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Sample records for bentonite thermo-hydro-mechanical thm

  1. 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.)

  2. Mont Terri Project - Heater experiment : rock and bentonite thermo-hydro-mechanical (THM) processes in the near field of a thermal source for development of deep underground high level radioactive waste repositories

    Energy Technology Data Exchange (ETDEWEB)

    Goebel, I.; Alheid, H.-J.; Kaufhold, St.; Naumann, M.; Pletsch, Th.; Plischke, I.; Schnier, H.; Schuster, K.; Sprado, K. [Bundesanstalt fuer Geowissenschaften und Rohstoffe (BGR), Hannover (Germany); Meyer, T.; Miehe, R.; Wieczorek, K. [Gesellschaft fuer Anlagen und Reaktorsicherheit mbH (GRS), Braunschweig (Germany); Mayor, J.C. [Empresa Nacional de Residuos Radioactivos SA (ENRESA), Madrid (Spain); Garcia-Sineriz, J.; Rey, M. [Asociacion para la Investigacion y Desarollo Industrial de los Recursos Naturales (AITEMIN), Madrid (Spain); Alonso, E.; Lloret, A.; Munoz, J.J. [Centre Internacional de Metodos Numerics en Ingenyeria (CIMNE), Barcelona (Spain); Weber, H. [National Cooperative for the Disposal of Radioactive Waste (Nagra), Wettingen (Switzerland); Ploetze, M. [Eidgenoessische Technische Hochschule Zuerich, Institut fuer Geotechnik, Zuerich (Switzerland); Klubertanz, G. [Colenco Power Engineering Ltd, Baden (Switzerland); Ammon, Ch. [Rothpletz Lienhard und Cie AG, Aarau (Switzerland); Graf, A.; Nussbaum, Ch.; Zingg, A. [Goetechnical Institute Ltd, Saint-Ursanne (Switzerland); Bossart, P. [Federal Office of Topography (swisstopo), Wabern (Switzerland); Buehler, Ch.; Kech, M.; Trick, Th. [Solexperts AG, Moenchaltorf (Switzerland); Emmerich, K. [ITC-WGT, Karlsruhe (Germany); Fernandez, A. M. [Ciemat, Madrid (Spain)

    2007-07-01

    The long-term safety of underground permanent repositories for radioactive waste relies on a combination of several engineered and geological barriers. The interactions between a host rock formation of the type 'Opalinus Clay' and an engineered barrier of the type 'bentonite buffer' are observed in the Heater Experiment (HE) during a hydration and a heating phase. The objective of the experiment is an improved understanding of the coupled thermo-hydro-mechanical (THM) processes in a host rock-buffer system achieved by experimental observations as well as numerical modelling. The basic objectives are in detail: a) Long-term monitoring in the vicinity of the heater during hydration and heating; especially observation and study of coupled THM processes in the near field, i.e. continuous measurements of temperatures, pore pressures, displacements, electric conductivity, and analysis of the gases and water released into the rock by effect of heating; b) Determination of the properties of barrier and host rock done mainly by laboratory and in situ experiments, i.e. general mechanical and mineralogical properties, mechanical state in-situ, and changes induced by the experiment; c) Study of the interaction between host rock and bentonite buffer as well as validation and refinement of existing tools for modelling THM processes; d) Study of the behaviour and reliability of instrumentation and measuring techniques, i.e. inspection of sensors after dismantling the experimental setting. To achieve the objectives, 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 THM processes. Finally, the experiment was dismantled to provide laboratory specimens of post-heating buffer and host rock material. The continuous monitoring of the experiment by a multitude of sensors (for temperature, pore pressure, total pressure, relative

  3. 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)

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

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xuerui

    2016-10-06

    Clay formations are investigated worldwide as potential host rock for the deep geological disposal of high-level radioactive waste (HLW). Usually bentonite is preferred as the buffer and backfill material in the disposal system. In the disposal of HLW, heat emission is one of the most important issues as it can generate a series of complex thermo-hydro-mechanical (THM) processes in the surrounding materials and thus change the material properties. In the context of safety assessment, it is important to understand the thermally induced THM interactions and the associated change in material properties. In this work, the thermally induced coupled THM behaviours in the clay host rock and in the bentonite buffer as well as the corresponding coupling effects among the relevant material properties are numerically analysed. A coupled non-isothermal Richards flow mechanical model and a non-isothermal multiphase flow model were developed based on the scientific computer codes OpenGeoSys (OGS). Heat transfer in the porous media is governed by thermal conduction and advective flow of the pore fluids. Within the hydraulic processes, evaporation, vapour diffusion, and the unsaturated flow field are considered. Darcy's law is used to describe the advective flux of gas and liquid phases. The relative permeability of each phase is considered. The elastic deformation process is modelled by the generalized Hooke's law complemented with additional strain caused by swelling/shrinkage behaviour and by temperature change. In this study, special attention has been paid to the analysis of the thermally induced changes in material properties. The strong mechanical and hydraulic anisotropic properties of clay rock are described by a transversely isotropic mechanical model and by a transversely isotropic permeability tensor, respectively. The thermal anisotropy is described by adoption of the bedding-orientation-dependent thermal conductivity. The dependency of the thermal

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

    International Nuclear Information System (INIS)

    Wang, Xuerui

    2016-01-01

    Clay formations are investigated worldwide as potential host rock for the deep geological disposal of high-level radioactive waste (HLW). Usually bentonite is preferred as the buffer and backfill material in the disposal system. In the disposal of HLW, heat emission is one of the most important issues as it can generate a series of complex thermo-hydro-mechanical (THM) processes in the surrounding materials and thus change the material properties. In the context of safety assessment, it is important to understand the thermally induced THM interactions and the associated change in material properties. In this work, the thermally induced coupled THM behaviours in the clay host rock and in the bentonite buffer as well as the corresponding coupling effects among the relevant material properties are numerically analysed. A coupled non-isothermal Richards flow mechanical model and a non-isothermal multiphase flow model were developed based on the scientific computer codes OpenGeoSys (OGS). Heat transfer in the porous media is governed by thermal conduction and advective flow of the pore fluids. Within the hydraulic processes, evaporation, vapour diffusion, and the unsaturated flow field are considered. Darcy's law is used to describe the advective flux of gas and liquid phases. The relative permeability of each phase is considered. The elastic deformation process is modelled by the generalized Hooke's law complemented with additional strain caused by swelling/shrinkage behaviour and by temperature change. In this study, special attention has been paid to the analysis of the thermally induced changes in material properties. The strong mechanical and hydraulic anisotropic properties of clay rock are described by a transversely isotropic mechanical model and by a transversely isotropic permeability tensor, respectively. The thermal anisotropy is described by adoption of the bedding-orientation-dependent thermal conductivity. The dependency of the thermal

  6. FEBEX Full-Scalle Engineered Barriers Experiment in Crystalline Host Rock Preoperational Thermo-Hydro-Mechanical (THM) Modelling of the Mock Up Test

    International Nuclear Information System (INIS)

    1998-01-01

    The object of this report is to present and discuss the results of a series of 1-D and 2-D coupled thermo-hydro-mechanical (THM) and 2-D coupled thermo-hydro-mechanical (THM) analyses modelling the FEBEX mock-up test. The analyses have been carried out during the preoperational storage of the test and attempt to incorporate all available information obtained from laboratory characterisation work. The aim is not only to offer the best estimate of test performance using current models and information but also to provide a basis for future model improvements. Both the theoretical framework adopted in the analysis and the computer code employed are briefly described. The set of parameters used in the computation is then presented with particular reference to the source from which they have been derived. Initial and boundary condition are also defined. The results of a 1-D radially symmetric analysis are used to examine the basic patterns of thermal, hydraulic and mechanical behaviour of the test. A set of sensitivity analyses has been carried out in order to check the effects that the variation of a number of important parameters has on test results. Only in this way it is possible to acquire a proper understanding of the internal structure of the problem and of the interactions between the various phenomena occurring in the buffer. A better reproduction of the geometry of the test is achieved by means of a 2-D mesh representing and axisymmetric longitudinal section. Due to two-dimensional effects, the analyses carried out using this geometry exhibit some differences when compared with the results of the 1-D case, but the basic test behaviour is very similar. The test was started with an initial flooding stage with the purpose of closing the gaps between bentonite blocks. A limited number of compilations using recently developed joint elements have been performed to assess approximately the effect of this initial step on subsequent test behaviour. The analyses reported

  7. FEBEX Full-Scalle Engineered barriers experiment in crystalline host rock Preoperational thermo-hydro-mechanical (THM) modelling of the in situ test

    International Nuclear Information System (INIS)

    1998-01-01

    This report contains the results of a set of 1-D and 2-D coupled thermo-hydro-mechanical (THM) analyses carried out during the preoperational stage simulating the in situ FEBEX test. The analyses incorporate available information concerning rock and bentonite properties as well as the final test layout and conditions. The main goals are: -To provide the best estimate of test performance given current models and information - To define a basis for future model improvements. The theoretical bases of the analyses and the computer code used are reviewed. Special reference is made to the process of parameter estimation that tries to incorporate available information on material behaviour obtained in the characterisation work carried out both in the laboratory and in the field. Data obtained in the characterisation stage is also used to define initial and boundary conditions. The results of the 1-D THM Base Case analysis are used to gain a good understanding of expected test behaviour concerning thermal, hydraulic and mechanical problems. A quite extensive programme of sensitivity analyses is also reported in which the effect of a number of parameters and boundary conditions are examined. The results of the sensitivity analyses place an appropriate context the information obtained from the Base Case showing, for instance, that rock desaturation and degree of buffer hydration depend on some critical parameters in a complex way. Two-dimensional effects are discussed on the basis of the results of 2-D axisymmetric THM analysis performed using a longitudinal section that provides a better representation of real test geometry. Quantitative but not qualitative differences are found with respect to the 1-D results. Finally, a 2-D THM cross section analysis has been performed under plane strain conditions. No specific 2-D effects are observed in this case as quasi-axisymmetric conditions have been prescribed. The models employed in the analyses included in this report have not

  8. Thermo-Hydro-Mechanical Characterisation of the Bentonite of a Simulated HLW Repository after Five Years Operation ( In Situ Test of the FEBEX Project)

    Energy Technology Data Exchange (ETDEWEB)

    Villar, M. V.

    2004-07-01

    After five years of operation, heater 1 of the FEBEX experimental at the Grimsel Test Sites was switched off in February 2002. Following cooling of the system, the bentonite barrier was dismantled and the heater extracted. During dismantling many bentonite samples were taken. Several determinations were carried out in these samples with the aim of: (1) characterise the actual state of the bentonite and (2) determine the possible changes in its properties occurred during the experiment. The results of the thermo-hydro-mechanical characterisation performed at CIEMAT are reported and analysed. The distribution of water content and dry density of the bentonite in vertical sections presents axial symmetry. The construction gaps of the barrier have been filled by the expansion of the bentonite. The water retention capacity, the hydraulic conductivity and the swelling capacity of the samples from Grimsel have not irreversible changed. The pre consolidation pressure of the Grimsel samples has decreased due to the microstructural changes associated to the volume increase experienced during hydration. The thermal conductivity is higher for the bentonite blocks of the external ring of the barrier. (Author)

  9. Thermo-Hydro-Mechanical Characterisation of the Bentonite of a Simulated HLW Repository after Five Years Operation ( In Situ Test of the FEBEX Project)

    International Nuclear Information System (INIS)

    Villar, M. V.

    2004-01-01

    After five years of operation, heater 1 of the FEBEX experimental at the Grimsel Test Sites was switched off in February 2002. Following cooling of the system, the bentonite barrier was dismantled and the heater extracted. During dismantling many bentonite samples were taken. Several determinations were carried out in these samples with the aim of: (1) characterise the actual state of the bentonite and (2) determine the possible changes in its properties occurred during the experiment. The results of the thermo-hydro-mechanical characterisation performed at CIEMAT are reported and analysed. The distribution of water content and dry density of the bentonite in vertical sections presents axial symmetry. The construction gaps of the barrier have been filled by the expansion of the bentonite. The water retention capaciaty, the hydraulic conductivity and the swelling capacity of the samples from Grimsel have not irreversible changed. The preconsolidation pressure of the Grimsel samples has decreased due to the microstructural changes asswociated to the volume increase experienced during hydration. The thermal conductivity is higher for the bentonite blocks of the external ring of the barrier. (Author)

  10. OpenGeoSys: An open-source initiative for numerical simulation of thermo-hydro-mechanical/chemical (THM/C) processes in porous media

    DEFF Research Database (Denmark)

    Kolditz, O.; Bauer, S.; Bilke, L.

    In this paper we describe the OpenGeoSys (OGS) project, which is a scientific open-source initiative for numerical simulation of thermo-hydro-mechanical/chemical processes in porous media. The basic concept is to provide a flexible numerical framework (using primarily the Finite Element Method (FEM...

  11. Report on Thermo-Hydro-Mechanical Laboratory Tests Performed by CIEMAT on Febex Bentonite 2004-2008

    Energy Technology Data Exchange (ETDEWEB)

    Villar, M. V.; Gomez-Espina, R.

    2009-11-25

    The results of the laboratory studies performed by CIEMAT with the FEBEX bentonite in the context of WP3.2 of the NF-PRO Project and of the Agreement ENRESA-CIEMAT Anexo V are presented and analysed in this report. They refer to the effect of the hydraulic gradient on the permeability of bentonite, the effect of the thermal gradient on the hydration kinetics of bentonite, and the repercussion of temperature on the hydro-mechanical properties of bentonite (swelling, permeability and water retention capacity). In all the cases the bentonite has been used compacted to densities expected in the engineered barrier of a high-level radioactive waste repository. The existence of threshold and critical hydraulic gradients has been observed, both of them dependent on bentonite density and water pressures. After more than seven years of hydration, the 40-cm high bentonite columns are far from full saturation, the thermal gradient additionally delaying the process, which is very slow. Temperatures below 100 degree centigrade slightly decrease the swelling and the water retention capacity of the bentonite and increase its permeability. The information obtained improves the knowledge on the behaviour of expansive clay and will help the development of constitutive models and the interpretation of the results obtained in the mock-up and the in situ tests. (Author) 35 refs.

  12. Report on Thermo-Hydro-Mechanical Laboratory Tests Performed by CIEMAT on Febex Bentonite 2004-2008

    International Nuclear Information System (INIS)

    Villar, M. V.; Gomez-Espina, R.

    2009-01-01

    The results of the laboratory studies performed by CIEMAT with the FEBEX bentonite in the context of WP3.2 of the NF-PRO Project and of the Agreement ENRESA-CIEMAT Anexo V are presented and analysed in this report. They refer to the effect of the hydraulic gradient on the permeability of bentonite, the effect of the thermal gradient on the hydration kinetics of bentonite, and the repercussion of temperature on the hydro-mechanical properties of bentonite (swelling, permeability and water retention capacity). In all the cases the bentonite has been used compacted to densities expected in the engineered barrier of a high-level radioactive waste repository. The existence of threshold and critical hydraulic gradients has been observed, both of them dependent on bentonite density and water pressures. After more than seven years of hydration, the 40-cm high bentonite columns are far from full saturation, the thermal gradient additionally delaying the process, which is very slow. Temperatures below 100 degree centigrade slightly decrease the swelling and the water retention capacity of the bentonite and increase its permeability. The information obtained improves the knowledge on the behaviour of expansive clay and will help the development of constitutive models and the interpretation of the results obtained in the mock-up and the in situ tests. (Author) 35 refs

  13. Thermo-hydro-mechanical modelling of buffer, synthesis report

    International Nuclear Information System (INIS)

    Toprak, E.; Mokni, N.; Olivella, S.; Pintado, X.

    2013-08-01

    This study addresses analyses of coupled thermo-hydro-mechanical (THM) processes in a scheme considered for the spent nuclear fuel repository in Olkiluoto (Finland). The finite element code CODE B RIGHT is used to perform modelling calculations. The objective of the THM modelling was to study some fundamental design parameters. The time required to reach full saturation, the maximum temperature reached in the canister, the deformations in the buffer-backfill interface, the stress-deformation balance between the buffer and the backfill, the swelling pressure developed and the homogenization process development are critical variables. Because of the complexity of the THM processes developed, only a single deposition hole has been modelled with realistic boundary conditions which take into account the entire repository. A thermal calculation has been performed to adopt appropriate boundary conditions for a reduced domain. The modelling has been done under axisymmetric conditions. As a material model for the buffer bentonite and backfill soil, the Barcelona Basic Model (BBM) has been used. Simulation of laboratory tests conducted at B and Tech under supervision of Posiva has been carried out in order to determine the fundamental mechanical parameters for modelling the behaviour of MX-80 bentonite using the BBM model. The modelling process of the buffer-backfill interface is an essential part of tunnel backfill design. The calculations will aim to determine deformations in this intersection, the behaviour of which is important for the buffer swelling. The homogenization process is a key issue as well. Porosity evolution during the saturation process is evaluated in order to check if the final saturated density accomplishes the homogenization requirements. This report also describes the effect of the existence of an air-filled gap located between the canister and the bentonite block rings in thermo-hydro-mechanical behaviour of the future spent nuclear fuel repository in

  14. Thermo-hydro-mechanical modelling of buffer, synthesis report

    Energy Technology Data Exchange (ETDEWEB)

    Toprak, E.; Mokni, N.; Olivella, S. [Universitat Politecnica de Catalunya, Barcelona (Spain); Pintado, X. [B and Tech Oy, Helsinki (Finland)

    2013-08-15

    This study addresses analyses of coupled thermo-hydro-mechanical (THM) processes in a scheme considered for the spent nuclear fuel repository in Olkiluoto (Finland). The finite element code CODE{sub B}RIGHT is used to perform modelling calculations. The objective of the THM modelling was to study some fundamental design parameters. The time required to reach full saturation, the maximum temperature reached in the canister, the deformations in the buffer-backfill interface, the stress-deformation balance between the buffer and the backfill, the swelling pressure developed and the homogenization process development are critical variables. Because of the complexity of the THM processes developed, only a single deposition hole has been modelled with realistic boundary conditions which take into account the entire repository. A thermal calculation has been performed to adopt appropriate boundary conditions for a reduced domain. The modelling has been done under axisymmetric conditions. As a material model for the buffer bentonite and backfill soil, the Barcelona Basic Model (BBM) has been used. Simulation of laboratory tests conducted at B and Tech under supervision of Posiva has been carried out in order to determine the fundamental mechanical parameters for modelling the behaviour of MX-80 bentonite using the BBM model. The modelling process of the buffer-backfill interface is an essential part of tunnel backfill design. The calculations will aim to determine deformations in this intersection, the behaviour of which is important for the buffer swelling. The homogenization process is a key issue as well. Porosity evolution during the saturation process is evaluated in order to check if the final saturated density accomplishes the homogenization requirements. This report also describes the effect of the existence of an air-filled gap located between the canister and the bentonite block rings in thermo-hydro-mechanical behaviour of the future spent nuclear fuel

  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. Thermo-hydro-mechanical tests of buffer material

    Energy Technology Data Exchange (ETDEWEB)

    Pintado, X.; Hassan, Md. M.; Martikainen, J. [B and Tech Oy, Helsinki (Finland)

    2013-10-15

    MX-80 bentonite is the reference clay material for the buffer component planned to be used in the deep geological repository for the disposal of spent nuclear fuel in Finland. The buffer presents complex thermo-hydro-mechanical behavior which is modeled with different constitutive models for heat flow, water flow and stress-strain evolution in the buffer. Thermo, hydro and mechanical models need parameters to evaluate the THM-behavior. These modeling parameters were determined by performing series of laboratory experiments as follows: Water retention curve tests were performed on compacted bentonite samples, encompassing a range of initial dry density values from 1397 to 1718 kg/m{sup 3} as the initial water content was around of 5-8 %. The water retention curve was determined by imposing different suctions to the samples and the suctions were then checked using capacitive hygrometer and chilled mirror psychrometer. Oedometer tests were performed on compacted bentonite samples, encompassing a range of initial dry density values from 1590 to 1750 kg/m{sup 3} as the initial water content was around of 6 %. Samples were saturated with tap water, 35 or 70 g/L salt solutions. Infiltration tests were performed on compacted unsaturated bentonite samples, encompassing a range of initial dry density values from 1400 to 1720 kg/m{sup 3} as the initial water content was approximately between 4-7 %. Samples were saturated with tap water, 0.87, 35 or 70 g/L salt solutions. Tortuosity tests were performed on bentonite samples, encompassing a range of dry density values from 1460 to 1750 kg/m{sup 3} and the degree of saturation varied between 33-93 %. Thermal conductivity tests were performed on compacted bentonite samples, encompassing a range of dry density values from 1545 to 1715 kg/m{sup 3} and the degree of saturation varied between 31-88 %. The measurement was performed using a thermal needle probe. The general trend of all analyzed parameters was as expected when dry

  17. Thermo-hydro-mechanical tests of buffer material

    International Nuclear Information System (INIS)

    Pintado, X.; Hassan, Md. M.; Martikainen, J.

    2013-10-01

    MX-80 bentonite is the reference clay material for the buffer component planned to be used in the deep geological repository for the disposal of spent nuclear fuel in Finland. The buffer presents complex thermo-hydro-mechanical behavior which is modeled with different constitutive models for heat flow, water flow and stress-strain evolution in the buffer. Thermo, hydro and mechanical models need parameters to evaluate the THM-behavior. These modeling parameters were determined by performing series of laboratory experiments as follows: Water retention curve tests were performed on compacted bentonite samples, encompassing a range of initial dry density values from 1397 to 1718 kg/m 3 as the initial water content was around of 5-8 %. The water retention curve was determined by imposing different suctions to the samples and the suctions were then checked using capacitive hygrometer and chilled mirror psychrometer. Oedometer tests were performed on compacted bentonite samples, encompassing a range of initial dry density values from 1590 to 1750 kg/m 3 as the initial water content was around of 6 %. Samples were saturated with tap water, 35 or 70 g/L salt solutions. Infiltration tests were performed on compacted unsaturated bentonite samples, encompassing a range of initial dry density values from 1400 to 1720 kg/m 3 as the initial water content was approximately between 4-7 %. Samples were saturated with tap water, 0.87, 35 or 70 g/L salt solutions. Tortuosity tests were performed on bentonite samples, encompassing a range of dry density values from 1460 to 1750 kg/m 3 and the degree of saturation varied between 33-93 %. Thermal conductivity tests were performed on compacted bentonite samples, encompassing a range of dry density values from 1545 to 1715 kg/m 3 and the degree of saturation varied between 31-88 %. The measurement was performed using a thermal needle probe. The general trend of all analyzed parameters was as expected when dry density, water content, and

  18. Modeling of Coupled Thermo-Hydro-Mechanical-Chemical Processes for Bentonite in a Clay-rock Repository for Heat-generating Nuclear Waste

    Science.gov (United States)

    Xu, H.; Rutqvist, J.; Zheng, L.; Birkholzer, J. T.

    2016-12-01

    Engineered Barrier Systems (EBS) that include a bentonite-based buffer are designed to isolate the high-level radioactive waste emplaced in tunnels in deep geological formations. The heat emanated from the waste can drive the moisture flow transport and induce strongly coupled Thermal (T), Hydrological (H), Mechanical (M) and Chemical (C) processes within the bentonite buffer and may also impact the evolution of the excavation disturbed zone and the sealing between the buffer and walls of an emplacement tunnel The flow and contaminant transport potential along the disturbed zone can be minimized by backfilling the tunnels with bentonite, if it provides enough swelling stress when hydrated by the host rock. The swelling capability of clay minerals within the bentonite is important for sealing gaps between bentonite block, and between the EBS and the surrounding host rock. However, a high temperature could result in chemical alteration of bentonite-based buffer and backfill materials through illitization, which may compromise the function of these EBS components by reducing their plasticity and capability to swell under wetting. Therefore, an adequate THMC coupling scheme is required to understand and to predict the changes of bentonite for identifying whether EBS bentonite can sustain higher temperatures. More comprehensive links between chemistry and mechanics, taking advantage of the framework provided by a dual-structure model, named Barcelona Expansive Model (BExM), was implemented in TOUGHREACT-FLAC3D and is used to simulate the response of EBS bentonite in in clay formation for a generic case. The current work is to evaluate the chemical changes in EBS bentonite and the effects on the bentonite swelling stress under high temperature. This work sheds light on the interaction between THMC processes, evaluates the potential deterioration of EBS bentonite and supports the decision making in the design of a nuclear waste repository in light of the maximum allowance

  19. Thermo-hydro-mechanical mode of canister retrieval test

    International Nuclear Information System (INIS)

    Zandarin, M.T.; Olivella, S.; Gens', A.; Alonso, E.E.

    2010-01-01

    Document available in extended abstract form only. The Canister Retrieval Tests (CRT) is a full scale in situ experiment performed by SKB at Aespoe Laboratory. The experiment involves placing a canister equipped with electrical heaters inside of a deposition hole bored in Aespoe diorite. The deposition hole is 8.55 metres deep and has a diameter of 1.76 metres. The space between canister and the hole is filled with a MX-80 bentonite buffer. The bentonite buffer was installed in form of blocks and rings of bentonite. At the top of the canister bentonite bricks occupy the volume between the canister top surface and the bottom surface of the plug. Due to the bentonite ring size there are two gaps; once between canister and buffer which was left empty and another one between buffer and rock that was filled with bentonite pellets. The top of the hole was sealed with a retaining plug composed of concrete and a steel plate. The plug was secured against heave caused by the swelling clay with nine cables anchored in the rock. An artificial pressurised saturation system was used because the supply of water from the rock was judged to be insufficient for saturating the buffer in a feasible time. A large number of instruments were installed to monitor the test as follows: - Canister - temperature and strain. - Rock mass - temperature and stress. - Retaining system - force and displacement. - Buffer - temperature, relative humidity, pore pressure and total pressure. After dismantling the tests the final dry density and water content of bentonite and pellets were measured. The comprehensive record of the Thermo-Hydro-Mechanical (THM) processes in the buffer give the possibility to investigate theoretical formulations and models, since the results of THM analyses can be checked against experimental data. As part of the European project THERESA, a 2-D axisymmetric model simulation of CRT bas been carried out. Some of the main objectives of this simulation are the study of the

  20. Thermo-hydro-mechanical behavior of argillite

    International Nuclear Information System (INIS)

    Tran, Duy Thuong; Dormieux, Luc; Lemarchand, Eric; Skoczylas, Frederic

    2012-01-01

    Document available in extended abstract form only. Argillite is a very low permeability geo-material widely encountered: that is the reason why it is an excellent candidate for the storage of long-term nuclear waste depositories. This study focuses on argillites from Meuse-Haute-Marne (East of France) which forms a geological layer located approximately 400 m and 500 m depth. We know that this material is made up of a mixture of shale, quartz and calcite phases. The multi-scale definition of this material suggests the derivation of micro-mechanics reasonings in order to better account for the mechanisms occurring at the local (nano and micro-) scale and controlling the macroscopic mechanical behavior. In this work, up-scaling techniques are used in the context of thermo-hydro-mechanical couplings. The first step consists in clarifying the morphology of the microstructure at the relevant scales (particles arrangement, pore size distribution) and identifying the mechanisms that take place at those scales. These local informations provide the input data of micro-mechanics based models. Schematic picture of the microstructure where the argillite material behaves as a dual-porosity, with liquid in both micro-pores and interlayer space in between clay solid platelets, seems a reasonable starting point for this micro-mechanical modelling of clay. This allows us to link the physical phenomena (swelling clays) and the mechanical properties (elastic moduli, Poisson's ratio). At the pressure applied by the fluid on the solid platelets appears as the sum of the uniform pressure in the micro-pores and of a swelling overpressure depending on the distance between platelets and on the ion concentration in the micro-pores. The latter is proved to be responsible for a local elastic modulus of physical origin. This additional elastic component may strongly be influenced by both relative humidity and temperature. A first contribution of this study is to analysing this local elastic

  1. Coupled thermo-hydro-mechanical experiment at Kamaishi mine. Technical note 15-99-02. Experimental results

    Energy Technology Data Exchange (ETDEWEB)

    Chijimatsu, Masakazu; Sugita, Yutaka; Fujita, Tomoo [Tokai Works, Waste Management and Fuel Cycle Research Center, Waste Isolation Research Division, Barrier Performance Group, Japan Nuclear Cycle Development Inst., Tokai, Ibaraki (Japan); Amemiya, Kiyoshi [Hazama Corp., Tokyo (Japan)

    1999-07-01

    It is an important part of the near field performance assessment of nuclear waste disposal to evaluate coupled thermo-hydro-mechanical (T-H-M) phenomena, e.g., thermal effects on groundwater flow through rock matrix and water seepage into the buffer material, the generation of swelling pressure of the buffer material, and thermal stresses potentially affecting porosity and fracture apertures of the rock. An in-situ T-H-M experiment named Engineered Barrier Experiment' has been conducted at the Kamaishi Mine, of which host rock is granodiorite, in order to establish conceptual models of the coupled T-H-M processes and to build confidence in mathematical and computer codes. In 1995, fourteen boreholes were excavated in order to install the various sensors. After the hydraulic tests, mechanical tests were carried out to obtain the rock properties. After that, a test pit, 1.7 m in diameter and 5.0 m in depth, was excavated. During the excavation, the change of pore pressure, displacement and temperature of rock mass were measured. In 1996, the buffer material and heater were set up in the test pit, and then coupled thermo-hydro-mechanical test was started. The duration of heating phase was 250 days and that of cooling phase was 180 days. The heater surface was controlled to be 100degC during heating phase. Measurement was carried out by a number of sensors installed in both buffer and rock mass during the test. The field experiment leads to a better understanding of the behavior of the coupled thermo-hydro-mechanical phenomena in the near field. (author)

  2. FEBEX II Project Final report on thermo-hydro-mechanical laboratory tests

    Energy Technology Data Exchange (ETDEWEB)

    Lloret, A.; Romero, E.; Villar, M. V.

    2004-07-01

    The results of the thermo-hydro-mechanical (THM) study of the FEBEX bentonite performed during FEBEX II are presented. The laboratory test program continued in part with the works carried out during FEBEX I, particularly in activities related to tests aimed to the calibration of the models, the acquisition of parameters by back-analysis and the improvement of the knowledge on the behaviour of expansive clays. But the program has also included tests on new areas: investigations about the influence of the microstructure changes in bentonite, of temperature and of the solute concentration on the behaviour of clay. Besides, several tests were proposed in order to understand the unexpected behaviour observed in the mock-up test, towards the end of year 2. Temperature effects on water retention curves in confined and unconfined conditions were determined, and swelling pressure, hydraulic conductivity and swelling and consolidation strains as a function of temperature were successfully measured. Different experimental techniques and equipments were developed to study thermal induced changes under partially saturated states, covering a wide range of suctions. FEBEX bentonite remains suitable as a sealing material in HLW repositories (from the hydro- mechanical point of view) for temperatures of up to 80 C, as it keeps its high water retention capacity, low permeability and self-healing ability. The extrapolation of results points out to the preservation of properties for at least up to 100 C. Mercury intrusion porosimetry and environmental scanning electron microscopy provided promising results in order to characterise the bentonite microstructure and to give information about the mechanisms influencing pore size distribution changes on high active clays. The use of digital imaging techniques allowed verifying that at micro-scale level, where chemical phenomena prevail, strains are almost reversible as it is considered in the two-level elasto-plastic models. The swelling

  3. FEBEX II Project Final report on thermo-hydro-mechanical laboratory tests

    International Nuclear Information System (INIS)

    Lloret, A.; Romero, E.; Villar, M. V.

    2004-01-01

    The results of the thermo-hydro-mechanical (THM) study of the FEBEX bentonite performed during FEBEX II are presented. The laboratory test program continued in part with the works carried out during FEBEX I, particularly in activities related to tests aimed to the calibration of the models, the acquisition of parameters by back-analysis and the improvement of the knowledge on the behaviour of expansive clays. But the program has also included tests on new areas: investigations about the influence of the microstructure changes in bentonite, of temperature and of the solute concentration on the behaviour of clay. Besides, several tests were proposed in order to understand the unexpected behaviour observed in the mock-up test, towards the end of year 2. Temperature effects on water retention curves in confined and unconfined conditions were determined, and swelling pressure, hydraulic conductivity and swelling and consolidation strains as a function of temperature were successfully measured. Different experimental techniques and equipments were developed to study thermal induced changes under partially saturated states, covering a wide range of suctions. FEBEX bentonite remains suitable as a sealing material in HLW repositories (from the hydro- mechanical point of view) for temperatures of up to 80 C, as it keeps its high water retention capacity, low permeability and self-healing ability. The extrapolation of results points out to the preservation of properties for at least up to 100 C. Mercury intrusion porosimetry and environmental scanning electron microscopy provided promising results in order to characterise the bentonite microstructure and to give information about the mechanisms influencing pore size distribution changes on high active clays. The use of digital imaging techniques allowed verifying that at micro-scale level, where chemical phenomena prevail, strains are almost reversible as it is considered in the two-level elasto-plastic models. The swelling

  4. Evaluation of coupled thermo-hydro-mechanical phenomena in the near field for geological disposal of high-level radioactive waste

    International Nuclear Information System (INIS)

    Chijimatsu, Masakazu; Fujita, Tomoo; Sugita, Yutaka; Taniguchi, Wataru

    2000-01-01

    , fracture survey, hydraulic test and the measurement of inflow rate into the test pit, which was excavated at the floor of the experiment drift, were conducted. In Chapter 4, hydraulic analyses were conducted using the rock properties obtained by the hydraulic test described in Chapter 3. Analyses were performed by tow kinds of methods; continuum approach and discrete approach. In Chapter 5, the results of in-situ coupled thermo-hydro-mechanical experiment at Kamaishi mine was described. The test pit, 1.7 m in diameter and 5.0 m in depth, was excavated. After the excavation of test pit, the buffer material and heater were set up in the test pit, and then coupled thermo-hydro-mechanical test was started. The duration of heating phase was 250 days and that of cooling phase was 180 days. The heater surface was controlled to be 100degC during heating phase. Measurement was carried out by a number of sensors installed in both buffer and rock mass during the test. In Chapter 6, development of coupled T-H-M model and the validation analyses of model were described. As validation, the analysis of BIG-BEN experiment at Tokai Works in JNC and the analysis of in-situ experiment at Kamaishi mine etc. were performed. In Chapter 7, the coupled T-H-M processes in the near field were simulated with fully coupled model. The material of buffer is bentonite-sand mixture and dry density is 1.6 g/cm 3 . From the results, the following results were obtained; re-saturation time of buffer is strongly dependent on the water pressure in the rock mass. However, it is not dependent on the permeability of rock mass if the intrinsic permeability of rock mass is in the 10 -13 - 10 -18 m 2 range. In the case that the intrinsic permeability of rock mass is approximately 10 -15 m 2 , the initial water content in the buffer does not exert influence on the re-saturation time of buffer. Two dimensional coupled T-H-M analysis in consideration of water drawdown due to the excavation of drift is carried our. As a

  5. Evaluation of coupled thermo-hydro-mechanical phenomena in the near field for geological disposal of high-level radioactive waste

    Energy Technology Data Exchange (ETDEWEB)

    Chijimatsu, Masakazu; Fujita, Tomoo; Sugita, Yutaka; Taniguchi, Wataru [Japan Nuclear Cycle Development Inst., Tokai Works, Waste Management and Fuel Cycle Research Center, Waste Isolation Research Division, Barrier Performance Group, Tokai, Ibaraki (Japan)

    2000-01-01

    , fracture survey, hydraulic test and the measurement of inflow rate into the test pit, which was excavated at the floor of the experiment drift, were conducted. In Chapter 4, hydraulic analyses were conducted using the rock properties obtained by the hydraulic test described in Chapter 3. Analyses were performed by tow kinds of methods; continuum approach and discrete approach. In Chapter 5, the results of in-situ coupled thermo-hydro-mechanical experiment at Kamaishi mine was described. The test pit, 1.7 m in diameter and 5.0 m in depth, was excavated. After the excavation of test pit, the buffer material and heater were set up in the test pit, and then coupled thermo-hydro-mechanical test was started. The duration of heating phase was 250 days and that of cooling phase was 180 days. The heater surface was controlled to be 100degC during heating phase. Measurement was carried out by a number of sensors installed in both buffer and rock mass during the test. In Chapter 6, development of coupled T-H-M model and the validation analyses of model were described. As validation, the analysis of BIG-BEN experiment at Tokai Works in JNC and the analysis of in-situ experiment at Kamaishi mine etc. were performed. In Chapter 7, the coupled T-H-M processes in the near field were simulated with fully coupled model. The material of buffer is bentonite-sand mixture and dry density is 1.6 g/cm{sup 3}. From the results, the following results were obtained; re-saturation time of buffer is strongly dependent on the water pressure in the rock mass. However, it is not dependent on the permeability of rock mass if the intrinsic permeability of rock mass is in the 10{sup -13} - 10{sup -18} m{sup 2} range. In the case that the intrinsic permeability of rock mass is approximately 10{sup -15} m{sup 2}, the initial water content in the buffer does not exert influence on the re-saturation time of buffer. Two dimensional coupled T-H-M analysis in consideration of water drawdown due to the excavation

  6. Thermo-hydro-mechanical modelling of fractured rock masses application to radioactive wastes storage

    International Nuclear Information System (INIS)

    Vuillod, E.

    1995-01-01

    This work belongs to the Decovalex project (international cooperative project for the development of coupled models and their validation against experiments in nuclear waste isolation) of thermo-hydro-mechanical (THM) modeling of fractured rock massifs inside which high level radioactive waste disposal sites are simulated. The mathematical laws controlling the behaviour of the environment are resolved analytically in the case of a continuous environment (definition of an equivalent environment) and numerically if the environment is discontinuous (modeling of joints behaviour). The coupled THM models strongly influence the behaviour of a model. Modeling performed with the UDEC code shows the importance of HM couplings depending on whether the calculations are made in permanent or transient regime, and the influence of the loading path in the case of TM modeling. The geometry of fractures also influences the behaviour of the model. Studying the connexity of a fractures network allows to determine its degree of homogeneity. The comparison between two methods, continuous environment and discontinuous environment, has been carried out by determining the permeability tensor and the stress-deformation relations on fractured test-samples. It shows the differences in behaviour between an homogenized environment and a discrete environment. Finally two exercises of THM modeling of radioactive waste disposal sites illustrate the researches carried out. A far field model has permitted to compare the results obtained with calculation codes using different logics. The second model, a near field one, focusses more on the importance played by fracturing on the behaviour of the massif. The high density of the reference network has required some mathematical developments, in order to determine the representative equivalent volume (continuous approaches), and some mathematical analyses, to correctly simplify the environment (discontinuous approaches). These methods and analyses are

  7. Investigation research on the evaluation of a coupled thermo-hydro-mechanical-chemical phenomena. 4

    International Nuclear Information System (INIS)

    Ishihara, Yoshinao; Sagawa, Hiroshi; Matsuoka, Fushiki; Chijimatsu, Masakazu; Amemiya, Kiyoshi

    2005-02-01

    In order to realize a coupling analysis in the near field of the geological disposal system, the coupling analysis code 'COUPLYS (Coupling analysis system)' on the Thermo-Hydro-Mechanical-Chemical (THMC) phenomena by THAMES, Dtransu-3D·EL and PHREEQC, those are existing analysis code, is developed in this study. (1) We have introduced 8 nodes element for THAMES code in order to solve the coupled thermal, hydraulic and mechanical phenomena. Furthermore, in order to obtain the reliable resolution, each phenomenon is solved separately instead of full coupling. (2) In order to upgrade Dtransu-3D·EL model, we have introduced gas diffusion independent on aqueous element. (3) We have adopted surface site density for the bentonite depend on water content and CSH solid phase based on the ratio of C/S for cementitious material in the geochemistry module, and studied on the methodology of time mesh for kinetic model and separate method for pore water chemistry in the bentonite. (4) In order to develop THMC code, we have modified Multi p hreeqc to keep efficiency distributed processing for geochemical calculation and modified COUPLYS to calculate continuous treatment, and studied on the coupling module. After THAMES, Dtransu, PHREEQC and the hydraulic conductivity module were installed in COUPLYS, verification study was carried out to check basic function. (5) In order to ensure efficiency of analysis processor, we have developed supporting tool for graphic processor for THMC code and supporting tool of interpretation for geochemistry results. (author)

  8. A Coupled Thermo-Hydro-Mechanical Model of Jointed Hard Rock for Compressed Air Energy Storage

    Directory of Open Access Journals (Sweden)

    Xiaoying Zhuang

    2014-01-01

    Full Text Available Renewable energy resources such as wind and solar are intermittent, which causes instability when being connected to utility grid of electricity. Compressed air energy storage (CAES provides an economic and technical viable solution to this problem by utilizing subsurface rock cavern to store the electricity generated by renewable energy in the form of compressed air. Though CAES has been used for over three decades, it is only restricted to salt rock or aquifers for air tightness reason. In this paper, the technical feasibility of utilizing hard rock for CAES is investigated by using a coupled thermo-hydro-mechanical (THM modelling of nonisothermal gas flow. Governing equations are derived from the rules of energy balance, mass balance, and static equilibrium. Cyclic volumetric mass source and heat source models are applied to simulate the gas injection and production. Evaluation is carried out for intact rock and rock with discrete crack, respectively. In both cases, the heat and pressure losses using air mass control and supplementary air injection are compared.

  9. Thermo-hydro-mechanical behavior of fractured rock mass

    International Nuclear Information System (INIS)

    Coste, F.

    1997-12-01

    The purpose of this research is to model Thermo-Hydro-Mechanical behavior of fractured rock mass regarding a nuclear waste re-depository. For this, a methodology of modeling was proposed and was applied to a real underground site (EDF site at Nouvelle Romanche). This methodology consists, in a first step, to determine hydraulic and mechanical REV. Beyond the greatest of these REV, development of a finite element code allows to model all the fractures in an explicit manner. The homogenized mechanical properties are determined in drained and undrained boundary conditions by simulating triaxial tests that represent rock mass subject to loading. These simulations allow to study the evolution of hydraulic and mechanical properties as a function of stress state. Drained and undrained boundary conditions enable to discuss the validity of assimilation of a fractured rock mass to a porous medium. The simulations lead to a better understanding of the behavior of the fractured rock masses and allow to show the dominant role of the shear behavior of the fractures on the hydraulic and mechanical homogenized properties. From a thermal point of view, as long as conduction is dominant, thermal properties of the rock mass are almost the same as those the intact rock. (author)

  10. Research on evaluation of coupled thermo-hydro-mechanical phenomena in the near-field

    International Nuclear Information System (INIS)

    Chijimatsu, Masakazu; Imai, Hisashi; Fukutome, Kazuhito; Kayukawa, Koji; Sasaki, Hajime; Moro, Yoshiji

    2004-02-01

    After emplacement of the engineered barrier system (EBS), it is expected that the near-field environment will be impacted by phenomena such as heat dissipation by conduction and other heat transfer mechanisms, infiltration of groundwater from the surrounding rock in the engineered barrier system, stress imposed by the overburden pressure and generation of swelling pressure in the buffer due to water infiltration. In order to recognize and evaluate these coupled thermo-hydro-mechanical (THM) phenomena, it is necessary to make a confidence of the mathematical models and computer codes. Evaluating these coupled THM phenomena is important in order to clarify the initial transient behavior of the EBS within the near field. DECOVALEX project is an international co-operative project for the DEvelopment of COupled models and their VALidation against EXperiments in nuclear waste isolation and it is significance to participate this project and to apply the code for the validation. Therefore, we tried to apply the developed numerical code against the subjects of DECOVALEX. We carried out the simulation against the Task 1 (simulation of FEBEX in-situ full-scale experiment), Task 3 BMT1 (Bench Mark Test against the near field coupling phenomena) and Task 3 BMT2 (Bench Mark Test against the up-scaling of fractured rock mass). This report shows the simulation results against these tasks. Furthermore, technical investigations about the in-situ full-scale experiment (called Prototype Repository Project) in Aespoe HRL facility by SKB of Sweden were performed. In order to evaluate the coupled phenomena in the engineered barrier, we use the new swelling model based on the theoretical approach. In this paper, we introduce the modeling approach and applicability about the new model. (author)

  11. Computational thermo-hydro-mechanics for freezing and thawing multiphase geological media in the finite deformation range

    Science.gov (United States)

    Sun, W.; Na, S.

    2017-12-01

    A stabilized thermo-hydro-mechanical (THM) finite element model is introduced to investigate the freeze-thaw action of frozen porous media in the finite deformation range. By applying the mixture theory, frozen soil is idealized as a composite consisting of three phases, i.e., solid grain, unfrozen water and ice crystal. A generalized hardening rule at finite strain is adopted to replicate how the elasto-plastic responses and critical state evolve under the influence of phase transitions and heat transfer. The enhanced particle interlocking and ice strengthening during the freezing processes and the thawing-induced consolidation at the geometrical nonlinear regimes are both replicated in numerical examples. The numerical issues due to lack of two-fold inf-sup condition and ill-conditioning of the system of equations are addressed. Numerical examples for engineering applications at cold region are analyzed via the proposed model to predict the impacts of changing climate on infrastructure at cold regions.

  12. Full-scale test on coupled thermo-hydro-mechanical processes in engineered barrier system

    International Nuclear Information System (INIS)

    Moro, Yoshiji; Fujita, Tomoo; Kanno, Takeshi; Kobayashi, Akira.

    1994-01-01

    On dynamic behavior within artificial barrier in ground layer disposal of high level radioactive wastes, some phenomena such as exotherm from the wastes, penetration of groundwater from surrounding base rock, swelling pressure formation of buffer material due to penetration of groundwater, ground pressure change of the surrounding base rock, and so forth are supposed to affect each other. It is one of important problems from a viewpoint of elucidation of near field environment in the property evaluation study to evaluate such thermo-hydro-mechanical coupled phenomena. As results of the investigation from such reason and its application to actual test in accompany with execution of heating and water inserting test in the Big-Ben (Big-Bentonite facility), the following informations were obtained: (1) In heating and water inserting test, data on temperature distribution, water content ratio distribution and swelling pressure of each portion for 5 months could be obtained. (2) water migration due to water slope was divided to migrations due to steam and liquid water, of which models were made according to Fick and Darcy laws, respectively. (3) As a simulation of water migration, water diffusion coefficient due to temperature slope could be expressed almost by a model with nonlinearity to temperature. (G.K.)

  13. Modelling of thermo-hydro-mechanical couplings and damage of viscoplastic rocks in the context of radioactive waste storage

    International Nuclear Information System (INIS)

    Kharkhour, H.

    2002-12-01

    Trying to develop a model taking into account the complex rheology of a geologic media characterized by visco-plasticity, damage and thermo-hydro-mechanical couplings is unusual in geotechnics. This is not the case for radioactive waste storage that presents specificities from several viewpoints. Indeed, the scales of time and space concerned by this type of storage are disproportionate to those of civil engineering works or mines. Another specificity of the radioactive waste storage lies in the coupled processes involved. No effect likely to compromise the long-term security of the storage could be ignored. For example this is the case of damage, a phenomenon which does not necessarily lead to a major change of the mechanical behavior of the works but can influence the permeability of the medium in relation with a migration of radionuclides. It can be conceived that this phenomenon finds all its importance in the context of the thermo-hydro-mechanical couplings of a waste storage with high activity. However, the interaction between the damage and the THM coupled processes was the object of very few research subject up to now. This. is even more true for viscoplastic media considered as ductile, and therefore, less prone to cracking than brittle media. It is exactly in this 'original' but difficult context that took place the research presented in this report. This study was dedicated to the analysis of the phenomena and the thermal, hydraulic and mechanical couplings occurring in the near and far field of a high activity radioactive waste storage. Two examples of geological media were considered in this report: the clayey rock of Callovo-Oxfordian, called ' Argilites de l'Est ', target rock of the ANDRA project to carry out a subterranean laboratory for the study of long life radioactive waste storage; and the salt rock of the. subterranean laboratory in the old salt mine of Asse in Germany. (author)

  14. Summary report of research on evaluation of coupled thermo-hydro-mechanical behavior in the engineered barrier

    International Nuclear Information System (INIS)

    Chijimatsu, Masakazu; Amemiya, Kiyoshi; Yamashita, Ryo

    2002-02-01

    After emplacement of the engineered barrier system (EBS), it is expected that the near-field environment will be impacted by phenomena such as heat dissipation by conduction and other heat transfer mechanisms, infiltration of groundwater from the surrounding rock in to the engineered barrier system, stress imposed by the overburden pressure and generation of swelling pressure in the buffer due to water infiltration. In order to recognize and evaluate these coupled thermo-hydro-mechanical (THM) phenomena, it is necessary to make a confidence of the mathematical models and computer codes. Evaluating these coupled THM phenomena is important in order to clarify the initial transient behavior of the EBS within the near field. DECOVALEX project is an international co-operative project for the DEvelopment of COupled models and their VALidation against EXperiments in nuclear waste isolation and it is significance to participate this project and to apply the code for the validation. Therefore, we tried to apply the developed numerical code against the subjects of DECOVALEX. In the above numerical code, swelling phenomenon is modeled as the function of water potential. However it dose no evaluate the experiment results enough. Then, we try to apply the new model. (author)

  15. 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.

  16. Thermo-Hydro Mechanical Characteristics and Processes in the Clay Barrier of a High Level Radioactive Waste Repository. State of the Art Report

    Energy Technology Data Exchange (ETDEWEB)

    Villar, M. V.

    2004-07-01

    This document is a summary of the available information on the thermo-hydro-mechanical properties of the bentonite barrier of a high-level radioactive waste repository and of the processes taking place in it during the successive repository operation phases. Mainly the thermal properties, the volume change processes (swelling and consolidation), the permeability and the water retention capacity are analysed. A review is made of the existing experimental knowledge on the modification of the these properties by the effect of temperature, water salinity, humidity and density of the bentonite, and their foreseen evolution as a consequence of the processes expected in the repository. The compiled evolution refers mostly to the FEBEX (Spain), the MX-80 (US) and the FoCa (France) bentonite, considered as reference barrier materials in several European disposal concepts. (Author) 102 refs.

  17. Thermo-Hydro Mechanical Characteristics and Processes in the Clay Barrier of a High Level Radioactive Waste Repository. State of the Art Report

    International Nuclear Information System (INIS)

    Villar, M. V.

    2004-01-01

    This document is a summary of the available information on the thermo-hydro-mechanical properties of the bentonite barrier of a high-level radioactive waste repository and of the processes taking place in it during the successive repository operation phases. Mainly the thermal properties, the volume change processes (swelling and consolidation), the permeability and the water retention capacity are analysed. A review is made of the existing experimental knowledge on the modification of the these properties by the effect of temperature, water salinity, humidity and density of the bentonite, and their foreseen evolution as a consequence of the processes expected in the repository. The compiled evolution refers mostly to the FEBEX (Spain), the MX-80 (USA) and the FoCa (France) bentonite, considered as reference barrier materials in several European disposal concepts. (Author) 102 refs

  18. Investigation research on the evaluation of a coupled thermo-hydro-mechanical-chemical phenomena. Outline report

    International Nuclear Information System (INIS)

    Chijimatsu, Masakazu; Amemiya, Kiyoshi; Neyama, Atsushi; Iwata, Hiroshi; Nakagawa, Koichi; Ishihara, Yoshinao; Shiozaki, Isao; Sagawa, Hiroshi

    2002-02-01

    In order to realize a coupling analysis in the near field of the geological disposal system, this study has been studied on the addition of the mass transport model to the coupled thermo-hydro-mechanical analysis code (THAMES) and preliminary coupling analysis by using development environmental tool (Diffpack) for numerical analysis. (1) In order to prepare the strategy on the addition of the mass transport model to the coupled thermo-hydro-mechanical analysis code (THAMES), we have studied on the requirement of THAMES-Transport and methodology of coupling analysis. After that we set out modification plan by the Eulerian-Lagrangian (EL) method. (2) Based on the document of modification plan, we have done addition of the mass transport model to the coupled thermo-hydro-mechanical analysis code (THAMES) and carried out verification analysis in order to confirm on the accuracy of THAMES-Transport. (3) In order to understand on the behavior of NaCl in the porewater under the coupled thermo-hydro-mechanical phenomena in the HLW engineered barrier system, we have calculated coupling phenomenon by using THAMES-Transport. Transportation and concentration phenomena of NaCl are calculated but precipitation of NaCl is not occurred under the analysis conditions in this report. (4) In order to confirm about feasibility of coupling analysis under the development environmental tool (Diffpack) for numerical analysis, we have carried out on the design work and writing program of the preliminary coupling system. In this study, we have adopted existing transport model (HYDROGEOCHEM) and geochemical model (phreeqe60) for preliminary coupling system. (5) In order to confirm program correctness of preliminary coupling system, we have carried out benchmarking analysis by using existing reactive-transport analysis code (HYDROGEOCHEM). (6) We have been prepared short-range development plan based on through the modification study of THAMES and writing program of the preliminary coupling

  19. Investigation research on the evaluation of a coupled thermo-hydro-mechanical-chemical phenomena. Result report

    International Nuclear Information System (INIS)

    Chijimatsu, Masakazu; Amemiya, Kiyoshi; Shiozaki, Isao; Neyama, Atsushi; Iwata, Hiroshi; Nakagawa, Koichi; Ishihara, Yoshinao; Sagawa, Hiroshi

    2002-02-01

    In order to realize a coupling analysis in the near field of the geological disposal system, this study has been studied on the addition of the mass transport model to the coupled thermo-hydro-mechanical analysis code (THAMES) and preliminary coupling analysis by using development environmental tool (Diffpack) for numerical analysis. (1) In order to prepare the strategy on the addition of the mass transport model to the coupled thermo-hydro-mechanical analysis code (THAMES), we have studied on the requirement of THAMES-Transport and methodology of coupling analysis. After that we set out modification plan by the Eulerian-Lagrangian (EL) method. (2) Based on the document of modification plan, we have done addition of the mass transport model to the coupled thermo-hydro-mechanical analysis code (THAMES) and carried out verification analysis in order to confirm on the accuracy of THAMES-Transport. (3) In order to understand on the behavior of NaCl in the porewater under the coupled thermo-hydro-mechanical phenomena in the HLW engineered barrier system, we have calculated coupling phenomenon by using THAMES-Transport. Transportation and concentration phenomena of NaCl are calculated but precipitation of NaCl is not occurred under the analysis conditions in this report. (4) In order to confirm about feasibility of coupling analysis under the development environmental tool (Diffpack) for numerical analysis, we have carried out on the design work and writing program of the preliminary coupling system. In this study, we have adopted existing transport model (HYDROGEOCHEM) and geochemical model (phreeqe 60) for preliminary coupling system. (5) In order to confirm program correctness of preliminary coupling system, we have carried out benchmarking analysis by using existing reactive-transport analysis code (HYDROGEOCHEM). (6) We have been prepared short-range development plan based on through the modification study of THAMES and writing program of the preliminary coupling

  20. Main outcomes from in situ thermo-hydro-mechanical experiments programme to demonstrate feasibility of radioactive high-level waste disposal in the Callovo-Oxfordian claystone

    Directory of Open Access Journals (Sweden)

    G. Armand

    2017-06-01

    Full Text Available In the context of radioactive waste disposal, an underground research laboratory (URL is a facility in which experiments are conducted to demonstrate the feasibility of constructing and operating a radioactive waste disposal facility within a geological formation. The Meuse/Haute-Marne URL is a site-specific facility planned to study the feasibility of a radioactive waste disposal in the Callovo-Oxfordian (COx claystone. The thermo-hydro-mechanical (THM behaviour of the host rock is significant for the design of the underground nuclear waste disposal facility and for its long-term safety. The French National Radioactive Waste Management Agency (Andra has begun a research programme aiming to demonstrate the relevancy of the French high-level waste (HLW concept. This paper presents the programme implemented from small-scale (small diameter boreholes to full-scale demonstration experiments to study the THM effects of the thermal transient on the COx claystone and the strategy implemented in this new programme to demonstrate and optimise current disposal facility components for HLW. It shows that the French high-level waste concept is feasible and working in the COx claystone. It also exhibits that, as for other plastic clay or claystone, heating-induced pore pressure increases and that the THM behaviour is anisotropic.

  1. Coupled thermo-hydro-mechanical experiment at Kamaishi mine. Technical note 08-96-01. Measurement data related to excavation of the test pit

    International Nuclear Information System (INIS)

    Fujita, T.; Chijimatsu, M.; Sugita, Y.; Ishikawa, H.

    1997-07-01

    It is an important part of the near field performance assessment of nuclear waste disposal to evaluate coupled thermo-hydro-mechanical (T-H-M) phenomena, e.g., thermal effects on groundwater flow through rock matrix and water seepage into the buffer material, the generation of swelling pressure of the buffer material, and thermal stresses potentially affecting porosity and fracture apertures of the rock. An in-situ T-H-M experiment named Engineered Barrier Experiment ' has been conducted at the Kamaishi Mine, of which host rock is granodiorite, in order to establish conceptual models of the coupled T-H-M processes and to build confidence in mathematical models and computer codes. In 1995, fourteen boreholes were excavated in order to install the various sensors. After the hydraulic tests, mechanical tests were carried out to obtain the rock properties. After that, a test pit, 1.7 m in diameter and 5.0 m in depth, was excavated. During the excavation, the change of pore pressure, displacement and temperature of rock mass were measured. Furthermore, pit convergence was measured. This note shows the results of mechanical tests and measurement data during the excavation of test pit. (author)

  2. MX-80 Bentonite. Thermal-Hydro-Mechanical Characterisation Performed at CIEMAT in the Context of the Prototype Project

    International Nuclear Information System (INIS)

    Villar, M. V.

    2005-01-01

    This document details the results of the thermo-hydro-mechanical (THM) characterisation of the commercial MX-80 bentonite performed by CIEMAT from 2001 to 2004 in the context of a project carried out at the AEspoe Hard Rock Laboratory (Sweden), the Prototype Repository. The swelling pressure and the permeability of the bentonite compacted to different dry densities has been determined, as well as the influence of the permeant salinity on hydraulic conductivity. The influence of salinity on the retention capacity of the compacted bentonite has been studied. For that, a new methodology has been designed. Water retention curves have been determined at temperatures of 20 and 60 0 C. Suction controlled odometer tests have been performed at 20oC. Finally, the behaviour of the MX-80 bentonite has been compared to that of the Spanish FEBEX bentonite. (Author) 13 refs

  3. MX-80 Bentonite. thermal-Hydro-Mechanical Characterisation Performed at CIEMAT in the Context of the Prototype Project

    Energy Technology Data Exchange (ETDEWEB)

    Villar, M. V.

    2005-07-01

    This document details the results of the thermo-hydro-mechanical (THM) characterisation of the commercial MX-80 bentonite performed by CIEMAT from 2001 to 2004 in the context of a project carried out at the AEspoe Hard Rock Laboratory (Sweden), the Prototype Repository. The swelling pressure and the permeability of the bentonite compacted to different dry densities has been determined, as well as the influence of the permeant salinity on hydraulic conductivity. The influence of salinity on the retention capacity of the compacted bentonite has been studied. For that, a new methodology has been designed. Water retention curves have been determined at temperatures of 20 and 60oC. Suction controlled odometer tests have been performed at 20oC. Finally, the behaviour of the MX-80 bentonite has been compared to that of the Spanish FEBEX bentonite. (Author) 13 refs.

  4. Investigation research on the evaluation of a coupled thermo-hydro-mechanical-chemical phenomena. 3. Result Report

    International Nuclear Information System (INIS)

    Ishihara, Yoshinao; Ito, Takaya; Chijimatsu, Masakazu; Amemiya, Kiyoshi; Shiozaki, Isao

    2004-02-01

    In order to realize a coupling analysis in the near field of the geological disposal system, the coupling analysis code 'COUPLYS (Coupling analysis system)' on the Thermo-Hydro-Mechanical-Chemical (THMC) phenomena by THAMES, Dtransu and phreeqc, which are existing analysis code, is developed in this study. And some case analyses on THMC phenomena are carried out by this code. (1) Some supporting modules, which include the transfer of dissolution concentration and total concentration (dissolution + precipitation concentration), were prepared as a functional expansion. And in order to add on the function of treat de-gases and gases diffusion, accumulation and dilution phenomena, the mass transport analysis code was modified. (2) We have modified reactive transport module to treat ionic exchange, surface reaction and kinetic reaction in the each barrier. (3) We have prepared hydraulic conductivity module of buffer material depending on change of dry density due to chemical equilibrium (dissolution and precipitation of minerals), degradation of buffer material such as Ca-type bentonite and change of concentration of NaCl solutions. After THAMES, Dtransu, phreeqc and the hydraulic conductivity module were installed in COUPLYS (Coupling Analysis), verification study was carried out to check basic function. And we have modified COUPLYS to control coupling process. (4) In order to confirm the applicability of the developed THMC analysis code (existing analysis code and COUPLYS), we have carried out case analyses on 1-dimensional and 3-dimensional model which are including vitrified waste, over-pack, buffer material and rock in the HLW near-field. (author)

  5. Coupled thermo-hydro-mechanical processes associated with a radioactive waste repository

    International Nuclear Information System (INIS)

    Tsang, C.F.

    1988-01-01

    The performance assessment of a nuclear waste geologic repository presents a scientific and technical problem of a scope far beyond the evaluation of most civil and geologic constructions. First performance prediction must be made for tens of thousands of years, and a secondly, in calculating potential leakage rates from a repository to the biosphere the authors must determine not only the mean or average travel time but also the shorter travel times of low concentrations. These two criteria demand an understanding of all significant physical and chemical processes likely to occur around a nuclear waste repository. In particular, processes coupling thermal transfer fluid flow, mechanical deformation and chemical reactors, which may be slow in a laboratory time scale, may become very important. This paper gives a general survey on the subject, with specific examples of a number of relevant coupled thermo-hydro-mechanical processes associated with nuclear waste repository

  6. Experimental study of thermo-hydro-mechanical behaviour of Callovo-Oxfordian Clay-stone

    International Nuclear Information System (INIS)

    Mohajerani, M.

    2011-01-01

    During the different phases of the exothermic radioactive waste deep disposal (excavation, operation) and after permanent closure, the host rock is submitted to various coupled mechanical, hydraulic and thermal phenomena. Hence, a thorough investigation of the thermo-hydro-mechanical behaviour of the rock is necessary to complete existing data and to better understand and model the short and long term behaviour of the Callovo-Oxfordian (COx) clay formation in Bure (Meuse/Haute-Marne - M/HM), considered by ANDRA as a potential host rock in France.In this work, the compression - swelling behaviour of the COx Clay-stone was first investigated by carrying out a series of high-pressure oedometric tests. The results, interpreted in terms of coupling between damage and swelling, showed that the magnitude of swelling was linked to the density of the fissures created during compression. In a second step, the hydro-mechanical and thermo-hydro-mechanical behaviour of the saturated Clay-stone under a mean stress close to the in situ one were investigated by using two devices with short drainage path (10 mm), namely a isotropic cell and a newly designed hollow cylinder triaxial cell with local displacement measurements. These devices helped to solve two majors problems related to testing very low permeability materials: i) a satisfactory previous sample saturation (indicated by good Skempton values) and ii) satisfactory drainage conditions. Some typical constitutive parameters (Skempton and Biot's coefficients, drained and undrained compressibility coefficients) have been determined at ambient temperature through isotropic compression tests that also confirmed the transverse isotropy of the Clay-stone. The consistency of the obtained parameters has been checked in a saturated poro-elastic framework. Two aspects of the thermo-hydro-mechanical behaviour of the COx Clay-stone have then been investigated through different heating tests and through drained and undrained isotropic

  7. Investigation of the THM behaviour of the buffer and rock-buffer interaction during the canister retrieval test performed in the ASPÖ Hard Rock Laboratory

    International Nuclear Information System (INIS)

    Millard, A.; Barnichon, J.D.

    2014-01-01

    In the framework of the THERESA European project, numerical modelling of coupled thermo-hydro-mechanical (THM) and thermo-hydro-mechanical-chemical (THMC) behaviour of buffer (bentonite) and buffer-rock interfaces for deep underground nuclear waste repositories has been undertaken, with focus on the performance assessments. A major step of the project was the analysis of a large scale test, called the Canister Retrieval test, which has been performed in Aspö Hard Rock Laboratory. It consists in a full scale test of the emplacement of a canister with the surrounding buffer material. A deposition hole was first bored, and then the canister with heaters was installed together with bentonite blocks. The gap between the rock and the bentonite blocks was filled with bentonite pellets. The whole set was artificially wetted from its external boundary in order to accelerate the expected natural rehydration by the surrounding rock. The evolution of the THM processes was recorded over 5 years. Before analysing the whole CRT experiment, a preliminary simpler problem has been defined, which consisted in modelling a disc of buffer at canister mid-height. Thanks to the available experimental recorded measurements, it has been possible to numerically investigate the respective influence of the various THM parameters involved in the modelling of the physical processes. The theoretical model is based on one hand on the Richard's approximation for the flow calculation, and on the other hand on a Biot's type model for the hydro-mechanical behaviour. It has revealed the large influence of the liquid relative permeability, which is unfortunately in general not directly available from experiments and must be determined through inverse analysis techniques. Then, in a second stage, the whole CRT experiment has been analysed. For simplicity reasons, an axisymetrical model has been adopted, although the presence of a neighbouring experiment did influence the CRT results. The comparisons of

  8. Thermo-hydro-mechanical characterisation and modelling of MX-80 granular bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Seiphoori, A.

    2014-07-01

    The library of the Swiss Federal Institute of Technology EPFL does not publish an abstract for this thesis. Accordingly, no abstract can be made available by INIS. However, the EPFL library will send the full text of the thesis, free of charge, to anybody asking for it. Please use the indicated DOI to contact the library.

  9. Thermo-hydro-mechanical characterisation and modelling of MX-80 granular bentonite

    International Nuclear Information System (INIS)

    Seiphoori, A.

    2014-01-01

    The library of the Swiss Federal Institute of Technology EPFL does not publish an abstract for this thesis. Accordingly, no abstract can be made available by INIS. However, the EPFL library will send the full text of the thesis, free of charge, to anybody asking for it. Please use the indicated DOI to contact the library

  10. Long term thermo-hydro-mechanical interaction behavior study of the saturated, discontinuous granitic rock mass around the radwaste repository using a steady state flow algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jhin Wung; Bae, Dae Suk; Kang, Chul Hyung; Choi, Jong Won [Korea Atomic Energy Research Institute, Taejeon (Korea)

    2002-02-01

    The objective of the present study is to understand the long term (500 years) thermo-hydro-mechanical interaction behavior of the 500 m depth underground radwaste repository in the saturated, discontinuous granitic rock mass using a steady state flow algorithm. The numerical model includes a saturated granitic rock mass with joints around the repository and a 45 .deg. C fault passing through the tunnel roof-wall intersection, and a canister with PWR spent fuels surrounded by the compacted bentonite and mixed-bentonite. Barton-Bandis joint constitutive model from the UDEC code is used for the joints. For the hydraulic analysis, a steady state flow algorithm is used for the groundwater flow through the rock joints. For the thermal analysis, heat transfer is modeled as isotropic conduction and heat decays exponentially with time. The results show that the variations of the hydraulic aperture, hydraulic conductivity, normal stress, normal displacements, and shear displacements of the joints are high in the vicinity of the repository and stay fairly constant on the region away from the repository. 14 refs., 15 figs., 11 tabs. (Author)

  11. Thermo-hydro mechanical modeling in unsaturated hard clay: application to nuclear waste storage

    International Nuclear Information System (INIS)

    Jia, Y.

    2006-07-01

    This work presents an elastoplastic damage model for argillite in unsaturated conditions. A short resume of experimental investigations is presented in the first part. The results obtained show an important plastic deformation coupled with damage induced by initiation and growth of microcracks. Influences of water content on the mechanical behaviour are also investigated. Based on experimental data and micro-mechanical considerations, a general constitutive model is proposed for the poro-mechanical behavior of argillite in unsaturated conditions. The time dependent creep has also been incorporated in they model. The performance of the model is examined by comparing numerical simulation with experimental data in various load paths under saturated and unsaturated conditions. Finally, the model is applied to hydro-mechanical coupling study of the REP experiment and thermo-hydro-mechanical coupling study of the HE-D experiment. A good agreement is obtained between experimental data and numerical predictions. It has been shown that the proposed model describe correctly the main features of the mechanical behaviour of unsaturated rocks. (author)

  12. A coupled thermo-hydro-mechanical-damage model for concrete subjected to moderate temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Bary, B.; Carpentier, O. [CEA Saclay, DEN/DPC/SCCME/LECBA, F-91191 Gif Sur Yvette, (France); Ranc, G. [CEA VALRHO, DEN/DTEC/L2EC/LCEC, F-30207 Bagnols Sur Ceze, (France); Durand, S. [CEA Saclay, DEN/DM2S/SEMT/LM2S, F-91191 Gif Sur Yvette, (France)

    2008-07-01

    This study focuses on the concrete behavior subjected to moderate temperatures, with a particular emphasis on the transient thermo-hydric stage. A simplified coupled thermo-hydro-mechanical model is developed with the assumption that the gaseous phase is composed uniquely of vapor. Estimations of the mechanical parameters, Biot coefficient and permeability as a function of damage and saturation degree are provided by applying effective-medium approximation schemes. The isotherm adsorption curves are supposed to depend upon both temperature and crack-induced porosity. The effects of damage and parameters linked to transfer (in particular the adsorption curves) on the concrete structure response in the transient phase of heating are then investigated and evaluated. To this aim, the model is applied to the simulation of concrete cylinders with height and diameter of 0.80 m subjected to heating rates of 0.1 and 10 degrees C/min up to 160 degrees C. The numerical results are analyzed, commented and compared with experimental ones in terms of water mass loss, temperatures and gas pressures evolutions. A numerical study indicates that some parameters have a greater influence on the results than others, and that certain coupling terms in the mass conservation equation of water may be neglected. (authors)

  13. Investigation research on the evaluation of a coupled thermo-hydro-mechanical-chemical phenomena. 2. Result report

    International Nuclear Information System (INIS)

    Ishihara, Yoshinao; Ito Takaya; Chijimatsu, Masakazu; Amemiya, Kiyoshi; Shiozaki, Isao; Neyama, Atsushi; Tanaka, Yumiko

    2003-02-01

    In order to realize a coupling analysis in the near field of the geological disposal system, the coupling analysis code on the thermo-hydro-mechanical-chemical phenomena by THAMES, Dtransu and phreeqe60, which are existing analysis code, is developed in this study. And we carried out the case analysis on the thermo-hydro-mechanical-chemical phenomena by this code. (1) We have developed coupling analysis system to manage coupling analysis and to control coupling process automatically for THAMES (thermo-hydro-mechanical analysis code), Dtransu (mass transport analysis code) and phreeqe60 (geochemical analysis code). (2) Some supporting module, which includes transfer of dissolution concentration and total concentration (dissolution + precipitation concentration), was prepared as a functional expansion. And in order to treat multi-chemical elements, we have codified mass transport analysis code. (3) We have prepared hydraulic conductivity module of buffer material depending on change of dry density due to chemical equilibrium (dissolution and precipitation of minerals), and change of concentration of NaCl solutions. After THAMES, Dtransu, phreeqe60 and hydraulic conductivity module were installed in the COUPLYS, sensitivity analysis was carried out to check basic operation. (4) In order to confirm the applicability of the developed THMC analysis code, we have carried out case analysis on 1-dimensional and 3-dimensional model which including vitrified waste, over-pack, buffer material and rock in the HLW near-field. (author)

  14. Development of a finite element code to solve thermo-hydro-mechanical coupling and simulate induced seismicity.

    Science.gov (United States)

    María Gómez Castro, Berta; De Simone, Silvia; Rossi, Riccardo; Larese De Tetto, Antonia; Carrera Ramírez, Jesús

    2015-04-01

    Coupled thermo-hydro-mechanical modeling is essential for CO2 storage because of (1) large amounts of CO2 will be injected, which will cause large pressure buildups and might compromise the mechanical stability of the caprock seal, (2) the most efficient technique to inject CO2 is the cold injection, which induces thermal stress changes in the reservoir and seal. These stress variations can cause mechanical failure in the caprock and can also trigger induced earthquakes. To properly assess these effects, numerical models that take into account the short and long-term thermo-hydro-mechanical coupling are an important tool. For this purpose, there is a growing need of codes that couple these processes efficiently and accurately. This work involves the development of an open-source, finite element code written in C ++ for correctly modeling the effects of thermo-hydro-mechanical coupling in the field of CO2 storage and in others fields related to these processes (geothermal energy systems, fracking, nuclear waste disposal, etc.), and capable to simulate induced seismicity. In order to be able to simulate earthquakes, a new lower dimensional interface element will be implemented in the code to represent preexisting fractures, where pressure continuity will be imposed across the fractures.

