waste repositories

    International Nuclear Information System (INIS)

    Stefanova, I.; Gradev, G.D.

    1993-01-01

    The sorption properties of Bulgarian inorganic sorbents - clinoptilolite, vermiculite, bentonite, glauconite, celadonite and loess, which can be used as buffer, backfill and sealing materials in radwaste repository are studied. Experimental data about sorption and desorption capacities, radiation and thermal stability of sorbents from different Bulgarian deposits are reported and compared. Clinoptilolite from Beli Plast and its sodium variety from Kostino and Moryantsi is recommended as a barrier against radionuclide migration from radwaste repository due to their high sorption capacity of 137 Ce, 90 Sr and 60 Co. The high selectivity of vermiculite for polyvalent ions ( 144 Ce, 59 Fe and 90 Sr) gives grounds to include the sorption on vermiculite as a second step in the ion exchange technology for low level laundry waste decontamination. Bentonite is studied as a proposed buffer, backfill and sealing material. Its selectivity for cesium is lower compared to those of clinoptilolite. Thus a tailored-made mixture of bentonite and clinoptilolite will act as a barrier against radionuclides in different oxidation state. Glauconite can be successfully used as a barrier against migration of 144 Ce, 90 Sr, 54 Mn and 65 Zn. Loess is also included in the study, as the Kozloduy NPP is sited on loess formation and it is a natural potential site for low and intermediate level waste burial. It is concludes that zeolites and clays of Bulgarian deposits can be used effectively against radionuclide migration from radioactive waste repositories. 59 refs., 5 tabs. (author)

  5. What makes a natural clay antibacterial?

    Science.gov (United States)

    Williams, Lynda B.; Metge, David W.; Eberl, Dennis D.; Harvey, Ronald W.; Turner, Amanda G.; Prapaipong, Panjai; Port-Peterson, Amisha T.

    2011-01-01

    Natural clays have been used in ancient and modern medicine, but the mechanism(s) that make certain clays lethal against bacterial pathogens has not been identified. We have compared the depositional environments, mineralogies, and chemistries of clays that exhibit antibacterial effects on a broad spectrum of human pathogens including antibiotic resistant strains. Natural antibacterial clays contain nanoscale (2+ solubility.

  6. Viscosity and Plasticity of Latvian Illite Clays

    OpenAIRE

    Jurgelāne, I; Vecstaudža, J; Stepanova, V; Mālers, J; Bērziņa-Cimdiņa, L

    2012-01-01

    Due to viscosity and plasticity, clays and clay minerals are used in civil engineering, pottery and also in cosmetics and medicine as thickening agents and emulsion and suspension stabilizers. The rheological properties of clay suspensions are complex. Mostly it is an interaction between mineral composition, clay particle size and pH value and also depends on clay minerals. Clay-water suspension is non-Newtonian fluid showing thixotropic and pseudoplastic properties. Results showed that plast...

  7. The geochemistry of radionuclides with long half-lives

    International Nuclear Information System (INIS)

    Skytte Jensen, B.

    1980-11-01

    The geochemical behaviour of the actinides and technetium is discussed on a thermocynamic basis. The compositions of ground water in deep underground formations are discussed. The components in ground water which may enhance migration by complexation are found to be primarily bicarbonate and carbonate ions; but organic acids, if present, may similarly enhance migration. Based on available data, stability diagrams for the transuranium elements from uranium to americium under diverse conditions have been calculated. The diagrams identify the dominant species in solution, and in an accompanying diagram iso-concentration curves have been calculated, which show that the actinides may be expected to be very slightly soluble under the conditions existing in deep geological formations. The same is found to be the case for technetium. The adsorption of selected radionuclides onto clay components from Danish soils is discussed, and recent experimental data are presented. (author)

  8. Water diffusion through compacted clays analyzed by neutron scattering and tracer experiments

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez Sanchez, F

    2007-11-15

    Clay minerals are aluminium phyllosilicates, mostly products of the chemical alteration and mechanical breakdown of igneous and metamorphic rocks. Their physical and chemical properties can be directly related to their layered, fine-grained (large surface area) structure. These properties such as large water retention, low hydraulic conductivity, heat resistance and ionic exchange capacities, make clays ideal for many different applications, e.g. as sealing material for the underground disposal of radioactive waste. The long-term disposal of radioactive waste in an underground geological repository is based on a multibarrier concept. In the barrier of highly compacted clay, water is intercalated and confined between the clay layers. The narrow pores are responsible that under natural hydraulic gradients, molecular diffusion through water is the dominant transport mechanism for released radionuclides. The properties of water at the water-clay interface differ from that of bulk water. Therefore, a good and deep understanding of the water structure and dynamics in compacted clay systems is fundamental. This knowledge is the base for the progressing research about transport of pollutants through the compacted clays and argillaceous rock of radioactive waste barriers. This study focusses on four different types of pure clays, two of them charged, namely montmorillonite and illite (both in a Na and Ca form), and two uncharged, namely kaolinite and pyrophyllite. Their structural differences result in a significantly different behaviour in contact with water. In case of montmorillonite, water is located in between particles and in the interlayer space. In illite, water is found only in between particles, because the interlayer surfaces are tightly linked by potassium cations. The layers of kaolinite and pyrophyllite are uncharged and, consequently, water is located only in between particles. The clay powders were compacted to reach a high bulk dry density of about 1.9 g

  9. Water diffusion through compacted clays analyzed by neutron scattering and tracer experiments

    International Nuclear Information System (INIS)

    Gonzalez Sanchez, F.

    2007-11-01

    Clay minerals are aluminium phyllosilicates, mostly products of the chemical alteration and mechanical breakdown of igneous and metamorphic rocks. Their physical and chemical properties can be directly related to their layered, fine-grained (large surface area) structure. These properties such as large water retention, low hydraulic conductivity, heat resistance and ionic exchange capacities, make clays ideal for many different applications, e.g. as sealing material for the underground disposal of radioactive waste. The long-term disposal of radioactive waste in an underground geological repository is based on a multibarrier concept. In the barrier of highly compacted clay, water is intercalated and confined between the clay layers. The narrow pores are responsible that under natural hydraulic gradients, molecular diffusion through water is the dominant transport mechanism for released radionuclides. The properties of water at the water-clay interface differ from that of bulk water. Therefore, a good and deep understanding of the water structure and dynamics in compacted clay systems is fundamental. This knowledge is the base for the progressing research about transport of pollutants through the compacted clays and argillaceous rock of radioactive waste barriers. This study focusses on four different types of pure clays, two of them charged, namely montmorillonite and illite (both in a Na and Ca form), and two uncharged, namely kaolinite and pyrophyllite. Their structural differences result in a significantly different behaviour in contact with water. In case of montmorillonite, water is located in between particles and in the interlayer space. In illite, water is found only in between particles, because the interlayer surfaces are tightly linked by potassium cations. The layers of kaolinite and pyrophyllite are uncharged and, consequently, water is located only in between particles. The clay powders were compacted to reach a high bulk dry density of about 1.9 g

  10. Speciation analysis of radionuclides

    International Nuclear Information System (INIS)

    Salbu, B.

    2010-01-01

    Full text: Naturally occurring and artificially produced radionuclides in the environment can be present in different physico-chemical forms (i. e. radionuclide species) varying in size (nominal molecular mass), charge properties and valence, oxidation state, structure and morphology, density, complexing ability etc. Low molecular mass (LMM) species are believed to be mobile and potentially bioavailable, while high molecular mass (HMM) species such as colloids, polymers, pseudocolloids and particles are considered inert. Due to time dependent transformation processes such as mobilization of radionuclide species from solid phases or interactions of mobile and reactive radionuclide species with components in soils and sediments, however, the original distribution of radionuclides deposited in ecosystems will change over time and influence the ecosystem behaviour. To assess the environmental impact from radionuclide contamination, information on radionuclide species deposited, interactions within affected ecosystems and the time-dependent distribution of radionuclide species influencing mobility and biological uptake is essential. The development of speciation techniques to characterize radionuclide species in waters, soils and sediments should therefore be essential for improving the prediction power of impact and risk assessment models. The present paper reviews fractionation techniques which should be utilised for radionuclide speciation purposes. (author)

  11. Clay Portrait Boxes

    Science.gov (United States)

    Wilbert, Nancy Corrigan

    2009-01-01

    In an attempt to incorporate sculptural elements into her ceramics program, the author decided to try direct plaster casting of the face to make a plaster mold for clay. In this article, the author shares an innovative ceramics lesson that teaches students in making plaster casts and casting the face in clay. This project gives students the…

  12. Clay matrix voltammetry

    International Nuclear Information System (INIS)

