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Sample records for bentonite thermo-hydro-mechanical thm

  1. 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

    International Nuclear Information System (INIS)

    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 humidity, and radial

  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

    International Nuclear Information System (INIS)

    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. 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)

    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

  5. 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)

    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

  6. 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)

    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)

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

    International Nuclear Information System (INIS)

    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

  8. 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.

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

    International Nuclear Information System (INIS)

    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 CODEBRIGHT 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

  10. 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

    In this paper we describe the OpenGeoSys (OGS) project, which is a scientific open-source initiative for numerical simulations of thermo-hydro-mechanical/chemical processes in fractured porous media. The basic concept is to provide a flexible numerical framework (using primarily the Finite Element Method (FEM)) for solving multi-field problems in porous and fractured media for applications in geoscience, hydrology and energy conversion. To this purpose OGS is based on an object-oriented (OO) FEM concept including a broad spectrum of interfaces for pre- and post-processing. OGS has been developed since the mid-eighties, has been continuously improved in concept and evolved through Fortran, C, and C++ implementations. The idea behind OGS is to provide an open platform to the scientific community featuring professional software-engineering tools such as platform-independent compiling and automated benchmarking. Comprehensive benchmarking books (Kolditz et al. 2012, 2014) and tutorials (Sachse et al. 2014) are being published. Benchmarking has proven to be a valuable tool for cooperation between different developer teams, for example, for code comparison and validation purposes (DEVOVALEX, CO2 BENCH and SSBENCH projects). The computational efficiency of OO codes is very important in scientific computing (Wang et al. 2009). We have already parallelized the OO codes by using both custom schemes and the PETSc library (Wang et al. 2014). Meanwhile the 6th version, ogs6, is under construction to further foster various parallel computing techniques and to improve code modularity for enhancing collaborative development by several researchers. The code is openly accessible via GitHub (https://github.com/ufz/ogs) and our development workflow extensively builds on Git features such as branching, merging automatic compiling, executing unit tests and code review to improve communication among developers and maintain code quality. OGS also provides a graphical user interface (Data

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

    International Nuclear Information System (INIS)

    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)

  12. Thermo-hydro-mechanical tests of buffer material

    International Nuclear Information System (INIS)

    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/m3 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/m3 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/m3 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/m3 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/m3 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

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

    International Nuclear Information System (INIS)

    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

  14. Thermo-hydro-mechanical processes in fractured rock formations during a glacial advance

    OpenAIRE

    Selvadurai, A. P. S.; Suvorov, A. P.; Selvadurai, P. A.

    2015-01-01

    The paper examines the coupled thermo-hydro-mechanical (THM) processes that develop in a fractured rock region within a fluid-saturated rock mass due to loads imposed by an advancing glacier. This scenario needs to be examined in order to assess the suitability of potential sites for the location of deep geologic repositories for the storage of high-level nuclear waste. The THM processes are examined using a computational multiphysics approach that takes into account thermo-...

  15. Thermo-hydro-mechanical processes in fractured rock formations during glacial advance

    Science.gov (United States)

    Selvadurai, A. P. S.; Suvorov, A. P.; Selvadurai, P. A.

    2014-11-01

    The paper examines the coupled thermo-hydro-mechanical (THM) processes that develop in a fractured rock region within a fluid-saturated rock mass due to loads imposed by an advancing glacier. This scenario needs to be examined in order to assess the suitability of potential sites for the location of deep geologic repositories for the storage of high-level nuclear waste. The THM processes are examined using a computational multiphysics approach that takes into account thermo-poroelasticity of the intact geological formation and the presence of a system of sessile but hydraulically interacting fractures (fracture zones). The modeling considers coupled thermo-hydro-mechanical effects in both the intact rock and the fracture zones due to contact normal stresses and fluid pressure at the base of the advancing glacier. Computational modelling provides an assessment of the role of fractures that can modify the pore pressure generation within the entire rock mass.

  16. Thermo-hydro-mechanical processes in fractured rock formations during a glacial advance

    Science.gov (United States)

    Selvadurai, A. P. S.; Suvorov, A. P.; Selvadurai, P. A.

    2015-07-01

    The paper examines the coupled thermo-hydro-mechanical (THM) processes that develop in a fractured rock region within a fluid-saturated rock mass due to loads imposed by an advancing glacier. This scenario needs to be examined in order to assess the suitability of potential sites for the location of deep geologic repositories for the storage of high-level nuclear waste. The THM processes are examined using a computational multiphysics approach that takes into account thermo-poroelasticity of the intact geological formation and the presence of a system of sessile but hydraulically interacting fractures (fracture zones). The modelling considers coupled thermo-hydro-mechanical effects in both the intact rock and the fracture zones due to contact normal stresses and fluid pressure at the base of the advancing glacier. Computational modelling provides an assessment of the role of fractures in modifying the pore pressure generation within the entire rock mass.

  17. Thermo-Hydro-Mechanical properties of MX-80. Results from advanced laboratory tests

    Energy Technology Data Exchange (ETDEWEB)

    Dueck, Ann; Nilsson, Ulf (Clay Technology AB, Lund (Sweden))

    2010-12-15

    General Highly compacted bentonite is proposed as the buffer material in the Swedish concept for disposal of nuclear waste. The saturated homogenized bentonite is expected to fully act as a buffer material between the waste canister and the surrounding bedrock. Material models describing the thermo-hydro-mechanical (THM) behaviour of the buffer material have been created with the purpose to simulate and predict the behaviour in a repository both before and after water saturation. The material models of water saturated and water unsaturated buffer material are complicated and contain a number of parameters that need to be determined. The present report is a compilation of results concerning thermo-hydro-mechanical laboratory tests on saturated and unsaturated buffer material. The main purpose of the report is to supply modelling groups with available results for improving models and determine parameters that can be used for the THM modelling of the behaviour of the buffer.Retention curves The relation between water content and relative humidity has been determined in a number of test series for some specific conditions, e.g. different initial water contents. Two methods have been used; the sorption balance method and a method with jars as desiccators. The majority of the results were derived from tests where RH was controlled and the response of the bentonite samples was measured. The results are given as water content versus relative humidity in diagrams and in tabular form. Volume change The volume change of water unsaturated bentonite specimens has been investigated by compression tests and swelling/shrinkage tests for some specific stress and moisture paths. The constant relative humidity was generated by the vapour equilibrium technique combined with an air circulation system. Measured stresses, deformation and relative humidity are presented versus time in diagrams and the final values at different stages are also presented in tabular form. Moisture transport

  18. A multiphase thermo-hydro-mechanical model for concrete at high temperatures : Finite element implementation and validation under LOCA load

    OpenAIRE

    DAL PONT, S; Durand, S; SCHREFLER, BA

    2007-01-01

    The aim of this paper is to study the thermo-hydraulic behavior of concrete subjected to severe loading conditions, such as those typical of nuclear waste storage structures and pressurized water reactors (PWR's) vessels in accidental conditions. The paper presents a coupled thermo-hydro-mechanical (THM) model for the description of concrete at high temperatures. The model is characterized by the presence of a deformable solid matrix (linearly elastic) filled with three fluid phases (liquid w...

  19. Thermo-hydro-mechanical behavior of argillite

    International Nuclear Information System (INIS)

    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

  20. Bentonite THM behaviour mock-up studies

    International Nuclear Information System (INIS)

    Nuclear waste disposal rely on multi-barrier system. Engineered Barrier Systems make use of swelling clay buffer set in place unsaturated in deposition hole. After waste emplacement, buffer hydrates and swells, being submitted to the heat from nuclear waste decay. In order to characterize the THM behaviour of swelling clays under temperatures exceeding 100 C, Andra has gathered research laboratories, CEA/LECBA, Eurogeomat and EDF/CPM to conduct experimental a d modelling studies. The analysis of the state of art led to the definition of mock-up tests to evaluate effects of high temperatures and high thermal gradients on the heat and mass transfer, and the stress-strain behaviour of initially unsaturated MX80 bentonite during a thermal loading at constant volume for both closed and opened system. This paper presents the first mock-up tests and their experimental result. (authors)

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

    International Nuclear Information System (INIS)

    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. Thermo-hydro-mechanical behaviour of Boom clay

    International Nuclear Information System (INIS)

    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)

  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)

    , 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/cm3. 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 m2 range. In the case that the intrinsic permeability of rock mass is approximately 10-15 m2, 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 result

  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. Excavation effect on thermo hydro- mechanical behaviour of geological barrier

    International Nuclear Information System (INIS)

    Heat emitted by nuclear waste has great influences on mechanical and hydraulic properties of the surrounded media and also on the movement of water, vapour and air. Due to the complexity of the phenomena that might take place in a waste repository, an adequate understanding of the behaviour of the barriers is not an easy task. The difficulty of the task is increased by the fact that many effect s are coupled. In order to study these effects, series of coupled thermo-hydro-mechanical formulations are used. The first step in a theoretical development of a fully coupled thermo-hydro-mechanical model for an unsaturated soil, is choosing the adequate and independent variables which would be able to present all significant interaction effects among the different components involved in a coupled process in a deformable unsaturated porous medium with three phases (skeleton, water and air)under heating. The phase changes between liquid and gas, evaporation, condensation, induced moisture transfer under thermal and pore pressure gradients and the effects of moisture distribution on the heat flow are important aspects in non-deformable unsaturated porous media. If the deformation of porous media is considered, the coupling effects among deformation, moisture, and heat should be also regarded in addition to all above aspects. The governing equations are the equation of equilibrium and constitutive law for solid skeleton, mass conservation and fluid transfer for water and air, and Fourier law and conservation equation for energy. Due to the fact that water phase consists of liquid and vapour two sets of transfer equations are used for water phase: Philip and de Vries law for vapour and Darcy law for liquid. Darcy law is also used for air transfer. In the presented formulations, due to the fact that the medium is assumed to be deformable, the effects of deformation on the temperature and suction distribution in soil and the inverse effects must be included. In order to include

  7. 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.

  8. Coupled thermo-hydro-mechanical experiment at Kamaishi Mine. Technical note 16-99-03. Analyses of Task 2C, DECOVALEX II

    International Nuclear Information System (INIS)

    It is an important part of the near field performance assesment 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. The coupled T-H-M experiment is one of tasks in DECOVALEX (DEvelopment of COupled models and their VALidation against EXperiments) project which is an international co-operative project and it is defined as Task 2. The Task 2 for the DECOVALEX project are divided into three subtasks (A-C) in accordance with the programme and availability of data, called subtasks. This note describes the results of subtask C. Subtask C is a coupled thermo-hydro-mechanical analysis in the near field. (author)

  9. Thermo-hydro-mechanical modeling and analysis of cement-based energy storages for small-scale dwellings

    Science.gov (United States)

    Hailemariam, Henok; Wuttke, Frank

    2016-04-01

    One of the common technologies for balancing the energy demand and supply in district heating, domestic hot water production, thermal power plants and thermal process industries in general is thermal energy storage. Thermal energy storage, in particular sensible heat storage as compared to latent heat storage and thermo-chemical storage, has recently gained much interest in the renewable energy storage sector due to its comparatively low cost and technical development. Sensible heat storages work on the principle of storing thermal energy by raising or lowering the temperature of liquid (commonly water) or solid media, and do not involve material phase change or conversion of thermal energy by chemical reactions or adsorption processes as in latent heat and thermo-chemical storages, respectively. In this study, the coupled thermo-hydro-mechanical behaviour of a cement-based thermal energy storage system for domestic applications has been modeled in both saturated as well as unsaturated conditions using the Finite Element method along with an extensive experimental analysis program for parameter detection. For this purpose, a prototype model is used with three well-known thermal energy storage materials, and the temperature and heat distribution of the system were investigated under specific thermo-hydro-mechanical conditions. Thermal energy samples with controlled water to solids ratio and stored in water for up to 28 days were used for the experimental program. The determination of parameters included: thermal conductivity, specific heat capacity and linear coefficient of thermal expansion (CTE) using a transient line-source measurement technique as well as a steady-state thermal conductivity and expansion meter; mechanical strength parameters such as uni-axial strength, young's modulus of elasticity, poisson's ratio and shear parameters using uniaxial, oedometer and triaxial tests; and hydraulic properties such as hydraulic permeability or conductivity under

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

    International Nuclear Information System (INIS)

    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)

  11. Rheological numerical simulation for thermo-hydro-mechanical coupling analysis for rock mass

    Institute of Scientific and Technical Information of China (English)

    WANG Zhi-yin; XU Jie; LI Yun-peng; GUO Shu-tai; AI Chuan-zhi

    2007-01-01

    Under the environment of seepage field, stress field and temperature field interaction and influence, the three fields will not only produce coupling effect, but also have deformation with time due to the rheological behavior of rock mass. In the paper, based on the fundamental theories of rock mass coupling theory and rheological mechanics, the rheological model for fully coupled thermo-hydro-mechanical analysis for rock mass was set up, and the corresponding constitutive relationship, the conservation equation of mass and the conservation equation of energy were given, and the finite element formulas were derived for coupling analysis of rock mass. During establishing governing equations, rock mass was assumed approximately as macro-equivalent continuum medium. The obtained rheological numerical model for fully coupled thermo-hydro-mechanical analysis can be used for analyzing and predicting the long-term stability of underground caverns and slope engineering under the condition of thermo-hydro-mechanical coupling with rheological deformation.