  15. Analysis and modeling of coupled thermo-hydro-mechanical phenomena in 3D fractured media

    International Nuclear Information System (INIS)

    Canamon Valera, I.

    2006-11-01

    This doctoral research was conducted as part of a joint France-Spain co-tutelage PhD thesis in the framework of a bilateral agreement between two universities, the Institut National Polytechnique de Toulouse (INPT) and the Universidad Politecnica de Madrid (UPM). It concerns a problem of common interest at the national and international levels, namely, the disposal of radioactive waste in deep geological repositories. The present work is devoted, more precisely, to near-field hydrogeological aspects involving mass and heat transport phenomena. The first part of the work is devoted to a specific data interpretation problem (pressures, relative humidities, temperatures) in a multi-barrier experimental system at the scale of a few meters - the 'Mock-Up Test' of the FEBEX project, conducted in Spain. Over 500 time series are characterized in terms of spatial, temporal, and/or frequency/scale-based statistical analysis techniques. The time evolution and coupling of physical phenomena during the experiment are analyzed, and conclusions are drawn concerning the behavior and reliability of the sensors. The second part of the thesis develops in more detail the 3-Dimensional (3D) modeling of coupled Thermo-Hydro-Mechanical phenomena in a fractured porous rock, this time at the scale of a hundred meters, based on the data of the 'In-Situ Test' of the FEBEX project conducted at the Grimsel Test Site in the Swiss Alps. As a first step, a reconstruction of the 3D fracture network is obtained by Monte Carlo simulation, taking into account through optimization the geomorphological data collected around the FEBEX gallery. The heterogeneous distribution of traces observed on the cylindrical wall of the tunnel is fairly well reproduced in the simulated network. In a second step, we develop a method to estimate the equivalent permeability of a many-fractured block by extending the superposition method of Ababou et al. [1994] to the case where the permeability of the rock matrix is not

  16. Thermo-hydro-mechanical coupling in long-term sedimentary rock response

    Science.gov (United States)

    Makhnenko, R. Y.; Podladchikov, Y.

    2017-12-01

    Storage of nuclear waste or CO2 affects the state of stress and pore pressure in the subsurface and may induce large thermal gradients in the rock formations. In general, the associated coupled thermo-hydro-mechanical effect on long-term rock deformation and fluid flow have to be studied. Principles behind mathematical models for poroviscoelastic response are reviewed, and poroviscous model parameter, the bulk viscosity, is included in the constitutive equations. Time-dependent response (creep) of fluid-filled sedimentary rocks is experimentally quantified at isotropic stress states. Three poroelastic parameters are measured by drained, undrained, and unjacketed geomechanical tests for quartz-rich Berea sandstone, calcite-rich Apulian limestone, and clay-rich Jurassic shale. The bulk viscosity is calculated from the measurements of pore pressure growth under undrained conditions, which requires time scales 104 s. The bulk viscosity is reported to be on the order of 1015 Pa•s for the sandstone, limestone, and shale. It is found to be decreasing with the increase of pore pressure despite corresponding decrease in the effective stress. Additionally, increase of temperature (from 24 ºC to 40 ºC) enhances creep, where the most pronounced effect is reported for the shale with bulk viscosity decrease by a factor of 3. Viscous compaction of fluid-filled porous media allows a generation of a special type of fluid flow instability that leads to formation of high-porosity, high-permeability domains that are able to self-propagate upwards due to interplay between buoyancy and viscous resistance of the deforming porous matrix. This instability is known as "porosity wave" and its formation is possible under conditions applicable to deep CO2 storage in reservoirs and explains creation of high-porosity channels and chimneys. The reported experiments show that the formation of high-permeability pathways is most likely to occur in low-permeable clay-rich materials (caprock

  17. Coupled thermo-hydro-mechanical calculations of the water saturation phase of a KBS-3 deposition hole. Influence of hydraulic rock properties on the water saturation phase

    International Nuclear Information System (INIS)

    Boergesson, Lennart; Hernelind, J.

    1999-12-01

    The wetting process in deposition holes designed according to the KBS-3-concept has been simulated with finite element calculations of the thermo-hydro-mechanical processes in the buffer, backfill and surrounding rock. The buffer material has been modelled according to the preliminary material models developed for swelling clay. The properties of the rock have been varied in order to investigate the influence of the rock properties and the hydraulic conditions on the wetting processes. In the modelling of the test holes the permeability of the rock matrix, the water supply from the backfill, the water pressure in the surrounding rock, the permeability of the disturbed zone around the deposition hole, the water retention properties of the rock, and the transmissivity of two fractures intersecting the deposition hole have been varied. The calculations indicate that the wetting takes about 5 years if the water pressure in the rock is high and if the permeability of the rock is so high that the properties of the bentonite determine the wetting rate. However, it may take considerably more than 30 years if the rock is very tight and the water pressure in the rock is low. The calculations also show that the influence of the rock structure is rather large except for the influence of the transmissivity T of the fractures, which turned out to be insignificant for the values used in the calculations

  18. Long-term stability of the near-field about high-level radioactive waste repository in thermo-hydro-mechanical coupling action condition

    International Nuclear Information System (INIS)

    Liu Yuemiao; Wang Ju; Ke Dan; Cai Meifeng

    2008-01-01

    It is a long-term process for the high-level radioactive waste repository, from opening, construction to end of its service. The long-term stability of the near-field is the key issue for the design of HLW repository because the opening and heat generated from the HLW. Through a nationwide investigation, Beishan area, a Gobi desert in Gansu province, is considered as a suitable candidate and GMZ bentonite deposit which located in Xinghe County, Inner Mongolia has been proposed for the supplier of buffer/backfill material for HLW geological repository in China. According to the R and D guide of high-level radioactive waste disposal in China, the 3D model of HLW repository with high-level radioactive waste, canister and buffer/backfill material is established using FLAC3D. To take into account in situ stress, geothermal gradient, groundwater, thermal relief of HLW and swelling pressure of buffer/backfill material, the evolution of temperature, stress and displacement of HLW repository under thermo-mechanical coupling, hydro-mechanical coupling and thermo-hydro-mechanical coupling conditions was analyzed respectively. The long-term stability of HLW repository in Beishan area was studied. (authors)

  19. Coupled thermo-hydro-mechanical analysis for the conceptual repository of high-level radioactive waste in China

    International Nuclear Information System (INIS)

    Lin, Y.M.; Wang, J.; Ke, D.; Cai, M.F.

    2010-01-01

    In order to safely dispose of the high-level radioactive waste (HLW), RD guide of HLW disposal was published in February 2006 in China. The spent fuel from nuclear power plants will be reprocessed first, followed by verification and final disposal. A conceptual repository 3D configuration comprises a single vertical borehole in a continuous and homogeneous hard rock, containing a canister surrounded by an over-pack and a bentonite layer, and the backfilled upper portion of the gallery using FLAC3D. To take into account in situ stress, geothermal gradient and groundwater of Beishan area, thermal relief of HLW and swelling pressure of buffer/backfill material made by GMZ01 bentonite, the TM, HM and THM evolution of the whole configuration is simulated over a period of 100 years. The results demonstrate that temperature is hardly affected by the couplings. In contrast, the influence of the couplings on the mechanical stresses is considerable. The repository has long-term stability in fully THM coupling action condition. (authors)

  20. On a morphological approach of the meso-structure for the multi-scale analysis of the thermo-hydro-mechanical behaviour of cementitious materials

    International Nuclear Information System (INIS)

    Le, T.T.H.

    2011-01-01

    The investigation of the behavior of heated concrete is a major research topic which concerns the assessment of safety level of structures when exposed to high temperatures, for instance during a fire. For this purpose, several modeling approaches were developed within thermo-hydro-mechanical (THM) frameworks in order to take into account the involved physic-chemical and mechanical processes that affect stability of heated concrete. However, existing models often do note account explicitly for the heterogeneity of the material: concrete is composite material that may be schematized as an assembly of inclusions (aggregates) embedded in a cementitious matrix (cement paste). This latter may be described as a partially saturated open porous medium. The aggregates are characterized by their mineralogical nature together with their morphology and size distribution. The material heterogeneity bring an additional complexity: the need to take into account the microstructure in order to quantify the effect of matrix-inclusion thermal, hygral and mechanical incompatibilities on the THM behavior of concrete. This work is a first step in this direction. For this purpose, a three-dimensional (3D) multi-scale finite element model is developed. It allows affecting specific behaviors to matrix and inclusions. For the former, where mass transports occur within the connected porous network, a three-fluids approach (liquid water, vapor and dry air) is adopted and is coupled to a poro-mechanical damage based approach. For inclusions (aggregates) no hygral component arises a pure thermo-mechanical model is considered. The developed model is then used to investigate, either by 2D or 3D numerical simulations, effects of mineralogical nature, morphology and distribution of aggregates. Studied effects have mainly concerned the influence of these parameters on local fluctuations of simulated temperature, gas pressure and damage fields with regard to experimentally observed dispersion. The

  1. The importance of Thermo-Hydro-Mechanical couplings and microstructure to strain localization in 3D continua with application to seismic faults. Part I: Theory and linear stability analysis

    Science.gov (United States)

    Rattez, Hadrien; Stefanou, Ioannis; Sulem, Jean

    2018-06-01

    A Thermo-Hydro-Mechanical (THM) model for Cosserat continua is developed to explore the influence of frictional heating and thermal pore fluid pressurization on the strain localization phenomenon. A general framework is presented to conduct a bifurcation analysis for elasto-plastic Cosserat continua with THM couplings and predict the onset of instability. The presence of internal lengths in Cosserat continua enables to estimate the thickness of the localization zone. This is done by performing a linear stability analysis of the system and looking for the selected wavelength corresponding to the instability mode with fastest finite growth coefficient. These concepts are applied to the study of fault zones under fast shearing. For doing so, we consider a model of a sheared saturated infinite granular layer. The influence of THM couplings on the bifurcation state and the shear band width is investigated. Taking representative parameters for a centroidal fault gouge, the evolution of the thickness of the localized zone under continuous shear is studied. Furthermore, the effect of grain crushing inside the shear band is explored by varying the internal length of the constitutive law.

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

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Y.J.; Tang, A.M.; Loiseau, C.; Delage, P.; Polak, M.; Souli, H.; Fleureau, J.M.; Wu, P.L.; Tien, Y.M.; Romero, E.; LI, Xiang Ling; Tanaka, Y.; Hasegawa, T.; Nakamura, K.; Sahara, F.; Murakami, T.; Kobayashi, I.; Mihara, M.; Ohi, T.; Lu, J.D.; Huang, W.H.; Lee, W.Y.; Sui, I.H.; Villar, M.V.; Sanchez, M.; Gens, A.; Samper, J.; Lu, C.; Montenegro, L.; Birgersson, M.; Karnland, O.; Nilsson, U.; Akesson, M.; Kristensson, O.; Gatabin, C.; Yang, C.R.; Huang, W.H.; Hsiao, T.H.; Dueck, A.; Lonnqvist, M.; Goudarzi, R.; Borgesson, L.; Fernandez, A.M.; Rivas, P.; Melon, A.M.; Villar, M.V.; Ferrow, E.; Bender Koch, Ch.; Suzuki, S.; Sazarashi, M.; Takegahara, T.; Takao, H.; Tanai, K.; Matsumoto, K.; Gatabin, C.; Touze, G.; Imbert, C.; Guillot, W.; Billaud, P

    2007-07-01

    This session gathers 24 articles (posters) dealing with: determining water permeability of a compacted bentonite sand mixture under confined and free-swell conditions; the model prediction of engineered barrier system effectiveness in the fracture at laboratory scale; the changes in the hydraulic properties of a smectite in presence of chromium; the wall friction and ejection behaviour of bentonite-base buffer material; the thermo-hydro-mechanical behaviour of a large scale mock-up test 'Ophelie' in Belgium: laboratory characterization and numerical modelling; modeling swelling characteristics and permeability of several compacted bentonite affected by saline water; modelling for the long-term Mechanical and Hydraulic behaviour of bentonite-based materials considering chemical transitions; the coupled thermal-hydro analysis on partially saturated bentonite; the behaviour of a bentonite barrier in the laboratory: experimental results up to 8 years and numerical simulation; a coupled hydrogeochemical calculations of the interactions of corrosion products and bentonite; the freezing in saturated bentonite: a thermodynamic approach; the mechanical modeling of MX-80: Development of constitutive laws; the mechanical modeling of MX-80 - Quick tools for BBM parameter analysis; TBT{sub 3} Mock-up test-experimental and model results; the suction characteristics of two compacted bentonite; the retention curves and volume change properties of unsaturated MX-80 bentonite: a laboratory study; humidity induced swelling and water absorption rate of highly compacted bentonite; unconfined compression tests on bentonite samples exposed to high temperature during long time in the field test lot; the thermophysical properties of bentonite; the geochemistry and mineralogy of a bentonite subjected to heating and hydration in an in-situ test after five years operation; the LOT project, long term test of buffer material at Aespoe: a Moessbauer spectroscopic study; the self

  3. Development of finite element code for the analysis of coupled thermo-hydro-mechanical behaviors of saturated-unsaturated medium

    International Nuclear Information System (INIS)

    Ohnishi, Y.; Shibata, H.; Kobayashi, A.

    1985-01-01

    A model is presented which describes fully coupled thermo-hydro-mechanical behavior of porous geologic medium. The mathematical formulation for the model utilizes the Biot theory for the consolidation and the energy balance equation. The medium is in the condition of saturated-unsaturated flow, then the free surfaces are taken into consideration in the model. The model, incorporated in a finite element numerical procedure, was implemented in a two-dimensional computer code. The code was developed under the assumptions that the medium is poro-elastic and in plane strain condition; water in the ground does not change its phase; heat is transferred by conductive and convective flow. Analytical solutions pertaining to consolidation theory for soils and rocks, thermoelasticity for solids and hydrothermal convection theory provided verification of stress and fluid flow couplings, respectively in the coupled model. Several types of problems are analyzed. The one is a study of some of the effects of completely coupled thermo-hydro-mechanical behavior on the response of a saturated-unsaturated porous rock containing a buried heat source. Excavation of an underground opening which has radioactive wastes at elevated temperatures is modeled and analyzed. The results shows that the coupling phenomena can be estimated at some degree by the numerical procedure. The computer code has a powerful ability to analyze of the repository the complex nature of the repository

  4. A three-dimensional coupled thermo-hydro-mechanical model for deformable fractured geothermal systems

    DEFF Research Database (Denmark)

    Salimzadeh, Saeed; Paluszny, Adriana; Nick, Hamidreza M.

    2018-01-01

    A fully coupled thermal-hydraulic-mechanical (THM) finite element model is presented for fractured geothermal reservoirs. Fractures are modelled as surface discontinuities within a three-dimensional matrix. Non-isothermal flow through the rock matrix and fractures are defined and coupled to a mec......A fully coupled thermal-hydraulic-mechanical (THM) finite element model is presented for fractured geothermal reservoirs. Fractures are modelled as surface discontinuities within a three-dimensional matrix. Non-isothermal flow through the rock matrix and fractures are defined and coupled....... The model has been validated against several analytical solutions, and applied to study the effects of the deformable fractures on the injection of cold water in fractured geothermal systems. Results show that the creation of flow channelling due to the thermal volumetric contraction of the rock matrix...

  5. Thermo-hydro-mechanical processes in the nearfield around a HLW repository in argillaceous formations. Vol. II. In-situ-investigations and interpretative modelling. May 2007 to May 2013

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Chun-Liang; Czaikowski, Oliver; Komischke, Michael; Wieczorek, Klaus

    2014-06-15

    Deep disposal of heat-emitting high-level radioactive waste (HLW) in clay formations will inevitably induce thermo-hydro-mechanical-chemical disturbances to the host rock and engineered barriers over very long periods of time. The responses and resulting property changes of the natural and engineered barriers are to be well understood, characterized, and predicted for assessing the long-term performance and safety of the repositories. In accordance with the R and D programme defined by the German Federal Ministry of Economics and Technology (BMWi), GRS has intensively performed site-independent research work on argillaceous rocks during the last decade. Most of the investigations have been carried out on the Callovo-Oxfordian argillite and the Opalinus clay by par-ticipation in international research projects conducted at the underground research laboratories at Bure in France (MHM-URL) and Mont-Terri in Switzerland (MT-URL). The THM-TON project, which was funded by BMWi under contract number 02E10377, in-vestigated the THM behaviours of the clay host rock and clay-based backfill/sealing materials with laboratory tests, in situ experiments and numerical modelling.

  6. Thermo-hydro-mechanical simulation of a 3D fractured porous rock: preliminary study of coupled matrix-fracture hydraulics

    International Nuclear Information System (INIS)

    Canamon, I.; Javier Elorza, F.; Ababou, R.

    2007-01-01

    We present a problem involving the modeling of coupled flow and elastic strain in a 3D fractured porous rock, which requires prior homogenization (up-scaling) of the fractured medium into an equivalent Darcian anisotropic continuum. The governing equations form a system of PDE's (Partial Differential Equations) and, depending on the case being considered, this system may involve two different types of 'couplings' (in a real system, both couplings (1) and (2) generally take place): 1) Hydraulic coupling in a single (no exchange) or in a dual matrix-fracture continuum (exchange); 2) Thermo-Hydro-Mechanical interactions between fluid flow, pressure, elastic stress, strain, and temperature. We present here a preliminary model and simulation results with FEMLAB R , for the hydraulic problem with anisotropic heterogeneous coefficients. The model is based on data collected at an instrumented granitic site (FEBEX project) for studying a hypothetical nuclear waste repository at the Grimsel Test Site in the Swiss Alps. (authors)

  7. Thermo-hydro-mechanical behaviour of Boom clay; Comportement thermo-hydro-mecanique de l'argile de Boom

    Energy Technology Data Exchange (ETDEWEB)

    Le, T.T

    2008-01-15

    This thesis studied the thermo-hydro-mechanical properties of Boom clay, which was chosen to be the host material for the radioactive waste disposal in Mol, Belgium. Firstly, the research was concentrated on the soil water retention properties and the hydro-mechanical coupling by carrying out axial compression tests with suction monitoring. The results obtained permitted elaborating a rational experimental procedure for triaxial tests. Secondly, the systems for high pressure triaxial test at controlled temperature were developed to carry out compression, heating, and shearing tests at different temperatures. The obtained results showed clear visco-elasto-plastic behaviour of the soil. This behaviour was modelled by extending the thermo-elasto-plastic model of Cui et al. (2000) to creep effect. (author)

  8. 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

  9. Investigation of the THM behaviour of the buffer and rock-buffer interaction during the canister retrieval test performed in the ASPÖ Hard Rock Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Millard, A., E-mail: alain.millard@cea.fr [CEA, DEN, DANS, DM2S, SEMT, LM2S, F91191 Gif sur Yvette (France); Barnichon, J.D. [IRSN/DEI/SARG/LR2S, F-92260 Fontenay-aux-Roses (France)

    2014-04-01

    In the framework of the THERESA European project, numerical modelling of coupled thermo-hydro-mechanical (THM) and thermo-hydro-mechanical-chemical (THMC) behaviour of buffer (bentonite) and buffer-rock interfaces for deep underground nuclear waste repositories has been undertaken, with focus on the performance assessments. A major step of the project was the analysis of a large scale test, called the Canister Retrieval test, which has been performed in Aspö Hard Rock Laboratory. It consists in a full scale test of the emplacement of a canister with the surrounding buffer material. A deposition hole was first bored, and then the canister with heaters was installed together with bentonite blocks. The gap between the rock and the bentonite blocks was filled with bentonite pellets. The whole set was artificially wetted from its external boundary in order to accelerate the expected natural rehydration by the surrounding rock. The evolution of the THM processes was recorded over 5 years. Before analysing the whole CRT experiment, a preliminary simpler problem has been defined, which consisted in modelling a disc of buffer at canister mid-height. Thanks to the available experimental recorded measurements, it has been possible to numerically investigate the respective influence of the various THM parameters involved in the modelling of the physical processes. The theoretical model is based on one hand on the Richard's approximation for the flow calculation, and on the other hand on a Biot's type model for the hydro-mechanical behaviour. It has revealed the large influence of the liquid relative permeability, which is unfortunately in general not directly available from experiments and must be determined through inverse analysis techniques. Then, in a second stage, the whole CRT experiment has been analysed. For simplicity reasons, an axisymetrical model has been adopted, although the presence of a neighbouring experiment did influence the CRT results. The

  10. Basic rock properties for the thermo-hydro-mechanical analysis of a high-level radioactive waste repository

    International Nuclear Information System (INIS)

    Kim, Jhin Wung; Kang, Chul Hyung

    1999-04-01

    Deep geological radioactive waste disposal is generally based on the isolation of the waste from the biosphere by multiple barriers. The host rock is one of these barriers which should provide a stable mechanical and chemical environment for the engineered barriers. In the evaluation of the safety of the high-level radioactive waste disposal systems, an important part of the safety analysis is an assessment of the coupling or interaction between thermal, hydrological, and mechanical effects. In order to do this assessment, adequate data on the characteristics of different host rocks are necessary. The properties of the rock and rock discontinuity are very complex and their values vary in a wide range. The accuracy of the result of the assessment depends on the values of these properties used. The present study is an attempt to bring together and condense data for the basic properties of various rock masses, which are needed in the thermo-hydro-mechanical analysis for the deep geological radioactive waste repository. The testing and measurement methods for these basic properties are also presented. Domestic data for deep geological media should be supplemented in the future, due to the insufficiency and the lack of accuracy of the data available at present. (author). 28 refs., 21 figs

  11. Thermo-hydro-mechanical simulation of a 3D fractured porous rock: preliminary study of coupled matrix-fracture hydraulics

    Energy Technology Data Exchange (ETDEWEB)

    Canamon, I.; Javier Elorza, F. [Universidad Politecnica de Madrid, Dept. de Matematica Aplicada y Metodos Informaticas, ETSI Minas (UPM) (Spain); Ababou, R. [Institut de Mecanique des Fluides de Toulouse (IMFT), 31 (France)

    2007-07-01

    We present a problem involving the modeling of coupled flow and elastic strain in a 3D fractured porous rock, which requires prior homogenization (up-scaling) of the fractured medium into an equivalent Darcian anisotropic continuum. The governing equations form a system of PDE's (Partial Differential Equations) and, depending on the case being considered, this system may involve two different types of 'couplings' (in a real system, both couplings (1) and (2) generally take place): 1) Hydraulic coupling in a single (no exchange) or in a dual matrix-fracture continuum (exchange); 2) Thermo-Hydro-Mechanical interactions between fluid flow, pressure, elastic stress, strain, and temperature. We present here a preliminary model and simulation results with FEMLAB{sup R}, for the hydraulic problem with anisotropic heterogeneous coefficients. The model is based on data collected at an instrumented granitic site (FEBEX project) for studying a hypothetical nuclear waste repository at the Grimsel Test Site in the Swiss Alps. (authors)

  12. Basic rock properties for the thermo-hydro-mechanical analysis of a high-level radioactive waste repository

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jhin Wung; Kang, Chul Hyung

    1999-04-01

    Deep geological radioactive waste disposal is generally based on the isolation of the waste from the biosphere by multiple barriers. The host rock is one of these barriers which should provide a stable mechanical and chemical environment for the engineered barriers. In the evaluation of the safety of the high-level radioactive waste disposal systems, an important part of the safety analysis is an assessment of the coupling or interaction between thermal, hydrological, and mechanical effects. In order to do this assessment, adequate data on the characteristics of different host rocks are necessary. The properties of the rock and rock discontinuity are very complex and their values vary in a wide range. The accuracy of the result of the assessment depends on the values of these properties used. The present study is an attempt to bring together and condense data for the basic properties of various rock masses, which are needed in the thermo-hydro-mechanical analysis for the deep geological radioactive waste repository. The testing and measurement methods for these basic properties are also presented. Domestic data for deep geological media should be supplemented in the future, due to the insufficiency and the lack of accuracy of the data available at present. (author). 28 refs., 21 figs.

  13. The importance of Thermo-Hydro-Mechanical couplings and microstructure to strain localization in 3D continua with application to seismic faults. Part II: Numerical implementation and post-bifurcation analysis

    Science.gov (United States)

    Rattez, Hadrien; Stefanou, Ioannis; Sulem, Jean; Veveakis, Manolis; Poulet, Thomas

    2018-06-01

    In this paper we study the phenomenon of localization of deformation in fault gouges during seismic slip. This process is of key importance to understand frictional heating and energy budget during an earthquake. A infinite layer of fault gouge is modeled as a Cosserat continuum taking into account Thermo-Hydro-Mechanical (THM) couplings. The theoretical aspects of the problem are presented in the companion paper (Rattez et al., 2017a), together with a linear stability analysis to determine the conditions of localization and estimate the shear band thickness. In this Part II of the study, we investigate the post-bifurcation evolution of the system by integrating numerically the full system of non-linear equations using the method of Finite Elements. The problem is formulated in the framework of Cosserat theory. It enables to introduce information about the microstructure of the material in the constitutive equations and to regularize the mathematical problem in the post-localization regime. We emphasize the influence of the size of the microstructure and of the softening law on the material response and the strain localization process. The weakening effect of pore fluid thermal pressurization induced by shear heating is examined and quantified. It enhances the weakening process and contributes to the narrowing of shear band thickness. Moreover, due to THM couplings an apparent rate-dependency is observed, even for rate-independent material behavior. Finally, comparisons show that when the perturbed field of shear deformation dominates, the estimation of the shear band thickness obtained from linear stability analysis differs from the one obtained from the finite element computations, demonstrating the importance of post-localization numerical simulations.

  14. Coupled Thermo-Hydro-Mechanical-Chemical Modeling of Water Leak-Off Process during Hydraulic Fracturing in Shale Gas Reservoirs

    Directory of Open Access Journals (Sweden)

    Fei Wang

    2017-11-01

    Full Text Available The water leak-off during hydraulic fracturing in shale gas reservoirs is a complicated transport behavior involving thermal (T, hydrodynamic (H, mechanical (M and chemical (C processes. Although many leak-off models have been published, none of the models fully coupled the transient fluid flow modeling with heat transfer, chemical-potential equilibrium and natural-fracture dilation phenomena. In this paper, a coupled thermo-hydro-mechanical-chemical (THMC model based on non-equilibrium thermodynamics, hydrodynamics, thermo-poroelastic rock mechanics, and non-isothermal chemical-potential equations is presented to simulate the water leak-off process in shale gas reservoirs. The THMC model takes into account a triple-porosity medium, which includes hydraulic fractures, natural fractures and shale matrix. The leak-off simulation with the THMC model involves all the important processes in this triple-porosity medium, including: (1 water transport driven by hydraulic, capillary, chemical and thermal osmotic convections; (2 gas transport induced by both hydraulic pressure driven convection and adsorption; (3 heat transport driven by thermal convection and conduction; and (4 natural-fracture dilation considered as a thermo-poroelastic rock deformation. The fluid and heat transport, coupled with rock deformation, are described by a set of partial differential equations resulting from the conservation of mass, momentum, and energy. The semi-implicit finite-difference algorithm is proposed to solve these equations. The evolution of pressure, temperature, saturation and salinity profiles of hydraulic fractures, natural fractures and matrix is calculated, revealing the multi-field coupled water leak-off process in shale gas reservoirs. The influences of hydraulic pressure, natural-fracture dilation, chemical osmosis and thermal osmosis on water leak-off are investigated. Results from this study are expected to provide a better understanding of the

  15. Multi-scale modelling and simulation of the thermo-hydro-mechanical behavior of concrete with explicit representation of cracking

    International Nuclear Information System (INIS)

    Tognevi, Amen

    2012-01-01

    The concrete structures of nuclear power plants can be subjected to moderate thermo-hydric loadings characterized by temperatures of the order of hundred of degrees in service conditions as well as in accidental ones. These loadings can be at the origin of important disorders, in particular cracking which accelerate hydric transfers in the structure. In the framework of the study of durability of these structures, a coupled thermo-hydro-mechanical model denoted THMs has been developed at Laboratoire d'Etude du Comportement des Betons et des Argiles (LECBA) of CEA Saclay in order to perform simulations of the concrete behavior submitted to such loadings. In this work, we focus on the improvement in the model THMs in one hand of the assessment of the mechanical and hydro-mechanical parameters of the unsaturated micro-cracked material and in the other hand of the description of cracking in terms of opening and propagation. The first part is devoted to the development of a model based on a multi-scale description of cement-based materials starting from the scale of the main hydrated products (portlandite, ettringite, C-S-H etc.) to the macroscopic scale of the cracked material. The investigated parameters are obtained at each scale of the description by applying analytical homogenization techniques. The second part concerns a fine numerical description of cracking. To this end, we choose to use combined finite element and discrete element methods. This procedure is presented and illustrated through a series of mechanical tests in order to show the feasibility of the method and to proceed to its validation. Finally, we apply the procedure to a heated wall and the proposed method for estimating the permeability shows the interest to take into account an anisotropic permeability tensor when dealing with mass transfers in cracked concrete structures. (author) [fr

  16. Study of the water retention and the consolidation of partially saturated soils in a thermo-hydro-mechanical framework

    International Nuclear Information System (INIS)

    Salager, Simon

    2007-01-01

    This work is concerned with the study of water retention and consolidation of unsaturated soils in a thermo-hydro-mechanical framework. It is organized into two parts which deal respectively with deformation and temperature effects on hydric behaviour, and suction and temperature effects on mechanical behaviour. In the first part, we point out the relevance of the characteristic surface concept for soils as opposed to the retention curve, which has limited modelling power in the case of deformable media. The characteristic surface concept is experimentally illustrated for the example of a clayey silty sand. Its modelling is based on a large sample of experimental investigations with about 240 measurements of the triplet void ratio, water content, suction. In addition, a thermo-hydric behaviour model is proposed in order to determine the characteristic surface and the retention curve for a given temperature. This model is validated for the case of two materials: a ceramic and a clayey silty sand through direct testing, and for other materials on the basis of an analysis of the literature. Finally, we present an application to the determination of the permeability of unsaturated soils taking into account deformation and temperature. In the second part, temperature and suction effects on the mechanical behaviour are studied through consolidation tests on 'Sion' silt. These tests are performed for different temperatures and suctions. For each test, swelling and compression indexes, as well as the pre-consolidation pressure are measured. The influence of temperature and suction on these essential parameters of mechanical behaviour is determined. Finally, we propose a theoretical model which account for pre-consolidation pressure as a function of temperature and suction. (author)

  17. The coupled process laboratory test of highly compacted bentonite

    International Nuclear Information System (INIS)

    Shen Zhenyao; Li Guoding; Li Shushen; Wang Chengzu

    2004-01-01

    Highly compacted bentonite blocks have been heated and hydrated in the laboratory in order to simulate the thermo-hydro-mechanical (THM) coupled processes of buffer material in a high-level radioactive waste (HLW) repository. The experiment facility, which is composed of experiment barrel, heated system, high pressure water input system, temperature measure system, water content measure system and swelling stress system, is introduced in this paper. The steps of the THM coupled experiment are also given out in detail. There are total 10 highly compacted bentonite blocks used in this test. Experimental number 1-4 are the tests with the heater and the hydrated process, which temperature distribution vs. time and final moisture distribution are measured. Experimental number 5-8 are the tests with the heater and without the hydrated process, which temperature distribution vs. time and final moisture distribution are measured. Experimental number 9-10 are the tests with the heater and the hydrated process, which temperature distribution vs. time, final moisture distribution and the swelling stress distribution at some typical points vs. time are measured. The maximum test time is nearly 20 days and the minimum test time is only 8 hours. The results show that the temperature field is little affected by hydration process and stress condition, but moisture transport and stress distribution are a little affected by the thermal gradient. The results also show that the water head difference is the mainly driving force of hydration process and the swelling stress is mainly from hydration process. It will great help to understand better about heat and mass transfer in porous media and the THM coupled process in actual HLW disposal. (author)

  18. Modelling of thermo-hydro-mechanical couplings and damage of viscoplastic rocks in the context of radioactive waste storage; Modelisation des couplages thermo-hydro-mecaniques et de l'endommagement des roches viscoplastiques dans le contexte du stockage de dechets radioactifs

    Energy Technology Data Exchange (ETDEWEB)

    Kharkhour, H

    2002-12-01

    Trying to develop a model taking into account the complex rheology of a geologic media characterized by visco-plasticity, damage and thermo-hydro-mechanical couplings is unusual in geotechnics. This is not the case for radioactive waste storage that presents specificities from several viewpoints. Indeed, the scales of time and space concerned by this type of storage are disproportionate to those of civil engineering works or mines. Another specificity of the radioactive waste storage lies in the coupled processes involved. No effect likely to compromise the long-term security of the storage could be ignored. For example this is the case of damage, a phenomenon which does not necessarily lead to a major change of the mechanical behavior of the works but can influence the permeability of the medium in relation with a migration of radionuclides. It can be conceived that this phenomenon finds all its importance in the context of the thermo-hydro-mechanical couplings of a waste storage with high activity. However, the interaction between the damage and the THM coupled processes was the object of very few research subject up to now. This. is even more true for viscoplastic media considered as ductile, and therefore, less prone to cracking than brittle media. It is exactly in this 'original' but difficult context that took place the research presented in this report. This study was dedicated to the analysis of the phenomena and the thermal, hydraulic and mechanical couplings occurring in the near and far field of a high activity radioactive waste storage. Two examples of geological media were considered in this report: the clayey rock of Callovo-Oxfordian, called ' Argilites de l'Est ', target rock of the ANDRA project to carry out a subterranean laboratory for the study of long life radioactive waste storage; and the salt rock of the. subterranean laboratory in the old salt mine of Asse in Germany. (author)

  19. 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

  20. OpenGeoSys: An Open-Source Initiative for Numerical Simulation of Thermo-Hydro-Mechanical/Chemical (THM/C) Processes in Porous Media

    Science.gov (United States)

    Watanabe, N.; Bilke, L.; Fischer, T.; Kalbacher, T.; Nagel, T.; Naumov, D.; Rink, K.; Shao, H.; Wang, W.; Kolditz, O.

    2014-12-01

    The current understanding of geochemical reactions in reservoirs for geological carbon sequestration (GCS) is largely based on aqueous chemistry (CO2 dissolves in reservoir brine and brine reacts with rocks). However, only a portion of the injected supercritical (sc) CO2 dissolves before the buoyant plume contacts caprock, where it is expected to reside for a long time. Although numerous studies have addressed scCO2-mineral reactions occurring within adsorbed aqueous films, possible reactions resulting from direct CO2-rock contact remain less understood. Does CO2 as a supercritical phase react with reservoir rocks? Do mineral react differently with scCO2 than with dissolved CO2? We selected muscovite, one of the more stable and common rock-forming silicate minerals, to react with scCO2 phase (both water-saturated and water-free) and compared with CO2-saturated-brine. The reacted basal surfaces were analyzed using atomic force microscopy and X-ray photoelectron spectroscopy for examining the changes in surface morphology and chemistry. The results show that scCO2 (regardless of its water content) altered muscovite considerably more than CO2-saturated brine; suggest CO2 diffusion into mica interlayers and localized mica dissolution into scCO2 phase. The mechanisms underlying these observations and their implications for GCS need further exploration.

  1. Advances on experimental techniques for the characterization of THM behaviour of bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Villar, M.V. [CIEMAT - Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT), Madrid (Spain); Lioret, A. [Universidad Politecnica de Cataluna (UPC), Barcelona (Spain)

    2005-07-01

    The design of high level radioactive waste (HLW) repositories in deep geological media in which bentonite clay is proposed as a sealing material leads to the need of further studying the behaviour of highly compacted expansive soils when subjected to mechanical, hydraulic and thermal changes. Laboratory tests may help to understand the processes that take place in the clay barrier under simple and controlled conditions and to develop the governing equations. The laboratory tests enable to isolate the different processes, making their interpretation easier, and provide with fundamental data concerning the parameters to be used in the models. The extremely low permeability of these materials, their avidity for water (high suction) and their high swelling capacity make necessary the modification of the conventional laboratory techniques and procedures to determine basic physical parameters. The main hydraulic properties of the barrier to be considered are the permeability and the water retention capacity. Among the mechanical properties of bentonites, the most outstanding is their capacity to change volume and thus, the characterisation and measurement of swelling pressure, swelling under load and mechanical compressibility are keystones to understand the behaviour of expansive materials. Besides, since the barrier will be subjected to thermal and hydraulic gradients, the variation of its mechanical and hydraulic characteristics with temperature and suction must be known. (authors)

  2. Effect of the heating rate on residual thermo-hydro-mechanical properties of a high-strength concrete in the context of nuclear waste storage

    International Nuclear Information System (INIS)

    Galle, C.; Pin, M.; Ranc, G.; Rodrigues, S.

    2003-01-01

    Concrete is likely to be used in massive structures for nuclear waste long-term storage facilities in France. In the framework of vitrified waste and spent fuel management, these structures could be submitted to high temperatures. In standard conditions, ambient temperature should not exceed 60 degC but in case of failure of a cooling system, concretes could be temporarily exposed to temperatures up to 250 degC. Depending on the temperature rise kinetics, concretes could be damaged to a greater or lesser extent. In this context, an experimental study on the effect of heating rate on concrete thermo-hydro-mechanical properties exposed to high temperatures (110 - 250 degC) was carried out at the French Atomic Energy Commission (CEA). Data analysis and interpretation provided enough arguments to conclude that, at local scale, the impact of heating rate on residual properties was real though relatively limited. (author)

  3. Development of finite element code for the analysis of coupled thermo-hydro-mechanical behaviors of a saturated-unsaturated medium

    International Nuclear Information System (INIS)

    Ohnishi, Y.; Shibata, H.; Kobsayashi, A.

    1987-01-01

    A model is presented which describes fully coupled thermo-hydro-mechanical behavior of a porous geologic medium. The mathematical formulation for the model utilizes the Biot theory for the consolidation and the energy balance equation. If the medium is in the condition of saturated-unsaturated flow, then the free surfaces are taken into consideration in the model. The model, incorporated in a finite element numerical procedure, was implemented in a two-dimensional computer code. The code was developed under the assumptions that the medium is poro-elastic and in the plane strain condition; that water in the ground does not change its phase; and that heat is transferred by conductive and convective flow. Analytical solutions pertaining to consolidation theory for soils and rocks, thermoelasticity for solids and hydrothermal convection theory provided verification of stress and fluid flow couplings, respectively, in the coupled model. Several types of problems are analyzed

  4. Numerical Analysis of a Class of THM Coupled Model for Porous Materials

    Science.gov (United States)

    Liu, Tangwei; Zhou, Jingying; Lu, Hongzhi

    2018-01-01

    We consider the coupled models of the Thermo-hydro-mechanical (THM) problem for porous materials which arises in many engineering applications. Firstly, mathematical models of the THM coupled problem for porous materials were discussed. Secondly, for different cases, some numerical difference schemes of coupled model were constructed, respectively. Finally, aassuming that the original water vapour effect is neglectable and that the volume fraction of liquid phase and the solid phase are constants, the nonlinear equations can be reduced to linear equations. The discrete equations corresponding to the linear equations were solved by the Arnodli method.

  5. A Thermo-Hydro-Mechanical coupled Numerical modeling of Injection-induced seismicity on a pre-existing fault

    Science.gov (United States)

    Kim, Jongchan; Archer, Rosalind

    2017-04-01

    In terms of energy development (oil, gas and geothermal field) and environmental improvement (carbon dioxide sequestration), fluid injection into subsurface has been dramatically increased. As a side effect of these operations, a number of injection-induced seismic activities have also significantly risen. It is known that the main causes of induced seismicity are changes in local shear and normal stresses and pore pressure as well. This mechanism leads to increase in the probability of earthquake occurrence on permeable pre-existing fault zones predominantly. In this 2D fully coupled THM geothermal reservoir numerical simulation of injection-induced seismicity, we investigate the thermal, hydraulic and mechanical behavior of the fracture zone, considering a variety of 1) fault permeability, 2) injection rate and 3) injection temperature to identify major contributing parameters to induced seismic activity. We also calculate spatiotemporal variation of the Coulomb stress which is a combination of shear stress, normal stress and pore pressure and lastly forecast the seismicity rate on the fault zone by computing the seismic prediction model of Dieterich (1994).

  6. Multi-scale modeling of the thermo-hydro- mechanical behaviour of heterogeneous materials. Application to cement-based materials under severe loads

    International Nuclear Information System (INIS)

    Grondin, Frederic Alain

    2005-01-01

    The work of modeling presented here relates to the study of the thermo-hydro- mechanical behaviour of porous materials based on hydraulic binder such as concrete, High Performance Concrete or more generally cement-based materials. This work is based on the exploitation of the Digital Concrete model, of the finite element code Symphonie developed in the Scientific and Technical Centre for Building (CSTB), in coupling with the homogenization methods to obtain macroscopic behaviour laws drawn from the Micro-Macro relations. Scales of investigation, macroscopic and microscopic, has been exploited by simulation in order to allow the comprehension fine of the behaviour of cement-based materials according to thermal, hydrous and mechanical loads. It appears necessary to take into account various scales of modeling. In order to study the behaviour of the structure, we are brought to reduce the scale of investigation to study the material more particularly. The research tasks presented suggest a new approach for the identification of the multi-physic behaviour of materials by simulation. In complement of the purely experimental approach, based on observations on the sample with measurements of the apparent parameters on the macroscopic scale, this new approach allows to obtain the fine analysis of elementary mechanisms in acting within the material. These elementary mechanisms are at the origin of the evolution of the macroscopic parameters measured in experimental tests. In this work, coefficients of the thermo-hydro-mechanical behaviour law of porous materials and the equivalent hydraulic conductivity were obtained by a multi-scales approach. Applications has been carried out on the study of the damaged behaviour of cement-based materials, in the objective to determine the elasticity tensor and the permeability tensor of a High Performance Concrete at high temperatures under a mechanical load. Also, the study of the strain evolution of cement-based materials at low

  7. Temperature Buffer Test. Final THM modelling

    International Nuclear Information System (INIS)

    Aakesson, Mattias; Malmberg, Daniel; Boergesson, Lennart; Hernelind, Jan; Ledesma, Alberto; Jacinto, Abel

    2012-01-01

    The Temperature Buffer Test (TBT) is a joint project between SKB/ANDRA and supported by ENRESA (modelling) and DBE (instrumentation), which aims at improving the understanding and to model the thermo-hydro-mechanical behavior of buffers made of swelling clay submitted to high temperatures (over 100 deg C) during the water saturation process. The test has been carried out in a KBS-3 deposition hole at Aespoe HRL. It was installed during the spring of 2003. Two heaters (3 m long, 0.6 m diameter) and two buffer arrangements have been investigated: the lower heater was surrounded by bentonite only, whereas the upper heater was surrounded by a composite barrier, with a sand shield between the heater and the bentonite. The test was dismantled and sampled during the winter of 2009/2010. This report presents the final THM modelling which was resumed subsequent to the dismantling operation. The main part of this work has been numerical modelling of the field test. Three different modelling teams have presented several model cases for different geometries and different degree of process complexity. Two different numerical codes, Code B right and Abaqus, have been used. The modelling performed by UPC-Cimne using Code B right, has been divided in three subtasks: i) analysis of the response observed in the lower part of the test, by inclusion of a number of considerations: (a) the use of the Barcelona Expansive Model for MX-80 bentonite; (b) updated parameters in the vapour diffusive flow term; (c) the use of a non-conventional water retention curve for MX-80 at high temperature; ii) assessment of a possible relation between the cracks observed in the bentonite blocks in the upper part of TBT, and the cycles of suction and stresses registered in that zone at the start of the experiment; and iii) analysis of the performance, observations and interpretation of the entire test. It was however not possible to carry out a full THM analysis until the end of the test due to

  8. Temperature Buffer Test. Final THM modelling

    Energy Technology Data Exchange (ETDEWEB)

    Aakesson, Mattias; Malmberg, Daniel; Boergesson, Lennart; Hernelind, Jan [Clay Technology AB, Lund (Sweden); Ledesma, Alberto; Jacinto, Abel [UPC, Universitat Politecnica de Catalunya, Barcelona (Spain)

    2012-01-15

    The Temperature Buffer Test (TBT) is a joint project between SKB/ANDRA and supported by ENRESA (modelling) and DBE (instrumentation), which aims at improving the understanding and to model the thermo-hydro-mechanical behavior of buffers made of swelling clay submitted to high temperatures (over 100 deg C) during the water saturation process. The test has been carried out in a KBS-3 deposition hole at Aespoe HRL. It was installed during the spring of 2003. Two heaters (3 m long, 0.6 m diameter) and two buffer arrangements have been investigated: the lower heater was surrounded by bentonite only, whereas the upper heater was surrounded by a composite barrier, with a sand shield between the heater and the bentonite. The test was dismantled and sampled during the winter of 2009/2010. This report presents the final THM modelling which was resumed subsequent to the dismantling operation. The main part of this work has been numerical modelling of the field test. Three different modelling teams have presented several model cases for different geometries and different degree of process complexity. Two different numerical codes, Code{sub B}right and Abaqus, have been used. The modelling performed by UPC-Cimne using Code{sub B}right, has been divided in three subtasks: i) analysis of the response observed in the lower part of the test, by inclusion of a number of considerations: (a) the use of the Barcelona Expansive Model for MX-80 bentonite; (b) updated parameters in the vapour diffusive flow term; (c) the use of a non-conventional water retention curve for MX-80 at high temperature; ii) assessment of a possible relation between the cracks observed in the bentonite blocks in the upper part of TBT, and the cycles of suction and stresses registered in that zone at the start of the experiment; and iii) analysis of the performance, observations and interpretation of the entire test. It was however not possible to carry out a full THM analysis until the end of the test due to

  9. Numerical study of the EDZ by a thermo-hydro-mechanical damage model dedicated to unsaturated geo-materials

    International Nuclear Information System (INIS)

    Arson, Chloe; Gatmiri, Behrouz

    2010-01-01

    Document available in extended abstract form only. The design of deep nuclear waste repositories requires the modelling of the effects of thermal loadings in the Excavation Damaged Zone (EDZ). The containers are to be stored in bentonite buffers surrounded by a geological massif. These two barriers are multi-phase porous media, in which coupled mechanical, capillary and thermal phenomena occur. The aim of this study is to develop a new damage model dedicated to non-isothermal unsaturated porous media, the 'THHMD' model. Contrary to almost all of the existing damage models dedicated to non dry media, it is formulated in independent stress state variables (net stress, suction and thermal stress). The damage variable is a second-order tensor, which gives a good approximation for the representation of anisotropic cracking in three dimensions. The behaviour laws stem from the combination of phenomenological and micromechanical principles. The total strain tensor is split into three components, each of which being conjugated to a stress state variable. The Helmholtz free energy is written as the sum of damaged elastic energies and residual-strain-potentials. The concept of effective stress, frequently used in Continuum Damaged Mechanics, is extended to the three stress state variables, by using the operator of Cordebois and Sidoroff. The damaged rigidities are computed by application of the Principle of Equivalent Elastic Energy (PEEE). The non-elastic strain components depend on the increment of damage, which is determined by an associative flow rule. Fracturing is also modelled in the transfer equations. The Representative Elementary Volume (REV) is assumed to be damaged by a microcrack network, among which liquid water and vapour flows are homogenized. A damaged intrinsic conductivity, which plays the role of an internal length parameter, is introduced. The influence of damage on air and heat flows is taken into account by means of porosity, which is also

  10. 裂隙岩体水-冰相变及低温温度场-渗流场-应力场耦合研究%WATER-ICE PHASE TRANSITION AND THERMO-HYDRO-MECHANICAL COUPLING AT LOW TEMPERATURE IN FRACTURED ROCK

    Institute of Scientific and Technical Information of China (English)

    刘泉声; 康永水; 刘滨; 朱元广

    2011-01-01

    The problem of freezing-thawing damage of rock mass involves thermo-hydro-mechanic al(THM) coupling at low temperature. Based on the phase transition theory and the energy conservation principle, the expression of frozen ratio is derived. Using the dual-porosity medium theory, the governing equations of THM coupling of freezing rock are obtained according to the law of mass conservation, the law of energy conservation and the principle of static equilibrium. Finally, considering the influence of freezing process on permeability, an example of fractured tunnel is given to reveal the distribution of temperature field, stress field and pore pressure under THM coupling condition by using the method of equivalent thermal expansion coefficient.%岩体冻融损伤涉及低温环境下温度场、渗流场和应力场的耦合问题.基于水-冰相变理论和能量守恒原理,得出冻结率表达式.运用双重孔隙介质模型理论,根据质量守恒定律、能量守恒定律及静力平衡原理,得出冻结条件下裂隙岩体的温度场-渗流场-应力场(THM)耦合控制方程.最后,通过1个含裂隙隧道低温THM耦合算例,将围岩当作岩块与裂隙介质组成的系统,采用等效热膨胀系数法对夹冰(含水)裂隙的冻胀效应进行模拟,并考虑冻结过程对岩体渗透系数的影响,研究低温THM耦合条件下的温度场、应力场及孔隙压力等的分布规律.

  11. Modelling of the THM-evolution of Olkiluoto nuclear waste repository

    International Nuclear Information System (INIS)

    Toprak, Erdem; Olivella, Sebastia; Mokni, Nadia; Pintado, Xavier

    2012-01-01

    Document available in extended abstract form only. This paper presents preliminary analyses of coupled Thermo-Hydro-Mechanical (THM) processes in the future nuclear waste repository in Olkiluoto (www.posiva.fi). A finite element program Code-Bright is used to perform modeling calculations of disposal tunnels in an underground repository for spent nuclear fuel. The repository will consist of a series of deposition holes in the bedrock. Bentonite buffer rings will surround the copper canisters containing spent fuel. As a protecting and isolating barrier between the waste canisters and the surrounding host rock, MX80 bentonite will be used as buffer material. Friedland clay is considered one of the best candidates to be used as drift backfill material to meet the long-term performance requirements set for backfilling of a disposal tunnel in the repository. Figure 1 shows a cross section of the spent nuclear final disposal facility. The time required for reaching full saturation, maximum temperature reached in canister, deformations in the buffer-backfill interface and stress-deformation balance in this interaction and also modeling of gap between canister and buffer ring are the main issued addressed of this study. A fundamental issue in modeling was to determine relevant thermal boundary conditions so that the details of THM-behavior could be captured by defining proper near-field thermal boundaries. In this study, it has been shown that temperature on the considered close boundaries depends on initial canister power, fuel power decay characteristic and rock thermal properties. The thermal boundary conditions fixed at the THM modeling have been calculated solving the thermal problem for the entire repository with the analytical solution (Ikonen, 2005). With regard to the hydraulic analyses, the time required for full saturation is sensitive to vapor diffusion, hydraulic conductivity and water retention curve of the buffer and the hydraulic conductivity of the rock. A

  12. Integration of THM-experimental work and modelling

    International Nuclear Information System (INIS)

    Pintado, Xavier; Autio, Jorma; Koskinen, Kari

    2010-01-01

    this case, the boundary conditions play an important role because they are not easy to fix. The work ongoing is the small scale laboratory tests. Some thermal, thermo-hydraulic, hydro-mechanical and thermo-hydro-mechanical test are running. The previous scoping calculations allow to have an idea about the time necessary to run the test and the order of magnitude of the variables measured. This experimental work is doing with the MX-80, the clay reference. The scoping calculations allow us to know what parameters control a test. This work can be done under statistical point of view with an accurate analysis of the derivatives of the variables respect the parameters. The results from the small and large scale laboratory tests and the large scale test provide the information necessary for simulate the repository behaviour. As it was mentioned previously, the boundary conditions are quite important because the hydration of the barrier depends on the water contribution from the host rock. The accurate knowledge of the groundwater flow will be quite important to simulate properly the clay barrier. Other boundary conditions have to be considered, like the mechanical contact between different materials (buffer, backfill and host rock) and the behaviour of special parts of the barrier, like the gaps initially filled of air, water or pellets. The future quality control of the repository in the early stages will calibrate the model used for calculate and simulate during the design phase. There is experience in the control of a construction, like in dams, where the properly auscultation during its live is necessary to assure the security of the population. (authors)

  13. Analysis and modeling of coupled thermo-hydro-mechanical phenomena in 3D fractured media; Analyse et modelisation des phenomenes couples thermo-hydromecaniques en milieux fractures 3D

    Energy Technology Data Exchange (ETDEWEB)

    Canamon Valera, I

    2006-11-15

    This doctoral research was conducted as part of a joint France-Spain co-tutelage PhD thesis in the framework of a bilateral agreement between two universities, the Institut National Polytechnique de Toulouse (INPT) and the Universidad Politecnica de Madrid (UPM). It concerns a problem of common interest at the national and international levels, namely, the disposal of radioactive waste in deep geological repositories. The present work is devoted, more precisely, to near-field hydrogeological aspects involving mass and heat transport phenomena. The first part of the work is devoted to a specific data interpretation problem (pressures, relative humidities, temperatures) in a multi-barrier experimental system at the scale of a few meters - the 'Mock-Up Test' of the FEBEX project, conducted in Spain. Over 500 time series are characterized in terms of spatial, temporal, and/or frequency/scale-based statistical analysis techniques. The time evolution and coupling of physical phenomena during the experiment are analyzed, and conclusions are drawn concerning the behavior and reliability of the sensors. The second part of the thesis develops in more detail the 3-Dimensional (3D) modeling of coupled Thermo-Hydro-Mechanical phenomena in a fractured porous rock, this time at the scale of a hundred meters, based on the data of the 'In-Situ Test' of the FEBEX project conducted at the Grimsel Test Site in the Swiss Alps. As a first step, a reconstruction of the 3D fracture network is obtained by Monte Carlo simulation, taking into account through optimization the geomorphological data collected around the FEBEX gallery. The heterogeneous distribution of traces observed on the cylindrical wall of the tunnel is fairly well reproduced in the simulated network. In a second step, we develop a method to estimate the equivalent permeability of a many-fractured block by extending the superposition method of Ababou et al. [1994] to the case where the permeability of

  14. DECOVALEX-THMC Project. Task D. Long-Term Permeability/Porosity Changes in the EDZ and Near Field due to THM and THC Processes in Volcanic and Crystalline-Bentonite Systems. Phase 1 Report

    International Nuclear Information System (INIS)

    Birkholzer, J.; Rutqvist, J.; Sonnenthal, E.; Barr, D.

    2007-02-01

    The general goal of this project is to encourage multidisciplinary interactive and cooperative research on modeling coupled processes in geologic formations in support of the performance assessment for underground storage of radioactive waste. Three multi-year project stages of DECOVALEX have been completed in the past decade, mainly focusing on coupled thermal-hydrological-mechanical processes. Currently, a fourth three-year project stage of DECOVALEX is under way, referred to as DECOVALEX-THMC. THMC stands for Thermal, Hydrological, Mechanical, and Chemical processes. The new project stage aims at expanding the traditional geomechanical scope of the previous DECOVALEX project stages by incorporating geochemical processes important for repository performance. The U.S. Department of Energy (DOE) leads Task D of the new DECOVALEX phase, entitled 'Long-term Permeability/Porosity Changes in the EDZ and Near Field due to THC and THM Processes for Volcanic and Crystalline-Bentonite Systems.' In its leadership role for Task D, DOE coordinates and sets the direction for the cooperative research activities of the international research teams engaged in Task D. The research program developed for Task D of DECOVALEX-THMC involves geomechanical and geochemical research areas. THM and THC processes may lead to changes in hydrological properties that are important for performance because the flow processes in the vicinity of emplacement tunnels will be altered from their initial state. Some of these changes can be permanent (irreversible), in which case they persist after the thermal conditions have returned to ambient; i.e., they will affect the entire regulatory compliance period. Geochemical processes also affect the water and gas chemistry close to the waste packages, which are relevant for waste package corrosion, buffer stability, and radionuclide transport. Research teams participating in Task D evaluate long-term THM and THC processes in two generic geologic

  15. DECOVALEX-THMC Project. Task D. Long-Term Permeability/Porosity Changes in the EDZ and Near Field due to THM and THC Processes in Volcanic and Crystalline-Bentonite Systems. Phase 1 Report

    Energy Technology Data Exchange (ETDEWEB)

    Birkholzer, J.; Rutqvist, J.; Sonnenthal, E. [Lawrence Berkeley National Laboratory, CA (United States); Barr, D. [Office of Repository Development, DOE (United States)

    2007-02-15

    The general goal of this project is to encourage multidisciplinary interactive and cooperative research on modeling coupled processes in geologic formations in support of the performance assessment for underground storage of radioactive waste. Three multi-year project stages of DECOVALEX have been completed in the past decade, mainly focusing on coupled thermal-hydrological-mechanical processes. Currently, a fourth three-year project stage of DECOVALEX is under way, referred to as DECOVALEX-THMC. THMC stands for Thermal, Hydrological, Mechanical, and Chemical processes. The new project stage aims at expanding the traditional geomechanical scope of the previous DECOVALEX project stages by incorporating geochemical processes important for repository performance. The U.S. Department of Energy (DOE) leads Task D of the new DECOVALEX phase, entitled 'Long-term Permeability/Porosity Changes in the EDZ and Near Field due to THC and THM Processes for Volcanic and Crystalline-Bentonite Systems.' In its leadership role for Task D, DOE coordinates and sets the direction for the cooperative research activities of the international research teams engaged in Task D. The research program developed for Task D of DECOVALEX-THMC involves geomechanical and geochemical research areas. THM and THC processes may lead to changes in hydrological properties that are important for performance because the flow processes in the vicinity of emplacement tunnels will be altered from their initial state. Some of these changes can be permanent (irreversible), in which case they persist after the thermal conditions have returned to ambient; i.e., they will affect the entire regulatory compliance period. Geochemical processes also affect the water and gas chemistry close to the waste packages, which are relevant for waste package corrosion, buffer stability, and radionuclide transport. Research teams participating in Task D evaluate long-term THM and THC processes in two generic geologic

  16. DECOVALEX-THMC Task D: Long-Term Permeability/Porosity Changes in the EDZ and Near Field due to THM and THC Processes in Volcanic and Crystalline-Bentonite Systems, Status Report October 2005

    International Nuclear Information System (INIS)

    Birkholzer, J.; Rutqvist, J.; Sonnenthal, E.; Barr, D.

    2005-01-01

    The DECOVALEX project is an international cooperative project initiated by SKI, the Swedish Nuclear Power Inspectorate, with participation of about 10 international organizations. The name DECOVALEX stands for DEvelopment of COupled models and their VALidation against Experiments. The general goal of this project is to encourage multidisciplinary interactive and cooperative research on modeling coupled processes in geologic formations in support of the performance assessment for underground storage of radioactive waste. Three multi-year project stages of DECOVALEX have been completed in the past decade, mainly focusing on coupled thermal-hydrological-mechanical processes. Currently, a fourth three-year project stage of DECOVALEX is under way, referred to as DECOVALEX-THMC. THMC stands for Thermal, Hydrological, Mechanical, and Chemical processes. The new project stage aims at expanding the traditional geomechanical scope of the previous DECOVALEX project stages by incorporating geochemical processes important for repository performance. The U.S. Department of Energy (DOE) leads Task D of the new DECOVALEX phase, entitled ''Long-term Permeability/Porosity Changes in the EDZ and Near Field due to THC and THM Processes for Volcanic and Crystalline-Bentonite Systems''. In its leadership role for Task D, DOE coordinates and sets the direction for the cooperative research activities of the international research teams engaged in Task D

  17. Behaviour of M X-80 Bentonite at Unsaturated Conditions and under Thermo-Hydraulic Gradient - Work Performed by CIEMAT in the Context of the TB T Project - Behaviour of M X-80 Bentonite at Unsaturated Conditions and under Thermo-Hydraulic Gradient - Work Performed by CIEMAT in the Context of the TB T Project -

    Energy Technology Data Exchange (ETDEWEB)

    Villar, M.V.; Gomez-Espina, R.; Martin, P.L.

    2006-07-01

    This document reports the thermo-hydro-mechanical characterisation of the MX-80 bentonite performed at CIEMAT between 2004 and 2006 in the context of the Agreement CIEMAT/CIMNE 04/113. This Agreement took place in the framework of the Temperature Buffer Test (TBT) Project, Whose experimental part is going on at the underground research laboratory of Aspo (Sweden) and in which the MX-80 bentonite is used as sealing material in a large scale test. A methodology has been developed for the determination of retention curves at high temperature, what has allowed checking the decrease of the retention capacity of the bentonite with temperature. Infiltration and infiltration/heating tests have been carried out, some of them with simultaneous measurement of temperature and relative humidity. (Author) 9 refs.

  18. Physical changes in MX-80 bentonite saturated under thermal gradient

    International Nuclear Information System (INIS)

    Villar, Maria Victoria; Gomez-Espina, Roberto; Gutierrez-Nebot, Luis; Campos, Rocio; Barrios, Iciar

    2012-01-01

    Document available in extended abstract form only. This study was developed in the framework of the Temperature Buffer Test (TBT project), which was a full-scale test for HLW disposal that aimed at improving the understanding of the thermo-hydro-mechanical (THM) behaviour of buffers with a temperature around and above 100 deg. C during the water saturation transient. The French organisation ANDRA run this test at the Aespoe HRL in cooperation with SKB (Svensk Kaernbraenslehantering AB 2005). To simulate the conditions of the field test in the laboratory, 20-cm high columns of MX80 bentonite compacted at dry density 1.70 g/cm 3 with an initial water content of 16 percent were submitted in thermo-hydraulic cells to heating and hydration by opposite ends for different periods of time (TH test). The temperature at the bottom of the columns was set at 140 deg. C and on top at 30 C, and deionised water was injected on top at a pressure of 0.01 MPa. The tests were running for 337, 496 and 1510 days. Upon dismantling water content, dry density, specific surface area, porosity and basal spacings, among others, were determined in different positions along the bentonite columns. The strong gradients developed are remarkable. In the shorter tests the water content decreased below the initial value in the 7 cm closest to the heater, whereas in the longer test the decrease below the initial value took place only in the 5 cm closest to the heater. In the remaining part of the columns the water content increased with respect to the initial value, particularly so in the longest test. The dry density along the bentonite changed accordingly, decreasing in the hydrated areas below the initial value and increasing near the heater. The decrease in dry density is due to the swelling of the bentonite upon saturation, while the dry density increase results from the combination of two processes: the compression of the dry areas exerted by the hydrated bentonite, and the shrinkage due to the

  19. Granular MX-80 bentonite as buffer material: a focus on swelling characteristics

    International Nuclear Information System (INIS)

    Rizzi, M.; Laloui, L.; Salager, S.; Marschall, P.

    2010-01-01

    Document available in extended abstract form only. The Swiss High Level Waste (HLW) disposal concept envisages the emplacement of the waste canisters in horizontal tunnels excavated at a depth of several hundred meters in an over-consolidated clay-stone formation. After waste emplacement the disposal tunnels are backfilled with MX-80 granular bentonite. Research activities are presented in this paper, aimed at characterising the geomechanical behaviour of the MX-80 granular bentonite and at providing the theoretical framework for modelling its response to thermo-hydro- mechanical (THM) perturbations. From the experimental point of view, a series of tests has been designed in order to extract constitutive data and to assess the temperature and suction effects on the mechanical behaviour of the bentonite, paying particular attention in the investigation to the swelling behaviour of the material. As for the theoretical framework an elasto-plastic constitutive model has been developed to take into account those coupled processes of stress, capillary pressure, and temperature to which the bentonite will be submitted,. Bentonite is mainly composed of the smectite mineral montmorillonite with a high swelling capacity which may provide sufficient sealing properties to seal the tunnel without gaps and to restore the buffer continuity. In fact, as bentonite hydrates in the repositories it will expand in those areas where it is allowed and will exert a swelling pressure where the material is confined. The results of both confined and free swelling tests are presented. Confined tests are aiming at determining the pressure applied by the material during complete saturation under isochoric conditions, whereas in the free swelling tests the strain on hydration is measured. Some results from confined swelling tests at ambient temperature are presented. The specimen is compacted uniaxially directly in the cells, the initial dry density being chosen in the range between 1.6 and 1

  20. Drift Scale THM Model

    International Nuclear Information System (INIS)

    Rutqvist, J.

    2004-01-01

    This model report documents the drift scale coupled thermal-hydrological-mechanical (THM) processes model development and presents simulations of the THM behavior in fractured rock close to emplacement drifts. The modeling and analyses are used to evaluate the impact of THM processes on permeability and flow in the near-field of the emplacement drifts. The results from this report are used to assess the importance of THM processes on seepage and support in the model reports ''Seepage Model for PA Including Drift Collapse'' and ''Abstraction of Drift Seepage'', and to support arguments for exclusion of features, events, and processes (FEPs) in the analysis reports ''Features, Events, and Processes in Unsaturated Zone Flow and Transport and Features, Events, and Processes: Disruptive Events''. The total system performance assessment (TSPA) calculations do not use any output from this report. Specifically, the coupled THM process model is applied to simulate the impact of THM processes on hydrologic properties (permeability and capillary strength) and flow in the near-field rock around a heat-releasing emplacement drift. The heat generated by the decay of radioactive waste results in elevated rock temperatures for thousands of years after waste emplacement. Depending on the thermal load, these temperatures are high enough to cause boiling conditions in the rock, resulting in water redistribution and altered flow paths. These temperatures will also cause thermal expansion of the rock, with the potential of opening or closing fractures and thus changing fracture permeability in the near-field. Understanding the THM coupled processes is important for the performance of the repository because the thermally induced permeability changes potentially effect the magnitude and spatial distribution of percolation flux in the vicinity of the drift, and hence the seepage of water into the drift. This is important because a sufficient amount of water must be available within a

  1. Geochemical processes and compacted bentonite FEBEX with a thermohydraulic gradient with a thermohydraulic gradient

    International Nuclear Information System (INIS)

    Leguey Jimenez, S.; Cuevas Rodriguez, J.; Martin Barca, M.; Vigil de la Villa Mencia, R.; Ramirez Martin, S.; Garcia Gimenez, R.

    2002-01-01

    At present, the main source of High Level radioactive Waste (HLW) is the electrical energy production during all sep of developing. In almost all the countries with nuclear programs, the option for the final management of HLW is the Deep Geological Repository (DGR), based on the concept of multi barrier. According to this concept, the wastes is isolated from biosphere by the interposition of confinement barrier. In the context of an investigation of the near field for a repository of HLW, the FEBEX Project, a set of laboratory test has been designed to give a better understanding of the thermo-hydro-mechanical and geochemical behaviour of the compacted bentonite as a confinement barrier. The object of these work is to analyse the properties of the bentonite and its behaviour under conditions that will be found in a repository. The precipitation of mineral phases, due to local changes in the chemical equilibrium and the hydration itself, can produce changes in the salinity of the interstitial water and in the microstructural organisation of the clay particles. the hydraulic and mechanical properties of the bentonite can be modified by the special conditions of the barrier. (Author)

  2. Freefem++ in THM analyses of KBS-3 deposition hole

    International Nuclear Information System (INIS)

    Lempinen, A.

    2006-12-01

    The applicability of Freefem++ as a software for thermo-hydro-mechanical analysis of KBS-3V deposition hole was evaluated. Freefem++ is software for multiphysical simulations with finite element method. A set of previously performed analyses were successfully repeated with Freefem++. The only significant problem was to impose unique values for variables at the canister surface. This problem can be circumvented with an iterative method, and it can possibly be solved later, since Freefem++ is opensource software. (orig.)

  3. THM-issues in repository rock. Thermal, mechanical, thermo-mechanical and hydro-mechanical evolution of the rock at the Forsmark and Laxemar sites

    Energy Technology Data Exchange (ETDEWEB)

    Hoekmark, Harald; Loennqvist, Margareta; Faelth, Billy (Clay Technology AB, Lund (Sweden))

    2010-05-15

    The present report addresses aspects of the Thermo-Hydro-Mechanical (THM) evolution of the repository host rock that are of potential importance to the SR-Site safety assessment of a KBS-3 type spent nuclear fuel repository. The report covers the evolution of rock temperatures, rock stresses, pore pressures and fracture transmissivities during the excavation and operational phase, the temperate phase and a glacial cycle on different scales. The glacial cycle is assumed to include a period of pre-glacial permafrost with lowered temperatures and with increased pore pressures in the rock beneath the impermeable permafrost layer. The report also addresses the question of the peak temperature reached during the early temperate phase in the bentonite buffer surrounding the spent fuel canisters. The main text is devoted exclusively to the projected THM evolution of the rock at the Forsmark site in central Sweden. The focus is on the potential for stress-induced failures, i.e. spalling, in the walls of the deposition holes and on changes in the transmissivity of fractures and deformation zones. All analyses are conducted by a combination of numerical tools (3DEC) and analytical solutions. All phases are treated separately and independently of each other, although in reality construction will overlap with heat generation because of the step-by-step excavation/deposition approach with some 50 years between deposition of the first and last canisters. It is demonstrated here that the thermal and thermo-mechanical evolution of the near-field will be independent of heat generated by canisters that were deposited in the past, provided that deposition is made in an orderly fashion, deposition area by deposition area. Peak temperatures and near-field stresses can, consequently, be calculated as if all canisters were deposited simultaneously. The canister and tunnel spacing is specified such that the peak buffer temperature will not exceed 100 deg C in any deposition hole, i.e. not

  4. Geochemical Processes and compacted bentonite FEBEX with a thermohydraulic gradient with a thermohydraulic gradient; Procesos geoquimicos y modificaciones texturales en bentonita FEBEX compactada sometida a un gradiente termohidraulico

    Energy Technology Data Exchange (ETDEWEB)

    Leguey Jimenez, S; Cuevas Rodriguez, J; Martin Barca, M; Vigil de la Villa Mencia, R.; Ramirez Martin, S; Garcia Gimenez, R [Universidad Autonoma de Madrid (Spain)

    2002-07-01

    At present, the main source of High Level radioactive Waste (HLW) is the electrical energy production during all sep of developing. In almost all the countries with nuclear programs, the option for the final management of HLW is the Deep Geological Repository (DGR), based on the concept of multi barrier. According to this concept, the wastes is isolated from biosphere by the interposition of confinement barrier. In the context of an investigation of the near field for a repository of HLW, the FEBEX Project, a set of laboratory test has been designed to give a better understanding of the thermo-hydro-mechanical and geochemical behaviour of the compacted bentonite as a confinement barrier. The object of these work is to analyse the properties of the bentonite and its behaviour under conditions that will be found in a repository. The precipitation of mineral phases, due to local changes in the chemical equilibrium and the hydration itself, can produce changes in the salinity of the interstitial water and in the microstructural organisation of the clay particles. the hydraulic and mechanical properties of the bentonite can be modified by the special conditions of the barrier. (Author)

  5. Definition and implementation of a fully coupled THM model for unsaturated soils

    International Nuclear Information System (INIS)

    Haxaire, A.; Galavi, V.; Brinkgreve, R.B.J.