    Perdicakis, Michel

    2012-01-01

    Document available in extended abstract form only. In many countries, it is planned that the long life highly radioactive nuclear spent fuel will be stored in deep argillaceous rocks. The sites selected for this purpose are anoxic and satisfy several recommendations as mechanical stability, low permeability and low redox potential. Pyrite (FeS 2 ), iron(II) carbonate, iron(II) bearing clays and organic matter that are present in very small amounts (about 1% w:w) in soils play a major role in their reactivity and are considered today as responsible for the low redox potential values of these sites. In this communication, we describe an electrochemical technique derived from 'Salt matrix voltammetry' and allowing the almost in-situ voltammetric characterization of air-sensitive samples of soils after the only addition of the minimum humidity required for electrolytic conduction. Figure 1 shows the principle of the developed technique. It consists in the entrapment of the clay sample between a graphite working electrode and a silver counter/quasi-reference electrode. The sample was previously humidified by passing a water saturated inert gas through the electrochemical cell. The technique leads to well-defined voltammetric responses of the electro-active components of the clays. Figure 2 shows a typical voltammogram relative to a Callovo-Oxfordian argillite sample from Bure, the French place planned for the underground nuclear waste disposal. During the direct scan, one can clearly distinguish the anodic voltammetric signals for the oxidation of the iron (II) species associated with the clay and the oxidation of pyrite. The reverse scan displays a small cathodic signal for the reduction of iron (III) associated with the clay that demonstrates that the majority of the previously oxidized iron (II) species were transformed into iron (III) oxides reducible at lower potentials. When a second voltammetric cycle is performed, one can notice that the signal for iron (II

  13. Clays in natural and engineered barriers for radioactive waste confinement - 4. International meeting. Book of abstracts

    International Nuclear Information System (INIS)

    2010-01-01

    The 4. edition of the International Meeting 'Clays in Natural and Engineered Barriers for Radioactive Waste Confinement' took place at the 'Cite Internationale des Congres' of Nantes (France). Approximately 500 participants (from about 20 different countries) attended the meeting. All the abstracts (oral and poster sessions) are included in these proceedings. The purpose of this 4. international conference is to gather specialists in the different disciplines related to clays and clay minerals, with scientists from organisations engaged in radioactive waste disposal, in order to evaluate the progress of the research conducted in that field. Multidisciplinary approaches including geology, mineralogy, geochemistry, rheology, geomechanics of clays are required in order to provide a detailed characterisation of the geological host formations considered for the disposal of radioactive waste and to assess the behaviour of engineered and natural barriers when submitted to various types of perturbations induced by disposal facilities. The major objectives for the experimental programs are constituted by the performance evaluation for the natural barrier as well as the impact of repository-induced disturbances upon the confinement properties of clay-rich geological formations. This is being or will be conducted in underground research laboratories, for interpreting the subsequent scientific results, for modelling the long-term behaviour of radioactive waste repositories and for carrying out safety assessment exercises. This conference covers all the aspects of clay characterisation and behaviour relevant to the confinement of radionuclides in clay, considered at various time scales and locations, from the descriptions of basic phenomenological processes to the global understanding of the performance and safety at repository and geological scales. Most of the topics covered by the programme of the conference are in line with the general objectives

  14. On the use of the spectroscopic techniques to model the interactions between radionuclides and solid minerals

    Energy Technology Data Exchange (ETDEWEB)

    Simoni, E. [IPN, Paris XI University, 91406 Orsay (France)]. e-mail: simoni@ipno.in2p3.fr

    2004-07-01

    In order to determine the radionuclides sorption constants on solid natural minerals, both thermodynamic and structural investigations, using spectroscopic techniques, are presented. The natural clays, that could be used as engineering barrier in the nuclear waste geological repository, are rather complex minerals. Therefore, in order to understand how these natural materials retain the radionuclides, it is necessary first to perform these studies on simple substrates such as phosphates, oxides and silicates (as powder and single crystal as well) and then extrapolate the obtained results on the natural minerals. As examples, the main results on the sorption processes of the hexavalent uranium onto zircon (ZrSiO{sub 4}) and lanthanum phosphate (LaPO{sub 4}) are presented. The corresponding sorption curves are simulated using the results obtained with the following spectroscopic techniques: laser induced spectro fluorimetry, X-ray photoelectron spectroscopy (XP S), X-ray absorption spectroscopy (Exafs). Finally, the thermodynamic sorption constants are calculated. (Author)

  15. Clay Animals and Their Habitats

    Science.gov (United States)

    Adamson, Kay

    2010-01-01

    Creating clay animals and their habitats with second-grade students has long been one of the author's favorite classroom activities. Students love working with clay and they also enjoy drawing animal homes. In this article, the author describes how the students created a diorama instead of drawing their clay animal's habitat. This gave students…

  16. Surface modification of montmorillonite on surface Acid-base characteristics of clay and thermal stability of epoxy/clay nanocomposites.

    Science.gov (United States)

    Park, Soo-Jin; Seo, Dong-Il; Lee, Jae-Rock

    2002-07-01

    In this work, the effect of surface treatments on smectitic clay was investigated in surface energetics and thermal behaviors of epoxy/clay nanocomposites. The pH values, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR) were used to analyze the effect of cation exchange on clay surface and the exfoliation phenomenon of clay interlayer. The surface energetics of clay and thermal properties of epoxy/clay nanocomposites were investigated in contact angles and thermogravimetric analysis (TGA), respectively. From the experimental results, the surface modification of clay by dodecylammonium chloride led to the increases in both distance between silicate layers of about 8 A and surface acid values, as well as in the electron acceptor component (gamma(+)(s)) of surface free energy, resulting in improved interfacial adhesion between basic (or electron donor) epoxy resins and acidic (electron acceptor) clay interlayers. Also, the thermal stability of nanocomposites was highly superior to pure epoxy resin due to the presence of the well-dispersed clay nanolayer, which has a barrier property in a composite system.

  17. 21 CFR 186.1256 - Clay (kaolin).

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Clay (kaolin). 186.1256 Section 186.1256 Food and... Substances Affirmed as GRAS § 186.1256 Clay (kaolin). (a) Clay (kaolin) Al2O3.2SiO2.nH2O, Cas Reg. No. 1332-58-7) consists of hydrated aluminum silicate. The commercial products of clay (kaolin) contain...

  18. Quantitative radionuclide angiocardiography

    International Nuclear Information System (INIS)

    Scholz, P.M.; Rerych, S.K.; Moran, J.F.; Newman, G.E.; Douglas, J.M.; Sabiston, D.C. Jr.; Jones, R.H.

    1980-01-01

    This study introduces a new method for calculating actual left ventricular volumes and cardiac output from data recorded during a single transit of a radionuclide bolus through the heart, and describes in detail current radionuclide angiocardiography methodology. A group of 64 healthy adults with a wide age range were studied to define the normal range of hemodynamic parameters determined by the technique. Radionuclide angiocardiograms were performed in patients undergoing cardiac catherization to validate the measurements. In 33 patients studied by both techniques on the same day, a close correlation was documented for measurement of ejection fraction and end-diastolic volume. To validate the method of volumetric cardiac output calcuation, 33 simultaneous radionuclide and indocyanine green dye determinations of cardiac output were performed in 18 normal young adults. These independent comparisons of radionuclide measurements with two separate methods document that initial transit radionuclide angiocardiography accurately assesses left ventricular function

  19. Quantifying the effect of squirt flow dispersion from compliant clay porosity in clay bearing sandstones

    DEFF Research Database (Denmark)

    Sørensen, Morten Kanne; Fabricius, Ida Lykke

    2013-01-01

    Compliant porosity in the form of cracks is known to cause significant attenuation and velocity dispersion through pore pressure gradients and consequent relaxation, dubbed squirt flow. Squirt flow from cracks vanish at high confining stress due to crack closing. Studies on clay bearing sandstones......-squirt flow on the bulk modulus of a clay bearing sandstone. The predicted magnitude of the clay-squirt effect on the bulk modulus is compared with experimental data. The clay-squirt effect is found to possibly account for a significant portion of the deviances from Gassmann fluid substitution in claybearing...... sandstones....

  20. Heavy metals and their radionuclides uptake by Bacillus Licheniformis

    International Nuclear Information System (INIS)

    Ramadan, A.A.; Ahmed, M.M.; Abo-state, M.A.M.; Sarhan, M.; Faroqe, M.

    2007-01-01

    Bacillus licheniformis is a gram positive spore forming bacterium. Different concentrations of cobalt affected the ability of Co uptake and growth of Bacillus licheniformis. As the concentration increased, both the uptake and growth were decreased. Maximum Co uptake was found at ph 7.0, while for growth was ph 8.0. The optimum temperature for uptake and growth was 40 degree C and 20% inoculum size represents the maximum cobalt uptake by Bacillus licheniformis. Also, maximum uptake was recorded after 72 hours, incubation period. As the concentration of cesium was increased till 400 mg/l, the uptake was also increased. The optimum cesium uptake and growth was at ph 8.0. The optimum growth was at 45 degree C while Cs uptake was found at 35 degree C and 15% inoculum size represented the maximum Cs uptake. After 72 hour incubation period, maximum Cs uptake was recorded. Generally, Bacillus licheniformis removed more than 80% of Co and 50% of Cs from the broth medium. Addition of clay to Bacillus licheniformis increased both Co or Cs uptake. Bacillus licheniformis was gamma resistant and 10 KGy reduced the viability by 5.3 log cycles. The irradiated and non-irradiated cultures can grow on 500 or 700 mg Co or Cs. Bacillus licheniformis removed 99.32% of the Co radionuclides and 99.28% of Cs radionuclides

  1. Zinc adsorption on clays inferred from atomistic simulations and EXAFS spectroscopy

    International Nuclear Information System (INIS)

    Churakov, S.V.; Daehn, R.