  12. Behaviour of high performance concrete under high temperature (60-450 deg C) for surface long-term storage: thermo-hydro-mechanical residual properties

    International Nuclear Information System (INIS)

    After various thermal treatments (up to 450 deg C), residual thermo-hydro-mechanical (T-H-M) properties of two OPC high performance concretes (HPC) were analyzed in the context of surface long-term storage. Materials were prepared with silico-calcareous aggregates (standard HPC) and hematite aggregates (heavy HPC). The initial micro structural (porosity =10%) and transport (gas permeability ∼ 10-19 m2) properties are similar for both concretes. As far as the mechanical aspect is concerned, heavy HPC shows a higher compressive strength and elastic modulus than standard HPC (78 and 63 MPa, 81 and 49 GPa, respectively). Heavy HPC is also characterized by a higher thermal conductivity (7.3 W m-1 K-1 compared to 2.7 W m-1 K-1 for standard concrete). Results analysis show that thermo-hydro-mechanical damages are smaller for heavy HPC. Between 60 and 250 deg C, the elastic modulus and the compressive strength of standard HPC decrease by 40% and 16%, respectively. For heavy HPC, these parameters respectively decrease by 10% and 4% A similar trend was observed for thermal conductivity evolution. Gas permeability and porosity data confirm the good behavior of heavy HPC. As a conclusion, hematite HPC seems to provide more interesting T-H-M residual properties than standard HPC. Limited thermal expansion and thermal gradients induced by hematite are probably responsible of this behavior. Copyright (2001) Material Research Society

  13. 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.

  14. 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)

    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

  15. Study of thermo-hydro-mechanical processes at a potential site of an Indian nuclear waste repository

    Science.gov (United States)

    Maheshwar, Sachin; Verma, A. K.; Singh, T. N.; Bajpai, R. K.

    2015-12-01

    A detailed scientific study is required for the disposal of high-level radioactive wastes because they generate extremely high heat during their half-life period. Although, several methods have been proposed for the disposal of nuclear wastes, deep underground repository is considered to be a suitable option. In this paper, field investigation has been done near to Bhima basin of peninsular India. Detailed fracture analysis near the borehole shows very prominent maxima of fractures striking N55∘E coinciding with the trace of master basement cover metasediment fault. Physico-mechanical properties of rocks have been determined in the laboratory. The host rock chosen is granite and engineered barrier near the canister is proposed to be clay. A thermo-hydro-mechanical (THM) analysis has been done to study the effect of heat on deformations, stresses and pore-pressure variation in granite and clay barriers. For this purpose, finite difference method has been used. Suitable rheological models have been used to model elastic canister and elasto-plastic engineered barrier and host rock. It has been found that both temperature and stresses at any point in the rockmass is below the design criteria which are 100∘C for temperature and 0.2 for damage number.

  16. Study of thermo-hydro-mechanical processes at a potential site of an Indian nuclear waste repository

    International Nuclear Information System (INIS)

    A detailed scientific study is required for the disposal of high-level radioactive wastes because they generate extremely high heat during their half-life period. Although, several methods have been proposed for the disposal of nuclear wastes, deep underground repository is considered to be a suitable option. In this paper, field investigation has been done near to Bhima basin of peninsular India. Detailed fracture analysis near the borehole shows very prominent maxima of fractures striking N55°E coinciding with the trace of master basement cover metasediment fault. Physico-mechanical properties of rocks have been determined in the laboratory. The host rock chosen is granite and engineered barrier near the canister is proposed to be clay. A thermo-hydro-mechanical (THM) analysis has been done to study the effect of heat on deformations, stresses and pore-pressure variation in granite and clay barriers. For this purpose, finite difference method has been used. Suitable rheological models have been used to model elastic canister and elasto-plastic engineered barrier and host rock. It has been found that both temperature and stresses at any point in the rockmass is below the design criteria which are 100°C for temperature and 0.2 for damage number. (author)

  17. Study of thermo-hydro-mechanical processes at a potential site of an Indian nuclear waste repository

    Indian Academy of Sciences (India)

    Sachin Maheshwar; A K Verma; T N Singh; R K Bajpai

    2015-12-01

    A detailed scientific study is required for the disposal of high-level radioactive wastes because they generate extremely high heat during their half-life period. Although, several methods have been proposed for the disposal of nuclear wastes, deep underground repository is considered to be a suitable option. In this paper, field investigation has been done near to Bhima basin of peninsular India. Detailed fracture analysis near the borehole shows very prominent maxima of fractures striking N55°E coinciding with the trace of master basement cover metasediment fault. Physico-mechanical properties of rocks have been determined in the laboratory. The host rock chosen is granite and engineered barrier near the canister is proposed to be clay. A thermo-hydro-mechanical (THM) analysis has been done to study the effect of heat on deformations, stresses and pore-pressure variation in granite and clay barriers. For this purpose, finite difference method has been used. Suitable rheological models have been used to model elastic canister and elasto-plastic engineered barrier and host rock. It has been found that both temperature and stresses at any point in the rockmass is below the design criteria which are 100°C for temperature and 0.2 for damage number.

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

    International Nuclear Information System (INIS)

    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

  19. A multiphase thermo-hydro-mechanical model for concrete at high temperatures-Finite element implementation and validation under LOCA load

    International Nuclear Information System (INIS)

    The aim of this paper is to study the thermo-hydraulic behavior of concrete subjected to severe loading conditions, such as those typical of nuclear waste storage structures and pressurized water reactors (PWR's) vessels in accidental conditions. The paper presents a coupled thermo-hydro-mechanical (THM) model for the description of concrete at high temperatures. The model is characterized by the presence of a deformable solid matrix (linearly elastic) filled with three fluid phases (liquid water, vapour water and dry air) and has been implemented in a finite element code freely available for research purposes (CAST3M) developed by the French research center for nuclear energy (CEA). The code has been validated by means of some case tests and has been finally applied for the prediction of the thermo-hydraulic conditions in a concrete slab submitted to a loss-of-coolant accident (LOCA) load

  20. Study of radioactive waste disposal possibilities in geologic formations: thermo-hydro-mechanical (THM) experience

    International Nuclear Information System (INIS)

    A simulation test of heat release and of the mechanical effects generated by deep disposal of reprocessing waste (long-lived, high-level radioactivity) was carried out in an abandoned uranium mine at Tenelles, in the Fanay-Augeres area (15 km north of Limoges). The experimental conditions are described and the main results are presented

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

    International Nuclear Information System (INIS)

    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 600C. 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

  2. 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)

    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)

  3. Coupled thermo-hydro-mechanical experiment at Kamaishi Mine technical note 14-99-01. Verification of the buffer material emplacement technique

    International Nuclear Information System (INIS)

    It is an important part of the near field performance assessment of nuclear waste disposal to evaluate coupled thermo-hydromechanical (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' was conducted at the Kamaishi Mine, in which the 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. This report summarizes the results of the in-situ direct compaction technique to evaluate the appropriate conditions for this technique. The in-situ direct compaction technique is one of the major candidate emplacement techniques for the buffer material. This experiment consisted of the mock-up tests and the in-situ test. The mock-up tests showed the appropriate conditions for the in-situ direct compaction technique. For the in-situ experiment, the manufactured OT-9607 achieved dry density averaged 1.65 g/cm3, which matched the demand for the thermo-hydro-mechanical experiment. (author)

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

    International Nuclear Information System (INIS)

    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

  5. 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)

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

    International Nuclear Information System (INIS)

    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

  7. Contribution to the study of mechanical and thermo-hydro-mechanical behaviour of Callovo-Oxfordian argillites. Application to radioactive waste storage

    International Nuclear Information System (INIS)

    This Habilitation thesis presents a synthesis of the different mechanical and thermo-hydro-mechanical coupled aspects of rocks and in particular it deals with a)the phenomena and processes coupled with mechanics in a storage (ch 1); b)the behavior of argillites under thermal, mechanical and coupled hydro-mechanical and thermo-hydro-mechanical solicitations (ch 2 to 4); c)the rheological models and the argillites behavior simulations (ch 5). (O.M.)

  8. 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)

    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

  9. A Thermo-Hydro-Mechanical modeling of fracture opening and closing due heat extraction from geothermal reservoir

    Science.gov (United States)

    Nand Pandey, Sachchida; Chaudhuri, Abhijit; Kelkar, Sharad

    2015-04-01

    Increasing the carbon dioxide concentration in atmosphere become challenging task for the scientific community. To achieve the sustainable growth with minimum pollution in atmosphere requires the development of low carbon technology or switch towards renewable energy. Geothermal energy is one of the promising source of clean energy. Geothermal energy is also considered a sustainable, reliable and least-expensive. This study presents a numerical modeling of subsurface heat extraction from the reservoir. The combine flow, heat transfer and geo-mechanical problem are modeled using FEHM code, which was validated against existing field data, numerical code and commercial software. In FEHM the flow and heat transfer in reservoir are solved by control volume method while for mechanical deformation finite element technique is used. The 3-D computational domain (230m × 200m × 1000m) has single horizontal fault/fracture, which is located at 800 m depth from the ground surface. The fracture connects the injection and production wells. The distance between the wells is 100 m. A geothermal gradient 0.08 °C/m is considered. The temperatures at top and bottom boundaries are held fixed as 20 and 100 °C respectively. The zero heat and mass flux boundary conditions are imposed to all vertical side boundaries of the domain. The simulation results for 100 days suggests that the computational domain is sufficiently large as the temperature along the vertical boundaries are not affected by cold-water injection. To model the thermo-poro-elastic deformation, zero all three components of displacement are specified as zero at the bottom. The zero stress condition along all other boundaries allows the boundaries to move freely. The temperature and pressure dependent fluid properties such as density and viscosity with single phase flow in saturated medium is considered. We performed a series of thermo-hydro-mechanical (THM) simulations to show aperture alteration due to cold

  10. 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)

    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

  11. A thermo-hydro-mechanical coupled model in local thermal non-equilibrium for fractured HDR reservoir with double porosity

    Science.gov (United States)

    Gelet, R.; Loret, B.; Khalili, N.

    2012-07-01

    The constitutive thermo-hydro-mechanical equations of fractured media are embodied in the theory of mixtures applied to three-phase poroelastic media. The solid skeleton contains two distinct cavities filled with the same fluid. Each of the three phases is endowed with its own temperature. The constitutive relations governing the thermomechanical behavior, generalized diffusion and transfer are structured by, and satisfy, the dissipation inequality. The cavities exchange both mass and energy. Mass exchanges are driven by the jump in scaled chemical potential, and energy exchanges by the jump in coldness. The finite element approximation uses the displacement vector, the two fluid pressures and the three temperatures as primary variables. It is used to analyze a generic hot dry rock geothermal reservoir. Three parameters of the model are calibrated from the thermal outputs of Fenton Hill and Rosemanowes HDR reservoirs. The calibrated model is next applied to simulate circulation tests at the Fenton Hill HDR reservoir. The finer thermo-hydro-mechanical response provided by the dual porosity model with respect to a single porosity model is highlighted in a parameter analysis. Emphasis is put on the influence of the fracture spacing, on the effective stress response and on the permeation of the fluid into the porous blocks. The dual porosity model yields a thermally induced effective stress that is less tensile compared with the single porosity response. This effect becomes significant for large fracture spacings. In agreement with field data, fluid loss is observed to be high initially and to decrease with time.

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

    International Nuclear Information System (INIS)

    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

  13. Finite element method for simulating coupled thermo-hydro-mechanical processes in discretely fractured porous media and application to enhanced geothermal reservoir analysis

    Science.gov (United States)

    Watanabe, N.; Wong, L.; Bloecher, G.; Cacace, M.; Kolditz, O.