    2012-01-01

    Document available in extended abstract form only. The governing equations of a coupled thermo-hydro-mechanical (THM) model are presented. They are an extension to the previous work of Galavi (2011) in which a coupled THM model based on Biot's consolidation theory was developed for saturated and partially saturated soils. This study is based on the assumption of local thermodynamical equilibrium, meaning that all phases have the same temperature at a point of the multiphase porous medium. The model is implemented in a research version of PLAXIS 2D. The non isothermal partially saturated flow is modeled using the water mass balance described in Rutqvist et al. (2001), in which the flux is decomposed in water advection and vapor diffusion. A limiting hypothesis lies in the gas pressure assumed to be constant in the entire domain. The air flow as a separate phase is therefore neglected. This choice results in having only one independent unknown in the fluid mass balance equation, which is water pressure. However, the vapor diffusion can still be modeled. It depends on temperature by means of a decomposition in a water pressure gradient part and a temperature gradient part. The vapor density follows the psychrometric law. The water storage is described using the ratio of saturation in the soil, the mechanical volumetric strains, and the variation of the skeleton density. To model the influence of water flow in the heat transport equation, the flux term is split in an averaged conductive term and a water advection term. The other quantities such as heat capacity and density are also averaged. This yields a simple yet accurate representation of the interactions between water flow and temperature. The non-isothermal deformation is formulated in terms of Bishop stresses. The effective saturation is taken as the Bishop coefficient. This provides a better accuracy compared to experimental results. The anisotropic thermal expansion tensor is used for the drained linear

  6. BENTONITE PROCESSING

    Directory of Open Access Journals (Sweden)

    Anamarija Kutlić

    2012-07-01

    Full Text Available Bentonite has vide variety of uses. Special use of bentonite, where its absorbing properties are employed to provide water-tight sealing is for an underground repository in granites In this paper, bentonite processing and beneficiation are described.

  7. Response of Compacted Bentonites to Thermal and Thermo-Hydraulic Loadings at High Temperatures

    Directory of Open Access Journals (Sweden)

    Snehasis Tripathy

    2017-07-01

    elevated temperatures (up to 150 °C on the thermo-hydro-mechanical response of compacted bentonites in the nuclear waste repository settings.

  8. Strength and Permeability Evolution of Compressed Bentonite in Response to Salinity and Temperature Changes

    Science.gov (United States)

    Winnard, B. R.; Mitchell, T. M.; Browning, J.; Cuss, R. J.; Norris, S.; Meredith, P. G.

    2017-12-01

    Deep geological repositories are the preferred solution to dispose of radioactive waste; design concepts for these disposal facilities include compacted, saturated bentonite as a buffer between waste canister and host rock. Bentonite is favoured for its high swelling capacity, low permeability, and radionuclide retention properties. However, its thermo-hydro-mechanical tolerances must be thoroughly tested to ensure adequate long term performance. Climate variations are likely to induce periods of permafrost, and consequently, changes in groundwater salinity at depth. We performed laboratory experiments investigating effects of temperature and salinity change on uniaxial compressive strength (UCS), and permeability of compacted MX-80 bentonite cylinders. These specimens (moisture content = 22.9±0.1%, dry density = 1.66±0.02 g.cm-3) were compacted with deionised water, and a range of wt% NaCl, CaCl2, or KCl, to compare the effects of compaction fluid. Samples of compressed bentonite were cooled to -20 °C, and heated to 90 ºC, a possible temperature forecast for a repository dependent on factors such as geographical location, waste type, and facility design. Tests were all performed at room temperature, however in situ temperature tests are planned. The UCS of samples that experienced freeze thaw, and 40 ºC treatment failed at 6.5 MPa, with 4% strain, maintaining the same values as untreated bentonite compacted with deionised water. Samples compacted with saline solutions also yielded similar strengths, of 7 MPa, and failed at 4%. However, the 90 ºC, regardless of compaction fluid, failed at 15-18 MPa, at just 2% strain. In all experiments, the spread of strain accommodated varied inconsistently, however, peak stress was uniform. Further experiments into heterogeneity are needed to understand the responsible mechanisms. To obtain permeability, we utilised the pore pressure oscillation (PPO) technique with argon as the pore fluid. We also tested water as the pore

  9. Thermo-hydro-mechanics of fractured rock mass in nuclear waste studies. The measurement of electrical conductivity during the thermo-hydro-mechanical experiment

    International Nuclear Information System (INIS)

    Mursu, J.; Peltoniemi, M.

    1996-12-01

    The report reviews and summarizes the present state-of-the-art knowledge about electrical conductivity measurements of rock samples in high-temperature, high-pressure conditions. The special requirements for these measurements have been studied in terms of sample preparation, instrumentation, and experimental procedures. Possibilities to utilize a MTS System 815 testing unit, currently available at the Helsinki University of Technology, for these measurements have been studied. (17 refs.)

  10. 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

  11. Technical feasibility of a Dutch radioactive waste repository in Boom Clay : Thermo-hydro-mechanical behaviour

    NARCIS (Netherlands)

    Vardon, P.J.; Buragohain, Poly; Hicks, M.A.; Hart, J; Fokker, PA; Graham, C

    2017-01-01

    OPERA-PU-TUD321c
    Radioactive substances and ionizing radiation are used in medicine, industry, agriculture, re- search, education and electricity production. This generates radioactive waste. In the Neth- erlands, this waste is collected, treated and stored by COVRA (Centrale Organisatie Voor

  12. Study of thermo-hydro-mechanical processes at a potential site of an ...

    Indian Academy of Sciences (India)

    2008-09-29

    Sep 29, 2008 ... In this paper, field investigation has been done near to Bhima basin of peninsular India. Detailed ... investigations and other state-of-the-art methods .... Table 1. Variation of physico-mechanical parameters with depth. Tensile. Angle of. UCS strength. Cohesive internal. Young's. Sample nos. Depth. (σc). (σt).

  13. Microstructure and Thermo-Hydro-Mechanical effects as an explanation for rate dependency during seismic slip

    Science.gov (United States)

    Stefanou, I.; Rattez, H.; Sulem, J.

    2017-12-01

    Rapid shear tests of granulated fault gouges show pronounced rate-dependency. For this reason rate-dependent constitutive laws are frequently used for describing fault friction.Here we propose a micromechanical, physics-based continuum approach by considering the characteristic size of the microstructure and the thermal- and pore-pressure-diffusion mechanisms that take place in the fault gouge during rapid shearing. It is shown that even for rate-independent materials, the apparent, macroscopic behavior of the system is rate-dependent. This is due to the competition of the characteristic lengths and time scales introduced indirectly by the microstructure and the thermal and hydraulic diffusivities.Both weakening and shear band thickness are rate dependent, despite the fact that the constitutive description of the material was considered rate-independent. Moreover the size of the microstructure, which here is identified with the grain size of the fault gouge (D50), plays an important role in the slope of the softening branch of the shear stress-strain response curve and consequently in the transition from aseismic to seismic slip.References Dieterich, J. H. (1979). Modeling of rock friction: 1. Experimental results and constitutive equations. Journal of Geophysical Research, 84(B5), 2161. http://doi.org/10.1029/JB084iB05p02161 Scholz, C. H. (2002). The mechanics of earthquakes and faulting (Second). Cambridge. Sulem, J., & Stefanou, I. (2016). Thermal and chemical effects in shear and compaction bands. Geomechanics for Energy and the Environment, 6, 4-21. http://doi.org/10.1016/j.gete.2015.12.004

  14. Objective thermo-hydro-mechanical modelling of the damaged zone around a radioactive waste storage site

    International Nuclear Information System (INIS)

    Marinelli, Ferdinando

    2013-01-01

    We present two different approaches to describe the hydro-mechanical behaviour of geo-materials. In the first approach the porous media is studied through an equivalent continuum media where the interaction between the fluid and solid phases characterize the coupling behaviour at the macro-scale. We take into account this approach to model experimental tests performed over a hollow cylinder sample of clay rock (Boom Clay), considered for nuclear waste storage. The experimental results clearly show that the mechanical behaviour of the material is strongly anisotropic. For this reason we chose an elasto-plastic model based on Drucker-Prager criterion where the elastic part is characterized by cross anisotropy. The numerical results of boundary value problem clearly show localised strains around the inner hollow section. In order to regularize the numerical problem we consider a second gradient local continuum media with an enriched kinematic where an internal length can be introduced making the results mesh independent. The uniqueness study is carried out showing that changing the temporal discretization of the problem leads to different solutions. In the second approach we study the hydro-mechanical behaviour of a porous media that it is characterised by the microstructure of the material. The microstructure taken into account is composed by elastic grains, cohesive interfaces and a network of fluid channels. Using a periodic media a numerical homogenization (square finite element method) is considered to compute mass flux, stress and density of the mixture. In this way a pure numerical constitutive law is built from the microstructure of the media. This method has been implemented into a finite element code (Lagamine, Universite de Liege) to obtain results at the macro-scale. A validation of this implementation is performed for a pure mechanical boundary value problem and for a hydro-mechanical one. (author)

  15. DECOVALEX I - Bench-Mark Test 3: Thermo-hydro-mechanical modelling

    International Nuclear Information System (INIS)

    Israelsson, J.

    1995-12-01

    The bench-mark test concerns the excavation of a tunnel, located 500 m below the ground surface, and the establishment of mechanical equilibrium and steady-state fluid flow. Following this, a thermal heating due to the nuclear waste, stored in a borehole below the tunnel, was simulated. The results are reported at (1) 30 days after tunnel excavation, (2) steady state, (3) one year after thermal loading, and (4) at the time of maximum temperature. The problem specification included the excavation and waste geometry, materials properties for intact rock and joints, location of more than 6500 joints observed in the 50 by 50 m area, and calculated hydraulic conductivities. However, due to the large number of joints and the lack of dominating orientations, it was decided to treat the problem as a continuum using the computer code FLAC. The problem was modeled using a vertical symmetry plane through the tunnel and the borehole. Flow equilibrium was obtained approx. 40 days after the opening of the tunnel. Since the hydraulic conductivity was set to be stress dependent, a noticeable difference in the horizontal and vertical conductivity and flow was observed. After 40 days, an oedometer-type consolidation of the model was observed. Approx. 4 years after the initiation of the heat source, a maximum temperature of 171 C was obtained. The stress-dependent hydraulic conductivity and the temperature-dependent dynamic viscosity caused minor changes to the flow pattern. The specified mechanical boundary conditions imply that the tunnel is part of a system of parallel tunnels. However, the fixed temperature at the top boundary maintains the temperature below the temperature anticipated for an equivalent repository. The combination of mechanical and hydraulic boundary conditions cause the model to behave like an oedometer test in which the consolidation rate goes asymptotically to zero. 17 refs, 55 figs, 22 tabs

  16. Theoretical and numerical study of thermo-hydro-mechanical damage in unsaturated porous media

    International Nuclear Information System (INIS)

    Arson, Ch.

    2009-09-01

    Nuclear waste disposals are designed in multi-phase porous media. A new damage model, formulated in independent state variables (net stress, suction and thermal stress), is proposed for such geo-materials. The damage variable is a second-order tensor, which principal values grow with tensile strains. The stress/strain relations are derived from a postulated expression of the free energy. The degraded rigidities are computed by applying the Principle of Equivalent Elastic Energy for each stress state variable. Cracking effects are taken into account in transfers by introducing internal length parameters in the expressions of moisture conductivities. The damage model has been implemented in Θ-Stock Finite Element code. The mechanical model has been validated by comparing numerical results to experimental data and theoretical predictions. The qualitative evolutions given by the model in the parametric studies performed on realistic complex configurations show good trends. (author)

  17. Coupled behaviour of bentonite buffer results of PUSKURI project

    International Nuclear Information System (INIS)

    Olin, M.; Rasilainen, K.; Itaelae, A.

    2011-08-01

    In the report main results form a KYT2010 programme's project Coupled behaviour of bentonite buffer (PUSKURI) are presented. In THC modelling, Aku Itaelae made and published his Master of Science Thesis. Itaelae was able to successfully model the LOT-experiment. Additionally, he also listed problems and development proposals for THC-modelling of bentonite buffer. VTT and Numerola created in collaboration a model coupling saturation, diffusion and cation exchange; the model was implemented and tested in Numerrin, COMSOL and TOUGHREACT. Petri Jussila's PhD THM-model was implemented into COMSOL to facilitate further development. At GTK, the mineralogical characterisation of bentonite was planned. The previous THM model (Jussila's model) including only small deformations was successfully generalized to finite deformations in way at least formally preserving the original formalism. It appears that the theory allows also a possibility to include finite plastic deformations in the theory. In order to measure the relevant mechanical properties of compacted bentonite, two different experiments, namely hydrostatic compression experiment and one-dimensional compression experiment were designed. In the hydrostatic compression experiment, a cylindrical sample of compacted bentonite covered with liquid rubber coating is placed in the sample chamber equipped with a piston. The same device was also used in one-dimensional compression experiment. X-ray microtomographic techniques were used in order to study the basic mechanisms of water transport in bentonite. The preliminary results indicate that in the present experimental set-up, water transport is dominated by a dispersive mechanism such as diffusion of vapour in gas phase or diffusion of water in solid phase. (orig.)

  18. Coupled behaviour of bentonite buffer results of PUSKURI project; Bentoniittipuskurin kytketty kaeyttaeytyminen PUSKURI-hankkeen tuloksia

    Energy Technology Data Exchange (ETDEWEB)

    Olin, M.; Rasilainen, K.; Itaelae, A. [and others

    2011-08-15

    In the report main results form a KYT2010 programme's project Coupled behaviour of bentonite buffer (PUSKURI) are presented. In THC modelling, Aku Itaelae made and published his Master of Science Thesis. Itaelae was able to successfully model the LOT-experiment. Additionally, he also listed problems and development proposals for THC-modelling of bentonite buffer. VTT and Numerola created in collaboration a model coupling saturation, diffusion and cation exchange; the model was implemented and tested in Numerrin, COMSOL and TOUGHREACT. Petri Jussila's PhD THM-model was implemented into COMSOL to facilitate further development. At GTK, the mineralogical characterisation of bentonite was planned. The previous THM model (Jussila's model) including only small deformations was successfully generalized to finite deformations in way at least formally preserving the original formalism. It appears that the theory allows also a possibility to include finite plastic deformations in the theory. In order to measure the relevant mechanical properties of compacted bentonite, two different experiments, namely hydrostatic compression experiment and one-dimensional compression experiment were designed. In the hydrostatic compression experiment, a cylindrical sample of compacted bentonite covered with liquid rubber coating is placed in the sample chamber equipped with a piston. The same device was also used in one-dimensional compression experiment. X-ray microtomographic techniques were used in order to study the basic mechanisms of water transport in bentonite. The preliminary results indicate that in the present experimental set-up, water transport is dominated by a dispersive mechanism such as diffusion of vapour in gas phase or diffusion of water in solid phase. (orig.)

  19. DECOVALEX - Mathematical models of coupled T-H-M processes for nuclear waste repositories. Executive summary for Phases I,II and III

    International Nuclear Information System (INIS)

    Jing, L.; Stephansson, O.; Tsang, C.F.; Kautsky, F.

    1996-06-01

    This executive summary presents the motivation, structure, objectives, methodologies and results of the first stage of the international DECOVALEX project - DECOVALEX I (1992-1995). The acronym stands for Development of Coupled Models and their Validation against Experiment in Nuclear Waste Isolation, and the project is an international effort to develop mathematical models, numerical methods and computer codes for coupled thermo-hydro-mechanical processes in fractured rocks and buffer materials for geological isolation of spent nuclear fuel and other radioactive wastes, and validate them against laboratory and field experiments. 24 refs

  20. Bentonite erosion - Laboratory studies

    International Nuclear Information System (INIS)

    Jansson, Mats

    2010-01-01

    Document available in extended abstract form only. Bentonite clay is proposed as buffer material in the KBS-3 concept of storing spent nuclear fuel. Since the clay is plastic it will protect the canisters containing the spent fuel from movements in the rock. Furthermore, the clay will expand when taking up water, become very compact and hence limit the transport of solutes to and from the canister to only diffusion. The chemical stability of the bentonite barrier is of vital importance. If much material would be lost the barrier will lose its functions. As a side effect, lots of colloids will be released which may facilitate radionuclide transport in case of a breach in the canister. There are scenarios where during an ice age fresh melt water may penetrate down to repository depths with relatively high flow rates and not mix with older waters of high salinity. Under such conditions bentonite colloids will be more stable and there is a possibility that the bentonite buffer would start to disperse and bentonite colloids be carried away by the passing water. This work is a part of a larger project called Bentonite Erosion, initiated and supported by SKB. In this work several minor experiments have been performed in order to investigate the influence of for instance di-valent cations, gravity, etc. on the dispersion behaviour of bentonite and/or montmorillonite. A bigger experiment where the real situation was simulated using an artificial fracture was conducted. Two Plexiglas slabs were placed on top of each other, separated by plastic spacers. Bentonite was placed in a container in contact with a fracture. The bentonite was water saturated before deionized water was pumped through the fracture. The evolution of the bentonite profile in the fracture was followed visually. The eluate was collected in five different slots at the outlet side and analyzed for colloid concentration employing Photon Correlation Spectroscopy (PCS) and a Single Particle Counter (SPC). Some

  1. Thermo-hydro-mechanical processes in the nearfield around a HLW repository in argillaceous formations. Vol. I. Laboratory investigations

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-06-15

    All over the world, clay formations are being investigated as host medium for geologic disposal of radioactive waste because of their favourable properties, such as very low hydraulic conductivity against fluid transport, good sorption capacity for retardation of radionuclides, and high potential of self-sealing of fractures. The construction of a repository, the disposal of heat-emitting high-level radioactive waste (HLW), the backfilling and sealing of the remaining voids, however, will inevitably induce mechanical (M), hydraulic (H), thermal (T) and chemical (C) disturbances to the host formation and the engineered barrier system (EBS) over very long periods of time during the operation and post-closure phases of the repository. The responses and resulting property changes of the clay host rock and engineered barriers are to be well understood, characterized, and predicted for assessing the long-term performance and safety of the repository.

  2. A THM stress-strain framework for modelling the performance of argillaceous materials in deep repositories for radioactive waste

    International Nuclear Information System (INIS)

    Laloui, L.; Francois, B.

    2007-01-01

    In the scenarios for deep, geological nuclear-waste repositories, clayey soils will be hydrated, heated, cooled and dried. The numerical modelling of these mechanical processes is a key issue. Performance assessment of deep repositories for heat-generating radioactive waste would benefit from improvements in mechanical stress-strain constitutive modelling of the coupled thermo-hydro-mechanical behaviour. The presented framework allows progress in understanding the most involved phenomena relevant to nuclear-waste repositories and their coupled nature. It could be used both in the design and in the performance assessment of repositories. It may be applied to disposal in clay formations and to hard-rock repositories where artificially compacted clay is to be used as buffer and backfill. Such a constitutive framework may help in understanding some unexplained or controversial behaviours and in defining experimental programmes to answer key questions. (author)

  3. Porewater chemistry in compacted bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Muurinen, A.; Lehikoinen, J. [VTT Chemical Technology, Espoo (Finland)

    1999-03-01

    In this study, the porewater chemistry in compacted bentonite, considered as an engineered barrier in the repository of spent fuel, has been studied in interaction experiments. Many parameters, like the composition and density of bentonite, composition of the solution, bentonite-to-water ratio (B/W), surrounding conditions and experimental time have been varied in the experiments. At the end of the interaction the equilibrating solution, the porewaters squeezed out of the bentonite samples, and bentonites themselves were analyzed to give information for the interpretation and modelling of the interaction. Equilibrium modelling was performed with the HYDRAQL/CE computer code 33 refs.

  4. MOUNTAIN-SCALE COUPLED PROCESSES (TH/THC/THM)MODELS

    Energy Technology Data Exchange (ETDEWEB)

    Y.S. Wu

    2005-08-24

    This report documents the development and validation of the mountain-scale thermal-hydrologic (TH), thermal-hydrologic-chemical (THC), and thermal-hydrologic-mechanical (THM) models. These models provide technical support for screening of features, events, and processes (FEPs) related to the effects of coupled TH/THC/THM processes on mountain-scale unsaturated zone (UZ) and saturated zone (SZ) flow at Yucca Mountain, Nevada (BSC 2005 [DIRS 174842], Section 2.1.1.1). The purpose and validation criteria for these models are specified in ''Technical Work Plan for: Near-Field Environment and Transport: Coupled Processes (Mountain-Scale TH/THC/THM, Drift-Scale THC Seepage, and Drift-Scale Abstraction) Model Report Integration'' (BSC 2005 [DIRS 174842]). Model results are used to support exclusion of certain FEPs from the total system performance assessment for the license application (TSPA-LA) model on the basis of low consequence, consistent with the requirements of 10 CFR 63.342 [DIRS 173273]. Outputs from this report are not direct feeds to the TSPA-LA. All the FEPs related to the effects of coupled TH/THC/THM processes on mountain-scale UZ and SZ flow are discussed in Sections 6 and 7 of this report. The mountain-scale coupled TH/THC/THM processes models numerically simulate the impact of nuclear waste heat release on the natural hydrogeological system, including a representation of heat-driven processes occurring in the far field. The mountain-scale TH simulations provide predictions for thermally affected liquid saturation, gas- and liquid-phase fluxes, and water and rock temperature (together called the flow fields). The main focus of the TH model is to predict the changes in water flux driven by evaporation/condensation processes, and drainage between drifts. The TH model captures mountain-scale three-dimensional flow effects, including lateral diversion and mountain-scale flow patterns. The mountain-scale THC model evaluates TH effects on

  5. MOUNTAIN-SCALE COUPLED PROCESSES (TH/THC/THM) MODELS

    International Nuclear Information System (INIS)

    Y.S. Wu

    2005-01-01

    This report documents the development and validation of the mountain-scale thermal-hydrologic (TH), thermal-hydrologic-chemical (THC), and thermal-hydrologic-mechanical (THM) models. These models provide technical support for screening of features, events, and processes (FEPs) related to the effects of coupled TH/THC/THM processes on mountain-scale unsaturated zone (UZ) and saturated zone (SZ) flow at Yucca Mountain, Nevada (BSC 2005 [DIRS 174842], Section 2.1.1.1). The purpose and validation criteria for these models are specified in ''Technical Work Plan for: Near-Field Environment and Transport: Coupled Processes (Mountain-Scale TH/THC/THM, Drift-Scale THC Seepage, and Drift-Scale Abstraction) Model Report Integration'' (BSC 2005 [DIRS 174842]). Model results are used to support exclusion of certain FEPs from the total system performance assessment for the license application (TSPA-LA) model on the basis of low consequence, consistent with the requirements of 10 CFR 63.342 [DIRS 173273]. Outputs from this report are not direct feeds to the TSPA-LA. All the FEPs related to the effects of coupled TH/THC/THM processes on mountain-scale UZ and SZ flow are discussed in Sections 6 and 7 of this report. The mountain-scale coupled TH/THC/THM processes models numerically simulate the impact of nuclear waste heat release on the natural hydrogeological system, including a representation of heat-driven processes occurring in the far field. The mountain-scale TH simulations provide predictions for thermally affected liquid saturation, gas- and liquid-phase fluxes, and water and rock temperature (together called the flow fields). The main focus of the TH model is to predict the changes in water flux driven by evaporation/condensation processes, and drainage between drifts. The TH model captures mountain-scale three-dimensional flow effects, including lateral diversion and mountain-scale flow patterns. The mountain-scale THC model evaluates TH effects on water and gas

  6. THM modelling of buffer, backfill and other system components. Critical processes and scenarios

    International Nuclear Information System (INIS)

    Aakesson, Mattias; Kristensson, Ola; Boergesson, Lennart; Dueck, Ann; Hernelind, Jan

    2010-03-01

    A number of critical thermo-hydro-mechanical processes and scenarios for the buffer, tunnel backfill and other filling components in the repository have been identified. These processes and scenarios representing different aspects of the repository evolution have been pinpointed and modelled. In total, 22 cases have been modelled. Most cases have been analysed with finite element (FE) calculations, using primarily the two codes Abaqus and Code B right. For some cases analytical methods have been used either to supplement the FE calculations or due to that the scenario has a character that makes it unsuitable or very difficult to use the FE method. Material models and element models and choice of parameters as well as presumptions have been stated for all modelling cases. In addition, the results have been analysed and conclusions drawn for each case. The uncertainties have also been analysed. Besides the information given for all cases studied, the codes and material models have been described in a separate so called data report

  7. THM modelling of buffer, backfill and other system components. Critical processes and scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Aakesson, Mattias; Kristensson, Ola; Boergesson, Lennart; Dueck, Ann (Clay Technology AB, Lund (Sweden)); Hernelind, Jan (5T-Engineering AB, Vaesteraas (Sweden))

    2010-03-15

    A number of critical thermo-hydro-mechanical processes and scenarios for the buffer, tunnel backfill and other filling components in the repository have been identified. These processes and scenarios representing different aspects of the repository evolution have been pinpointed and modelled. In total, 22 cases have been modelled. Most cases have been analysed with finite element (FE) calculations, using primarily the two codes Abaqus and Code-Bright. For some cases analytical methods have been used either to supplement the FE calculations or due to that the scenario has a character that makes it unsuitable or very difficult to use the FE method. Material models and element models and choice of parameters as well as presumptions have been stated for all modelling cases. In addition, the results have been analysed and conclusions drawn for each case. The uncertainties have also been analysed. Besides the information given for all cases studied, the codes and material models have been described in a separate so called data report

  8. Modelling the evolution of compacted bentonite clays in engineered barrier systems: process model development of the bentonite-water-air system

    International Nuclear Information System (INIS)

    Bond, A.E.; Wilson, J.C.; Maul, P.R.; Robinson, P.C.; Savage, D.

    2010-01-01

    Document available in extended abstract form only. An adequate understanding of the short- and long-term evolution of compacted bentonite clays in engineered barrier systems (EBS) for radioactive waste based on the KBS-3 disposal concept is an essential requirement for demonstrating the safe performance of the system. Uncertainties in the way that the re-saturation process occurs are intrinsically tied to the thermal and mechanical evolution of the bentonite buffer and its interaction with the disposal canister and host-rock. Furthermore, the evolution of bentonite in the presence of changing ambient saturation states, groundwater chemistry and stress states could cause the bentonite re-saturation and long-term stability (including the so-called 'buffer erosion scenario') to deviate from the behaviour required by the safety case; this has emphasised the need to consider adequately coupled thermal (T), hydraulic(H), mechanical (M) and chemical (C) processes. Historically, there have been fundamental differences in the representation of porosity and water disposition between geochemical modelling and coupled THM modelling studies. In this paper, a model for the porosity and water disposition in bentonite is presented that is more detailed than models used to date in most THM modelling studies under variably saturated conditions. The new model moves away from the conventional THM soils approach which treats bentonite as an elasto-plastic porous medium with water or air occupying a notional porosity with the inclusion of additional process models to take into account the very high observed water suctions, intrinsic permeability variation and macroscopic swelling of partially saturated compacted bentonite. It replaces the empirical parameterisation usually employed in THM models with a direct representation of the water disposition, pore structure and relevant processes, albeit at an abstracted level. The new model differentiates between water which can be

  9. Gas Transport in Bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Villar, M. V.; Gutierre-Rodrigo, V.; Martin, P. I.; Romero, F. J.; Barcala, J. M.

    2013-07-01

    The gas permeability of the Spanish FEBEX bentonite compacted at dry densities of between 1.4 and 1.8 g/cm{sup 3} with high water contents was measured for different confining, injection and back pressures. The results were compared with results obtained in previous investigations for lower degrees of saturation. It was checked that gas permeability was greatly affected by dry density, decreasing about three orders of magnitude when it increased from 1.5 to 1.8 g/cm{sup 3} for similar water content. The increase of water content caused also a decrease in gas permeability. It was found that both gas permeability and the relative gas permeability were mainly related to the accessible porosity. These relationships could be fitted to potential expressions with exponents between 3 and 4, as well as the relationship between intrinsic permeability and void ratio. For gas pressures below 1.2 MPa no effect of the injection or confining pressures on the value of permeability was detected. For a given confining pressure the permeability value decreased as the effective pressure increased, especially if the increase in effective pressure was due to a decrease in gas back pressure. It was checked that the Klinkenberg effect was not significant for this material in the range of pressures applied in the tests. The gas breakthrough pressure values in FEBEX saturated bentonite were determined for different dry densities. They increased clearly with dry density and were always higher than the swelling pressure of the bentonite. In high density samples gas flow tended to stop abruptly after breakthrough, whereas in lower density samples gas flow decreased gradually until a given pressure gradient was reached. The permeabilities computed after breakthrough (which usually did not stabilise) were inversely related to dry density. This would indicate that, even if the flow took place predominantly through preferential pathways that sometimes closed quickly after breakthrough and others

  10. Gas Transport in Bentonite

    International Nuclear Information System (INIS)

    Villar, M. V.; Gutierrez-Rodrigo, V.; Martin, P. L.; Romero, F. J.; Barcala, J. M.

    2013-01-01

    The gas permeability of the Spanish FEBEX bentonite compacted at dry densities of between 1.4 and 1.8 g/cm 3 with high water contents was measured for different confining, injection and back pressures. The results were compared with results obtained in previous investigations for lower degrees of saturation. It was checked that gas permeability was greatly affected by dry density, decreasing about three orders of magnitude when it increased from 1.5 to 1.8 g/cm 3 for similar water content. The increase of water content caused also a decrease in gas permeability. It was found that both gas permeability and the relative gas permeability were mainly related to the accessible porosity. These relationships could be fitted to potential expressions with exponents between 3 and 4, as well as the relationship between intrinsic permeability and void ratio. For gas pressures below 1.2 MPa no effect of the injection or confining pressures on the value of permeability was detected. For a given confining pressure the permeability value decreased as the effective pressure increased, especially if the increase in effective pressure was due to a decrease in gas back pressure. It was checked that the Klinkenberg effect was not significant for this material in the range of pressures applied in the tests. The gas breakthrough pressure values in FEBEX saturated bentonite were determined for different dry densities. They increased clearly with dry density and were always higher than the swelling pressure of the bentonite. In high density samples gas flow tended to stop abruptly after breakthrough, whereas in lower density samples gas flow decreased gradually until a given pressure gradient was reached. The permeabilities computed after breakthrough (which usually did not stabilise) were inversely related to dry density. This would indicate that, even if the flow took place predominantly through preferential pathways that sometimes closed quickly after breakthrough and others remained

  11. Spectral response of THM grown CdZnTe crystals

    DEFF Research Database (Denmark)

    Chen, H.; Awadalla, S.A.; Harris, F.

    2008-01-01

    The spectral response of several crystals grown by the Traveling Heater Method (THM) were investigated. An energy resolution of 0.98% for a Pseudo Frisch-Grid of 4 × 4 × 9 mm3 and 2.1% FWHM for a coplanar-grid of size 11 × 11 × 5 mm3 were measured using 137Cs-662 keV. In addition a 4% FWHM at 122...

  12. Development and validation of mechanical model for saturated/unsaturated bentonite buffer

    International Nuclear Information System (INIS)

    Yamamoto, S.; Komine, H.; Kato, S.

    2010-01-01

    Document available in extended abstract form only. Development and validation of mechanical models for bentonite buffer and backfill materials are one of important subjects to appropriately evaluate long term behaviour or condition of the EBS in radioactive waste disposal. The Barcelona Basic Model (BBM), which is one of extensions of the modified Cam-Clay model for unsaturated and expansive soil, has been developed and widely applied to several problems by using the coupled THM code, Code B right. Advantage of the model is that mechanical characteristics of buffer and backfill materials under not only saturated condition but also unsaturated one are taken account as well as swelling characteristics due to wetting. In this study the BBM is compared with already existing experimental data and already developed another model in terms of swelling characteristics of Japanese bentonite Kunigel-V1, and is validated in terms of consolidation characteristics based on newly performed controlled-suction oedometer tests for the Kunigel-V1 bentonite. Komine et al. (2003) have proposed a model (set of equations) for predicting swelling characteristics based on the diffuse double layer concept and the van der Waals force concept etc. They performed a lot of swelling deformation tests of bentonite and sand-bentonite mixture to confirm the applicability of the model. The BBM well agrees with the model proposed by Komine et al. and the experimental data in terms of swelling characteristics. Compression index and swelling index depending on suction are introduced in the BBM. Controlled-suction consolidation tests (oedometer tests) were performed to confirm the applicability of the suction dependent indexes to unsaturated bentonite. Compacted bentonite with initial dry density of 1.0 Mg/m 3 was tested. Constant suction, 80 kPa, 280 kPa and 480 kPa was applied and kept during the consolidation tests. Applicability of the BBM to consolidation and swelling behaviour of saturated and

  13. Thermo-mechanical cementation effects in bentonite investigated by unconfined compression tests

    International Nuclear Information System (INIS)

    Dueck, Ann; Boergesson, Lennart; Karnland, Ola

    2010-01-01

    Document available in extended abstract form only. Mechanical properties of buffer material are included in the model used for predicting the physical behaviour of saturated buffer in the final disposal of spent nuclear fuel. One simple test where the mechanical properties can be quantified is the unconfined compression test. In this type of test the relation between stress and strain are determined from axial compression of a cylindrical specimen. In the project LOT the unconfined compression test was used to study the mechanical properties on field exposed buffer material. The results from these test series showed that specimens exposed to warm conditions had a significantly reduced strain at failure compared to reference material. Changes in mechanical properties may be due to incipient chemical changes in the material. However, the present study focuses on other possible sources for brittle failure behaviour. In this study the objective was to experimentally investigate if deviating stress-strain behaviour measured after temperature exposure could be explained by Thermo-Hydro-Mechanical processes. The word cementation is used as a general term for the process involving a change in mechanical properties including brittleness at failure. A relatively large number of specimens were tested representing sodium dominated and calcium dominated bentonites. Cylindrical specimens were compacted from air dry powder to a height and diameter of 20 mm. The main part of the specimens was put in a saturation device prior to the tests in order to ensure full saturation. After the saturation each sample was placed in a mechanical press where a constant rate of strain was applied axially to the specimens having no radial confinement. During the test the deformation and the applied force were measured by means of force and strain transducers. After failure the water content and density were determined. Test series were carried out for investigating the influence of for example

  14. Bentonite erosion. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Birgersson, Martin; Boergesson, Lennart; Hedstroem, Magnus; Karnland, Ola; Nilsson, Ulf (Clay Technology AB, Lund (Sweden))

    2009-12-15

    Low saline water may reach KBS-3 repository depth, e.g. during periods of glaciation. Under such aqueous conditions, the montmorillonite part of the bentonite buffer might transform into a sol and thereby be transported away with flowing water in fractures. The primary aim with this report is to improve the understanding of the basic principles for this possible montmorillonite particle release. The report includes experimental and theoretical work performed at Clay Technology. Natural bentonite and ion-exchanged purified montmorillonite from three different geographical origins, Wyoming (U.S.), Milos (Greece) and Kutch (India) have been studied. Experimental and/or theoretical investigations have been performed with respect to: - Free swelling ability; - Rheological properties; - Rate of bentonite loss into fractures; - Filtering; - Ion exchange; - Sol formation ability; - Ion diffusion; - Mass loss due to erosion. The performed erosion experiments show that erosion does not occur in a mixed calcium/sodium montmorillonite with at least 20% calcium in exchange positions, when the external solution contains above 4 mM charge equivalents. This result is in agreement with the presented conceptual view of sol formation and measured equilibrium properties in mixed calcium/sodium montmorillonite. The findings imply that the buffer will be stable for non-glacial conditions. However, erosion due to sol formation cannot be ruled out for glacial conditions.

  15. Bentonite erosion. Final report

    International Nuclear Information System (INIS)

    Birgersson, Martin; Boergesson, Lennart; Hedstroem, Magnus; Karnland, Ola; Nilsson, Ulf

    2009-12-01

    Low saline water may reach KBS-3 repository depth, e.g. during periods of glaciation. Under such aqueous conditions, the montmorillonite part of the bentonite buffer might transform into a sol and thereby be transported away with flowing water in fractures. The primary aim with this report is to improve the understanding of the basic principles for this possible montmorillonite particle release. The report includes experimental and theoretical work performed at Clay Technology. Natural bentonite and ion-exchanged purified montmorillonite from three different geographical origins, Wyoming (U.S.), Milos (Greece) and Kutch (India) have been studied. Experimental and/or theoretical investigations have been performed with respect to: - Free swelling ability; - Rheological properties; - Rate of bentonite loss into fractures; - Filtering; - Ion exchange; - Sol formation ability; - Ion diffusion; - Mass loss due to erosion. The performed erosion experiments show that erosion does not occur in a mixed calcium/sodium montmorillonite with at least 20% calcium in exchange positions, when the external solution contains above 4 mM charge equivalents. This result is in agreement with the presented conceptual view of sol formation and measured equilibrium properties in mixed calcium/sodium montmorillonite. The findings imply that the buffer will be stable for non-glacial conditions. However, erosion due to sol formation cannot be ruled out for glacial conditions.

  16. Mountain-Scale Coupled Processes (TH/THC/THM)

    International Nuclear Information System (INIS)

    Dixon, P.

    2004-01-01

    The purpose of this Model Report is to document the development of the Mountain-Scale Thermal-Hydrological (TH), Thermal-Hydrological-Chemical (THC), and Thermal-Hydrological-Mechanical (THM) Models and evaluate the effects of coupled TH/THC/THM processes on mountain-scale UZ flow at Yucca Mountain, Nevada. This Model Report was planned in ''Technical Work Plan (TWP) for: Performance Assessment Unsaturated Zone'' (BSC 2002 [160819], Section 1.12.7), and was developed in accordance with AP-SIII.10Q, Models. In this Model Report, any reference to ''repository'' means the nuclear waste repository at Yucca Mountain, and any reference to ''drifts'' means the emplacement drifts at the repository horizon. This Model Report provides the necessary framework to test conceptual hypotheses for analyzing mountain-scale hydrological/chemical/mechanical changes and predict flow behavior in response to heat release by radioactive decay from the nuclear waste repository at the Yucca Mountain site. The mountain-scale coupled TH/THC/THM processes models numerically simulate the impact of nuclear waste heat release on the natural hydrogeological system, including a representation of heat-driven processes occurring in the far field. The TH simulations provide predictions for thermally affected liquid saturation, gas- and liquid-phase fluxes, and water and rock temperature (together called the flow fields). The main focus of the TH Model is to predict the changes in water flux driven by evaporation/condensation processes, and drainage between drifts. The TH Model captures mountain-scale three dimensional (3-D) flow effects, including lateral diversion at the PTn/TSw interface and mountain-scale flow patterns. The Mountain-Scale THC Model evaluates TH effects on water and gas chemistry, mineral dissolution/precipitation, and the resulting impact to UZ hydrological properties, flow and transport. The THM Model addresses changes in permeability due to mechanical and thermal disturbances in

  17. Bentonite erosion. Laboratory studies

    Energy Technology Data Exchange (ETDEWEB)

    Jansson, Mats (Div. of Nuclear Chemistry, Royal Inst. of Technology, Stockholm (Sweden), School of Chemical Science and Engineering)

    2009-11-15

    This report covers the laboratory studies that have been performed at Nuclear Chemistry, KTH in the project 'Bentonite Erosion'. Many of the experiments in this report were performed to support the work of the modelling group and were often relatively simple. One of the experiment series was performed to see the impact of gravity and concentration of mono- and di-valent cations. A clay suspension was prepared in a test tube. A net was placed in contact with the suspension, the test tube was filled with solutions of different concentrations and the system was left overnight to settle. The tube was then turned upside down and the behaviour was visually observed. Either the clay suspension fell through the net or stayed on top. By using this method surprisingly sharp determinations of the Critical Coagulation (Flocculation) Concentration (CCC/CFC) could be made. The CCC/CFC of Ca2+ was for sodium montmorillonite determined to be between 1 and 2 mM. An artificial fracture was manufactured in order to simulate the real case scenario. The set-up was two Plexiglas slabs separated by 1 mm thick spacers with a bentonite container at one side of the fracture. Water was pumped with a very low flow rate perpendicular to bentonite container and the water exiting the fracture was sampled and analyzed for colloid content. The bentonite used was treated in different ways. In the first experiment a relatively montmorillonite rich clay was used while in the second bentonite where only the readily soluble minerals had been removed was used. Since Plexiglas was used it was possible to visually observe the bentonite dispersing into the fracture. After the compacted bentonite (1,000 kg/m3) had been water saturated the clay had expanded some 12 mm out into the fracture. As the experiment progressed the clay expanded more out into the fracture and seemed to fractionate in two different phases with less material in the outmost phase. A dark rim which was later analyzed to contain

  18. Modelling of the physical behaviour of water saturated clay barriers. Laboratory tests, material models and finite element application

    International Nuclear Information System (INIS)

    Boergesson, L.; Johannesson, L.E.; Sanden, T.; Hernelind, J.

    1995-09-01

    This report deals with laboratory testing and modelling of the thermo-hydro-mechanical (THM) properties of water saturated bentonite based buffer materials. A number of different laboratory tests have been performed and the results are accounted for. These test results have lead to a tentative material model, consisting of several sub-models, which is described in the report. The tentative model has partly been adapted to the material models available in the finite element code ABAQUS and partly been implemented and incorporated in the code. The model that can be used for ABAQUS calculations agrees with the tentative model with a few exceptions. The model has been used in a number of verification calculations, simulating different laboratory tests, and the results have been compared with actual measurements. These calculations show that the model generally can be used for THM calculations of the behaviour of water saturated buffer materials, but also that there is still a lack of some understanding. It is concluded that the available model is relevant for the required predictions of the THM behaviour but that a further improvement of the model is desirable

  19. Current Status of Research Activities Related to THM-Coupled Processes in Buffer

    International Nuclear Information System (INIS)

    Choi, Heui Joo; Lee, Changsoo; Choi, Young Chul; Lee, Minsoo; Kim, Jin Seop

    2015-01-01

    For the purpose of enhancing the understanding of THM-coupled behavior in and around buffer, a computer code, KAERI-SIMULATOR, is being developed and verified by participating in Decovalex-2015 project. The THM data collected from this facility will be used to validate the KAERI-SIMULATOR

  20. Current Status of Research Activities Related to THM-Coupled Processes in Buffer

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Heui Joo; Lee, Changsoo; Choi, Young Chul; Lee, Minsoo; Kim, Jin Seop [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-05-15

    For the purpose of enhancing the understanding of THM-coupled behavior in and around buffer, a computer code, KAERI-SIMULATOR, is being developed and verified by participating in Decovalex-2015 project. The THM data collected from this facility will be used to validate the KAERI-SIMULATOR.

  1. A coupled THMC model of a heating and hydration laboratory experiment in unsaturated compacted FEBEX bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, L.; Samper, J.; Montenegro, L.; Fernandez, A.M.

    2010-05-01

    Unsaturated compacted bentonite is foreseen by several countries as a backfill and sealing material in high-level radioactive waste repositories. The strong interplays between thermal (T), hydrodynamic (H), mechanical (M) and chemical (C) processes during the hydration stage of a repository call for fully coupled THMC models. Validation of such THMC models is prevented by the lack of comprehensive THMC experiments and the difficulties of experimental methods to measure accurately the chemical composition of bentonite porewater. We present here a non-isothermal multiphase flow and multicomponent reactive solute transport model for a deformable medium of a heating and hydration experiment performed on a sample of compacted FEBEX bentonite. Besides standard solute transport and geochemical processes, the model accounts for solute cross diffusion and thermal and chemical osmosis. Bentonite swelling is solved with a state-surface approach. The THM model is calibrated with transient temperature, water content and porosity data measured at the end of the experiment. The reactive transport model is calibrated with porewater chemical data derived from aqueous extract data. Model results confirm that thermal osmosis is relevant for the hydration of FEBEX bentonite while chemical osmosis can be safely neglected. Dilution and evaporation are the main processes controlling the concentration of conservative species. Dissolved cations are mostly affected by calcite dissolution-precipitation and cation exchange reactions. Dissolved sulphate is controlled by gypsum/anhydrite dissolution-precipitation. pH is mostly buffered by protonation/deprotonation via surface complexation. Computed concentrations agree well with inferred aqueous extract data at all sections except near the hydration boundary where cation data are affected by a sampling artifact. The fit of Cl{sup -} data is excellent except for the data near the heater. The largest deviations of the model from inferred aqueous

  2. Thermally-driven Coupled THM Processes in Shales

    Science.gov (United States)

    Rutqvist, J.

    2017-12-01

    Temperature changes can trigger strongly coupled thermal-hydrological-mechanical (THM) processes in shales that are important to a number of subsurface energy applications, including geologic nuclear waste disposal and hydrocarbon extraction. These coupled processes include (1) direct pore-volume couplings, by thermal expansion of trapped pore-fluid that triggers instantaneous two-way couplings between pore fluid pressure and mechanical deformation, and (2) indirect couplings in terms of property changes, such as changes in mechanical stiffness, strength, and permeability. Direct pore-volume couplings have been studied in situ during borehole heating experiments in shale (or clay stone) formations at Mont Terri and Bure underground research laboratories in Switzerland and France. Typically, the temperature changes are accompanied with a rapid increase in pore pressure followed by a slower decrease towards initial (pre-heating) pore pressure. Coupled THM modeling of these heater tests shows that the pore pressure increases because the thermal expansion coefficient of the fluid is much higher than that of the porous clay stone. Such thermal pressurization induces fluid flow away from the pressurized area towards areas of lower pressure. The rate of pressure increase and magnitude of peak pressure depends on the rate of heating, pore-compressibility, and permeability of the shale. Modeling as well as laboratory experiments have shown that if the pore pressure increase is sufficiently large it could lead to fracturing of the shale or shear slip along pre-existing bedding planes. Another set of data and observations have been collected associated with studies related to concentrated heating and cooling of oil-shales and shale-gas formations. Heating may be used to enhance production from tight oil-shale, whereas thermal stimulation has been attempted for enhanced shale-gas extraction. Laboratory experiments on shale have shown that strength and elastic deformation

  3. SR-Site Data report. THM modelling of buffer, backfill and other system components

    Energy Technology Data Exchange (ETDEWEB)

    Aakesson, Mattias; Boergesson, Lennart; Kristensson, Ola (Clay Technology AB, Lund (Sweden))

    2010-03-15

    This report is a supplement to the SR-Site data report. Based on the issues raised in the Process reports concerning THM processes in buffer, backfill and other system components, 22 modelling tasks have been identified, representing different aspects of the repository evolution. The purpose of this data report is to provide parameter values for the materials included in these tasks. Two codes, Code{_}Bright and Abaqus, have been employed for the tasks. The data qualification has focused on the bentonite material for buffer, backfill and the seals for tunnel plugs and bore-holes. All these system components have been treated as if they were based on MX-80 bentonite. The sources of information and documentation of the data qualification for the parameters for MX-80 have been listed. A substantial part of the refinement, especially concerning parameters used for Code{_}Bright, is presented in the report. The data qualification has been performed through a motivated and transparent chain; from measurements, via evaluations, to parameter determinations. The measured data was selected to be as recent, traceable and independent as possible. The data sets from this process are thus regarded to be qualified. The conditions for which the data is supplied, the conceptual uncertainties, the spatial and temporal variability and correlations are briefly presented and discussed. A more detailed discussion concerning the data uncertainty due to precision, bias and representativity is presented for measurements of swelling pressure, hydraulic conductivity, shear strength, retention properties and thermal conductivity. The results from the data qualification are presented as a detailed evaluation of measured data. In order to strengthen the relevance of the parameter values and to confirm previously used relations, either newer or independent measurements have been taken into account in the parameter value evaluation. Previously used relations for swelling pressure, hydraulic

  4. SR-Site Data report. THM modelling of buffer, backfill and other system components

    International Nuclear Information System (INIS)

    Aakesson, Mattias; Boergesson, Lennart; Kristensson, Ola

    2010-03-01

    This report is a supplement to the SR-Site data report. Based on the issues raised in the Process reports concerning THM processes in buffer, backfill and other system components, 22 modelling tasks have been identified, representing different aspects of the repository evolution. The purpose of this data report is to provide parameter values for the materials included in these tasks. Two codes, Code B right and Abaqus, have been employed for the tasks. The data qualification has focused on the bentonite material for buffer, backfill and the seals for tunnel plugs and bore-holes. All these system components have been treated as if they were based on MX-80 bentonite. The sources of information and documentation of the data qualification for the parameters for MX-80 have been listed. A substantial part of the refinement, especially concerning parameters used for Code B right, is presented in the report. The data qualification has been performed through a motivated and transparent chain; from measurements, via evaluations, to parameter determinations. The measured data was selected to be as recent, traceable and independent as possible. The data sets from this process are thus regarded to be qualified. The conditions for which the data is supplied, the conceptual uncertainties, the spatial and temporal variability and correlations are briefly presented and discussed. A more detailed discussion concerning the data uncertainty due to precision, bias and representativity is presented for measurements of swelling pressure, hydraulic conductivity, shear strength, retention properties and thermal conductivity. The results from the data qualification are presented as a detailed evaluation of measured data. In order to strengthen the relevance of the parameter values and to confirm previously used relations, either newer or independent measurements have been taken into account in the parameter value evaluation. Previously used relations for swelling pressure, hydraulic

  5. Simulation of ultra-long term behavior in HLW near-field by centrifugal model test. Part 1. Development of centrifugal equipment and centrifuge model test method

    International Nuclear Information System (INIS)

    Nishimoto, Soshi; Okada, Tetsuji; Sawada, Masataka

    2011-01-01

    The objective of this paper is to develop a centrifugal equipment which can continuously be run for a long time and a model test method in order to evaluate a long term behavior which is a coupled thermo-hydro-mechanical processes in the high level wastes geological disposal repository and the neighborhood (called 'near-field'). The centrifugal equipment of CRIEPI, 'CENTURY5000-THM', developed in the present study is able to run continuously up to six months. Therefore, a long term behavior in the near-field can be simulated in a short term, for instance, the behavior for 5000 equivalent years can be simulated in six months by centrifugalizing 100 G using a 1/100 size model. We carried out a test using a nylon specimen in a centrifugal force field of 30 G and confirmed the operations of CENTURY5000-THM, control and measurement for 11 days. As the results, it was able to control the stress in the pressure vessel and measure the values of strain, temperature and pressure. And, as a result of scanning the small model of near-field including the metal overpack, bentonite buffer and rock by a medical X-rays CT scanner, the internal structure of the model was able to be evaluated when the metal artifact was reduced. From these results, the evaluation for a long term behavior of a disposal repository by the method of centrifugal model test became possible. (author)

  6. A numerical model for modeling microstructure and THM couplings in fault gouges

    Science.gov (United States)

    Veveakis, M.; Rattez, H.; Stefanou, I.; Sulem, J.; Poulet, T.

    2017-12-01

    When materials are subjected to large deformations, most of them experience inelastic deformations, accompanied by a localization of these deformations into a narrow zone leading to failure. Localization is seen as an instability from the homogeneous state of deformation. Therefore a first approach to study it consists at looking at the possible critical conditions for which the constitutive equations of the material allow a bifurcation point (Rudnicki & Rice 1975). But in some cases, we would like to know the evolution of the material after the onset of localization. For example, a fault in the crustal part of the lithosphere is a shear band and the study of this localized zone enables to extract information about seismic slip. For that, we need to approximate the solution of a nonlinear boundary value problem numerically. It is a challenging task due to the complications that arise while dealing with a softening behavior. Indeed, the classical continuum theory cannot be used because the governing system of equations is ill-posed (Vardoulakis 1985). This ill-posedness can be tracked back to the fact that constitutive models don't contain material parameters with the dimension of a length. It leads to what is called "mesh dependency" for numerical simulations, as the deformations localize in only one element of the mesh and the behavior of the system depends thus on the mesh size. A way to regularize the problem is to resort to continuum models with microstructure, such as Cosserat continua (Sulem et al. 2011). Cosserat theory is particularly interesting as it can explicitly take into account the size of the microstructure in a fault gouge. Basically, it introduces 3 degrees of freedom of rotation on top of the 3 translations (Godio et al. 2016). The original work of (Mühlhaus & Vardoulakis 1987) is extended in 3D and thermo-hydro mechanical couplings are added to the model to study fault system in the crustal part of the lithosphere. The system of equations is

  7. Prediction for swelling characteristics of compacted bentonite

    International Nuclear Information System (INIS)

    Komine, H.; Ogata, N.

    1996-01-01

    Compacted bentonites are attracting greater attention as back-filling (buffer) materials for high-level nuclear waste repositories. For this purpose, it is very important to quantitatively evaluate the swelling characteristics of compacted bentonite. New equations for evaluating the relationship between the swelling deformation of compacted bentonite and the distance between two montmorillonite layers are derived. New equations for evaluating the ion concentration of pore water and the specific surface of bentonite, which significantly influence the swelling characteristics of compacted bentonite, are proposed. Furthermore, a prediction method for the swelling characteristics of compacted bentonite is presented by combining the new equations with the well-known theoretical equations of repulsive and attractive forces between two montmorillonite layers. The applicability of this method was investigated by comparing the predicted results with laboratory test results on the swelling deformation and swelling pressure of compacted bentonites. (author) 31 refs., 8 tabs., 12 figs

  8. FEBEX. Investigations on gas generation, release and migration

    International Nuclear Information System (INIS)

    Jockwer, Norbert; Wieczorek, Klaus

    2008-06-01

    The FEBEX project is based on the Spanish reference concept for the disposal of radioactive waste in crystalline rock, which considers the emplacement of the canisters enclosing the conditioned waste surrounded by clay barriers constructed of high-compacted bentonite blocks in horizontal drifts /ENR 957. The whole project consisted of an experimental and a modelling part. The experimental part itself was divided into the in-situ test, a mock-up test performed at the CIEMAT laboratory, and various small-scale laboratory tests. In the modelling part it was expected to develop and validate the thermo-hydro-mechanical (THM) and the thermo-hydro-chemical (THC) processes for the performance assessment of the near-field behaviour. GRS was only involved in the in-situ test and some additional laboratory work with regard to gas generation, gas migration, and pore pressure build-up in the buffer constructed of high-compacted bentonite blocks around the electrical heaters simulating the waste containers. The following topics are covered: installation and dismantling of the heater pipes; methods of gas generation and release measurement, summary of results and discussion

  9. Organophilic bentonites based on Argentinean and Brazilian bentonites: part 2: potential evaluation to obtain nanocomposites

    Directory of Open Access Journals (Sweden)

    L. B. Paiva

    2012-12-01

    Full Text Available This work describes the preparation of composites of polypropylene and organophilic bentonites based on Brazilian and Argentinean bentonites. During the processing of the samples in a twin screw microextruder, torque and pressures of the extruder were accompanied and the viscosity values were calculated. No significant changes in the torque, pressure and viscosity were found for composites prepared with different bentonites. The samples were characterized by XRD and TEM to evaluate the structure and dispersion of the organophilic bentonites. Composites with exfoliated, partially exfoliated and intercalated structures were obtained and correlations between the intrinsic properties of the sodium clays and organophilic bentonites and their influence on the composites were studied. The cation exchange capacity of the sodium bentonites and the swelling capacity of the organophilic bentonites were the most important properties to obtain exfoliated structures in composites. All bentonites showed the potential to obtain polymer nanocomposites, but the ones from Argentina displayed the best results.

  10. Bentonite in the repository - Manufacture of bentonite blocks. A literature study

    International Nuclear Information System (INIS)

    Hultgren, Aa.

    1995-09-01

    Activities in nuclear power countries are reviewed, concerning developments in the use of bentonite for backfilling in nuclear waste repositories, in particular regarding manufacture of bentonite-blocks. Only one report was found which in detail describes the manufacture of highly compacted blocks of bentonite. Use of bentonite for sealing boreholes etc in the oil- and gas industry was also covered in the literature study. 19 refs, 3 tabs

  11. DECOVALEX-THMC Project. Task A. Influence of near field coupled THM phenomena on the performance of a spent fuel repository. Report of Task A1: Preliminary scoping calculations

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Son (ed.) [Canadian Nuclear Safety Commission (Canada); Lanru Jing (ed.) [Royal Institute of Technology, Stockholm (Sweden); Boergesson, Lennart [Clay Technology AB, Lund (Sweden); Chijimatzu, Masakazu [Hazama Corporation (Japan); Jussila, Petri [Helsinki Univ. of Technology, Helsinki (Finland); Rutqvist, Jonny [Lawrence Berkeley National Laboratory CA (United States)

    2007-02-15

    The DECOVALEX-THMC project is an ongoing international co-operative project that was stared in 2004 to support the development of mathematical models of coupled Thermal (T), Hydrological (H), Mechanical (M) and Chemical (C) processes in geological media for siting potential nuclear fuel waste repositories. The general objective is to characterise and evaluate the coupled THMC processes in the near field and far field of a geological repository and to assess their impact on performance assessment: - during the three phases of repository development: excavation phase, operation phase and post-closure phase; - for three different rocks types: crystalline, argillaceous and tuff; - with specific focus on the issues of: Excavation Damaged Zone (EDZ), permanent property changes of rock masses, and glaciation and permafrost phenomena. The project involves a large number of research teams supported by radioactive waste management agencies or governmental regulatory bodies in Canada, China, Finland, France, Germany, Japan, Sweden and USA, who conducted advanced studies and numerical modelling of coupled THMC processes under five tasks. This report presents the definition of the first phase, Task A-1, of the Task A of the project. The task is a working example of how interaction between THMC modelling and SA analysis could be performed. Starting with the technical definition of the Task A, the report presents the results of preliminary THM calculations with a purpose of an initial appreciation of the phenomena and material properties that must be better understood in subsequent phases. Many simplifications and assumptions were introduced and the results should be considered under these assumptions. Based on the evaluation of the multiple teams' results, a few points of concern were identified that may guide the successive phases of Task A studies: 1. The predicted maximum total stress in the MX-80 bentonite could slightly exceed the 15 MPa design pressure for the

  12. DECOVALEX-THMC Project. Task A. Influence of near field coupled THM phenomena on the performance of a spent fuel repository. Report of Task A1: Preliminary scoping calculations

    International Nuclear Information System (INIS)

    Nguyen, Son; Lanru Jing; Boergesson, Lennart; Chijimatzu, Masakazu; Jussila, Petri; Rutqvist, Jonny

    2007-02-01

    The DECOVALEX-THMC project is an ongoing international co-operative project that was stared in 2004 to support the development of mathematical models of coupled Thermal (T), Hydrological (H), Mechanical (M) and Chemical (C) processes in geological media for siting potential nuclear fuel waste repositories. The general objective is to characterise and evaluate the coupled THMC processes in the near field and far field of a geological repository and to assess their impact on performance assessment: - during the three phases of repository development: excavation phase, operation phase and post-closure phase; - for three different rocks types: crystalline, argillaceous and tuff; - with specific focus on the issues of: Excavation Damaged Zone (EDZ), permanent property changes of rock masses, and glaciation and permafrost phenomena. The project involves a large number of research teams supported by radioactive waste management agencies or governmental regulatory bodies in Canada, China, Finland, France, Germany, Japan, Sweden and USA, who conducted advanced studies and numerical modelling of coupled THMC processes under five tasks. This report presents the definition of the first phase, Task A-1, of the Task A of the project. The task is a working example of how interaction between THMC modelling and SA analysis could be performed. Starting with the technical definition of the Task A, the report presents the results of preliminary THM calculations with a purpose of an initial appreciation of the phenomena and material properties that must be better understood in subsequent phases. Many simplifications and assumptions were introduced and the results should be considered under these assumptions. Based on the evaluation of the multiple teams' results, a few points of concern were identified that may guide the successive phases of Task A studies: 1. The predicted maximum total stress in the MX-80 bentonite could slightly exceed the 15 MPa design pressure for the container

  13. Roles of bentonite in radioactive waste disposal

    International Nuclear Information System (INIS)

    Suzuki, Keizo

    1995-01-01

    Bentonite is used in radioactive waste disposal from the following points; (1) properties (2) now utilization fields (3) how to use in radioactive waste disposal (4) how much consumption and deposits as source at the present time. Bentonite is produced as alteration products from pyroclastic rocks such as volcanic ash and ryolite, and is clay composed mainly smectite (montmorillonite in general). Therefore, special properties of bentonite such as swelling potential, rheological property, bonding ability, cation exchange capacity and absorption come mainly from properties of montmorillonite. Bentonite has numerous uses such as iron ore pelleizing, civil engineering, green sand molding, cat litter, agricultural chemicals and drilling mud. Consumption of bentonite is about 600-700 x 10 3 tons in Japan and about 10 x 10 6 tons in the world. Roles of bentonite to be expected in radioactive waste disposal are hydraulic conductivity, swelling potential, absorption, mechanical strength, ion diffusion capacity and long-term durability. These properties come from montmorillonite. (author)

  14. Implementation of the full-scale emplacement (FE) experiment at the Mont Terri rock laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Müller, H.R.; Garitte, B.; Vogt, T.; and others

    2017-04-15

    Opalinus Clay is currently being assessed as the host rock for a deep geological repository for high-level and low- and intermediate-level radioactive wastes in Switzerland. Within this framework, the 'Full-Scale Emplacement' (FE) experiment was initiated at the Mont Terri rock laboratory close to the small town of St-Ursanne in Switzerland. The FE experiment simulates, as realistically as possible, the construction, waste emplacement, backfilling and early post-closure evolution of a spent fuel/vitrified high-level waste disposal tunnel according to the Swiss repository concept. The main aim of this multiple heater test is the investigation of repository-induced thermo-hydro-mechanical (THM) coupled effects on the host rock at this scale and the validation of existing coupled THM models. For this, several hundred sensors were installed in the rock, the tunnel lining, the bentonite buffer, the heaters and the plug. This paper is structured according to the implementation timeline of the FE experiment. It documents relevant details about the instrumentation, the tunnel construction, the production of the bentonite blocks and the highly compacted 'granulated bentonite mixture' (GBM), the development and construction of the prototype 'backfilling machine' (BFM) and its testing for horizontal GBM emplacement. Finally, the plug construction and the start of all 3 heaters (with a thermal output of 1350 Watt each) in February 2015 are briefly described. In this paper, measurement results representative of the different experimental steps are also presented. Tunnel construction aspects are discussed on the basis of tunnel wall displacements, permeability testing and relative humidity measurements around the tunnel. GBM densities achieved with the BFM in the different off-site mock-up tests and, finally, in the FE tunnel are presented. Finally, in situ thermal conductivity and temperature measurements recorded during the first heating months

  15. Diffusion of uranium in compacted sodium bentonite

    International Nuclear Information System (INIS)

    Muurinen, A.; Lehikoinen, J.

    1992-09-01

    In the study the diffusion of uranium dissolved from uranium oxide fuel was studied experimentally in compacted sodium bentonite (Wyoming bentonite MX-80). The experiments were carried out by the through-diffusion method. The parameters varied in the study were the density of bentonite, salt content of the solution and redox conditions. Uranium was dissolved under aerobic conditions in order to simulate oxic conditions possibly caused by radiolysis in the repository

  16. Numerical study of the THM effects on the near-field safety of a hypothetical nuclear waste repository - BMT1 of the DECOVALEX III project. Part 1: conceptualization and characterization of the problems and summary of results

    International Nuclear Information System (INIS)

    Chijimatsu, M.; Nguyen, T.S.; Jing, L.; De Jonge, J.; Kohlmeier, M.; Millard, A.; Rejeb, A.; Rutqvist, J.; Souley, M.; Sugita, Y.

    2004-01-01

    Geological disposal of the spent nuclear fuel uses often the concept of multiple barrier systems. In order to predict the performance of these barriers, mathematical models have been developed, verified and validated against analytical solutions, laboratory tests and field experiments within the international DECOVALEX III project. These models in general consider the full coupling of thermal (T), hydraulic (H) and mechanical (M) processes that would prevail in the geological media around the repository. For Bench Mark Test no. 1 (BMT1) of the DECOVALEX III project, seven multinational research teams studied the implications of coupled THM processes on the safety of a hypothetical nuclear waste repository at the near-field and are presented in three accompany papers in this issue. This paper is the first of the three companion papers, which provides the conceptualization and characterization of the BMT1 as well as some general conclusions based on the findings of the numerical studies. It also shows the process of building confidence in the mathematical models by calibration with a reference T-H-M experiment with realistic rock mass conditions and bentonite properties and measured outputs of thermal, hydraulic and mechanical variables

  17. Contribution to the study of cementitious and clayey materials behaviour in the context of deep geological disposal: transport aspect, durability and thermo-hydro-mechanical behaviour

    International Nuclear Information System (INIS)

    Galle, C.

    2011-07-01

    Deep geological formation disposal is the reference solution in France for the management of medium and high activities radioactive waste. In this context, to demonstrate the feasibility of such a disposal, it is necessary to evaluate the long-term performances and the behaviour of the materials engaged in the elaboration of engineered barrier systems (EBS) and waste package elements. The studies mentioned and synthesized in this HDR thesis focused mainly on the convective transport of gas (under pressure gradient) in cementitious matrices, by coupling microstructure aspect (porosity/pores sizes distribution) and hydric environment (water saturation). Works on physico-chemical durability allowed the description of the chemical degradation of cement-based materials in extreme conditions using ammonium nitrate, to increase the materials damaging processes in order to identify functional margins. In relationship with the interim storage management phase, studies related to the behaviour and characterization of concrete submitted to high temperatures (up to 400 C) were also described. Finally, results concerning the gas (H 2 ) overpressure resistance of engineered barriers made of compacted clays were summarized. (author)

  18. Thermo-hydro-mechanical characterization of the Spanish reference clay material for engineered barrier for granite and clay HLW repository: laboratory and small mock up testing

    International Nuclear Information System (INIS)

    Villar, M.V.

    1995-01-01

    This report refers to the work carried out by Technic Geologic Division of CIEMAT (CIEMAT.DT.TG) coordinated by SCK/CEN (Belgium), participating besides UPC-DIT and University of Wales on the framework of CEC Contract F12W-CT91-0102 (DOEO). It presents the results obtained. The total results on the project will be published by CE in the EUR series. The role of CIEMAT in this project was to carry out tests in which the conditions of the clay barrier in the repository were simulated. The interaction of heat coming from the wastes and of water coming from the geological medium has been reproduced on compacted clay blocks. For the performance of tests on high density compacted clay blocks (Task 2.1) and for the cementation and chemical-mineralogical transformation studies two different cells were designed and constructed in stainless steel: a thermohydraulic cell and an alteration cell. The experiments performed in these cells have provided us with a better knowledge of the heat source, hydration system and sensors, as well as interesting data on heat and water diffusion. A revision of the experiments performed on the thermohydraulic cell was presented at the ''International Workshop on Thermomechanics of Clays and Clay Barriers'' held in Bergamo in October'93 (Villar et al. 1993)

  19. Bentonite Permeability at Elevated Temperature

    Directory of Open Access Journals (Sweden)

    Katherine A. Daniels

    2017-01-01

    Full Text Available Repository designs frequently favour geological disposal of radioactive waste with a backfill material occupying void space around the waste. The backfill material must tolerate the high temperatures produced by decaying radioactive waste to prevent its failure or degradation, leading to increased hydraulic conductivity and reduced sealing performance. The results of four experiments investigating the effect of temperature on the permeability of a bentonite backfill are presented. Bentonite is a clay commonly proposed as the backfill in repository designs because of its high swelling capacity and very low permeability. The experiments were conducted in two sets of purpose-built, temperature controlled apparatus, designed to simulate isotropic pressure and constant volume conditions within the testing range of 4–6 MPa average effective stress. The response of bentonite during thermal loading at temperatures up to 200 °C was investigated, extending the previously considered temperature range. The results provide details of bentonite’s intrinsic permeability, total stress, swelling pressure and porewater pressure during thermal cycles. We find that bentonite’s hydraulic properties are sensitive to thermal loading and the type of imposed boundary condition. However, the permeability change is not large and can mostly be accounted for by water viscosity changes. Thus, under 150 °C, temperature has a minimal impact on bentonite’s hydraulic permeability.

  20. THM reduction on water distribution network with chlorine dioxide as disinfectant

    International Nuclear Information System (INIS)

    Ventura, G.; Gorriz, D.; Pascual, E.; Romero, M.

    2009-01-01

    A disinfectant change on water distribution network, by chlorine dioxide in that case, avoids THM formation. In the other hand it creates big doubts about utilization and analytical determination of another oxidant different to chlorine. Just a need to comply the current legislation points us to make a change as the one mentioned above and carried out in DWTP Rio Verde, being managed by Acosol, where the THM formation is been reduced to 80%, according to the new limit of 100μg/l, along the 200 km of the supply network. (Author) 13 refs.

  1. Bentonite erosion by dilute waters in initially saturated bentonite

    International Nuclear Information System (INIS)

    Olin, Markus; Seppaelae, Anniina; Laurila, Teemu; Koskinen, Kari

    2012-01-01

    Document available in extended abstract form only. One scenario of interest for the long-term safety assessment of a spent nuclear fuel repository involves the loss of bentonite buffer material through contact with dilute groundwater at a transmissive fracture interface (SKB 2011, Posiva 2012a). The scenario is based on the stable colloids at low ionic strength: - the cohesive forces of bentonite decrease in low-salinity conditions, and colloids start to dominate and are able to leave the gel-like bentonite on the groundwater bentonite boundary; - after colloid formation, groundwater may carry away the only just released clay colloids; - low-salinity events are most probable during post-glacial conditions, when also pressure gradients are high, causing elevated flow velocity, which may enhance colloidal transport. Therefore, it is very important from the point of view of repository safety assessment to be able to estimate how much bentonite may be lost during a post-glacial event, when the groundwater salinity and velocity, as well as the duration of the event are fixed. It is possible that more than one event will hit the same canister and buffer, and that several canisters and buffers may be jeopardized. The results in the issue so far may be divided into modelling attempts and experimental work. The modelling has been based on two main guidelines: external (Birgersson et al., 2009) and internal friction models (Neretnieks et al., 2009). However, these models have not been validated for erosion, probably due to lack of suitable laboratory data. The latter approach is more ambitious due to lack of fitting parameters, though the internal friction model itself may be varied. The internal friction model has proven to be time-consuming to solve numerically. This work indicates that experiments carried out by Schatz et al. (2012) differ significantly from the predictions obtained from Neretnieks' model. We present our numerical modelling results based on a set of

  2. The bentonite industry in North America

    International Nuclear Information System (INIS)

    Dixon, D.A.; Hnatiw, D.S.J.; Walker, B.T.