    2012-01-01

    Document available in extended abstract form only. Clay minerals such as illite and montmorillonite are ubiquitous in the environment. Because of their large specific area and high structural charge, they control the migration of heavy metals in the geosphere via different uptake mechanisms. The main processes for the sequestration of trace concentrations of heavy metals are sorption to clay edge sites and incorporation into clay structures. Whereas, sorption is a fast process occurring nearly instantaneously, the incorporation of metal ions into clay minerals occurs over geological time scales. Zn is a divalent transition metal, which shows similar chemical behavior to Ni and Co and can thus also be considered as a natural analogue for radioactive Ni and Co arising from nuclear fuel and radioactive waste from the decommissioning of nuclear power plants. The release of radionuclides from a repository can be considerably retarded due to interactions with clay minerals. For example, bentonite containing >70 wt% di-octahedral alumino-silicate clays is foreseen as a backfill material in the Swiss concept for a high level radioactive waste repository (NAGRA, 2002). Knowing the uptake mechanism of these elements on clays can help to protect the natural environment. In this study ab initio molecular dynamics (MD) calculations were applied to simulate the molecular mechanism of Zn uptake on the edge surfaces of montmorillonite, a di-octahedral clay, and to explain the measured K-edge extended X-ray absorption fine structure (EXAFS) spectra of Zn adsorbed on montmorillonite at different loadings. Two different montmorillonites were chosen for the experimental part of this study: Milos (Island of Milos, Greece) and STx-1 (Gonzales County, Texas, USA) (VANTELON et al., 2003). As a reference for Zn substituted for Al in the clay octahedral sheet a MILOS sample was prepared without adding any Zn. Milos was chosen because it contains 1.8 [mmol/kg] Zn incorporated into the

  2. Mineral acquisition from clay by budongo forest chimpanzees

    NARCIS (Netherlands)

    Reynolds, Vernon; Lloyd, Andrew W.; English, Christopher J.; Lyons, Peter; Dodd, Howard; Hobaiter, Catherine; Newton-Fisher, Nicholas; Mullins, Caroline; Lamon, Noemie; Schel, Anne Marijke; Fallon, Brittany

    2015-01-01

    Chimpanzees of the Sonso community, Budongo Forest, Uganda were observed eating clay and drinking clay-water from waterholes. We show that clay, clay-rich water, and clay obtained with leaf sponges, provide a range of minerals in different concentrations. The presence of aluminium in the clay

  3. Implications of sedimentological and hydrological processes on the distribution of radionuclides: the example of a salt marsh near Ravenglass, Cumbria

    International Nuclear Information System (INIS)

    Carr, A.P.; Blackley, M.W.L.

    1986-01-01

    This paper summarizes sedimentological and hydrological studies at a salt marsh site on the north bank of the River Esk near Ravenglass which have a bearing on the fate of the low-level radioactive effluent from the reprocessing facility at Sellafield, Cumbria. A range of techniques has been used including electromagnetic distance measurement (EDM) and pore water pressure studies. The results show that: (a) Over a two-year period there were no significant net changes in salt marsh creek level, although shorter-term (probably seasonal) fluctuations, of the order of 2 cm, occurred. These were attributed to expansion of clay particles during the winter months. Nearby, however, there were vertical changes of the order of 1 m due to erosion. (b) Pore water pressures indicated a dynamic situation with very rapid responses both to tidal fluctuations and to rainfall. During neap tides there was clear evidence for water seeping upwards from the underlying clay/sand interface. Shortlived radionuclides ( 95 Zr/ 95 Nb and 106 Ru) were detected in this zone. (c) soil polygons, once initiated by desiccation, thereafter provide preferential routes for water (and radionuclides) to the sub-surface sediment. These, and other results, are discussed in the context of previous studies. It is concluded that the complexity of the estuarine environment results in most data being site specific. (author)

  4. Evaluation of kaolinite clays of Moa for the production of cement based clinker-calcined clay-limestone (LC3

    Directory of Open Access Journals (Sweden)

    Roger S. Almenares-Reyes

    2016-12-01

    Full Text Available Clay materials from two outcrops of the Moa region were analyzed to determine their potential use as supplementary cementitious material in the production of ternary cements based on limestone-calcined clay. The clays were characterized by atomic absorption spectroscopy (EAA, X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FTIR and thermogravimetric analysis (ATG. These methods revealed high aluminum in clays, moderate kaolinite content, a disordered structure and the presence of impurities. The solubility of aluminum and silicon in alkali and the compressive strength of LC3 systems is proportional to their content in clay, being higher for the one with higher kaolinite content and greater structural disorder (outcrop D1, although the clay of both outcrops may constitute supplementary cementitious materials in the production of ternary cements based clinker-calcined clay-limestone. The suitable thermal activation range for both clays is between 650 ° C and 850 ° C.

  5. Influence of herbicide structure, clay acidity, and humic acid coating on acetanilide herbicide adsorption on homoionic clays.

    Science.gov (United States)

    Liu, Weiping; Gan, Jianying; Yates, Scott R

    2002-07-03

    Adsorption of chloroacetanilide herbicides on homoionic montmorillonite was studied by coupling batch equilibration and FT-IR analysis. Adsorption decreased in the order metolachlor > acetochlor > alachlor > propachlor on Ca(2+)- or Mg(2+)-saturated clays and in the order metolachlor > alachlor > acetachlor > propachlor on Al(3+)- or Fe(3+)-saturated clays. FT-IR spectra showed that the carbonyl group of the herbicide molecule was involved in bonding. For the same herbicide, adsorption of alachlor, acetachlor, and metolachlor on clay followed the order Ca(2+) approximately Mg(2+) < Al(3+) < or = Fe(3+), which coincided with the increasing acidity of homoionic clays. Adsorption of propachlor, however, showed an opposite dependence, suggesting a different governing interaction. In clay and humic acid mixtures, herbicide adsorption was less than that expected from independent additive adsorption by the individual constituents, and the deviation was dependent on the clay-to-humic acid ratio, with the greatest deviation consistently occurring at a 60:40 clay-to-humic acid ratio.

  6. The migration of the radionuclide 3 H in unsaturated soil from the disposal in the final repository for low and medium active waste in Saligny area

    International Nuclear Information System (INIS)

    Toma, A.D.

    2002-01-01

    The functioning of the Cernavoda Nuclear Power Plant will generate low and medium active waste which will be contaminated with long-life fission products (U, Pu, Np, Am), radioactive carbon ( 14 C) and tritium ( 3 H), which through their radiochemical characteristics and their influence upon the environment and people, request special attention regarding their storage and disposal. Based on the geological and mineralogical research regarding the location of a repository for low and medium active waste, Saligny area near the Cernavoda Nuclear Power Plant was chosen. The repository will be located in loess, seated on sedimentary formations with insertions of clay patches. The main target of the research is to obtain some experimental data necessary for the evaluation of the migration of the radionuclide 3 H (resulting from Cernavoda Nuclear Power Plant) in unsaturated soils in Saligny area. From the analysis of the test data obtained in the laboratory for the determination of the migration parameters of the radionuclide 3 H in the material of the geological formation of Saligny area it results that there is a direct correlation between the values of these parameters and the basic mineralogical component - clay - of the soil sample. (authors)

  7. Redox properties of iron-bearing clays and MX-80 bentonite – Electrochemical and spectroscopic characterization

    International Nuclear Information System (INIS)

    Hofstetter, Th. B.; Sosedova, Y.; Gorski, C.; Voegelin, A.; Sander, M.

    2014-03-01

    The characterization of the redox properties of Fe-bearing minerals in the presence and absence of dissolved Fe"2"+ is of major relevance for the assessment of redox reactions in natural and engineered environments such as radioactive waste repositories. In this study, we developed an electrochemical approach based on the use of soluble organic electron transfer mediators, which enabled us to quantify the redox properties of Fe-bearing clay minerals, MX- 80 bentonite and combinations of clay minerals, Fe oxides and dissolved Fe"2"+. Using mediated electrochemical oxidation and reduction, we quantified the electron accepting and donating capacities of ferrous smectite SWa-1, Wyoming montmorillonite SWy-2 and MX-80 bentonite at pH 7.5. All structural Fe in clay minerals was redox-active in contrast to that present in other, not further defined phases of MX-80. The materials investigated were redoxactive over a very wide range of Eh-values, that is the Fe"2"+/Fe_t_o_t_a_l ratio of the minerals changed from 0 to 100 % between +600 and -600 mV (vs. SHE). Redox properties were highly path-dependent due to structural changes of the minerals as revealed from the study of native and redox-cycled clay minerals after repeated reduction and re-oxidation cycles. Irreversible alteration of the mineral structure, however, was less obvious for materials with lower total Fe content such as MX-80 bentonite and SWy-2. Systems containing native montmorillonites (SWy-2 or MX-80), goethite and dissolved Fe"2"+ were also able to buffer the reduction potential E_H between 0 and -300 mV. Regardless of their Fe oxidation state, Fe-bearing minerals are redox-active over a wide potential range and therefore very relevant as redox buffers determining the fate of redox-active radionuclides and metals in waste repositories. (authors)

  8. Redox properties of iron-bearing clays and MX-80 bentonite – Electrochemical and spectroscopic characterization

    Energy Technology Data Exchange (ETDEWEB)

    Hofstetter, Th. B.; Sosedova, Y.; Gorski, C.; Voegelin, A.; Sander, M.