    2012-12-01

    We present our recent development of the finite element method (FEM) for simulating coupled thermo-hydro-mechanical (THM) processes in discretely fractured porous media and an application to geothermal reservoir modeling for the research test site Gross Schoenebeck in Germany operated by the GFZ German Research Centre for Geosciences. Numerical analysis of multi-physics problems in fractured rocks is important for various geotechnical applications. In particular for enhanced geothermal reservoirs where induced fractures and possibly natural fault systems dominate the system behavior, explicit modeling of those characteristic fractures (i.e. discrete fracture models) is essential to get more detailed understanding of in-situ processes and reliable estimations of heat extraction from those deep reservoirs. However, as fractures are mechanical discontinuities, it is difficult to solve the problems using continuity based numerical methods such as the FEM. Currently, equivalent porous medium or multiple continuum model approaches are often only the way to model fractured rocks with the FEM. The authors have recently developed lower-dimensional interface elements (LIEs) for modeling mechanics-involved coupled processes with pre-existing fractures (Watanabe et al. 2012 IJNME). The method does not require any double nodes unlike conventional interface elements. Moreover, for coupled problems, the approach allows for the use of a single mesh for both mechanical and other related processes such as flow and transport. All the code developments have been carried out within the scientific open source project OpenGeoSys (www.opengeosys.net) (Kolditz et al. 2012 EES). Using both traditional and new simulation techniques, a geothermal reservoir model for the research test site Gross Schoenebeck has been developed. Unstructured meshing of the complex faulted reservoir including both rock matrix and fracture elements has been conducted using recently developed automatic

  14. 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.

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

    International Nuclear Information System (INIS)

    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 FEMLABR, 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)

  16. Thermo-hydro-mechanical coupled analysis for an in-situ heating test in sedimentary soft rock

    International Nuclear Information System (INIS)

    Soft rock is expected to be one of the potential host rocks for the geological disposal of radioactive waste. An in-situ heating test was conducted in order to establish an evaluation method of long-term stability of caverns in soft rocks. Thermo-hydro-mechanical coupled analysis for the heating test was also conducted. The comparison between numerical results and measurement when the temperature of heater was finally set as 90degC is reported in this paper. Deformation of soft rock during the heating test was able to be broadly reproduced by numerical model considering linear elasticity and thermal expansion with the exception of the displacement pattern of the heater wall and the smaller vertical strains. (author)

  17. 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)

  18. An elastoplastic model for the THM analysis of freezing soils

    OpenAIRE

    Satoshi,Nishimura; Gens Solé, Antonio; Olivella Pastallé, Sebastià; Jardine, Richard

    2009-01-01

    By employing a combination of ice pressure, liquid pressure and total stress as state variables, a new thermoplastic constitutive model has been developed that encompasses frozen and unfrozen behaviour within a unified effective-stress-based framework. It has been incorporated into a fully coupled thermo-hydro-mechanical (THM) finite element formulation that considers freezing and thawing in water-saturated soils and applied to a large-scale pipeline frost heave test. Peer Reviewed

  19. Simulations of the thermo-hydro-mechanical behaviour of an annular reinforced concrete structure heated up to 200 C

    International Nuclear Information System (INIS)

    We analyze in this study the numerical thermo-hydro-mechanical response of an annular reinforced concrete structure called MAQBETH subjected to a thermal loading up to 200 degrees C during more than 250 h. This mock-up is typical of concrete structures in nuclear waste storage conditions under accidental situations. The simulations are performed with a simplified coupled model based on the mechanics of partially saturated porous media, which was previously developed. As a main contribution of this paper, we explicitly take into account the temperature effects in the water retention curves, via the introduction of the isosteric heat of sorption. These effects result in a significant reduction of the saturation degree at any given relative humidity for increasing temperatures. The numerical results of the MAQBETH simulation are then compared with experimental ones in terms of profiles of temperature, relative humidity, gas pressures and strains in the median plan at different times. This comparison shows a reasonable agreement. The effects of the temperature-dependent sorption curves are further analyzed through additional simulations carried out with a constant sorption curve. Large differences in the relative humidity and saturation degree profiles, and to a lesser extent in the gas pressure profiles, are observed between the two cases. (authors)

  20. 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.

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

    International Nuclear Information System (INIS)

    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

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

    International Nuclear Information System (INIS)

    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)

  3. The international DECOVALEX project for the modelling of coupled Thermo-Hydro-Mechanical processes in a nuclear waste repository. The Finnish contribution during 1991-1995

    International Nuclear Information System (INIS)

    During the years 1991-1995, an international effort was going on in order to study the coupled thermo-hydro-mechanical effects in the water containing rock mass caused by the heat generation of spent fuel canisters in a repository. The project was named DECOVALEX which is an acronym of the words 'an international co-operative project for the DEvelopment of COupled models and their VALidation agaist EXperiments in nuclear waste isolation'. The Finnish Centre for Radiation and Nuclear Safety (STUK) was one of the nine funding organizations in the international project. STUK's research team was the Road, Traffic, and Geotechnical Laboratory of the Technical Research Centre of Finland (VTT). After the change in the VTT's organization the research team was from Communities and Infrastructure. To support the Finnish contribution in the international project, a National DECOVALEX Group was established January 16, 1992 under the leadership of STUK. The group consisted of research and funding organizations as well as others interested in the problematics. The Finnish contribution was concentrated on three topics. Bench Mark Tests 2 and 3 were those suggested by the international project. In addition to these, there was a thermo-hydro-mechanical experiment carried out at the Helsinki University of Technology. The data were gotten from the hydro-mechanical part of the test. The thermal part was postponed. All the material presented in this report has been documented and published elsewhere. So, the aim of this report is only to be a summary. (orig.)

  4. Coupled THM analysis of a nuclear waste repository in crystalline rock

    OpenAIRE

    Sanchez, Marcelo Dolores; Dontha, L; Gens Solé, Antonio; Guimarães, Leonardo do N

    2013-01-01

    This paper presents the Thermo-Hydro-Mechanical (THM) analysis of an isolation system for high level nuclear waste. A geological disposal facility of such type encompasses both: natural (host rock) and engineered barriers (generally clay based). The study deals on an ongoing large scale heating test at full scale that is being carried at the Grimsel test site under actual conditions. The experiment reproduces the conditions of a HLW repository, at full scale under actual conditions. Key therm...

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

    International Nuclear Information System (INIS)

    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

  6. 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)

    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)

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

    International Nuclear Information System (INIS)

    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 in the

  8. 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.;

    -eighties and has been continuously developed in concept and software implementations evolved through FORTRAN, C, and C++. The idea behind OGS is to provide an open platform to the community, outfitted with professional software-engineering tools such as platform-independent compiling and automated benchmarking...

  9. 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)

    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

  10. THERMO-HYDRO-MECHANICAL MODELING OF WORKING FLUID INJECTION AND THERMAL ENERGY EXTRACTION IN EGS FRACTURES AND ROCK MATRIX

    Energy Technology Data Exchange (ETDEWEB)

    Robert Podgorney; Chuan Lu; Hai Huang

    2012-01-01

    Development of enhanced geothermal systems (EGS) will require creation of a reservoir of sufficient volume to enable commercial-scale heat transfer from the reservoir rocks to the working fluid. A key assumption associated with reservoir creation/stimulation is that sufficient rock volumes can be hydraulically fractured via both tensile and shear failure, and more importantly by reactivation of naturally existing fractures (by shearing), to create the reservoir. The advancement of EGS greatly depends on our understanding of the dynamics of the intimately coupled rock-fracture-fluid-heat system and our ability to reliably predict how reservoirs behave under stimulation and production. Reliable performance predictions of EGS reservoirs require accurate and robust modeling for strongly coupled thermal-hydrological-mechanical (THM) processes. Conventionally, these types of problems have been solved using operator-splitting methods, usually by coupling a subsurface flow and heat transport simulators with a solid mechanics simulator via input files. An alternative approach is to solve the system of nonlinear partial differential equations that govern multiphase fluid flow, heat transport, and rock mechanics simultaneously, using a fully coupled, fully implicit solution procedure, in which all solution variables (pressure, enthalpy, and rock displacement fields) are solved simultaneously. This paper describes numerical simulations used to investigate the poro- and thermal- elastic effects of working fluid injection and thermal energy extraction on the properties of the fractures and rock matrix of a hypothetical EGS reservoir, using a novel simulation software FALCON (Podgorney et al., 2011), a finite element based simulator solving fully coupled multiphase fluid flow, heat transport, rock deformation, and fracturing using a global implicit approach. Investigations are also conducted on how these poro- and thermal-elastic effects are related to fracture permeability

  11. Development of numerical model on the coupled thermo-hydro-mechanical-chemical process for the assessment methodology of chemical effects in the buffer material

    International Nuclear Information System (INIS)

    Numerical model which is mainly paid attention on chemical effects in the buffer material has been developed, for the purpose of quantification of the early complex evolution on the coupled thermo-hydro-mechanical-chemical processes in the near-field of a HLW repository. In this paper, governing equations are described, considering heat flow, fluid flow, mass transport and a variety of chemical reactions such as mineral dissolution/precipitation, gas dissolution/exsolution, ion-exchange and surface complexation. And also limitations are described. Through the comparison analysis against another coupled model, TOUGHREACT which has been developed in the Lawrence Berkeley National Laboratory, propriety of our coupled modeling and uncertainties between models are shown. And also designed laboratory tests for the salt accumulation/precipitation are presented. As the result of verification analysis against experimental salt concentration data, the almost distribution of saturation, temperature and concentration of aqueous species and minerals in the buffer material agree. This result suggests chemical effects such as salt accumulation/precipitation is able to simulate using our numerical model. Moreover, using the geological environment data based on the existing investigation in the Horonobe Underground Research Laboratory Project, simulation on chemical changes in the near-field involving the radioactive decay heat arising from the vitrified waste and infiltration of ground water into the buffer material is also presented. (author)

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

    International Nuclear Information System (INIS)

    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

  13. Temperature Buffer Test. Final THM modelling

    International Nuclear Information System (INIS)

    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, CodeBright and Abaqus, have been used. The modelling performed by UPC-Cimne using CodeBright, 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 convergence

  14. 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

  15. Thermo-Hydro-Mechanical Evolution of Transport Properties in Porous Media: From Laboratory to the Groß-Schönebeck Geothermal Reservoir.

    Science.gov (United States)

    Jacquey, Antoine; Cacace, Mauro; Blöcher, Guido; Watanabe, Norihiro; Scheck-Wenderoth, Magadalena

    2015-04-01

    simulations to experimental results. It is then possible to constrain some parameters involved in these porosity formulations. One formulation with T-M coupling is also investigated (Ghabezloo et al. 2008) which is based on thermoelasticity and a fluid volume balance. Then, this theoretical background has been applied to the field scale to study the performance of the Groß-Schönebeck geothermal reservoir situated in the North-East German Basin. Current results on numerical simulations of Thermo-Hydro-Mechanical coupled processes involving transport properties evolution will be presented.