    1992-11-01

    The Canadian Nuclear Fuel Waste Management Program is studying a concept for the disposal of nuclear fuel waste at a depth of 500 to 1000 m below the surface in stable crystalline rock of the Canadian Shield. The waste containers would be surrounded by a clay-based buffer material, composed of equal proportions of bentonite clay and silica sand. In the reference disposal concept, some 1.9 x 10 5 Mg of used fuel would be emplaced. This would require 2.5 x 10 6 Mg of bentonite. A review of the bentonite industry in North America was carried out to establish the availability of sufficient high-quality material. There are proven reserves of sodium bentonite clay in excess of 1.5 x 10 8 Mg, and vast supplies are known to exist but not yet proven. The Canadian conceptual disposal vault would require 6 x 10 4 Mg of sodium bentonite each year for 40 years. The bentonite industry of North America has an installed annual production capacity of 2 x 10 7 Mg. A disposal vault would therefore require approximately 2% of the industry capacity. A number of commercial products have been screened for potential suitability for use as a component of the buffer. Ten currently marketed bentonite products have been identified as meeting the initial quality standards for the buffer, and two non-commercial bentonites have been identified as having the potential for use in a disposal vault. (Author) (14 figs., 7 tabs., 18 refs.)

  3. Understanding the Alteration of Bentonite Backfill Using Coupled THMC Modeling for a Long Term Heater Test at the Grimsel Underground Research Lab

    Science.gov (United States)

    Birkholzer, J. T.; Zheng, L.; Xu, H.; Rutqvist, J.

    2017-12-01

    Compacted bentonite is commonly used as backfill material in emplacement tunnels of nuclear waste repositories because of its low permeability, high swelling pressure, and retardation capacity of radionuclide. To assess whether this backfill material can maintain these favorable features when undergoing heating from the waste package and hydration from the host rock, we need a thorough understanding of the thermal, hydrological, mechanical, and chemical evolution of bentonite under disposal conditions. Dedicated field tests integrated with THMC modeling provide an effective way to deepen such understanding. Here, we present coupled THMC models for an in situ heater test which was conducted at the Grimsel Test Site in Switzerland for 18 years. The comprehensive monitoring data obtained in the test provide a unique opportunity to evaluate bentonite integrity and test coupled THMC models. We developed a modeling strategy where conceptual model complexity is increased gradually by adding/testing processes such as Non-Darcian flow, enhanced vapor diffusion, thermal osmosis and different constitutive relationships for permeability/porosity changes due to swelling. The final THMC model explains well all the THM data and the concentration profiles of conservative chemical species. Over the course of modeling the in situ test, we learned that (1) including Non-Darcian flow into the model leads to a significant underestimation of hydration rate of bentonite, (2) chemical data provide an important additional piece of information for calibrating a THM model; (3) key processes needed to reproduce the data include vapor diffusion, as well as porosity and permeability changes due to swelling and thermal osmosis; (4) the concentration profiles of cations (calcium, potassium, magnesium and sodium) were largely shaped by transport processes despite their concentration levels being affected by mineral dissolution/precipitation and cation exchange. The concentration profiles of p

  4. Permeability of highly compacted bentonite

    International Nuclear Information System (INIS)

    Pusch, R.

    1980-12-01

    The object of the study was the water flow through the bentonite which is caused by hydraulic gradients. The study comprised laboratory tests and theoretical considerations. It was found that high bulk densities reduced the permeability to very low values. It was concluded that practically impervious conditions prevail when the gradients are low. Thus with a regional gradient of 10 -2 and a premeability of 10 -13 m/s the flow rate will not be higher than approximately 1 mm in 30 000 years. (G.B.)

  5. Occurrence of THM and NDMA precursors in a watershed: Effect of seasons and anthropogenic pollution.

    Science.gov (United States)

    Aydin, Egemen; Yaman, Fatma Busra; Ates Genceli, Esra; Topuz, Emel; Erdim, Esra; Gurel, Melike; Ipek, Murat; Pehlivanoglu-Mantas, Elif

    2012-06-30

    In pristine watersheds, natural organic matter is the main source of disinfection by-product (DBP) precursors. However, the presence of point or non-point pollution sources in watersheds may lead to increased levels of DBP precursors which in turn form DBPs in the drinking water treatment plant upon chlorination or chloramination. In this study, water samples were collected from a lake used to obtain drinking water for Istanbul as well as its tributaries to investigate the presence of the precursors of two disinfection by-products, trihalomethanes (THM) and N-nitrosodimethylamine (NDMA). In addition, the effect of seasons and the possible relationships between these precursors and water quality parameters were evaluated. The concentrations of THM and NDMA precursors measured as total THM formation potential (TTHMFP) and NDMA formation potential (NDMAFP) ranged between 126 and 1523μg/L THM and NDMA, respectively. Such wide ranges imply that some of the tributaries are affected by anthropogenic pollution sources, which is also supported by high DOC, Cl(-) and NH(3) concentrations. No significant correlation was found between the water quality parameters and DBP formation potential, except for a weak correlation between NDMAFP and DOC concentrations. The effect of the sampling location was more pronounced than the seasonal variation due to anthropogenic pollution in some tributaries and no significant correlation was obtained between the seasons and water quality parameters. Copyright © 2012 Elsevier B.V. All rights reserved.

  6. Assessment Criteria of Bentonite Binding Properties

    Directory of Open Access Journals (Sweden)

    S. Żymankowska-Kumon

    2012-09-01

    Full Text Available The criteria, with which one should be guided at the assessment of the binding properties of bentonites used for moulding sands, areproposed in the paper. Apart from the standard parameter which is the active bentonite content, the unrestrained growth indicator should be taken into account since it seems to be more adequate in the estimation of the sand compression strength. The investigations performed for three kinds of bentonites, applied in the Polish foundry plants, subjected to a high temperature influences indicate, that the pathway of changes of the unrestrained growth indicator is very similar to the pathway of changes of the sand compression strength. Instead, the character of changes of the montmorillonite content in the sand in dependence of the temperature is quite different. The sand exhibits the significant active bentonite content, and the sand compression strength decreases rapidly. The montmorillonite content in bentonite samples was determined by the modern copper complex method of triethylenetetraamine (Cu(II-TET. Tests were performed for bentonites and for sands with those bentonites subjected to high temperatures influences in a range: 100-700ºC.

  7. Rheological Behavior of Bentonite-Polyester Dispersions

    Science.gov (United States)

    Abu-Jdayil, Basim; Al-Omari, Salah Addin

    2013-07-01

    The rheological behavior of a bentonite clay dispersed in unsaturated polyester was investigated. The effects of the solid content and particle size on the steady and transient rheological properties of the dispersions were studied. In addition, two types of bentonite with different Na+/Ca+2 ratio were used in this study. The Herschel-Bulkley and the Weltman models were used to describe the apparent viscosity of the bentonite-polyester composite in relation to the shear rate and shearing time. The bentonite-polyester dispersions were found to exhibit both Newtonian and non-Newtonian behavior. The transition from a Newtonian to a Bingham plastic and then to a shear-thinning material with a yield stress was found to depend on the solid concentration, the particle size, and the type of bentonite. At a low solid content, the apparent viscosity of the bentonite dispersion increased linearly with solid concentration. But a dramatic increase in the apparent viscosity beyond a solid content of 20 wt.% was observed. On the other hand, a thixotropic behavior was detected in bentonite-polyester dispersions with a high solid content and a low particle size. However, this behavior was more pronounced in dispersions with a high Na+/Ca+2 ratio.

  8. Quality assurance of the bentonite material

    International Nuclear Information System (INIS)

    Ahonen, L.; Korkeakoski, P.; Tiljander, M.; Kivikoski, H.; Laaksonen, R.

    2008-05-01

    This report describes a quality assurance chain for the bentonite material acquisition for a nuclear waste disposal repository. Chemical, mineralogical and geotechnical methods, which may be applied in quality control of bentonite are shortly reviewed. As a case study, many of the presented control studies were performed for six different bentonite samples. Chemical analysis is a very reliable research method to control material homogeneity, because the accuracy and repeatability of the study method is extremely good. Accurate mineralogical study of bentonite is a complicated task. X-ray diffractometry is the best method to identify smectite minerals, but quantitative analysis of smectite content remains uncertain. To obtain a better quantitative analysis, development of techniques based on automatic image analysis of SEM images is proposed. General characteristics of bentonite can be obtained by rapid indicator tests, which can be done on the place of reception. These tests are methylene blue test giving information on the cation exchange capacity, swelling index and determination of water absorption. Different methods were used in the determination of cation exchange capacity (CEC) of bentonite. The results indicated differences both between methodologies and between replicate determinations for the same material and method. Additional work should be done to improve the reliability and reproducibility of the methodology. Bentonite contains water in different modes. Thus, different determination methods are used in bentonite studies and they give somewhat dissimilar results. Clay research use frequently the so-called consistency tests (liquid limit, plastic limit and plasticity index). This study method does, however, not seem to be very practical in quality control of bentonite. Therefore, only the determination of liquid limit with fall-cone method is recommended for quality control. (orig.)

  9. Activation of wine bentonite with gamma rays

    International Nuclear Information System (INIS)

    Goranov, N.; Antonov, M.

    1997-01-01

    The action of gamma rays on wine bentonite as well as influence of its adsorption and technologic qualities on the composition and stability of wines against protein darkening and precipitation has been studied. The experiments were carried out with wine bentonite produced in the firm Bentonite and irradiated with doses of 0.4, 0.6, 0.8 and 1.0 MR. White and red wines have been treated with irradiated bentonite under laboratory conditions at 1.0 g/dm 3 . All samples are treated at the same conditions. The flocculation rate of the sediment was determined visually. Samples have been taken 24 h later from the cleared wine layers. The following parameters have been determined: clarification, filtration rate, phenolic compounds, calcium, colour intensity, total extracted substances, etc. The volume of the sediment has been determined also. The control samples have been taken from the same unirradiated wines. The results showed better and faster clarification in on the third, the 20th and the 24th hours with using of gamma-irradiated at doses 0.8 and 1.0 MR. The sediment was the most compact and its volume - the smallest compared to the samples treated with bentonite irradiated with doses of 0.6 and 0.4 MR. This ensures a faster clarification and better filtration of treated wines. The bentonite activated with doses of 0.8 and 1.0 MR adsorbs the phenolic compounds and the complex protein-phenolic molecules better. In the same time it adsorbs less extracted substances compared to untreated bentonite and so preserves all organoleptic properties of wine. The irradiated bentonite adsorbs less the monomers of anthocyan compounds which ensures brighter natural colour of wine. The gamma-rays activation consolidates calcium in the crystal lattice of bentonite particles and in this way eliminates the formation of crystal precipitates

  10. 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)

  11. Quality control and characterization of bentonite materials

    International Nuclear Information System (INIS)

    Kiviranta, L.; Kumpulainen, S.

    2011-12-01

    Before bentonite material is taken into use in performance testing, the quality of the material needs to be checked. Three high grade bentonite materials: two natural Nabentonites from Wyoming, and one natural Ca-bentonite from Milos, were characterized. Each material was characterized using duplicate or triplicate samples in order to study variability in material quality in batches. The procedure consisted of basic acceptance testing (water ratio, CEC, swelling index, liquid limit, and granule size distribution), advanced acceptance testing (exchangeable cations, chemical and mineralogical composition, density, swelling pressure and hydraulic conductivity) and complementary testing (herein surface area, water absorption capacity, montmorillonite composition, grain size distribution and plastic limit). All three materials qualified the requirements set for buffer bentonite for CEC, smectite content, swelling pressure, and hydraulic conductivity. Wyoming bentonites contained approximately 88 wt.% of smectite, and Milos bentonite 79 wt.% of smectite and 3 wt.% of illite. Precision of smectite analyses was ±2 %, and variances in composition of parallel samples within analytical errors, at least for Wyoming bentonites. Accuracy of quantitative analyses for trace minerals such as gypsum, pyrite or carbonates, was however low. As the concentrations of these trace minerals are important for Eh or pH buffering reactions or development of bentonite pore water composition, normative concentrations are recommended to be used instead of mineralogically determined concentrations. The swelling pressures and hydraulic conductivities of different materials were compared using EMDD. Swelling pressure was relatively higher for studied Cabentonite than for the studied Na-bentonites and the difference could not be explained with different smectite contents. Hydraulic conductivities seemed to be similar for all materials. The results of index tests correlated with the smectite content

  12. Reduction of trihalomethane (THM) formation with potassium permanganate in potable water treatment; Aplicacion del permanganato potasico y la formacion de trihalometanos (THM) en los procesos de potabilizacion del agua

    Energy Technology Data Exchange (ETDEWEB)

    Aguirre Pascual, G.; Monforte de Monleon, L.; Tos Boix, s.

    1996-04-01

    Replacing prechlorination with a preoxidation with potassium permanganate in potable water treatment has proved to be an effective way to reduce the formation of THM, organochlorinated compounds known to be carcinogenic. It has been proved that the use of potassium permanganate to reduce the formation of THM is a simple and economic treatment process, having the added affect of improving the taste of the treated water. (Author) 21 refs.

  13. Calculation of saturated hydraulic conductivity of bentonite

    International Nuclear Information System (INIS)

    He Jun

    2006-01-01

    Hydraulic conductivity test has some defects such as weak repeatability, time-consuming. Taking bentonite as dual porous media, the calculation formula of the distance, d 2 , between montmorillonite in intraparticle pores is deduced. Improved calculated method of hydraulic conductivity is obtained using d 2 and Poiseuille law. The method is valid through the comparison with results of test and other methods. The method is very convenient to calculate hydraulic conductivity of bentonite of certain montmorillonite content and void ratio. (authors)

  14. Optimization of bentonite pellet properties

    International Nuclear Information System (INIS)

    Sanden, Torbjoern; Andersson, Linus; Jonsson, Esther; Fritzell, Anni

    2012-01-01

    Document available in extended abstract form only. SKB in Sweden is developing and implementing concepts for the final disposal of spent nuclear fuel. A KBS-3V repository consists of a deposition tunnel with copper canisters containing spent fuel placed in vertical deposition holes. The canisters are embedded in highly compacted bentonite. After emplacement of canisters and bentonite blocks, the tunnels will be backfilled and sealed with an in-situ cast plug at the entrance. The main concept for backfilling the deposition tunnels imply pre compacted blocks of bentonite stacked on a bed of bentonite pellet. The remaining slot between blocks and rock will be filled with bentonite pellets. The work described in this abstract is a part of the ASKAR-project which main goal is to make a system design based on the selected concept for backfilling. Immediately after starting the backfill installation, inflowing water from the rock will come in contact with the pellet filling and thereby influence the characteristics of the pellet filling. The pellet filling helps to increase the average density of the backfill, but one of the most important properties beside this is the water storing capacity which will prevent water from reaching the backfill front where it would disturb and influence the quality of the installation. If water flows through the pellet filling out to the backfilling front, there will be erosion of material which also will affect the quality of the installed backfill. In order to optimize the properties regarding water storing capacity and sensitivity for erosion a number of tests have been made with different pellet types. The tests were made in different scales and with equipment specially designed for the purpose. The performed tests can be divided in four parts: 1. Standard tests (determining water content and density of pellet fillings and individual pellets, compressibility of the pellet fillings and strength of the individual pellets); 2. Erosion

  15. Removal of oil from water by bentonite

    International Nuclear Information System (INIS)

    Moazed, H.; Viraraghavan, T.

    1999-01-01

    Many materials, included activated carbon, peat, coal, fiberglass, polypropylene, organoclay and bentonite have been used for removing oils and grease from water. However, bentonite has been used only rarely for this purpose. In this study Na-bentonite was used to remove oil from oil-in-water emulsions of various kinds such as standard mineral oil, cutting oils, refinery effluent and produced water from production wells at Estevan, Saskatchewan. Removal efficiencies obtained were 85 to 96 per cent for cutting oils, 84 to 86 per cent for produced water and 54 to 87 per cent for refinery effluent. Bentonite proved to be more effective in the removal of oil from oil-in-water emulsions than from actual waste waters; up to 96 percent from oil-in-water emulsions to only 87 per cent from actual waste water. The percentage of oil removed was found to be a function of the amount of bentonite added and the adsorption time up to the equilibrium time. Result also showed that the Langmuir, Freundlich and BET isotherms are well suited to describe the adsorption of oil by bentonite from the various oily waters employed in this study. 15 refs

  16. Hydraulic conductivity of some bentonites in artificial seawater

    International Nuclear Information System (INIS)

    Komine, Hideo; Murakami, Satoshi; Yasuhara, Kazuya

    2011-01-01

    A high-level radioactive waste disposal facility might be built in a coastal area in Japan from the viewpoint of feasible transportation of waste. Therefore, it is important to investigate the effects of seawater on a bentonite-based buffer. This study investigated the influence of seawater on hydraulic conductivity of three common sodium-types of bentonite and one calcium-type bentonite by the laboratory experiments. >From the results of laboratory experiment, this study discussed the influence of seawater on hydraulic conductivity of bentonites from the viewpoints of kinds of bentonite such as exchangeable-cation type and montmorillonite content and dry density of bentonite-based buffer. (author)

  17. GTRF Calculations Using Hydra-TH (L3 Milestone THM.CFD.P5.05)

    International Nuclear Information System (INIS)

    Bakosi, Jozsef; Christon, Mark A.; Francois, Marianne M.; Lowrie, Robert B.; Nourgaliev, Robert

    2012-01-01

    This report describes the work carried out for completion of the Thermal Hydraulics Methods (THM) Level 3 Milestone THM.CFD.P5.05 for the Consortium for Advanced Simulation of Light Water Reactors (CASL). A series of body-fitted computational meshes have been generated by Numeca's Hexpress/Hybrid, a.k.a. 'Spider', meshing technology for the V5H 3 x 3 and 5 x 5 rod bundle geometries and subsequently used to compute the fluid dynamics of grid-to-rod fretting (GTRF). Spider is easy to use, fast, and automatically generates high-quality meshes for extremely complex geometries, required for the GTRF problem. Hydra-TH has been used to carry out large-eddy simulations on both 3 x 3 and 5 x 5 geometries, using different mesh resolutions. The results analyzed show good agreement with Star-CCM+ simulations and experimental data.

  18. GTRF Calculations Using Hydra-TH (L3 Milestone THM.CFD.P5.05)

    Energy Technology Data Exchange (ETDEWEB)

    Bakosi, Jozsef [Los Alamos National Laboratory; Christon, Mark A. [Los Alamos National Laboratory; Francois, Marianne M. [Los Alamos National Laboratory; Lowrie, Robert B. [Los Alamos National Laboratory; Nourgaliev, Robert [Los Alamos National Laboratory

    2012-09-05

    This report describes the work carried out for completion of the Thermal Hydraulics Methods (THM) Level 3 Milestone THM.CFD.P5.05 for the Consortium for Advanced Simulation of Light Water Reactors (CASL). A series of body-fitted computational meshes have been generated by Numeca's Hexpress/Hybrid, a.k.a. 'Spider', meshing technology for the V5H 3 x 3 and 5 x 5 rod bundle geometries and subsequently used to compute the fluid dynamics of grid-to-rod fretting (GTRF). Spider is easy to use, fast, and automatically generates high-quality meshes for extremely complex geometries, required for the GTRF problem. Hydra-TH has been used to carry out large-eddy simulations on both 3 x 3 and 5 x 5 geometries, using different mesh resolutions. The results analyzed show good agreement with Star-CCM+ simulations and experimental data.

  19. Exchangeability of bentonite buffer and backfill materials

    Energy Technology Data Exchange (ETDEWEB)

    Savage, D. [Savage Earth Associates Ltd, Bournemouth (United Kingdom); Arthur, R. [Intera Inc, Ottawa, ON, (Canada); Luukkonen, A.

    2012-08-15

    Clay-based buffer and tunnel backfill materials are important barriers in the KBS-3 repository concept for final disposal of spent nuclear fuel in Finland. One issue that is relevant to material properties is the degree to which different bentonite compositions can be regarded as interchangeable. In Posiva's current repository design, the reference bentonite composition is MX-80, a sodium montmorillonite dominated clay. Posiva would like to be able to use bentonite with Ca-montmorillonite as the dominant clay mineral. However, at this stage, it is not clear what supporting data need to be acquired/defined to be able to place the state of knowledge of Ca-bentonite at the same level as that of Na-bentonite. In this report, the concept of bentonite exchangeability has been evaluated through consideration of how bentonite behaviour may be affected in six key performance-relevant properties, namely (1) mineralogical composition and availability of materials, (2) hydraulic conductivity, (3) mechanical and rheological properties, (4) long-term alteration, (5) colloidal properties, and (6) swelling pressure. The report evaluates implications for both buffer and backfill. Summary conclusions are drawn from these sections to suggest how bentonite exchangeability may be addressed in regulatory assessments of engineered barrier design for a future geological repository for spent fuel in Finland. Some important conclusions are: (a) There are some fundamental differences between Ca- and Na-bentonites such as colloidal behaviour, pore structure and long-term alteration that could affect the exchangeability of these materials as buffer or backfill materials and which should be further evaluated; (b) Additional experimental data are desirable for some issues such as long-term alteration, hydraulic properties and swelling behaviour, (c) The minor mineral content of bentonites is very variable, both between different bentonites and within the same bentonite type, it is not clear

  20. Fabrication and handling of bentonite blocks

    International Nuclear Information System (INIS)

    1978-06-01

    In accordance with the project for the final storage of spent nuclear fuel, the waste will be encapsulated into copper canisters, which will be deposited in a final repository located in rock 500 m below ground level. The canisters will be placed in vertical holes in the bottoms of the tunnels, where the copper cylinders will be surrounded by blocks of highly compacted bentonite. When the blocks are saturated with water and expansion is essentially retained as in the actual case, a very high swelling pressure will arise. The bentonite will be extremely impermeable and thus it will form a barrier against transport of corrosive matters to the canister. The blocks are fabricated by means of cold isostatic pressing of bentonite powder. The base material in the form of powder is enclosed in flexible forms, which are introduced into pressure vessels where the forms are surrounded by oil or water. Thus the powder is compacted into rigid bodies with a bulk density of about 2.2 t/m 3 for ''air dry'' bentonite, which might be compared with a specific density of about 2.7 t/m 3 . The placing of a canister is preceded by piling up bentonite blocks to a level just below the canister lid position, after which the slot around the blocks is filled with bentonite powder. The rest of the blocks are mounted after filling bentonite powder into the inner slot around the canister as well. Finally the storage tunnels will be sealed by filling them with a mixture o02067NRM 0000181 45

  1. Microbial activity in bentonite buffers. Literature study

    Energy Technology Data Exchange (ETDEWEB)

    Ratto, M.; Itavaara, M.

    2012-07-01

    The proposed disposal concept for high-level radioactive wastes involves storing the wastes underground in copper-iron containers embedded in buffer material of compacted bentonite. Hydrogen sulphide production by sulphate-reducing prokaryotes is a potential mechanism that could cause corrosion of waste containers in repository conditions. The prevailing conditions in compacted bentonite buffer will be harsh. The swelling pressure is 7-8 MPa, the amount of free water is low and the average pore and pore throat diameters are small. This literature study aims to assess the potential of microbial activity in bentonite buffers. Literature on the environmental limits of microbial life in extreme conditions and the occurrence of sulphatereducing prokaryotes in extreme environments is reviewed briefly and the results of published studies characterizing microbes and microbial processes in repository conditions or in relevant subsurface environments are presented. The presence of bacteria, including SRBs, has been confirmed in deep groundwater and bentonite-based materials. Sulphate reducers have been detected in various high-pressure environments, and sulphate-reduction based on hydrogen as an energy source is considered a major microbial process in deep subsurface environments. In bentonite, microbial activity is strongly suppressed, mainly due to the low amount of free water and small pores, which limit the transport of microbes and nutrients. Spore-forming bacteria have been shown to survive in compacted bentonite as dormant spores, and they are able to resume a metabolically active state after decompaction. Thus, microbial sulphide production may increase in repository conditions if the dry density of the bentonite buffer is locally reduced. (orig.)

  2. Simulation of bentonite colloid migration through granite

    International Nuclear Information System (INIS)

    Rosicka, Dana; Hokr, Milan

    2012-01-01

    Document available in extended abstract form only. Full text of publication follows: Colloidal bentonite particles generate at the interface of buffer and host rock in spent nuclear fuel repository due to an erosion process and migrate through granite by the water flow. Stability of these colloids and their migration possibilities have been studied on account of radionuclide transport possibility as colloid could carry adsorbed radionuclides in groundwater through granite. That is why a simulation of bentonite colloid migration in the surrounding of a repository might be requested. According to chemical condition as ionic strength and pH, the colloidal particles coagulate into clusters and that influence the migration of particles. The coagulation kinetics of natural bentonite colloids were experimentally studied in many articles, for example by light scattering techniques. We created a model of coagulation of bentonite colloids and simulation of a chosen experiment with use of the multicomponent reactive transport equation. The coagulation model describes clustering of particles due to attractive van der Waals forces as result of collision of particles due to heat fluctuation and different velocity of particles during sedimentation and velocity gradient of water flow. Next, the model includes influence of repulsive electrostatic forces among colloidal particles leading to stability of particles provided high surface charge of colloids. In the model, each group of clusters is transported as one solution component and the kinetics of coagulation are implemented as reactions between the components: a shift of particles among groups of particles with similar migration properties, according to size of the clusters of colloids. The simulation of migration of bentonite colloid through granite using the coagulation model was calibrated according to experiment results. On the basis of the simulation, one can estimate the basic processes that occur during bentonite colloid

  3. Chemical interaction of fresh and saline waters with compacted bentonite

    International Nuclear Information System (INIS)

    Muurinen, A.; Lehikoinen, J.; Melamed, A.; Pitkaenen, P.

    1996-01-01

    The interaction of compacted sodium bentonite with fresh and saline ground-water simulant was studied. The parameters varied in the experiments were the compositions of the solutions and oxygen and carbon dioxide content in the surroundings. The main interests of the study were the chemical changes in the experimental solution, bentonite porewater and bentonite together with the microstructural properties of bentonite. The major processes with fresh water were the diffusion of sodium, potassium, sulphate, bicarbonate and chloride from bentonite to the solution, and the diffusion of calcium and magnesium from the solution into bentonite. The major processes in the experiments with saline water were the diffusion of the sodium, magnesium, sulphate and bicarbonate from bentonite into the solution, and the diffusion of calcium from the solution into bentonite

  4. Evaluation of gas migration characteristics of compacted bentonite and Ca-bentonite mixture

    International Nuclear Information System (INIS)

    Tanaka, Yukihisa; Hironaga, Michihiko

    2014-01-01

    In the current concept of subsurface disposal and near-surface pit disposal for low level radioactive waste, compacted bentonite and Ca-bentonite mixture will be used as an engineered barrier mainly for inhibiting migration of radioactive nuclides, respectively. Hydrogen gas can be generated inside the engineered barrier of subsurface disposal facilities mainly by anaerobic corrosion of metals used for containers, etc. Hydrogen gas can be also generated inside the engineered barrier of near-surface pit disposal facilities mainly by the chemical interaction between aluminum and the alkaline component of cement, or water. If the gas generation rate exceeds the diffusion rate of gas molecules inside of the compacted bentonite and Ca-bentonite mixture, gas will accumulate in the void space inside of the compacted bentonite and Ca-bentonite mixture until breakthrough occurs. It is expected to be not easy for gas to entering into the compacted bentonite mixture as a discrete gaseous phase because the pore of the compacted bentonite and Ca-bentonite mixture is so minute. Therefore in this study, the gas migration characteristics and the effect of gas migration on the hydraulic conductivity of the compacted bentonite and Ca-bentonite mixture are investigated by the gas migration tests. The applicability of the two phase flow model without considering deformability of the specimen is investigated. The applicability of the model of two phase flow through deformable porous media, which was originally developed by CRIEPI, is also investigated. Results of this study imply that : (1) Gas migration mechanism of the compacted bentonite and Ca-bentonite mixture is revealed through gas migration test. (2) Hydraulic conductivity measured after the large gas breakthrough is substantially the same that measured before the gas migration test. (3) Stress change, pore-water pressure change and volume change of the specimen during the gas migration test can be reproduced by the numerical

  5. Sorption behavior of cesium onto bentonite colloid

    International Nuclear Information System (INIS)

    Iijima, Kazuki; Masuda, Tsuguya; Tomura, Tsutomu

    2004-01-01

    It is considered that bentonite colloid might be generated from bentonite which will be used as buffer material in geological disposal system, and can facilitate the migration of radionuclides by means of sorption. In order to examine this characteristic, sorption and desorption experiments of Cs onto bentonite colloid were carried out to obtain its distribution coefficient (Kd) and information on the reversibility of its sorption. In addition, particle size distribution and shape of colloid were investigated and their effect on the sorption behavior was discussed. Kds for Cs were around 20 m 3 /kg for sorption and 30 m 3 /kg for desorption, in which sorbed Cs was desorbed by 8.4x10 -4 mol/l of NaCl solution. These values did not show any dependencies on Cs concentration and duration of sorption and desorption. The first 20% of sorbed Cs was desorbed reversibly at least. Most of colloidal particles were larger than 200 nm and TEM micrographs showed they had only several sheets of the clay crystal. Obtained Kds for colloidal bentonite were larger than those for powdered bentonite. This can be caused by difference of competing ions in the solution, characteristics of contained smectite, or sorption site density. (author)

  6. Bentonite-amended soil special study

    International Nuclear Information System (INIS)

    1989-12-01

    This special study was conducted to assess the viability of soil with a high percentage of bentonite added as an infiltration barrier in the cover of Uranium Mill Tailings Remedial Action (UMTRA) Project disposal cells. To achieve maximum concentration limits (MCLs) at several UMTRA Project sites, covers with a very low permeability are needed. If alternate concentration limits (ACLs) are the appropriate site groundwater compliance strategy, the US Department of Energy (DOE) is required to demonstrate, among other things, that the infiltration to the disposal cell is as low as reasonably achievable, and hence that the cover has a very low permeability. When the study discussed here was begun, the lowest permeability element available was CLAYMAX R , a manufactured liner material constructed of natural material (bentonite clay) between two geosynthetics.The strength of soil-bentonite mixes was measured to see if they could be placed on sideslopes and not pose stability problems. Also evaluated were the hydraulic conductivities of soil-bentonite mixes. If the strengths and permeabilities of soils with a high percentage of bentonite are favorable, the soils may be used as infiltration barriers in current cover designs without changing pile geometries. The scope of work for this study called for a literature review and a two-phased laboratory testing program. This report presents the results of the literature review and the first phase of the testing program

  7. BaM bentonite and some of its properties

    International Nuclear Information System (INIS)

    Matal, Oldřich; Vávra Michal; Kachlík, Martin; Maca, Karel; Kotnour, Petr; Pospíšková, Ilona

    2018-01-01

    BaM bentonite is lime-magnesium bentonite of domestic origin. Its properties were measured experimentally with focus on the following parameters: composition, morphology and particle size distribution, powder bulk density, powder pressing parameters, shear strength, and water saturation. The findings will find use in nuclear safety assessments of engineered bentonite barriers in underground nuclear waste disposal facilities. (orig.)

  8. Bentonite-amended soils special study

    International Nuclear Information System (INIS)

    1990-10-01

    This report presents the results of a two-phased special study to evaluate the viability of soil amended with a high percentage of bentonite as an infiltration barrier in the cover of Uranium Mill Tailings Remedial Action (UMTRA) Project disposal cells. Phase I of the study was initiated in order to examine the feasibility of using bentonite-amended soils as a cover component on sideslopes and topslopes. The Phase I objectives were to test a variety of materials to determine if low hydraulic conductivities were achievable in materials exhibiting sufficient strength and to select suitable materials for further testing. Phase II objectives were to (1) optimize designs -- test materials with various percentages of bentonite added; (2) provide design recommendations; (3) address constructibility concerns; and (4) evaluate long-term performance with respect to desiccation effects on the amended materials

  9. SAXS and TEM Investigation of Bentonite Structure

    International Nuclear Information System (INIS)

    Matusewicz, Michal; Liljestroem, Ville; Muurinen, Arto; Serimaa, Ritva

    2013-01-01

    A preliminary investigation of bentonite structure using Small-Angle X-ray Scattering (SAXS) and Transmission Electron Microscopy (TEM) is presented. Three types of clay were used: unchanged MX-80 bentonite and purified clays with sodium or calcium ions. Quantitative information in nano-scale - basal spacing, mean crystallite size - was obtained from SAXS, which was complemented by TEM to give qualitative information from micron to nanometre scale. SAXS seems to be a more reliable source of quantitative data than TEM. SAXS gives the averaged information about basal spacing. TEM in this study gives more qualitative information, but in a greater resolution range. The presented work is a starting point to combine more methods to obtain a better idea of bentonite structure. (authors)

  10. MANU. Purchase of Bentonite. Process Description

    International Nuclear Information System (INIS)

    Laaksonen, R.

    2010-01-01

    The aim of this study is to describe the entire bentonite purchasing process accurately. This will enable efficient and focused use of information related to the purchasing phase and to each individual bentonite batch. This work continues from the work started in the report by Ahonen et al. (2008), Quality Assurance of the Bentonite Material, Posiva Working Report 2008-33. The current work includes a short enquiry for all relevant and at the time known producers or re-sellers of bentonite. Questions about relevant products suitable for civil engineering use, more specifically nuclear waste disposal site use, were asked together with test methods, typical test results and test standards. The following aspects and opinions have been processed from the results that were obtained during the project. Each seller/producer has a quality management system, QMS (typically ISO 9001), and ability to perform the basic tests, but there is not an established common set of properties to be tested. Some producers are willing to test according to customers' specifications. Posiva could arrange a network of capable laboratories to carry out tests according to its selected standards. This activity should then be accredited with a reasonable testing volume. Before starting the purchase of bentonite at a large scale, Posiva should go through negotiations and audits with each seller in order to make sure that both parties are testing with the same methods and both understand the range where the values of key parameters may lie. A database is needed for gathering statistically relevant information from the bentonite material parameters over the long run. This is needed for determining the limits within which the material parameters should remain in order to be acceptable. Posiva is encouraged to create a process to optimize the test types and the amount of tests should be identified for immediate and long term use. This process ensures the required quality and costs involved. (orig.)

  11. Preparation and characterization of bentonite organo clay

    International Nuclear Information System (INIS)

    Bertagnolli, C.; Almeida Neto, A.F.; Silva, M.G.C.

    2009-01-01

    Bentonite clays organically modified have great potential use for environmental remediation, especially in the separation of organic compounds from the water. The aim of this work was the preparation of organophilic clays from 'Verde-Lodo' bentonite clay with the quaternary ammonium salts cetyl-pyridinium chloride and benzalkonium chloride. The materials obtained were characterized by XRD, thermogravimetric analyses, Helium picnometry, SEM and energy dispersive X-ray techniques. The results show consistently successful synthesis of the organoclay through the increase in the basal spacing, as well as salt elimination picks and presence of carbon and chlorine in the modified clays; they are inexistent elements in the natural clay. (author)

  12. Sorption of natural uranium by algerian bentonite

    International Nuclear Information System (INIS)

    Megouda, N.; Kadi, H.; Hamla, M.S.; Brahimi, H.

    2004-01-01

    Full text.Batch sorption experiments have been used to assess the sorption behaviour of uranium onto natural and drilling bentonites. The operating parameters (pH, aolis-liquid ratio, particle size, time and initial uranium concentration) influenced the rate of adsorption. The distribution coefficient (Kd) range values at equilibrium time are 45.95-1079.26 ml/g and 32.81-463053 ml/g for the drilling and natural bentonites respectively. The equilibrium isotherms show that the data correlate with both Freundlich and Langmuir models

  13. Ion diffusion in compacted bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Lehikoinen, J. [VTT Chemical Technology, Espoo (Finland)

    1999-03-01

    In the study, a two-dimensional molecular-level diffusion model, based on a modified form of the Gouy-Chapman (GC) theory of the electrical double layers, for hydrated ionic species in compacted bentonite was developed. The modifications to the GC theory, which forms the very kernel of the diffusion model, stem from various non-conventional features: ionic hydration, dielectric saturation, finite ion-sizes and specific adsorption. The principal objectives of the study were met. With the aid of the consistent diffusion model, it is a relatively simple matter to explain the experimentally observed macroscopic exclusion for anions as well as the postulated, but greatly controversial, surface diffusion for cations. From purely theoretical grounds, it was possible to show that the apparent diffusivities of cations, anions and neutral molecules (i) do not exhibit order-or-magnitude differences, and (ii) are practically independent of the solution ionic strength used and, consequently, of the distribution coefficient, K{sub d}, unless they experience specific binding onto the substrate surface. It was also of interest to investigate the equilibrium anionic concentration distribution in the pore geometry of the GMM model as a function of the solution ionic strength, and to briefly speculate its consequences to diffusion. An explicit account of the filter-plate effect was taken by developing a computerised macroscopic diffusion model, which is based upon the very robust and efficient Laplace Transform Finite-Difference technique. Finally, the inherent limitations as well as the potential fields of applications of the models were addressed. (orig.) 45 refs.

  14. Ion diffusion in compacted bentonite

    International Nuclear Information System (INIS)

    Lehikoinen, J.

    1999-03-01

    In the study, a two-dimensional molecular-level diffusion model, based on a modified form of the Gouy-Chapman (GC) theory of the electrical double layers, for hydrated ionic species in compacted bentonite was developed. The modifications to the GC theory, which forms the very kernel of the diffusion model, stem from various non-conventional features: ionic hydration, dielectric saturation, finite ion-sizes and specific adsorption. The principal objectives of the study were met. With the aid of the consistent diffusion model, it is a relatively simple matter to explain the experimentally observed macroscopic exclusion for anions as well as the postulated, but greatly controversial, surface diffusion for cations. From purely theoretical grounds, it was possible to show that the apparent diffusivities of cations, anions and neutral molecules (i) do not exhibit order-or-magnitude differences, and (ii) are practically independent of the solution ionic strength used and, consequently, of the distribution coefficient, K d , unless they experience specific binding onto the substrate surface. It was also of interest to investigate the equilibrium anionic concentration distribution in the pore geometry of the GMM model as a function of the solution ionic strength, and to briefly speculate its consequences to diffusion. An explicit account of the filter-plate effect was taken by developing a computerised macroscopic diffusion model, which is based upon the very robust and efficient Laplace Transform Finite-Difference technique. Finally, the inherent limitations as well as the potential fields of applications of the models were addressed. (orig.)

  15. Selfinjection of highly compacted bentonite into rock joints

    International Nuclear Information System (INIS)

    Pusch, R.

    1978-02-01

    When radioactive waste is disposed in bore holes in rocks there will be some space between rock and canister. Other investigations have suggested that the space could be filled with highly compacted bentonite. In this report it is discussed if open joints formed or widened in the surrounding rock after the deposition will be sealed by self-injecting bentonite. Bentonite in contact with water will swell. The flow pattern and properties of the swelling bentonite, the permeability of the extruded bentonite and the viscosity of the extruded bentonite have been investigated. The following statements are done. In the narrow joints that can possibly be opened by various processes, the rate of bentonite extrusion will be very slow except for the first few centimeter move, which may take place in a few mounths. The swelling pressure of the extruded bentonite will decrease rapidly with the distance from the deposition hole. The loss of bentonite extruded through the narrow joints will be negligible. In the outer part of the bentonite zone there will be a successive transition to a very soft, dilute bentonite suspension. It will consist of fairly large particle aggregates which will be stuck where the joint width decreases

  16. Bentonite as a waste isolation pilot plant shaft sealing material

    International Nuclear Information System (INIS)

    Daemen, J.; Ran, Chongwei

    1996-12-01

    Current designs of the shaft sealing system for the Waste Isolation Pilot Plant (WIPP) propose using bentonite as a primary sealing component. The shaft sealing designs anticipate that compacted bentonite sealing components can perform through the 10,000-year regulatory period and beyond. To evaluate the acceptability of bentonite as a sealing material for the WIPP, this report identifies references that deal with the properties and characteristics of bentonite that may affect its behavior in the WIPP environment. This report reviews published studies that discuss using bentonite as sealing material for nuclear waste disposal, environmental restoration, toxic and chemical waste disposal, landfill liners, and applications in the petroleum industry. This report identifies the physical and chemical properties, stability and seal construction technologies of bentonite seals in shafts, especially in a saline brine environment. This report focuses on permeability, swelling pressure, strength, stiffness, longevity, and densification properties of bentonites

  17. Bentonite as a waste isolation pilot plant shaft sealing material

    Energy Technology Data Exchange (ETDEWEB)

    Daemen, J.; Ran, Chongwei [Univ. of Nevada, Reno, NV (United States)

    1996-12-01

    Current designs of the shaft sealing system for the Waste Isolation Pilot Plant (WIPP) propose using bentonite as a primary sealing component. The shaft sealing designs anticipate that compacted bentonite sealing components can perform through the 10,000-year regulatory period and beyond. To evaluate the acceptability of bentonite as a sealing material for the WIPP, this report identifies references that deal with the properties and characteristics of bentonite that may affect its behavior in the WIPP environment. This report reviews published studies that discuss using bentonite as sealing material for nuclear waste disposal, environmental restoration, toxic and chemical waste disposal, landfill liners, and applications in the petroleum industry. This report identifies the physical and chemical properties, stability and seal construction technologies of bentonite seals in shafts, especially in a saline brine environment. This report focuses on permeability, swelling pressure, strength, stiffness, longevity, and densification properties of bentonites.

  18. Modeling Coupled THM Processes and Brine Migration in Salt at High Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Rutqvist, Jonny [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Blanco-Martin, Laura [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Molins, Sergi [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Trebotich, David [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Birkholzer, Jens [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2015-09-01

    In this report, we present FY2015 progress by Lawrence Berkeley National Laboratory (LBNL) related to modeling of coupled thermal-hydrological-mechanical-chemical (THMC) processes in salt and their effect on brine migration at high temperatures. This is a combined milestone report related to milestone Salt R&D Milestone “Modeling Coupled THM Processes and Brine Migration in Salt at High Temperatures” (M3FT-15LB0818012) and the Salt Field Testing Milestone (M3FT-15LB0819022) to support the overall objectives of the salt field test planning.

  19. Modeling Coupled THM Processes and Brine Migration in Salt at High Temperatures

    International Nuclear Information System (INIS)

    Rutqvist, Jonny; Blanco-Martin, Laura; Molins, Sergi; Trebotich, David; Birkholzer, Jens

    2015-01-01

    In this report, we present FY2015 progress by Lawrence Berkeley National Laboratory (LBNL) related to modeling of coupled thermal-hydrological-mechanical-chemical (THMC) processes in salt and their effect on brine migration at high temperatures. This is a combined milestone report related to milestone Salt R&D Milestone ''Modeling Coupled THM Processes and Brine Migration in Salt at High Temperatures'' (M3FT-15LB0818012) and the Salt Field Testing Milestone (M3FT-15LB0819022) to support the overall objectives of the salt field test planning.

  20. Sealing performance assessments of bentonite and bentonite/crushed rock plugs

    International Nuclear Information System (INIS)

    Ouyang, Shoung.

    1990-01-01

    Bentonite and mixtures of bentonite and crushed rock are potential sealing materials for high level nuclear waste repositories. The materials have been used to form cap layers to reduce infiltration for mined waste tailings and can also be used to construct clay liners for municipal as well as industrial waste managements. American Colloid C/S granular dentonite and Apache Leap tuff have been mixed to prepare samples for laboratory flow testing. Bentonite weight percent and crushed tuff gradation are the major variables studied. The sealing performance assessments include high injection pressure flow tests, polyaxial flow tests, high temperature flow tests, and piping tests. The results indicate that an appropriate composition would have at least 25% bentonite by weight mixed with well-graded crushed rock. Hydraulic properties of the mixture plugs may be highly anisotropic if significant particle segregation occurs during sample installation and compaction. Temperature has no negative effects on the sealing performance within the test range from room temperature to 60C. The piping damage to the sealing performance is small if the maximum hydraulic gradient does not exceed 120 and 280 for 25 and 35% bentonite content, respectively. The hydraulic gradients above which flow of bentonite may take place are deemed critical. Analytical work includes the introduction of bentonite occupancy percentage and water content at saturation as two major parameters for the plug design. A permeability model developed is useful for the prediction of permeability in clays. A piping model permits the estimation of critical hydraulic gradient allowed before the flow of bentonite takes place. It can also be used to define the maximum allowable pore diameter of a protective filter layer

  1. Characterization of natural bentonite by NMR

    International Nuclear Information System (INIS)

    Leite, Sidnei Q.M.; Dieguez, Lidia C.; Menezes, Sonia M.C.; San Gil, Rosane A.S.

    1993-01-01

    Solid state NMR as well as several other instrumental chemical analysis techniques were used in order to characterize two natural occurring bentonite. The methodology is described. The NMR spectra, together with the other used techniques suggest that the observed differences are due to iron inclusions in tetrahedral and octahedral sites

  2. Pemanfaatan Bentonite sebagai Media Pembumian Elektroda Batang

    Directory of Open Access Journals (Sweden)

    Winanda Riga Tamma

    2017-03-01

    Full Text Available Sistem pentanahan merupakan suatu sistem yang bertujuan untuk mengamankan sistem tenaga listrik dari gangguan ke tanah maupun gangguan hubung singkat. Pada sistem pentanahan yang baik, resistansi pentanahan harus bernilai dibawah lima ohm. Resistansi pentanahan bergantung pada berbagai aspek antara lain yaitu struktur tanah, kelembapan tanah, dan kandungan yang ada dalam tanah itu sendiri. Dalam pengujian pada penelitian ini akan dilakukan perbaikan pada tanah dengan mencampurkan bentonite ke dalam tanah sebagai media pentanahan. Pencampuran bentonite bertujuan agar mendapatkan nilai resistansi pentanahan yang baik sesuai dengan standar sistem pentanahan. Pengujian dilakukan menggunakan elektroda batang dan alat earth resistance tester dengan metode tiga titik dimana elektroda utama atau elektroda pengukuran diberikan treatment sesuai dengan kondisi yang telah ditentukan. Diharapkan pada pengujian ini akan diketahui dampak dari bentonite terhadap penurunan nilai resistansi pentanahan. Hasil pengujian menunjukkan bahwa dengan mencampurkan bentonite pada media pentanahan, resistansi pentanahan menjadi lebih baik. Meskipun tidak terlalu signifikan, rata-rata penurunan dari setiap masing-masing treatment adalah sebesar 2 ohm.

  3. Fe-bentonite. Experiments and modelling of the interactions of bentonites with iron

    Energy Technology Data Exchange (ETDEWEB)

    Herbert, Horst-Juergen; Xie, Mingliang [Gesellschaft fuer Anlagen- und Reaktorsicherheit mbH (GRS), Koeln (Germany); Kasbohm, Joern; Lan, Nguyen T. [Greifswald Univ. (Germany); Hoang Thi Minh Thao [Hanoi Univ. of Science (Viet Nam)

    2011-11-15

    The main objectives of this study were to enhance the understanding of the interactions of bentonites with steel containers in the near field of a repository in salt formations and to determine missing experimental thermo-hydraulical-chemical and mineralogical data needed for the THC modelling of the interactions of bentonites with iron. At the beginning of this project a literature review helped to clarify the state of the art regarding the above mentioned objectives prior to the start of the experimental work. In the following experimental programme the hydraulic changes in the pore space of compacted MX80 bentonites containing metallic iron powder and in contact with three solutions of different ionic strength containing different concentrations of Fe{sup 2+} have been investigated. The alterations of MX80 and several other bentonites have been assessed in contact with the low ionic strength Opalinus Clay Pore Water (OCPW) and the saturated salt solutions NaCl solution and IP21 solution. Under repository relevant boundary conditions we determined on compacted MX80 samples with the raw density of 1.6 g/cm{sup 3} simultaneously interdependent properties like swelling pressures, hydraulic parameters (permeabilities and porosities), mineralogical data (changes of the smectite composition and iron corrosion products), transport parameters (diffusion coefficients) and thermal data (temperature dependent reaction progresses). The information and data resulting from the experiments have been used in geochemical modelling calculations and the existing possibilities and limitations to simulate these very complex near field processes were demonstrated. The main conclusion of this study is that the alteration of bentonites in contact with iron is accentuated and accelerated. Alterations in contact with solutions of different ionic strength identified by the authors in previous studies were found be much more intensive in contact with metallic iron and at elevated

  4. Corrosion of carbon steel in contact with bentonite

    International Nuclear Information System (INIS)

    Dobrev, D.; Vokal, A.; Bruha, P.

    2010-01-01

    Document available in extended abstract form only. Carbon steel canisters were chosen in a number of disposal concepts as reference material for disposal canisters. The corrosion rates of carbon steels in water solution both in aerobic and anaerobic conditions are well known, but only scarce data are available for corrosion behaviour of carbon steels in contact with bentonite. A special apparatus, which enables to measure corrosion rate of carbon steels under conditions simulating conditions in a repository, namely in contact with bentonite under high pressure and elevated temperatures was therefore prepared to study: - Corrosion rate of carbon steels in direct contact with bentonite in comparison with corrosion rate of carbon steels in synthetic bentonite pore water. - Influence of corrosion products on bentonite. The apparatus is composed of corrosion chamber containing a carbon steel disc in direct contact with compacted bentonite. Synthetic granitic water is above compacted bentonite under high pressure (50 - 100 bar) to simulate hydrostatic pressure in a repository. The experiments can be carried out under various temperatures. Bentonites used for experiments were Na-type of bentonite Volclay KWK 80 - 20 and Ca-Mg Czech bentonite from deposit Rokle. Before adding water into corrosion system the corrosion chamber was purged by nitrogen gas. The saturation of bentonite and corrosion rate were monitored by measuring consumption of water, pressure increase caused by swelling pressure of bentonite and by generation of hydrogen. Corrosion rate was also determined after corrosion experiments from weight loss of samples. The results of experiments show that the corrosion behaviour of carbon steels in contact with bentonite is very different from corrosion of carbon steels in water simulating bentonite pore water solution. The corrosion rates of carbon steel in contact with bentonite reached after 30 days of corrosion the values approaching 40 mm/yr contrary to values

  5. A validation study for the gas migration modelling of the compacted bentonite using existing experiment data

    International Nuclear Information System (INIS)

    Tawara, Y.; Mori, K.; Tada, K.; Shimura, T.; Sato, S.; Yamamoto, S.; Hayashi, H.

    2010-01-01

    gas to enter the water-saturated bentonite without propagation of pressure-induced pathway. In this validation study, we have adopted here two computer codes GETFLOWS and Code B right which are based on different conceptual models, respectively. GETFLOWS is the conventional non-isothermal multi-phase fluid-flow code. However pressure-induced macroscopic pathway propagation of porous media is incorporated by changing porosity and permeability explicitly depending on the pore pressure distribution. Code B right is so called coupled THM code and can be applied to non-isothermal two-phase flow in deformable porous media. Automatic inversion code namely UCODE-2005, which was developed by U.S Geological Survey, was used with GETFLOWS. Good matching was attained reasonably between the simulated and observed flow rate in both GETFLOWS and Code-Bright. However when we neglected the pressure-induced pathway propagations, any combinations of flow parameters could not provide a reasonable match between simulated and observed results. This also means that the capillary threshold for gas entry into water-saturated bentonite exists, suggesting consideration of unconventional two phase flow. On the other hand, the identified residual water saturation eventually, which can reproduce observed behaviour well, became extremely high. When we consider long-term behaviour including the re-saturation period after closure of disposal system, it is not available directly as the parameter of the unsaturated bentonite. The identified residual water saturation is only applicable to the fully-water saturated environments. The future work will focus on the gas flow in unsaturated bentonite using experimental data from not only laboratory but also in-situ data. In addition, we are planning to develop the modelling technique of long-term water and gas migration behaviour in the EBS which includes both re-saturation and gas migration phase considering the contribution of THMC coupled phenomena

  6. STUDY OF THERMAL AND ACID STABILITY OF BENTONITE CLAY

    Directory of Open Access Journals (Sweden)

    Karna Wijaya

    2010-06-01

    Full Text Available The thermal and acid stability of the bentonite clays (Na- and Ca-bentonite have been tested. The thermal stability testing has been carried out by heating 5 gram of the clays  for five hours at 200, 300 and 500 °C respectively, meanwhile acid stability testing was performed by immersing 5 gram clays into 100 mL sulphuric acid 1M, 2M and 3M for 24 hours. The tested clays, then were characterized by means of X-Ray difractometry and IR-spectroscopy methods. The characterization results showed that upon heating, both Ca- and Na-bentonites indicated same thermal stability. However, upon acid treatment, Na-bentonite was found relatively stabiler and more resistance then Ca-bentonite.   Keywords: bentonite, clay, thermal stability, acid stability.

  7. Bentonite. Geotechnical barrier and source for microbial life

    Energy Technology Data Exchange (ETDEWEB)

    Matschiavelli, Nicole; Kluge, Sindy; Cherkouk, Andrea [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). HZDR Young Investigator Group; Steglich, Jennifer

    2017-06-01

    Due to their properties, namely a high swelling capacity and a low hydraulic conductivity, Bentonites fulfil as geotechnical barrier a sealing and buffering function in the nuclear waste repository. Depending on the mineral composition Bentonites contain many suitable electron-donors and -acceptors, enabling potential microbial life. For the potential repository of highly radioactive waste the microbial mediated transformation of Bentonite could influence its properties as a barrier material. Microcosms were set up containing Bentonite and anaerobic synthetic Opalinus-clay-pore water solution under an N{sub 2}/CO{sub 2}-atmosphere to elucidate the microbial potential within selected Bentonites. Substrates like acetate and lactate were supplemented to stimulate potential microbial activity. First results show that bentonites represent a source for microbial life, demonstrated by the consumption of lactate and the formation of pyruvate. Furthermore, microbial iron-reduction was determined, which plays a crucial role in Betonite-transformation.

  8. Bentonite. Geotechnical barrier and source for microbial life

    International Nuclear Information System (INIS)

    Matschiavelli, Nicole; Kluge, Sindy; Cherkouk, Andrea; Steglich, Jennifer

    2017-01-01

    Due to their properties, namely a high swelling capacity and a low hydraulic conductivity, Bentonites fulfil as geotechnical barrier a sealing and buffering function in the nuclear waste repository. Depending on the mineral composition Bentonites contain many suitable electron-donors and -acceptors, enabling potential microbial life. For the potential repository of highly radioactive waste the microbial mediated transformation of Bentonite could influence its properties as a barrier material. Microcosms were set up containing Bentonite and anaerobic synthetic Opalinus-clay-pore water solution under an N_2/CO_2-atmosphere to elucidate the microbial potential within selected Bentonites. Substrates like acetate and lactate were supplemented to stimulate potential microbial activity. First results show that bentonites represent a source for microbial life, demonstrated by the consumption of lactate and the formation of pyruvate. Furthermore, microbial iron-reduction was determined, which plays a crucial role in Betonite-transformation.

  9. FEBEX bentonite colloid stability in ground water

    Energy Technology Data Exchange (ETDEWEB)

    Seher, H.; Schaefer, T.; Geckeis, H. [Inst. fuer Nukleare Entsorgung (INE), Forschungszentrum Karlsruhe, 76021 Karlsruhe (Germany)]. e-mail: holger.seher@ine.fzk .de; Fanghaenel, T. [Ruprecht-Karls-Univ. Heidelberg, Physikalisch-Chemisches In st., D-69120 Heidelberg (Germany)

    2007-06-15

    Coagulation experiments are accomplished to identify the geochemical conditions for the stability of Febex bentonite colloids in granite ground water. The experiments are carried out by varying pH, ionic strength and type of electrolyte. The dynamic light scattering technique (photon correlation spectroscopy) is used to measure the size evolution of the colloids with time. Agglomeration rates are higher in MgCl{sub 2} and CaCl{sub 2} than in NaCl solution. Relative agglomeration rates follow approximately the Schulze-Hardy rule. Increasing agglomeration rates at pH>8 are observed in experiments with MgCl{sub 2} and CaCl{sub 2} which are, however, caused by coprecipitation phenomena. Bentonite colloid stability fields derived from the colloid agglomeration experiments predict low colloid stabilization in granite ground water taken from Aespoe, Sweden, and relatively high colloid stability in Grimsel ground water (Switzerland)

  10. Swelling characteristics of Gaomiaozi bentonite and its prediction

    Directory of Open Access Journals (Sweden)

    De'an Sun

    2014-04-01

    Full Text Available Gaomiaozi (GMZ bentonite has been chosen as a possible matrix material of buffers/backfills in the deep geological disposal to isolate the high-level radioactive waste (HLRW in China. In the Gaomiaozi deposit area, calcium bentonite in the near surface zone and sodium bentonite in the deeper zone are observed. The swelling characteristics of GMZ sodium and calcium bentonites and their mixtures with sand wetted with distilled water were studied in the present work. The test results show that the relationship between the void ratio and swelling pressure of compacted GMZ bentonite-sand mixtures at full saturation is independent of the initial conditions such as the initial dry density and water content, but dependent on the ratio of bentonite to sand. An empirical method was accordingly proposed allowing the prediction of the swelling deformation and swelling pressure with different initial densities and bentonite-sand ratios when in saturated conditions. Finally, the swelling capacities of GMZ Na- and Ca-bentonites and Kunigel Na-bentonite are compared.

  11. Study on the basic property of Gaomiaozi bentonite, inner mongolia

    International Nuclear Information System (INIS)

    Liu Yuemiao; Xu Guoqing; Liu Shufen; Chen Zhangru

    2001-01-01

    Buffer/backfill material layer is one of important engineered barriers in the HLW geological repository. The geologic setting of Gaomiaozi bentonite deposit is introduced, and the mineral composition, physical and chemical property, basic geotechnical property, swelling property and permeability of highly compacted bentonite of main ore bed has been studied. The study results show that montmorillonite content of Gaomiaozi bentonite is relatively high, physical and chemical property, geotechnical property and impermeability are good. So Gaomiaozi bentonite deposit could be regarded as supply base of buffer/backfill material for HLW geological repository

  12. Synthesis of PDLLA/PLLA-bentonite nanocomposite through sonication

    International Nuclear Information System (INIS)

    Sitompul, Johnner; Setyawan, Daru; Kim, Daniel Young Joon; Lee, Hyung Woo

    2016-01-01

    This paper concerns the synthesis of poly(D,L-lactic acid)/poly(L-lactic acid) bentonite nanocomposites. Poly (D,L-lactic acid) (PDLLA) was synthesized using lactic acid through the ZnO-catalyzed direct polycondensation method at vacuum pressure and poly(L-lactic acid) (PLLA) was synthesized with L-lactide by ring-opening polymerization method. The PDLLA/PLLA-bentonite nanocomposite films were synthesized using the solvent casting method. The nanoclay, bentonite, was prepared using the solution-intercalation method by dissolving the nanoparticles into chloroform before sonication. In this study, PDLLA/PLLA-bentonite nanocomposite films were produced using variable amounts of nanoclay and sonication times during the mixing of PDLLA/PLLA and bentonite. The properties of the PDLLA/PLLA nanocomposites were then characterized using the X-ray Diffraction (XRD), Universal Testing Machine (UTM), Water Vapor Permeability (WVP) tests, and the enzymatic biodegradability test. The XRD test was used to measure the intercalation of nanoclay layers in the PDLLA/PLLA matrix and the PDLLA/PLLA-bentonite intercalated nanocomposite films. It was found through these various tests that adding bentonite to the PDLLA/PLLA increases tensile strength to 56.76 MP. Furthermore, the biodegradability increases as well as the barrier properties of the polymers The different sonication time used during the mixing of the polymer solution with bentonite also affected the properties of the PDLLA/PLLA-bentonite nanocomposite films.

  13. Analysis of corrosion products of carbon steel in wet bentonite

    International Nuclear Information System (INIS)

    Osada, Kazuo; Nagano, Tetsushi; Nakayama, Shinichi; Muraoka, Susumu

    1992-02-01

    As a part of evaluation of the long-term durability for the overpack containers for high-level radioactive waste, we have conducted corrosion tests for carbon steel in wet bentonite, a candidate buffer material. The corrosion rates were evaluated by weight difference of carbon steel and corrosion products were analyzed by Fourier transform infrared spectroscopy (FT-IR) and colorimetry. At 40degC, the corrosion rate of carbon steel in wet bentonite was smaller than that in pure water. At 95degC, however, the corrosion rate in wet bentonite was much higher than that in pure water. This high corrosion rate in wet bentonite at 95degC was considered to result from evaporation of moisture in bentonite in contact with the metal. This evaporation led to dryness and then to shrinkage of the bentonite, which generated ununiform contact of the metal with bentonite. Probably, this ununiform contact promoted the local corrosion. The locally corroded parts of specimen in wet bentonite at 95degC were analyzed by Fourier transform infrared microspectroscopy (micro-FT-IR), and lepidocrocite γ-FeO(OH) was found as well as goethite α-FeO(OH). In wet bentonite at 95degC, hematite α-Fe 2 O 3 was identified by means of colorimetry. (author)

  14. Synthesis of PDLLA/PLLA-bentonite nanocomposite through sonication

    Energy Technology Data Exchange (ETDEWEB)

    Sitompul, Johnner, E-mail: sitompul@che.itb.ac.id; Setyawan, Daru, E-mail: daru.setyawan@gmail.com; Kim, Daniel Young Joon, E-mail: daniel.kim12321@gmail.com [Department of Chemical Engineering, Faculty of Industrial Technology, Institute of Technology Bandung Jl. Ganesha 10, Bandung, West Java, 40132 (Indonesia); Lee, Hyung Woo, E-mail: leehw@che.itb.ac.id [Department of Chemical Engineering, Faculty of Industrial Technology, Institute of Technology Bandung Jl. Ganesha 10, Bandung, West Java, 40132 (Indonesia); Research and Business Foundation, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi, 440-746 (Korea, Republic of)

    2016-04-19

    This paper concerns the synthesis of poly(D,L-lactic acid)/poly(L-lactic acid) bentonite nanocomposites. Poly (D,L-lactic acid) (PDLLA) was synthesized using lactic acid through the ZnO-catalyzed direct polycondensation method at vacuum pressure and poly(L-lactic acid) (PLLA) was synthesized with L-lactide by ring-opening polymerization method. The PDLLA/PLLA-bentonite nanocomposite films were synthesized using the solvent casting method. The nanoclay, bentonite, was prepared using the solution-intercalation method by dissolving the nanoparticles into chloroform before sonication. In this study, PDLLA/PLLA-bentonite nanocomposite films were produced using variable amounts of nanoclay and sonication times during the mixing of PDLLA/PLLA and bentonite. The properties of the PDLLA/PLLA nanocomposites were then characterized using the X-ray Diffraction (XRD), Universal Testing Machine (UTM), Water Vapor Permeability (WVP) tests, and the enzymatic biodegradability test. The XRD test was used to measure the intercalation of nanoclay layers in the PDLLA/PLLA matrix and the PDLLA/PLLA-bentonite intercalated nanocomposite films. It was found through these various tests that adding bentonite to the PDLLA/PLLA increases tensile strength to 56.76 MP. Furthermore, the biodegradability increases as well as the barrier properties of the polymers The different sonication time used during the mixing of the polymer solution with bentonite also affected the properties of the PDLLA/PLLA-bentonite nanocomposite films.

  15. Immobilization of spent Bentonite by using cement matrix

    International Nuclear Information System (INIS)

    Isman MT; Endro-Kismolo

    1996-01-01

    Investigation of spent bentonite immobilization by using cement was done. The purpose of the investigation was to know the performance of cement in binding bentonite waste. The investigation was done by adding cement, water, and bentonite waste into a container and string until the mixture became homogenous. The mixture was put into a polyethylene tube (3.5 cm in diameter and 4 cm high) and it was cured up to 28 days. The specific weight of the monolith block was then calculated, and the compressive strength and the leaching rate in ground water and sea water was tested. The mass ratio of water to cement was 0.4. The variable investigated was the mass ratio of bentonite to cement. The immobilized bentonite waste was natural bentonite waste and activated bentonite waste. The result of the investigation showed that cement was good for binding bentonite waste. The maximum binding mass ratio of bentonite to cement was 0.4. In this condition the specific weight of the monolith block was 2.177 gram/cm 3 , its compressive strength was 22.6 N/mm 2 , and the leaching rate for 90 days in ground water and sea water was 5.7 x 10 -4 gram cm -2 day -1

  16. Borehole sealing with highly compactd Na bentonite

    International Nuclear Information System (INIS)

    Pusch, R.

    1981-12-01

    This report describes the use of highly compacted Na bentonite for borehole plugging. Bentonites have an extremely low permeability and a low diffusivity, and a swelling ability which produces a nonleaching boundary between clay and rock if the initial bulk density of the bentonite is sufficiently high. The suggested technique, which is applicable to long vertical, and inclined, as well as horizontal boreholes, is based on the use of perforated copper pipes to insert elements of compacted bentonite. Such pipe segments are connected at the rock surface and successively inserted in the hole. When the hole is equipped, the clay takes up water spontaneously and swells through the perforation, and ultimately forms an almost completely homogenous clay core. It embeds the pipe which is left in the hole. Several tests were conducted in the laboratory and one field test was run in Stripa. They all showed that a gel soon fills the slot between the pipe and the confinement which had the form of metal pipes in the laboratory investigations. Subsequently, more clay migrates through the perforation and produces a stiff clay filling in the slot. The redistribution of minerals, leading ultimately to a high degree of homogeneity, can be described as a diffusion process. The rate of redistribution depends on the joint geometry and water flow pattern in the rock. In the rock with an average joint frequence of one per meter or higher, very good homogeneity and sealing ability of the clay are expected within a few months after the application of the plug. (author)

  17. Using bentonite for NPP liquid waste treatment

    International Nuclear Information System (INIS)

    Bui Dang Hanh

    2015-01-01

    During operation, nuclear power plants (NPPs) release a large quantity of water waste containing radionuclides required treatment for protection of the radiation workers and the environment. This paper introduces processes used to treat water waste from Paks NPP in Hungary and it also presents the results of a study on the use of Vietnamese bentonite to remove radioactive Caesium from a simulated water waste containing Cs. (author)

  18. Stability of bentonite gels in crystalline rock

    International Nuclear Information System (INIS)

    Pusch, R.

    1983-02-01

    The present, extended study comprises a derivation of a simple rock model as a basis for calculation of the penetration rate of bentonite and of the groundwater flow rate, which is a determinant of the erodibility of the protruding clay film. This model, which is representative of a gross permeability of about 10 -8 - 10 -9 m/s, implies a spectrum of slot-shaped joints with apertures ranging between 0.1 and 0.5 mm. It is concluded that less than 2percent of the highly compacted bentonite will be lost into traversing joints in 10 6 years. A closer analysis, in which also Poiseuille retardation and short-term experiments were taken into account, even suggests that the penetration into the considered joints will be less than that. The penetration rate is expected to be 1 decimeter in a few hundred years. The risk of erosion by flowing groundwater was estimated by comparing clay particle bond strength, evaluated from viscometer tests, and theoretically derived drag forces, the conclusion being that the maximum expected water flow rate in the widest joints of the rock model (4 times 10 -4 m/s) is not sufficient to disrupt the gel front or the large individual clay flocs that may exist at this front. The experiments support the conclusion that erosion will not be a source of bentonite loss. A worst case scenario with a shear zone being developed across deposition holes is finally considered and in addition to this, the conditions in the fracture-rich tunnel floor at the upper end of the deposition holes are also analysed. This study shows that even if the rock is much more fractured than normal conditions would imply, the bentonite loss is expected to be very moderate and without substantial effect on the barrier functions of the remaining clay cores in the deposition holes. (author)

  19. THM-GTRF: New Spider meshes, New Hydra-TH runs

    Energy Technology Data Exchange (ETDEWEB)

    Bakosi, Jozsef [Los Alamos National Laboratory; Christon, Mark A. [Los Alamos National Laboratory; Francois, Marianne M. [Los Alamos National Laboratory; Lowrie, Robert B. [Los Alamos National Laboratory; Nourgaliev, Robert [Los Alamos National Laboratory

    2012-06-20

    Progress is reported on computational capabilities for the grid-to-rod-fretting (GTRF) problem of pressurized water reactors. Numeca's Hexpress/Hybrid mesh generator is demonstrated as an excellent alternative to generating computational meshes for complex flow geometries, such as in GTRF. Mesh assessment is carried out using standard industrial computational fluid dynamics practices. Hydra-TH, a simulation code developed at LANL for reactor thermal-hydraulics, is demonstrated on hybrid meshes, containing different element types. A series of new Hydra-TH calculations has been carried out collecting turbulence statistics. Preliminary results on the newly generated meshes are discussed; full analysis will be documented in the L3 milestone, THM.CFD.P5.05, Sept. 2012.

  20. Thermal characteristics of highly compressed bentonite

    International Nuclear Information System (INIS)

    Sueoka, Tooru; Kobayashi, Atsushi; Imamura, S.; Ogawa, Terushige; Murata, Shigemi.

    1990-01-01

    In the disposal of high level radioactive wastes in strata, it is planned to protect the canisters enclosing wastes with buffer materials such as overpacks and clay, therefore, the examination of artificial barrier materials is an important problem. The concept of the disposal in strata and the soil mechanics characteristics of highly compressed bentonite as an artificial barrier material were already reported. In this study, the basic experiment on the thermal characteristics of highly compressed bentonite was carried out, therefore, it is reported. The thermal conductivity of buffer materials is important because the possibility that it determines the temperature of solidified bodies and canisters is high, and the buffer materials may cause the thermal degeneration due to high temperature. Thermophysical properties are roughly divided into thermodynamic property, transport property and optical property. The basic principle of measured thermal conductivity and thermal diffusivity, the kinds of the measuring method and so on are explained. As for the measurement of the thermal conductivity of highly compressed bentonite, the experimental setup, the procedure, samples and the results are reported. (K.I.)

  1. Hydrothermal alterations of Bentonites in Almeria (Spain)

    International Nuclear Information System (INIS)

    Linares Gonzalez, J.; Barahona Fernandez, E.; Huertas Garcia, F.; Caballero Mesa, E.; Cuadros Ojeda, J.

    1996-01-01

    The use of bentonite as backfilling and sealing material in the high level radioactive waste disposals has been treated in previous studies accomplished by different authors. However, the use of this clayey barrier needs the resolution of different problems so that its efficiency will be enhanced. between those could be cited the study of the actual capacity of sealing the space around the canister and the accommodation to the pressure of the rocky environment; the possible variations in plasticity; the diffusion and reaction processes that can be produced through the barrier by groundwater, the capacity of radionuclides adsorption, etc. These studies, show that the bentonites with high content in smectite fulfill satisfactorily with the physical and chemical conditions to be used as sealing material, but it is known that the smectite can be unstable in diagenetic conditions similar to those are given in a deep repository of radioactive wastes, being transformed into illite. A conclusion of immediate interest is deduced from this last study. The bentonites used as sealing material in radioactive waste repositories must no contain Na as interlayer cation since it is very easily exchangeable by K. It is better to select those smectites with Ca and Mg that detain the entry of K in the interlayer and as a consequence the transformation process of smectite into illite is made more difficult. (Author)

  2. A comparison of nano bentonite and some nano chemical additives to improve drilling fluid using local clay and commercial bentonites

    Directory of Open Access Journals (Sweden)

    Nada S. Al-Zubaidi

    2017-09-01

    In the second part, a commercial bentonite was used and mixed with nano commercial bentonite and nano chemical materials (MgO, TiO2, and graphene at 0.005, 0.01, 0.05, 0.1, 0.2 and 0.4 wt% concentrations. The results showed that nano commercial bentonite gives the same filtration behavior of graphene, whereas, the plastic viscosity, yield point and apparent viscosity were the same when using nano commercial bentonite, TiO2 and graphene. The best results were obtained with MgO addition, whereby the filter loss decreased to 35% with a higher value of yield point.