    2014-03-15

    The characterization of the redox properties of Fe-bearing minerals in the presence and absence of dissolved Fe{sup 2+} is of major relevance for the assessment of redox reactions in natural and engineered environments such as radioactive waste repositories. In this study, we developed an electrochemical approach based on the use of soluble organic electron transfer mediators, which enabled us to quantify the redox properties of Fe-bearing clay minerals, MX- 80 bentonite and combinations of clay minerals, Fe oxides and dissolved Fe{sup 2+}. Using mediated electrochemical oxidation and reduction, we quantified the electron accepting and donating capacities of ferrous smectite SWa-1, Wyoming montmorillonite SWy-2 and MX-80 bentonite at pH 7.5. All structural Fe in clay minerals was redox-active in contrast to that present in other, not further defined phases of MX-80. The materials investigated were redoxactive over a very wide range of Eh-values, that is the Fe{sup 2+}/Fe{sub total} ratio of the minerals changed from 0 to 100 % between +600 and -600 mV (vs. SHE). Redox properties were highly path-dependent due to structural changes of the minerals as revealed from the study of native and redox-cycled clay minerals after repeated reduction and re-oxidation cycles. Irreversible alteration of the mineral structure, however, was less obvious for materials with lower total Fe content such as MX-80 bentonite and SWy-2. Systems containing native montmorillonites (SWy-2 or MX-80), goethite and dissolved Fe{sup 2+} were also able to buffer the reduction potential E{sub H} between 0 and -300 mV. Regardless of their Fe oxidation state, Fe-bearing minerals are redox-active over a wide potential range and therefore very relevant as redox buffers determining the fate of redox-active radionuclides and metals in waste repositories. (authors)

  9. Fate and transport of radionuclides in soil-water environment. Review.

    Science.gov (United States)

    Konoplev, Aleksei

    2017-04-01

    The ease in which radionuclides move through the environment and are taken up by plants and animals is governed by their chemical forms and by site-specific environmental characteristics. The objective of this paper is to review basic mechanisms of the behavior of radiocesium and radiostrontium in the environment after the nuclear accident. Our understanding of radionuclide's speciation and migration processes seems to be adequate and explains similarities and differences of radiocesium (r-Cs) behavior in the environment after Fukushima and Chernobyl accidents. Climate and geographical conditions in Fukushima Prefecture of Japan and Chernobyl's near-field zone are obviously different. In particular, precipitation differs substantially, with the annual average for Fukushima being about 3 times higher than at Chernobyl. The landscapes and soils also differ significantly. What is more, the speciation of r-Cs in the releases was distinct (large fraction of radionuclides was deposited as fuel particles in 30-km zone around Chernobyl NPP, while in Fukushima radiocesium is mostly part of condensation particles including glassy hot particles). Radiocesium (r-Cs) in the environment is strongly bound to soil and sediment particles containing micaceous clay minerals (illite, vermiculite, etc.), which is associated with two basic processes - high selective reversible sorption and fixation. The r-Cs distribution coefficient Kd in Fukushima rivers was found to be 1-2 orders of magnitude higher than corresponding values for rivers and surface runoff of Chernobyl area. This is indicative of higher ability of Fukushima soils and sediments to bind r-Cs. Dissolved r-Cs wash-off for Fukushima river watersheds is essentially slower than those for Chernobyl. However, steeper slopes and higher precipitation in Fukushima area cause higher erosion and higher particulate r-Cs wash-off. For a comparable time after the accident the total r-Cs wash-off from contaminated catchments in Fukushima

  10. Mineralogy and geotechnical characteristics of some pottery clay

    Directory of Open Access Journals (Sweden)

    Mujib Olamide ADEAGBO

    2016-12-01

    Full Text Available The physical properties of soils, which are tremendously influenced by the active clay minerals in soil, are of great importance in geotechnical engineering. This paper investigates the clay-sized particles of the Igbara-Odo pottery clay, and compares results obtained with available data on the bulk sample, to determine their correlation and underline the dependence of the geotechnical properties of the bulk clay material on the clay-sized particles. The bulk clay sample consists of 52% sand-size particles, 21% silt and 27% clay. Analysis of the clay-sized particles and the bulk materials shows: specific gravity of 2.07 and 2.66, liquid limit of 91.0% and 33.0%, plastic limit of 27.5% and 14.3%, plasticity index of 63.5% and 18.7% and a linear shrinkage of 7.9% and 5.4%, for both clay-sized particles and bulk clay respectively. The activity value of the clay material (0.64 suggests the presence of Kaolinite and Ilite; and these were confirmed with X-Ray diffraction on the bulk sample and clay-sized particles. X-Ray diffraction patterns shows distinctive peaks which highlight the dominance of Kaolinite (with 8 peaks in the pottery clay sample for both clay-sized particles and bulk material; while traces of other clay minerals like Illite and Halloysite and rock minerals like Mica, Feldspar and Chrysotile were also found. These results suggest that the clay possesses high viability in the manufacturing of ceramics, refractory bricks, paper, fertilizer and paint. The clay material can be used as a subgrade in road construction, since it possesses low swelling characteristics.

  11. Xenon-129 NMR study of the microporous structure of clays and pillared clays

    International Nuclear Information System (INIS)

    Tsiao, C.; Carrado, K.A.

    1990-01-01

    129 Xe NMR studies have been carried out using xenon gas adsorbed in clays and pillared clays. Data from the measurements provide information on the pore structure of clays before and after pillaring. The results indicate that the effective pore diameter of montmorillonite increases, for example, from 5.4 Angstrom to 8.0 Angstrom after pillaring cheto-montmorillonite with aluminum polyoxohydroxy Keggin cations. The data are consistent with X-ray powder diffraction results, which show a corresponding increase in the interlamellar gallery height from 5.6 Angstrom to 8.4 Angstrom

  12. Performance assessment of geological isolation systems for radioactive waste. Disposal in clay formations

    International Nuclear Information System (INIS)

    Marivoet, J.; Bonne, A.

    1988-01-01

    In the framework of the PAGIS project of the CEC Research Programme on radioactive waste, performance assessment studies have been undertaken on the geological disposal of vitrified high-level waste in clay layers at a reference site at Mol (B) and a variant site at Harwell (UK). The calculations performed for the reference site shown that most radionuclides decay to negligible levels within the first meters of the clay barrier. The maximum dose rates arising from the geological disposal of HLW, as evaluated by the deterministic approach are about 10 -11 Sv/y for river pathways. If the sinking of a water well into the 150 m deep aquifer layer in the vicinity of the repository is considered together with a climatic change, the maximum calculated dose rate rises to a value of 3.10 -7 Sv/y. The calculated maxima arise between 1 million and 15 million years after disposal. The maximum dose rates evaluated by stochastic calculations are about one order of magnitude higher due to the considerable uncertainties in the model parameters. In the case of the Boom clay the estimated consequences of a fault scenario are of the same order of magnitude as the results obtained for the normal evolution scenario. The maximum risk is estimated from stochastic calculations to be about 4.10 -8 per year. For the variant site the case of the normal evolution scenario has been evaluated. The maximum dose rates calculated deterministically are about 1.10 -6 Sv/y for river pathways and 6.10 -5 Sv/y for a water well pathways; these doses would occur after about 1 million years. This document is one of a set of 5 reports covering a relevant project of the European Community on a nuclear safety subject having very wide interest. The five volumes are: the summary (EUR 11775-EN), the clay (EUR 11776-EN), the granite (EUR 11777-FR), the salt (EUR 11778-EN) and the sub-seabed (EUR 11779-EN)

  13. Wave liquefaction in soils with clay content

    DEFF Research Database (Denmark)

    Kirca, Özgür; Sumer, B. Mutlu; Fredsøe, Jørgen

    2012-01-01

    The paper presents the results of an experimental study of the influence of clay content (in silt-clay and sand-clay mixtures) on liquefaction beneath progressive waves. The experiments showed that the influence of clay content is very significant. Susceptibility of silt to liquefaction is increa...

  14. Radionuclide fixation mechanisms in rocks

    International Nuclear Information System (INIS)

    Nakashima, S.