  16. Thermomechanics of swelling unsaturated porous media. Compacted bentonite clay in spent fuel disposal

    International Nuclear Information System (INIS)

    A barrier of compacted bentonite clay is planned to be used in geological disposal of spent nuclear fuel. In addition to providing mechanical stability to the waste containers the barrier is supposed to prevent or delay the movement of groundwater and the consequential transport of radionuclides from the repository. Fluid flow, phase changes, mechanical behavior of the buffer, rock, and the containers, and the heat produced by the radioactive waste constitute a coupled thermo-hydro-mechanical (THM) system. The objective of the thesis is to model the coupled THM behaviour of the bentonite buffer. For this purpose a general thermomechanical and mixture theoretical model is derived and applied to the fully coupled THM description of swelling compacted bentonite. The particular form of the free energy of the system is chosen to take into account interactions of the mixture components, namely, mixing of the gaseous components (water vapor and air) and adsorption and swelling interactions between the liquid water and the solid skeleton. The mechanical part of the model is limited to reversible behavior within the limit of small strains. Numerical implementation is done with the multi-purpose finite element method software ELMER. The model is applied to various coupled experiments: two kinds of laboratory scale tests for Febex bentonite, larger scale mock-up and in-situ tests for Febex bentonite, and to three kinds of laboratory scale experiments for MX-80 bentonite. In addition, a brief consideration of the difference of the large scale Febex experiments and the real disposal situation is done by incorporating more realistic temperature evolutions of the containers. The inclusion of the mixing interaction yields Clausius-Clapeyron equations which are valid both for the total pressure (i.e. the boiling pressure) and for the partial pressure of saturated vapor. Additionally, together with an appropriate dissipation function the mixing interaction yields a common form of

  17. Model and code development for numerical experiments on the coupled thermo-hydro-mechanical and chemical processes in the near-field of a high-level radioactive waste repository

    International Nuclear Information System (INIS)

    The expected processes in the near-field of a high-level radioactive waste (HLW) repository after emplacement of engineered barrier system (EBS) are the coupled processes among radioactive decay heat from vitrified waste, infiltration of groundwater into buffer material, swelling pressure of buffer material due to saturation, and chemical reaction between EBS material and porewater. After the second progress report on research and development for the geological disposal of HLW in Japan (H12 report), Japan Nuclear Cycle Development Institute has initiated the model and code development for numerical experiments on the coupled thermo-hydro-mechanical and chemical (THMC) processes, in order to understand and predict the near-field long-term evolution. The focal point of this research is to predict (1) near-field chemistry for overpack corrosion and radionuclide migration; and (2) near-field long-term integrity by chemical degradation. This report presents the status and future activities on the model and code development for numerical experiments on the coupled THMC processes in the near-field of a HLW repository. (author)

  18. 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

  19. 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. Final Report

    International Nuclear Information System (INIS)

    , Germany, Japan, and USA-predicted the long-term THM and THC processes in two generic geologic repositories for radioactive waste, with the goal of determining the impact of geomechanical and geochemical processes on hydrologic properties and flow patterns. The two repositories are simplified representations of possible repository sites and emplacement conditions considered by participating countries. One repository is 'located' in saturated crystalline rock, with the waste packages emplaced into tunnels backfilled with a bentonite buffer material (Febex type). The other repository is a simplified model of the Yucca Mountain; Nevada, site (Yucca Mountain type), featuring a deep and unsaturated volcanic rock formation with emplacement in open tunnels. While different conceptual approaches and various numerical simulators were used to predict the future conditions in these repositories, a good agreement was obtained between the respective predictions. This provides valuable supporting evidence that the relevant coupled processes are well understood and that reliable modeling approaches are available

  20. THM modelling of hydrothermal circulation in deep geothermal reservoirs

    Science.gov (United States)

    Magnenet, Vincent; Fond, Christophe; Schmittbuhl, Jean; Genter, Albert

    2014-05-01

    Numerous models have been developped for describing deep geothermal reservoirs. Using the opensource finite element software ASTER developped by EDF R&D, we carried out 2D simulations of the hydrothermal circulation in the deep geothermal reservoir of Soultz-sous-Forêts. The model is based on the effective description of Thermo-Hydro-Mechanical (THM) coupling at large scale. Such a model has a fourfold interest: a) the physical integration of laboratory measurements (rock physics), well logging, well head parameters, geological description, and geophysics field measurements; b) the construction of a direct model mechanically based for geophysical inversion: fluid flow, fluid pressure, temperature profile, seismicity monitoring, deformation of the ground surface (INSAR/GPS) related to reservoir modification, gravity or electromagnetic geophysical measurements; c) the sensitivity analysis of the parameters involved in the hydrothermal circulation and identification of the dominant ones; d) the development of a decision tool for drilling planning, stimulation and exploitation. In our model, we introduced extended Thermo-Hydro-Mechanical coupling including not only poro-elastic behavior but also the sensitivity of the fluid density, viscosity, and heat capacity to temperature and pressure. The behavior of solid rock grains is assumed to be thermo-elastic and linear. Hydraulic and thermal phenomena are governed by Darcy and Fourier laws respectively, and most rock properties (like the specific heat at constant stress csσ(T), or the thermal conductivity Λ(T,φ)) are assumed to depend on the temperature T and/or porosity φ. The radioactivity of the rocks is taken into account through a heat source term appearing in the balance equation of enthalpy. To characterize as precisely as possible the convective movement of water and the associated heat flow, water properties (specific mass ρw(T,pw), specific enthalpy hmw(T,pw) dynamic viscosity μw(T), thermal dilation

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-11-01

    The DECOVALEX project is an international cooperativeproject initiated by SKI, the Swedish Nuclear Power Inspectorate, withparticipation of about 10 international organizations. The name DECOVALEXstands for DEvelopment of COupled models and their VALidation againstExperiments. The general goal of this project is to encouragemultidisciplinary interactive and cooperative research on modelingcoupled processes in geologic formations in support of the performanceassessment for underground storage of radioactive waste. Three multi-yearproject stages of DECOVALEX have been completed in the past decade,mainly focusing on coupled thermal-hydrological-mechanicalprocesses.Currently, a fourth three-year project stage of DECOVALEX isunder way, referred to as DECOVALEX-THMC. THMC stands for Thermal,Hydrological, Mechanical, and Chemical processes. The new project stageaims at expanding the traditional geomechanical scope of the previousDECOVALEX project stages by incorporating geochemical processes importantfor repository performance. The U.S. Department of Energy (DOE) leadsTask D of the new DECOVALEX phase, entitled "Long-termPermeability/Porosity Changes in the EDZ and Near Field due to THC andTHM Processes for Volcanic and Crystalline-Bentonite Systems." In itsleadership role for Task D, DOE coordinates and sets the direction forthe cooperative research activities of the international research teamsengaged in Task D.

  2. 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)

    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

  3. 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)

    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

  4. Simulation of coupled THM process in surrounding rock mass of nuclear waste repository in argillaceous formation

    Institute of Scientific and Technical Information of China (English)

    蒋中明; 陈永贵

    2015-01-01

    To investigate and analyze the thermo-hydro-mechanical (THM) coupling phenomena of a surrounding rock mass in an argillaceous formation, a nuclear waste disposal concept in drifts was represented physically in an in-situ test way. A transversely isotropic model was employed to reproduce the whole test process numerically. Parameters of the rock mass were determined by laboratory and in-situ experiments. Based on the numerical simulation results and in-situ test data, the variation processes of pore water pressure, temperature and deformation of surrounding rock were analyzed. Both the measured data and numerical results reveal that the thermal perturbation is the principal driving force which leads to the variation of pore water pressure and deformations in the surrounding rock. The temperature, pore pressure and deformation of rock mass change rapidly at each initial heating stage with a constant heating power. The temperature field near the heater borehole is relatively steady in the subsequent stages of the heating phase. However, the pore pressure and deformation fields decrease gradually with temperature remaining unchanged condition. It also shows that a transversely isotropic model can reproduce the THM coupling effects generating in the near-field of a nuclear waste repository in an argillaceous formation.

  5. Coupled hydro - transport analysis study of geochemical reaction due to unsaturated around the disposal tunnel. Application of the coupled thermo - hydro - mechanical and chemical (THMC) processes model/analysis code in the geological disposal for the high-level radioactive waste

    International Nuclear Information System (INIS)

    The development of excavation disturbed zone (EDZ) around the disposal tunnel affects such as the corrosive environment of the over-pack, re-saturation period of the buffer material, and environmental condition of the nuclear species migration on the geological disposal for the high-level radioactive waste (HLW). It is necessary to consider aftermath of EDZ in initial condition of the realistic numerical simulation of the long-term behavior of near-filed HLW repository after emplacement of engineered barrier system. This report presents the analysis assessment geochemical reaction with the development of the unsaturated zone around the disposal tunnel by developed the coupled Thermo - Hydro - Mechanical and Chemical (THMC) processes model/analysis code. As a result, the THMC processes analysis model apply a change of the solution composition by degasification of the carbon dioxide gas to the pore water and the change of the oxidation-reduction potential due to unsaturated zone around the disposal tunnel. (author)

  6. Behaviour of MX-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 TBT Project -

    International Nuclear Information System (INIS)

    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

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

    International Nuclear Information System (INIS)

    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)

  8. Coupled THM-statistical modeling of induced seismicity during deep geothermal exploitation

    Science.gov (United States)

    Nespoli, Massimo; Rinaldi, Antonio Pio; Wiemer, Stefan

    2015-04-01

    During deep geothermal exploitation, seismicity is unavoidably induced, posing potential hazard for structures and concerns to the local community. Thus, understanding how to avoid triggering of large earthquakes plays a crucial role in the success of underground anthropogenic activities. Recent works, combining physical consideration with stochastic elements, showed the importance of developing tools for hazard and risk assessment that can operate in real-time during reservoir stimulation, and which depend on the ability to efficiently model induced seismicity. Understanding the triggering mechanism is a fundamental step towards controlling the seismicity generated by deep underground exploitation. Although seismicity is generally controlled by fluid injection, it is not possible to rule out some other mechanisms such as static stress transfers between neighbor asperities, or creep-mediated stress interactions along the fault zone. In these conditions, the relationship between fluid pressure and induced seismicity is much more complex. Moreover, while current modeling approaches focus mostly on the active injection phase, the static stress transfer may become import at later stage during the post-injection phase. In order to address these effects, we here propose a novel modeling approach based on coupling a Thermo-Hydro-Mechanical (THM) simulator with a statistical model. The THM simulator provides the fluid flow and the poro-elastic deformation, and the permeability may be enhanced by stress/strain changes. The transient pressure field is then used to trigger events at so-called 'seed points' that are randomly distributed in space and represent potential earthquake hypocenters. Assuming a fault orientation with respect to the stress field and a Mohr-Coulomb failure criterion, we evaluate at each time step, if a seed point is triggered by the pressure/stress change at the seed location. In case of a triggered event, the magnitude of such event is randomly

  9. Drift Scale THM Model

    Energy Technology Data Exchange (ETDEWEB)

    J. Rutqvist

    2004-10-07

    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

  10. 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.

  11. 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

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

    International Nuclear Information System (INIS)

    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

  13. 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)

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

    International Nuclear Information System (INIS)

    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

  15. 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)

    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.)

  16. Field experiment of T-H-M process in the near field

    International Nuclear Information System (INIS)

    A test pit for thermal-hydro-mechanical (T-H-M) experiments was excavated by the shot boring method at the bottom of a drift excavated at Kamaishi in situ field in 1994. The test pit has the diameter of 1.7 m and the depth of 6.0 m. A heating system was installed in the center of the pit and buffer material composed of granulated bentonite was compacted around the heater. Duration of the heating test was 280 days and the heater was controlled to be 100degC at the surface during the time. A number of sensors were installed to monitor the temperature and pore pressure distribution in both buffer and rock mass, the water content distribution in the buffer, swelling pressure of the buffer, and strain in the rock mass. The field experiment led to a better understanding of the behavior of the T-H-M phenomena in the near field. (H. Bata)

  17. Coupled behaviour of bentonite buffer results of PUSKURI project

    International Nuclear Information System (INIS)

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

    International Nuclear Information System (INIS)

    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

  19. Thermo-Hydro-Mechanical Behaviour of expansive clays under high temperatures

    OpenAIRE

    Jacinto, Abel Carlos

    2010-01-01

    Esta Tesis presenta los resultados de la investigación desarrollada en el marco del proyecto Temperature Buffer Test (TBT). El objetivo general de este proyecto es investigar el desempeño de la bentonita usada en barreras de ingeniería bajo la acción de las altas temperaturas que se esperan alrededor de los contenedores con residuos vitrificados. Dentro del proyecto, se ha implementado un ensayo de campo a escala real que simula el almacenamiento de residuos radioactivos de alta actividad. Ad...

  20. Selection of bentonite deposits

    International Nuclear Information System (INIS)

    The selection of bentonite deposits is to offer a supply base of backfill/buffer materials for high-level radioactive waste repository in China. In this paper the comprehensive evaluation criteria were discussed first, then a comprehensive comment on bentonite deposits in China was given. The properties of geographic distribution, origin, reserves and ore quality of bentonite deposits were also discussed. The comprehensive comparison studies on 12 large-sized bentonite deposits was presented. Based on the results obtained Gaomiaozi bentonite deposit, Inner Mongolia, was recommended as the first choice of backfill/buffer materials for repository in China. (author)

  1. Impact of THM reaction rates for astrophysics

    Science.gov (United States)

    Lamia, L.; Spitaleri, C.; Tognelli, E.; Degl'Innocenti, S.; Pizzone, R. G.; Moroni, P. G. Prada; Puglia, S. M. R.; Romano, S.; Sergi, M. L.