  3. Influence of selected factors on strontium sorption on bentonites

    International Nuclear Information System (INIS)

    Galambos, M.; Kufcakova, J.; Rajec, P.

    2007-01-01

    Sorption on bentonite will play an important role in retarding the migration of radionuclides from a waste repository. Bentonite is a natural clay and one of the most promising candidates for use as a buffer material in the geological disposal systems for high-level nuclear waste. It is intended to isolate metal canisters with highly radioactive waste products from the surrounding rocks because of its ability to retard the movement of radionuclides by sorption. Bentonite is characterized by low permeability, water swelling capability and excellent sorption potential for cationic radionuclides. To correctly assess the sorption potential of radionuclides on bentonite is essential for the development of predictive migration models. The sorption of strontium on bentonite from different Slovak deposits - Jelsovy potok, Kopernica and Lieskovec has been investigated under various experimental conditions, such as contact time, sorbate concentrations, presence of complementary cation. Sorption was studied using the batch technique. The uptake of Sr was rapid and equilibrium was reached almost instantaneously. The instantaneous uptake may be due to adsorption and/or exchange of the metal with some ions on the surface of the adsorbent. The best sorption characteristics distinguish bentonite Kopernica, sorption capacity for Sr of the fraction under 45 mm is 0,48 mmol·g -1 for Sr. The highest values of distribution coefficient were reached for the bentonite Jelsovy potok. Radiation stability has been investigated, the higher sorption parameters were observed for the irradiated bentonites, which can be explained by the increase of specific surface of the bentonite samples. The presence of complementary cations depresses the sorption of Sr on bentonite. Cations Ca 2+ exhibit higher effect on cesium sorption than the Na 2+ ions. Results indicate that the sorption of Sr 2+ on bentonite will be affected by the presence of high concentrations of various salts in the waste water

  4. MANU. Handling of bentonite prior buffer block manufacturing

    International Nuclear Information System (INIS)

    Laaksonen, R.

    2010-01-01

    The aim of this study is to describe the entire bentonite handling process starting from freight from harbour to storage facility and ending up to the manufacturing filling process of the bentonite block moulds. This work describes the bentonite handling prior to the process in which bentonite blocks are manufactured in great quantities. This work included a study of relevant Nordic and international well documented cases of storage, processing and techniques involving bentonite material. Information about storage and handling processes from producers or re-sellers of bentonite was collected while keeping in mind the requirements coming from the Posiva side. Also a limited experiment was made for humidification of different material types. This work includes a detailed description of methods and equipment needed for bentonite storage and processing. Posiva Oy used Jauhetekniikka Oy as a consultant to prepare handling process flow charts for bentonite. Jauhetekniikka Oy also evaluated the content of this report. The handling of bentonite was based on the assumption that bentonite process work is done in one factory for 11 months of work time while the weekly volume is around 41-45 tons. Storage space needed in this case is about 300 tons of bentonite which equals about seven weeks of raw material consumption. This work concluded several things to be carefully considered: sampling at various phases of the process, the air quality at the production/storage facilities (humidity and temperature), the level of automation/process control of the manufacturing process and the means of producing/saving data from different phases of the process. (orig.)

  5. Modelling interaction of deep groundwaters with bentonite and radionuclide speciation

    International Nuclear Information System (INIS)

    Wanner, H.

    1986-04-01

    In the safety analysis recently reported for a potential Swiss high-level waste repository, radionuclide speciation and solubility limits are calculated for expected granitic groundwater conditions. With the objective of deriving a more realistic description of radionuclide release from the near-field, an investigation has been initiated to quantitatively specify the chemistry of the near-field. In the Swiss case, the main components of the near-field are the glass waste-matrix, a thick steel canister horizontally emplaced in a drift, and a backfill of highly compacted sodium bentonite. This report describes a thermodynamic model which is used to estimate the chemical composition of the pore water in compacted sodium bentonite. Solubility limits and speciation of important actinides and the fission product technetium in the bentonite pore water are then calculated. The model is based on available experimental data on the interaction of sodium bentonite and groundwater and represents means of extrapolation from laboratory data to repository conditions. The modelled composition of the pore water of compacted sodium bentonite, as well as the various compositions resulting from the long-term extrapolation, are used to estimate radionuclide solubilities in the near-field of a deep repository. From the chemical point of view, calcium bentonite seems to be more stable than sodium bentonite in the presence of Swiss Reference Groundwater. Since the effect of calcium bentonite on the groundwater chemical composition will be considerably less marked than that of sodium bentonite, especially with respect to key parameters for the nuclide speciation like carbonate concentration and pH, the use of calcium bentonite instead of sodium bentonite will improve the reliability in the prediction of source terms for radionuclide transport in the geosphere. (author)

  6. Mineralogy and geochemistry of bauxite and bentonite deposits from Mozambique

    NARCIS (Netherlands)

    Dos Muchangos, A.C.

    2000-01-01

    Results of mineralogical and geochemical studies of bauxites, kaolinitic clays and bentoniteS from Mozambique are presented in this thesis. The bauxite and kaolinitic clay deposits in Penhalonga area (in the central western part of Mozambique) are associated with Precambrian magmatic rocks and

  7. Filtration behavior of organic substance through a compacted bentonite

    International Nuclear Information System (INIS)

    Kanaji, Mariko; Kuno, Yoshio; Yui, Mikazu

    1999-07-01

    Filtration behavior of organic substance through a compacted bentonite was investigated. Na-type bentonite containing 30wt% of quartz sand was compacted in a column and the dry density was adjusted to be 1.6 g/cm 3 . Polyacrylic acid solution (including three types of polyacrylic acid, average molecular weight 2,100, 15,000 and 450,000) was prepared and was passed through the compacted bentonite. Molecular weight distributions of polyacrylic acid in the effluent solution were analysed by GPC (Gel Permeation Chromatography). A batch type experiment was also carried out in order to examine a sorption behavior of these organic substances onto the surfaces of grains of the bentonite. The results indicated that the smaller size polyacrylic acid (molecular weight < 100,000) was passed through the compacted bentonite. On the other hand, the larger size polyacrylic acid (molecular weight ≥100,000) was mostly filtrated by the compacted bentonite. The batch type sorption tests clarified that the polyacrylic acid did not sorb onto the surfaces of minerals constituting the bentonite. Therefore it was suggested that the larger size molecules (≥100,000) of organic substances could be predominantly filtrated by the microstructure of the compacted bentonite. (author)

  8. A comparative study of the flow enhancing properties of bentonite ...

    African Journals Online (AJOL)

    A comparative study of granule flow enhancing property of bentonite, magnesium stearate, talc and microcrystalline cellulose (MCC) was undertaken. Bentonite was processed into fine powder. A 10 %w/w of starch granules was prepared and separated into different sizes (˂180, 180-500, 500-710 and 710-850 μm).

  9. Diffusion behavior for Se and Zr in sodium-bentonite

    International Nuclear Information System (INIS)

    Sato, Haruo; Yui, Mikazu; Yoshikawa, Hideki

    1995-01-01

    Apparent diffusion coefficients for Se and Zr in bentonite were measured by in-diffusion method at room temperature using water-saturated sodium-bentonite, Kunigel V1 reg-sign containing 50wt% Na-smectite as a major mineral was used as the bentonite material. The experiments were carried out in the dry density range of 400--1,800 kg/m 3 . Bentonite samples were immersed with distilled water and saturated before the experiments. The experiments for Se were carried out under N 2 atmospheric condition (O 2 : 2.5ppm). Those for Zr were carried out under aerobic condition. The apparent diffusion coefficients decrease with increasing density of the bentonite. Since dominant species of Se in the pore water is predicted to be SeO 3 2- , Se may be retarded by anion-exclusion because of negative charge on the surface of the bentonite and little sorption. The dominant species of Zr in the porewater is predicted to be Zr(OH) 5 - or HZrO 3 - . Distribution coefficient measured for Zr on the bentonite was about 1.0 m 3 /kg from batch experiments. Therefore, the retardation may be caused by combination of the sorption and the anion-exclusion. A modeling for the diffusion mechanisms in the bentonite were discussed based on an electric double layer theory. Comparison between the apparent diffusion coefficients predicted by the model and the measured ones shows a good agreement

  10. Reactive Transport and Coupled THM Processes in Engineering Barrier Systems (EBS)

    International Nuclear Information System (INIS)

    Steefel, Carl; Rutqvist, Jonny; Tsang, Chin-Fu; Liu, Hui-Hai; Sonnenthal, Eric; Houseworth, Jim; Birkholzer, Jens

    2010-01-01

    Geological repositories for disposal of high-level nuclear wastes generally rely on a multi-barrier system to isolate radioactive wastes from the biosphere. The multi-barrier system typically consists of a natural barrier system, including repository host rock and its surrounding subsurface environment, and an engineering barrier system (EBS). EBS represents the man-made, engineered materials placed within a repository, including the waste form, waste canisters, buffer materials, backfill and seals (OECD, 2003). EBS plays a significant role in the containment and long-term retardation of radionuclide release. EBS is involved in complex thermal, hydrogeological, mechanical, chemical and biological processes, such as heat release due to radionuclide decay, multiphase flow (including gas release due to canister corrosion), swelling of buffer materials, radionuclide diffusive transport, waste dissolution and chemical reactions. All these processes are related to each other. An in-depth understanding of these coupled processes is critical for the performance assessment (PA) for EBS and the entire repository. Within the EBS group of Used Fuel Disposition (UFD) Campaign, LBNL is currently focused on (1) thermal-hydraulic-mechanical-chemical (THMC) processes in buffer materials (bentonite) and (2) diffusive transport in EBS associated with clay host rock, with a long-term goal to develop a full understanding of (and needed modeling capabilities to simulate) impacts of coupled processes on radionuclide transport in different components of EBS, as well as the interaction between near-field host rock (e.g., clay) and EBS and how they effect radionuclide release. This final report documents the progress that LBNL has made in its focus areas. Specifically, Section 2 summarizes progress on literature review for THMC processes and reactive-diffusive radionuclide transport in bentonite. The literature review provides a picture of the state-of-the-art of the relevant research areas

  11. Reactive Transport and Coupled THM Processes in Engineering Barrier Systems (EBS)

    Energy Technology Data Exchange (ETDEWEB)

    Steefel, Carl; Rutqvist, Jonny; Tsang, Chin-Fu; Liu, Hui-Hai; Sonnenthal, Eric; Houseworth, Jim; Birkholzer, Jens

    2010-08-31

    Geological repositories for disposal of high-level nuclear wastes generally rely on a multi-barrier system to isolate radioactive wastes from the biosphere. The multi-barrier system typically consists of a natural barrier system, including repository host rock and its surrounding subsurface environment, and an engineering barrier system (EBS). EBS represents the man-made, engineered materials placed within a repository, including the waste form, waste canisters, buffer materials, backfill and seals (OECD, 2003). EBS plays a significant role in the containment and long-term retardation of radionuclide release. EBS is involved in complex thermal, hydrogeological, mechanical, chemical and biological processes, such as heat release due to radionuclide decay, multiphase flow (including gas release due to canister corrosion), swelling of buffer materials, radionuclide diffusive transport, waste dissolution and chemical reactions. All these processes are related to each other. An in-depth understanding of these coupled processes is critical for the performance assessment (PA) for EBS and the entire repository. Within the EBS group of Used Fuel Disposition (UFD) Campaign, LBNL is currently focused on (1) thermal-hydraulic-mechanical-chemical (THMC) processes in buffer materials (bentonite) and (2) diffusive transport in EBS associated with clay host rock, with a long-term goal to develop a full understanding of (and needed modeling capabilities to simulate) impacts of coupled processes on radionuclide transport in different components of EBS, as well as the interaction between near-field host rock (e.g., clay) and EBS and how they effect radionuclide release. This final report documents the progress that LBNL has made in its focus areas. Specifically, Section 2 summarizes progress on literature review for THMC processes and reactive-diffusive radionuclide transport in bentonite. The literature review provides a picture of the state-of-the-art of the relevant research areas

  12. Gas migration characteristics of highly compacted bentonite ore

    International Nuclear Information System (INIS)

    Tanaka, Yukihisa; Hironaga, Michihiko

    2010-01-01

    In the current concept of repository for radioactive waste disposal, compacted bentonite will be used as an engineered barrier mainly for inhibiting migration of radioactive nuclides. Hydrogen gas can be generated inside the engineered barrier by anaerobic corrosion of metals used for containers, etc. If the gas generation rate exceeds the diffusion rate of dissolved gas inside of the engineered barrier, gas will accumulate in the void space inside of the engineered barrier until its pressure becomes large enough for it to enter the bentonite as a discrete gaseous phase. It is expected to be not easy for gas to entering into the bentonite as a discrete gaseous phase because the pore of compacted bentonite is so minute. Gas migration characteristics of highly compacted powdered bentonite are already reported by CRIEPI. In this report, gas migration characteristics of bentonite ore, which is a candidate for construction material of repository for radioactive waste, is investigated. The following conclusions are obtained through the results of the gas migration tests which are conducted in this study: 1) When the total gas pressure exceeds the initial total axial stress, the total axial stress is always equal to the total gas pressure because specimens shrink in the axial direction with causing the clearance between the end of the specimen and porous metal. By increasing the gas pressure more, gas breakthrough, which defined as a sudden and sharp increase in gas flow rate out of the specimen, occurs. Therefore gas migration mechanism of compacted bentonite ore is basically identical to that of compacted powdered bentonite. 2) Hydraulic conductivity measured after the gas breakthrough is somewhat smaller than that measured before the gas migration test. This fact means that it might be possible to neglect decline of the function of bentonite as engineered barrier caused by the gas breakthrough. These characteristics of compacted bentonite ore are identical to those of

  13. Enhanced shear strength of sodium bentonite using frictional additives

    International Nuclear Information System (INIS)

    Schmitt, K.E.; Bowders, J.J.; Gilbert, R.B.; Daniel, D.E.

    1997-01-01

    One of the most important obstacles to using geosynthetic clay liners (GCLs) in landfill cover systems is the low shear strength provided by the bentonitic portion of the GCL. In this study, the authors propose that granular, frictional materials might be added to the bentonite to form an admixture that would have greater shear strength than the bentonite alone while still raining low hydraulic conductivity. Bentonite was mixed with two separate granular additives, expanded shale and recycled to form mixtures consisting of 20-70% bentonite by weight. In direct shear tests at normal stresses of 34.5-103.5 kPa, effective friction angles were measured as 45 degrees for the expanded 36 degrees for the recycled glass, and 7 degrees for the hydrated granular bentonite. The strength of the expanded shale mixtures increased nearly linearly as the percentage shale in the mixture increased, to 44 degrees for a bentonite mixture with 80% shale. The addition of recycled glass showed little effect on the shear strength of the mixtures of glass and bentonite. Hydraulic conductivity measurements for both types of mixtures indicated a linear increase with log(k) as the amount of granular additive increased. For applications involving geosynthetic clay liners for cover systems, a mixture of 40% expanded shale and 60% bentonite is recommended, although further testing must be done. The 40/60 mixture satisfies the hydraulic equivalency requirement, with k = 5.1X10 -9 cm/sec, while increasing the shear strength parameters of the bentonitic mixture to φ' = 17 degrees and c' = 0

  14. Influence factors of sand-bentonite mixtures on hydraulic conductivity

    International Nuclear Information System (INIS)

    Chen Yonggui; Ye Weimin; Chen Bao; Wan Min; Wang Qiong

    2008-01-01

    Buffer material is a very important part of the engineering barrier for geological disposal of high-level radioactive nuclear waste. Compacted bentonite is attracting greater attention as buffer and backfill material because it offer impermeability and swelling properties, but the pure compacted bentonite strength decreases with increasing hydration and these will reduce the buffer capability. To solve this problem, sand is often used to form compacted sand-bentonite mixtures (SBMs) providing high thermal conductivity, excellent compaction capacity, long-time stability, and low engineering cost. As to SBMs, hydraulic conductivity is a important index for evaluation barrier capability. Based on the review of research results, the factors affecting the hydraulic conductivity of SBMs were put forward including bentonite content, grain size distribution, moisture content, dry density, compacting method and energy, and bentonite type. The studies show that the hydraulic conductivity of SBMs is controlled by the hydraulic conductivity of the bentonite, it also decreases as dry density and bentonite content increase, but when the bentonite content reach a critical point, the influence of increasing bentonite to decrease the hydraulic conductivity is limited. A fine and well-graded SBMs is likely to have a lower hydraulic conductivity than a coarse and poorly graded material. The internal erosion or erodibility based on the grain size distribution of the SBMs has a negative effect on the final hydraulic conductivity. The lowest hydraulic conductivity is gained when the mixtures are compacted close to optimum moisture content. Also, the mixtures compacted at moisture contents slightly above optimum values give lower hydraulic conductivity than when compacted at slightly under the optimum moisture content. Finally, discussion was brought to importance of compaction method, compacting energy, and bentonite type to the hydraulic conductivity of SBMs. (authors)

  15. Modelling interaction of deep groundwaters with bentonite and radionuclide speciation

    International Nuclear Information System (INIS)

    Wanner, H.

    1986-04-01

    In the safety analysis recently reported for a potential Swiss high-level waste repository, radionuclide speciation and solubility limits are calculated for expected granitic groundwater conditions. This report describes a thermodynamic model which is used to estimate the chemical composition of the pore water in compacted sodium bentonite. The model is based on available experimental data and describes the basic reactions between bentonite and groundwater by an ion-exchange model for sodium, potassium, magnesium, and calcium. The model assumes equilibrium with calcite as long as sufficient carbonates remain in the bentonite, as well as quartz saturation. The long-term situation is modelled by the assumption that the near-field of a deep repository behaves like a mixing tank. It is found that sodium bentonite will slowly be converted to calcium bentonite. The modelled composition of the pore water of compacted sodium bentonite is used to estimate radionuclide solubilities in the near-field of a deep repository. The elements considered are: uranium, neptunium, plutonium, thorium, americium, and technetium. The redox potential in the near-field is assumed to be controlled by the corrosion products of the iron canister. Except for uranium and neptunium, radionuclide solubilities turn out to be lower under the modelled near-field conditions than in the groundwater of the surrounding granitic host rock. Uranium and neptunium solubility might be higher by orders of magnitude in the near-field than in the far-field. From the chemical point of view, calcium bentonite seems to be more stable than sodium bentonite in the presence of Swiss Reference Groundwater. The use of calcium bentonite instead of sodium bentonite will improve the reliability in the prediction of source terms for radionuclide transport in the geosphere. (author)

  16. Antifungal activity of streptomycetes isolated bentonite clay

    Directory of Open Access Journals (Sweden)

    V. P. Shirobokov

    2016-12-01

    Full Text Available Aim. To investigate the biological activity of streptomycetes, isolated from Ukrainian bentonite clay. Methods. For identification of the investigated microorganisms there were used generally accepted methods for study of morpho-cultural and biochemical properties and sequencing of 16Ѕ rRNA producer. Antagonistic activity of the strain was determined by agar diffusion and agar block method using gram-positive, gram-negative microorganisms and fungi. Results. Research of autochthonous flora from bentonite clay of Ukrainian various deposits proved the existence of stable politaxonomic prokaryotic-eukaryotic consortia there. It was particularly interesting that the isolated microorganisms had demonstrated clearly expressed antagonistic properties against fungi. During bacteriological investigation this bacterial culture was identified like representative of the genus Streptomyces. Bentonite streptomycetes, named as Streptomyces SVP-71, inagar mediums (agar block method inhibited the growth of fungi (yeast and mold; zones of growth retardation constituted of 11-36 mm, and did not affect the growth of bacteria. There were investigated the inhibitory effects of supernatant culture fluid, ethanol and butanol extracts of biomass streptomycetes on museum and clinical strains of fungi that are pathogenic for humans (Candida albicans, C. krusei, C. utilis, C. parapsilosis, C. tropicalis, C. kefir, S. glabrata, C. lusitaniae, Aspergillus niger, Mucor pusillus, Fusarium sporotrichioides. It has been shown that research antifungal factor had 100% of inhibitory effect against all fungi used in experiments in vitro. In parallel, it was found that alcohol extracts hadn’t influence to the growth of gram-positive and gram-negative bacteria absolutely. It was shown that the cultural fluid supernatant and alcoholic extracts of biomass had the same antagonistic effect, but with different manifestation. This evidenced about identity of antifungal substances

  17. Effect of pH to adsorption behavior of Pu on bentonite in aqueous environment

    International Nuclear Information System (INIS)

    Wang Xiaoqiang; Tuo Xianguo; Li Pingchuan; Leng Yangchun; Su Jilong; Yueping

    2013-01-01

    The effects of pH to the adsorption behavior of Pu in GMZ-bentonite, Lingshou Ca-bentonite, Na-bentonite and bleaching earth were tested by static adsorption experiments in aqueous environment. The results show that the adsorption equilibrium time of Pu is four days in GMZ-bentonite and 5-6 days in bleaching earth, Ca-bentonite and Na-bentonite. In aqueous environment, the adsorption capacity of bentonite to Pu increases with pH in water phase, and it is weak in acidic aqueous environment and strong in alkaline aqueous environment extremely. (authors)

  18. A numerical study of thermal conditions in the THM growth of HgTe

    Science.gov (United States)

    Martínez-Tomás, M. C.; Muñoz-Sanjosé, V.; Reig, C.

    2002-09-01

    A numerical simulation of the travelling heater method (THM) process in the growth of HgTe is carried out. The whole system (furnace, ampoule and charge) is taken into account in the frame of a quasi-steady-state model. The mass conservation condition for the solute in the liquid zone permits the determination of the rate of advance of the crystallisation isotherm as a function of the heater position. We claim to study the evolution of different magnitudes along the growth process, searching for the physical reasons which could be at the origin of defects in the form of thin layers observed in some growing experiences. To solve the governing equations of fluid flow, heat transfer and mass transport we have made use of a commercial code which can run in a PC. The simulation is made by using a three-level strategy, which allows the reduction of the computational effort. In the first level, heat transport is assumed to be by conduction, convection and radiation between the furnace and the ampoule, and by conduction through the ampoule wall, coating, solid and liquid zones. The temperature calculated at this level in the air/ampoule boundary is used as boundary condition for the second and third level. In these two levels the ampoule and its content are studied in detail. Convection in the liquid zone is considered at the second level and thermosolutal convection is finally included at the third level. The analysis of the incoming/outcoming heat flux per second through the ampoule for the whole system shows that the lower part of the ampoule exhibits some ineffectiveness for the heat evacuation at certain positions of the growth run, depending on thermal properties of the whole system and the particular material to be grown. As a consequence, the growth rate suffers a significant variation just for these positions of the heater. From these considerations a plausible interpretation has been proposed to understand the apparition of solvent inclusions in the form of thin

  19. T-H-M couplings in rock. Overview of results of importance to the SR-Can safety assessment

    International Nuclear Information System (INIS)

    Hoekmark, Harald; Faelth, Billy; Wallroth, Thomas

    2006-09-01

    This report deals with THM processes in rock hosting a KBS-nuclear waste repository. The issues addressed are mechanically and thermo-mechanically induced changes of the hydraulic conditions in the near-field and in the far-field, and the risk of stress-induced failure, spalling, in the walls of deposition holes. These changes are examined for the construction and operational phases, the initial temperate period and a subsequent glacial cycle. The report was compiled to be used as reference and background for corresponding parts of the safety report SR-Can. The near-field is analyzed using thermo-mechanical DEC models. There are a number of models for each of the three sites Forsmark, Simpevarp and Laxemar. Parameter values of intact rock and rock mass mechanical and thermo-mechanical properties were obtained from the site descriptive models. Layout data, i.e. the number of canisters, the geometry of the repository openings, the tunnel spacing and the canister spacing are in accordance with rules and guidelines given in general design- and layout documents. Heat generation data, i.e. the initial canister power and the canister power decay are in accordance with data given in the SR-Can main report. The effects of changes in nearfield stresses during the different phases of the repository's lifetime are evaluated by comparing numerically obtained stresses and deformations on a number of explicitly modelled near-field fractures with empirical and theoretical stress-transmissivity laws and with empirically based slip-transmissivity estimates. For the near-field it is concluded that substantial transmissivity increases are found only very close to the repository openings. Bounding estimates, judged to be valid for the entire load sequence, are made of the extent and magnitude of the hydraulic disturbance. At distances larger than about 1.5 m from the tunnel periphery, transmissivity increases are concluded to be too small and unsystematic to be of any concern. The

  20. T-H-M couplings in rock. Overview of results of importance to the SR-Can safety assessment

    Energy Technology Data Exchange (ETDEWEB)

    Hoekmark, Harald; Faelth, Billy [Clay Technology AB, Lund (Sweden); Wallroth, Thomas [BERGAB, Goeteborg (Sweden)

    2006-09-15

    This report deals with THM processes in rock hosting a KBS-nuclear waste repository. The issues addressed are mechanically and thermo-mechanically induced changes of the hydraulic conditions in the near-field and in the far-field, and the risk of stress-induced failure, spalling, in the walls of deposition holes. These changes are examined for the construction and operational phases, the initial temperate period and a subsequent glacial cycle. The report was compiled to be used as reference and background for corresponding parts of the safety report SR-Can. The near-field is analyzed using thermo-mechanical DEC models. There are a number of models for each of the three sites Forsmark, Simpevarp and Laxemar. Parameter values of intact rock and rock mass mechanical and thermo-mechanical properties were obtained from the site descriptive models. Layout data, i.e. the number of canisters, the geometry of the repository openings, the tunnel spacing and the canister spacing are in accordance with rules and guidelines given in general design- and layout documents. Heat generation data, i.e. the initial canister power and the canister power decay are in accordance with data given in the SR-Can main report. The effects of changes in nearfield stresses during the different phases of the repository's lifetime are evaluated by comparing numerically obtained stresses and deformations on a number of explicitly modelled near-field fractures with empirical and theoretical stress-transmissivity laws and with empirically based slip-transmissivity estimates. For the near-field it is concluded that substantial transmissivity increases are found only very close to the repository openings. Bounding estimates, judged to be valid for the entire load sequence, are made of the extent and magnitude of the hydraulic disturbance. At distances larger than about 1.5 m from the tunnel periphery, transmissivity increases are concluded to be too small and unsystematic to be of any concern. The

  1. Results from an International Simulation Study on Couples Thermal, Hydrological, and Mechanical (THM) Processes Near Geological Nuclear Waste Repositories

    International Nuclear Information System (INIS)

    J. Rutqvist; J.T. Birkholzer; M. Chijimatsu; O. Kolditz; Q.S. Liu; Y. Oda; W. Wang; C.Y. Zhang

    2006-01-01

    As part of the ongoing international code comparison project DECOVALEX, four research teams used five different models to simulate coupled thermal, hydrological, and mechanical (THM) processes near underground waste emplacement drifts. The simulations were conducted for two generic repository types with open or back-filled repository drifts under higher and lower post-closure temperature, respectively. In the completed first model inception phase of the project, a good agreement was achieved between the research teams in calculating THM responses for both repository types, although some disagreement in hydrological responses are currently being resolved. Good agreement in the basic thermal-mechanical responses was achieved for both repository types, even with some teams using relatively simplified thermal-elastic heat-conduction models that neglect complex near-field thermal-hydrological processes. The good agreement between the complex and simplified (and well-known) process models indicates that the basic thermal-mechanical responses can be predicted with a relatively high confidence level. The research teams have now moved on to the second phase of the project, the analysis of THM-induced permanent (irreversible) changes and the impact of those changes on the fluid flow field near an emplacement drift

  2. Engineering Properties of Bentonite Stabilized with Lime and Phosphogypsum

    Directory of Open Access Journals (Sweden)

    Kumar Sujeet

    2014-12-01

    Full Text Available Engineering properties such as compaction, unconfined compressive strength, consistency limits, percentage swell, free swell index, the California bearing ratio and the consolidation of bentonite stabilized with lime and phosphogypsum are presented in this paper. The content of the lime and phosphogypsum varied from 0 to 10 %. The results reveal that the dry unit weight and optimum moisture content of bentonite + 8 % lime increased with the addition of 8 % phosphogypsum. The percentage of swell increased and the free swell index decreased with the addition of 8 % phosphogypsum to the bentonite + 8 % lime mix. The unconfined compressive strength of the bentonite + 8 % lime increased with the addition of 8 % phosphogypsum as well as an increase in the curing period up to 14 days. The liquid limit and plastic limit of the bentonite + 8 % lime increased, whereas the plasticity index remained constant with the addition of 8 % phosphogypsum. The California bearing ratio, modulus of subgrade reaction, and secant modulus increased for the bentonite stabilized with lime and phosphogypsum. The coefficient of the consolidation of the bentonite increased with the addition of 8 % lime and no change with the addition of 8 % phosphogypsum.

  3. Colloid chemical aspects of the ''confined bentonite concept''

    International Nuclear Information System (INIS)

    Bell, J.C. Le

    1978-03-01

    Measurements of the amount of particles released from a bentonite gel by light scattering and visual inspection show that while particles are released in distilled water, the gel will be coagulated if in contact with ground water and consequently the release of particles is negligibly small. Studies of sedimentation volumes by ultracentrifugation also clearly indicate that the bentonite in contact with ground water under the repository pressure will form a completely stable coagulated gel. The swelling of confined bentonite was studied in an ''artificial crack'' of width 0.5 mm. The bentonite flowed readily into this crack and into the much narrower crack formed when the cell was broken. The swelling properties of the bentonite at the repository depth are discussed. It is argued that the gel, if sufficient volume is available, will swell spontaneously to a volume that is approximately 30 % larger than the initial one and then form a stable, coagulated gel containing 30-35 % water in equilibrium with the ground water. Investigations of the diffusion of colloidal matter (sodium lignosulphonate molecules of mean diameter 6 nm) and calcium ions into a dilute bentonite gel show that colloidal matter very probably will have a negligible rate of diffusion while the calcium ions diffuse rapidly. This implies that the initial bentonite gel which is partially in its sodium form will be completely exchanged to its calcium form when brought into contact with ground water which ensures that it will remain coagulated even in its swollen state

  4. Characterization of bentonite clay from Cubati, PB, Brazil

    International Nuclear Information System (INIS)

    Batista, A.P.; Marques, L.N.; Campos, L.A.; Neves, G.A.; Ferreira, H.C.; Menezes, R.R.

    2009-01-01

    The bentonite of the State of Paraiba are commercially used in numerous technological sectors, particularly in oil drilling muds. However, these bentonite deposits are becoming exhausted after decades of exploitation. Thus, the aim of this work was to characterize physically, mineralogically and technologically bentonite clays from Cubati city, PB. The samples were dried at 60 deg C and characterized through X-ray fluorescence, particle size distribution, X-ray diffraction, differential thermal and gravimetric analyzes and scanning electronic microscopy. The natural bentonite clays were transformed into sodium bentonite by Na_2CO_3 solution treatment. It was estimated the rheological properties of the suspensions: apparent and plastic viscosities and water loss. The results showed that the samples are polycationic bentonite clays, containing amounts of MgO, CaO and K_2O similar to those of bentonite from Boa Vista, PB, and are composed of smectite, kaolinite and quartz. The samples presented fractions of particles size under 2 μm of 30 and 32%. The rheological properties showed that the samples presented technological potential to be used in drilling muds. (author)

  5. Laboratory studies on the effect of ozonation on THM formation in swimming pool water

    DEFF Research Database (Denmark)

    Hansen, Kamilla Marie Speht; Spiliotopoulou, Aikaterini; Cheema, Waqas Akram

    2015-01-01

    Water samples from indoor swimming pool were ozonated at different pH values to evaluate the effect of pH on decomposition of ozone in swimming pool water. Furthermore, drinking and pool water were repeatedly ozonated followed by chlorination to evaluate THM formation. Decomposition of ozone...... was not affected by pH in the range relevant to swimming pools (pH 6.8 – 7.8) and a half-life time at 10-12 min was obtained. Repeating the ozonation, the decomposition of ozone increased at the second dose of ozone added (t½,2=8 min) and then decreased again at the third and fourth dose of ozone (t½,3=17 min; t...... chlorine for drinking water as lower TTHM formation occurred than in non-ozonated samples. For pool water, a higher TTHM formation was observed in ozonated than non-ozonated pool water. Thus, it was observed that ozone reacts markedly different in swimming pool water from the known pattern in drinking...

  6. Modelling interaction of deep groundwaters with bentonite and radionuclide speciation

    International Nuclear Information System (INIS)

    Wanner, H.

    1986-04-01

    In the safety analysis recently reported for a potential Swiss high-level waste repository, radionuclide speciation and solubility limits are calculated for expected granitic groundwater conditions. With the objective of deriving a more realistic description of radionuclide release from the near-field, an investigation has been initiated to quantitatively specify the chemistry of the near-field. In the Swiss case, the main components of the near-field are the glass waste-matrix, a thick steel canister horizontally emplaced in a drift, and a backfill of highly compacted sodium bentonite. This report describes a thermodynamic model which is used to estimate the chemical composition of the pore water in compacted sodium bentonite. Solubility limits and speciation of important actinides and the fission product technetium in the bentonite pore water are then calculated. The model is based on available experimental data on the interaction of sodium bentonite and groundwater and represents means of extrapolation from laboratory data to repository conditions. The basic reactions between sodium bentonite and groundwater are described by an ion-exchange model for sodium, potassium, magnesium, and calcium. The model assumes equilibrium with calcite as long as sufficient carbonates remain in the bentonite, as well as quartz saturation. It is calculated that the pore water of compacted sodium bentonite saturated with Swiss Reference Groundwater will have a pH value of 9.7 and a free carbonate activity of 8x10 -4 M. The long-term situation is modelled by the assumption that the near-field of a deep repository behaves like a mixing tank. In this way, an attempt is made to account for the continuous water exchange between the near-field and the host rock. It is found that sodium bentonite will be slowly converted to calcium bentonite. This conversion is roughly estimated to be completed after 2 million years

  7. Bentonite chemical modification for use in industrial effluents

    International Nuclear Information System (INIS)

    Laranjeira, E.; Pinto, M.R.O.; Rodrigues, D.P.; Costa, B.P.; Guimaraes, P.L.F.

    2010-01-01

    The present work aims at synthesizing organoclays using a layered silicate of regional importance, bentonite clay, for the treatment of industrial effluents. The choice of clay to be organophilized was based on cation exchange capacity (CEC). Bentonite with higher CTC was called AN 35 (92 meq/100 g), and therefore was the one that suffered the chemical modification with salt cetyl trimethyl ammonium Cetremide, provided by Vetec.The unmodified and modified clays were characterized by FTIR and XDR. The data obtained through the characterizations confirmed the acquisition of bentonite organoclay thus suggesting its subsequent application in the treatment of industrial effluents. (author)

  8. Water uptake and stress development in bentonites and bentonite-sand buffer materials

    International Nuclear Information System (INIS)

    Dixon, D.A.; Wan, A.W-L.; Gray, M.N.; Miller, S.H.

    1996-10-01

    The development of swelling pressure and the transfer of pore water pressures through dense bentonite and bentonite-sand materials are examined in this report. This report focuses on the swelling pressure and total pressure developed in initially unsaturated specimens allowed access to free water on one end. The bentonite in this wetted region rapidly develops its full swelling pressure and this pressure is transferred upwards through the specimen. Hence, the bentonite plug will exert a pressure approximately equivalent to the swelling pressure even though only a small region of the plug is actually saturated. A number of specimens were tested with total pressure sensors mounted normal and parallel to the axis of compaction. Lateral pressures developed long before the wetting front reached sensor locations, suggesting stress transfer through the unsaturated portions of these specimens. On achieving saturation, specimens were found to have similar swelling pressures both normal to and parallel to the axis of compaction. This indicates that there is little or no specimen anisotropy induced by the compaction process. Tests were conducted on specimens allowed only to take on a limited quantity of water and it was found that density anisotropy was induced as the result of the swelling pressures generated by the buffer. The wetted skin of buffer developed a considerable pressure and compressed a region of buffer immediately above the wetted region. The results suggest that the buffer material placed in a disposal vault will rapidly develop and transfer swelling pressures as a result of the saturation of a limited region or 'skin' within the emplacement site. The total pressure ultimately present on the container surface should be the sum of the swelling and hydraulic components. (author). 14 refs., 4 tabs., 8 figs

  9. Comparison between uniaxially and isostatically compacted bentonite

    International Nuclear Information System (INIS)

    Kalbantner, P.; Sjoeblom, R.; Boergesson, Lennart

    2001-12-01

    The purpose of the present report is to provide the Swedish Nuclear Fuel and Waste Management Company (SKB) with the knowledge base needed for their selection of reference method for manufacturing of bentonite blocks. The purpose is also to provide support for the direction of the further development work. Three types of blocks are compared in the present report: uniaxially compacted medium high blocks, isostatically compacted medium high blocks, isostatically compacted high blocks. The analyses is based on three process systems relating to the sequence of excavation of bentonite-transport-powder preparation-compaction-handling and emplacement of bentonite blocks. The need for further knowledge has been identified and documented in conjunction with these analyses. The comparison is primarily made with regard to the criteria safety/risk, quality/ technique and economy. It is carried out through identification of issues of significance and subsequent analysis and evaluation as well as more formally in a simplified AHP (AHP = Analytical Hierarchic Process). The result of the analyses is that the isostatic technique is applicable for the production of high as well as medium size blocks. The pressed blocks are assessed to fulfil the basic requirements with a very large margin. The result of the analyses is also that the uniaxial technique is applicable for the preparation of medium size blocks, which are assessed to fulfil the basic requirements with a large margin. The need for development and process control is assessed to be somewhat higher for the uniaxial technique. One example is the friction against the walls of the die during the compaction, including the significance of this friction for the development of stresses and discontinuities in the block. These results support a selection of the isostatic technique as the reference technique as it provides flexibility in the choice of block height. The uniaxial technique can form a second alternative if medium high

  10. Polypropylene–clay composite prepared from Indian bentonite

    Indian Academy of Sciences (India)

    WINTEC

    composites have recently found applications in packaging, automotive ... process using xylene as the solvent. Solvent ... Particle size distribution curve for clay, bentonite. Table 2. .... greater probability of debonding due to the poor interfa-.

  11. Small-scale bentonite injection test on rock

    International Nuclear Information System (INIS)

    Pusch, R.

    1978-03-01

    When radiactive waste is disposed a sealing of the rock is very valuable since it reduces the rate of water percolation and diffusion. In an earlier report injection of bentonite gels by means of over-pressure and subsequent electrophoresis has been suggested. The present report describes a rock test series where bentonite injection was applied. For the test an approximately cubical block of about 1 m 3 was selected. The rock type was diorite with a fairly high frequency of quartz denses. The block was kept in a basin during the test in order to maintain the water saturation. Holes were bored in the block. A bentonite slurry with 1000 percent water content was injected. It was shown that the bentonite had a sealing effect but the depth of extrusion into rock joints was not large because of gelation. Electro-Kinetic injection of montmorillonite was found to be a more promising technique for rock lightening

  12. Effects of polyethyleneimine adsorption on rheology of bentonite ...

    Indian Academy of Sciences (India)

    Unknown

    XRD, zeta potential and adsorption studies were done together with rheological .... trokinetics experiments on Balikesir bentonite samples. For this reason, the ... rence between apparent and true adsorption rates, and hence swelling of clays ...

  13. Immobilization of industrial waste in cement–bentonite clay matrix

    Indian Academy of Sciences (India)

    Unknown

    Immobilization of industrial waste in cement–bentonite clay matrix. I B PLECAS* and S ... high structural integrity and minimizing the risk of escape by leaching. ..... Radioactive Waste Management and Nuclear Fuel Cycle 14. 195. Plecas I ...

  14. Diffusion of Fission Product Elements in Compacted Bentonite

    International Nuclear Information System (INIS)

    Pratomo-Budiman-Sastrowardoyo; Dewi-Susilowati; Dadang-Suganda

    2000-01-01

    Study on diffusion of fission product in compacted bentonite has been conducted. The information about mobilities of these elements have been obtained from the studies resulted in many countries. It is presented that the diffusion coefficient was varied by the function of solution phase condition as well as the nature of bentonite. It is also showed that the diffusion coefficient decreased by the increasing of density, as well as the increasing of montmorillonite content in bentonite. The ratio of bentonite/silica-sand used, was related to the increasing of elements mobility. In many case variation of diffusion coefficient was related to the variation of pH, redox condition, and the presence of complex ant in solution phase. The lower diffusion coefficient could give the higher retardation factor, which is a favorable factor to retard the radionuclides release from a disposal facility to geosphere. (author)

  15. Long term mineralogical properties of bentonite/quartz buffer substance

    International Nuclear Information System (INIS)

    Jacobsson, A.; Pusch, R.

    1978-06-01

    This report shows results from investigations concerning properties in bentonitebased buffersubstances which are suggested to be used when high level radioactive wastes from nuclear powerplants are to be stored finally. Recommended material characteristica of the bentonite to be used are summerized. In an attempt to find geological evidence for bentonite to loose its desireable properties there were no such findings at the temperatures, groundwater situations and pressures which are to be expected at the actual depositing depth (500 m) for a considerable period of time. Concerning biological activity and then specially the mobility and activity of bacteria the conclusion is that there will be little or no influence from them either there is bentonite-sand or compacted pure bentonite in the buffer mass

  16. bentonite-sand mixture as new backfill/buffer material

    International Nuclear Information System (INIS)

    Cui Suli; Liu Jisheng; Zhang Huyuan; Liang Jian

    2008-01-01

    The mixture of bentonite and quartz sand is suggested as a new backfill/buffer material for geological disposal of HLW. To improve the further design of underground laboratory and in-situ industrial construction test, the optimization of sand addition to bentonite is focused at present research stage. Based on summarizing the research results abroad, laboratory tests were conducted on the mixture of GMZ001 bentonite and quartz sand, such as compaction test and swelling tests etc. Test data shows that GMZ bentonite-sand mixture exhibits a favorite compaction with a 30% sand addition, a highest swelling pressure with a 20% sand addition, and a decreasing plasticity with increases in sand addition and pore liquid concentration. (authors)

  17. Simulation of Tracer Transport in Porous Media: Application to Bentonites

    International Nuclear Information System (INIS)

    Bru, A.; Casero, D.

    2001-01-01

    We present a formal framework to describe tracer transport in heterogeneous media, such as porous media like bentonites. In these media, mean field approximation is not valid because there exist some geometrical constraints and the transport is anomalous. (Author)

  18. Migration study of actinides and lanthanides in compacted bentonite

    International Nuclear Information System (INIS)

    Sastrowardoyo, P.B.; Susilowati, D.; Suganda, D.

    1998-01-01

    Migration study of actinide and lanthanide elements in compacted bentonite has been conducted. Data of these elements mobilities have been shown, and it is showed that the diffusion coefficient was varied as the function of solution phase condition as well as the origin/composition of bentonite. It is showed that the diffusion coefficient decreased by the increasing of density, as well as the increasing of montmorillonite content in bentonite. The ratio of bentonite/silica-sand used was related to the increasing of elements mobility. In many case the difference of diffusion coefficient was related to the variation of pH and redox condition, as well as the presence of complexant in solution phase. The Lower diffusion coefficient could give the higher retardation factor, which is a favourable factor to retard the radionuclides release from a disposal facility to geosphere. (author)

  19. Evaluation of brazilian bentonites as additive in the radwaste cementation

    International Nuclear Information System (INIS)

    Tello, C.C.O. de.

    1988-01-01

    The behavior of some Brazilian bentonites has been evaluated, concerning to their use as additive in the radwaste cementation. The purpose of the bentonite is to retain the radioelements in the final product in leaching process. Experiments to determine properties such as compressive strenght, viscosity, set time leaching and cesium sorption have been carried out to this evaluation. After one-year test, the results show that the bentonites greatly reduce the cesium release. A literature survey about cementation process and plants and about the cement product characteristics has been made in order to obtain a reliable final product, able to be transported and storaged. Some leaching test methods and mathematical models, that could be applied in the evaluation of cement products with bentonite have been evaluated. (author) [pt

  20. Comparative Analysis on Chemical Composition of Bentonite Clays ...

    African Journals Online (AJOL)

    2017-09-12

    Sep 12, 2017 ... Comparative Analysis on Chemical Composition of Bentonite Clays. Obtained from Ashaka and ... versatile material for geotechnical engineering and as well as their demand for ..... A PhD thesis submitted to the Chemical ...

  1. Physico-chemical properties of water in bentonite

    International Nuclear Information System (INIS)

    Torikai, Yuji; Sato, Seichi; Ohashi, Hiroshi

    1994-01-01

    As a part of safety analysis on ground layer disposal, in order to estimate nuclides migration behavior from engineering shielding materials, it is required to modelize migration process of nuclides in bentonite and chemical species relating to corrosion, to estimate solubility and to specify application condition of geochemical calculation code. In this study, as a part of elucidation of nuclide migration process, physico-chemical properties of water in bentonite and montmorillonite using steam pressure method were determined. As a result, following items were found: (1) Even if 1/3 of water in bentonite is near free water, it is far from a region dealable with dilute solution in the electrolyte solution theory. And, (2) the water in bentonite has generally small activity in comparison with dilute solution, then has smaller solubility than estimation value of calculation code. (G.K.)

  2. Buffer construction technique using granular bentonite

    International Nuclear Information System (INIS)

    Masuda, Ryoichi; Asano, Hidekazu; Toguri, Satohito; Mori, Takuo; Shimura, Tomoyuki; Matsuda, Takeshi; Uyama, Masao; Noda, Masaru

    2007-01-01

    Buffer construction using bentonite pellets as filling material is a promising technology for enhancing the ease of repository operation. In this study, a test of such technology was conducted in a full-scale simulated disposal drift, using a filling system which utilizes a screw conveyor system. The simulated drift, which contained two dummy overpacks, was configured as a half-cross-section model with a height of 2.22 m and a length of 6.0 m. The average dry density of the buffer obtained in the test was 1.29 Mg/m 3 , with an angle of repose of 35 to 40 degrees. These test results indicate that buffer construction using a screw conveyor system for pellet emplacement in a waste disposal drift is a promising technology for repositories for high level radioactive wastes. (author)

  3. Thermally modified bentonite clay for copper removal

    International Nuclear Information System (INIS)

    Bertagnolli, C.; Kleinübing, S.J.; Silva, M.G.C.

    2011-01-01

    Bentonite clay coming from Pernambuco was thermally modified in order to increase its affinity and capacity in the copper removal in porous bed. The application of this procedure is justified by the low cost of clay, their abundance and affinity for various metal ions. Thermally treatment modifies the clay adsorption properties enables its use in porous bed system, with the increase in surface area and mechanical strength. The material was characterized by x-ray diffraction, thermogravimetric analysis and N_2 physisorption. Then tests were carried out for adsorption of copper in various experimental conditions and evaluated the mass transfer zone, useful and total adsorbed removal amounts and total copper removal percentage. The results showed that the clay treated at higher temperature showed higher copper removal. (author)

  4. Experimental Setup to Characterize Bentonite Hydration Processes

    International Nuclear Information System (INIS)

    Bru, A.; Casero, D.; Pastor, J. M.

    2001-01-01

    We present an experimental setup to follow-up the hydration process of a bentonite. Clay samples, of 2 cm x 12 cm x 12 cm, were made and introduced in a Hele-Shaw cell with two PMM windows and two steel frames. In hydration experiments, a fluid enters by an orifice in the frame, located both at the top and the bottom of the cell, to perform hydration in both senses. To get a uniform hydration we place a diffuser near the orifice. Volume influxes in hydration cells are registered in time. The evolution of the developed interface was recorded on a videotape. The video cameras was fixed to a holder so that the vertical direction in the monitor was the same as the direction of the larger extension of the cell. (Author) 6 refs

  5. Adsorption behavior of 99Tc in Ca-bentonite

    International Nuclear Information System (INIS)

    Liu Dejun; Fan Xianhua; Zhang Yingjie; Yao Jun; Zhou Duo; Wang Yong

    2004-01-01

    The adsorption behaviors of 99 Tc in bentonite were studied with batch methods under aerobic and anoxic conditions. The adsorption ratios is about 1.47 mL/g under aerobic conditions. The adsorption ratio of 99 Tc in bentonite is not affected by pH in the range of 5-12 and the CO 3 2- , Fe 3+ concentrations in the range of 10 -8 -10 -2 mol/L in the solution. The adsorption ratio of Tc in bentonite increases with the increase of the mass percent of Fe 2 O 3 and Fe 3 O 4 and the Fe 2+ concentration in the range of 10 -8 -10 -2 mol/L. Tc exists ainly in the form of Tc(VII) after the adsorption equilibriums. The adsorption ratio of Tc in bentonite increase with the increase of the mass percent of Fe and Tc exists mainly in the form of Tc(VII) after the adsorption equilibriums. The adsorption ratio of Tc in bentonite is about 84.84 mL/g under anoxic conditions. The adsorption ratios of 99 Tc in bentonite decreases with the increase of pH in the range of 5-12 and the CO 3 2- concentration in the range of 10 -8 -10 -2 mol/L in the solution. The adsorption ratio of Tc in bentonite increases with the increase of the Fe 3+ , Fe 2+ concentration in the range of 10 -8 -10 -2 mol/L and the mass percent of Fe, Fe 2 O 3 and Fe 3 O 4 . Tc exists mainly in the form of Tc(IV) after the adsorption equilibriums. The adsorption isotherms of TcO 4 - in bentonite are all in fairly agree with the Freundlich's equation under aerobic and anoxic conditions. (authors)

  6. Bentonite as a backfill material for shallow land repositories

    International Nuclear Information System (INIS)

    Yalmali, V.S.; Deshingkar, D.S.

    2001-01-01

    Two commercially available indigenous bentonite samples were evaluated for their cesium and strontium sorption properties in distilled water and surface water. By converting them into sodium form, the distribution coefficients for both cesium (I) and strontium (II) increased. Sodium bentonite was recommended because of high sorption capacity for Cs(I), Mg(II) and Sr(II) for use as backfill material in shallow land repositories where cement waste form containing Cs, Sr and Be wastes are disposed. (author)

  7. Saturation of bentonite dependent upon temperature

    International Nuclear Information System (INIS)

    Hausmannova, Lucie; Vasicek, Radek

    2010-01-01

    Document available in extended abstract form only. The fundamental idea behind the long-term safe operation of a deep repository is the use of the Multi-barrier system principle. Barriers may well differ according to the type of host rock in which the repository is located. It is assumed that the buffer in the granitic host rock environment will consist of swelling clays which boast the ideal properties for such a function i.e. low permeability, high swelling pressure, self-healing ability etc. all of which are affected primarily by mineralogy and dry density. Water content plays a crucial role in the activation of swelling pressure as well as, subsequently, in the potential self healing of the various contact areas of the numerous buffer components made from bentonite. In the case of a deep repository, a change in water content is not only connected with the possible intake of water from the host rock, but also with its redistribution owing to changes in temperature after the insertion of the heat source (disposal waste package containing spent fuel) into the repository 'nest'. The principal reason for the experimental testing of this high dry density material is the uncertainty with regard to its saturation ability (final water content or the degree of saturation) at higher temperatures. The results of the Mock-Up-CZ experiment showed that when the barrier is constantly supplied with a saturation medium over a long time period the water content in the barrier as well as the degree of saturation settle independently of temperature. The Mock-Up-CZ experiment was performed at temperatures of 30 deg. - 90 deg. C in the barrier; therefore it was decided to experimentally verify this behaviour by means of targeted laboratory tests. A temperature of 110 deg. C was added to the set of experimental temperatures resulting in samples being tested at 25 deg. C, 95 deg. C and 110 deg. C. The degree of saturation is defined as the ratio of pore water volume to pore

  8. Sorption of strontium on bentonites from Slovak deposits

    International Nuclear Information System (INIS)

    Kufcakova, J.; Galambos, M.; Rajc, P.

    2005-01-01

    Sorption on bentonite from different Slovak deposits / Jelsovy potok, Kopernica and Lieskove has been investigated under various experimental conditions, such as contact time, pH, sorbate concentrations, presence of complementary cation. The sorption of strontium from aqueous solutions was investigated using a radiometric determination of distribution coefficient, Kd. The individual solutions were labelled with radiotracer. Radiation stability has been investigated, the higher sorption parameters were observed for the irradiated bentonites /tab.l/ , which can be explained by the increase of specific surface and change of solubility of the irradiated samples of bentonite. The presence of complementary cations, Na + , K + , NH 4 + , Ca 2+ , Mg 2+ and Ba 2+ depresses the sorption of Sr on bentonite. In the case of bentonite Kopernica the effectiveness in reducing the sorption of strontium by cations followed the order K + 4 + + 2+ 2+ 2+ . Results indicate that the sorption of Sr + on bentonite will be affected by the presence of high concentrations of various salts in the waste water effluents. (author)

  9. Geochemical investigation of iron transport into bentonite as steel corrodes

    International Nuclear Information System (INIS)

    Hunter, Fiona; Bate, Fiona; Heath, Tim; Hoch, Andrew

    2007-09-01

    In Sweden and Finland, it is proposed that spent nuclear fuel will be encapsulated in sealed cylindrical canisters, for disposal in a geologic repository, either in vertical boreholes (KBS-3V) or in long horizontal boreholes (KBS-3H). The canisters will consist of a thick cast iron insert and a copper outer container, and each canister will be surrounded by a compacted bentonite clay buffer. It is important to investigate the possible consequences if a failure of these physical barriers was to occur. For instance, if mechanical failure of the copper outer container were to occur then groundwater could enter the annulus and reach the cast iron insert. This would result in anaerobically corroded iron from the cast iron insert interacting with the bentonite surrounding the canisters. The presence of anaerobically corroded iron in groundwater raises the question of how the bentonite will be affected by this process. In the case of the KBS-3H concept, mechanical failure of the copper outer container could lead to interaction between anaerobically corroded iron and bentonite, as above. However, direct contact between anaerobically corroding carbon steel and bentonite is also likely because of the presence of perforated carbon steel support structures in the long horizontal boreholes. As part of the NF-PRO project, an extensive experimental programme has been carried out over several years to study the interactions between anaerobically corroding carbon steel or cast iron and bentonite. The purpose of this report is to describe the modelling work that has been carried out, and the conclusions that have been reached. The experimental programme has carried out a series of long term experiments looking at anaerobic corrosion of carbon steel or cast iron in compacted MX80 bentonite at 30 deg C or 50 deg C. In the bentonite the concentration of iron decreased with increasing distance away from the iron-bentonite interface, with local iron concentrations as high as 20 wt % in

  10. Behaviour of bentonite accessory minerals during the thermal stage

    International Nuclear Information System (INIS)

    Arcos, David; Bruno, Jordi; Benbow, Steven; Takase, Hiro

    2000-03-01

    This report discusses in a quantitative manner the evolution of the accessory minerals in the bentonite as a result of the thermal event exerted by the spent fuel in the near field. Three different modelling approaches have been used and the results compared between them. The three different approaches have been calculated using two Differential Algebraic Equation (DAE) solver: DYLAN (Model-1) and the Nag DAE solver, d02ngf (Model-2) and the third approach (Model-3) using the last version of PHREEQC. The results from these calculations indicate the feasibility of the modelling approach to model the migration of bentonite accessory minerals and relevant aqueous species throughout the thermal gradient. These calculations indicate that the migration of quartz and quartz polymorphs is a lesser problem. The aqueous speciation of Ca in the bentonite pore water is fundamental in order to define the potential migration of anhydrite during the thermal stage. If CaSO 4 (aq) is the predominant aqueous species, then anhydrite dissolves at the initial groundwater migration times through bentonite. However, if Ca 2+ is considered to be the dominant Ca species at the bentonite pore water, then anhydrite migrates towards the clay/granite interface. This is the main difference in the chemical systems considered in the three model approaches used in this work. The main process affecting the trace mineral behaviour in bentonite is cation exchange. This process controls the concentration of calcium, which results in a direct control of the calcite precipitation-dissolution

  11. Geochemical investigation of iron transport into bentonite as steel corrodes

    Energy Technology Data Exchange (ETDEWEB)

    Hunter, Fiona; Bate, Fiona; Heath, Tim; Hoch, Andrew [Serco Assurance, Harwe ll (United Kingdom)

    2007-09-15

    In Sweden and Finland, it is proposed that spent nuclear fuel will be encapsulated in sealed cylindrical canisters, for disposal in a geologic repository, either in vertical boreholes (KBS-3V) or in long horizontal boreholes (KBS-3H). The canisters will consist of a thick cast iron insert and a copper outer container, and each canister will be surrounded by a compacted bentonite clay buffer. It is important to investigate the possible consequences if a failure of these physical barriers was to occur. For instance, if mechanical failure of the copper outer container were to occur then groundwater could enter the annulus and reach the cast iron insert. This would result in anaerobically corroded iron from the cast iron insert interacting with the bentonite surrounding the canisters. The presence of anaerobically corroded iron in groundwater raises the question of how the bentonite will be affected by this process. In the case of the KBS-3H concept, mechanical failure of the copper outer container could lead to interaction between anaerobically corroded iron and bentonite, as above. However, direct contact between anaerobically corroding carbon steel and bentonite is also likely because of the presence of perforated carbon steel support structures in the long horizontal boreholes. As part of the NF-PRO project, an extensive experimental programme has been carried out over several years to study the interactions between anaerobically corroding carbon steel or cast iron and bentonite. The purpose of this report is to describe the modelling work that has been carried out, and the conclusions that have been reached. The experimental programme has carried out a series of long term experiments looking at anaerobic corrosion of carbon steel or cast iron in compacted MX80 bentonite at 30 deg C or 50 deg C. In the bentonite the concentration of iron decreased with increasing distance away from the iron-bentonite interface, with local iron concentrations as high as 20 wt % in

  12. Review of the interactions between bentonite and cement

    International Nuclear Information System (INIS)

    Duerden, S.L.

    1992-01-01

    Properties of bentonite may be significantly affected by reaction with cement. This report reviews the literature to identify the reactions that may occur and considers their effects on the performance of bentonite in these applications. The dominant reactions expected under alkaline conditions prevalent in an underground repository where cement is used extensively are zeolitization, beidellitization, and ion exchange. Zeolitisation will occur at high temperatures (200 o C) or after long periods (500-1000 years) when the pH is high (pH>9). Beidellitization may occur at high pH (pH>9). The silica may reprecipitate in situ due to low hydraulic conductivity or in regions of low pH or temperature. This may result in reduced porosity/permeability and plasticity. Ion exchange reactions are virtually instantaneous. The rate of the reaction depends on the concentration and rate of access of ground water. Substitution of Ca 2+ ions from cement for Na + ions in sodium-bentonites will result in reduced swelling pressure and plasticity, and increased hydraulic conductivity of the bentonite. The effect of Na-bentonite on the properties of cement is the formation of an Al-substituted 11A tobermorite, which results in improved Cs + sorption. In cements reacted with Calcium-bentonite the main product was found to be a hydroxyapatite layer on the cement surface. (author)

  13. Diffusive transport of strontium-85 in sand-bentonite mixtures

    International Nuclear Information System (INIS)

    Gillham, R.W.; Robin, M.J.L.; Dytynyshyn, D.J.

    1983-06-01

    Diffusion experiments have been used to determine the transport of 85 Sr in sand-bentonite mixtures. The diffusion experiments were performed on one natural soil (Chalk River sand) and on seven mixtures of bentonite and silica sand, containing from 0 percent to 100 percent bentonite. Two non-reactive solutes ( 36 Cl and 3 H) and one reactive solute ( 85 Sr) were used in the study. The experiments with non-reactive solutes yielded estimates of tortuosity factors. Retardation factors were obtained from experimental porosities, experimental bulk densities, and from batch distribution coefficients (Ksub(d)). These Ksub(d) values are a simple way of describing the solute/medium reaction, and are based on the assumption that the cation-exchange reaction may be described by a linear adsorption isotherm passing through the origin. The results demonstrate that, for practical purposes and for our experimental conditions, the use of the distribution coefficient provides a convenient means of calculating the effective diffusion coefficient for 85 Sr. The porosity and bulk density were also found to have a considerable influence on the effective diffusion coefficient, through the retardation factor. Mixtures containing 5-10 percent bentonite were found to be more effective in retarding 85 Sr than either sand alone, or mixtures containing more bentonite. In the soils of higher bentonite content, the effect of increased cation-exchange capacity was balanced by a decreasing ratio of bulk density to porosity

  14. Chitosan/bentonite bionanocomposites: morphology and mechanical behavior

    International Nuclear Information System (INIS)

    Braga, C.R.C.; Melo, F.M.A. de; Vitorino, I.F.; Fook, M.V.L.; Silva, S.M.L.

    2010-01-01

    This study chitosan/bentonite bionanocomposite films were prepared by solution intercalation process, seeking to investigate the effect of the chitosan/bentonite ratio (5/1 e 10/1) on the morphology and mechanical behavior of the bionanocomposites. It was used as nanophase, Argel sodium bentonite (AN), was provided by Bentonit Uniao Nordeste-BUN (Campina Grande, Brazil) and as biopolymer matrix the chitosan of low molecular weight and degree of deacetylation of 86,7% was supplied by Polymar (Fortaleza, Brazil). The bionanocomposites was investigated by X-ray diffraction and tensile properties. According to the results, the morphology and the mechanical behavior of the bionanocomposite was affected by the ratio of chitosan/bentonite. The chitosan/bentonite ratio (5/1 and 10/1) indicated the formation of an intercalated nanostructure and of the predominantly exfoliated nanostructure, respectively. And the considerable increases in the resistance to the traction were observed mainly for the bionanocomposite with predominantly exfoliated morphology. (author)

  15. DECOVALEX II PROJECT Technical Report - Task 2C

    International Nuclear Information System (INIS)

    Jing, L.; Stephansson, O.; Chijimatzu, M.; Tsang, C.F.

    1999-05-01

    definition, simulation and results of Task 2C for predicting the fully coupled thermo-hydro-mechanical behaviour of the complete heater-buffer-rock system at the test site, especially the interactions between the different components and interfaces (heater-buffer, buffer-rock, solid-water) and buffer property determination. The problem was treated as a near-field problem, like Task 2A and 2B models. The same four research teams studied this case

  16. 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

  17. Long-term stability of bentonite. A literature review

    International Nuclear Information System (INIS)

    Laine, H.; Karttunen, P.

    2010-07-01

    The long-term thermodynamic stability of the bentonite buffer in the evolving chemical, thermal and hydrological conditions at Olkiluoto has been evaluated by reviewing the relevant experimental data and natural occurrences of bentonite that could serve as analogues for the long-term bentonite stability in the expected repository conditions, especially focussing on mineral transformations due, among others, to thermal effects including cementation. Natural occurrences with stable smectite have been reviewed and compared with Olkiluoto groundwater compositions at present and during the expected hydrogeochemical evolution of the repository. Alteration of the bentonite buffer is expected to be insignificant for natural groundwater conditions at present and for the evolving groundwater conditions at the expected thermal boundary conditions caused by the heat induced from the fuel canisters ( + and SiO 2 and elevated pH due to degradation and dissolution processes. These may alter the conditions in the repository that may favour alteration and cementation processes. The amounts of foreign materials to be used in the repository will be updated along with the progress of the construction. Also the information on their impact on the barriers needs to be evaluated in more detail, including the degradation rate, mobility or dilution of the foreign materials in the repository environment. The exchangeable cation composition of the buffer bentonite is expected to equilibrate with the surrounding groundwater during and after saturation. This process is expected to lead towards Ca-dominant exchangeable cation composition within the montmorillonite interlayer spaces in the buffer. In general it seems that the transformation towards Ca-dominated composition would favour the long-term stability of the buffer as Ca-dominated smectite (compared to Na-dominated type) has larger water retention capacity and anion incorporation to the interlayer space of montmorillonite is more

  18. Customized bentonite pellets. Manufacturing, performance and gap filling properties

    Energy Technology Data Exchange (ETDEWEB)

    Marjavaara, P.; Holt, E.; Sjoeblom, V. [VTT Technical Research Centre of Finland, Espoo (Finland)

    2013-12-15

    The goal of this work was to provide knowledge about how to manufacture customized bentonite pellets and how customized bentonite pellets perform in practice during the nuclear repository construction process. The project was mainly focused on laboratory experimental tests to optimize the pellet filling by customizing the raw materials and pellet manufacturing. Bentonite pellets were made using both extrusion and roller compaction methods. The pellets were intended for use in gaps between compacted bentonite and the rock walls in both buffer deposition holes and tunnel backfilling. Performance of different types of custom-made pellets were evaluated with regard to their ease of manufacturing, density, crush strength, abrasion resistance, water holding capacity, free swelling and also their thermal conductivity. These evaluations were done in both Finland (by VTT) and Canada (by AECL). Over 50 different varieties of pellets were roller-compaction manufactured at AECL in Canada and 20 types of extrusion pellets at VTT in Finland. The parameters that were varied during manufacturing included: bentonite raw material type, water content, pellet sizes, bentonite compaction machine parameters, use of recycled pellets, and addition of two different types of filler (illite or granitic sand) at varying addition percentages. By examining the pellets produced with these methods and materials the performance and behaviour of the bentonite pellets were evaluated in laboratory with selected tests. The work done using extrusion pellets showed that it was possible to manufacture pellets with higher water contents, up to 21 % from MX-80. This water content value was higher than what was typically possible using roller-compaction method in this study. Higher water content values allow closer compatibility with the designed bentonite buffer water content. The extrusion tests also showed that the required production simulation runs could be made successfully with reference type of MX

  19. Evaluation of permeability and swelling pressure of compacted bentonite using a calcium hydroxide solution

    International Nuclear Information System (INIS)

    Aoyagi, Takayoshi; Maeda, Munehiro; Mihara, Morihiro; Tanaka, Masuhiro

    1998-12-01

    Tests to determine the swelling pressure, permeability, compressive strength and elastic modulus of Ca-Na exchanged bentonite, Na-bentonite and Ca-bentonite at the Power Reactor and Nuclear Fuel Development Corporation have mainly used distilled water. However, disposal facilities for TRU waste will use cementateous material for packaging, backfill as well as structural support. In this case, a large amount of calcium will dissolve in groundwater flowing through the cementateous material. Therefore, it is important to investigate the mechanical properties of bentonite in calcium-rich water as part of the disposal research program for TRU waste. In order to understand the effect of the chemical composition of water on the basic mechanical properties of bentonite - part of evaluating the disposal concepts for TRU waste disposal - we tested the permeability of compacted bentonite under saturated conditions using a calcium hydroxide solution. The aqueous solution represents water dominated by the calcium component. Na-bentonite, Ca-Na exchanged bentonite and Ca-bentonite were used for swelling pressure measurement tests and permeability testing. Measures of the maximum and equilibrium swelling pressure as well as permeability we obtained. The dry density of bentonite was varied between tests. Results show that swelling pressure and permeability are dependent on dry density. In separate tests using Ca-bentonite, the bentonite-mixing rate was varied as an independent parameter. Results show that there is little change in the swelling pressure and permeability between tests using calcium hydroxide solution and distilled water for all bentonite types. (author)

  20. Resonance Strength Measurement at Astrophysical Energies: The 17O(p,α14N Reaction Studied via THM

    Directory of Open Access Journals (Sweden)

    Sergi M.L.

    2016-01-01

    Full Text Available In recent years, the Trojan Horse Method (THM has been used to investigate the low-energy cross sections of proton-induced reactions on 17O nuclei, overcoming extrapolation procedures and enhancement effects due to electron screening. We will report on the indirect study of the 17O(p,α14N reaction via the Trojan Horse Method by applying the approach developed for extracting the resonance strength of narrow resonance in the ultralow energy region. The mean value of the strengths obtained in the two measurements was calculated and compared with the direct data available in literature.

  1. Mechanisms and models for bentonite erosion

    Energy Technology Data Exchange (ETDEWEB)

    Neretnieks, Ivars; Longcheng Liu; Moreno, Luis (Dept. of Chemical Engineering and Technology, School of Chemical Science and Engineering, Royal Inst. of Technology, KTH, Stockholm (Sweden))

    2009-12-15

    There are concerns that the bentonite buffer surrounding the canisters with spent nuclear fuel may erode when non-saline groundwaters seep past the buffer. This is known to happen if the water content of ions is below the critical coagulation concentration CCC. Above the CCC the smectite forms a coherent gel, which does not release particles. One main effort in this study has been directed to assess under which conditions the pore water composition of the gel at the gel/water interface could be lower than the CCC. Another main effort has been directed to understanding the behaviour of expansive gel when the pore water is below the CCC. We have developed a Dynamic model for sodium gel expansion in fractures where the gel soaks up non-saline water as it expands. The model is based on a force balance between and on smectite particles, which move in the water. The Dynamic model of gel expansion showing the evolution in time and space of a gel was successfully tested against expansion experiments in test tubes. The expansion was measured with high resolution and in great detail over many months by Magnetic Resonance Imaging. The model also predicted the gel expansion through filters with very narrow pores well. A gel viscosity model of dilute gels was derived, which accounts for ion concentration influence as well as the volume fraction of smectite in the gel. The model accounts for the presence of the DDL, which seemingly makes the particles larger so that they interact at lower particle densities. Simulations were performed for a case where the gel expands outward into the fracture that intersects the deposition hole. Fresh groundwater approaches and passes the gel/water interface. Smectite colloids move out into the water due to the repulsive forces between the particle and by Brownian motion (effect included in the Dynamic model). The dilute gel/sol is mobilised and flows downstream in a thin region where the viscosity is low enough to permit flow. Sodium diffuses

  2. Mechanisms and models for bentonite erosion

    International Nuclear Information System (INIS)

    Neretnieks, Ivars; Longcheng Liu; Moreno, Luis

    2009-12-01

    There are concerns that the bentonite buffer surrounding the canisters with spent nuclear fuel may erode when non-saline groundwaters seep past the buffer. This is known to happen if the water content of ions is below the critical coagulation concentration CCC. Above the CCC the smectite forms a coherent gel, which does not release particles. One main effort in this study has been directed to assess under which conditions the pore water composition of the gel at the gel/water interface could be lower than the CCC. Another main effort has been directed to understanding the behaviour of expansive gel when the pore water is below the CCC. We have developed a Dynamic model for sodium gel expansion in fractures where the gel soaks up non-saline water as it expands. The model is based on a force balance between and on smectite particles, which move in the water. The Dynamic model of gel expansion showing the evolution in time and space of a gel was successfully tested against expansion experiments in test tubes. The expansion was measured with high resolution and in great detail over many months by Magnetic Resonance Imaging. The model also predicted the gel expansion through filters with very narrow pores well. A gel viscosity model of dilute gels was derived, which accounts for ion concentration influence as well as the volume fraction of smectite in the gel. The model accounts for the presence of the DDL, which seemingly makes the particles larger so that they interact at lower particle densities. Simulations were performed for a case where the gel expands outward into the fracture that intersects the deposition hole. Fresh groundwater approaches and passes the gel/water interface. Smectite colloids move out into the water due to the repulsive forces between the particle and by Brownian motion (effect included in the Dynamic model). The dilute gel/sol is mobilised and flows downstream in a thin region where the viscosity is low enough to permit flow. Sodium diffuses

  3. THM large spatial-temporal model to simulate the past 2 Ma hydrogeological evolution of Paris Basin including natural tracer transport as part of site characterization for radwaste repository project Cigéo - France

    Science.gov (United States)

    Benabderrahmane, A., Sr.