    1991-01-01

    In the safety evaluation of the radioactive waste disposal in geological environment, the mass balance equation for radionuclide migration is given. The sorption of radionuclides by geological formations is conventionally represented by the retardation of the radionuclides as compared with water movement. In order to quantify the sorption of radionuclides by rocks and sediments, the distribution ratio is used. In order to study quantitatively the long term behavior of waste radionuclides in geological environment, besides the distribution ratio concept in short term, slower radionuclide retention reaction involving mineral transformation should be considered. The development of microspectroscopic method for long term reaction path modeling, the behavior of iron during granite and water interaction, the reduction precipitation of radionuclides, radionuclide migration pathways, and the representative scheme of radionuclide migration and fixation in rocks are discussed. (K.I.)

  15. Characterization of clay minerals

    International Nuclear Information System (INIS)

    Diaz N, C.; Olguin, M.T.; Solache R, M.; Alarcon H, T.; Aguilar E, A.

    2002-01-01

    The natural clays are the more abundant minerals on the crust. They are used for making diverse industrial products. Due to the adsorption and ion exchange properties of these, a great interest for developing research directed toward the use of natural clays for the waste water treatment has been aroused. As part of such researches it is very important to carry out previously the characterization of the interest materials. In this work the results of the mineral and elemental chemical composition are presented as well as the morphological characteristics of clay minerals from different regions of the Mexican Republic. (Author)

  16. The cleaning of the soils polluted by oil and radionuclides by natural sorbents

    International Nuclear Information System (INIS)

    Farajov, M.F.; Shamilov, E.N.; Abdullayev, A.S.; Huseynov, V.I.

    2005-01-01

    Full text : Problem of environmental pollution in oil extracting areas of Absheron peninsula became the very important discussion object lately. It this areas for many years oil and well waters were flowed to environmental areas caused a lot of pools in that areas and at the result the soil and plants were polluted with oil and radionuclides. By last years researches it was revealed that amount of radium 226 oil well water contains 10 - 500 Bq/l. Sometimes amount of radium 226 in polluted soils is increasing to 2000--5000 Bq/l and at the result it is raising probability of entering radionuclides by the way of migration from ground to plants into the nutrition chain cycle. Thus the polluted areas with oil and radionuclides and also when oil spills from oil-pipes by an accident the deactivation of soils is one of the main and most actual problems. In researches for cleaning of polluted soils with radionuclides for the first time were used the phyto sorbent modified breccias forms taken from Chaildag, Gobu, and Lokbatan mud volcano areas. The mineral contain of volcano mud generally consists of clay rocks -(kaolinit, montmorillonit, zeolite, chlorite, biotit) pyrite, and i.e.[2]. The polluted soil samples were taken in Surakhani region from area with the 150 mikroroentgen per hour radiation background. The contain and amount of radionuclides were determined with the radio spectrometer P rogress - Beta - Gamma . Polluted soil samples firstly are washed by hot water and HCl solution by mixing for 3-5 hours. At the next level by adding pieced sorbent into the solution is intensively mixing by mixer and putting for sedimentation for 24 hours. After sedimentation the stiring process is repeated by adding HCl on the sediment again. The soil is stirred by water for last time. Decomposed solutions from soil are adhering and are maked with sorbent again. Thus the soil is quite cleaned from oil and radionuclides by the sorbents we offer. At the same time this sorbents may be

  17. Clays and Clay Minerals and their environmental application in Food Technology

    Science.gov (United States)

    del Hoyo Martínez, Carmen; Cuéllar Antequera, Jorge; Sánchez Escribano, Vicente; Solange Lozano García, Marina; Cutillas Díez, Raul

    2013-04-01

    The clay materials have led to numerous applications in the field of public health (del Hoyo, 2007; Volzone, 2007) having been demonstrated its effectiveness as adsorbents of all contaminants. Some biodegradable materials are used for for adsorption of chemical contaminants: lignins (Valderrabano et al., 2008) and also clays and clay minerals, whose colloidal properties, ease of generating structural changes, abundance in nature, and low cost make them very suitable for this kind of applications. Among the strategies used at present to preserve the quality of the water and this way to diminish the environmental risk that supposes the chemical pollution, stands out the use of adsorbents of under cost, already they are natural or modified, to immobilize these compounds and to avoid the pollution of the water with the consequent reduction of environmental and economic costs Thanks to the development of the science and the technology of the nourishment in the last 50 years, there have revealed itself several new substances that can fulfill beneficial functions in the food, and these substances, named food additives, are today within reach of all. The food additives recover a very important role in the complex nourishing supply. The additives fulfill several useful functions in the food, which often we give for sat. Nevertheless the widespread use of food additives in the food production also influences the public health. The food industries, which are very important for the economy, spill residues proved from its activity that they have to be controlled to evaluate the environmental impact and to offer the necessary information about the quantitative evaluation of the chemical risk of the use of food additives for the public health. We have studied the adsorption of several contaminants by natural or modified clays, searching their interaction mechanisms and the possible recycling of these materials for environmental purposes and prevention of the health. References

  18. Marine biogeochemistry of radionuclides

    International Nuclear Information System (INIS)

    Fowler, S.W.

    1997-01-01

    Radionuclides entering the ocean from runoff, fallout, or deliberate release rapidly become involved in marine biogeochemical cycles. Sources, sinks and transport of radionuclides and analogue elements are discussed with emphasis placed on how these elements interact with marine organisms. Water, food and sediments are the source terms from which marine biota acquire radionuclides. Uptake from water occurs by surface adsorption, absorption across body surfaces, or a combination of both. Radionuclides ingested with food are either assimilated into tissue or excreted. The relative importance of the food and water pathway in uptake varies with the radionuclide and the conditions under which exposure occurs. Evidence suggests that, compared to the water and food pathways, bioavailability of sediment-bound radionuclides is low. Bioaccumulation processes are controlled by many environmental and intrinsic factors including exposure time, physical-chemical form of the radionuclide, salinity, temperature, competitive effects with other elements, organism size, physiology, life cycle and feeding habits. Once accumulated, radionuclides are transported actively by vertical and horizontal movements of organisms and passively by release of biogenic products, e.g., soluble excreta, feces, molts and eggs. Through feeding activities, particles containing radionuclides are ''packaged'' into larger aggregates which are redistributed upon release. Most radionuclides are not irreversibly bound to such particles but are remineralized as they sink and/or decompose. In the pelagic zones, sinking aggregates can further scavenge particle-reactive elements thus removing them from the surface layers and transporting them to depth. Evidence from both radiotracer experiments and in situ sediment trap studies is presented which illustrates the importance of biological scavenging in controlling the distribution of radionuclides in the water column. (author)

  19. Mineral Acquisition from Clay by Budongo Forest Chimpanzees.

    Directory of Open Access Journals (Sweden)

    Vernon Reynolds

    Full Text Available Chimpanzees of the Sonso community, Budongo Forest, Uganda were observed eating clay and drinking clay-water from waterholes. We show that clay, clay-rich water, and clay obtained with leaf sponges, provide a range of minerals in different concentrations. The presence of aluminium in the clay consumed indicates that it takes the form of kaolinite. We discuss the contribution of clay geophagy to the mineral intake of the Sonso chimpanzees and show that clay eaten using leaf sponges is particularly rich in minerals. We show that termite mound soil, also regularly consumed, is rich in minerals. We discuss the frequency of clay and termite soil geophagy in the context of the disappearance from Budongo Forest of a formerly rich source of minerals, the decaying pith of Raphia farinifera palms.

  20. Mineral Acquisition from Clay by Budongo Forest Chimpanzees.

    Science.gov (United States)

    Reynolds, Vernon; Lloyd, Andrew W; English, Christopher J; Lyons, Peter; Dodd, Howard; Hobaiter, Catherine; Newton-Fisher, Nicholas; Mullins, Caroline; Lamon, Noemie; Schel, Anne Marijke; Fallon, Brittany

    2015-01-01

    Chimpanzees of the Sonso community, Budongo Forest, Uganda were observed eating clay and drinking clay-water from waterholes. We show that clay, clay-rich water, and clay obtained with leaf sponges, provide a range of minerals in different concentrations. The presence of aluminium in the clay consumed indicates that it takes the form of kaolinite. We discuss the contribution of clay geophagy to the mineral intake of the Sonso chimpanzees and show that clay eaten using leaf sponges is particularly rich in minerals. We show that termite mound soil, also regularly consumed, is rich in minerals. We discuss the frequency of clay and termite soil geophagy in the context of the disappearance from Budongo Forest of a formerly rich source of minerals, the decaying pith of Raphia farinifera palms.

  1. Mineralogical and chemical characterization of various bentonite and smectite-rich clay materials Part A: Comparison and development of mineralogical characterization methods Part B: Mineralogical and chemical characterization of clay materials

    International Nuclear Information System (INIS)

    Kumpulainen, S.; Kiviranta, L.