    2015-10-01

    Burning reaction S(E)-factor determinations are among the key ingredients for stellar models when one has to deal with energy generation evaluation and the genesis of the elements at stellar conditions. To by pass the still present uncertainties in extrapolating low-energies values, S(E)-factor measurements for charged-particle induced reactions involving light elements have been made available by devote Trojan Horse Method (THM) experiments. The recent results are here discussed together with their impact in astrophysics.

  2. Bentonite porewater chemistry

    International Nuclear Information System (INIS)

    Porewater composition in a compacted bentonite is dependent on the composition of the surrounding groundwater, and on the characteristics of the bentonite itself. Two mechanisms through which bentonite influences the respective porewater composition are distinguished: surface chemical reactions (ion exchange, surface complexation) on smectite and dissolution of minerals and soluble impurities included in bentonite. This report provides the results of different activities related to the definition of porewater chemistry through the use of geochemical models: 1) review of thermodynamic model on ion exchange reaction, 2) modeling of bentonite-water interactions under aerobic conditions, 3) performance of sensitivity analyses of key parameters in the bentonite model, 4) model simulation of bentonite porewater chemistry in the engineered barrier system under repository conditions. Experimental information of bentonite-water interaction allowed the determination of soluble impurities in the bentonite, and the knowledge of these impurities is important for predictive modeling. For the impurities of Kunigel-V1, 0.38% of CaSO4, 0.0011% of NaCl and 0.0044% of KCl were determined. The sensitivity analyses resulted in that the presence of calcite, CaSO4 and pyrite strongly influences the pH in the compacted bentonite, and the pH in compacted bentonite is buffered by the acid/base equilibria at the Na-smectite surface as well. Through the model calculations, some remarks on the expected trends for the long term behavior can be made like that the pH in compacted bentonite is expected to increase with increasing number of water exchange cycles, as long as CaCO3 contributes to the pH buffering capacity, due to slow depletion of the soluble impurities in the bentonite. The pH of the porewater, however, lies in all cases (but in the presence of CaCo3) between 5.6 and 9.5. Based on the findings discussed above, a large number of calculations were carried out to support the definition

  3. 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.)

  4. Geochemical evolution of the Fe/Febex bentonite interface under simultaneous hydration and heating

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. Carbon steel canister and compacted bentonite have been proposed as overpack and sealing materials for the engineered barrier system (EBS). This work reports the results of an experimental work designed to investigate the geochemical processes occurring in the canister/FEBEX bentonite interface during pre-saturation phase of a deep geological disposal. Corrosion behaviour of the canister depends strongly on the evolution of environmental conditions. In this way, moisture conditions at the canister surface will dictate the mechanism and extension of the corrosion process, as well as during the gradual saturation of the near-field, deliquescence of salts and other impurities could favour the initialization of localized corrosion. Therefore, saline fronts are expected to be formed during the saturation of the clay barrier and chloride and sulphate could move by advective transport towards the metallic container due to the hydraulic and thermal gradients that will be established along the bentonite barrier, compromising canister performance. In the tests bentonite was subjected simultaneously to constant hydration and heating, in opposite directions, in order to simulate the conditions of the clay barrier in the repository and better understand the coupled THMC (Thermo-Hydro-Mechanical-Chemical) processes that can affect the performance of the bentonite barrier or the metallic container. The tests were performed in cylindrical cells with an internal diameter of 70 mm and an inner length of 100 mm in which compacted FEBEX bentonite (1.65 g/cm3) and Fe powder were placed. They were made out of Teflon to prevent as much as possible lateral heat conduction. Externally, stainless steel 316 L rings avoid the deformation caused by the swelling of bentonite. The upper closing of the cells was made by means of a stainless steel plug. Inside this plug there was a deposit in which water circulated at room temperature. The bottom

  5. Modelling of THM processes in rocks

    Czech Academy of Sciences Publication Activity Database

    Blaheta, Radim; Kohut, Roman; Neytcheva, M.; Starý, Jiří

    Vol. 2. Ostrava : Ústav geoniky AV ČR, v.v Ostrava, 2007 - (Kožušníková, A.), s. 49-55 ISBN 978-80-86407-18-0. [Geonics 2007. Ostrava (CZ), 23.05.2007-25.05.2007] R&D Projects: GA AV ČR 1ET400300415 Grant ostatní: Uppsala Univ.(SE) UPPMAX project p2004009 Institutional research plan: CEZ:AV0Z30860518 Keywords : mathematical modelling methods * THM processes in rocks * waste disposal Subject RIV: BA - General Mathematics

  6. DECOVALEX-THMC Project. Task A. Influence of near-field coupled THM phenomena on the performance of a spent fuel repository. Report of Task A2

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, T.S. (Canadian Nuclear Safety Commission (Canada)); Jing, L. (Royal lnstitute of Technology, Stockholm (Sweden)) (eds.) (and others)

    2008-06-15

    This report presents the research works performed for the Phase 2 of Task A of the international co-operative research project DECOVALEX-THMC (2003-2007), in which the development and calibration of mathematical models for Lac-du-Bonnet granite and the MX-80 bentonite, using a variety of laboratory and field experiments are the major topics of research. The objective is to assess the implications of coupled THM processes in the near field of a typical repository on its long-term performance, with special concerns on the impact of rock damage and bentonite behaviours on the performance and safety assessments of underground nuclear waste repositories. The mathematical models used by all teams are based on the framework of Biot's theory of poroelasticity. However, the models are extended beyond the classical Biot's theory, in order to include such effects as thermal effects, unsaturated behaviour of the bentonite and damage behaviour of the granite. The results show that the behaviour of both materials are very complex, and an accurate scientific understanding is not currently achieved for repository safety assessment. However, the achievement have clarified a number of scientific and technical issues related to rock damage and bentonite behaviour and helped to establish adequate confidence in identifying the key safety features in the near field of a hypothetical repository, using coupled THM scoping calculations. These key features would be the temperature evolution, the resaturation and stresses in the bentonite, the extent of the inner damage zone in the rock, and the change in hydraulic and mechanical properties in the rock

  7. Copper/bentonite interaction

    International Nuclear Information System (INIS)

    The prediction of the processes and rate of corrosion of the KBS 2 copper canisters must be based on a proper scenario, which involves the physical state of the bentonite surrounding the canisters, and the chemical interaction between copper and bentonite. Literature data suggest slow Cu migration and Cu exchanging originally adsorbed cations. Two tests involving copper/bentonite contacts for 3 - 6 months in boreholes have yielded certain valuable information. Thus, Cu ion migration is indeed very slow and where it yields a sufficiently high concentration, it is associated with replacement of originally adsorbed Na ions, which should result in an increased permeability. In one of the tests the copper was separated from the bentonite by a partly air-filled slot. These conditions caused the formation of copper oxides and hydroxides which intermingled with the bentonite that expanded to fill the slot. Due to the low solubility of these copper compounds, the Cu ion concentration was too low to produce ion exchange during the time of observation. (Author)

  8. Porewater chemistry in compacted bentonite

    International Nuclear Information System (INIS)

    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

  9. 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.

  10. Factors affecting the thermo-hydro-mechanical response of clay in the safety assessment of nuclear waste repositories

    International Nuclear Information System (INIS)

    Decay heat due to waste disposal in a saturated clay medium causes the development of pore water overpressures. In this study, the effects of thermal pore pressure increase such as effective stress reduction, hydraulic gradient increase and possible yielding have been taken into account. Numerical computations assess the disturbance on the in situ stress field due to excavation of an isolated borehole under different assumptions on the drilling conditions. Thermo-mechanical response of clay over a zone about 1 metre wide around the borehole depends significantly on the excavation technique. This zone is characterized by development of plastic strains; under some drilling conditions yielding occurs with dilative strains, which are associated to fracturing of the clay. Outside this zone, thermo-mechanical response has been found as dependent mostly on the perturbation of the thermal field. Significant pore pressure increase and effective stress decrease develop over a zone 10 metre wide. This study has been developed for a specific type of clay and it aims to point out that analogous studies have to be undertaken for sites to be considered for waste emplacement

  11. 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

  12. UO22+ sorption on bentonite

    International Nuclear Information System (INIS)

    The capacity of bentonite and purified bentonite to remove UO22+ ions from aqueous solutions has been investigated. The UO22+ uptake in these clays was determined for 0.2 and 0.002M uranyl nitrate solutions. It was found that under these conditions (0.2M) the maximum UO22+ uptake was 1.010±0.070 meq UO22+/g of bentonite and 0.787±0.020 meq UO22+/g of purified bentonite. In purified bentonite UO22+ sorption is irreversible up to 50 hours as no desorption was observed. Such is not the case in the natural bentonite. X-ray diffraction, thermal analyses, and transmission electron microscopy were used to characterize the solids. The uranium content was determined by neutron activation analysis. (author)

  13. Bentonite erosion. Final report

    International Nuclear Information System (INIS)

    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.

  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. 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)

    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

  16. Bentonite erosion. Laboratory studies

    International Nuclear Information System (INIS)

    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 mostly

  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. The Decovalex III Project: A Summary of Activities and LessonsLearned

    Energy Technology Data Exchange (ETDEWEB)

    Tsang, Chin-Fu; Jing, Lanru; Stephansson, Ove; Kautsky, Fritz

    2005-03-21

    Initiated in 1992, the DECOVALEX project is an international collaboration for advancing the understanding and modeling of coupled thermo-hydro-mechanical (THM) processes in geologic systems. The project has made important scientific achievements through three stages and is progressing in its fourth stage. It has played a key role in the development of mathematical modeling and in situ testing of coupled THM processes in fractured rock and buffer/backfill materials, a subject of importance for performance assessment of radioactive waste geologic repositories. This paper summarizes studies under the most recent stage of the project, DECOVALEX III (2000-2003). These studies include those of two major field experiments: (a) the FEBEX experiment at Grimsel, Switzerland, investigating coupled THM processes in a crystalline rock-bentonite system, and (b) the Drift Scale Test (DST) experiment at Yucca Mountain, Nevada, investigating coupled THM processes in unsaturated tuff. These are two of the largest multiyear heater tests undertaken to date for the study of coupled THM processes in geological systems. In addition, three so-called benchmark tests are also studied to evaluate the impact of coupled THM processes under different scenarios and geometries. Within the DECOVALEX project, multiple research teams participated in each of the studies, using different approaches and computer codes. Comparisons of results have provided insight into coupled THM processes, which in turn has stimulated further development of our modeling capabilities. Lessons learned from these studies are discussed. The scientific advances and enhanced insight gained through this kind of international cooperation illustrate the effectiveness of the DECOVALEX project.

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

    International Nuclear Information System (INIS)

    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

  20. 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

  1. 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

  2. Towards the generic conceptual and numerical framework for the simulation of CO 2 sequestration in different types of georeservoirs

    DEFF Research Database (Denmark)

    Görke, Uwe Jens; Taron, Joshua; Singh, Ashok;

    2011-01-01

    In this paper, conceptual and numerical modeling of coupled thermo-hydro-mechanical (THM) processes during CO 2 injection and storage is presented. The commonly used averaging procedure combining the Theory of Mixtures and the Concept of Volume Fractions serves as background for the complex porou...

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

    International Nuclear Information System (INIS)

    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- data is excellent except for the data near the heater. The largest deviations of the model from inferred aqueous

  4. 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

  5. Bentonite in the repository - Manufacture of bentonite blocks. A literature study; Bentonit i slutfoervaret - Tillverkning av bentonitblock. En litteraturstudie

    Energy Technology Data Exchange (ETDEWEB)

    Hultgren, Aa. [NFC Konsult, Nykoeping (Sweden)

    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.

  6. Spectral response of THM grown CdZnTe crystals

    DEFF Research Database (Denmark)

    Chen, H.; Awadalla, S.A.; Harris, F.; Lu, Pinghe; Redden, R.; Bindley, G.; Copete, A.; Hong, J.; Grindlay, J.; Amman, M.; Lee, J.S.; Luke, P.; Kuvvetli, Irfan; Budtz-Jørgensen, Carl

    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...