    2017-12-01

    Hydrogeological site characterization for deep geological high level and intermediate level long lived radioactive waste repository cover a large time scale needed for safety analysis and calculation. Hydrogeological performance of a site relies also on the effects of geodynamic evolution as tectonic uplift, erosion/sedimentation and climate including glaciation on the groundwater flow and solute and heat transfer. Thermo-Hydro-Mechanical model of multilayered aquifer system of Paris Basin is developed to reproduce the present time flow and the natural tracer (Helium) concentration profiles based on the last 2 Ma of geodynamic evolution. Present time geological conceptual model consist of 27 layers at Paris Basin (Triassic-Tertiary) with refinement at project site scale (29 layers from Triassic to Portlandian). Target layers are the clay host formation of Callovo-Oxfrodian age (160 Ma) and the surrounding aquifer layers of Oxfordian and Dogger. Modelled processes are: groundwater flow, heat and solutes (natural tracers) transport, freezing and thawing of groundwater (expansion and retreat of permafrost), deformation of the multilayered aquifer system induced by differential tectonic uplift and the hydro-mechanical stress effect as caused by erosion of the outcropping layers. Numerical simulation considers a period from 2 Ma BP and up to the present. Transient boundary conditions are governed by geodynamic processes: (i) modification of the geometry of the basin and (ii) temperatures along the topography will change according to a series of 15 identical climate cycles with multiple permafrost (glaciation) periods. Numerical model contains 71 layers and 18 million cells. The solution procedure solves three coupled systems of equations, head, temperature and concentrations, by the use of a finite difference method, and by applying extensive parallel processing. The major modelling results related to the processes of importance for site characterization as hydraulic

  4. Diffusion in crushed rock and in bentonite clay

    International Nuclear Information System (INIS)

    Olin, M.

    1994-04-01

    Diffusion theories for porous media with sorption are reviewed to serve as a basis for considering diffusion in simple systems like sand of crushed rock. A Fickian diffusion and linear sorption model is solved both by analytical Laplance transform and Green's function methods and by numerical methods, and then applied to small-scale experiments for Finnish low- and medium-level operating waste repositories. The main properties of bentonite are reviewed. The hydraulic conductivity of compacted bentonite is so low that the major transport mechanism is diffusion. A Fickian diffusion and linear sorption model is applied to bentonite. The main component of bentonite, montmorillonite, has a high ion-exchange capacity and thus, transport in bentonite consists of interactive chemical and diffusion phenomena. A chemical equilibrium model, CHEQ, is developed for ion-exchange reactions in bentonite water systems. CHEQ is applied to some bentonite experiments with success, especially for monovalent ions. The fitted log-binding constants for sodium exchange with potassium, magnesium, and calcium were 0.27, 1.50, and 2.10, respectively. A coupled chemical and diffusion model, CHEQDIFF, is developed to take account of diffusion in pore water, surface diffusion and ion-exchange reactions. The model is applied to the same experiments as CHEQ, and validation is partly successful. In the diffusion case, the above-mentioned values for binding constants are used. The apparent diffusion (both anions and cations) and surface diffusion (only for cations) constants used are 3.0*10 -11 m 2 /s and 6.0*10 -12 m 2 /s, respectively, but these values are questionable, as experimental results good enough for fitting are not available. (orig.). (74 refs., 27 figs., 12 tabs.)

  5. Thermal properties of bentonite under extreme conditions

    Energy Technology Data Exchange (ETDEWEB)

    Vasicek, R. [Czech Technical Univ., Centre of Experimental Geotechnics, Faculty of Civil Engineering, Prague (Czech Republic)

    2005-07-01

    Centre of Experimental Geotechnics (CEG) deals with the research of the behaviour of bentonite and clays. The measurement of thermal properties is not so frequent test in geotechnical laboratory but in relation to deep repository it is a part which should not be overlooked. The reason is the heat generated by canister with spent nuclear fuel and possible influence of the heat on the materials of the engineered barrier. In the initial stages following the burial of canister with the waste the barrier materials will be exposed to elevated temperature. According to existing information, these temperatures should not exceed 90 C. That heat can induce a creation of cracks and opening of joint between highly compacted blocks. It will predispose the bentonite barrier to penetration of water from surrounding towards to canister. Therefore easy removal of heat through the barrier is required. It is essential that the tests aimed at determining the real values of measured parameters are carried out in conditions identical with those anticipated in a future disposal system. These relatively complicated thermophysical tests are logical continuation of the simple ones, carried out under laboratory temperature and on not fully saturated samples without possibility to measure the swelling pressure. Thermophysical properties and swelling pressure are dominantly influenced by water content (which is influenced by temperature). Therefore is important to realize the tests under different moisture and thermal conditions. These tests are running at the APT-PO1 Analyser, designed to fulfill mentioned requirements - it allows measurement of thermal properties under temperature up to 200 C and swelling pressure up to 20 MPa. The device is capable to register the evolution of temperature, swelling and vapor pressure. The measurement of thermal conductivity and volume heat capacity is realized by the dynamic impulse method with point source of heat. Four types of tests are possible: at

  6. Lake restoration with aluminium, bentonite and Phoslock: the effect on sediment stability and light attenuation

    DEFF Research Database (Denmark)

    Egemose, Sara; Reitzel, Kasper; Flindt, Mogens

    treatments on aluminium mobility, sediment stability or light climate. A laboratory flume experiment including three shallow Danish lakes was conducted. We measured the effects of aluminium, Phoslock (a commercial product), bentonite, and a combination of bentonite/aluminium. Each treatment caused a varying...... consolidation of the sediment. The largest consolidation occurred using Phoslock- and bentonite-addition followed by bentonite/aluminium-addition, whereas aluminium alone had no effect. Sediment stability thresholds were measured before and after addition. Especially Phoslock, but also bentonite and bentonite....../aluminium increased sediment erosion threshold, with respectively 200%, 43% and 57%. Aluminium, bentonite/aluminium, and Phoslock improved the light conditions in the water phase, with respectively 60%, 57% and 50%, whereas bentonite created higher turbidity. Conclusively aluminium improved the light conditions...

  7. Effect of seawater and high-temperature history on swelling characteristics of bentonite

    International Nuclear Information System (INIS)

    Tanaka, Yukihisa; Nakamura, Kunihiko

    2005-01-01

    In the case of construction of repository for nuclear waste near the coastal area, the effect of seawater on swelling characteristics of bentonite as an engineering as an engineering barrier should be considered. Effects of high-temperature history on swelling characteristics of bentonite should also be considered because nuclear waste generates heat. Thus, in this study, swelling characteristics of bentonite on the conditions of high temperature history and seawater are investigated. The results of this study imply that : (1) Swelling strain of sodium bentonite or transformed sodium bentonite decrease as the salinity of water increases, whereas those of calcium bentonite are not affected by salinity of the water. (2) Quantitative evaluation method for swelling strain and swelling pressure of several kinds of bentonites under brine is proposed. (3) Using distilled water, swelling strain and swelling pressure of sodium bentonite with high-temperature history is less than those without high-temperature history. (author)

  8. Thermic and thermodynamic properties of desorption process of essential oil of Hyssopus seravshanicus from bentonite clays

    International Nuclear Information System (INIS)

    Kukaniev, M.A.; Badalov, A.B.; Sharopov, F.S.

    2004-01-01

    It shown, that desorption process of essential oil of Hyssopus seravshanicus from bentonite clays include by four parts (lines) and the nature between essential oil of Hyssopus seravshanicus from bentonite clays is physical and chemical sorption

  9. Field test of ethanol/bentonite slurry grouting into rock fracture

    International Nuclear Information System (INIS)

    Motoyuki Asada; Hitoshi Nakashima; Takashi Ishii; Sumio Horiuchi

    2006-01-01

    Crystalline rocks have fractures which may cause unexpected routes of groundwater seepage. Cement grouting is one of the most effective methods to minimize seepage; however, cement materials may not be suitable for the purpose of extra-long durability, because cement is neutralized or degraded by chemical and physical influence of chemical reaction. Natural clay like bentonite is one of the most promising materials for seepage barrier; however, water/bentonite grout is so viscous that enough amount of bentonite can not be grouted into rock fractures. To increase bentonite content in grout with low viscosity, the utilization of ethanol as a mixing liquid was studied. Ethanol suppresses bentonite swelling, and more bentonite can be injected more than that of water/bentonite slurry. In this paper, grouting into in-situ rock mass fracture from the ground surface was tested to investigate the barrier performance and workability of ethanol/bentonite slurry as a grouting material. (author)

  10. Observations of bentonite-hyper-alkaline fluid and bentonite-cement interactions by the X-ray computed tomography

    International Nuclear Information System (INIS)

    Nakabayashi, R.; Chino, D.; Kawaragi, C.; Sato, T.; Yoneda, T.; Kaneko, K.; Shibata, S.; Sakamoto, H.

    2010-01-01

    Document available in extended abstract form only. Bentonite-hyper-alkaline fluid interaction has been a key research issue in the performance assessment of radioactive waste disposal. It has therefore been investigated based on the dissolution rate of smectite (main constituent mineral of bentonite) under such hyper-alkaline condition. Generally, the dissolution rate has been obtained from batch and flow-through experiments under the conditions with high fluid/solid weight rations. These previous studies have provided a contribution to kinetic model of smectite dissolution. Some of them in particularly showed some equations explaining the effect of different factors such as pH of reactive fluid, temperature and deviation from equilibrium on smectite dissolution rate. However, the experimental conditions in such studies were completely different from the conditions in actual radioactive waste disposal system. For quantitative understanding, dissolution experiments for the compacted bentonite have also been conducted. These studies showed that the dissolution rate of compacted bentonite was different from that of batch and flow-through experiments. However, the difference has not been understood in details. On the other hand, the interface between bentonite and cement has also been investigated by experiments in laboratories and field sites, via reaction transport modelling. Despite the very few in numbers of experimental results as function of time, there are many long-term modelling works intended for bentonite-cement interaction. The models developed by many authors should be verified by comparing results of the model calculations with experimental observations. The experimental results with different conditions are therefore necessary for verifications and comparisons. Even in the experimental works done previously, the alteration process at the interface has mainly been observed by EPMA. EPMA is a destructive analysis with lower time resolution for 2D images

  11. Results From an International Simulation Study on Coupled Thermal, Hydrological, and Mechanical (THM) Processes Near Geological Nuclear Waste Repositories

    International Nuclear Information System (INIS)

    J. Rutqvist; D. Barr; J.T. Birkholzer; M. Chijimatsu; O. Kolditz; Q. Liu; Y. Oda; W. Wang; C. Zhang

    2006-01-01

    As part of the ongoing international DECOVALEX project, four research teams used five different models to simulate coupled thermal, hydrological, and mechanical (THM) processes near waste emplacement drifts of geological nuclear waste repositories. The simulations were conducted for two generic repository types, one with open and the other with back-filled repository drifts, under higher and lower postclosure temperatures, respectively. In the completed first model inception phase of the project, a good agreement was achieved between the research teams in calculating THM responses for both repository types, although some disagreement in hydrological responses is currently being resolved. In particular, good agreement in the basic thermal-mechanical responses was achieved for both repository types, even though some teams used relatively simplified thermal-elastic heat-conduction models that neglected complex near-field thermal-hydrological processes. The good agreement between the complex and simplified process models indicates that the basic thermal-mechanical responses can be predicted with a relatively high confidence level

  12. Radioassay of vitamin B-12 employing bentonite

    International Nuclear Information System (INIS)

    Lewin, N.; Fries, J.E.; Richards, C.S.

    1976-01-01

    Radioassay for vitamin B-12 using the unknown quantity of non-radioactive vitamin B-12 released from serum mixed with the radioactivity of a known quantity of radioactive vitamin B-12 tracer. A solution of intrinsic factor having a binding capacity less than the quantity of serum vitamin B-12 and radioactive vitamin B-12 is used to bind a portion of the vitamin B-12 mixture. The vitamin B-12 not bound to intrinsic factor is removed by addition of a bentonite-containing tablet. The quantity of radioactive vitamin B-12 bound to intrinsic factor is compared with standard values and the unknown serum vitamin B-12 obtained. In the steps of the procedure the acid assay medium is pre-combined with the radioactive tracer so that the radioactive vitamin B-12 tracer receives the same treatment as serum vitamin B-12. Certain of the other reagent solutions are pre-combined and the concentration of the components adjusted so that the volume used of each of these other reagent solutions is the same in different assay steps. Thus, fewer pipetting steps are necessary. 7 claims, 1 drawing figure

  13. Analysis of corrosion products of carbon steel in wet bentonite

    International Nuclear Information System (INIS)

    Osada, K.; Nagano, T.; Kozai, N.; Nakashima, S.; Nakayama, S.; Muraoka, S.

    1991-01-01

    The following conclusions were obtained; (1) At 40degC, the average corrosion rate of SS41 carbon steel in wet bentonite was 0.025 mm/y. This is smaller than the value of 0.042 mm/y obtained in pure water at 40degC. However, at 95degC, the corrosion rate of SS41 carbon steel in wet bentonite was 0.27 mm/y, which is much larger than that in pure water at 95degC. (2) At 95degC, γ-FeO(OH) (lepidocrocite) was formed only in wet bentonite, and it was absent in pure water. Evaporation of moisture resulted in the formation of partial covering of bentonite, which promoted local corrosion. Consequently, γ-FeO(OH) was considered to be formed. (3) In wet bentonite at 95degC, α-Fe 2 O 3 (hematite) can be identified by means of colorimetry. The color of corrosion products is orangish, indicating the contribution of α-Fe 2 O 3 in iron hydroxides. (author)

  14. Tracer diffusion in compacted, water-saturated bentonite

    International Nuclear Information System (INIS)

    Bourg, Ian C.; Sposito, Garrison; Bourg, Alain C.M.

    2005-01-01

    Compacted Na-bentonite clay barriers, widely used in the isolation of solid-waste landfills and other contaminated sites, have been proposed for a similar use in the disposal of high-level radioactive waste. Molecular diffusion through the pore space in these barriers plays a key role in their performance, thus motivating recent measurements of the apparent diffusion coefficient tensor of water tracers in compacted, water-saturated Na-bentonites. In the present study, we introduce a conceptual model in which the pore space of water-saturated bentonite is divided into 'macropore' and 'interlayer nanopore' compartments. With this model we determine quantitatively the relative contributions of pore-network geometry (expressed as a geometric factor) and of the diffusive behavior of water molecules near montmorillonite basal surfaces(expressed as a contrastivity factor) to the apparent diffusion coefficient tensor. Our model predicts, in agreement with experiment, that the mean principal value of the apparent diffusion coefficient tensor follows a single relationship when plotted against the partial montmorillonite dry density (mass of montmorillonite per combined volume of montmorillonite and pore space). Using a single fitted parameter, the mean principal geometric factor, our model successfully describes this relationship for a broad range of bentonite-water system, from dilute gel to highly-compacted bentonite with 80 percent of its pore water in interlayer nanopores

  15. Iodine sorption of bentonite - radiometric and polarographic study

    International Nuclear Information System (INIS)

    Konirova, R.; Vinsova, H.; Koudelkova, M.; Ernestova, M.; Jedinakova-Krizova, V.

    2003-01-01

    The experiments focused on kinetics of iodine retardation on bentonite, influence of aqueous phase pH, buffering properties of bentonite, etc. were carried out by batch method. Distribution coefficient KD was the criterion applied for evaluation of iodine interaction with solid phase. High sorption potential of bentonite to cationic forms of various radionuclides, resulting from relatively high cation exchange capacity, is generally known. On the other hand the inorganic anions are not adsorbed strongly to mineral surface of clays thus uptake of iodine (occurring mainly at iodide (I - ) or iodate (IO 3 - ) form under oxoic conditions) is limited. The distribution coefficients of iodine anions' sorption on bentonite R reach order of magnitude 10 -1 mL/g. In order to increase the sorption capacity of the solid phase, several additives were added to bentonite. Most of them didn't provide satisfactory results except of the addition of activated carbon, which has high surface area. Electromigration and polarographic methods were used for investigation of the redox state of iodine in aqueous phase and determination of KD values as well. Acquired results were compared with data obtained by radiometric measurements. (authors)

  16. Hydrothermal alkaline stability of bentonite barrier by concrete interstitial wastes

    International Nuclear Information System (INIS)

    Leguey Jimenez, S.; Cuevas Rodriguez, J.; Ramirez Martin, S.; Vigil de la villa Mencia, R.; Martin Barca, M.

    2002-01-01

    At present, the main source of High Level radioactive Waste (HLW) is the electrical energy production during all the steps of developing. In almost all the countries with nuclear programs, the option for the final management of HLW is the Deep Geological Repository (DGR) based on the concept of multi barrier. According to this concept, the waste is isolated from biosphere by the interposition of confinement barriers. Two of the engineering barriers in the Spanish design of DGR in granitic rock are compacted bentonite and concrete. The bentonite barrier is the backfilling and sealing material for the repository gallery, because of its mechanical and physico-chemical properties. The main qualities of concrete as a component of a multi barrier system are its low permeability, mechanical resistance and chemical properties. With regard to chemical composition of concrete, the alkaline nature of cement pore water lowers the solubility of many radioactive elements. However, structural transformation in smectite, dissolution or precipitation of minerals and, consequently, changes in the bentonite properties could occurs in the alkaline conditions generated by the cement degradation. The main objective of the present work is to evaluate the effect of concrete in the stability of Spanish reference bentonite (La Serrata of Nijar, Almeria, Spain) in conditions similar to those estimated in a DGR in granitic rock. Because of the main role of bentonite barrier in the global performance of the repository, the present study is essential to guarantee its security. (Author)

  17. Diffusion, sorption, and retardation processes of anions in bentonite and organo-bentonites for multibarrier systems

    Science.gov (United States)

    Schampera, Birgit; Dultz, Stefan

    2013-04-01

    The low permeability, high cation exchange capacity (CEC) and plasticity of bentonites favor their use in multibarrier systems of waste deposits [1]. Bentonites have a high CEC but their ability to sorb anions is very low. There is, however, need for retardation of anions and organic pollutants in many applications. Bentonites, modified with certain organic cations, have the capacity to sorb anions and non-polar organic compounds in addition to cations. Investigations on organically modified clays address a wide variety of applications including immobilization of pollutants in contaminated soils, waste water treatment and in situ placement for the protection of ground water [2]. Many experiments on anion and cation sorption of organo-clays were conducted in the batch mode which does not reflect solid-liquid ratios and material densities in barrier systems. Diffusion experiments on compacted clays allow the evaluation of transport processes and sorption of pollutants at conditions relevant for repositories. For organo-clays only few diffusion studies are published e.g. [3] measured the diffusion of tritium and [4] the diffusion of H2O in bentonite and organo-bentonites. The organic cation hexadecylpyridinium (HDPy) was added to Wyoming bentonite (MX-80) in amounts corresponding to 2-400 % of the CEC. The uptake of organic cations was determined by the C-content, XRD and IR-spectroscopy. Wettability was analyzed by the contact angle. Physical, chemical and mineralogical properties of clays were characterized. Diffusion experiments were carried out in situ in a cell attached to the ATR-unit of a FTIR-spectrometer. For H2O-diffusion the compacted organo-clays are saturated first with D2O, afterwards H2O is supplied to the surface at the top of the clay platelet. Anion-diffusion was conducted with NO3--solution instead of H2O only having characteristic IR band positions at 1350 cm-1. Three different concentrations (0.25M, 0.5M and 1M) were used. Additional batch

  18. Evaluation for swelling characteristics of buffer and backfill materials for high-level nuclear waste disposal. Influence of sand-bentonite content and cation compositions in bentonite

    International Nuclear Information System (INIS)

    Komine, Hideo; Ogata, Nobuhide

    1999-01-01

    Compacted bentonite and sand-bentonite mixture are attracting greater attention as buffer and backfill materials for disposal pits and access tunnels in the underground facilities for repositories of high-level nuclear waste. Buffer and backfill materials must have the swelling characteristics and are expected to fill up the space between these materials and surrounding ground by swelling. This role is called as 'Self-sealing'. To design the specifications, such as dry density, bentonite content and size, of buffer and backfill materials for the disposal facilities of high-level nuclear wastes described above, we must evaluate the swelling characteristics of compacted bentonite and sand-bentonite mixtures. For this purpose, this study proposed the evaluation formula for swelling characteristics of buffer and backfill materials containing bentonite. This study derived new equations for evaluating the relationship between the swelling deformation of compacted bentonite and sand-bentonite mixtures, and the swelling behavior of montmorillonite minerals, which are swelling clay minerals. This study also proposed new equations for evaluating the ion compositions of bentonite, ion concentration of pore water and the specific surface of bentonite, which significantly influence the swelling characteristics of buffer and backfill materials. The evaluation formula proposed in this study is presented by combining the above-mentioned new equations with theoretical equations, of which are the Gouy-Chapman diffuse double layer theory and the van der Waals force, of repulsive and attractive forces of montmorillonite minerals. (author)

  19. Evaluation of bentonite alteration due to interactions with iron. Sensitivity analyses to identify the important factors for the bentonite alteration

    International Nuclear Information System (INIS)

    Sasamoto, Hiroshi; Wilson, James; Sato, Tsutomu

    2013-01-01

    Performance assessment of geological disposal systems for high-level radioactive waste requires a consideration of long-term systems behaviour. It is possible that the alteration of swelling clay present in bentonite buffers might have an impact on buffer functions. In the present study, iron (as a candidate overpack material)-bentonite (I-B) interactions were evaluated as the main buffer alteration scenario. Existing knowledge on alteration of bentonite during I-B interactions was first reviewed, then the evaluation methodology was developed considering modeling techniques previously used overseas. A conceptual model for smectite alteration during I-B interactions was produced. The following reactions and processes were selected: 1) release of Fe 2+ due to overpack corrosion; 2) diffusion of Fe 2+ in compacted bentonite; 3) sorption of Fe 2+ on smectite edge and ion exchange in interlayers; 4) dissolution of primary phases and formation of alteration products. Sensitivity analyses were performed to identify the most important factors for the alteration of bentonite by I-B interactions. (author)

  20. Migration Behaviour of Strontium in Czech Bentonite Clay

    Directory of Open Access Journals (Sweden)

    Lucie Baborova

    2016-09-01

    Full Text Available The study deals with sorption and diffusion behaviour of strontium in Czech bentonite B75. The study is a part of a research on reactive transport of radioactive contaminants in barrier materials of a deep geological repository of radioactive waste in the Czech Republic. Series of sorption and diffusion experiments with Sr and non-activated Ca bentonite B75 produced in the Czech Republic were performed in two background solutions (CaCl2 and NaCl. On the basis of sorption batch experiments the kinetics of strontium sorption on bentonite was assessed and the sorption isotherms for various experimental conditions were obtained. As a result of performed diffusion experiments the parameters of diffusion (i.e. effective diffusion coefficient De and apparent diffusion coefficient Da were determined. The observed discrepancies between sorption characteristics obtained from the sorption and diffusion experiments are discussed.

  1. Decantation time of evaluation on bentonite clays fractionation

    International Nuclear Information System (INIS)

    Gomes, J.; Menezes, R.R.; Neves, G.A.; Lira, H.L; Santana, L.N.L.

    2009-01-01

    Bentonite clays present a great number of industrial uses, from petroleum to pharmaceutics and cosmetic industry. The bentonite clay present particles with very fine particles that is responsible by the vast application of these materials. However, commercial clays present wide particle size distribution and a significant content of impurities, particularly quartz, in the form of silt and fine silt. So, the aim of this work is to analyze the effect of the stirring and decantation time in the deagglomeration, purification and size separation of the bentonite clay particles from Paraiba. The clays were characterized by X-ray diffraction and particle size distribution. Based on the results it was observed the decantation time give the elimination of the agglomerates formed by submicrometric particles. The uses of decantation column give separation of the fraction below 200nm. (author)

  2. Effect of organic matter on 125I diffusion in bentonite

    International Nuclear Information System (INIS)

    Tao Wu; Qing Zheng

    2015-01-01

    Through-diffusion method was conducted to investigate the diffusion behavior of 125 I in bentonite in present of organic matter, such as polyaminopolycarboxylate EDTA, oxalic acid, hydrazine and humic acid HA. The effective diffusion coefficient D e value and rock capacity factor α were (2.32.6) × 10 -11 m 2 /s and 0.040-0.052, respectively. The small difference showed that iodine was preferentially associated with silicoaluminate mineral as an inorganic form. In present of HA, the D a value of 125 I was almost two orders of magnitude higher than that of HA and humic substances HS. The D e and α derived from the experiments were used to simulate its diffusion in the designed bentonite obstacle of high-level radioactive waste repository and the results showed that 125 I can be transported from 30 to 50 cm thickness of bentonite to the far-field of repository in several years. (author)

  3. Organophilization process of Brazilian bentonite for preparation of polymeric nanocomposites

    International Nuclear Information System (INIS)

    Oliveira, Carlos I.R. de; Rocha, Marisa C.G.; Ferreira, Joao L.A.N.G.

    2015-01-01

    Bentonite clay from the municipality of Cubati, PB, was used for the preparation of an organophilic clay. First, the clay was treated with sodium chloride to obtain the homo-ionic sodium clay. The organoclay was, then, obtained from the reaction of homo-ionic clay with the quaternary ammonium salt, cetyltrimethyl ammonium chloride. The natural clay and the modified clays were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The chemical analysis showed a decrease in the concentration of the majority of the metallic oxides when the bentonite was organophilizated. This result is characteristic of the metal cation exchange process by organic salt molecules. The X-ray diffraction confirmed the intercalation among the layers of the clay. The results obtained by FTIR showed the presence of the characteristic groups of the salt in the clay, thus confirming the obtaining of organophilic bentonite. (author)

  4. Database on gas migration tests through bentonite buffer material

    International Nuclear Information System (INIS)

    Tanai, Kenji

    2009-02-01

    Carbon steel is a candidate material for an overpack for geological disposal of high-level radioactive waste in Japan. The corrosion of the carbon steel overpack in aqueous solution under anoxic conditions will cause the generation of hydrogen gas, which may affect hydrological and mechanical properties of the bentonite buffer. To evaluate such an effect of gas generation, it is necessary to develop a model of gas migration through bentonite buffer material taking account of data obtained from experiments. The gas migration experiments under both unsaturated and saturated conditions have been carried out to clarify the fundamental characteristics of bentonite for gas migration. This report compiles the experimental data obtained from gas migration tests for buffer material which has been conducted by JAEA until December, 2007. A CD-ROM is attached as an appendix. (author)

  5. Review of SKB's Work on Coupled THM Processes Within SR-Can. External review contribution in support of SKI's and SSI's review of SR-Can

    Energy Technology Data Exchange (ETDEWEB)

    Rutqvist, Jonny; Chin-Fu Tsang (Lawrence Berkeley National Laboratory, Berkeley, CA (US))

    2008-03-15

    In this report, we scrutinize the work by the Swedish Nuclear Fuel and Waste Management Company (SKB) related to coupled thermal, hydrological and mechanical (THM) processes within the SR-Can project. SR-Can is SKB's preliminary assessment of long-term safety for a KBS-3 nuclear waste repository, and is a preparation stage for the SR-Site assessment, the report that will be used in SKB's application for a final repository. We scrutinize SKB's work related to THM processes through review and detailed analysis, using an independent modeling tool. The modeling tool is applied to analyze coupled THM processes at the two candidate sites, Forsmark and Laxemar, using data defined in SKB's site description models for respective sites. In this report, we first provide a brief overview of SKB's work related to analysis of the evolution of coupled THM processes as presented in SRCan, as well as supporting documents. In this overview we also identify issues and assumptions that we then analyze using our modeling tool. The overview and subsequent independent model analysis addresses issues related to near-field behavior, such as buffer resaturation and the evolution of the excavation-disturbed zone, as well as far-field behavior, such as stress induced changes in hydrologic properties. Based on the review and modeling conducted in this report, we conclude by identifying a number of areas of weaknesses, where we believe further work and clarifications are needed. Some of the most important ones are summarized below: 1) We found that SKB's calculation of peak temperature might not have been conducted for the most conservative case of extreme drying of the buffer under dry rock conditions and an unexpectedly high thermal diffusion coefficient. Our alternative analysis indicates that temperatures close to 100 might be achieved under unfavorable (and perhaps unexpected) conditions in which the buffer is dried to below 20% near the canister. We believe

  6. Characterization of bentonite clay from “Greda” deposit

    Directory of Open Access Journals (Sweden)

    Nadežda Stanković

    2011-06-01

    Full Text Available Based on mineralogical and technological investigations of the deposit “Greda” important characteristics of bentonite clay were determined. Representative samples of the deposit were characterized with X-ray diffraction, low-temperature nitrogen adsorption, chemical analysis, differential thermal analysis and scanning electron microscopy. It was determined that the main mineral is montmorillonite and in subordinate quantities kaolinite, quartz and pyrite. The chemical composition generally shows high silica and alumina contents in all samples and small quantities of Fe3+, Ca2+ and Mg2+ cations. Based on technological and mineralogical research, bentonite from this deposit is a high-quality raw material for use in the ceramic industry.

  7. Evaluation of phenomena affecting diffusion of cations in compacted bentonite

    International Nuclear Information System (INIS)

    Muurinen, A.; Lehikoinen, J.

    1995-04-01

    In a number of diffusion studies, contradictions between the apparent diffusivities of cations and their distribution coefficients in bentonite have been found. Two principal reasons have been offered as explanations for this discrepancy; diffusion of the sorbed cations, often called surface diffusion, and the decrease of sorption in compacted clay compared to a sorption value obtained from a batch experiment. In the study the information available from the literature on sorption-diffusion mechanisms of cations in bentonite has been compiled and re-interpreted in order to improve the understanding of the diffusion process. (103 refs., 23 figs., 8 tabs.)

  8. Thermal conductivity tests on buffermasses of bentonite/silt

    International Nuclear Information System (INIS)

    Knutsson, S.

    1977-09-01

    The investigation concerns the thermal conductivity of the bentonite/quartz buffer mass suggested as embedding substance for radioactive canisters. The first part presents the theoretical relationships associated with the various heat transfer mechanisms in moist granular materials. Chapter 3 describes the author's experimental determination of the thermal conductivity of the buffer mass. The tested mass consisted of 10 percent (by weight) bentonite and 90 percent natural silt. Four tests were made with different water content values and degree of water saturation. A comparison between the measured and calculated thermal conductivities is given. It is shown that the conductivity can be calculated with an accuracy of +-20 percent. (author)

  9. Structure and forces in bentonite MX-80

    International Nuclear Information System (INIS)

    Joensson, Bo; Aakesson, Torbjoern; Joensson, Bengt; Meehdi, Segad; Janiak, John; Wallenberg, Reine

    2009-03-01

    Wyoming bentonite (MX-80) and its ion exchanged forms, Na and Ca montmorillonite, have been studied experimentally and theoretically. A variety of experimental techniques have been used in order to gain insight into the structural conditions in dry clay as well as clay in equilibrium with a bulk solution of given ionic composition. The main objective has been the swelling behaviour and osmotic pressure of montmorillonite clay when the bulk solution contains a mix of monovalent sodium and divalent calcium ions. For a clay system in equilibrium with pure water, Monte Carlo simulations predict a large swelling when the clay counterions are monovalent, while in presence of divalent counterions a limited swelling is predicted with an aqueous layer between the clay lamellaes of about 1 nm. This latter result is in excellent agreement with small angle x-ray scattering data, but in disagreement with dialysis experiments, which gives a significantly larger swelling for Ca montmorillonite in pure water. Obviously, there is one lamellar swelling and a second 'extra-lamellar' swelling, which could be the result of a phase separation in the clay. Montmorillonite in contact with a salt reservoir with both Na + and Ca 2+ counterions will only show a modest swelling unless the sodium concentration in the bulk is several orders of magnitude larger than the calcium concentration. The limited swelling of clay in presence of divalent counterions is a consequence of ion-ion correlations, which reduce the entropic repulsion as well as give rise to an attractive component in the total osmotic pressure. Ion-ion correlations also favour divalent counterions in a situation where we have a competition with monovalent ones. A more fundamental result of ion-ion correlations is that the osmotic pressure as a function of clay sheet separation becomes nonmonotonic, which indicates the possibility of a phase separation into a concentrated and a dilute clay phase. This phenomenon could explain the

  10. Strength and Compaction Analysis of Sand-Bentonite-Coal Ash Mixes

    Science.gov (United States)

    Sobti, Jaskiran; Singh, Sanjay Kumar

    2017-08-01

    This paper deals with the strength and compaction characteristics of sand-bentonite-coal ash mixes prepared by varying percentages of sand, bentonite and coal ash to be used in cutoff walls and as a liner or cover material in landfills. The maximum dry density (MDD) and optimum moisture content (OMC) of sand-bentonite mixes and sand-bentonite-coal ash mixes were determined by conducting the standard proctor test. Also, the strength and stiffness characteristics of soil mixes were furnished using unconfined compressive strength test. The results of the study reveal influence of varying percentages of coal ash and bentonite on the compaction characteristics of the sand-bentonite-coal ash mixes. Also, validation of a statistical analysis of the correlations between maximum dry density (MDD), optimum moisture content (OMC) and Specific Gravity (G) was done using the experimental results. The experimental results obtained for sand-bentonite, sand-bentonite-ash and coal ash-bentonite mixes very well satisfied the statistical relations between MDD, OMC and G with a maximum error in the estimate of MDD being within ±1 kN/m3. The coefficient of determination (R2) ranged from 0.95 to 0.967 in case of sand-bentonite-ash mixes. However, for sand-bentonite mixes, the R2 values are low and varied from 0.48 to 0.56.

  11. Numerical simulation of alteration of sodium bentonite by diffusion of ionic groundwater components

    International Nuclear Information System (INIS)

    Jacobsen, J.S.; Carnahan, C.L.

    1987-12-01

    Experiments measuring the movement of trace amounts of radionuclides through compacted bentonite have typically used unaltered bentonite. Models based on experiments such as these may not lead to accurate predictions of the migration through altered or partially altered bentonite of radionuclides that undergo ion exchange. To address this problem, we have modified an existing transport code to include ion exchange and aqueous complexation reactions. The code is thus able to simulate the diffusion of major ionic groundwater components through bentonite and reactions between the bentonite and groundwater. Numerical simulations have been made to investigate the conversion of sodium bentonite to calcium bentonite for a reference groundwater characteristic of deep granitic formations. 20 refs., 2 figs., 2 tabs

  12. Study on the properties of Gaomiaozi bentonite as the buffer/backfilling materials for HLW disposal

    International Nuclear Information System (INIS)

    Liu Xiaodong; Luo Taian; Zhu Guoping; Chen Qingchun

    2007-12-01

    Systematic studies including mineral composition and structure, physico- chemical properties and thermal properties have been conducted on Gaomiaozi bentonite, Xinghe County, Inner Mongolia Autonomous Region. The compaction characteristics of bentonite and the influence of additive to bentonite have been discussed. The analysis of mineral composition and structure show that the bentonite ores are dominated by montmorillonite. Preliminary studies of the characteristics of ores indicated that No-type bentonite from the deposit has good absorption, excellent swelling and high cation exchangeability. The compressibility of bentonite will be improved by adding the additives such as quartz sand. The studies indicated that the characteristics of Gaomiaozi bentonite can satisfy the requirement of buffer/backfilling materials for HLW repository and the ores can be selected as the preferential candidate to provide buffer/backfill- ing materials for HLW repository in China. (authors)

  13. Study on the properties of Gaomiaozi bentonite as the buffer/backfilling materials for HLW disposal

    Energy Technology Data Exchange (ETDEWEB)

    Xiaodong, Liu [East China Inst. of Technology, Fuzhou (China); [Key Laboratory of Nuclear Resources and Environment of Ministry of Education, Fuzhou (China); Taian, Luo; Guoping, Zhu; Qingchun, Chen [East China Inst. of Technology, Fuzhou (China)

    2007-12-15

    Systematic studies including mineral composition and structure, physico- chemical properties and thermal properties have been conducted on Gaomiaozi bentonite, Xinghe County, Inner Mongolia Autonomous Region. The compaction characteristics of bentonite and the influence of additive to bentonite have been discussed. The analysis of mineral composition and structure show that the bentonite ores are dominated by montmorillonite. Preliminary studies of the characteristics of ores indicated that No-type bentonite from the deposit has good absorption, excellent swelling and high cation exchangeability. The compressibility of bentonite will be improved by adding the additives such as quartz sand. The studies indicated that the characteristics of Gaomiaozi bentonite can satisfy the requirement of buffer/backfilling materials for HLW repository and the ores can be selected as the preferential candidate to provide buffer/backfill- ing materials for HLW repository in China. (authors)

  14. Enhanced sealing project: monitoring the THM response of a full-scale shaft seal

    Energy Technology Data Exchange (ETDEWEB)

    Dixon, D.A.; Martino, J.B.; Holowick, B.; Priyanto, D. [Atomic Energy of Canada Limited, Pinawa, MB (Canada)

    2011-07-01

    Closure of the subsurface facilities at Atomic Energy of Canada Limited's (AECL) Underground Research Laboratory (URL) was completed in 2010 with installation of a concrete surface cap. Additionally, as part of decommissioning, seals were installed at the penetration of the shafts through the major hydro-geological feature known as Fracture Zone 2 (FZ2). The seal construction was funded by Natural Resources Canada (NRCan) under the Nuclear Legacy Liabilities Program (NLLP). The shaft seals at the URL were based on the composite seal concept developed for application in a deep geological repository for disposal of used nuclear fuel. The access shaft seal consists of two 3-m thick concrete segments that rigidly confine a 6-m long section of swelling clay-based material (40% bentonite clay - 60% sand by dry mass). Monitoring of the regional groundwater recovery following flooding of the lower shaft is a closure requirement and was included in the design. It was widely recognized that the installation of the seals at the URL represented a unique opportunity to monitor the evolution of the type of seal that might be installed in an actual repository but the NLLP mandate did not include any monitoring of shaft seal evolution. As a result the Enhanced Sealing Project (ESP) partnership composed of NWMO, Posiva, SKB and ANDRA was established and a set of 68 instruments (containing 100 sensors) were installed to monitor the evolution of the seal. In the first year of operation sensors have monitored the following parameters in the ESP: thermal evolution and strain of the concrete components, thermal, hydraulic and mechanical changes in the clay component and its contacts with the rock and concrete confinement. Additionally, monitoring of the near-field and regional groundwater evolution has been undertaken. Monitoring of the short-term thermal-mechanical evolution of the concrete components was successfully accomplished and only a small temperature rise occurred due to

  15. Enhanced sealing project: monitoring the THM response of a full-scale shaft seal

    International Nuclear Information System (INIS)

    Dixon, D.A.; Martino, J.B.; Holowick, B.; Priyanto, D.

    2011-01-01

    Closure of the subsurface facilities at Atomic Energy of Canada Limited's (AECL) Underground Research Laboratory (URL) was completed in 2010 with installation of a concrete surface cap. Additionally, as part of decommissioning, seals were installed at the penetration of the shafts through the major hydro-geological feature known as Fracture Zone 2 (FZ2). The seal construction was funded by Natural Resources Canada (NRCan) under the Nuclear Legacy Liabilities Program (NLLP). The shaft seals at the URL were based on the composite seal concept developed for application in a deep geological repository for disposal of used nuclear fuel. The access shaft seal consists of two 3-m thick concrete segments that rigidly confine a 6-m long section of swelling clay-based material (40% bentonite clay - 60% sand by dry mass). Monitoring of the regional groundwater recovery following flooding of the lower shaft is a closure requirement and was included in the design. It was widely recognized that the installation of the seals at the URL represented a unique opportunity to monitor the evolution of the type of seal that might be installed in an actual repository but the NLLP mandate did not include any monitoring of shaft seal evolution. As a result the Enhanced Sealing Project (ESP) partnership composed of NWMO, Posiva, SKB and ANDRA was established and a set of 68 instruments (containing 100 sensors) were installed to monitor the evolution of the seal. In the first year of operation sensors have monitored the following parameters in the ESP: thermal evolution and strain of the concrete components, thermal, hydraulic and mechanical changes in the clay component and its contacts with the rock and concrete confinement. Additionally, monitoring of the near-field and regional groundwater evolution has been undertaken. Monitoring of the short-term thermal-mechanical evolution of the concrete components was successfully accomplished and only a small temperature rise occurred due to

  16. Pore water chemistry of Rokle Bentonite (Czech Republic)

    International Nuclear Information System (INIS)

    Cervinka, R.; Vejsada, J.

    2010-01-01

    Document available in extended abstract form only. With inflowing the groundwater to Deep Geological Repository (DGR), the interaction of this water with engineering barrier materials will alter both, barrier materials and also the groundwater. One of the most important alterations represents the formation of bentonite pore water that will affect a number of important processes, e.g. corrosion of waste package materials, solubility of radionuclides, diffusion and sorption of radionuclides. The composition of bentonite pore water is influenced primarily by the composition of solid phase (bentonite), liquid phase (inflowing groundwater), the gaseous phase (partial pressure of CO 2 ), bentonite compaction and the rate of groundwater species diffusion through bentonite. Also following processes have to be taken into account: dissolution of admixtures present in the bentonite (particularly well soluble salts, e.g. KCl, NaCl, gypsum), ion exchange process and protonation and deprotonation of surface hydroxyl groups on clay minerals. Long-term stability of mineral phases and possible mineral transformation should not be neglected as well. In the Czech Republic, DGR concept takes local bentonite into account as material for both buffer and backfill. The candidate bentonite comes from the Rokle deposit (NW Bohemia) and represents complex mixture of (Ca,Mg)-Fe-rich montmorillonite, micas, kaolinite and other mineral admixtures (mainly Ca, Mg, Fe carbonates, feldspars and iron oxides). The mineralogical and chemical characteristics were published previously. This bentonite is different in composition and properties from worldwide studied Na-bentonite (e.g. MX-80, Volclay) or Na-Ca bentonite (e.g. Febex). This fact leads to the need of investigation of Rokle bentonite in greater detail to verify its suitability as a buffer and backfill in DGR. Presented task is focused on the study of pore water evolution. Our approach for this study consists in modeling the pore water using

  17. The application of bentonite in the atomic energy field and some research results of the sorption of uranium on Vietnam bentonite

    International Nuclear Information System (INIS)

    Than Van Lien; Do Qui Son; Le Thi Kim Dung

    2008-01-01

    The properties of bentonite can be summarised as follows: low gas permeability, low hydraulic conductivity, high radionuclide retardation capacity, high swelling potential, that is why bentonite has been widely used in the atomic energy fields in many countries all over the world. Vietnam has bentonite deposits that is exploited and used in some fields. In order to use bentonite - available and abandon resources in our country for atomic energy many research activities on the field of bentonite applications have been carried out in Institute for Technology of Radioactive and Rare Elements and Dalat Nuclear Research Institute. In this content, this article introduces the application of bentonite in radioactive waste management and treatment fields (bentonite used as barrier in the deep repository for spent nuclear fuel, as barriers in landfills to prevent contamination of soil and groundwater by leachates containing radioactive, bentonite is also used as sorbent for nuclear reactor activation products (Co, Cr in the waste effluents). At the some time it is present some research results of the sorption of uranium on Vietnamese bentonite. (author)

  18. On the introduction of {sup 17}O+p reaction rates evaluated through the THM in AGB nucleosynthesis calculations

    Energy Technology Data Exchange (ETDEWEB)

    Palmerini, S.; Sergi, M. L.; La Cognata, M.; Pizzone, R. G. [I.N.F.N. Laboratori Nazionali del Sud, via Santa Sofia 62, Catania (Italy); Lamia, L.; Spitaleri, C. [Dipartimento di Fisica e Astronomia, Universitá degli Studi di Catania (Italy)

    2014-05-09

    The rates for the {sup 17}O(p,αα{sup 14}N, {sup 17}O(p,α){sup 18}F and {sup 18}O(p,α){sup 15}N reactions deduced trough the Trojan Horse Method (THM) have been introduced into a state-of-the-art asymptotic giant branch (AGB) models for proton-capture nucleosynthesis and cool bottom process. The predicted abundances have been compared with isotopic compositions provided by geochemical analysis of presolar grains. As a result, an improved agreement is found between the models and the isotopic mix of oxide grains of AGB origins, whose composition is the signature of low-temperature proton-capture nucleosynthesis.

  19. Effect of pH on the formation of disinfection byproducts in swimming pool water – Is less THM better?

    DEFF Research Database (Denmark)

    Hansen, Kamilla Marie Speht; Willach, Sarah; Antoniou, Maria

    2012-01-01

    This study investigated the formation and predicted toxicity of different groups of disinfection byproducts (DBPs) from human exudates in relation to chlorination of pool water at different pH values. Specifically, the formation of the DBP groups trihalomethanes (THMs), haloacetic acids (HAAs......), haloacetonitriles (HANs) and trichloramine (NCl3), resulting from the chlorination of body fluid analog, were investigated at 6.0 ≤ pH ≤ 8.0. Either the initial concentration of active chorine or free chlorine was kept constant in the tested pH range. THM formation was reduced by decreasing pH but HAN, and NCl3...... formation was investigated and found to follow the same pH dependency as without bromide present, with the overall DBP formation increasing, except for HAAs. Estimation of genotoxicity and cytotoxicity of the chlorinated human exudates showed that among the quantified DBP groups, HAN formation were...

  20. The full-scale Emplacement (FE) Experiment at the Mont Terri URL

    International Nuclear Information System (INIS)

    Mueller, H.R.; Weber, H.P.; Koehler, S.; Vogt, T.; Vietor, T.

    2012-01-01

    Document available in extended abstract form only. The Full-Scale Emplacement (FE) Experiment at the Mont Terri underground research laboratory (URL) is a full-scale heater test in a clay-rich formation. It simulates the construction, waste emplacement and backfilling of a spent fuel (SF) / vitrified high-level waste (HLW) repository tunnel as realistically as possible. The entire experiment implementation as well as the post-closure THM(C) evolution will be monitored using several hundred sensors. These are distributed in the host rock in the near- and far-field, the tunnel lining, the engineered barrier system and on the heaters. The aim of this experiment is to investigate HLW repository-induced thermo-hydro-mechanical (THM) coupled effects on the host rock and the validation of existing coupled THM models. A further aim is the verification of the technical feasibility of constructing a 50 m repository section at full scale with all relevant components using standard industrial equipment. Finally, the experiment will demonstrate the canister and buffer emplacement procedures for underground conditions based on the Swiss disposal concept. Experimental layout The FE experiment is based on the Swiss disposal concept for SF / HLW. The 50 m long test gallery, at the end of the former MB test tunnel in the Mont Terri URL, will be realised with a diameter of approx. 3 m. In the experiment gallery, 3 heaters with dimensions similar to those of waste canisters will be emplaced on top of abutments built of bentonite blocks. The remaining space will be backfilled with compacted bentonite pellets. The experiment will be sealed off towards the start niche with a concrete plug holding the buffer in place and reducing air and water fluxes. The first scoping calculations and design modelling for the 'far-field' instrumentation have been completed; these works have been carried out using CodeBRIGHT and the multiphase flow simulator TOUGH2. With an initial heat output of 1500 W

  1. Comparison of Spot and Time Weighted Averaging (TWA Sampling with SPME-GC/MS Methods for Trihalomethane (THM Analysis

    Directory of Open Access Journals (Sweden)

    Don-Roger Parkinson

    2016-02-01

    Full Text Available Water samples were collected and analyzed for conductivity, pH, temperature and trihalomethanes (THMs during the fall of 2014 at two monitored municipal drinking water source ponds. Both spot (or grab and time weighted average (TWA sampling methods were assessed over the same two day sampling time period. For spot sampling, replicate samples were taken at each site and analyzed within 12 h of sampling by both Headspace (HS- and direct (DI- solid phase microextraction (SPME sampling/extraction methods followed by Gas Chromatography/Mass Spectrometry (GC/MS. For TWA, a two day passive on-site TWA sampling was carried out at the same sampling points in the ponds. All SPME sampling methods undertaken used a 65-µm PDMS/DVB SPME fiber, which was found optimal for THM sampling. Sampling conditions were optimized in the laboratory using calibration standards of chloroform, bromoform, bromodichloromethane, dibromochloromethane, 1,2-dibromoethane and 1,2-dichloroethane, prepared in aqueous solutions from analytical grade samples. Calibration curves for all methods with R2 values ranging from 0.985–0.998 (N = 5 over the quantitation linear range of 3–800 ppb were achieved. The different sampling methods were compared for quantification of the water samples, and results showed that DI- and TWA- sampling methods gave better data and analytical metrics. Addition of 10% wt./vol. of (NH42SO4 salt to the sampling vial was found to aid extraction of THMs by increasing GC peaks areas by about 10%, which resulted in lower detection limits for all techniques studied. However, for on-site TWA analysis of THMs in natural waters, the calibration standard(s ionic strength conditions, must be carefully matched to natural water conditions to properly quantitate THM concentrations. The data obtained from the TWA method may better reflect actual natural water conditions.

  2. Glucose Oxidase Immobilization on TMAH-Modified Bentonite

    Directory of Open Access Journals (Sweden)

    Ruth Chrisnasari

    2015-03-01

    Full Text Available The influence of bentonite modification by tetramethyl ammonium hydroxide (TMAH on its capability to immobilize glucose oxidase (GOX was studied. Modification of bentonite was conducted by the adding of 0-5% (v/v TMAH. The observed results show that the different concentrations of TMAH affect the percentage of immobilized enzyme. The results of this study show that the best concentration of TMAH is 5% (v/v which can immobilize up to 84.71% of GOX. X-ray diffraction (XRD and Fourier Transforms Infrared Spectroscopy (FTIR studies have been carried out to observe the structural changes in bentonite due to TMAH modification. The obtained immobilized GOX show the optimum catalytic activity on reaction temperature of 40-50 °C and pH of 7. The immobilized GOX kinetics at the optimum conditions determined the Km and Vmax value to be 4.96x10-2 mM and 4.99x10-3 mM.min-1 respectively. In addition, the immobilized GOX on TMAH-modified bentonite is stable enough so it could be re-used six times before its activity decreased by 39.44%.

  3. Magnesium incorporated bentonite clay for defluoridation of drinking water.

    Science.gov (United States)

    Thakre, Dilip; Rayalu, Sadhana; Kawade, Raju; Meshram, Siddharth; Subrt, J; Labhsetwar, Nitin

    2010-08-15

    Low cost bentonite clay was chemically modified using magnesium chloride in order to enhance its fluoride removal capacity. The magnesium incorporated bentonite (MB) was characterized by using XRD and SEM techniques. Batch adsorption experiments were conducted to study and optimize various operational parameters such as adsorbent dose, contact time, pH, effect of co-ions and initial fluoride concentration. It was observed that the MB works effectively over wide range of pH and showed a maximum fluoride removal capacity of 2.26 mgg(-1) at an initial fluoride concentration of 5 mg L(-1), which is much better than the unmodified bentonite. The experimental data fitted well into Langmuir adsorption isotherm and follows pseudo-first-order kinetics. Thermodynamic study suggests that fluoride adsorption on MB is reasonably spontaneous and an endothermic process. MB showed significantly high fluoride removal in synthetic water as compared to field water. Desorption study of MB suggest that almost all the loaded fluoride was desorbed ( approximately 97%) using 1M NaOH solution however maximum fluoride removal decreases from 95.47 to 73 (%) after regeneration. From the experimental results, it may be inferred that chemical modification enhances the fluoride removal efficiency of bentonite and it works as an effective adsorbent for defluoridation of water. Copyright 2010 Elsevier B.V. All rights reserved.

  4. Magnesium incorporated bentonite clay for defluoridation of drinking water

    International Nuclear Information System (INIS)

    Thakre, Dilip; Rayalu, Sadhana; Kawade, Raju; Meshram, Siddharth; Subrt, J.; Labhsetwar, Nitin

    2010-01-01

    Low cost bentonite clay was chemically modified using magnesium chloride in order to enhance its fluoride removal capacity. The magnesium incorporated bentonite (MB) was characterized by using XRD and SEM techniques. Batch adsorption experiments were conducted to study and optimize various operational parameters such as adsorbent dose, contact time, pH, effect of co-ions and initial fluoride concentration. It was observed that the MB works effectively over wide range of pH and showed a maximum fluoride removal capacity of 2.26 mg g -1 at an initial fluoride concentration of 5 mg L -1 , which is much better than the unmodified bentonite. The experimental data fitted well into Langmuir adsorption isotherm and follows pseudo-first-order kinetics. Thermodynamic study suggests that fluoride adsorption on MB is reasonably spontaneous and an endothermic process. MB showed significantly high fluoride removal in synthetic water as compared to field water. Desorption study of MB suggest that almost all the loaded fluoride was desorbed (∼97%) using 1 M NaOH solution however maximum fluoride removal decreases from 95.47 to 73 (%) after regeneration. From the experimental results, it may be inferred that chemical modification enhances the fluoride removal efficiency of bentonite and it works as an effective adsorbent for defluoridation of water.

  5. The biological costs of not reclaiming bentonite mine spoils

    Science.gov (United States)

    Carolyn Hull Sieg; Daniel W. Uresk; Richard M. Hansen

    1982-01-01

    Bentonite clay has been mined in the northern Great Plains for more than 80 years. Until the late 1960's, mine spoil materials were left in steep piles and no effort was made to restore biological productivity to these disturbed sites. As a result, unreclaimed spoils are barren and eroded. The biological costs of not reclaiming these spoils are examined in this...

  6. Mineralogical behaviour of bentonites in open and closed systems

    International Nuclear Information System (INIS)

    Herbert, H.J.; Kasbohm, J.

    2004-01-01

    Mineralogical and chemical changes of bentonites were investigated in a natural analogue study and in laboratory experiments. As a working hypothesis we assumed that in geological, i.e. open systems, bentonites may be penetrated over geological time scales by larger water volumes than high compacted bentonites used as technical barriers in repositories in salt formations. Under this assumption open geological systems are characterised by low solid/liquid ratios and closed repository systems by high solid/liquid ratios. Consequently in laboratory experiments the mineralogical changes were investigated under different solid/liquid ratios and compared with results of a natural analogue study. In the natural analogue study in deep boreholes in the East Slovakian Basin the expandability of montmorillonite and the degree of transformation in illite-smectite (IS) mixed layer structures was found to be dependent not only on depth and temperature but also on the salinity of the pore waters. In this open geological system with a comparatively low solid/liquid ratio the observed changes in the montmorillonite were significantly different than those observed in the laboratory study on compacted MX-80 bentonite. (authors)

  7. Behaviour of humic-bentonite aggregates in diluted suspensions ...

    African Journals Online (AJOL)

    Formation and disaggregation of micron-size aggregates in a diluted suspension made up of HSs and bentonite (B) were studied by tracing distribution of aggregate sizes and their counts in freshly prepared and aged suspensions, and at high (10 000) and low (1.0) [HS]/[B] ratios. Diluted HSB suspensions are unstable ...

  8. Magnesium incorporated bentonite clay for defluoridation of drinking water

    Czech Academy of Sciences Publication Activity Database

    Thakre, D.; Rayalu, S.; Kawade, R.; Meshram, S.; Šubrt, Jan; Labhsetwar, N.

    2010-01-01

    Roč. 180, 1-3 (2010), s. 122-130 ISSN 0304-3894 Institutional research plan: CEZ:AV0Z40320502 Keywords : adsorption * bentonite * fluoride removal Subject RIV: CA - Inorganic Chemistry Impact factor: 3.723, year: 2010

  9. Synthesis of MCM-41 nanomaterial from Algerian bentonite ...

    African Journals Online (AJOL)

    Mesoporous materials of the MCM-41 type were synthesized from Algerian bentonite as an aluminosilicate source without the addition of pure silica and aluminum reagents. The samples were synthesized under hydrothermal condition using cetyltrimithylammonium bromide (CTAB) as surfactant. The influence of initial ...

  10. Vitrification and neomineralisation of bentonitic and kaolinitic clays ...

    African Journals Online (AJOL)

    ... metamorphic and/or igneous rocks. Resultant fired mineral phases depicted mineral compositions of ceramic bodies, and the study suggested that these clays could be gainfully utilized in the making of ceramic wares, subject to selected beneficiation processes. Keywords: kaolin, bentonite, vitrification, neomineralization, ...

  11. Diffusion of anions and cations in compacted sodium bentonite

    International Nuclear Information System (INIS)

    Muurinen, A.

    1994-02-01

    The thesis presents the results of studies on the diffusion mechanisms of anions and cations in compacted sodium bentonite, which is planned to be used as a buffer material in nuclear waste disposal in Finland. The diffusivities and sorption factors were determined by tracer experiments. The pore volume accessible to chloride, here defined as effective porosity, was determined as a function of bentonite density and electrolyte concentration in water, and the Stern-Gouy double-layer model was used to explain the observed anion exclusion. The sorption of Cs + and Sr 2+ was studied in loose and compacted bentonite samples as a function of the electrolyte concentration in solution. In order to obtain evidence of the diffusion of exchangeable cations, defined as surface diffusion, the diffusivities of Cs + and Sr 2+ in compacted bentonite were studied as a function of the sorption factor, which was varied by electrolyte concentration in solution. The measurements were performed both by a non-steady state method and by a through-diffusion method. (89 refs., 35 fig., 4 tab.)

  12. Effects of polyethyleneimine adsorption on rheology of bentonite ...

    Indian Academy of Sciences (India)

    2016-08-26

    Aug 26, 2016 ... The influence of the cationic polymer, polyethyleneimine polymer (PEI) on the flow behaviour of bentonite suspensions (2%, w/w), was studied. XRD, zeta potential and adsorption studies were done together with rheological measurements. The addition of PEI at concentration ranges of 10-5–4.5 g/l and ...

  13. characterization of geotechnical properties of lateritic soil-bentonite

    African Journals Online (AJOL)

    2013-03-01

    Mar 1, 2013 ... cilities should ensure minimum fluid flow through or into the repository ... were evaluated using the rigid wall permeameter un- der falling ... cell pressure [22]. 3. Results .... them to retain a portion of water (double layer water) that may ... water in the pore space. ... The effect of bentonite content on volumetric.

  14. Performance of Mn2+-modified Bentonite Clay for the Removal

    African Journals Online (AJOL)

    NICOLAAS

    Clay minerals are promising materials for defluoridation of ... edge of the bentonite sheet. ... surface area analyzer (Autosorb-iQ & Quadrasorb SI, USA). .... used to describe chemisorption, as well as cation exchange reac- tions.14 t q. 1. K q. 1.

  15. Bentonite Modification with Manganese Oxides and Its Characterization

    Czech Academy of Sciences Publication Activity Database

    Dolinská, S.; Schütz, T.; Znamenáčková, I.; Lovás, M.; Vaculíková, Lenka

    2015-01-01

    Roč. 35, č. 1 (2015), s. 213-218 ISSN 1640-4920 Institutional support: RVO:68145535 Keywords : bentonite * natrification * manganese oxide Subject RIV: CB - Analytical Chemistry, Separation http://www.potopk.com.pl/ Full _text/2015_full/IM%202-2015-a35.pdf

  16. The removal of chromium from wastewaters by activated bentonite

    International Nuclear Information System (INIS)

    Mellah, A.; Chegrouche, S.; Ait Ghezala, H.; Douar, L.

    1994-12-01

    The adsorption of chromium onto activated bentonite has been investigated. Adsorption isotherms were analysed to obtain the Langmuir and freundlich constants. The operating parameters (i.e pH, contact time, solid/liquid ratio, temperatureand initial chromium concentration) influenced the rate of adsorption have been studied

  17. Thermal loading of bentonite. Impact on hydromechanics and permeability

    Energy Technology Data Exchange (ETDEWEB)

    Zihms, Stephanie G.; Harrington, Jon [British Geological Survey, Nickerhill Keyworth (United Kingdom)

    2015-07-01

    Due to its favorable properties, in particular, low permeability and swelling capacity, bentonite has been favored as an engineered barrier and backfill material for the geological storage of radioactive waste. To ensure safe long-term performance it is important to understand any changes in these properties when the material is subject to heat emitting waste. As such, this study will investigate the hydro-mechanical response of bentonite under multi-step thermal loading subject to a constant volume boundary condition. The experimental set up allows continuous measurements of hydraulic and mechanical response during each phase of the thermal cycle. The constant volume cell was placed inside an oven and connected to a hydraulic system with the water reservoir located externally. A pressure gradient of 4 MPa was placed across the sample for the duration of the test in order to map the evolution of permeability. After initial hydration of the bentonite, in this case signified by reaching the asymptote in total stress, the temperature was raised in 20 C increments from 20 to 80 C followed by a final 10 C step to reach 90 C. Each temperature was held constant for at least 7-10 days to allow the stresses and hydraulic transients to equilibrate. This data set will provide an insight into the hydromechanical behavior of the bentonite and the evolution of its permeability when exposed to elevated temperatures.

  18. DEPOSITS AND MINING POTENTIAL OF BENTONITE IN CROATIA

    Directory of Open Access Journals (Sweden)

    Mario Klanfar

    2012-07-01

    Full Text Available Bentonite is one of the materials that is planed to be used for buffering and backfilling in spent nuclear fuel repositories, within deep crystalline rock. There are several locations in Croatia that bentonite deposits and occurrences are found on. Some were exploited in past, and others were more or less explored. This paper presents overview of bentonite deposits, basic properties and potential resources, and mining practices in Croatia. Largest exploited deposits are found in area of Poljanska luka, Gornja Jelenska and Bednja. Surface and underground methods (drift and fill, sublevel caving were used during exploitation. In the area of Svilaja and Lika are found potentially valuable deposits that were never exploited. Montmorilonite content ranges form 20-50% to 57-89%. Most deposits contain bentonite beds with thickness 0,4-1,6 m, and have plunge 10°-30°. Few exceptions are nearly horizontal and thick more than 5 m and even 12 m. One is declined at 70° and up to 40m thick. Proven reserves are about 2,3 Mt with some level of uncertainty. Average production per mine during exploitation period can be assumed to be several thousands t/y.

  19. Temperature effect on the behaviour of engineered clay barriers

    International Nuclear Information System (INIS)

    Tang, A.M.

    2005-11-01

    The present work deals with the thermo-hydro-mechanical behaviour of compacted swelling clay used for engineered barriers in high-level radioactive repositories. The MX80 bentonite was chosen for this work. Firstly, an experimental work on the thermal conductivity of the compacted bentonite was performed. The results evidenced the effects of dry density, water content, volumetric fraction of soil components, microstructure, and mineralogy. This experimental work gave rise to the proposition of a theoretical model for estimate the thermal conductivity of compacted bentonites. Secondly, after a calibration of suction generated by saturated saline solution in function of temperature, water retention curves were determined at different temperatures. The experimental results showed a decrease of the water retention capacity of soil after heating. A simple model based on the interfacial tension air-water was formulated to simulate this effect. Thirdly, a new isotropic cell enabling a simultaneous control of suction, temperature and mechanical stress was developed. With this new cell, an experimental work on the thermo-mechanical behaviour of the unsaturated compacted bentonite was performed. Finally, a constitutive model was developed for simulate the thermo-hydro-mechanical behaviours obtained experimentally. (author)

  20. Temperature effect on the behaviour of engineered clay barriers; Effet de la temperature sur le comportement des barrieres de confinement

    Energy Technology Data Exchange (ETDEWEB)

    Tang, A.M

    2005-11-15

    The present work deals with the thermo-hydro-mechanical behaviour of compacted swelling clay used for engineered barriers in high-level radioactive repositories. The MX80 bentonite was chosen for this work. Firstly, an experimental work on the thermal conductivity of the compacted bentonite was performed. The results evidenced the effects of dry density, water content, volumetric fraction of soil components, microstructure, and mineralogy. This experimental work gave rise to the proposition of a theoretical model for estimate the thermal conductivity of compacted bentonites. Secondly, after a calibration of suction generated by saturated saline solution in function of temperature, water retention curves were determined at different temperatures. The experimental results showed a decrease of the water retention capacity of soil after heating. A simple model based on the interfacial tension air-water was formulated to simulate this effect. Thirdly, a new isotropic cell enabling a simultaneous control of suction, temperature and mechanical stress was developed. With this new cell, an experimental work on the thermo-mechanical behaviour of the unsaturated compacted bentonite was performed. Finally, a constitutive model was developed for simulate the thermo-hydro-mechanical behaviours obtained experimentally. (author)

  1. Structure and forces in bentonite MX-80

    Energy Technology Data Exchange (ETDEWEB)

    Joensson, Bo; Aakesson, Torbjoern; Joensson, Bengt; Meehdi, Segad; Janiak, John; Wallenberg, Reine (Theoretical Chemistry, Chemical Center, Lund Univ., Lund (Sweden))

    2009-03-15

    Wyoming bentonite (MX-80) and its ion exchanged forms, Na and Ca montmorillonite, have been studied experimentally and theoretically. A variety of experimental techniques have been used in order to gain insight into the structural conditions in dry clay as well as clay in equilibrium with a bulk solution of given ionic composition. The main objective has been the swelling behaviour and osmotic pressure of montmorillonite clay when the bulk solution contains a mix of monovalent sodium and divalent calcium ions. For a clay system in equilibrium with pure water, Monte Carlo simulations predict a large swelling when the clay counterions are monovalent, while in presence of divalent counterions a limited swelling is predicted with an aqueous layer between the clay lamellaes of about 1 nm. This latter result is in excellent agreement with small angle x-ray scattering data, but in disagreement with dialysis experiments, which gives a significantly larger swelling for Ca montmorillonite in pure water. Obviously, there is one lamellar swelling and a second 'extra-lamellar' swelling, which could be the result of a phase separation in the clay. Montmorillonite in contact with a salt reservoir with both Na+ and Ca2+ counterions will only show a modest swelling unless the sodium concentration in the bulk is several orders of magnitude larger than the calcium concentration. The limited swelling of clay in presence of divalent counterions is a consequence of ion-ion correlations, which reduce the entropic repulsion as well as give rise to an attractive component in the total osmotic pressure. Ion-ion correlations also favour divalent counterions in a situation where we have a competition with monovalent ones. A more fundamental result of ion-ion correlations is that the osmotic pressure as a function of clay sheet separation becomes nonmonotonic, which indicates the possibility of a phase separation into a concentrated and a dilute clay phase. This phenomenon could

  2. Gas migration mechanism of saturated dense bentonite and its modeling

    International Nuclear Information System (INIS)

    Tanaka, Yukihisa; Hironaga, Michihiko; Kudo, Koji

    2007-01-01

    In the current concept of repository for nuclear waste disposal, compacted bentonite will be used as an engineered barrier mainly for inhibiting migration of radioactive nuclides. Hydrogen gas can be generated inside the engineered barrier by anaerobic corrosion of metals used for containers, etc. If the gas generation rate exceeds the diffusion rate of gas molecules inside of the engineered barrier, gas will accumulate in the void space inside of the engineered barrier until its pressure becomes large enough for it to enter the bentonite as a discrete gaseous phase. It is expected to be not easy for gas to entering into the bentonite as a discrete gaseous phase because the pore of compacted bentonite is so minute. Therefore it is necessary to investigate the following subjects: a) Effect of the accumulated gas pressure on surrounding objects such as concrete lining, rock mass. b) Effect of gas breakthrough on the barrier function of bentonite. c) Revealing and modeling gas migration mechanism for overcoming the scale effects in laboratory specimen test. Therefore in this study, gas migration tests for compacted and saturated bentonite to investigate and to model the mechanism of gas migration phenomenon. Firstly, the following conclusions were obtained through by the results of the gas migration tests which are conducted in this study: 1) Bubbles appear in the semitransparent drainage tube at first when the total gas is equal to the initial total axial stress or somewhat smaller. By increasing the gas pressure more, breakthrough of gas migration, which is defined as a sudden increase of amount of emission gas, occurred. When the total gas pressure exceeds the initial total axial stress, the total axial stress is always equal to the total gas pressure because specimens shrink in the axial direction with causing the clearance between the end of the specimen and porous metal. 2) Effective gas conductivity after breakthrough of gas migration is times larger than that

  3. Response surface optimisation for activation of bentonite with microwave irradiation

    Directory of Open Access Journals (Sweden)

    Rožić Ljiljana S.

    2011-01-01

    Full Text Available In this study, the statistical design of the experimental method was applied on the acid activation process of bentonite with microwave irradiation. The influence of activation parameters (time, acid normality and microwave heating power on the selected process response of the activated bentonite samples was studied. The specific surface area was chosen for the process response, because the chemical, surface and structural properties of the activated clay determine and limit its potential applications. The relationship of various process parameters with the specific surface area of bentonite was examined. A mathematical model was developed using a second-order response surface model (RSM with a central composite design incorporating the above mentioned process parameters. The mathematical model developed helped in predicting the variation in specific surface area of activated bentonite with time (5-21 min, acid normality (2-7 N and microwave heating power (63-172 W. The calculated regression models were found to be statistically significant at the required range and presented little variability. Furthermore, high values of R2 (0.957 and R2 (adjusted (0.914 indicate a high dependence and correlation between the observed and the predicted values of the response. These high values also indicate that about 96% of the result of the total variation can be explained by this model. In addition, the model shows that increasing the time and acid normality improves the textural properties of bentonites, resulting in increased specific surface area. This model also can be useful for setting an optimum value of the activation parameters for achieving the maximum specific surface area. An optimum specific surface area of 142 m2g-1 was achieved with an acid normality of 5.2 N, activation time of 7.38 min and microwave power of 117 W. Acid activation of bentonite was found to occur faster with microwave irradiation than with conventional heating. Microwave

  4. Alteration of bentonite when contacted with supercritical CO2

    Science.gov (United States)

    Jinseok, K.; Jo, H. Y.; Yun, S. T.