    2010-06-01

    Mineralogy is an essential issue in understanding thermo-hydro-mechanical-chemical (THMC) behavior of bentonite materials. Mineralogy affects, among others, chemical composition of pore water, susceptibility for erosion, and transport of radionuclides. Consequently, mineralogy affects the designs of the buffer and backfill components. The objective of this work was to implement and develop mineralogical and chemical methods for characterization of reference clays considered for use as buffer and backfill materials in nuclear waste disposal. In this work, different methods were tested, compared, developed, and best available techniques selected. An additional aim was to characterize reference materials that are used in various nuclear waste disposal supporting studies, e.g., the SKB's alternative buffer material (ABM) experiment. Materials studied included three Wyoming-bentonites, two bentonites from Milos, four bentonites from Kutch district, and two Friedland clays. Minerals were identified using x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and polarizing microscopy. Mineralogical composition was estimated using Rietveld-analysis. Chemical methods were used to support and validate mineralogical interpretation. Total chemical composition was determined from decomposed samples using spectrometry (ICP-AES) and combustion (Leco-S, Leco-C). Ferric and ferrous iron species were distinguished titrimetrically and the amount of soluble sulphate was determined using ion chromatography. In addition, cation exchange capacity and original exchangeable cations were determined. Chemical composition of fine (<2 μ m) fractions and poorly crystalline Fe-, Al- and Si-phases determined by selective extractions were used in structural calculations of smectite. XRD is a basic method for all mineralogical characterization, but it is insensitive for detecting trace minerals and variations in the structural chemical composition of clay minerals. Polarizing

  2. Preparation of nanocomposites polyurethane water bone with clay montmorillonite sodica and organophilic clay

    International Nuclear Information System (INIS)

    Garcia, Claudia P.; Delpech, Marcia C.; Coutinho, Fernanda M.B.; Mello, Ivana L.

    2009-01-01

    Nanocomposites based on water bone polyurethane (NWPU's) were synthesized based on poli(propylene glycol), dimethylolpropionic acid (DMPA), isophorone diisocyanate (IPDI) and hydrazine (HYD), as chain extender. Two kinds of clays were employed: hydrophilic and organophilic. The nanocomposites were characterized by infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electronic microscopy (SEM) and the mechanical properties were evaluated. The FTIR results showed the presence of specific groups of clay and the XRD suggested that occurred their intercalation/exfoliation through polyurethane matrix. The mechanical resistance of the systems showed significant increase when compared to water dispersions synthesized without clay. (author)

  3. Safety- and performance indicators for a generic deep geological repository in clay

    International Nuclear Information System (INIS)

    Resele, G.; Niemeyer, M.; Wilhelm, St.; Heimer, St.; Mohlfeld, M.; Eilers, G.; Preuss, J.; Wollrath, J.

    2010-01-01

    Document available in extended abstract form only. As a first step of an impartial survey for an optimal site selection for a deep geological repository in Germany, potentially suitable regions shall be identified and localised according to their suitability. During the early phases of such a site selection procedure the information about the properties of the host rock and the geological situation at the potential sites is not very precise. As site investigation procedures are both expensive and time-consuming, it is essential to identify those properties of the geological barrier system that are most relevant for long-term safety. Furthermore, adequate indicators have to be chosen that allow a simple but efficient assessment of the suitability of the potential regions. Definition and application of 'exclusion criteria' based on single parameter values, e.g. the hydraulic conductivity of the host rock, is inadequate because the long-term safety depends on the interaction of many features and properties of the barrier system. In a research project, indicators have been developed which depend on the most relevant properties of the geological barriers and estimate the overall performance of a repository system. The application of these indicators on the barrier properties which have been found during the investigations of potential repository sites in clay located in Germany, Switzerland and France demonstrates how, for instance, an unfavourably high hydraulic permeability of the clay can be compensated by a large vertical extension of the clay layer and small hydraulic gradients. Other indicators evaluate the importance of hydraulic discontinuities and define the minimal requirements on technical barriers like seals and backfill of emplacement tunnels. When the information of the radionuclide inventory and the biosphere, especially the diluting aquifer is included, the indicators allow the estimation of the resulting dose which matches the result of a

  4. Proceedings of the international workshop on mechanistic understanding of radionuclide migration in compacted/intact systems

    International Nuclear Information System (INIS)

    Tachi, Yukio; Yui, Mikazu

    2010-03-01

    The international workshop on mechanistic understanding of radionuclide migration in compacted / intact systems was held at ENTRY, JAEA, Tokai on 21st - 23rd January, 2009. This workshop was hosted by Japan Atomic Energy Agency (JAEA) as part of the project on the mechanistic model/database development for radionuclide sorption and diffusion behavior in compacted / intact systems. The overall goal of the project is to develop the mechanistic model / database for a consistent understanding and prediction of migration parameters and its uncertainties for performance assessment of geological disposal of radioactive waste. The objective of the workshop is to integrate the state-of-the-art of mechanistic sorption and diffusion model in compacted / intact systems, especially in bentonite / clay systems, and discuss the JAEA's mechanistic approaches and future challenges, especially the following discussions points; 1) What's the status and difficulties for mechanistic model/database development? 2) What's the status and difficulties for applicability of mechanistic model to the compacted/intact system? 3) What's the status and difficulties for obtaining evidences for mechanistic model? 4) What's the status and difficulties for standardization of experimental methodology for batch sorption and diffusion? 5) What's the uncertainties of transport parameters in radionuclides migration analysis due to a lack of understanding/experimental methodologies, and how do we derive them? This report includes workshop program, overview and materials of each presentation, summary of discussions. (author)

  5. Radionuclide migration in clayrock host formations for deep geological disposal of radioactive waste: advances in process understanding and up-scaling methods resulting from the EC integrated project `Funmig

    Science.gov (United States)

    Altmann, S.; Tournassat, C.; Goutelard, F.; Parneix, J. C.; Gimmi, T.; Maes, N.

    2009-04-01

    One of the ‘pillars' supporting Safety Cases for deep geological disposal of radioactive waste in clayrock formations is the knowledge base regarding radionuclide (Rn) retention by sorption and diffusion-driven transport which is why the EC integrated project ‘Funmig' focused a major part of its effort on advancing understanding of these two macroscopic phenomena. This talk presents some of the main results of this four year effort (2005-2008). One of the keys to understanding diffusion-driven transport of anionic and cationic radionuclide species in clayrocks lies in a detailed understanding of the phenomena governing Rn total concentration and speciation (dissolved, adsorbed) in the different types of pore spaces present in highly-compacted masses of permanently charged clay minerals. Work carried out on a specifically synthesized montmorillonite (a model for the clay mineral fraction in clayrocks) led to development, and preliminary experimental validation, of a conceptually coherent set of theoretical models (molecular dynamics, electrostatic double layer, thermodynamic) describing dissolved ion and water solvent behavior in this material. This work, complemented by the existing state of the art, provides a sound theoretical basis for explaining such important phenomena as anion exclusion, cation exchange and the diffusion behavior of anions, weakly sorbing cations and water tracers. Concerning the behavior of strongly sorbing and/or redox-reactive radionuclides in clay systems, project research improved understanding of the nature of sorption reactions and sorbed species structure for key radioelements, or analogues (U, Se, Eu, Sm, Yb, Nd) on the basal surfaces and in the interlayers of synthetic or purified clay minerals. A probable mechanism for Se(IV) retention by reduction to Se° in Fe2+-containing clays was brought to light; this same process was also studied on the Callovo-Oxfordien clayrock targeted by the French radwaste management program. The

  6. Geochemical characterisation of kerogen from the Boom Clay Formation (Mol, Belgium) and evolution under different thermal stress

    International Nuclear Information System (INIS)

    Deniau, I.

    2002-12-01

    The Boom clay formation in Belgium has been chosen as test site for the disposal of high level radioactive wastes. The organic matter present in the clay (kerogen) is sensible to the thermal stress and can generate a huge number of gaseous and liquid compounds leading to local pH changes and to fracturing processes. In particular, some polar compounds can complex radionuclides. The samples analyzed in this work were taken in the underground laboratory of Mol at a 223 m depth. They have been analyzed in detail using geochemical methods (Rock-Eval pyrolysis, element analysis, transmission and scanning electron microscopy), spectroscopic methods (Fourier transformation infrared spectroscopy, solid state 13 C NMR, Raman) and pyrolytic methods (off-line, on-line and in sealed tubes combined with coupled CG/SM analyses). The study of a representative sample of this formation has permitted to characterize the organic matter at the molecular scale, to determine its fossilization mechanisms and the nature of the organic compounds trapped inside the kerogen. The organic matter of the Boom clays comes mainly from phyto-planktonic matter with an important contribution of terrestrial and bacterial matter. The degradation-recondensation played an important role in its preservation but the presence of numerous oxygenated molecules implies that oxidative incorporation also participated to this preservation. Finally, various products (hydrocarbons, oxygenated and nitrogenous polar compounds) trapped in significant amount inside the macro-molecular structure are released under a relatively weak thermal stress. Moreover several small polar organic molecules are released and can play a significant role in the retention or migration of radionuclides inside the geologic barrier. A sample submitted to a in-situ thermal stress of 80 deg. C during 5 years (Cerberus experiment) do not show any significant change in its kerogen structure with respect to the non-heated reference sample

  7. Crude oil polycyclic aromatic hydrocarbons removal via clay-microbe-oil interactions: Effect of acid activated clay minerals.