  7. Equilibria in saturated bentonite

    International Nuclear Information System (INIS)

    It has been proposed that smectite clays, the predominant minerals in bentonite, are metastable solid solutions whose compositional heterogeneity prevents strict adherence to fixed ion activities and activity ratios characterizing invariant equilibria among stoichiometric phases. This is analysis of exceptionally well-constrained experimental data using a solid solution model defined by the phase rule and estimated ideal site-mixing are approached among smectite solid solutions and coexist metastably with respect to aSiO2(aq). Irreducible uncertainties are generated in the model by analytical and conceptual deficiencies in understanding compositional variability in smectite. However, their estimated effects on smectite's stability are relatively small, and are comparable to the effects of experimental uncertainty in standard Gibbs energies on the stabilities of stoichiometric minerals. An alternate analysis of the data further confirms that smectite does not behave like a stoichiometric phase. Ion-exchange models for this clay mineral may therefore be thermodynamically ill defined because stoichiometric behavior is assumed implicitly under limiting conditions of fixed sites. Ion exchange is a pragmatic simplification enabling empirical analysis of some experimental data. However, its empirical, rather than thermodynamic, basis should not be overextended to conditions that are beyond an experimentally calibrated range

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

    International Nuclear Information System (INIS)

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    P. Dixon

    2004-02-09

    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

  10. CONCENTRATION OF TRIHALOMETHANES (THM AND PRECURSORS IN DRINKING WATER WITHIN DISTRIBUTION NETWORKS

    Directory of Open Access Journals (Sweden)

    CORNELIA DIANA ROMAN

    2012-03-01

    Full Text Available Concentration of trihalomethanes (THM and precursors in drinking water within distribution networks. Water chlorination is the disinfection method most widely used, having however the disadvantage of producing trihalomethanes (THM as secondary compounds, which are included in the list of priority hazardous substances in water. THM formation is influenced by the raw water composition and chlorine from the disinfection process. This paper intends to highlight the individual values of the chemical compounds precursors of THM in the water network in order to correlate them with the evolution of THM concentration. The cities of Targu Mures and Zalau were chosen as the study area having surface waters with different degrees of contamination as the water source. Pre-treatment with potassium permanganate is used at the water treatment plant in Targu Mures, while pre-chlorination is used at the water treatment plant in Zalau. Water sampling was performed weekly between March-May, 2011 in three sampling points of each city, maintained during the period of study. Total THM and their compounds as well as THM precursors (oxidability, ammonium content, nitrites and nitrates were measured. The water supplied in the distribution network corresponded integrally to the quality standards in terms of the analyzed indicators, including THM concentrations. The higher average THM concentrations in Zalau (52.01±14 μg/L compared to Targu Mures (36.43±9.14 μg/L were expected as a result of precursors concentration. In terms of THM compounds, they had similar proportions in the two localities, chloroform being clearly predominant, followed by dichlorobromoform and dibromochloroform, while bromoform was not identified. Statistical data analysis showed that the presence of THM precursors is correlated with the THM levels but not sufficient for their generation, even if they can be considered in general the basis of a valid prediction.

  11. Geomechanical characterisation of unsaturated Kunigel V1 bentonite: swelling and shear strength

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. The development and validation of hydro-geomechanical models for bentonite buffer are one of the important subjects to appropriately evaluate long term behaviour of EBS in radioactive waste disposal. The Barcelona Basic Model (BBM), which is one extension of the modified Cam- Clay model for unsaturated and expansive soil, has been developed and widely applied to several hydro-geomechanical problems by using the coupled THM code, Code-Bright. Some advantages of the model are that hydro-geomechanical characteristics of buffer materials under saturated and partially saturated conditions are taken into account as well as the swelling characteristics due to wetting. Applicability of the BBM to consolidation and swelling behaviour of unsaturated bentonite has already been confirmed. In this study swelling characteristics of unsaturated bentonite are further discussed based on results from controlled-suction odometer tests, and in addition shear strength depending on matric suction is discussed based on controlled-suction triaxial compression tests. Swelling tests of compacted bentonite (Kunigel V1, initial dry density: 1.0 Mg/m3) under constant confined vertical net stresses (20 and 100 kPa) were performed by using controlled-suction odometer cells. Matrice suction was stepwise reduced from 500 kPa to 0 kPa by 100 kPa. It is found that swelling is more dominant in latter step of the suction change (i.e., closer steps to saturation), especially the step from 100 kPa to 0 kPa. Swelling due to wetting, i.e. decrease in matric suction is defined in the BBM. Controlled-suction triaxial compression tests of compacted bentonite (Kunigel V1, initial dry density: 1.36 Mg/m3) under both constant matric suctions (0, 300, and 500 kPa) and constant confined lateral net stresses were performed to study dependency of shear strength on matric suction. It is found that the apparent cohesion linearly increases with increase in matric

  12. Multiple scenarios of bentonite alteration

    International Nuclear Information System (INIS)

    Performance assessment for TRU waste repositories has shown that soluble and poorly sorbing nuclides such as I-129 and C-14 dominate the dose. These nuclides are expected to migrate with groundwater flow, hence hydraulic conditions and their evolution with time in the repository are key issues for repository safety. Cementitious material will be used for waste packaging, backfilling and structural material in a TRU waste repository. Bentonite is also expected to be used for some TRU wastes to provide the function of a hydraulic barrier in the disposal system. There is concern that the coexistence of cementitious material and bentonite cause the alteration of smectite due to interaction with hyperalkaline leachates and consequent deleterious perturbation of the function of bentonite as a hydraulic barrier. Many research studies have been performed to identify possible mechanisms of cement-bentonite interaction. However, uncertainties still exist in our understanding of the precise chemical scheme of bentonite alteration in highly alkaline conditions, especially the space and time variation of secondary mineral occurrences. In order to reflect this uncertainty, multiple scenarios of bentonite alteration were developed based on the possible mineralogical changes derived from knowledge of both experiments and observation of natural systems. It was focused that the mineral reaction involving hyperalkaline fluids would thermodynamically depend on the variable chemical condition in bentonite buffer and that kinetics would be important as well as thermodynamic stability in controlling their occurrence, i.e., the kinetic controls may operate to remain metastable minerals over the long term. The mineralogical consequences of the interaction between clays and alkaline fluids are summarized as follows. Clay → C-S-H gel and other solids which can rapidly precipitate. Clay and gel → illite. Clay and gel → metastable zeolite. Clay and gel → metastable zeolite → stable

  13. 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.

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

    International Nuclear Information System (INIS)

    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

  15. 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.

  16. Control of Bromate and THM Precursors Using Ozonation Combined System

    Institute of Scientific and Technical Information of China (English)

    SHU-GUANG XIE; DONG-WEN SHI; DONG-HUI WEN; RUI WANG; DAN-LI XI

    2007-01-01

    Objective To investigate the feasibility of reducing THM precursors and controlling bromate taste and odor in drinking water taken from the Yellow River by an ozonation combined system. Methods The appropriate ozone dosage was determined,and then the changes of TOC,UV254 and THM formation potential(THMFP)in the combined system were evaluated. Results One mg/L ozone could effectively remove taste and odor and meet the maximum allowable bromate level in drinking water.The pre-ozonation increased THMFP,but the conventional treatment system could effectively reduce the odor.The bio-ceramic filter could partly reduce CHCI3FP,but sometimes might increase CHCI2BrFP and CHCIBr2FP.The biological activated carbon(BAC)filter could effectively reduce CHCI3FP and CHCI2BrFP,but increase CHCIBr2FP.Compared with other filters.the fresh activated carbon(FAC)filter performed better in reducing THMFP and even reduced CHCIBrzFP.Conclusion The combined system can effectively reduce taste,odor,CHCI3FP,and CHCI2BrFP and also bring bromate under control.

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

    International Nuclear Information System (INIS)

    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

  18. Modelling the thermo-mechanical volume change behaviour of compacted expansive clays

    CERN Document Server

    Tang, Anh-Minh; 10.1680/geot.2009.59.3.185

    2009-01-01

    Compacted expansive clays are often considered as a possible buffer material in high-level deep radioactive waste disposals. After the installation of waste canisters, the engineered clay barriers are subjected to thermo-hydro-mechanical actions in the form of water infiltration from the geological barrier, heat dissipation from the radioactive waste canisters, and stresses generated by clay swelling under almost confined conditions. The aim of the present work is to develop a constitutive model that is able to describe the behaviour of compacted expansive clays under these coupled thermo-hydro-mechanical actions. The proposed model is based on two existing models: one for the hydro-mechanical behaviour of compacted expansive clays and another for the thermo-mechanical behaviour of saturated clays. The elaborated model has been validated using the thermo-hydro-mechanical test results on the compacted MX80 bentonite. Comparison between the model prediction and the experimental data show that this model is able...

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

    International Nuclear Information System (INIS)

    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

  20. Preparation of bentonites for laboratory investigations

    International Nuclear Information System (INIS)

    A project study on behalf of Nagra for high radioactive waste disposal in deep geological formations as well as literature studies have shown that bentonite could be a suitable filling and sealing material. The Institute for Foundation and Soil Mechanics of the Swiss Institute of Technology has been given a contract by Nagra to investigate different bentonites. The investigations concentrate on the Na-bentonite MX-80 from Wyoming, which is foreseen by the Swedes, and on the geographically more favorable Ca-bentonite Montigel from Bavaria. Montigel powder and granulate, which show certain manufacturing advantages, were investigated. The quality of the bentonites was examined especially to ascertain whether the bentonites were homogeneous with respect to composition and properties. Montmorillonite, carbonate, oxidizing substances and exchangeable ions were quality content criteria for bentonite. The investigations showed that these bentonites are typical Na- and Ca-bentonites. A representative sample of 500 kg weight (250 kg for Montigel K) was largely homogeneous. The samples were analysed by x-rays and thermoanalysis. Additionally grain size, carbonate content, methylene blue value, yield point, exchange capacity and exchangeable ions were determined. 5 refs., 2 figs., 2 tabs

  1. Pertechnetate diffusion in GMZ bentonite

    International Nuclear Information System (INIS)

    99Tc is an important radionuclides related to repository safety assessment. The mobility pertechnetate (TcO4-) can be reduced to immobility technetium(IV) hydrous oxides (TcO2 · nH2O) by Fe(II)-bearing minerals. In China, Gaomiaozi (GMZ) bentonite is regarded as the favorable candidate backfilling material for the HLW repository, which is contained some FeO. The diffusion behavior of 99Tc was investigated in GMZ bentonite by through- and out-diffusion methods. The effective diffusion coefficient (De), the accessible porosity (εacc), apparent diffusion coefficient (Da) and distribution coefficient (Kd) were decreased with the increasing of dry density. The De values were (2.8 ± 0.2) x 10-11 m2/s and (3.5 ± 0.2) x 10-12 m2/s at dry density of 1,600 and 1,800 kg/m3, respectively. It was indicated that the dominating species was TcO4- during the diffusion processing. While, out-diffusion results showed that part of TcO4- may be reduced by Fe(II). The relationship of De and εacc could be described by Archie's law with exponent n = 2.4 for 99Tc diffusion in GMZ bentonite. Furthermore, the relationship between Da and dry density (ρ) was exponential. (author)

  2. 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

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

    International Nuclear Information System (INIS)

    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, CodeBright 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 CodeBright, 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. Bentonite erosion by dilute waters in initially saturated bentonite

    International Nuclear Information System (INIS)

    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

  5. The bentonite industry in North America

    International Nuclear Information System (INIS)

    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 105 Mg of used fuel would be emplaced. This would require 2.5 x 106 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 108 Mg, and vast supplies are known to exist but not yet proven. The Canadian conceptual disposal vault would require 6 x 104 Mg of sodium bentonite each year for 40 years. The bentonite industry of North America has an installed annual production capacity of 2 x 107 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.)