    2014-12-01

    Deep saline formations overlaid by impermeable caprocks with a high sealing capacity are attractive CO2 storage reservoirs. Shales, which consist of mainly clay minerals, are potential caprocks for the CO2 storage reservoirs. The properties of clay minerals in shales may affect the sealing capacity of shales. In this study, changes in clay minerals' properties when contacted with supercritical (SC) CO2 at various conditions were investigated. Bentonite, whichis composed of primarily montmorillonite, was used as the clay material in this study. Batch reactor tests on wet bentonite samples in the presence of SC CO2 with or without aqueous phases were conducted at high pressure (12 MPa) and moderate temperature (50 oC) conditions for a week. Results show that the bentonite samples obtained from the tests with SC CO2 had less change in porosity than those obtained from the tests without SC CO2 (vacuum-drying) at a given reaction time, indicating that the bentonite samples dried in the presence of SC CO2 maintained their structure. These results suggest that CO2 molecules can diffuse into interlayer of montmorillonite, which is a primary mineral of bentonite, and form a single CO2 molecule layer or double CO2 molecule layers. The CO2 molecules can displace water molecules in the interlayer, resulting in maintaining the interlayer spacing when dehydration occurs. Noticeable changes in reacted bentonite samples obtained from the tests with an aqueous phase (NaCl, CaCl2, or sea water) are decreases in the fraction of plagioclase and pyrite and formation of carbonate minerals (i.e., calcite and dolomite) and halite. In addition, no significant exchanges of Na or Ca on the exchangeable complex of the montmorillonite in the presence of SC CO2 occurred, resulting in no significant changes in the swelling capacity of bentonite samples after reacting with SC CO2 in the presence of aqueous phases. These results might be attributed by the CO2 molecule layer, which prevents

  5. Activation of a Ca-bentonite as buffer material

    Science.gov (United States)

    Huang, Wei-Hsing; Chen, Wen-Chuan

    2016-04-01

    Swelling behavior is an important criterion in achieving the low-permeability sealing function of buffer material. A potential buffer material may be used for radioactive waste repository in Taiwan is a locally available clayey material known as Zhisin clay, which has been identified as a Ca-bentonite. Due to its Ca-based origin, Zhisin was found to exhibit swelling capacity much lower than that of Na-bentonite. To enhance the swelling potential of Zhisin clay, a cation exchange process by addition of Na2CO3 powder was introduced in this paper. The addition of Na2CO3 reagent to Zhisin clay, in a liquid phase, caused the precipitation of CaCO3 and thereby induced a replacement of Ca2+ ions by Na+ ions on the surface of bentonite. Characterization test conducted on Zhisin clay includes chemical analysis, cation exchange capacity, X-ray diffraction, and thermogravimetry (TG). Free-swelling test apparatus was developed according to International Society of Rock Mechanics recommendations. A series of free-swelling tests were conducted on untreated and activated specimens to characterize the effect of activation on the swelling capacity of Zhisin clay. Efforts were made to determine an optimum dosage for the activation, and to evaluate the aging effect. Also, the activated material was evaluated for its stability in various hydrothermal conditions for potential applications as buffer material in a repository. Experimental results show that Na2CO3-activated Zhisin clay is superior in swelling potential to untreated Zhisin clay. Also, there exists an optimum amount of activator in terms of improvements in the swelling capacity. A distinct time-swell relationship was discovered for activated Zhisin clay. The corresponding mechanism refers to exchange of cations and breakdown of quasi-crystal, which results in ion exchange hysteresis of Ca-bentonite. Due to the ion exchange hysteresis, activated bentonite shows a post-rise time-swell relationship different than the sigmoid

  6. DECOVALEX II PROJECT Technical Report - Task 2C

    Energy Technology Data Exchange (ETDEWEB)

    Jing, L.; Stephansson, O. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Civil and Environmental Engineering; Boergesson, L. [Clay Technology AB, IDEON Research Center, Lund (Sweden); Chijimatzu, M. [Japan Nuclear Cycle Development Inst., Ibaraki (Japan). Waste Management and Fuel Cycle Research Center; Kautsky, F. [Swedish Nuclear Power Inspectorate (SKI), Stockholm (Sweden); Tsang, C.F. [Lawrence Berkeley National Laboratory, Berkeley, CA (United States). Earth Science Div.

    1999-05-01

    , simulation and results of Task 2C for predicting the fully coupled thermo-hydro-mechanical behaviour of the complete heater-buffer-rock system at the test site, especially the interactions between the different components and interfaces (heater-buffer, buffer-rock, solid-water) and buffer property determination. The problem was treated as a near-field problem, like Task 2A and 2B models. The same four research teams studied this case.

  7. Cement/bentonite interaction. Results from 16 month laboratory tests

    Energy Technology Data Exchange (ETDEWEB)

    Karnland, O. [Clay Technology AB, Lund (Sweden)

    1997-12-01

    The work concerns possible bentonite clay mineral alteration in constructions with bentonite in close contact with cement, and the effect of such changes on bentonite buffer properties. The investigation comprises a 16 months laboratory test series with hydrothermal cell tests, percolation tests and diffusion tests. MX-80 Wyoming bentonite was used in all tests. Two types of artificial cement pore water solutions were used in the percolation and diffusion tests. The swelling pressure and the hydraulic conductivity were measured continuously in the percolation tests. After termination, the clay was analyzed with respect to changes in element distribution, mineralogy and shear strength. The water solutions were analyzed with respect to pH, cations and major anions. The results concerning chemical and mineralogical changes are in summary: Ion exchange in the montmorillonite until equilibrium with cement pore-water ions was reached; Increase in cation exchange capacity; Dissolution of original cristobalite; Increase in quartz content; Minor increase in illite content; Minor formation of chlorite; Formation of CSH(I); Wash away of CSH-gel into surrounding water. A large decrease in swelling pressure and a moderate increase in hydraulic conductivity were recorded in the samples percolated by SULFACEM pore-water solution. The mineralogical alterations only concerned a minor part of the total bentonite mass and the changes in physical properties were therefore most likely due to the replacement of the original charge balancing cation by cement pore-water cations. Comparisons between the current test result and results from 4 month tests indicate that the rates of illite and chlorite formation were reduced during the tests. The presence of zeolites in the clay could not be ensured. However, the discovery of CSH material is important since CSH is expected to precede the formation of zeolites 5 refs, 48 figs, 11 tabs

  8. Thermodynamic understanding on swelling pressure of bentonite buffer

    International Nuclear Information System (INIS)

    Sato, Haruo

    2007-01-01

    Smectite (montmorillonite) is a major clay mineral constituent of the bentonite buffer and backfilling materials to be used for the geological disposal of high-level radioactive waste. Swelling pressure of the bentonite buffer occurring in the permeation process of moisture was estimated based on thermodynamic theory and the thermodynamic data of interlayer water in smectite in this study. The relative partial molar Gibbs free energies (ΔG H2O ) of water on the smectite surface were measured as a function of water content (0-83%) in a dry density range of 0.6-0.9 Mg/m 3 . Purified Na-smectite of which interlayer cations were exchanged with Na + ions and soluble salts were completely removed, was used in this study. Obtained ΔG H2O decreased with an increase of water content in the range of water content lower than about 40%, and similar trends were obtained to data of Kunipia-F bentonite (Na-bentonite) of which smectite content was approximately 100 wt.%. From the specific surface area of smectite (ca. 800 m 2 /g) and the correlation between ΔG H2O and water content, water affected from the surface of smectite was estimated to be up to approximately 2 water layers. Swelling pressure versus smectite partial density (montmorillonite partial density) was estimated based on ΔG H2O from the chemical potential balance of water in equilibrium between the free water and moisturized smectite, and compared to data measured for various kinds of bentonites of which smectite contents were respectively different. The estimated swelling pressures were in good agreement with the measured data. (author)

  9. Study of cesium and strontium adsorption on slovak bentonite

    International Nuclear Information System (INIS)

    Galambos, M.

    2010-01-01

    Bentonite is a natural clay and one of the most promising candidates for use as a buffer material in the geological disposal systems for high-level radioactive waste and spent nuclear fuel. It is intended to isolate metal canisters with highly radioactive waste products from the surrounding rocks because of its ability to retard the movement of radionuclides by adsorption. Slovak Republic avails of many significant deposits of bentonite. Adsorption of Cs and Sr on five Slovak bentonite of deposits (Jelsovy potok, Kopernica, Lieskovec, Lastovce and Dolna Ves) and montmorillonite K10 (Sigma-Aldrich) has been studied with the using batch of radiometric techniques. Natural, irradiated and natrified samples, in three different kinds of grain size: 15, 45 and 250 μm have been used in the experiments. The adsorptions of Cs and Sr on bentonite under various experimental conditions, such as contact time, adsorbent and adsorbate concentrations, pH after adsorption and effect of pH change, chemical modification, competitive ions and organic agents on the adsorption have been studied. The K d have been determined for adsorbent-Cs/Sr solution system as a function of contact time and adsorbate and adsorbent concentration. The data have been interpreted in terms of Langmuir isotherm. The adsorption of Cs and Sr has increased with increasing metal concentrations. Adsorption of Cs and Sr has been suppressed by presence of organic agents; and of bivalent cations more than univalent cations. By adsorption on natrified samples colloidal particles and pH value increase have been formed. Adsorption experiments carried out show that the most suitable materials intended for use as barriers surrounding a canister of spent nuclear fuel are bentonite of the Jelsovy potok and Kopernica deposits. (author)

  10. Polyaniline (PANI) modified bentonite by plasma technique for U(VI) removal from aqueous solution

    International Nuclear Information System (INIS)

    Liu, Xinghao; Cheng, Cheng; Xiao, Chengjian; Shao, Dadong; Xu, Zimu; Wang, Jiaquan; Hu, Shuheng; Li, Xiaolong; Wang, Weijuan

    2017-01-01

    Highlights: • PANI/bentonie can be synthesized by simple plasma technique. • PANI/bentonie has an excellent adsorption capacity for trace uranium in solution. • U(VI) adsorption on PANI/bentonite is a spontaneous and endothermic process. - Abstract: Polyaniline (PANI) modified bentonite (PANI/bentonie) was synthesized by plasma induced polymerization of aniline on bentonite surface, and applied to uptake of uranium(VI) ions from aqueous solution. The as-synthesized PANI/bentonie was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). Batch adsorption technique was utilized to investigate the adsorption of U(VI) on bentonite and PANI/bentonite. The adsorption of U(VI) (10 mg/L) on PANI/bentonite surface is fairly depend on solution pH, ionic strength, and temperature in solution. The modified PANI on PANI/bentonite surface significantly enhances its adsorption capability for U(VI). The presence of humic acid (HA) can sound enhance U(VI) adsorption on PANI/bentonite at pH 6.5. According to the thermodynamic parameters, the adsorption of U(VI) on PANI/bentonite surface is a spontaneous and endothermic process. The results highlight the application of PANI/bentonite composites as candidate material for the uptake of trace U(VI) from aqueous solution.

  11. Polyaniline (PANI) modified bentonite by plasma technique for U(VI) removal from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xinghao [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Intelligent Manufacturing Technology Research Institute, Hefei University of Technology, Hefei 230088 (China); Cheng, Cheng [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Xiao, Chengjian, E-mail: xiaocj@caep.cn [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Shao, Dadong, E-mail: shaodadong@126.com [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Xu, Zimu, E-mail: xzm@mail.ustc.edu.cn [Intelligent Manufacturing Technology Research Institute, Hefei University of Technology, Hefei 230088 (China); Wang, Jiaquan; Hu, Shuheng [Intelligent Manufacturing Technology Research Institute, Hefei University of Technology, Hefei 230088 (China); Li, Xiaolong; Wang, Weijuan [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China)

    2017-07-31

    Highlights: • PANI/bentonie can be synthesized by simple plasma technique. • PANI/bentonie has an excellent adsorption capacity for trace uranium in solution. • U(VI) adsorption on PANI/bentonite is a spontaneous and endothermic process. - Abstract: Polyaniline (PANI) modified bentonite (PANI/bentonie) was synthesized by plasma induced polymerization of aniline on bentonite surface, and applied to uptake of uranium(VI) ions from aqueous solution. The as-synthesized PANI/bentonie was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). Batch adsorption technique was utilized to investigate the adsorption of U(VI) on bentonite and PANI/bentonite. The adsorption of U(VI) (10 mg/L) on PANI/bentonite surface is fairly depend on solution pH, ionic strength, and temperature in solution. The modified PANI on PANI/bentonite surface significantly enhances its adsorption capability for U(VI). The presence of humic acid (HA) can sound enhance U(VI) adsorption on PANI/bentonite at pH < 6.5 because of the strong complexation, and inhibits U(VI) adsorption at pH > 6.5. According to the thermodynamic parameters, the adsorption of U(VI) on PANI/bentonite surface is a spontaneous and endothermic process. The results highlight the application of PANI/bentonite composites as candidate material for the uptake of trace U(VI) from aqueous solution.

  12. Sequential use of bentonites and solar photocatalysis to treat winery wastewater.

    Science.gov (United States)

    Rodríguez, Eva; Márquez, Gracia; Carpintero, Juan Carlos; Beltrán, Fernando J; Alvarez, Pedro

    2008-12-24

    The sequential use of low-cost adsorbent bentonites and solar photocatalysis to treat winery wastewater has been studied. Three commercial sodium-bentonites (MB-M, MB-G, and MB-P) and one calcium-bentonite (Bengel) were characterized and used in this study. These clay materials were useful to totally remove turbidity (90-100%) and, to a lesser extent, color, polyphenols (PPh), and soluble chemical oxygen demand (CODS) from winery wastewater. Both surface area and cation exchange capacity (CEC) of bentonite had a positive impact on treatment efficiency. The effect of pH on turbidity removal by bentonites was studied in the 3.5-12 pH range. The bentonites were capable of greatly removing turbidity from winery wastewater at pH 3.5-5.5, but removal efficiency decreased with pH increase beyond this range. Settling characteristics (i.e., sludge volume index (SVI) and settling rate) of bentonites were also studied. Best settling properties were observed for bentonite doses around 0.5 g/L. The reuse of bentonite for winery wastewater treatment was found not to be advisable as the turbidity and PPh removal efficiencies decreased with successive uses. The resulting wastewater after bentonite treatment was exposed to solar radiation at oxic conditions in the presence of Fe(III) and Fe(III)/H2O2 catalysts. Significant reductions of COD, total organic carbon (TOC), and PPh were achieved by these solar photocatalytic processes.

  13. Effect of thermo-coupled processes on the behaviour of a clay barrier submitted to heating and hydration

    Directory of Open Access Journals (Sweden)

    Marcelo Sánchez

    2010-03-01

    Full Text Available The storage of high level radioactive waste is still an unresolved problem of the nuclear industry, being geological disposal the most favoured option and, naturally, the one requiring the strongest geo-mechanical input. Most conceptual designs for the deep geological disposal of nuclear waste envisage placing the canisters containing the waste in horizontal drifts or vertical boreholes. The empty space surrounding the canisters is filled by an engineered barrier often made up of compacted swelling clay. Inthebarrierandthenearfield,significantthermo-hydro-mechanical(THM phenomena take place that interact in a complex way. A good understanding of THM issues is, therefore, necessary to ensure a correct performance of engineered barriers and seals. The conditions of the bentonite in an engineered barrier for high-level radioactive waste disposal are being simulated in a mock-up heating test at almost scale, at the premises of CIEMAT in Madrid. The evolution of the main Thermo-Hydro-Mechanical (THM variables of this test are analysed in this paper by using a fully coupled THM formulation and the corresponding finite element code. Special emphasis has been placed on the study of the effect of thermo-osmotic flow in the hydration of the clay barrier at an advanced staged of the experiment.O armazenamento de rejeitos altamente radioativos é ainda um problema em aberto na área de engenharia nuclear sendo os sítios geológicos ainda a opção mais favorável e naturalmente aquela que demanda maior conhecimento na área de geomecânica. A maioria dos projetos conceituais de armazenamento do lixo nuclear objetiva a alocação de cilindros que contêm os rejeitos em poços verticais ou horizontais. O espaço vazio que circunda os cilindros é preenchido por uma barreirade engenharia na maioria dos casos composta por uma argila expansiva. Na barreira e na vizinhança fenômenos significativos de acoplamento termo-hidro-mecânico(THM tomam lugar e

  14. International conference on the performance of engineered barriers. Physical and chemical properties, behaviour and evolution. Short abstracts

    Energy Technology Data Exchange (ETDEWEB)

    Schaefers, Annika; Fahland, Sandra (eds.)

    2014-08-01

    The volume includes the abstracts of the papers presented at the international conference on the performance of engineered barrier systems, their physical and chemical properties, behavior and evolution. The papers cover the topics bentonite buffers, radioactive waste repository safety, geophysical and geochemical property monitoring, repository sealing materials, thermo-hydro-mechanical characterization, gas injection tests, hydration and heating tests, clay-iron interaction experiments, water retention behavior, thermal stability of materials, numerical modeling studies, long-term simulations, thermo-hydrologic phenomena, uncertainty and sensitivity studies, probabilistic assessments, preliminary safety analyses of Gorleben.

  15. Alteration behavior of bentonite barrier of radioactive waste disposal by alkaline solutions. Part 2. Effect of type of alkaline solution on permeability of compacted bentonite-sand mixture

    International Nuclear Information System (INIS)

    Yokoyama, Shingo; Nakamura, Kunihiko; Tanaka, Yukihisa; Hironaga, Michihiko

    2011-01-01

    Permeability tests were carried out using compacted bentonite-sand mixture with initial dry density of 1.55 Mg/m 3 and alkaline solutions at 50degC for about two years to estimate the alteration behavior and the change in the permeability. Bentonite-sand mixtures which contain bentonites of 15wt% were made using Na-bentonite or Ca-exchanged bentonite. 0.3M-NaOH solution with pH 13.3 and 5mM-Ca(OH) 2 solution with pH 12.0 were used to the permeability tests of Na-bentonite-sand mixture and of Ca-exchanged bentonite-sand mixture, respectively. In the case of the permeability test conducted using NaOH solution, montmorillonite and other associated minerals were dissolved, and consequently, the dry density and effective montmorillonite density of Na-bentonite-sand mixture were decreased. Furthermore, the mineralogical feature of montmorillonite was changed (i.e. beidellitization and an increase in the layer charge). The permeability of Na-bentonite-sand mixture was increased 5.6 times by the end of permeability test as a result of above alteration. In the case of the permeability test conducted using Ca(OH) 2 solution, montmorillonite and other associated minerals were dissolved, and calcium silicate hydrate (C-S-H) was precipitated. Consequently, the dry density of Ca-exchanged bentonite-sand mixture was increased, while the effective montmorillonite density was decreased. The mineralogical feature of montmorillonite was changed (i.e. beidellitization and an increase in the layer charge). The permeability of Ca-exchange bentonite-sand mixture was decreased by more than two orders of magnitude due to fill the pore of Ca-exchange bentonite-sand mixture by the precipitation of C-S-H. From above results, the type of alkaline solution affects the mineralogical alteration behavior of the compacted bentonite-sand mixture, and consequently, affects the changing trend of permeability. In conclusion, it is important not only to consider the dissolution of montmorillonite, but

  16. Application of HDTMA-intercalated bentonites in water waste treatment for U(VI) removal

    International Nuclear Information System (INIS)

    Krajnak, Adrian; Viglasova, Eva; Galambos, Michal; Krivosudsky, Lukas; Universitat Wien, Vienna

    2017-01-01

    Bentonite deposits in Slovakia are systematically investigated as potential adsorbents for wastewater and radioactive waste treatment applications. Herein, adsorption properties (isotherms, kinetics and thermodynamics) of raw and organo-modified bentonites towards uranium species in aqueous solutions were investigated. Organo-modified bentonites was prepared by practical and simple chemical modification method with hexadecyltrimethylammonium bromide (denoted as HDTMA-bentonites). The adsorption processes of U(VI) on HDTMA-bentonites were spontaneous and endothermic, and well simulated by pseudo-second-order model. The maximum adsorption capacity of U(VI) was calculated to be 31.45 mg/g at pH 8.5 and T = 298 K. Slovak bentonites Jelsovy potok and Kopernica, their natural and HDTMA-modified forms might be a promising sorbent for the treatment of U(VI) contaminants in aqueous solutions. (author)

  17. Progress of research on the influence of alkaline cation and alkaline solution on bentonite properties

    International Nuclear Information System (INIS)

    Ye Weimin; Zheng Zhenji; Chen Bao; Chen Yonggui

    2011-01-01

    Based on the previous laboratory studies and numerical simulation on bentonite in alkaline environments, the effects of alkaline cation and alkaline solution on mineral composition, microstructure, swelling capacity and hydraulic properties of bentonite are emphasized in this paper, temperature, pH values and concentration are discussed as main affecting factors. When bentonite is exposed to alkaline cation or alkaline solution, microstructure of bentonite will be changed due to the dissolution of montmorillonite and the formation of secondary minerals, which results in the decrease of swelling pressure. The amount of the reduction of swelling pressure depends on the concentration of alkaline solution. Temperature, polyvalent cation, salinity and concentration are the main factors affecting hydraulic properties of bentonite under alkaline conditions. Therefore, future research should focus on the mechanism of coupling effects of weak alkaline solutions on the mineral composition, microstructure, swelling capacity and hydraulic properties of bentonite under different temperatures and different pH values. (authors)

  18. Optimization of acid-activated bentonites on bleaching of cotton oil

    International Nuclear Information System (INIS)

    Lacin, O.; Sayan, E.; Kirali, E.G.

    2013-01-01

    Bentonites are commonly used adsorbent on bleaching cotton oil to produce edible oil products. Bleaching capacities of neutralized cotton oil were investigated with acid-activated Arguvan and Kursunlu bentonites. Two models for acid activation of the bentonites were developed by using a full factorial experimental design and central composite design. The parameters used to develop these models were contact time, solid to liquid ratio, acid concentration and moisture of bentonite. By using a constrained optimization program, the maximum bleaching capacities of neutralized cotton oil were determined as 99.99% and 48.5% for Arguvan and Kursunlu, respectively. Optimum results showed that Turkish bentonites (especially Arguvan bentonite) have high bleaching ability and they can be used efficiently to bleach neutralized cotton oil by considering the favorable volume weight, capacity of oil adsorbed and filtration rate. (author)

  19. Microstructure of bentonite in relation to its physical properties within nuclear waste repositories

    International Nuclear Information System (INIS)

    Laine, E.

    1998-01-01

    High-level nuclear waste in Finland is planned to be placed in bedrock at a depth of several hundred metres. The spent fuel containers in boreholes drilled in the floors of deposition tunnels will be surrounded by bentonite blocks. The upper parts of the tunnels will be filled with mixture of bentonite and crushed rock. The behaviour of the bentonite around the containers during several years after deposition of nuclear waste should be predicted. In the present report, a short literature study of the microstructure of bentonite is presented. The report concentrates on bentonite MX-80. The use of stochastic imaging of microstructure was tested by using the Boolean simulation. Using stochastic imaging, the effect of changes of bentonite microstructure on its physical properties can be evaluated and predicted. (orig.)

  20. Evaluation of permeability of compacted bentonite ground considering heterogeneity by geostatistics

    International Nuclear Information System (INIS)

    Tanaka, Yukihisa; Nakamura, Kunihiko; Kudo, Kohji; Hironaga, Michihiko; Nakagami, Motonori; Niwase, Kazuhito; Komatsu, Shin-ichi

    2007-01-01

    The permeability of the bentonite ground as an engineered barrier is possibly designed to the value which is lower than that determined in terms of required performance because of heterogeneous distribution of permeability in the ground, which might be considerable when the ground is created by the compaction method. The effect of heterogeneity in the ground on the permeability of the bentonite ground should be evaluated by overall permeability of the ground, whereas in practice, the effect is evaluated by the distribution of permeability in the ground. Thus, in this study, overall permeability of the bentonite ground is evaluated from the permeability of the bentonite ground is evaluated from the permeability distribution determined using the geostatistical method with the dry density data as well as permeability data of the undisturbed sample recovered from the bentonite ground. Consequently, it was proved through this study that possibility of overestimation of permeability of the bentonite ground can be reduced if the overall permeability is used. (author)

  1. Bentonite-like material sealing to high-level radioactive wastes storage

    International Nuclear Information System (INIS)

    Linares, J.; Linares Gonzalez, J.; Huertas Garcia, F.; Reyes Camacho.

    1993-01-01

    Among the most used materials for sealing of radioactive waste storage, bentonite shows a high number of advantages because of its plasticity, thermal and hydraulic conductivity, etc. The paper makes a review on different Spanish deposits of bentonite and their stability. Most of studies are focussed on the volcanic region at Cabo de Gata (Almeria). That area offers the most productive hydrothermal bentonite deposits in Spain

  2. Investigations of the changes in the bentonite structure caused by the different treatments

    OpenAIRE

    Stojiljković S.; Stamenković M.; Kostić D.; Miljković M.; Arsić B.; Savić I.; Savić I.

    2015-01-01

    The bentonite was treated in different ways and the changes in structure were monitored. Acid activation with sulphuric acid of investigated bentonite caused the increase in specific volume of micropore-mesopore. It was shown that activation by acid obtained at a constant temperature and constant period of time provides the possibility to obtain samples of bentonite of searched porosity only by changing the concentration of sulphuric and hydrochloric acid. ...

  3. Migration behaviour of Pu released from Pu-doped glass in compacted bentonite

    International Nuclear Information System (INIS)

    Ashida, T.; Kohara, Y.; Yui, M.

    1994-01-01

    In order to investigate the coupled behavior of Pu release from the waste glass and transport in bentonite, a migration experiment with compacted sodium-type bentonite saturated with distilled water was carried out at room temperature, in which Pu-doped borosilicate glass was sandwiched. Under these conditions, leaching of Pu from the glass, diffusion and sorption of Pu in the compacted bentonite occur simultaneously. (orig.)

  4. The use of Syrian bentonite to remove organics and other ions from commercial Syrian phosphoric acid

    International Nuclear Information System (INIS)

    Khorfan, S.; Abdulbaki, M.; Zein, A.

    2006-01-01

    Using of activated carbon to remove organic matter from phosphoric acid in uranium and P 2 O 5 extraction units has high cost. A new study was conducted to establish a new material instead of activated carbon. Experiments were carried out on removing organic matter by adsorption on Syrian bentonite. The experiments of the removal of humic acid by Syrian bentonite gave good results and showed that the chemical and thermal activation of bentonite increased the adsorption efficiency. (Authors)

  5. Investigation on the effect of seawater to hydraulic property and wetting process of bentonite

    International Nuclear Information System (INIS)

    Hasegawa, Takuma

    2004-01-01

    On high-level waste disposal, bentonite is one of the most promising material for buffer and backfill material. The hydraulic properties and wetting process of bentonite are important not only for barrier performance assessment but also for prediction of waste disposal environment, such as resaturation time and thermal distribution. In Japan, we should consider the effect of seawater for bentonite, because radioactive waste will be disposed of in coastal area and in marine sediment where seawater remained. However, it is not enough to understand the effect of seawater. Therefore, experimental study was conducted to investigate the effect of seawater on the hydraulic conductivity and wetting process of bentonite. The effect of seawater on hydraulic conductivity is significant for Na-bentonite, the hydraulic conductivity of Na-bentonite in seawater is one order to magnitude higher than that in distilled water. On the other hand, the hydraulic conductivity of Ca-bentonite is not influenced by seawater. The hydraulic conductivity of bentonite decreases as effective montmorillonite density increases. The effective montmorillonite density is ratio between the weight of montmorillonite and volume of porosity and montmorillonite. The hydraulic conductivity of bentonite is close related to swelling property since the hydraulic conductivity decrease as the swelling pressure increase. Wetting process of compacted bentonite could be evaluated by diffusion phenomena since infiltration rate and change of saturation rate and represented by diffusion equation. The effect of seawater on water diffusivity is significant for Na-type bentonite with low effective montmorillonite density. Except for that condition, the water diffusivity of bentonite is almost constant and is not influenced by effective montmorillonite density and seawater. (author)

  6. The use of Syrian bentonite to remove organics and other ions from commercial Syrian phosphoric acid

    International Nuclear Information System (INIS)

    Khorfan, S.; Abdulbaki, M.; Zein, A.

    2005-03-01

    Using of activated carbon to remove organic matter from phosphoric acid in uranium and P 2 O 5 extraction units has high cost. A new study was conducted to establish a new material instead of activated carbon. Experiments were carried out on removing organic matter by adsorption on Syrian bentonite. The experiments of the removal of humic acid by Syrian bentonite gave good results and showed that the chemical and thermal activation of bentonite increased the adsorption efficiency. (Authors)

  7. Comparative simulation study of coupled THM processes near back-filled and open-drift nuclear waste repositories in Task D of the International DECOVALEX Project

    International Nuclear Information System (INIS)

    Rutqvist, J.; Birkholzer, J.T.; Chijimatsu, M.; Kolditz, O.; Liu, Quan-Sheng; Oda, Y.; Wang, Wenqing; Zhang, Cheng-Yuan

    2006-01-01

    As part of the ongoing international DECOVALEX project, four research teams used five different models to simulate coupled thermal, hydrological, and mechanical (THM) processes near underground waste emplacement drifts. The simulations were conducted for two generic repository types, one with open and the other with back-filled repository drifts, under higher and lower post-closure temperature, respectively. In the completed first model inception phase of the project, a good agreement was achieved between the research teams in calculating THM responses for both repository types, although some disagreement in hydrological responses are currently being resolved. Good agreement in the basic thermal-mechanical responses was also achieved for both repository types, even though some teams used relatively simplified thermal-elastic heat-conduction models that neglect complex near-field thermal-hydrological processes. The good agreement between the complex and simplified process models indicates that the basic thermal-mechanical responses can be predicted with a relatively high confidence level

  8. Rheological characterization of nanocomposites Nylon 6/bentonite clay

    International Nuclear Information System (INIS)

    Silva, T.R.G.; Fernandes, P.C.; Oliveira, S.V.; Araujo, E.M.; Melo, T.J.A.

    2010-01-01

    Polymer nanocomposites are a class of materials that have been widely used in various applications. Among them, has been emphasizing the preparation of polymer films with barrier properties for applications in polymer membranes. In this work, nanocomposites of nylon 6/bentonite clay were obtained from a Homogenizer, in the ratios of 1, 3 and 5 wt% clay. The Brasgel PA bentonite clay was treated organically with Praepagen HY salt, to make it organophilic. By X-ray diffraction (XRD), it was showed that the efficiency of the incorporation of salt in the clay. The rheological curves showed that for the AST clay the torque did not change when compared with the pure nylon 6, while for the clay ACT, the torque increased gradually with the percentage of clay. (author)

  9. LABORATORY TESTING OF BENTONITE CLAYS FOR LANDFILL DESIGN AND CONSTRUCTION

    Directory of Open Access Journals (Sweden)

    Biljana Kovačević Zelić

    2007-12-01

    Full Text Available Top and bottom liners are one of the key construction elements in every landfill. They are usually made as compacted clay liners (CCLs composed of several layers of compacted clay with strictly defined properties or by the use of alternative materials such as: GCL – geosynthetic clay liner, BES – bentonite enhanced soils or bentonite/polymer mixtures. Following the state of the art experiences in the world, GCLs are used in Croatian landfills for several years, as well. Depending upon the location and the obeying function, GCLs have to fulfill certain conditions. A legislated compatibility criterion has to be proven by various laboratory tests. In the paper are presented the results of direct shear and chemical compatibility tests of GCLs as well as the results of permeability measurement of kaolin clay (the paper is published in Croatian .

  10. Retention of Cs on zeolite, bentonite and their mixtures

    International Nuclear Information System (INIS)

    Atun, G.

    2002-01-01

    The sorption behavior of cesium on zeolite and bentonite minerals and their mixtures was studied by means of a batch method and a tracer technique. All experiments were carried out in the presence of CsCl spiked with 137 Cs and NaCl as a supporting electrolyte in varying concentrations. The distribution coefficients (K D ) did not show significant differences at low Cs + loadings while they decreased in the high loading region. Freundlich and D-R isotherms were applied to the adsorption data of zeolite and bentonite. Adsorption capacities and mean energies calculated from D-R isotherm parameters decreased by increasing ionic strength on both minerals. The identification of the specific uptake sites was attempted on the basis of the Freundlich isotherm. Experimentally observed distribution coefficients of Cs on two mineral mixtures were smaller than theoretically calculated values, except at the highest NaCl concentration. (author)

  11. Sedimentation Characteristics of Kaolin and Bentonite in Concentrated Solutions

    Directory of Open Access Journals (Sweden)

    Abdulah Obut

    2005-11-01

    Full Text Available The sedimentation characteristics of two clays, namely kaolinite and bentonite, were determinated at high clay (5 % wt/vol and electrolyte (1 N concentrations using various inorganic-organic compounds. It was observed that the settling behaviour of kaolinite (1:1 clay and montmorillonite (2:1 clay is quite different due to the structural differences between these minerals. Although, similar initial settling rates and final sediment volumes were obtained after 24 hours of settling time for kaolin suspensions, the corresponding rates and volumes for bentonite suspensions varied greatly with the used chemical compound. According to the experimental results, a further intensive theoretical and experimental investigation is needed to reveal the mechanism underlying the sedimentation characteristics of clay minerals at high clay and electrolyte concentrations.

  12. Removal of uranium from water media by bentonite and zeolite

    International Nuclear Information System (INIS)

    Viglasova, E.; Krajnak, A.; Galambos, M.; Rosskopfova, O.

    2014-01-01

    The removal and recovery of uranium from contaminated surface, environment and ground water, as result of nuclear industries, has attracted more and more attentions. Several methods are available for removing of uranium, but adsorption among the others, is the most attractive. In case of management of radioactive waste, the adsorption of radionuclides plays significant role. Among the natural sorbents applied to the adsorption of uranium zeolites and bentonites offer a number of advantages. The main aims of this work are investigations of adsorption properties of Greek zeolite Metaxades and Greek bentonite Kimolos during adsorption of uranium from water solutions, comparison of their adsorption characteristics, fitting with isotherms (Freundlich, Langmuir and DR isotherm) and its behaviour during kinetics process influenced by temperature. (authors)

  13. Investigation of alteration behaviour of compacted bentonite contracted with carbon steel for 10 years

    International Nuclear Information System (INIS)

    Suyama, Tadahiro; Ueno, Kenichi; Sasamoto, Hiroshi

    2008-03-01

    To evaluate long term behavior of corrosion for carbon steel in compacted bentonite, and to evaluate long term stability of bentonite, corrosion experiments were conducted using synthetic sea water and synthetic groundwater at 50 and 80degC for 10 years under anaerobic atmosphere. In the present study, the samples of compacted bentonite after experiments were investigated to understand the alteration behavior of bentonite by iron-bentonite interactions. Results were summarized below. Iron generated by corrosion of carbon steel was migrated into compacted bentonite further in the synthetic seawater case than in the synthetic groundwater case. Result of TEM observation for the sample of synthetic sea water case at 80degC showed that the original layer structure for clay minerals was maintained and the layer distance was about 12[A] which was similar to the layer distance of normal 2:1 smectite. Thus, it was suggested that there was no change in smectite before and after experiments. Iron generated by corrosion of carbon steel was migrated into compacted bentonite in anaerobic condition case but scarcely migrated in aerobic condition case. Results of EPMA analysis indicated that the maximum migration depth of iron in compacted bentonite was about 0.2 mm for sample in synthetic sea water at 80degC under anaerobic condition. Results of XRD analysis for the sample in which iron migration in compacted bentonite was observed showed that there was no corrosion product in compacted bentonite and the structure of clay mineral in bentonite was di-octahedral. Furthermore, the result of XRD analysis under relative humidity controlled condition suggested that the swelling property of sample after experiment was similar to that of initial Na-type smectite. Therefore, it was supposed that the initial Na-type smectite did not change during the experiment. Batch type experiments with different temperature, solutions and duration have been conducted to understand the alteration

  14. Investigations of the changes in the bentonite structure caused by the different treatments

    Directory of Open Access Journals (Sweden)

    Stojiljković S.

    2015-01-01

    Full Text Available The bentonite was treated in different ways and the changes in structure were monitored. Acid activation with sulphuric acid of investigated bentonite caused the increase in specific volume of micropore-mesopore. It was shown that activation by acid obtained at a constant temperature and constant period of time provides the possibility to obtain samples of bentonite of searched porosity only by changing the concentration of sulphuric and hydrochloric acid. By thermal activation of bentonite clay in the temperature range 100-1100 0C, samples of desired porosity were acquired. [Projekat Ministarstva nauke Republike Srbije, br. 174007i br. TR 34020

  15. Characteristics study of bentonite as candidate of buffer materials for radioactive waste disposal system

    International Nuclear Information System (INIS)

    Suryantoro; Arimuladi, S.P.; Sastrowardoyo, P.B.

    1998-01-01

    Literature studies on bentonite characteristic of, as candidate for radioactive waste disposal system, have been conducted. Several information have been obtained from references, which would be contributed on performance assessment of engineered barrier. The functions bentonite includes the buffering of chemical and physical behavior, i.e. swelling property, self sealing, hydraulic conductivities and gas permeability. This paper also presented long-term stability of bentonite in natural condition related to the illitisazation, which could change its buffering capacities. These information, showed that bentonite was satisfied to be used for candidate of buffer materials in radioactive waste disposal system. (author)

  16. Study of the Properties of Bentonites for their use in Clay Geo synthetic Barriers

    International Nuclear Information System (INIS)

    Leiro Lopez, A.; Mateo Sanz, B.; Garcia Cidoncha, H.; Blanco Fernandez, M.

    2014-01-01

    Bentonites used for the production of clay geo synthetic barriers need to meet some properties so that they can be a waterproofing system. among the bentonites used in industry, sodium bentonite has the lowest permeability due to its high water absorption capacity in the inter-laminar space, causing it to swell and form a barrier to water flow. this paper provides the study of the properties of four bentonite to evaluate their quality the study of the properties of four bentonite to evaluate their quality. For this study, the main properties have been tested: water absorption, swelling index, fluid loss, cation exchange capacity and montmorillonite content. In order to optimize the procedure for the characterization of bentonites, correlations between different tests have been done, to identify the most suitable ones. Finally, a compatibility test has been carried out to study the performance of bentonites in water containing a high amount of sales, because in this case, an ion exchange between the interlayer sodium ions of bentonite and cations dissolved in the water can take, resulting in a decrease swell of the bentonite. (Author)

  17. Polyaniline (PANI) modified bentonite by plasma technique for U(VI) removal from aqueous solution

    Science.gov (United States)

    Liu, Xinghao; Cheng, Cheng; Xiao, Chengjian; Shao, Dadong; Xu, Zimu; Wang, Jiaquan; Hu, Shuheng; Li, Xiaolong; Wang, Weijuan

    2017-07-01

    Polyaniline (PANI) modified bentonite (PANI/bentonie) was synthesized by plasma induced polymerization of aniline on bentonite surface, and applied to uptake of uranium(VI) ions from aqueous solution. The as-synthesized PANI/bentonie was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). Batch adsorption technique was utilized to investigate the adsorption of U(VI) on bentonite and PANI/bentonite. The adsorption of U(VI) (10 mg/L) on PANI/bentonite surface is fairly depend on solution pH, ionic strength, and temperature in solution. The modified PANI on PANI/bentonite surface significantly enhances its adsorption capability for U(VI). The presence of humic acid (HA) can sound enhance U(VI) adsorption on PANI/bentonite at pH 6.5. According to the thermodynamic parameters, the adsorption of U(VI) on PANI/bentonite surface is a spontaneous and endothermic process. The results highlight the application of PANI/bentonite composites as candidate material for the uptake of trace U(VI) from aqueous solution.

  18. Characterization of organo-modified bentonite sorbents: The effect of modification conditions on adsorption performance

    Science.gov (United States)

    Parolo, María E.; Pettinari, Gisela R.; Musso, Telma B.; Sánchez-Izquierdo, María P.; Fernández, Laura G.

    2014-11-01

    The organic modification of a natural bentonite was evaluated using two methods: exchanging the interlayer cations by hexadecyltrimethylammonium (HDTMA) and grafting with vinyltrimethoxysilane (VTMS) and γ-methacryloyloxy propyl trimethoxysilane (TMSPMA) on montmorillonite surface. The physicochemical characterization of all materials was made by X-ray diffraction (XRD), IR spectroscopy, thermogravimetric analysis (TGA) and Brunauer-Emmett-Teller (BET) surface area techniques. HDTMA cations and organosilanes were intercalated into the interlayer space of montmorillonite, as deduced from the increase of the basal spacing. IR spectroscopy, TGA and BET area give evidence of successful organic modification. The studies show a decrease in the IR absorption band intensity at 3465 cm-1 with surfactant modification, and also a decrease of mass loss due to adsorbed water observed in two samples: the organoclay and functionalized bentonites, which are evidences of a lower interlayer hydrophilicity. The efficiency of aniline removal onto natural bentonite, organobentonite and functionalized bentonites from aqueous solutions was evaluated. Aniline sorption on natural bentonite was studied using batch experiments, XRD and IR spectroscopy. The hydrophobic surface of organobentonite and functionalized bentonites increased the retention capacity for nonionic organic substances such as aniline on bentonites. The sorption properties of modified bentonite, through different modification methods, enhanced the potential industrial applications of bentonites in water decontamination.

  19. Soil-bentonite design mix for slurry cutoff walls used as containment barriers

    International Nuclear Information System (INIS)

    Rad, N.S.; Bachus, R.C.; Jacobson, B.D.

    1995-01-01

    In recent years, soil-bentonite slurry cutoff walls have been increasingly used as containment barriers around contaminated soils to impede or, in some cases, nearly eliminate the off-site migration of contaminated ground water or other potentially hazardous liquids. The paper presents the procedures used and the results obtained during an extensive laboratory testing program performed to select varying soil-bentonite slurry mix components for a soil-bentonite slurry cutoff wall constructed around an old landfill at a former oil refinery. The landfill is underlain to varying depths by a coarse granular soils that has been exposed to oil-products. Compatibility of three commercially available bentonite products with the free oil-products and the oil-contaminated ground water found at some locations in the landfill was initially investigated. Based on the test results, one of the bentonite products was selected for use in the soil-bentonite slurry testing program. A clayey soil from a borrow source, potable water from the site, and subsurface soils from the proposed soil-bentonite slurry wall alignment were used to form different soil-bentonite slurry mixes. Slump tests were performed to evaluate the workability of the mixes. Based on the test results, a single mix was selected for further study, including permeability/compatibility testing. The results of the compatibility testing program are presented and discussed in the paper. A specific design mix methodology for evaluating the chemical compatibility of soil-bentonite slurry mixes with permeants is proposed

  20. One-dimensional self-sealing ability of bentonites in artificial seawater

    International Nuclear Information System (INIS)

    Komine, Hideo; Yasuhara, Kazuya; Murakami, Satoshi

    2009-01-01

    A high-level radioactive waste disposal facility might be built in a coastal area in Japan from the viewpoint of feasible transportation of waste. Therefore, it is important to investigate the effects of seawater on a bentonite-based buffer. This study investigated the influence of seawater on self-sealing ability of three common sodium-types of bentonite by the laboratory experiment and chemical analysis. From the results of laboratory experiment, suitable specifications were defined for a bentonite-based buffer that can withstand the effects of seawater. Furthermore, mechanism on filtration of seawater components in highly compacted bentonite was discussed by the results of chemical analysis. (author)

  1. Possibilities of reducing radiocesium transfer to hen eggs. II. Using bentonite from Polish geological deposits

    International Nuclear Information System (INIS)

    Rachubik, J.; Kowalski, B.

    2000-01-01

    The decontamination effectiveness of bentonite from Polish geological deposits in reducing the radiocesium transfer to hen eggs was examined. The egg white radiocesium concentration was higher than that in egg yolk. The highest decontamination efficacy in all egg components was noticed in animals treated with bentonite from the first day of radionuclide administration. Generally, the radioactivity concentration in hens treated simultaneously with 137CsCl and a cesium binder were lower by 50% than those in the controls. The decontamination efficiency lowered with the delayed bentonite treatment. In Poland bentonite seems to be an alternative to other decontamination agents. (author)

  2. Production of smectite organophylic clays from three commercial sodium bentonite

    International Nuclear Information System (INIS)

    Valenzuela Diaz, Francisco R.; Souza Santos, Persio de

    1995-01-01

    Laboratory cationic exchange procedures using Brazilian's commercial quaternary ammonium salt and three samples of commercial sodium bentonites (two Brazilian's and one from Wyoming (US) are described. Swelling values in some liquid organic media are shown for the organophilic clays and for a Brazilian's commercial organophilic clay. Organophilic clays with larger swelling values than the commercial organophilic clay in kerosene, Varsol, toluene and soya bean oil were obtained. (author)

  3. Removal of zinc from aqueous solutions by natural bentonite

    International Nuclear Information System (INIS)

    Mellah, A.; Chegrouche, S.

    1994-01-01

    The equilibrium isotherms of zinc adsorption onto natural bentonite show that the data correlate well with freundlich and Langmuir's models and that the adsorption is physical in nature. The operating parameters (agitation speed, solid/liquid ratio temperature, particle size and initial zinc concentration) influenced the rate of adsorption. The maximum monomolecular capacity (Q 0 ) according to the Langmuir model is 52.91 mg. g-1 for an initial zinc concentration of 300 mg. litre-1, At 20 0 C

  4. Leaching of rare earth elements from bentonite clay

    OpenAIRE

    van der Watt, J.G; Waanders, F.B

    2012-01-01

    Due to increasing concerns of global rare earth element shortfalls in the near future, possible alternative sources of rare earth elements have recently become of economic interest. One such alternative is decanting acid mine water originating primarily from abandoned old mines in the Witwatersrand region of the Republic of South Africa. In this study, a novel way of rare earth element removal from the acid mine drainage was employed, making use of bentonite clay, which has very good adsorben...

  5. Water uptake and motion in highly densified bentonite

    International Nuclear Information System (INIS)

    Kahr, G.; Mueller-Vonmoos, F.; Kraehenbuehl, F.; Stoeckli, H.F.

    1986-07-01

    Water uptake by the bentonites MX-80 and Montigel was investigated according to the classical method of determination of the heat immersion and the adsorption-desorption isotherms. In addition, the layer expansion of the montmorillonite was measured as a function of the water content. The evaluation of the adsorption isotherms according to Dubinin-Radushkevich and the stratification distances determined by x-ray confirmed gradual water uptake. Up to 10% water content, the water is adsorbed as a monolayer, up to 20%, as a bimolecular layer around the interlayer cations. The partial specific entropy could be determined from the approximative calculation of the partial specific enthalpy from the heats of immersion and the free enthalpy from the adsorption isotherms. From this it is evident that the interlayer water shows a high degree of order. In this condition, the mobility of the water molecules is considerably lower than in free water. From the adsorption isotherm and the layer expansion observed, it can be assumed that water can appear in the pore space only from approximately 25% water content. The spaces outwith the interlayer space and the surfaces of the montmorillonite particles are considered as pore space. If free swelling is prevented and with dry densities greater than 1.8 Mg/m/sup 3/ for the highly compacted bentonites, water uptake causes a drastic reduction of the original pore space so that practically all the water is in the interlayer space. Calculation of the swelling pressure from the adsorption isotherms gives a good approximation of the measured swelling pressures. A montmorillonite surface of ca. 750 m/sup 2//g for both bentonites can be derived from a Dubinin-Radushkevich analysis of the adsorption isotherm. Water uptake into the compacted unsaturated bentonites can be described as diffusion with a diffusion coefficient of the order of magnitude of 3.10/sup -10/ m/sup 2//s. (author)

  6. Preparation and performance of Ecobras/bentonite biodegrading films

    International Nuclear Information System (INIS)

    Costa, Ana Nery M.; Melo, Nadja M.C.; Canedo, Eduardo L.; Carvalho, Laura H.; Araujo, Arthur R.A.

    2011-01-01

    Compounds based on the biodegradable polymer Ecobras and bentonite clay in its pristine, sonicated, and organically modified with a quaternary ammonium salt forms were prepared as flat films. Clays and compounds were characterized by x-ray diffraction and scanning electron microscopy. Mechanical properties of the films were determined according to pertinent ASTM standards. Reasonable properties, higher than those of the matrix, were obtained with compounds prepared with purified clays and organoclays, particularly for low clay loading. (author)

  7. Diffusion and sorption properties of radionuclides in compacted bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Yu Ji-Wei; Neretnieks, I. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Chemical Engineering and Technology

    1997-07-01

    In this report, recent studies on sorption and diffusion of radionuclides in compacted bentonite have been reviewed. The sorption distribution coefficient and diffusion coefficient data obtained from experiments in the literature have been compiled. Based on these experimental data and the report SKB-TR--91-16 (Brandberg and Skagius, 1991), this report proposes a set of sorption distribution coefficient and diffusion coefficient values for modelling purpose for safety analysis of nuclear waste repositories. The variability and uncertainty of the diffusivity data span somewhat more than an order or magnitude up and down. Most of the nuclides have an effective diffusivity in around 10{sup -10} m{sup 2}/s. Ion exclusion effects are observed for C, Cl and for Tc in oxidizing waters. Effective diffusivities are nearly tow orders of magnitude lower for these elements and of the order of 10{sup -12} m{sup 2}/s. Surface diffusion effects are found for Cs, Ni, Pa, Pb, Ra, Sn, Sr and Zr. Effective diffusivities for these elements are of the order of 10{sup -8} m{sup 2}/s. The surface diffusion effect should decrease in saline waters which is seen for Cs and Sr where there are data available. It is also deemed that Ra will have this effect because of its similarity with Sr. The other nuclides should also show this decrease but no data is available. Sorption and diffusion mechanisms in compacted bentonite are discussed in the report. In highly compacted bentonite, sorption and hence its distribution coefficient is not well defined, and a pore diffusion coefficient or a surface diffusion coefficient is not well defined either. Therefore, an apparent diffusion coefficient and a total concentration gradient should be more relevant in describing the diffusion process in compacted bentonite. 99 refs.

  8. Advanced study of transport analysis in bentonite (2)

    International Nuclear Information System (INIS)

    Kawamura, Katsuyuki

    2004-03-01

    Solute and radionuclide transport analysis in buffer material made of bentonite clay is essential in safety assessment of a geological disposal facility for high-level radioactive waste (HLW). It is keenly required to understand the true physical and chemical process of the transport phenomena and to improve reliability of the safety assessment, since any conventional methods based on experimental models involve difficulty to estimate the robustness for a very long-term behavior. In order to solve this difficulty we start with the molecular dynamics (MD) simulation method for understanding the molecular-based fundamental properties such as an ionic state and diffusion characteristics of hydrated smectite clay minerals, and we extend the microscale properties to the macroscale behaviors by applying the multiscale homogenization method. In the study of this year we improved the MD atomic model for the hydrated clay minerals, and a new adsorption-diffusion analysis scheme by the homogenization analysis (HA). In the MD simulation first we improved the interatomic potential model for the smectitic clays. Then the behaviors of hydrated Na-beidellite and its substitution products by Cs and Ca were calculated. Not only the swelling behaviors of the beidellite minerals but also the diffusion characteristics of cations in the interlayer space are calculated. A microscopic image is important to specify micro/macro behavior of bentonite. Last year we observed microstructures of bentonite by using a confocal laser scanning microscope (LSM). Based on the knowledge of the local material properties obtained by MD and the microscopic observation we simulated the micro-/macro-behavior of diffusion experiments of the bentonite which included the microscale adsorption characteristics at the edges of clay minerals. (author)

  9. Advanced study of transport analysis in bentonite (3)

    International Nuclear Information System (INIS)

    Kawamura, Katsuyuki

    2005-02-01

    Solute and radionuclide transport analysis in buffer material made of bentonite clay is essential in safety assessment of a geological disposal facility for high-level radioactive waste (HLW). It is keenly required to understand the true physical and chemical process of the transport phenomena and to improve reliability of the safety assessment, since any conventional methods based on experimental models involve difficulty to estimate the robustness for a very long-term behavior. In order to solve this difficulty we start with the molecular dynamics (MD) simulation method for understanding the molecular-based fundamental properties such as an ionic state and diffusion characteristics of hydrated smectite clay minerals, and we extend the microscale properties to the macroscale behaviors by applying the multiscale homogenization analysis (HA) method. In the study of this year we improved the MD atomic model for the hydrated clay minerals, and a new adsorption-diffusion analysis scheme by the homogenization analysis (HA). In the MD simulation we precisely simulated the molecular behaviors of cations and H 2 O in the neighborhood of a clay mineral. In FY2002 the swelling property and diffusivity of interlayer cations, Cs and Ca, were calculated. In FY2003 the interatomic potential model was improved, and the diffusivity of several interlayer cations were calculated. In FY2004 the interatomic potential model was further improved, and the swelling and diffusive properties became more realistic. Then the coordination number of cations were calculated. A microscopic image is important to specify micro/macro behavior of bentonite. In FY2002 we observed microstructures of bentonite by using a confocal laser scanning microscope (LSM). In FY2003 based on the knowledge of the local material properties obtained by MD and the microscopic observation we simulated the micro-/macro-behavior of diffusion experiments of the bentonite which included the microscale adsorption

  10. Adsorption of strontium on different sodium-enriched bentonites

    Directory of Open Access Journals (Sweden)

    Marinović Sanja R.

    2017-01-01

    Full Text Available Bentonites from three different deposits (Wyoming, TX, USA and Bogovina, Serbia with similar cation exchange capacities were sodium enriched and tested as adsorbents for Sr2+ in aqueous solutions. X-Ray diffraction analysis confirmed successful Na-exchange. The textural properties of the bentonite samples were determined using low-temperature the nitrogen physisorption method. Significant differences in the textural properties between the different sodium enriched bentonites were found. Adsorption was investigated with respect to adsorbent dosage, pH, contact time and the initial concentration of Sr2+. The adsorption capacity increased with pH. In the pH range from 4.0–8.5, the amount of adsorbed Sr2+ was almost constant but 2–3 times smaller than at pH ≈11. Further experiments were performed at the unadjusted pH since extreme alkaline conditions are environmentally hostile and inapplicable in real systems. The adsorption capacity of all the investigated adsorbents toward Sr2+ was similar under the investigated conditions, regardless of significant differences in the specific surface areas. It was shown and confirmed by the Dubinin–Radushkevich model that the cation exchange mechanism was the dominant mechanism of Sr2+ adsorption. Their developed microporous structures contributed to the Sr2+ adsorption process. The adsorption kinetics obeyed the pseudo-second-order model. The isotherm data were best fitted with the Langmuir isotherm model. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III 45001

  11. 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

  12. Swelling pressure in compacted bentonite below 0°C

    International Nuclear Information System (INIS)

    Birgersson, Martin; Karnland, Ola; Nilsson, Ulf

    2010-01-01

    Document available in extended abstract form only. Bentonite is a common component in many concepts for underground storage of high level radioactive waste. During its lifetime, an underground repository will be subject to various ambient temperatures. Backfilled tunnels, shafts and investigation bore holes closest to ground level will experience periods of temperature below 0 deg. C. From a safety assessment perspective, it is therefore essential to investigate and understand the behavior of bentonite below 0 deg. C. A large set of laboratory tests have been performed where fully water saturated samples of bentonites have been exposed to temperatures in the range -10 deg. C - +25 deg. C. The swelling pressure response has been recorded continuously. The samples have been varied with respect to bentonite type (e.g. calcium or sodium dominated), smectite content and density. The general observation is that the pressure of the bentonite lowers in a temperature range between 0 deg. C and a specific (negative) temperature T c , which is strongly correlated to the swelling pressure measured above 0 deg. C. Consequently, Tc decreases (i.e. becomes more negative) with increased density or smectite content. At T c , swelling pressure is completely lost. Furthermore, a very weak pressure dependence is observed at temperatures above 0 deg. C. This dependence is however strictly dependent on sample density. For any type of bentonite at high enough densities above 0 deg. C, the slope of the P-T curve is negative and becomes more negative with increasing density. For Na-dominated bentonites at lower densities, on the other hand, the slope is positive. An important observation is that no pressure increase was observed for any of the tested bentonite samples as the transition to temperatures below 0 deg. C was made. Since water expands as it freezes, this observation indicates that no ice is formed in compacted bentonite as the 0 deg. C level is passed. The observed swelling

  13. Compression characteristics and permeability of saturated Gaomiaozi ca-bentonite

    International Nuclear Information System (INIS)

    Sun Wenjing; Sun De'an; Fang Lei

    2012-01-01

    The compression characteristics and permeability of compacted Gaomiaozi Ca-bentonite saturated by the water uptake tests are studied by conducting a series of one-dimension compression tests. The permeability coefficient can be calculated by the Terzaghi's one-dimensional consolidation theory after the consolidation coefficient is obtained by the square root of time method. It is found that the compression curves of compacted specimens saturated by the water uptake tests tend to be consistent in the relatively high stress range. The compression indexes show a linear decrease with increasing dry density and the swelling index is a constant. The permeability coefficient decreases with increasing compression stress, and they show the linear relationship in double logarithmic coordinates. Meanwhile, the permeability coefficient shows a linear decrease with decreasing void ratio, which has no relationship with initial states, stress states and stress paths. The permeability coefficient k of GMZ Ca-bentonite at dry density Pd of 1.75 g/cm 3 can be calculated as 2.0 × 10 -11 cm/s by the linear relationship between Pd and log k. It is closed to the permeability coefficient of GMZ Ca-bentonite with the same dry density published in literature, which testifies that the method calculating the permeability coefficient is feasible from the consolidation coefficient obtained by the consolidation test. (authors)

  14. Bentonite as a colloid source in groundwaters at Olkiluoto

    International Nuclear Information System (INIS)

    Vuorinen, U.; Hirvonen, H.

    2005-02-01

    In this work bentonite was studied as a potential source of colloids in Olkiluoto groundwaters. Samples were collected at two groundwater stations, PVA1 at 37.5 m dept and PVA3 at 95.6 m depth, in the VLJ-tunnel. The deeper groundwater at PVA3 was more saline (2.6g/L of Cl-) than the shallow at PVA1 (0.8g/L of Cl-). A bentonite source had been assembled at each groundwater station so that two sample lines were available for water samples; one for collecting a sample before and the other for collecting a sample after interaction with bentonite. Before starting the actual colloid sampling groundwaters from both sample lines at both stations were analysed. Only minor alterations, mostly within the uncertainty limits of the analysis methods, were brought about in the water chemistries after interaction with the bentonite sources. The only clear changes were seen in the concentration of iron which decreased after interaction with bentonite in the groundwaters at both stations. After groundwater sampling the actual colloid sampling was performed. The water samples were collected and treated inside a movable nitrogen filled glove-box. The samples could be collected from each sampling line directly in the glove-box via two quick-couplings that had been assembled on the front face of the box. The sample lines had been assembled with 0.45 μm filters before entering the glove-box, because only colloids smaller than 0.45 μm were of interest, as they are not prone to sedimentation in slow groundwater flows and therefore could act as potential radionuclide carriers. Colloid samples were collected and treated similarly from both sampling lines at both groundwater stations. For estimating the colloid content the groundwater samples were filtered with centrifugal ultrafiltration tubes of different cut-off values (0.3 μm, 300kD and 10kD). The ultrafiltrations produced the colloid-containing concentrate fractions and the soluble substances-containing filtrate fractions. In

  15. Modelling Ni diffusion in bentonite using different sorption models

    International Nuclear Information System (INIS)

    Pfingsten, W.; Baeyens, B.; Bradbury, M.

    2010-01-01

    Document available in extended abstract form only. An important component of the multi barrier disposal concept for a radioactive waste repository is the bentonite backfill surrounding the canisters containing vitrified high-level waste and spent fuel located in the tunnels deep within the chosen host rock. The effectiveness of the compacted bentonite barrier is such that calculations have indicated that many radionuclides have decayed to insignificant levels before having diffused through the thickness of bentonite. These calculations are performed using the simple Kd sorption concept in which the values are taken from batch type experiments performed on dispersed systems performed for a single metal at a time, usually at trace concentrations. However, in such complex systems many radionuclides, inactive metal contaminants/ground water components may be simultaneously present in the aqueous phase at a range of concentrations varying with time during the temporal evolution of the repository system. An important aspect influencing the sorption of any radioactive metal under a set of given geochemical conditions is its competition with other metals present, and how this may vary as a function of concentration. Competitive sorption effects are not currently included in safety assessments and are thus an issue which needs to be addressed. Here we provide some first estimates of the potential influence of competitive sorption effects on the migration of radioactive metals through compacted bentonite as a function of their concentration and the concentration of competing metals. Ni(II) and Fe(II) were chosen as possible competing cations since their concentration levels are expected to have values greater than trace levels and effects might be maximal and canister corrosion represents a permanent Fe source at the bentonite interface which could influence bivalent radionuclide diffusion. The modelling of the Ni(II) diffusion/sorption has been carried out using three

  16. Ageing effects on swelling behaviour of compacted GMZ01 bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Ye, W.M., E-mail: ye_tju@tongji.edu.cn [Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092 (China); United Research Center for Urban Environment and Sustainable Development, the Ministry of Education, China, Shanghai 200092 (China); Lai, X.L.; Liu, Y. [Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092 (China); Chen, Y.G. [Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092 (China); United Research Center for Urban Environment and Sustainable Development, the Ministry of Education, China, Shanghai 200092 (China); Cui, Y.J. [Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092 (China); Ecole des Ponts Paris Tech, UR Navier/CERMES (France)

    2013-12-15

    Highlights: • Ageing effects on compacted GMZ01 bentonite are investigated. • Swelling property decreases with ageing and influenced by initial conditions. • Ageing effects are mainly attributed to the bonding effects and the hydration of smectites. - Abstract: Ageing effects on the swelling properties of compacted GMZ01 bentonite are investigated in this paper. Samples were compacted to prescribed dry densities and water contents and kept for ageing under constant volume and K{sub 0} confined conditions for target days of 0, 1, 7, 15, 30 and 90. Then, swelling deformation and swelling pressure tests were performed on the aged samples. Results indicate that both the swelling deformation and swelling pressure decrease with ageing time, with a more significant decrease at the first few days of ageing. Ageing effects are more pronounced for samples with large dry density and high water content. At the same initial dry density and water content, samples aged under constant volume conditions show much smaller decrease of swelling pressure compared to that of samples aged under K{sub 0} confined conditions. The decrease of swelling potential of samples with ageing days is mainly attributed to the bonding effects and the internal redistribution of water within the bentonite, which was confirmed by the changes of microstructure of samples with ageing.

  17. Transient nuclide release through the bentonite barrier -SKB 91

    International Nuclear Information System (INIS)

    Bengtsson, A.; Widen, H.

    1991-05-01

    A study of near-field radionuclide migration is presented. The study has been performed in the context of the SKB91 study which is a comprehensive performance assessment of disposal of spent fuel. The objective of the present study has been to enable the assessment of which nuclides can be screened out because they decay to insignificant levels already in the near-field of the repository. A numerical model has been used which describes the transient transport of radionuclides through a small hole in a HLW canister imbedded in bentonite clay into a fracture in the rock outside the bentonite. Calculations for more than twenty nuclides, nuclides with both high and low solubility have been made. The effect of sorption in the bentonite backfill is included. The size of the penetration hole was assumed to be constant up to time when the calculations were terminated, 500000 year after the deposition. The mass transport rate is controlled by diffusion. The model is three dimensional. The report describes the geometry of the modelled system, the assumptions concerning the transport resistances at the boundary conditions, the handling of the source term and obtained release curves. (au)

  18. Indirect measurement of the 15N(p,α)12C reaction cross section through the THM

    International Nuclear Information System (INIS)

    Romano, S.; La Cognata, M.; Spitaleri, C.; Cherubini, S.; Gulino, M.; Lamia, L.; Musumarra, A.; Tribble, R.; Trache, C.L.; Fu, C.

    2005-01-01

    Among the reactions of the stellar CNO cycle, the 15 N(p,α) 12 C plays a crucial role. In particular its reaction rate is important for understanding the CNOI escape towards CNOII. Thus it is important to study its bare nucleus cross section at the energies typical of such astrophysical environments, i.e. few tens of keV. At these energies such a measurement is hard to perform in a direct way because of the electron screening effect as pointed out for several cases. A possibility is then given by indirect methods and in particular the Trojan Horse Method (THM) has been applied in this case. The preliminary validity test for the study of 15 N(p,α) 12 C via the 15 N(d,α 12 C)n three body reaction is reported in this work. A 15 N beam was provided by the cyclotron at Texas A and M University with energy 60 MeV/c and delivered onto a CD 2 target. A ΔE/E telescope (PSD + ionization chamber) and a pair of PSD's were mounted in a coplanar geometry. Coincidences between the detectors were considered and the 15 N-p quasi-free contribution to the overall three-body cross-section was selected. Data analysis and preliminary results will be discussed and compared with direct data. (author)

  19. Corrosion of high-level radioactive waste iron-canisters in contact with bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Kaufhold, Stephan, E-mail: s.kaufhold@bgr.de [BGR, Bundesanstalt für Geowissenschaften und Rohstoffe, Stilleweg 2, D-30655 Hannover (Germany); Hassel, Achim Walter [Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, D-40237 Düsseldorf (Germany); Institute for Chemical Technology of Inorganic Materials, Johannes Kepler University Linz, Altenberger Straße 69, 4040 Linz (Austria); Sanders, Daniel [Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, D-40237 Düsseldorf (Germany); Dohrmann, Reiner [BGR, Bundesanstalt für Geowissenschaften und Rohstoffe, Stilleweg 2, D-30655 Hannover (Germany); LBEG, Landesamt für Bergbau, Energie und Geologie, Stilleweg 2, D-30655 Hannover (Germany)

    2015-03-21

    Graphical abstract: Corrosion at the bentonite iron interface proceeds unaerobically with formation of an 1:1 Fe silicate mineral. A series of exposure tests with different types of bentonites showed that Na–bentonites are slightly less corrosive than Ca–bentonites and highly charges smectites are less corrosive compared to low charged ones. The formation of a patina was observed in some cases and has to be investigated further. - Highlights: • At the iron bentonite interface a 1:1 Fe layer silicate forms upon corrosion. • A series of iron–bentonite corrosion products showed slightly less corrosion for Na-rich and high-charged bentonites. • In some tests the formation of a patina was observed consisting of Fe–silicate, which has to be investigated further. - Abstract: Several countries favor the encapsulation of high-level radioactive waste (HLRW) in iron or steel canisters surrounded by highly compacted bentonite. In the present study the corrosion of iron in contact with different bentonites was investigated. The corrosion product was a 1:1 Fe layer silicate already described in literature (sometimes referred to as berthierine). Seven exposition test series (60 °C, 5 months) showed slightly less corrosion for the Na–bentonites compared to the Ca–bentonites. Two independent exposition tests with iron pellets and 38 different bentonites clearly proved the role of the layer charge density of the swelling clay minerals (smectites). Bentonites with high charged smectites are less corrosive than bentonites dominated by low charged ones. The type of counterion is additionally important because it determines the density of the gel and hence the solid/liquid ratio at the contact to the canister. The present study proves that the integrity of the multibarrier-system is seriously affected by the choice of the bentonite buffer encasing the metal canisters in most of the concepts. In some tests the formation of a patina was observed consisting of Fe

  20. Sorption and diffusion of FE(II) in bentonite

    International Nuclear Information System (INIS)

    Muurinen, A.; Tournassat, C.; Hadi, J.; Greneche, J.-M.

    2014-02-01

    The iron in the engineering barrier system of a nuclear waste repository interacts via the corrosion process with the swelling clay intended as the buffer material. This interaction may affect the sealing properties of the clay. In the case of iron-bentonite interaction, redox reactions, dissolution/precipitation, the diffusion and sorption are coupled together. In a combined study different processes are difficult to distinguish from each other, and more specific studies are needed for the separate processes. In particular, there is a need for well-controlled diffusion and sorption experiments where iron is kept as Fe(II). In this project, sorption and diffusion of Fe(II) in bentonite have been studied. The experiments were carried out under low-oxygen conditions in an anaerobic glove-box. The radioactive isotope ( 55 Fe) was used as a tracer in the experiments. The sorption experiments were carried out with two batches of purified MX-80 bentonite. One was purified at Bureau de Recherches Geologiques et Minieres, French Geological Survey (BRGM) and the other one at VTT Technical Research Centre of Finland (VTT). Experiments were also carried out with synthetic smectite, which did not include iron, which was prepared at LMPC (ENSC, F 68093 Mulhouse, France). The sorption experiments were carried out in 0.3 M and 0.05 M NaCl solutions as a function of pH, and in 0.3 M NaCl solution buffered at pH 5 as a function of added Fe(II) concentration. The separation of bentonite and solution at the end of the sorption experiment was carried out in the early phase by centrifuging only. In the later phase, ultrafiltering was added in order to improve the separation. The diffusion experiments were carried out in compacted samples prepared from MX-80 purified at VTT and saturated with 0.3 M NaCl at pH 8 and 5. A non-steady-state diffusion experiment method, where the tracer was introduced as an impulse source between two bentonite plugs was used in the measurements

  1. Sorption and diffusion of FE(II) in bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Muurinen, A. [VTT Technical Research Centre of Finland, Espoo (Finland); Tournassat, C.; Hadi, J. [BRGM, Orleans (France); Greneche, J.-M. [LPCE, Le Mans (France)

    2014-02-15

    The iron in the engineering barrier system of a nuclear waste repository interacts via the corrosion process with the swelling clay intended as the buffer material. This interaction may affect the sealing properties of the clay. In the case of iron-bentonite interaction, redox reactions, dissolution/precipitation, the diffusion and sorption are coupled together. In a combined study different processes are difficult to distinguish from each other, and more specific studies are needed for the separate processes. In particular, there is a need for well-controlled diffusion and sorption experiments where iron is kept as Fe(II). In this project, sorption and diffusion of Fe(II) in bentonite have been studied. The experiments were carried out under low-oxygen conditions in an anaerobic glove-box. The radioactive isotope ({sup 55}Fe) was used as a tracer in the experiments. The sorption experiments were carried out with two batches of purified MX-80 bentonite. One was purified at Bureau de Recherches Geologiques et Minieres, French Geological Survey (BRGM) and the other one at VTT Technical Research Centre of Finland (VTT). Experiments were also carried out with synthetic smectite, which did not include iron, which was prepared at LMPC (ENSC, F 68093 Mulhouse, France). The sorption experiments were carried out in 0.3 M and 0.05 M NaCl solutions as a function of pH, and in 0.3 M NaCl solution buffered at pH 5 as a function of added Fe(II) concentration. The separation of bentonite and solution at the end of the sorption experiment was carried out in the early phase by centrifuging only. In the later phase, ultrafiltering was added in order to improve the separation. The diffusion experiments were carried out in compacted samples prepared from MX-80 purified at VTT and saturated with 0.3 M NaCl at pH 8 and 5. A non-steady-state diffusion experiment method, where the tracer was introduced as an impulse source between two bentonite plugs was used in the measurements

  2. Formula of Moulding Sand, Bentonite and Portland Cement toImprove The Quality of Al-Si Cast Alloy

    OpenAIRE

    Andoko Andoko; Poppy Puspitasari; Avita Ayu Permanasari; Didin Zakaria Lubis

    2017-01-01

    A binder is any material used to strengthen the bonding of moulding sand grains. The primary function of the binder is to hold the moulding sand and other materialstogether to produce high-quality casts. In this study, there were four binder compositions being tested, i.e. 5% bentonite + 5% Portland cement, 4% bentonite + 6% Portland cement, 6% bentonite + 4% Portland cement, and 7% bentonite + 3% Portland cement. Each specimen was measured for its compressive strength, shear strength, tensil...

  3. FEBEX-DP. Dismantling the ''full-scale engineered barrier experiment'' after 18 years of operation at the Grimsel Test Site, Switzerland

    Energy Technology Data Exchange (ETDEWEB)

    Kober, Florian; Gaus, Irina [Nagra, Wettingen (Switzerland)

    2015-07-01

    dismantling project (FEBEX-DP) are: - Characterization of the key physical properties (e.g., density, water content) of the barrier and their distribution, - Characterization of corrosion and microbiological processes on instruments and coupons resulting from evolving redox conditions and saturation states, including gas analysis, - Characterization macro- and micro level studies of mineralogical interactions at material interfaces (e.g., cement-bentonite or iron-bentonite, rock-bentonite), - Assessment of sensor performance, - Further increasing understanding of the thermo-hydro-mechanical (THM) and thermo-hydro-chemical (THC) processes through integration of monitoring and dismantling results. An intensive laboratory program will be conducted in 2015/2016 in order to achieve the outlined main objectives. It includes extensive mineralogical, chemical and biological investigations of the buffer and the related interfaces. It will be accompanied by pre- and post dismantling modeling efforts. Unique data are expected after completing one of the longest running 1:1 in-situ EBS experiment under continued heating and natural saturation conditions. It will further consolidate the EBS knowledge and will act as a benchmark for major coupled modeling codes. The dismantling project is set-up as an international project with partners from Europe, Asia and North America. Further information can are under http://www.grimsel.com/gts-phase-vi/febex-dp/febex-dp-introduction.