    Science.gov (United States)

    Ugochukwu, Uzochukwu C; Fialips, Claire I

    2017-07-01

    Acid treatment of clay minerals is known to modify their properties such as increase their surface area and surface acidity, making them suitable as catalysts in many chemical processes. However, the role of these surface properties during biodegradation processes of polycyclic aromatic hydrocarbons (PAHs) is only known for mild acid (0.5 M Hydrochloric acid) treated clays. Four different clay minerals were used for this study: a montmorillonite, a saponite, a palygorskite and a kaolinite. They were treated with 3 M hydrochloric acid to produce acid activated clay minerals. The role of the acid activated montmorillonite, saponite, palygorskite and kaolinite in comparison with the unmodified clay minerals in the removal of PAHs during biodegradation was investigated in microcosm experiments. The microcosm experiments contained micro-organisms, oil, and clays in aqueous medium with a hydrocarbon degrading microorganism community predominantly composed of Alcanivorax spp. Obtained results indicated that acid activated clays and unmodified kaolinite did not enhance the biodegradation of the PAHs whereas unmodified montmorillonite, palygorskite and saponite enhanced their biodegradation. In addition, unmodified palygorskite adsorbed the PAHs significantly due to its unique channel structure. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Microstructure and Thermal Properties of Polypropylene/Clay Nanocomposites with TiCl4/MgCl2/Clay Compound Catalyst

    Directory of Open Access Journals (Sweden)

    Limei Wang

    2015-01-01

    Full Text Available Polypropylene (PP/clay nanocomposites were synthesized by in situ intercalative polymerization with TiCl4/MgCl2/clay compound catalyst. Microstructure and thermal properties of PP/clay nanocomposites were studied in detail. Fourier transform infrared (FTIR spectra indicated that PP/clay nanocomposites were successfully prepared. Both wide-angle X-ray diffraction (XRD and transmission electron microscopy (TEM examination proved that clay layers are homogeneously distributed in PP matrix. XRD patterns also showed that the α phase was the dominate crystal phase of PP in the nanocomposites. Thermogravimetric analysis (TGA examinations confirmed that thermal stability of PP/clay nanocomposites was markedly superior to pure PP. Differential scanning calorimetry (DSC scans showed that the melt temperature and the crystallinity of nanocomposites were slightly lower than those of pure PP due to crystals imperfections.

  9. Investigation on long-term safety aspects of a radioactive waste repository in a diagenic clay formation. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Jobmann, M.; Gazul, R. [DBE Technology GmbH, Peine (Germany); Fluegge, J. [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) gGmbH, Braunschweig (Germany); and others

    2017-03-28

    The report presents the sealing concept developed for a Russian near surface low/intermediate level (LILW) waste repository at the ''radon site'' in the lower Cambrian ''blue clay'' formation. The radioactive wastes will be transported to the repository through a tunnel that will connect the underground disposal areas with the surface facilities. Two ventilation shafts for fresh and exhaust air will also connect the underground facilities with the surface. Specific characteristics of the flow regime in the studied area have been simulated. For the construction of a potential repository site it is necessary to know the possible contaminant transport paths to the surface and the biosphere. Due to the lack of sufficient data the calculation can only indicate tendencies that can trigger future explorations. Simulations of the radionuclide (C-14, Cl-36, Se-79, I-129) release from the repository in the liquid phase show a similar behavior as for other repositories in clay. Probabilistic simulations show a large variation of obtained results as a result of the parameter uncertainty.

  10. Environmental evolution records reflected by radionuclides in the sediment of coastal wetlands: A case study in the Yellow River Estuary wetland.

    Science.gov (United States)

    Wang, Qidong; Song, Jinming; Li, Xuegang; Yuan, Huamao; Li, Ning; Cao, Lei

    2016-10-01

    Vertical profiles of environmental radionuclides ( 210 Pb, 137 Cs, 238 U, 232 Th, 226 Ra and 4 0 K) in a sediment core (Y1) of the Yellow River Estuary wetland were investigated to assess whether environmental evolutions in the coastal wetland could be recorded by the distributions of radionuclides. Based on 210 Pb and 137 Cs dating, the average sedimentation rate of core Y1 was estimated to be 1.0 cm y -1 . Vertical distributions of natural radionuclides ( 238 U, 232 Th, 226 Ra and 40 K) changed dramatically, reflecting great changes in sediment input. Concentrations of 238 U, 232 Th, 226 Ra and 40 K all had significant positive relationships with organic matter and clay content, but their distributions were determined by different factors. Factor analysis showed that 238 U was determined by the river sediment input while 226 Ra was mainly affected by the seawater erosion. Environmental changes such as river channel migrations and sediment discharge variations could always cause changes in the concentrations of radionuclides. High concentrations of 238 U and 226 Ra were consistent with high accretion rate. Frequent seawater intrusion decreased the concentration of 226 Ra significantly. The value of 238 U/ 226 Ra tended to be higher when the sedimentation rate was low and tide intrusion was frequent. In summary, environmental evolutions in the estuary coastal wetland could be recorded by the vertical profiles of natural radionuclides. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Evaluation of the Equivalent Radium Activity of Clay Brickworks in Backlands of Paraiba, Brazil

    International Nuclear Information System (INIS)

    Nobrega de Araujo, E. E.; Araujo dos Santos Jr, J.; Andrade de Oliveira, I.; Santos Amaral, R. dos; Dias Bezerra, J.; Jimenez Charfuelan, J. M.; Araujo Costa, M. C.; Marques do Nacimento Santos, J.

    2015-01-01

    The natural radioactivity can reach high levels, depending on the geological formation of each area of the planet. Construction materials contain amounts of natural radioactive elements that may have concentrations upper of established limits, varying according to the composition of rock and soil from which they originated, causing greater exposure to human beings through the use of clay as raw material for ceramics used in construction. The radioecology dosimetry of these materials is defined in terms of the Equivalent Radium activity (Ra Eq ). In this context, this study aimed to establish the calculation of RaEq in the raw material of potteries in the badlands of Paraiba, area adjacent to the uranium deposits of Espinharas, to estimate the risks associated with primordial radionuclides attributed to TENORM activities from the extraction and use of clay in manufacture of bricks and tiles. Analysis were performed by high resolution gamma spectrometry with HPGe detector-Be, assuming the state of secular radioactive equilibrium. The results ranged from 84.49 to 747.78 Nq.kg -1 , with a mean 333.97 Bq.kg -1 . Some samples had values that exceeded the limit of 370 Bq.kg -1 established by UNSCEAR for construction materials, surpassing until on doubled, suggesting greater monitoring and control of these mining areas. (Author)

  12. Iodide Sorption to Clays and the Relationship to Surface Charge and Clay Texture - 12356

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Andrew; Kruichiak, Jessica; Tellez, Hernesto; Wang, Yifeng [Sandia National Laboratories, Albuquerque, NM 87185 (United States)

    2012-07-01

    Iodine is assumed to behave conservatively in clay barriers around nuclear waste repositories and in natural sediments. Batch experiments tend to show little to no sorption, while in column experiments iodine is often retarded relative to tritiated water. Current surface complexation theory cannot account for negatively charged ion sorption to a negatively charged clay particle. Surface protonation and iodide sorption to clay minerals were examined using surface titrations and batch sorption experiments with a suite of clay minerals. Surface titrations were completed spanning a range of both pH values and ionic strengths. For reference, similar titrations were performed on pure forms of an Al-O powder. The titration curves were deconvoluted to attain the pKa distribution for each material at each ionic strength. The pKa distribution for the Al-O shows two distinct peaks at 4.8 and 7.5, which are invariant with ionic strength. The pKa distribution of clays was highly variable between the different minerals and as a function of ionic strength. Iodide sorption experiments were completed at high solid:solution ratios to exacerbate sorption properties. Palygorskite and kaolinite had the highest amount of iodide sorption and montmorillonite had the least. (authors)

  13. Feasibility of using overburden clays for sealing purposes and laboratory testing of the clays

    Energy Technology Data Exchange (ETDEWEB)

    Mann, J. (Vyzkumny Ustav pro Hnede Uhli, Most (Czechoslovakia))

    1992-03-01

    Studies properties of overburden clay from North Bohemian surface coal mines for use as sealants of industrial and household waste that will be dumped at Czechoslovak surface mine sites. Basic requirements of sealing layers are optimum compressibility and impermeability by suitable compacting. Laboratory soil mechanical tests of different clay samples were carried out using the Proctor standard tests (PCS) and the Norwegian Geonor A/S - m 45 instrument. Laboratory tests were used to select the best available clay types with optimum density and moisture content. Experimental results of laboratory tests are provided.

  14. Radionuclide generators

    International Nuclear Information System (INIS)

    Lambrecht, R.M.; Wollongong Univ.; Tomiyoshi, K.; Sekine, T.