  6. Design and emplacement of bentonite barriers

    International Nuclear Information System (INIS)

    Bentonite is a well known sealing and buffer material for waste disposals in hard rock conditions. Bentonite was also tested as a sealing material for rock salt formations. Under salt conditions the hydraulic conductivity is higher and the swelling pressure is lower then under freshwater conditions using the same bentonite dry density. Because rock salt conditions are more ambitious for bentonite, the new research results of material design and emplacement technology are very useful for applications under freshwater conditions. Commercial available bentonites were tested by measurements of hydraulic conductivity and swelling pressure at various dry densities. The result is the required emplacement dry density for each bentonite. Following an industrial production process for high compacted bentonite materials with low initial water content was developed. Bentonite blocks for drift sealings and compacts / granules for bulk mixtures for shaft sealings have been successful tested in large scale in situ tests in salt mines. Since 1998 about 500 t of bentonite blocks have been produced by the company Preiss-Daimler Industries GmbH - Feuerfestwerke Wetro. The blocks have a standard size of (250 x 125 x 62,5) mm. A proper fit of the blocks to the rock contour can be formed by sawing. The emplacement as dry brickwork is simple and reliable for the rough conditions in underground mines. The recent shaft sealing systems consist of a binary mixture of air dry compacted bentonite compacts and granules (moisture content 7 - 10 %). This material design and the production technology were developed in cooperation with the K and S Group. Both components of the bulk mixture (compacts and granules) are now produced at the plant 'Bergmannssegen-Hugo' (K and S Group). This material defines the actual best state of the art for bentonite sealing materials for long term stable shaft sealing systems, especially under difficult conditions like in salt mines. Since 2004 about 3000 t of

  7. Properties of Bentonite Enhanced Loess and Laterite

    Institute of Scientific and Technical Information of China (English)

    刘阳生; 白庆中; 聂永丰

    2004-01-01

    Loess and laterite distributed widely in the northern and southern China cannot be directly used as the natural barrier to isolate the solid waste because of their high hydraulic conductivity. In this paper, they are enhanced by bentonite to improve their hydraulic performance. The impact of bentonite content and water content on compressive strength of the compacted soil was investigated. The effects of bentonite content, water content, dry density and hydraulic gradient on the hydraulic conductivity were studied in detail. For the laterite and the laterite with 8% of bentonite, the experimental results of hydraulic conductivity can be applied in the engineering design. However, for the loess and the bentonite enhanced loess, those of hydraulic conductivity can not be directly applied in the engineering design because their hydraulic performance does not comply with the Darcy's law. These experimental results have to be carefully modified before application.

  8. 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)

    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)

  9. A thermo-hydro-mechanical model for fracture propagation and evolution, fluid flow, and transport in the disturbed rock zone of an argillaceous repository

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. A key reason for considering argillaceous rock for nuclear waste disposal is the extremely low permeability and limited fracturing generally found in this rock type. Underground research laboratories in Switzerland, Belgium, and France have been developed to investigate the potential of argillaceous rock for nuclear waste disposal. However, excavations in argillaceous rock have shown the general tendency for fracturing to occur in the immediate vicinity of the excavations, called the disturbed rock zone (DRZ). Fractures are generated as a result of changes in mechanical stress caused by the excavation and changes in saturation caused by ventilation. The attributes of fractures in the DRZ evolve in response to post-closure changes in temperature, water redistribution, and materials interactions associated with a nuclear waste repository, and there is a tendency for the DRZ fractures to close over time, called self-sealing. Here we present a new computational method applicable to three-dimensional discrete fracture networks in the DRZ of an argillaceous rock. The method is intended to predict, in a mechanistic manner, the fracture formation and evolution as well as flow and transport through the fractured porous rock in the DRZ accounting for dynamically changing thermal-hydrologic-mechanical conditions. The new computation method simulates the non-isothermal multi-phase flow and transport processes with TOUGH2, a widely used subsurface simulator developed at Lawrence Berkeley National Laboratory. We use EOS7R, one of the TOUGH2 modules for thermal-hydrologic flow processes involving brine, water, and air phases as well as transport processes involving two-component radionuclide chains (Oldenburg and Pruess, 1995). A mechanical lattice model based on the rigid body-spring concept of Kawai (1977) is coupled to the TOUGH2 model to compute elastic response and fracture propagation. These two models share the same unstructured, three-dimensional Voronoi grid and the same set of nodes, where the scalar field quantities (e.g. temperature, pressure, and saturation) and the generalized displacement are obtained by TOUGH2 and the lattice model, respectively. As shown in Figure 1, each node pair ij that is mechanically connected is composed of a zero-size spring set located at the centroid of the corresponding Voronoi facet. Fractures propagate along Voronoi cell boundaries as thermal-hydrologic-mechanical induced stresses evolve and exceed the materials strength. Local fracture permeability and porosity are assigned based on grid geometry and apertures computed by the lattice model from mechanical strain induced at fracture locations. To demonstrate the utility of the coupled approach, fracture development in a clay sample subjected to drying environment is simulated. Figure 2 shows numerical results of crack pattern demonstrated by the 3-D coupled lattice model under drying shrinkage condition with restrained boundaries except one surface. Two stages of crack opening can be observed: 1) vertical cracks due to shrinkage strain increases, and 2) lateral cracks caused by curling of slab structure. The present modeling results include complicating factors such as time-dependent crack development, and the coupling of internal flow and mass transport with crack opening. Future developments will include coupling the lattice model with TOUGHREACT (Xu et al., 2004) to incorporate chemical processes, in particular, chemical-mechanical effects (e.g., swelling caused by changes in brine composition) that are characteristic of argillaceous rock types. (authors)

  10. On the Thermo-Hydro-Mechanical Behaviour of a Sheared Callovo-Oxfordian Claystone Sample with Respect to the EDZ Behaviour

    Science.gov (United States)

    Menaceur, Hamza; Delage, Pierre; Tang, Anh Minh; Conil, Nathalie

    2016-05-01

    To better understand the impact of temperature elevation on the response of the excavation damaged zone around repository cells and galleries for radioactive waste disposal, the combined effects of shear and temperature elevation were investigated in the laboratory on the Callovo-Oxfordian claystone. To do so, a hollow cylinder thermal triaxial cell with short drainage path specifically developed for low permeability rocks was used. Once properly saturated under stress conditions close to in situ, the specimen was sheared along a constant effective mean stress path mimicking the stress path followed during gallery excavation. The shear stress was afterwards released and an undrained heating test was performed on the sheared specimen. It was observed that the temperature increase under undrained conditions led to a thermal increase in pore water pressure resulting in a decrease in mean effective stress that brought back the sheared specimen to failure, evidencing a thermally induced failure. Steady state radial permeability tests performed at various stages of the test demonstrated that the overall permeability of the sheared specimen was comparable to that before shearing, confirming the excellent self-sealing properties of the Callovo-Oxfordian claystone. This shows that, in spite of being possibly remobilised by temperature elevation, the EDZ will keep an overall permeability constant equal to that of the massive rock, keeping the same isolation properties.

  11. 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)

    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 (H2) overpressure resistance of engineered barriers made of compacted clays were summarized. (author)

  12. THM reduction on water distribution network with chlorine dioxide as disinfectant; Reduccion de THM en red de distribucion utilizando dioxido de cloro como desinfectante

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-07-01

    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 100{mu}g/l, along the 200 km of the supply network. (Author) 13 refs.

  13. Bentonite mat demonstration. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Serrato, M.G.

    1994-12-30

    The Bentonite Mat Demonstration was developed to provide the Environmental Restoration Department with field performance characteristics and engineering data for an alternative closure cover system configuration. The demonstration was initiated in response to regulatory concerns regarding the use of an alternative cover system for future design configurations. These design considerations are in lieu of the US Environmental Protection Agency (EPA) Recommended Design for Closure Cover Systems and specifically a single compacted kaolin clay layer with a hydraulic conductivity of 1 {times} 10{sup {minus}7} cm/sec. This alternative configuration is a composite geosynthetic material hydraulic barrier consisting from bottom to top: 2 ft compacted sandy clay layer (typical local Savannah River Site soil type) that is covered by a bentonite mat--geosynthetic clay liner (GCL) and is overlaid by a 40 mil High Density Polyethylene (HDPE) geomembrane--flexible membrane liner. This effort was undertaken to obtain and document the necessary field performance/engineering data for future designs and meet regulatory technical requirements for an alternative cover system configuration. The composite geosynthetic materials hydraulic barrier is the recommended alternative cover system configuration for containment of hazardous and low level radiological waste layers that have a high potential of subsidence to be used at the Savannah River Site (SRS). This alternative configuration mitigates subsidence effects in providing a flexible, lightweight cover system to maintain the integrity of the closure. The composite geosynthetic materials hydraulic barrier is recommended for the Sanitary Landfill and Low Level Radiological Waste Disposal Facility (LLRWDF) Closures.

  14. 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.

  15. Effectiveness of fracture sealing with bentonite grouting

    International Nuclear Information System (INIS)

    Bentonite is known to have an extremely low permeability and a self-healing ability. It has therefore been selected as a major sealing component in several repository concepts. Bentonite grouts have the following advantages, (1) small particle size, can be injected into small fractures or voids, (2) suitable water absorption properties, can produce gels at low concentrations, and (3) stable physical and chemical properties, may have considerable longevity. Bentonite fracture grouting tests are performed on a model made of circular acrylic plates with outer diameter of 30 cm and central injection hole of 2.5 cm diameter. Suspension with bentonite concentration of 15% to 31% have been injected into fractures with apertures of 9 to 90 microns under injection pressures less than 0.6 MPa. Grouting reduces the hydraulic conductivities of the fractures from the 10-1 to the 10-5 cm/s level. When the suspension is thin enough and the fracture is very small, channeling develops in the grouted fractures. Preliminary results indicate that the permeability of a grouted fracture does not increase with time in more than 125 days. The flow properties of bentonite suspensions, viscosity, shear stress, yield stress and gelation, are investigated. Water flow through ungrouted fractures and movement of water in bentonite grout are studies. The physical stability or bleeding capacity of bentonite suspensions is determined. 122 refs., 56 figs., 10 tabs

  16. Quality assurance of the bentonite material

    International Nuclear Information System (INIS)

    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.)

  17. Activation of wine bentonite with gamma rays

    International Nuclear Information System (INIS)

    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/dm3. 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

  18. 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)

    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

  19. 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

  20. Development of a conceptual model for vapour diffusion dominated bentonite re-saturation

    International Nuclear Information System (INIS)

    The established codes for modelling the re-saturation of compacted bentonite are based on the assumption that the hydraulic processes can be described as a two-phase flow of liquid water and air. But not all hydraulic phenomena going on at micro scale during re-saturation are properly represented by the macroscopic description as a two-phase flow. Key to an examination of consistency between micro- and macroscopic description is the microstructure of the clay grains and the processes going on during re-saturation. Water propagates not only in the space of the macro-pores between the clay grains. A major amount of water migrates from the macro-pores into the micro-pores of the grains, from where the water is drawn into the inter-lamellar space of the clay particles. This holds true not only for liquid water but also for water vapour as has been shown by uptake experiments with vapour. The particles act as sinks for pore water flow, they immobilise it in the inter-lamellar space for all practical purposes and swell at the same time, thereby reducing the available pore space. In the end these considerations reveal some inconsistencies between the hydraulic processes going on on a microscopic scale and the macroscopic conceptual THM-model. Investigations have been performed at GRS for some time now suggesting that compacted bentonite in contact with liquid water does not re-saturate via the liquid water phase but mainly by evaporation in the pore space and subsequent vapour diffusion. The related conceptual model is based on the idea that a narrow and completely water-saturated zone develops very fast at locations where bentonite comes into contact with liquid water as has been suggested by. In this zone, the permeability is reduced to such an extent that the amount of liquid water that enters the bentonite balances the amount of water evaporating at the water-air interface inside the bentonite. That interface does therefore not proceed into the bentonite but instead

  1. Modelling Iron-Bentonite Interactions

    Science.gov (United States)

    Watson, C.; Savage, D.; Benbow, S.; Wilson, J.