  4. BENTONITE-QUARTZ SAND AS THE BACKFILL MATERIALS ON THE RADIOACTIVE WASTE REPOSITORY

    Directory of Open Access Journals (Sweden)

    Raharjo Raharjo

    2010-06-01

    Full Text Available An investigation of the contribution of quartz sand in the bentonite mixture as the backfill materials on the shallow land burial of radioactive waste has been done. The experiment objective is to determine the effect of quartz sand in a bentonite mixture with bentonite particle sizes of -20+40, -40+60, and -60+80 mesh on the retardation factor and the uranium dispersion in the simulation of uranium migration in the backfill materials. The experiment was carried out by the fixed bed method in the column filled by the bentonite mixture with a bentonite-to-quartz sand weight percent ratio of 0/100, 25/75, 50/50, 75/25, and 100/0 on the water saturated condition flown by uranyl nitrate solution at concentration (Co of 500 ppm. The concentration of uranium in the effluents in interval 15 minutes represented as Ct was analyzed by spectrophotometer, then using Co and Ct, retardation factor (R and dispersivity ( were determined. The experiment data showed that the bentonite of -60+80 mesh and the quartz sand of -20+40 mesh on bentonite-to-quartz sand with weight percent ratio of 50/50 gave the highest retardation factor and dispersivity of 18.37 and 0.0363 cm, respectively.   Keywords: bentonite, quartz sand, backfill materials, radioactive waste

  5. Corrosion of high-level radioactive waste iron-canisters in contact with bentonite.

    Science.gov (United States)

    Kaufhold, Stephan; Hassel, Achim Walter; Sanders, Daniel; Dohrmann, Reiner

    2015-03-21

    Several countries favor the encapsulation of high-level radioactive waste (HLRW) in iron or steel canisters surrounded by highly compacted bentonite. In the present study the corrosion of iron in contact with different bentonites was investigated. The corrosion product was a 1:1 Fe layer silicate already described in literature (sometimes referred to as berthierine). Seven exposition test series (60 °C, 5 months) showed slightly less corrosion for the Na-bentonites compared to the Ca-bentonites. Two independent exposition tests with iron pellets and 38 different bentonites clearly proved the role of the layer charge density of the swelling clay minerals (smectites). Bentonites with high charged smectites are less corrosive than bentonites dominated by low charged ones. The type of counterion is additionally important because it determines the density of the gel and hence the solid/liquid ratio at the contact to the canister. The present study proves that the integrity of the multibarrier-system is seriously affected by the choice of the bentonite buffer encasing the metal canisters in most of the concepts. In some tests the formation of a patina was observed consisting of Fe-silicate. Up to now it is not clear why and how the patina formed. It, however, may be relevant as a corrosion inhibitor. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. Characterization of Cr/Bentonite and HZSM-5 Zeolite as Catalysts for Ethanol Conversion to Biogasoline

    Directory of Open Access Journals (Sweden)

    Robert Ronal Widjaya

    2012-04-01

    Full Text Available In this research it has been done characterization on Cr/Bentonit and Zeolit HZSM-5 catalysts for ethanol catalytic process to biogasoline (equal to gasoline. Cr/Bentonit has high acidity and resistant to a lot of moisture, so in addition to being able to processing feed which a lot of moisture (>15% from ethanol-water mixture, also it is not easy deactivated. Cr/Bentonit which is then used as the catalyst material on the process of ethanol conversion to be biogasoline and the result was compared with catalyst HZSM-5 zeolite. Several characterization methods: X-ray diffraction, Brunauer Emmett Teller (BET, thermogravimetry analysis (TGA, and catalyst activity tests using catalytic Muffler instrument and gas chromatography-mass spectrometry (GC-MS for product analysis were performed on both catalysts. From acidity measurement, it is known that acidity level of Cr/Bentonit is the highest and also from XRD result, it is known there is shift for 2theta in Cr/Bentonit, which indicates that Cr-pillar in the Bentonite can have interaction. It is also supported by BET data that shows the addition of specific surface are in Cr/Bentonite compared with natural Bentonite before pillarization. Futhermore catalyst activity test produced the results, analyzed by GC-MS, identified as butanol and also possibly formed hexanol, decane, dodecane, undecane, which are all included in gasoline range (C4 until C12.

  7. Study on the saturating and swelling behavior of an engineering bentonite barrier using a test model

    International Nuclear Information System (INIS)

    Nakajima, Makoto; Kobayashi, Ichizo; Toida, Masaru; Fujisaki, Katsutoshi

    2007-01-01

    The conceptual design of a disposal facility with additional buffer depth for radioactive waste is mainly constituted from the multi-barrier system that is constructed around the waste form so that it prevents radionuclide transfer to the biosphere. The engineered bentonite barrier is one of the elements of the multi-barrier system and is constructed with homogeneous bentonite-containing material compacted to a high density so that there are no voids. Due to the swelling characteristics of the bentonite material, the self-sealing function which is an important function of the bentonite barrier can work, but at the same time it mechanically affects the neighboring structures. Therefore, an experimental study was implemented in order to evaluate the mechanical effect of the bentonite swelling behavior throughout the construction, emplacement operations and closure re-saturation phase. In this article, the results of swelling tests to obtain the mechanical properties of the bentonite and three types of test model experiments performed for the event observations in the different saturation processes are described. As a result, the effects of a seepage pattern of ground water and a variation in the density produced by construction on the swelling pressure distribution of the bentonite barrier could be reproduced and validated. It is thought that they will be important events when ground water permeates the bentonite layer of a multiple barrier system. (author)

  8. Literature study on the microstructure of bentonite and its effect on diffusion

    International Nuclear Information System (INIS)

    Muurinen, A.; Lehikoinen, J.; Pusch, R.

    1994-12-01

    In the study the available information from the literature on the microstructural properties of bentonite and its main component montmorillonite have been compiled, together with different phenomena which have been found to participate in the diffusion process in bentonite. (167 refs., 36 figs., 6 tabs.)

  9. Electrochemical and radiochemical material transport examinations in humate-containing montmorillonite a bentonite thin layers

    International Nuclear Information System (INIS)

    Antal, K.; Joo, P.

    1999-01-01

    Various humate-containing H-bentonite layers were investigated using 137 Cs ion transport and radio absorption measuring method. These processes can model radioactive contamination migration in soils exposed to acid rains. Experiment using montmorillonite and bentonite layers are discussed, and the results obtained with electrochemical and radioisotope absorption techniques are presented. (R.P.)

  10. Removal of nitrate by zero-valent iron and pillared bentonite

    International Nuclear Information System (INIS)

    Li Jianfa; Li Yimin; Meng Qingling

    2010-01-01

    The pillared bentonite prepared by intercalating poly(hydroxo Al(III)) cations into bentonite interlayers was used together with Fe(0) for removing nitrate in column experiments. The obvious synergetic effect on nitrate removal was exhibited through uniformly mixing the pillared bentonite with Fe(0). In such a mixing manner, the nitrate was 100% removed, and the removal efficiency was much higher than the simple summation of adsorption by the pillared bentonite and reduction by Fe(0). The influencing factors such as bentonite type, amount of the pillared bentonite and initial pH of nitrate solutions were investigated. In this uniform mixture, the pillared bentonite could adsorb nitrate ions, and facilitated the mass transfer of nitrate onto Fe(0) surface, then accelerated the nitrate reduction. The pillared bentonite could also act as the proton-donor, and helped to keep the complete nitrate removal for at least 10 h even when the nitrate solution was fed at nearly neutral pH.

  11. Geochemical modelling of hydrogen gas migration in an unsaturated bentonite buffer

    NARCIS (Netherlands)

    Sedighi, M.; Thomas, H.R.; Al Masum, S.; Vardon, P.J.; Nicholson, D.; Chen, Q.

    2014-01-01

    This paper presents an investigation of the transport and fate of hydrogen gas through compacted bentonite buffer. Various geochemical reactions that may occur in the multiphase and multicomponent system of the unsaturated bentonite buffer are considered. A reactive gas transport model, developed

  12. Effect of calcium bentonite on lipid parameters in Wistar albino rat ...

    African Journals Online (AJOL)

    The in vivo effect of Nigerian calcium bentonite clay on rat plasma cholesterol and triglyceride levels of Wistar albino rats was investigated. The rats were fed for a period of four weeks with varying concentrations of the bentonite clay, and the cholesterol and triglyceride levels determined using spectrophotometric methods.

  13. Sorption of technetium and its analogue rhenium on bentonite material under aerobic conditions

    International Nuclear Information System (INIS)

    Koudelkova, M.; Vinsova, H.; Konirova, R.; Ernestova, M.; Jedinakova-Krizova, V.; Tereesha, M.

    2003-01-01

    The uptake of technetium on bentonite materials has been studied from the point of view of characterization of long-term radioactive elements behavior in nuclear waste repository. Bentonite R (locality Rokle, Czech Republic) and two types of model groundwater (granitic and bentonite) were selected for the sorption experiments. The aim of our research has been to find out the conditions suitable for the technetium sorption on selected bentonite under oxidizing condition. The sorption experiments with Tc-99 on bentonite have been carried out by batch method. The influence of the addition of different materials (e.g. activated carbon, graphite, Fe 2+ ) with bentonite, the effect of solid: aqueous phase ratio and a pH value on the percentage of technetium uptake and on the K d values were tested. Perrhenate was selected as an analogue of pertechnetate in non-active experiments of capillary electrophoresis (CE) and isotachophoresis (ITP). The percentage of rhenium sorbed on bentonite material was determined from the decrease of perrhenate peak area (CE) and from the shortening of the ITP zone corresponding to perrhenate. Both electromigration methods provided comparable results. The results obtained in this study with non-active material were compared to those of technetium acquired by radiometry and polarography. The 8 days kinetics of the perrhenate and pertechnetate sorption on bentonite was described mathematically with a tendency to predict long-term behavior of studied systems. (authors)

  14. Theory and calculation of water distribution in bentonite in a thermal field

    International Nuclear Information System (INIS)

    Carnahan, C.L.

    1988-09-01

    Highly compacted bentonite is under consideration for use as a buffer material in geological repositories for high-level radioactive wastes. To assess the suitability of bentonite for this use, it is necessary to be able to predict the rate and spatial extent of water uptake and water distribution in highly compacted bentonite in the presence of thermal gradients. The ''Buffer Mass Test'' (BMT) was conducted by workers in Sweden as part of the Stripa Project. The BMT measured uptake and spatial distributions of water infiltrating annuli of compacted MX-80 sodium bentonite heated from within and surrounded by granite rock; the measurements provided a body of data very valuable for comparison to results of theoretical calculations. Results of experiments on adsorption of water by highly compacted MX-80 bentonite have been reported by workers in Switzerland. The experiments included measurements of heats of immersion and adsorption-desorption isotherms. These measurements provide the basis for prediction of water vapor pressures in equilibrium with bentonite having specified adsorbed water contents at various temperatures. The present work offers a phenomenological description of the processes influencing movement of water in compacted bentonite in the presence of a variable thermal field. The theory is applied to the bentonite buffer-water system in an assumed steady state of heat and mass transport, using critical data derived from the experimental work done in Switzerland. Results of the theory are compared to distributions of absorbed water in buffers observed in the Swedish BMT experiments. 9 refs., 2 figs

  15. Natural analogue study for interaction between alkaline groundwater and bentonite at Mangatarem region in the Philippines

    International Nuclear Information System (INIS)

    Tsukada, Y.; Fujita, K.; Nakabayashi, R.; Sato, T.; Yoneda, T.; Yamakawa, M.; Fujii, N.; Namiki, K.; Kasama, T.; Alexander, R.; Arcilla, C.; Pascua, C.

    2012-01-01

    Document available in extended abstract form only. Alteration of bentonite by alkaline leachate from cement/concrete in geological repositories for TRU radioactive waste is deleterious to bentonite performance as a buffer material. Although there have been many laboratory studies on high pH fluid-bentonite interaction for longer term understanding of the behavior of bentonites as buffer materials, different time scales between laboratory experiments and real disposal conditions impede its proper assessment. Thus, a natural analogue study can play an important role in (a) bridging the timescale gaps between laboratory experiments and real disposal conditions and (b) verifying the modeling studies of bentonite stability. Previous natural analogue studies on the cement-bentonite interaction are relatively few. Therefore, this study focuses on the process of serpentinization in ophiolitic rocks which resemble the process of leaching high pH ground waters from cement materials and report the results of study about alkaline water-bentonite interaction in Mangatarem, Philippines. In Mangatarem, in west central Luzon Island in the northern Philippines, there are bentonite quarries in the Aksitero Formation, which is part of the Zambales Ophiolite. Several alkaline hot springs derived from ongoing serpentinization of the ophiolite can be found in close proximity to the bentonite.Through a site characterization (including a foot survey, a series of boreholes and trench excavation in the Saile quarry in Mangatarem, the interface between the bentonite and the pillow lava of the upper ophiolite was confirmed, and chrysotile, a low temperature type of serpentine, was observed in the fault filling by XRD analysis. In the pillow lava, serpentine was also observed inside the fault that cut across both the bentonite and the pillow lava. From these facts, low temperature high pH fluids appears to have passed through the faults and came into contact with the bentonite. In order to

  16. Use of Bentonite in residual waters of tanneries for the removal of Cr(III)

    International Nuclear Information System (INIS)

    Echavarria Isaza, Adriana; Moreno Casaf, Monica; Ramirez Ochoa, Claudia; Tamayo Martinez, Claudia; Saldarriaga Molina, Carlos

    1998-01-01

    An efficient procedure is reported for Cr(III) removal from tannery waste waters by means of natural and chemically treated bentonites. The best result was obtained using 20 mL of effluent with 7.5 grams of Bentonite. With this quantity it was removed the total amount of chromium III present in the sample

  17. Coupled transport/reaction model of the properties of bentonite buffer in a repository

    International Nuclear Information System (INIS)

    Liu, Jinsong; Neretnieks, I.

    1996-11-01

    Two mechanisms that can affect the long-term properties of the bentonite buffer surrounding the canister in a final repository of spent nuclear fuel are studied. The two mechanisms are the oxidation of reducing minerals in the buffer by radiolytically generated oxidant, and the low-temperature alteration of Na-montmorillonite in the bentonite buffer to illite. A coupled mass transport with geochemical reaction model is used. Four cases have been considered, which differ in the assumptions of whether the radiolytically generated oxidant first oxidizes uraninite in the spent fuel, or it is directly transported to the bentonite to oxidize the pyrite. The cases also differ in the assumptions of varying initial concentrations of pyrite in the bentonite buffer. The modelling results show that, at low temperatures, the sodium montmorillonite in the bentonite buffer is chemically stable with respect to the chemical conditions of the near field. Alteration to illite and thus an increase in hydraulic conductivity and loss of swelling ability is not likely to occur. The radiolytically generated oxidant can possibly oxidize the reducing minerals in the bentonite buffer. A redox front can be generated. In all the cases considered in this study, the modelling results indicate that slightly less than 1% by weight of pyrite in the bentonite buffer will be able to ensure that the redox front does not penetrate through the bentonite buffer within 1 million years. 31 refs

  18. Effects of bentonite on plasma urea and creatinine of wistar albino rats.

    African Journals Online (AJOL)

    The in vivo effect of Nigerian calcium bentonite clay on wistar albino rat plasma urea and creatinine levels were investigated. The rats were fed for a period of four weeks with varying concentrations of the bentonite clay, and the urea and creatinine levels determined using spectrophotometric methods. Test results showed ...

  19. Freezing of bentonite. Experimental studies and theoretical considerations

    Energy Technology Data Exchange (ETDEWEB)

    Birgersson, Martin; Karnland, Ola; Nilsson, Ulf (Clay Technology AB, Lund (Sweden))

    2010-01-15

    During its lifetime, a KBS-3 repository will be subject to various ambient temperatures. Backfilled tunnels, shafts and investigation bore holes closest to ground level will experience periods of temperature below 0 deg C. From a safety assessment perspective, it is therefore essential to understand the behavior of compacted bentonite below 0 deg C. A theoretical framework for predicting the pressure response in compacted water saturated bentonite due to temperature changes has been developed based on thermodynamics and a single pore-type. This model predicts an approximately linear temperature dependence of swelling pressure P{sub s}(w,DELTAT) = P{sub s}(w,0 deg C) + DELTAs(w)DELTAT/nu{sub clay}(w) where DELTAT denotes a temperature difference from 0 deg C, DELTAs(w) is the difference in partial molar entropy between clay water and bulk water, nu{sub clay} (w) is the partial molar volume of the clay water and w denotes the water/solid mass ratio of the clay. As bulk water changes phase at 0 deg C, DELTAs(w) has a different value dependent on whether DELTAT is negative or positive. Above 0 deg C DELTAs(w) is a small value for all relevant densities which means that the pressure response due to temperature changes is small. A further consequence of this fact is that DELTAs(w) is a large positive number below 0 deg C when the external water phase is transformed to ice. Consequently, the model predicts a large drop of swelling pressure with temperature below 0 deg C, in the order of 1.2 MPa/deg C. Specifically, the swelling pressure is zero at a certain (negative) temperature T{sub C}. T{sub C} also quantifies the freezing point of the bentonite sample under consideration, as ice formation in the bentonite does not occur until swelling pressure is lost. A large set of laboratory tests have been performed where fully water saturated samples of bentonites have been exposed to temperatures in the range -10 deg C to +25 deg C. The swelling pressure response has been

  20. Wyoming bentonites. Evidence from the geological record to evaluate the suitability of bentonite as a buffer material during the long-term underground containment of radioactive wastes

    International Nuclear Information System (INIS)

    Smellie, J.

    2001-12-01

    In the Swedish programme for the deep, geological disposal of radioactive wastes, bentonite is planned to be used as a barrier material to reduce groundwater flow and minimise radionuclide migration into the geosphere. One of the possible threats to long-term bentonite stability is the gradual incursion of saline water into the repository confines which may reduce the swelling capacity of the bentonite, even to the extent of eliminating the positive effects of mixing bentonite into backfill materials. Important information may be obtained from the study of analogous processes in nature (i.e. natural analogue or natural system studies) where bentonite, during its formation, has been in long-term contact with reducing waters of brackish to saline character. Type bentonites include those mined from the Clay Spur bed at the top of the Cretaceous Mowry Formation in NE Wyoming and demarcated for potential use as a barrier material (e.g. MX-80 sodium bentonite) in the Swedish radioactive waste programme. This bentonite forms part of the Mowry Shale which was deposited in a southern embayment of the late Albian Western Interior Cretaceous sea (Mowry Sea). The question is whether these bentonite deposits show evidence of post-deposition alteration caused by the sea water in which they were deposited, and/or, have they been altered subsequently by contact with waters of increasing salinity? Bentonites are the product of pyroclastic fall deposits thought to be generated by the type of explosive, subaerial volcanic activity characteristic of Plinian eruptive systems. In Wyoming the overall composition of the original ash varied from dacite to rhyolite, or latite to trachyte. The ash clouds were carried to high altitudes and eastwards by the prevailing westerly winds before falling over the shallow Mowry Sea and forming thin but widespread and continuous horizons on sea floor muds and sands. Whilst bentonites were principally wind-transported, there is evidence of some water

  1. Wyoming bentonites. Evidence from the geological record to evaluate the suitability of bentonite as a buffer material during the long-term underground containment of radioactive wastes

    Energy Technology Data Exchange (ETDEWEB)

    Smellie, J [Conterra AB (Sweden)

    2001-12-01

    In the Swedish programme for the deep, geological disposal of radioactive wastes, bentonite is planned to be used as a barrier material to reduce groundwater flow and minimise radionuclide migration into the geosphere. One of the possible threats to long-term bentonite stability is the gradual incursion of saline water into the repository confines which may reduce the swelling capacity of the bentonite, even to the extent of eliminating the positive effects of mixing bentonite into backfill materials. Important information may be obtained from the study of analogous processes in nature (i.e. natural analogue or natural system studies) where bentonite, during its formation, has been in long-term contact with reducing waters of brackish to saline character. Type bentonites include those mined from the Clay Spur bed at the top of the Cretaceous Mowry Formation in NE Wyoming and demarcated for potential use as a barrier material (e.g. MX-80 sodium bentonite) in the Swedish radioactive waste programme. This bentonite forms part of the Mowry Shale which was deposited in a southern embayment of the late Albian Western Interior Cretaceous sea (Mowry Sea). The question is whether these bentonite deposits show evidence of post-deposition alteration caused by the sea water in which they were deposited, and/or, have they been altered subsequently by contact with waters of increasing salinity? Bentonites are the product of pyroclastic fall deposits thought to be generated by the type of explosive, subaerial volcanic activity characteristic of Plinian eruptive systems. In Wyoming the overall composition of the original ash varied from dacite to rhyolite, or latite to trachyte. The ash clouds were carried to high altitudes and eastwards by the prevailing westerly winds before falling over the shallow Mowry Sea and forming thin but widespread and continuous horizons on sea floor muds and sands. Whilst bentonites were principally wind-transported, there is evidence of some water

  2. Preliminary Study on Benzoic Acid Adsorption from Crude Active Coals and Bentonite

    Directory of Open Access Journals (Sweden)

    Abbes Boucheta

    2016-04-01

    Full Text Available We studied the adsorption of pollutant benzoic acid by the modified bentonite of Maghnia (west of Algeria, and coal (Coal from the mines, southwest of Algeria, Bechar area under three forms, crude and activated. Kinetic data show that the balance of bentonite (as amended adsorbs organic acids better than activated and raw coal. Indeed, the intercalation of bentonite with benzoic acid causes an improvement in the texture of porous material, which allows its use in the adsorption of organic compounds. The adsorption isotherms (Langmuir and Freundlich indicate that the adsorption of benzoic acid by the coal and bentonite yielded results favorably. The results obtained showed the practical value of using the activated coal and bentonite (as amended in the field of remediation of water contaminated with organic pollutants

  3. A study of the condition for the passivation of carbon steel in bentonite

    International Nuclear Information System (INIS)

    Taniguchi, Naoki; Morimoto, Masataka; Honda, Akira

    1999-01-01

    It is important to study the corrosion behavior of materials to be used for overpack for high-level radioactive waste disposal. Carbon steel is one of the candidate materials. The type of corrosion on carbon steel depends on whether the carbon steel is passivated or not. In this study, the condition for the passivation of carbon steel was studied using bentonite as the buffer material. Anodic polarization in bentonite and the measurements of pH of porewater in bentonite was measured. The results of these experiments showed that the possibility of passivation is small in highly compacted bentonite in groundwater in Japan. Therefore, localized corrosion on carbon steel due to the breakdown of passive film is unlikely in bentonite. In other words, general corrosion seems to be the most probable type of corrosion under repository condition in Japan. (author)

  4. Corrosion behavior of carbon steel in wet Na-bentonite medium

    International Nuclear Information System (INIS)

    Yeon, Jae-Won; Ha, Young-Kyoung; Choi, In-Kyu; Chun, Kwan-Sik

    1996-01-01

    Corrosion behaviors of carbon steel in wet Na-bentonite medium were studied. Corrosion rate of carbon steel in wet bentonite was measured to be 20 μm/yr at 25 deg C using the AC impedance technique. This value is agreed with that obtained by weight loss at 40 deg C for 1 year. The effect of bicarbonate ion on the corrosion of carbon steel in wet bentonite was also evaluated. The carbon steels in wet bentonite having 0.001, 0.01, and 0.1 M concentration of bicarbonate ion gave corrosion rates of 20, 8, and 0.2 μm/yr, respectively. Corrosion potentials of specimens were also measured and compared with the AC impedance results. Both results indicated that bicarbonate ion could effectively reduce the corrosion rate of carbon steels in bentonite due to the formation of protective layer on the carbon steel. (author)

  5. Cytotoxicity and mechanical behavior of chitin-bentonite clay based polyurethane bio-nanocomposites.

    Science.gov (United States)

    Zia, Khalid Mahmood; Zuber, Mohammad; Barikani, Mehdi; Hussain, Rizwan; Jamil, Tahir; Anjum, Sohail

    2011-12-01

    Chitin based polyurethane bio-nanocomposites (PUBNC) were prepared using chitin, Delite HPS bentonite nanoclay enriched in montmorillonite (MMT), 4,4'-diphenylmethane diisocyanate (MDI) and polycaprolactone polyol CAPA 231 (3000 g/mol(-1)). The prepolymers having different concentration of Delite HPS bentonite nanoclay were extended with 2 moles of chitin. The structures of the resulted polymers were determined by FT-IR technique. The effect of nanoclay contents on mechanical properties and in vitro biocompatibility was investigated. The mechanical properties of the synthesized materials were improved with increase in the Delite HPS bentonite nanoclay contents. Optimum mechanical properties were obtained from the PU bio-nanocomposite samples having 4% Delite HPS bentonite nanoclay. The results revealed that the final PU bio-nanocomposite having 2% Delite HPS bentonite nanoclay contents is ideal contenders for surgical threads with on going investigations into their in vitro biocompatibility, non-toxicity, and mechanical properties. Copyright © 2011 Elsevier B.V. All rights reserved.

  6. Mobility of U, Np, Pu, Am and Cm from spent nuclear fuel into bentonite clay

    International Nuclear Information System (INIS)

    Ramebaeck, H.; Skaalberg, M.; Eklund, U.B.; Kjellberg, L.; Werme, L.

    1998-01-01

    The mobility of uranium, neptunium, plutonium, americium and curium from spent nuclear fuel (UO 2 ) into compacted bentonite was studied. Pieces of spent BWR UO 2 fuel was embedded in a compacted bentonite clay/low saline synthetic groundwater system. After a contact time of six years the bentonite was sliced into 0.1 mm thick slices and analysed for its content of actinides. Radiometric as well as inductively coupled plasma mass spectrometry (ICP-MS) were used for the analysis. The influence on the mobility by the addition of metallic iron, metallic copper and vivianite (Fe(II)-mineral) to the bentonite clay was investigated. The results show a low mobility of actinides in bentonite clay. Except for uranium the mobility of the other actinides could, after six years of diffusion time, only be detected less than 1 mm from the spent fuel. (orig.)

  7. Erosion of bentonite by flow and colloid diffusion

    International Nuclear Information System (INIS)

    Moreno, Luis; Liu, Longcheng; Neretnieks, Ivars

    2010-01-01

    Document available in extended abstract form only. Bentonite intrusion into a fracture intersecting the canister deposition hole is modelled. The model describes the expansion of the bentonite within the fracture. It accounts for the repulsive electrostatic double-layer forces, the attractive van der Waals forces and friction forces between the particles and the water. The model also takes into account the diffusion of the colloid particles in the smectite sol. The buffer contains sodium in the pore water in much higher concentrations than the approaching seeping groundwater in the fracture has. Diffusion of sodium outward in the expanding gel is accounted for as this strongly influences the double layer force and the viscosity of the gel/sol. The gel/ sol is considered to be a fluid with a varying viscosity that is strongly dependent on the bentonite volume fraction in the gel and the sodium concentration in the water. Two different geometries were modelled; a rectangular and a cylindrical showing the flow in a fracture intersecting the deposition hole with the canister. The rectangular geometry was used to gain experience with the processes and mechanisms and how they interact since the cylindrical geometry was somewhat less stable numerically and more time consuming. In the rectangular geometry a fracture 1 metre long in the flow direction was modelled. In both geometries the fracture depth (extent from the deposition hole) was selected sufficiently large to ensure that the water velocity, near this border was nearly the same as the approaching water velocity and that the smectite concentration there was vanishingly small. It was found that the velocity of the fluid drops considerably where the bentonite volume fraction is larger than 1-2%. This is due to the strong increase in viscosity with increasing bentonite volume fraction. The loss of smectite as it is carried away by the slowly flowing fluid was found to be proportional to the square root of the seeping

  8. Review on cation exchange selectivity coefficients for MX-80 bentonite

    International Nuclear Information System (INIS)

    Domenech, C.; Arcos, D.; Duro, L.; Sellin, P.

    2005-01-01

    Full text of publication follows: Bentonite is considered as engineered barrier in the near field of a nuclear waste repository due to its low permeability, what impedes groundwater flow to the nuclear waste, and its high retention capacity (sorption) of radionuclides in the eventuality of groundwater intrusion. One of the main retention processes occurring at the bentonite surface is ion exchange. This process may exert a strong control on the mobility of major pore water cations. Changes in major cation concentration, especially calcium, can affect the dissolution-precipitation of calcite, which in turn controls one of the key parameters in the system: pH. The cation exchange process is usually described according to the Gaines-Thomas convention: Ca 2+ + 2 NaX = CaX 2 + 2 Na + , K Ca = (N Ca x a 2 Na + )/(N 2 Na x a Ca 2+ ) where K Ca is the selectivity coefficient for the Ca by Na exchange, ai is the activity of cation 'i' in solution and NJ the equivalent fractional occupancy of cation 'J' in bentonite. Parameters such as solid to liquid (S:L) ratio and dry density of the solid have an important influence on the value of selectivity coefficients (K ex ). Although in most geochemical modelling works, K ex values are directly taken from experiments conducted at low S:L ratios and low dry densities, the expected conditions in a deep geological nuclear waste repository are higher S:L and higher bentonite density (1.6 g.cm -3 in the SKB design to obtain a fully water saturated density of around 2.0 g.cm -3 ). Experiments focused at obtaining selectivity coefficients under the conditions of interest face the difficulty of achieving a proper extraction and analyses of pore water without disturbing the system by the sampling method itself. In this work we have conducted a complete analyses of published data on MX-80 bentonite cationic exchange in order to assess the effect of the S:L ratio and dry density on the value of the selectivity coefficients determined so far

  9. Behavior of plutonium interacting with bentonite and sulfate-reducing anaerobic bacteria

    International Nuclear Information System (INIS)

    Kudo, A.; Zheng, J.; Cayer, I.; Fujikawa, Y.; Yoshikawa, H.; Ito, M.

    1997-01-01

    The interactions between sulfate reducing anaerobic bacteria and plutonium, with or without bentonite present, were investigated using distribution coefficients [Kd (ml/g)] as an index of the radionuclide behavior. Plutonium Kds for living bacteria varied within a large range, from 1,804 to 112,952, depending on the pH, while the Kds ranged from 1,180 to 5,931 for dead bacteria. In general, living bacteria had higher plutonium Kds than dead bacteria. Furthermore, the higher Kd values of 39,677 to 106,915 for living bacteria were obtained for a pH range between 6.83 and 8.25, while no visible pH effect was observed for dead bacteria. These Kd values were obtained using tracers for both 236 Pu and 239 Pu, which can check the experimental procedures and mass balance. Another comparison was conducted for plutonium Kd values of mixtures of living bacteria with bentonite and sterilized bacteria with bentonite. The range of Kd values for the non-sterilized bacteria with bentonite were 1,194 to 83,648 while Kd values for the sterilized bacteria with bentonite were from 624 to 17,236. Again, the Kd values for the living bacteria with bentonite were higher than those of sterilized bacteria with bentonite. In other words, the presence of living anaerobic bacteria with bentonite increased, by roughly 50 times, the Kd values of 239 Pu when compared to the mixture of dead bacteria with bentonite. The results indicate that the effects of anaerobic bacteria within the engineered barrier system (in this case bentonite) will play a significant role in the behavior of plutonium in geologic repositories

  10. The advantages of a salt/bentonite backfill for Waste Isolation Pilot Plant disposal rooms

    International Nuclear Information System (INIS)

    Butcher, B.M.; Novak, C.F.; Jercinovic, M.

    1991-04-01

    A 70/30 wt% salt/bentonite mixture is shown to be preferable to pure crushed salt as backfill for disposal rooms in the Waste Isolation Pilot Plant (WIPP). This report discusses several selection criteria used to arrive at this conclusion: the need for low permeability and porosity after closure, chemical stability with the surroundings, adequate strength to avoid shear erosion from human intrusion, ease of emplacement, and sorption potential for brine and radionuclides. Both salt and salt/bentonite are expected to consolidate to a final state of impermeability (i.e., ≤ 10 -18 m 2 ) adequate for satisfying federal nuclear regulations. Any advantage of the salt/bentonite mixture is dependent upon bentonite's potential for sorbing brine and radionuclides. Estimates suggest that bentonite's sorption potential for water in brine is much less than for pure water. While no credit is presently taken for brine sorption in salt/bentonite backfill, the possibility that some amount of inflowing brine would be chemically bound is considered likely. Bentonite may also sorb much of the plutonium, americium, and neptunium within the disposal room inventory. Sorption would be effective only if a major portion of the backfill is in contact with radioactive brine. Brine flow from the waste out through highly localized channels in the backfill would negate sorption effectiveness. Although the sorption potentials of bentonite for both brine and radionuclides are not ideal, they are distinctly beneficial. Furthermore, no detrimental aspects of adding bentonite to the salt as a backfill have been identified. These two observations are the major reasons for selecting salt/bentonite as a backfill within the WIPP. 39 refs., 16 figs., 6 tabs

  11. Sorption of technetium and its analogue rhenium on bentonite material under aerobic conditions

    International Nuclear Information System (INIS)

    Vinsova, H.; Koudelkova, M.; Konirova, R.; Vecernik, P.; Jedinakova-Krizova, V.

    2003-01-01

    The uptake of technetium on bentonite materials has been studied from the point of view of characterization of long-term radioactive elements behavior in nuclear waste repository. Bentonite R (locality Rokle, Czech Republic) and two types of model groundwater (granitic and bentonite) were selected for the sorption experiments. It is generally known that bentonite materials show an excellent cation-exchange capacity and, on the other hand, a poor uptake of anions. Technetium occurs under aerobic conditions in its most stable oxidation state (+VII) as pertechnetate, which makes a question of its sorption on bentonite more complex when compared with e.g. Cs + or Sr 2+ . To increase the K d values for technetium sorption on bentonite, it is necessary to carry out the experiments under anaerobic conditions in the presence of reducing agent, which is capable to lower the oxidation state of technetium which enables its successful immobilization. The aim of our research has been to find out the conditions suitable for the technetium sorption on selected bentonite under oxidizing conditions. The sorption experiments with Tc-99 on bentonite have been carried out by batch method. The influence of the addition of different materials (e.g. activated carbon, graphite, Fe 2+ , Fe) with bentonite, the effect of solid:aqueous phase ratio and a pH value on the percentage of technetium uptake and on the K d values were tested. Perrhenate was selected as an analogue of pertechnetate in non-active experiments of capillary electrophoresis (CE) and isotachophoresis (ITP). The percentage of rhenium sorbed on bentonite material was determined from the decrease of perrhenate peak area (CE) and from the shortening of the ITP zone corresponding to perrhenate. Both electromigration methods provided comparable results. The results obtained in this study with non-active material were compared to those of technetium acquired by radiometry and polarography. (authors)

  12. Electrical resistivity and rheological properties of sensing bentonite drilling muds modified with lightweight polymer

    Directory of Open Access Journals (Sweden)

    Ahmed S. Mohammed

    2018-03-01

    Full Text Available In this study, the electrical resistivity and rheological properties of a water-based bentonite clay drilling mud modified with the lightweight polymer (guar gum under various temperature were investigated. Based on the experimental and analytical study, the electrical resistivity was identified as the sensing property of the bentonite drilling mud so that the changes in the properties can be monitored in real-time during the construction. The bentonite contents in the drilling muds were varied up to 8% by the weight of water and temperature was varied from 25 °C to 85 °C. The guar gum content (GG% was varied between 0% and 1% by the weight of the drilling mud to modify the rheological properties and enhance the sensing electrical resistivity of the drilling mud. The guar gum and bentonite clay were characterized using thermal gravimetric analysis (TGA. The total weight loss at 800 °C for the bentonite decreased from 12.96% to 0.7%, about 95% reduction, when the bentonite was mixed with 1% of guar gum. The results also showed that 1% guar gum decreased the electrical resistivity of the drilling mud from 50% to 90% based on the bentonite content and the temperature of the drilling mud. The guar gum modification increased the yield point (YP and plastic viscosity (PV by 58% to 230% and 44% to 77% respectively based on the bentonite content and temperature of the drilling mud. The rheological properties of the drilling muds have been correlated to the electrical resistivity of the drilling mud using nonlinear power and hyperbolic relationships. The model predictions agreed well with the experimental results. Hence the performance of the bentonite drilling muds with and without guar gum can be characterized based on the electrical resistivity which can be monitored real-time in the field. Keywords: Bentonite, Polymer (Guar gum, Electrical resistivity, Rheological properties, Temperature, Modeling

  13. Physicochemical, mineralogical and mechanical properties of domestic bentonite and bentonite-sand mixture as a buffer material in the high-level waste repository

    International Nuclear Information System (INIS)

    Cho, Won Jin; Lee, Jae Owan; Kang, Chul Hyung; Chun, Kwan Sik

    1999-09-01

    The physicochemical properties such as specific weight, free swell rate, chemical composition, cation exchange capacity (CEC), surface area and distribution coefficient of Kyunggju bentonite were measured, and the mineralogical analysis was performed to investigate the mineralogical composition. For the compacted bentonite and the mixture of bentonite and sand, the liquid and plastic limit, the linear shrinkage, and compaction property, the compression property, the shear property, and the consolidation property were investigated and analyzed. The bentonite contains montmorillonite (70 percent), feldspar (29 percent), and small amounts of quartz(-1 percent). The compressive strengths of bentonites are increased from 0.53 MPa to 8.83 MPa rapidly with increasing dry density of 1.4 g/cm 3 to 1.8 g/cm 3 . The cohesion and internal friction angles of bentonites with the dry density of 1.4 g/cm 3 to 1.8 g/cm 3 are in the range of 500 to 1100 kPa and 27 to 50 degree, respectively. (Author). 21 refs., 20 tabs., 46 figs

  14. Physicochemical, mineralogical and mechanical properties of domestic bentonite and bentonite-sand mixture as a buffer material in the high-level waste repository

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Won Jin; Lee, Jae Owan; Kang, Chul Hyung; Chun, Kwan Sik

    1999-09-01

    The physicochemical properties such as specific weight, free swell rate, chemical composition, cation exchange capacity (CEC), surface area and distribution coefficient of Kyunggju bentonite were measured, and the mineralogical analysis was performed to investigate the mineralogical composition. For the compacted bentonite and the mixture of bentonite and sand, the liquid and plastic limit, the linear shrinkage, and compaction property, the compression property, the shear property, and the consolidation property were investigated and analyzed. The bentonite contains montmorillonite (70 percent), feldspar (29 percent), and small amounts of quartz(-1 percent). The compressive strengths of bentonites are increased from 0.53 MPa to 8.83 MPa rapidly with increasing dry density of 1.4 g/cm{sup 3} to 1.8 g/cm{sup 3}. The cohesion and internal friction angles of bentonites with the dry density of 1.4 g/cm{sup 3} to 1.8 g/cm{sup 3} are in the range of 500 to 1100 kPa and 27 to 50 degree, respectively. (Author). 21 refs., 20 tabs., 46 figs.

  15. Adsorption of La(III) onto GMZ bentonite. Effect of contact time, bentonite content, pH value and ionic strength

    International Nuclear Information System (INIS)

    Yonggui Chen; Changsha University of Science and Technology, Changsha; Chunming Zhu; Weimin Ye; Yanhong Sun; Huiying Duan; Dongbei Wu

    2012-01-01

    Bentonite has been studied extensively because of its strong adsorption capacity. A local Na-bentonite named GMZ bentonite, collected from Gaomiaozi County (Inner Mongolia, China), was selected as the first choice of buffer/backfill material for the high-level radioactive waste repository in China. In this research, the adsorption of La (III) onto GMZ bentonite was performed as a function of contact time, pH, solid content and metal ion concentrations by using the batch experiments. The results indicate that the adsorption of La (III) on GMZ bentonite achieves equilibration quickly and the kinetic adsorption follows the pseudo-second-order model; the adsorption of La (III) on the adsorbent is strongly dependent on pH and solid content, the adsorption process follows Langmuir isotherm. The equilibrium batch experiment data demonstrate that GMZ bentonite is effective adsorbent for the removal of La (III) from aqueous solution with the maximum adsorption capacity of 26.8 mg g -1 under the given experimental conditions. (author)

  16. Modeling erosion of unsaturated compacted bentonite by groundwater flow; pinhole erosion test case

    International Nuclear Information System (INIS)

    Laurila, T.; Sane, P.; Olin, M.; Koskinen, K.

    2012-01-01

    swelling rate to erosion rate. Expressing eroded mass as a function of time as M(t) ∝ tβ. we note that for non-swelling material the wall shear -based erosion model gives β = 0,5. We find this limit in our model by suppressing swelling, and we observe that β increases when ratio of swelling to erosion increases, approaching values β ≅ 1 for strong swelling. It follows that the long term erosion of backfill and buffer materials are expected to differ, with erosion rates in the more compact buffer dropping slower. The result also suggests that the lower the initial erosion, the longer one can expect that rate to be maintained. We solve the model in cylindrically symmetric coordinates using COMSOL Multiphysics software, and fit parameters to match pinhole experiments on MX-80 bentonite with different salinities of the water inflow. Significant scatter within the experimental data makes it difficult to definitively validate models. Figure 1 shows erosion behavior in the model at the limit of vanishing swelling, and contrasts it to the highly-swelling case. Observations from the pinhole experiments, as well as from down-scaled piping erosion tests, show that erosion rates in buffer material don't drop significantly in time, suggesting a consistent with high swelling. In the larger piping erosion tests a seemingly steady state in the erosion rate is reached for an extended amount of time. The effects of scatter are reduced using statistical analysis of this state. An important experimental finding of unsaturated erosion is that larger salinities lead to larger erosion rates, in contrast to saturated erosion where the opposite has been observed. We expect this effect to be due to the processes of saturation, suction and permeability. Future work aims to model the dominant processes in this effect, as pertains to Posiva reference conditions for the Olkiluoto site, without going to the full complexity of (T)HM modeling, such as the Barcelona expansible model

  17. High Temperature Thermal Properties of Bentonite Foundry Sand

    Directory of Open Access Journals (Sweden)

    Krajewski P.K.

    2015-06-01

    Full Text Available The paper presents results of measuring thermal conductivity and heat capacity of bentonite foundry sand in temperature range ambient - 900­­°C. During the experiments a technical purity Cu plate was cast into the green-sand moulds. Basing on measurements of the mould temperature field during the solidification of the casting, the temperature relationships of the measured properties were evaluated. It was confirmed that water vaporization strongly influences thermal conductivity of the moulding sand in the first period of the mould heating by the poured casting.

  18. Morphology study of polyamide 6/bentonite clay nanocomposites

    International Nuclear Information System (INIS)

    Paz, Rene A.; Araujo, Edcleide M.; Melo, Tomas J.A.; Leite, Amanda M.D.; Medeiros, Vanessa Nobrega; Pessan, Luiz A.; Passador, Fabio R.

    2011-01-01

    Polymer/clay nanocomposites have had much attention in recent years, especially those developed with layered silicates, due to the need for engineering materials more efficient than pure polymers for certain applications. The level of exfoliation of layered silicates in the crystalline structure of polymer matrices has been studied and it has been observed that it affects the behavior of crystalline and therefore the mechanical and physical properties. In this study, polyamide 6 nanocomposites were obtained by the melt intercalation technique, using regional bentonite clay modified with a quaternary ammonium salt in an amount of 3% by weight. XRD and TEM tests showed obtaining nanocomposites with exfoliated structures (author)

  19. Development of polymer nanocomposites with regional bentonite clay

    International Nuclear Information System (INIS)

    Araujo, Edcleide M.; Leite, Amanda M.D.; Paz, Rene A. da; Medeiros, Keila M. de; Melo, Tomas J.A.; Barbosa, Josiane D.V.; Barbosa, Renata

    2011-01-01

    nanocomposites with regional bentonite clay were prepared by melt intercalation technique. The clays were studied without modification and modified with four quaternary ammonium salts. It was evidenced by X-ray diffraction that salts were incorporated into the clay structure thus confirming its organophilization. The nanocomposites were evaluated by means of thermal mechanic and flammability tests where presented properties significantly improved their pure polymers. The process of biodegradation of obtained bio nanocomposites was accelerated by the presence of clay. The produced membranes from nanocomposites have potential in the oil-water separation. (author)

  20. Microbial communities in bentonite formations and their interactions with uranium

    International Nuclear Information System (INIS)

    López-Fernández, Margarita; Fernández-Sanfrancisco, Omar; Moreno-García, Alberto; Martín-Sánchez, Inés; Sánchez-Castro, Iván; Merroun, Mohamed Larbi

    2014-01-01

    Highlights: • Microbial diversity of Spanish bentonites was studied. • High number of aerobe and facultative anaerobe microbes were isolated from bentonites. • Natural bentonite microbes are able to tolerate high U concentrations. • U is immobilized by the cells of the strain Rhodotorula mucilaginosa BII-R8 as U(VI) phosphates. - Abstract: A reliable performance assessment of deep geological disposal of nuclear waste depends on better knowledge of radionuclide interactions with natural microbes of geological formations (granitic rock, clay, salts) used to host these disposal systems. In Spain, clay deposits from Cabo de Gata region, Almeria, are investigated for this purpose. The present work characterizes the culture-dependent microbial diversity of two bentonite samples (BI and BII) recovered from Spanish clay deposits. The evaluation of aerobe and facultative anaerobe microbial populations shows the presence of a high number of cultivable bacteria (e.g. Stenotrophomonas, Micrococcus, Arthrobacter, Kocuria, Sphingomonas, Bacillus, Pseudomonas, etc.) affiliated to three phyla Proteobacteria, Actinobacteria, and Firmicutes. In addition, a pigmented yeast strain BII-R8 related to Rhodotorula mucilaginosa was also recovered from these formations. The minimal inhibitory concentrations of uranium for the growth of these natural isolates were found to range from 4 to 10.0 mM. For instance, strain R. mucilaginosa BII-R8 was shown to tolerate up to 8 mM of U. Flow cytometry studies indicated that the high U tolerance of this yeast isolate is a biologically mediated process. Microscopically dense intracellular and cell wall-bound precipitates were observed by Scanning Transmission Electron Microscopy-High-Angle Annular Dark-Field (STEM-HAADF). Energy Dispersive X-ray (EDX) element-distribution maps showed the presence of U and P within these accumulates, indicating the ability of cells to precipitate U as U(VI) phosphate minerals. Fundamental understanding of the

  1. Microbial communities in bentonite formations and their interactions with uranium

    Energy Technology Data Exchange (ETDEWEB)

    López-Fernández, Margarita; Fernández-Sanfrancisco, Omar; Moreno-García, Alberto; Martín-Sánchez, Inés; Sánchez-Castro, Iván; Merroun, Mohamed Larbi, E-mail: merroun@ugr.es

    2014-10-15

    Highlights: • Microbial diversity of Spanish bentonites was studied. • High number of aerobe and facultative anaerobe microbes were isolated from bentonites. • Natural bentonite microbes are able to tolerate high U concentrations. • U is immobilized by the cells of the strain Rhodotorula mucilaginosa BII-R8 as U(VI) phosphates. - Abstract: A reliable performance assessment of deep geological disposal of nuclear waste depends on better knowledge of radionuclide interactions with natural microbes of geological formations (granitic rock, clay, salts) used to host these disposal systems. In Spain, clay deposits from Cabo de Gata region, Almeria, are investigated for this purpose. The present work characterizes the culture-dependent microbial diversity of two bentonite samples (BI and BII) recovered from Spanish clay deposits. The evaluation of aerobe and facultative anaerobe microbial populations shows the presence of a high number of cultivable bacteria (e.g. Stenotrophomonas, Micrococcus, Arthrobacter, Kocuria, Sphingomonas, Bacillus, Pseudomonas, etc.) affiliated to three phyla Proteobacteria, Actinobacteria, and Firmicutes. In addition, a pigmented yeast strain BII-R8 related to Rhodotorula mucilaginosa was also recovered from these formations. The minimal inhibitory concentrations of uranium for the growth of these natural isolates were found to range from 4 to 10.0 mM. For instance, strain R. mucilaginosa BII-R8 was shown to tolerate up to 8 mM of U. Flow cytometry studies indicated that the high U tolerance of this yeast isolate is a biologically mediated process. Microscopically dense intracellular and cell wall-bound precipitates were observed by Scanning Transmission Electron Microscopy-High-Angle Annular Dark-Field (STEM-HAADF). Energy Dispersive X-ray (EDX) element-distribution maps showed the presence of U and P within these accumulates, indicating the ability of cells to precipitate U as U(VI) phosphate minerals. Fundamental understanding of the

  2. FEBEX II Project THG Laboratory Experiments

    International Nuclear Information System (INIS)

    Missana, T.

    2004-01-01

    The main roles of the bentonite in a radioactive waste repository is to act as a geochemical barrier against the radionuclides migration. The effectiveness of this geochemical barrier depends on the surface properties of the solid phases and on the physico-chemical environment generated by the interaction of the solid phases with the groundwater. Within the FEBEX (Full-scale Engineered Barriers Experiment) project, a program of laboratory tests was designed to study and to understand the processes taking place in the clay barrier. Since the first stages of the project, these laboratory tests enabled to isolate different processes, making easier their interpretation, and provided fundamental parameters to be used in the Thermo Hydro Mechanical (THM) and Thermo Hydro Geochemical (THG) models. Additionally, experimental data enabled to check the predictive capability of these models. In the second phase of the project, laboratory tests focused on all those relevant aspects not sufficiently covered during FEBEX I. Particularly, the following main objectives were proposed for the THG investigations during FEBEX II : Attainment of a reliable description of the pore water chemistry at different geochemical conditions. Identification of the different types of water present in the bentonite and to determine the amount of available water for the solute transport.Evaluation of the potential effects of the extraction pressure in the chemical composition of the water obtained by squeezing methods.Study of the effects of the exchange complex in the rheological properties of the clay.Identification and modelling of the surface processes occurring in smectite, determination of the solubility constants of smectite and the formation constants of the surface complexes.Understanding of the mechanisms involved in the sorption of different radionuclides in the bentonite. Investigation of the diffusion mechanisms of conservative neutral and anionic species to have a deeper insight on the

  3. FEBEX II Project THG Laboratory Experiments

    Energy Technology Data Exchange (ETDEWEB)

    Missana, T.

    2004-07-01

    The main roles of the bentonite in a radioactive waste repository is to act as a geochemical barrier against the radionuclides migration. The effectiveness of this geochemical barrier depends on the surface properties of the solid phases and on the physico-chemical environment generated by the interaction of the solid phases with the groundwater. Within the FEBEX (Full-scale Engineered Barriers Experiment) project, a program of laboratory tests was designed to study and to understand the processes taking place in the clay barrier. Since the first stages of the project, these laboratory tests enabled to isolate different processes, making easier their interpretation, and provided fundamental parameters to be used in the Thermo Hydro Mechanical (THM) and Thermo Hydro Geochemical (THG) models. Additionally, experimental data enabled to check the predictive capability of these models. In the second phase of the project, laboratory tests focused on all those relevant aspects not sufficiently covered during FEBEX I. Particularly, the following main objectives were proposed for the THG investigations during FEBEX II : Attainment of a reliable description of the pore water chemistry at different geochemical conditions. Identification of the different types of water present in the bentonite and to determine the amount of available water for the solute transport.Evaluation of the potential effects of the extraction pressure in the chemical composition of the water obtained by squeezing methods.Study of the effects of the exchange complex in the rheological properties of the clay.Identification and modelling of the surface processes occurring in smectite, determination of the solubility constants of smectite and the formation constants of the surface complexes.Understanding of the mechanisms involved in the sorption of different radionuclides in the bentonite. Investigation of the diffusion mechanisms of conservative neutral and anionic species to have a deeper insight on the

  4. Reaction rate of the 13C(α,n)16O neutron source using the ANC of the -3 keV resonance measured with the THM

    Science.gov (United States)

    La Cognata, M.; Spitaleri, C.; Trippella, O.; Kiss, G. G.; Rogachev, G. V.; Mukhamedzhanov, A. M.; Avila, M.; Guardo, G. L.; Koshchiy, E.; Kuchera, A.; Lamia, L.; Puglia, S. M. R.; Romano, S.; Santiago, D.; Spartà, R.

    2016-01-01

    The s-process is responsible of the synthesis of most of the nuclei in the mass range 90 ≤ A ≤ 208. It consists in a series of neutron capture reactions on seed nuclei followed by β-decays, since the neutron accretion rate is slower than the β-decay rate. Such small neutron flux is supplied by the 13C(α,n)16O reaction. It is active inside the helium-burning shell of asymptotic giant branch stars, at temperatures ANC and THM.

  5. Eutrophication management in surface waters using lanthanum modified bentonite

    DEFF Research Database (Denmark)

    Copetti, Diego; Finsterle, Karin; Marziali, Laura

    2016-01-01

    This paper reviews the scientific knowledge on the use of a lanthanum modified bentonite (LMB) to manage eutrophication in surface water. The LMB has been applied in around 200 environments worldwide and it has undergone extensive testing at laboratory, mesocosm, and whole lake scales. The availa......This paper reviews the scientific knowledge on the use of a lanthanum modified bentonite (LMB) to manage eutrophication in surface water. The LMB has been applied in around 200 environments worldwide and it has undergone extensive testing at laboratory, mesocosm, and whole lake scales....... The available data underline a high efficiency for phosphorus binding. This efficiency can be limited by the presence of humic substances and competing oxyanions. Lanthanum concentrations detected during a LMB application are generally below acute toxicological threshold of different organisms, except in low...... alkalinity waters. To date there are no indications for long-term negative effects on LMB treated ecosystems, but issues related to La accumulation, increase of suspended solids and drastic resources depletion still need to be explored, in particular for sediment dwelling organisms. Application of LMB...

  6. Investigation of Erosion of Cement-Bentonite via Piping

    Directory of Open Access Journals (Sweden)

    Zijun Wang

    2017-01-01

    Full Text Available Cement-bentonite is one of the main materials used in the seepage barriers to protect earth dams and levees from water erosion. However, the current understanding of the erodibility of the cementitious materials and the interactions between cracked seepage barriers and the water flow is inadequate. Based on the laboratory pinhole erosion test, we first investigated the impacts of cement-bentonite treatments by using the ground granulated blast-furnace slag (GGBS as replacement on the erosion characteristics, compared with the original mixtures; the inclusion of GGBS highlighted a potential advantage against water erosion. In addition, we proposed to calculate the erosion percentage and establish the mathematical relationships between the erosion percentage and different regimes, that is, different curing period, erosion time, and sizes of initial holes. Results showed that enough curing period was critical to avoid the increases of hydraulic conductivity in the macrofabric of the barrier; meanwhile, the materials were eroded quickly at the beginning and slowed down with the erosion time, where the enlargement of the initial creaks would be stabilised at some point in time. Moreover, the sizes of initial holes may affect the erosion situation varying from the sample curing periods.

  7. Adsorption behaviour of bivalent ions onto Febex bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Missana, T.; Garcia-Gutierrez, M. [Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT), Dpt. de Impacto Ambiental de la Energia Madrid (Spain)

    2005-07-01

    The sorption and transport properties of radionuclides in the near and far field barriers of a deep geological radioactive waste repository are amongst the principal aspects to be evaluated for the performance assessment (PA) of such a kind of disposal. The study of the clayey materials is crucial because the backfill material is constituted by compacted clay in most countries design; in addition, argillaceous formations are particularly suitable as host rock formations. It is widely recognised that, to acquire predictive modelling capability, a theoretical effort is needed for a mechanistic understanding of sorption processes, as they greatly influence the transport of radionuclides in clay porous structures. In this work, an exhaustive experimental study of the Co(II), Sr (II) and Ca(II) sorption behaviour on a Spanish bentonite was carried out. The clay used for these experiments is the FEBEX bentonite, which is basically formed by smectite (93 {+-} 2%) with small percentages of quartz (2 {+-} 1 %), plagioclase (3 {+-} 1 %), cristobalite (2 {+-} 1 %) and traces of minerals such as K-feldspar and calcite. (authors)

  8. Stress/strain/time properties of highly compacted bentonite

    International Nuclear Information System (INIS)

    Pusch, R.

    1983-05-01

    In this paper, a recently developed creep theory based on statistical mechanics has been used to analyze a number of experimental creep curves, the conclusion being that the creep behavior of dense MX-80 bentonite is in agreement with the physical model, and that the average bond strength is within the hydrogen bond region. The latter conclusion thus indicates that interparticle displacements leading to macroscopic creep takes place in interparticle and intraparticle water lattices. These findings were taken as a justification to apply the creep theory to a prediction of the settlement over a one million year period. It gave an estimated settlement of 1 cm at maximum, which is of no practical significance. The thixotropic and viscous properties of highly compacted bentonite present certain difficulties in the determination and evaluation of the stress/strain/time parameters that are required for ordinary elastic and elasto-plastic analyses. Still, these parameters could be sufficiently well identified to allow for a preliminary estimation of the stresses induced in the metal canisters by slight rock displacements. The analysis, suggests that a 1 cm rapid shear perpendicular to the axes of the canisters can take place without harming them. (author)

  9. Evaluation of hydraulic conductivities of bentonite and rock under hyper alkaline and nitrate conditions

    International Nuclear Information System (INIS)

    Iriya, K.; Fujii, K.; Kubo, H.

    2002-02-01

    The chemical conditions of TRU waste repository were estimated as alkaline conditions effected by cementitious materials. And, some TRU wastes include soluble nitrate salt, we have to consider the repository conditions might be high ionic strength condition leaching of nitrate salt. In this study, experimental studies were carried out to evaluate hydraulic conductivities of bentonite and rock under hyper alkaline and nitrate conditions. The followings results were obtained for bentonite. 1) In the immersion experiments of bentonite in hyper alkaline fluids with and without nitrate, the disappearance of montmorillonite of bentonite was observed and CSH formation was found after 30 days. In hyper alkaline fluid with nitrate, minerals at θ=37 nm by XRD was identified. 2) Significant effects of hyper alkaline on hydraulic conductivity of compacted bentonite were not observed. However, hydraulic conductivities of hyper alkaline fluid with nitrate and ion exchanged bentonite increased. In hyper alkaline with nitrate, more higher hydraulic conductivities of exchanged bentonite were measured. The followings results were obtained for rock. 1) In the immersion experiments of crushed tuff in hyper alkaline fluids with and without nitrate, CSH and CASH phases were observed. 2) The hydraulic conductivity of tuff in hyper alkaline fluids decreased gradually. Finally, hyper alkaline flow in tuff stopped after 2 months and hyper alkaline flow with nitrate stopped shorter than without nitrate. In the results of analysis of tuff after experiment, we could identified secondary minerals, but we couldn't find the clogging evidence of pores in tuff by secondary minerals. (author)

  10. Bentonite analogue research related to geological disposal of radioactive waste: current status and future outlook

    Energy Technology Data Exchange (ETDEWEB)

    Reijonen, H.M. [Saanio and Rickkola Oy, Helsinki (Finland); Russel, A.W. [Bedrock Geosciences, Auenstein (Switzerland)

    2015-06-15

    The practice of utilising natural analogues in assessing the long-term behaviour of various components of geological repositories for radioactive waste is already well established in most disposal programmes. Numerous studies on bentonites, focussing on bentonite interaction with other components of the engineered barrier system and a range of host rock environments, are present in the literature. In this article, recent bentonite natural analogue studies are briefly reviewed, and gaps in the current literature identified, with the aim of (1) suggesting where relevant new information could be obtained by data mining published bentonite natural analogue studies with a new focus on current safety case requirements, (2) collecting relevant information by revisiting known bentonite analogue sites and conducting investigations with more appropriate analytical techniques, and (3) identifying novel study sites where, for example, bentonite longevity in very dilute to highly saline groundwater conditions can be studied. It must be noted that the use of natural analogues in safety case development is likely to be site and repository design-specific in nature and thus emphasis is placed on the appropriate use of relevant natural analogue data on bentonite longevity. (authors)

  11. Applicability of low alkaline cement for construction and alteration of bentonite in the cement. 2

    International Nuclear Information System (INIS)

    Iriya, Keishiro; Fujii, Kensuke; Tajima, Takatoshi; Takeda, N.; Kubo, Hiroshi

    2003-02-01

    This study consists of accelerating corrosion test of rebar in saline, automogeneous shrinkage test of HFSC, accelerating test for bentonite and rock, and summarizing rock and bentonite alteration. Corrosion of rebars in HFSC: Since sorption capacity of HFSC for Cl ion is slow due to low alkalinity, rate of corrosion of rebar in HFSC is very large. Cracking due to corrosion is generating in 4 years or 20 years, although service period is deferent in OPC amount. Automogenous shrinkage: Automogenous shrinkage of HFSC is larger than OPC in cement paste. It decreases corresponding to rise of fly ash content. The shrinkage in HFSC 226 is quite similar to OPC. The shrinkage in HFSC concrete is smaller than OPC concrete. 720 days alteration test of bentonite by solution of low alkaline cement: Ion exchange to Ca bentonite and calcite are observed in the solid phase. Thin plate of bentonite is disappeared and round shaped secondary mineral is generated. Dissolution of bentonite and generation of secondary minerals are limited in pH 11.0 or less, since pH of bentonite is about 10.0. 720 days alteration test of rock by solution of low alkaline cement: Calcite is generated in very test. Very small evidence is observed as generation of secondary minerals. Etched pits are observed in tuff A due to corrosion. (author)

  12. Bentonite analogue research related to geological disposal of radioactive waste: current status and future outlook

    International Nuclear Information System (INIS)

    Reijonen, H.M.; Russel, A.W.

    2015-01-01

    The practice of utilising natural analogues in assessing the long-term behaviour of various components of geological repositories for radioactive waste is already well established in most disposal programmes. Numerous studies on bentonites, focussing on bentonite interaction with other components of the engineered barrier system and a range of host rock environments, are present in the literature. In this article, recent bentonite natural analogue studies are briefly reviewed, and gaps in the current literature identified, with the aim of (1) suggesting where relevant new information could be obtained by data mining published bentonite natural analogue studies with a new focus on current safety case requirements, (2) collecting relevant information by revisiting known bentonite analogue sites and conducting investigations with more appropriate analytical techniques, and (3) identifying novel study sites where, for example, bentonite longevity in very dilute to highly saline groundwater conditions can be studied. It must be noted that the use of natural analogues in safety case development is likely to be site and repository design-specific in nature and thus emphasis is placed on the appropriate use of relevant natural analogue data on bentonite longevity. (authors)

  13. Low-temperature pyrolysis of oily sludge: roles of Fe/Al-pillared bentonites

    Directory of Open Access Journals (Sweden)

    Jia Hanzhong

    2017-09-01

    Full Text Available Pyrolysis is potentially an effective treatment of oily sludge for oil recovery, and the addition of a catalyst is expected to affect its pyrolysis behavior. In the present study, Fe/Al-pillared bentonite with various Fe/Al ratios as pyrolysis catalyst is prepared and characterized by XRD, N2 adsorption, and NH3-TPD. The integration of Al and Fe in the bentonite interlayers to form pillared clay is evidenced by increase in the basal spacing. As a result, a critical ratio of Fe/Al exists in the Fe/Al-pillared bentonite catalytic pyrolysis for oil recovery from the sludge. The oil yield increases with respect to increase in Fe/Al ratio of catalysts, then decreases with further increasing of Fe/Al ratio. The optimum oil yield using 2.0 wt% of Fe/Al 0.5-pillared bentonite as catalyst attains to 52.46% compared to 29.23% without catalyst addition in the present study. In addition, the addition of Fe/Al-pillared bentonite catalyst also improves the quality of pyrolysis-produced oil and promotes the formation of CH4. Fe/Al-pillared bentonite provides acid center in the inner surface, which is beneficial to the cracking reaction of oil molecules in pyrolysis process. The present work implies that Fe/Al-pillared bentonite as addictive holds great potential in industrial pyrolysis of oily sludge.

  14. Evolution of the bentonite barrier under glacial meltwater intrusion conditions

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, T.; Bouby, M. [Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen (Germany). Inst. for Nuclear Waste Disposal (INE); Blechschmidt, I. [NAGRA National Cooperation Disposal Radioactive Waste, Wettingen (Switzerland); and others

    2015-07-01

    Recent safety assessments for repository concepts that combine a clay engineered barrier system (EBS) with a fractured rock have shown that melt water intrusion may have a direct impact on the EBS barrier function in two aspects: - Generation of colloids may degrade the engineered barrier - Colloid transport of radionuclides may reduce the efficiency of the natural barrier The studies presented here are performed in the framework of the Federal Ministry of Economic Affairs and Energy (BMWi) KIT/GRS project KOLLORADO-e, the EU collaborative project CP BELBaR (www.skb.se/belbar) and especially within the Colloid Formation and Migration (CFM) project at the Grimsel Test Site, GTS (www.grimsel.com). Key research areas are (a) the erosion of the bentonite buffer, (b) clay colloid stability and (c) colloid-radionuclide- host rock surface interactions. Concerning bentonite buffer integrity parameters like the bentonite type, Na-/Ca-exchangeable cation ratio, compaction density, role of accessory minerals, the fracture aperture size and groundwater chemistry and flow velocity are investigated in order to identify controlling factors, understand the main mechanisms of erosion from the bentonite surface and to quantify the extent of the possible erosion under these different conditions. Clay colloid stability studies are performed under different geochemical conditions. The main objective is to answer the question if colloids formed at the near/far field interface would be stable only if favourable conditions exist and therefore their relevance for radionuclide transport will be strongly dependent on the local geochemical conditions (inorganic cations Na{sup +}, Ca{sup 2+}, Mg{sup 2+}, Al{sup 3+} and organic complexing agents). Finally, the interaction between colloids and radionuclides and the host rock is intensively investigated in order to answer the question, how colloid mobility may be affected by the composition of the host rock, surface roughness and the mechanism of

  15. Characterization of organo-modified bentonite sorbents: The effect of modification conditions on adsorption performance

    Energy Technology Data Exchange (ETDEWEB)

    Parolo, María E., E-mail: maria.parolo@fain.uncoma.edu.ar [Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas (PROBIEN), Facultad de Ingeniería, Universidad Nacional del Comahue, Neuquén 8300 (Argentina); Pettinari, Gisela R. [Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas (PROBIEN), Facultad de Ingeniería, Universidad Nacional del Comahue, Neuquén 8300 (Argentina); Musso, Telma B. [Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas (PROBIEN), Facultad de Ingeniería, Universidad Nacional del Comahue, Neuquén 8300 (Argentina); CONICET, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires (Argentina); Sánchez-Izquierdo, María P.; Fernández, Laura G. [Facultad de Ingeniería, Universidad Nacional del Comahue, Neuquén 8300 (Argentina)

    2014-11-30

    Graphical abstract: - Highlights: • Modification of clay was evaluated by two methods for removing an organic substance. • Surfactant cations and organosilanes were intercalated into the interlayer space. • The hydrophobic surface of adsorbents increased the retention of organic substances. • Clay grafted with vinyltrimethoxysilane showed the highest adsorption for aniline. - Abstract: The organic modification of a natural bentonite was evaluated using two methods: exchanging the interlayer cations by hexadecyltrimethylammonium (HDTMA) and grafting with vinyltrimethoxysilane (VTMS) and γ-methacryloyloxy propyl trimethoxysilane (TMSPMA) on montmorillonite surface. The physicochemical characterization of all materials was made by X-ray diffraction (XRD), IR spectroscopy, thermogravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET) surface area techniques. HDTMA cations and organosilanes were intercalated into the interlayer space of montmorillonite, as deduced from the increase of the basal spacing. IR spectroscopy, TGA and BET area give evidence of successful organic modification. The studies show a decrease in the IR absorption band intensity at 3465 cm{sup −1} with surfactant modification, and also a decrease of mass loss due to adsorbed water observed in two samples: the organoclay and functionalized bentonites, which are evidences of a lower interlayer hydrophilicity. The efficiency of aniline removal onto natural bentonite, organobentonite and functionalized bentonites from aqueous solutions was evaluated. Aniline sorption on natural bentonite was studied using batch experiments, XRD and IR spectroscopy. The hydrophobic surface of organobentonite and functionalized bentonites increased the retention capacity for nonionic organic substances such as aniline on bentonites. The sorption properties of modified bentonite, through different modification methods, enhanced the potential industrial applications of bentonites in water decontamination.

  16. Characterization of organo-modified bentonite sorbents: The effect of modification conditions on adsorption performance

    International Nuclear Information System (INIS)

    Parolo, María E.; Pettinari, Gisela R.; Musso, Telma B.; Sánchez-Izquierdo, María P.; Fernández, Laura G.

    2014-01-01

    Graphical abstract: - Highlights: • Modification of clay was evaluated by two methods for removing an organic substance. • Surfactant cations and organosilanes were intercalated into the interlayer space. • The hydrophobic surface of adsorbents increased the retention of organic substances. • Clay grafted with vinyltrimethoxysilane showed the highest adsorption for aniline. - Abstract: The organic modification of a natural bentonite was evaluated using two methods: exchanging the interlayer cations by hexadecyltrimethylammonium (HDTMA) and grafting with vinyltrimethoxysilane (VTMS) and γ-methacryloyloxy propyl trimethoxysilane (TMSPMA) on montmorillonite surface. The physicochemical characterization of all materials was made by X-ray diffraction (XRD), IR spectroscopy, thermogravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET) surface area techniques. HDTMA cations and organosilanes were intercalated into the interlayer space of montmorillonite, as deduced from the increase of the basal spacing. IR spectroscopy, TGA and BET area give evidence of successful organic modification. The studies show a decrease in the IR absorption band intensity at 3465 cm −1 with surfactant modification, and also a decrease of mass loss due to adsorbed water observed in two samples: the organoclay and functionalized bentonites, which are evidences of a lower interlayer hydrophilicity. The efficiency of aniline removal onto natural bentonite, organobentonite and functionalized bentonites from aqueous solutions was evaluated. Aniline sorption on natural bentonite was studied using batch experiments, XRD and IR spectroscopy. The hydrophobic surface of organobentonite and functionalized bentonites increased the retention capacity for nonionic organic substances such as aniline on bentonites. The sorption properties of modified bentonite, through different modification methods, enhanced the potential industrial applications of bentonites in water decontamination

  17. Na-smectite s in the Cala de Tomate bentonite deposit (Spain): a natural analogue of the salinity effect on the bentonite barrier of a rad waste disposal

    Energy Technology Data Exchange (ETDEWEB)

    Perez del Villar, L.; Pelayo, M.; Fernandez, A.M.; Cozar, J.S. [CIEMAT - Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT/DIRE/CEAGP), Madrid (Spain); Delgado, A.; Reyes, E. [Ciencias de la Tierra y Quimica Ambiental Estacion Experimental del Zaidin Dpt., Granada (Spain); Fernandez-Soler, J.M. [Granada Univ., Dpt. de Mineralogia y Petrologia (Spain); Tsige, M. [Facultad de Ciencias Geologicas, Dpt. de Geodinamica, Madrid (Spain)

    2005-07-01

    Within the