    1997-01-01

    The present status and future directions of research and development on radionuclide generator technology are reported. The recent interest to develop double-neutron capture reactions for production of in vivo generators; neutron rich nuclides for radio-immunotherapeutic pharmaceuticals: and advances with ultra-short lived generators is highlighted. Emphasis is focused on: production of the parent radionuclide; the selection and the evaluation of support materials and eluents with respect to the resultant radiochemical yield of the daughter, and the breakthrough of the radionuclide parent: and, the uses of radionuclide generators in radiopharmaceutical chemistry, biomedical and industrial applications. The 62 Zn → 62 Cu, 66 Ni → 66 Cu, 103m Rh → 103 Rh, 188 W → 188 Re and the 225 Ac → 221 Fr → 213 Bi generators are predicted to be emphasized for future development. Coverage of the 99 Mo → 99m Tc generator was excluded, as it the subject of another review. The literature search ended June, 1996. (orig.)

  15. Organophilization and characterization of commercial bentonite clays

    International Nuclear Information System (INIS)

    Cunha, B.B. da; Lima, J.C.C.; Alves, A.M.; Araujo, E.M.; Melo, T.J.A. de

    2012-01-01

    Bentonite clay is a plastic changes resulting from volcanic ash, consisting mostly of montmorillonite. The state of Paraiba is a major source of bentonite clay from Brazil, where the main oil fields are located in Boa Vista and represents the largest national production of raw and beneficiated bentonite. Aimed at the commercial value of this type of clay and its high applicability in the polls, this article aims to make a comparison between two kinds of clay, a national (Brasgel) and other imported (Cloisite) from organophilization of two commercial bentonite, ionic surfactant with Praepagem WB, and characterize them by XRD, FTIR and TG / DTG. We observe that despite getting inferior properties, the clay presents national values very similar to those presented by imported clay. (author)

  16. Thermal Behaviour of clay formations

    International Nuclear Information System (INIS)

    Tassoni, E.

    1985-01-01

    The programme carried out by ENEA to model the thermal-hydraulic-mechanical behaviour of the clay formations and to measure, in situ and in laboratory, the thermal properties of these rocks, is presented. An in situ heating experiment has been carried out in an open clay quarry in the area of Monterotondo, near Rome. The main goal of the experiment was to know the temperature field and the thermal effects caused by the high level radioactive waste disposed of in a clayey geological formation. The conclusions are as follows: - the thermal conduction codes are sufficiently accurate to forecast the temperature increases caused in the clay by the dissipation of the heat generated by high level radioactive waste; - the thermal conductivity deduced by means of the ''curve fitting'' method ranges from 0.015 to 0.017 W.cm -1 . 0 C -1 - the temperature variation associated with the transport of clay interstitial water caused by temperature gradient is negligible. A laboratory automated method has been designed to measure the thermal conductivity and diffusivity in clay samples. A review of experimental data concerning thermomechanical effects in rocks as well as results of thermal experiments performed at ISMES on clays are presented. Negative thermal dilation has been found both in the elastic and plastic range under constant stress. Thermoplastic deformation appears ten times greater than the thermoelastic one. A mathematical model is proposed in order to simulate the above and other effects that encompass thermal-elastic-plastic-pore water pressure response of clays at high temperature and effective pressure with undrained and transient drainage conditions. Implementation of the two versions into a finite element computer code is described

  17. Silt-clay aggregates on Mars

    International Nuclear Information System (INIS)

    Greeley, R.

    1979-01-01

    Viking observations suggest abundant silt and clay particles on Mars. It is proposed that some of these particles agglomerate to form sand size aggregates that are redeposited as sandlike features such as drifts and dunes. Although the binding for the aggregates could include salt cementation or other mechanisms, electrostatic bonding is considered to be a primary force holding the aggregates together. Various laboratory experiments conducted since the 19th century, and as reported here for simulated Martian conditions, show that both the magnitude and sign of electrical charges on windblown particles are functions of particle velocity, shape and composition, atmospheric pressure, atmospheric composition, and other factors. Electrical charges have been measured for saltating particles in the wind tunnel and in the field, on the surfaces of sand dunes, and within dust clouds on earth. Similar, and perhaps even greater, charges are proposed to occur on Mars, which could form aggregates of silt and clay size particles. Electrification is proposed to occur within Martian dust clouds, generating silt-clay aggregates which would settle to the surface where they may be deposited in the form of sandlike structures. By analog, silt-clay dunes are known in many parts of the earth where silt-clay aggregated were transported by saltation and deposited as 'sand.' In these structures the binding forces were later destroyed, and the particles reassumed the physical properties of silt and clay, but the sandlike bedding structure within the 'dunes' was preserved. The bedding observed in drifts at the Viking landing site is suggested to result from a similar process involving silt-clay aggregates on Mars

  18. What Makes a Natural Clay Antibacterial?

    Science.gov (United States)

    Williams, Lynda B.; Metge, David W.; Eberl, Dennis D.; Harvey, Ronald W.; Turner, Amanda G.; Prapaipong, Panjai; Poret-Peterson, Amisha T.

    2011-01-01

    Natural clays have been used in ancient and modern medicine, but the mechanism(s) that make certain clays lethal against bacterial pathogens has not been identified. We have compared the depositional environments, mineralogies, and chemistries of clays that exhibit antibacterial effects on a broad spectrum of human pathogens including antibiotic resistant strains. Natural antibacterial clays contain nanoscale (clay minerals in the bactericidal process is to buffer the aqueous pH and oxidation state to conditions that promote Fe2+ solubility. Chemical analyses of E. coli killed by aqueous leachates of an antibacterial clay show that intracellular concentrations of Fe and P are elevated relative to controls. Phosphorus uptake by the cells supports a regulatory role of polyphosphate or phospholipids in controlling Fe2+. Fenton reaction products can degrade critical cell components, but we deduce that extracellular processes do not cause cell death. Rather, Fe2+ overwhelms outer membrane regulatory proteins and is oxidized when it enters the cell, precipitating Fe3+ and producing lethal hydroxyl radicals. PMID:21413758

  19. External exposure doses due to gamma emitting natural radionuclides in some Egyptian building materials.

    Science.gov (United States)

    Moharram, B M; Suliman, M N; Zahran, N F; Shennawy, S E; El Sayed, A R

    2012-01-01

    Using of building materials containing naturally occurring radionuclides as (238)U, (232)Th and (40)K and their progeny results in an external exposures of the housing of such buildings. In the present study, indoor dose rates for typical Egyptian rooms are calculated using the analytical method and activity concentrations of natural radionuclides in some building materials. Uniform chemical composition of the walls, floor and ceiling as well as uniform mass concentrations of the radionuclides in walls, floor and ceiling assumed. Different room models are assumed to discuss variation of indoor dose rates according to variation in room construction. Activity concentrations of (238)U, (232)Th and (40)K content in eight samples representative Clay soil and different building materials used in most recent Egyptian building were measured using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The specific activity for (238)U, (232)Th and (40)K, from the selected samples, were in the range 14.15-60.64, 2.75-84.66 and 7.35-554.4Bqkg(-1), respectively. The average indoor absorbed dose rates in air ranged from 0.005μGyh(-1) to 0.071μGyh(-1) and the corresponding population-weighted annual effective dose due to external gamma radiation varies from 0.025 to 0.345mSv. An outdoor dose rate for typical building samples in addition to some radiological hazards has been introduced for comparison. Copyright © 2011 Elsevier Ltd. All rights reserved.

  20. Iodide uptake by negatively charged clay interlayers?

    International Nuclear Information System (INIS)

    Miller, Andrew; Kruichak, Jessica; Mills, Melissa; Wang, Yifeng

    2015-01-01

    Understanding iodide interactions with clay minerals is critical to quantifying risk associated with nuclear waste disposal. Current thought assumes that iodide does not interact directly with clay minerals due to electrical repulsion between the iodide and the negatively charged clay layers. However, a growing body of work indicates a weak interaction between iodide and clays. The goal of this contribution is to report a conceptual model for iodide interaction with clays by considering clay mineral structures and emergent behaviors of chemical species in confined spaces. To approach the problem, a suite of clay minerals was used with varying degrees of isomorphic substitution, chemical composition, and mineral structure. Iodide uptake experiments were completed with each of these minerals in a range of swamping electrolyte identities (NaCl, NaBr, KCl) and concentrations. Iodide uptake behaviors form distinct trends with cation exchange capacity and mineral structure. These trends change substantially with electrolyte composition and concentration, but do not appear to be affected by solution pH. The experimental results suggest that iodide may directly interact with clays by forming ion-pairs (e.g., NaI (aq) ) which may concentrate within the interlayer space as well as the thin areas surrounding the clay particle where water behavior is more structured relative to bulk water. Ion pairing and iodide concentration in these zones is probably driven by the reduced dielectric constant of water in confined space and by the relatively high polarizability of the iodide species. - Highlights: • Iodide sorption experiments were completed with a diverse array of clay minerals. • Iodide uptake trended with CEC and swamping electrolyte identity and concentration. • Results can be explained by considering the formation of ion pairs in clay interlayers