    2009-04-01

    The presence of both iron canisters and bentonitic clay in some engineered barrier system (EBS) designs for the geological disposal of high-level radioactive wastes creates the potential for chemical interactions which may impact upon the long-term performance of the clay as a barrier to radionuclide migration. Flooding of potential radionuclide sorption sites on the clay by ferrous ions and conversion of clay to non-swelling sheet silicates (e.g. berthierine) are two possible outcomes deleterious to long-term performance. Laboratory experimental studies of the corrosion of iron in clay show that corrosion product layers are generally thin ( 250 °C) are dominated by chlorite, whereas lower temperatures produce berthierine, odinite, cronstedtite, or Fe-rich smectite. Unfortunately, the inevitable short-term nature of laboratory experimental studies introduces issues of metastability and kinetics. The sequential formation in time of minerals in natural systems often produces the formation of phases not predicted by equilibrium thermodynamics. Evidence from analogous natural systems suggests that the sequence of alteration of clay by Fe-rich fluids will proceed via an Ostwald step sequence. The computer code, QPAC, has been modified to incorporate processes of nucleation, growth, precursor cannibalisation, and Ostwald ripening to address the issues of the slow growth of bentonite alteration products. This, together with inclusion of processes of iron corrosion and diffusion, has enabled investigation of a representative model of the alteration of bentonite in a typical EBS environment. Simulations with fixed mineral surface areas show that berthierine dominates the solid product assemblage, with siderite replacing it at simulation times greater than 10 000 years. Simulations with time-dependent mineral surface areas show a sequence of solid alteration products, described by: magnetite -> cronstedtite -> berthierine -> chlorite. Using plausible estimates of mineral

  2. Gas migration through bentonite clay

    International Nuclear Information System (INIS)

    Hydrogen gas produced by irradiation of pore water in the highly compacted bentonite that surrounds the copper canisters according to the KBS 2 and 3 concepts, may escape from the clay/copper interface if the gas pressure is higher than the groundwater pressure. A reasonable physical model predicts that gas may penetrate wider capillary passages that actually exist in the very dense clay, although these passages are still of microscopic size. In the large majority of the clay voids, the capillary action is sufficient, however, to resist gas penetration, and this suggests that a possible mechanism of gas migration is that of a finger-like pattern of tortuous gas passages extending from the canisters if radiolysis takes place at all. Two series of experiments have been run at gas pressures up to about 10 MPa. Nitrogen as well as hydrogen were used in these tests which seem to confirm, in principle, the validity of the physical model. (authors)

  3. Results of bentonite grouting experiment

    International Nuclear Information System (INIS)

    The Bentonite grouting, which will not solidify, is mainly expected to reduce the hydraulic conductivity of underground water in the expected damage zone by filling the fractures or cracks, so the evaluation of the degree of hydraulic conductivity, stability and the improvement area becomes important. The study and basic experiments for sealing of the adits have been promoted, up to now, from the aspects of the characteristics and long term stability of candidate materials, and design and construction (Pusch et al., 1987; Tanai and Masuda, 1991). However, in Japan, the application examples of clay type materials for grouting are extremely few and is limited to the construction experience of the national oil underground storage at Kuji (Miyanaga and Ebara, 1993), with the exception of some test cases (Boergesson et al., 1991) from overseas. This report summarize basic characteristics of the clay type material relevant to the hydraulic conductivity, from the result of the clay grouting experiment conducted at the rock site. (author)

  4. Effect of bentonites on fluorometric selenium determination

    International Nuclear Information System (INIS)

    Bentonites in feeds cause error in the analysis for Se by the AOAC (3.097-3.101) fluorometric method for Se in plants. The error apparently results from the binding of the piazselenol by insoluble residue from the bentonite. This effect is avoided by diluting digests to volume after reduction with HCl, centrifuging or allowing to stand, and analyzing a portion of the clear supernatant liquid. Insoluble residues present after digestion of plant materials do not appear to cause a similar error

  5. Thermal cycling: impact on bentonite permeability

    OpenAIRE

    Zihms, S.G.; Harrington, J. F.

    2015-01-01

    Due to its favourable properties, in particular, low permeability and swelling capacity, bentonite has been favoured as an engineered-barrier and backfill material for the geological storage of radioactive waste. To ensure its 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 investigates the hydraulic response of bentonite under multi-step thermal loading subject to a constant-volu...

  6. Diffusion of humic colloids in compacted bentonite

    International Nuclear Information System (INIS)

    In Sweden, as in many other countries, compacted bentonite will surround the encapsulated spent nuclear fuel in a deep bedrock repository. Bentonite gives mechanical support and minimizes the water flow over the deposition holes. The retardation for cationic radionuclides escaping a faulted canister is high in saturated compacted bentonite, since cationic radionuclides sorbs strongly on the bentonite surface, and the only plausible transport mechanism is diffusion. Sorption and diffusion of radionuclides in the bentonite barrier has been extensively studied, and sorption and diffusion coefficients are well established. There is a lack of knowledge as well as data for effects of colloids on radionuclide mobility and transport in the bentonite barrier. In a deep bedrock repository, colloids, particles in the size range of 1-1000 nm, will be present, however in very low concentrations. The colloids origin from eroded bedrock and filling material, mineral oxides, clay, degraded organic compounds and micro-organisms etc. The bentonite barrier is regarded to be an efficient filtering barrier for colloids. With the widely spread micro-structure with pores in between the montmorillonite flakes in the size range of nm, and the inter particle voids partly gel filled of sizes, colloid transport seems unlikely. In a Japanese diffusion study on gold colloids no breakthrough of the colloids was detected. However, to reject the possibility of enhancement of transport of radionuclides by colloids, more data from diffusion studies on other types of colloids in compacted bentonite are needed. Therefore diffusion experiments of Humic Colloids (HC), in the size range of 1-10 nm, were performed. (author)

  7. Removal of oil from water by bentonite

    International Nuclear Information System (INIS)

    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

  8. Exchangeability of bentonite buffer and backfill materials

    International Nuclear Information System (INIS)

    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

  9. Pore water chemistry of the febex bentonite

    International Nuclear Information System (INIS)

    The knowledge of pore water chemistry in the clay barrier is essential for performance assessment purposes in a nuclear waste repository, since the pore water composition controls the processes involved in the release and transport of the radionuclides. The methodology followed to define the representative composition of the FEBEX bentonite pore water is presented in this paper. A series of bentonite-water interaction tests have been performed with the aim of providing a database on the main chemical parameters of the bentonite. These tests were carried out both with high solid to liquid (s:l) ratios (squeezing tests) and low s:l ratios (aqueous extracts tests). The exchangeable cations have also been analyzed to determine the selectivity coefficient of the exchange reactions. To complete the data set, a physical and mineralogical characterization of the bentonite was made. The most significant bentonite-water interaction processes controlling the chemistry of the system was identified. The ion concentrations basically depend on the s:l ratio of the system, and the pore water composition is controlled by the dissolution of chlorides, dissolution/precipitation of carbonates and sulphates and the cation exchange reactions in the smectite. The bentonite/water system was modelled with the PHREEQC2 program to obtain the best possible estimation of the pore water composition for initial conditions of water content (=14%), after checking the conceptual model with the experimental results. The model predictions fitted satisfactorily with the experimental data at low s:l ratios. At high s:l ratios, the modelled results agree adequately, except for the sulphate content, which could be affected by the effective porosity, anion exclusion or stagnant zones not taken into account in the model. According to the model, the FEBEX bentonite pore water at 14% moisture is a sodium-chloride type, with an ionic strength of 0.25 M and pH of 7.78. Copyright (2001) Material Research

  10. 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.)

  11. Microbial activity in bentonite buffers. Literature study

    International Nuclear Information System (INIS)

    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.)

  12. Compression Tests on a Sandy Silt at Different Suction and Temperature Levels

    OpenAIRE

    François, B; Salager, S.; El Youssoufi, M. S.; Ubals Picanyol, D.; Laloui, L.; Saix, C.

    2007-01-01

    This paper presents a unified thermo-mechanical experimental study on a remoulded unsaturated sandy silt and brings a contribution to the understanding of the fundamental mechanics of unsaturated soils in non- isothermal conditions. The experimental program was carried out at four temperatures and four suction levels using two thermo-hydro-mechanical (THM) cells, one isotropic and the other oedometric. The effect of suction and temperature on the compressibility and on the apparent preconsoli...

  13. Thermo-plasticity of soils at various saturation states : a constitutive model

    OpenAIRE

    François, Bertrand; LALOUI, Lyesse

    2008-01-01

    This paper presents a highly-coupled thermo-plasticity model for unsaturated soils. The effect of temperature on the mechanics of unsaturated soils is briefly addressed. Then the equations of the developed model, so-called ACMEG-TS, are detailed. Finally, the model is validated by the means of comparisons with experiments. This constitutive model constitutes an effective tool for modelling the thermo-hydro-mechanical (THM) behaviour of geomaterials involved in the confinement of nuclear waste...

  14. Formulation for the THMC analysis of clayey materials: application to radioactive waste disposal

    OpenAIRE

    Gens Solé, Antonio; Guimarães, Leonardo do N; Fernández, A.M.; Sánchez, M.; Olivella Pastallé, Sebastià

    2008-01-01

    A fully coupled formulation combining reactive transport and an existing thermo-hydro-mechanical (THM) code is briefly described. Special attention has been given to phenomena likely to be encountered in clay barriers used as part of containment systems of nuclear waste. The types of processes considered in the chemical formulation include hydrolysis, complex formation, oxidation/reduction reactions, acid/base reactions, precipitation/dissolution of minerals and cation exchange. Both kinetica...

  15. THMC analysis of saturation and heating processes of an expansive clay barrier in radioactive waste isolation

    OpenAIRE

    Guimarães, Leonardo do N; Gens Solé, Antonio; Sánchez, M.; Olivella Pastallé, Sebastià

    2010-01-01

    A fully coupled formulation combining reactive transport and an existing thermo- hydro-mechanical (THM) code is briefly described. Special attention has been given to phenomena likely to be encountered in clay barriers used as part of containment systems of nuclear waste. The types of processes considered in the chemical formulation include hydrolysis, complex formation, oxidation/reduction reactions, acid/base reactions, precipitation/dissolution of minerals and cation exchange. Both kine...

  16. Ion diffusion in compacted bentonite

    International Nuclear Information System (INIS)

    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, Kd, 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.)

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

    International Nuclear Information System (INIS)

    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.

  18. Enhancement of the bentonite sorption properties

    Energy Technology Data Exchange (ETDEWEB)

    Mockovciakova, Annamaria, E-mail: mocka@saske.sk [Institute of Geotechnics, Slovak Academy of Sciences Watsonova 45, 04354 Kosice (Slovakia); Orolinova, Zuzana [Institute of Geotechnics, Slovak Academy of Sciences Watsonova 45, 04354 Kosice (Slovakia); Skvarla, Jiri [Institute of Montaneous Sciences and Environmental Protection, Technical University in Kosice, Park Komenskeho 19, 04200 Kosice (Slovakia)

    2010-08-15

    The almost monomineral fraction of bentonite rock-montmorillonite was modified by magnetic particles to enhance its sorption properties. The method of clay modification consists in the precipitation of magnetic nanoparticles, often used in preparing of ferrofluids, on the surface of clay. The influence of the synthesis temperature (20 and 85 deg. C) and the weight ratio of bentonite/iron oxides (1:1 and 5:1) on the composite materials properties were investigated. The obtained materials were characterized by the X-ray diffraction method and Moessbauer spectroscopy. Changes in the surface and pore properties of the magnetic composites were studied by the low nitrogen adsorption method and the electrokinetic measurements. The natural bentonite and magnetic composites were used in sorption experiments. The sorption of toxic metals (zinc, cadmium and nickel) from the model solutions was well described by the linearized Langmuir and Freundlich sorption model. The results show that the magnetic bentonite is better sorbent than the unmodified bentonite if the initial concentration of studied metals is very low.

  19. Migration behavior of iodine in compacted bentonite

    International Nuclear Information System (INIS)

    When the wastes that include I-129 dispose, compacted bentonite would be used as buffer material as well as for HLW disposal. Therefore in this study diffusion experiments were carried out to investigate the migration behavior of iodine in compacted bentonite. Bentonite used in this study consists of more than 95 % of sodium montmorillonite. Bentonite powder was compacted into a cylinder with a diameter of 10 mm and a height of 10 mm with a varied dry density. After saturated with water including 0.01 M of NaCl for one month, approximately 10 micro liters of tracer solution I- or IO3- were spiked on a surface of compacted bentonite respectively. The constant boundary concentrations and the diffusion coefficients of I- and IO3- were determined by the penetration method. Iodine profiles showed typical shape of error function complement. The constant boundary concentration of I- is several times larger than that of IO3-. This could be cause by geometrical limitation and/or anion exclusion of montmorillonite because IO3- is larger than I- and montmorillonite has negative surface charge. Apparent diffusion coefficients of I- and IO3- were obtained in the range of 27.0 to 192.9 μm2/s and 9.8 to 117.4 μm2/s, respectively. (author)

  20. Bentonite-amended soil special study

    International Nuclear Information System (INIS)

    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 CLAYMAXR, 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

  1. Sealing performance of bentonite and bentonite/crushed rock borehole plugs

    Energy Technology Data Exchange (ETDEWEB)

    Ouyang, S.; Daemen, J.J.K. [Arizona Univ., Tucson, AZ (United States). Dept. of Mining and Geological Engineering

    1992-07-01

    This study includes a systematic investigation of the sealing performance of bentonite and bentonite/crushed rock plugs. American Colloid C/S granular bentonite and crushed 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 a composition to yield a permeability lower than 5 {times} 10{sup {minus}8} cm/s 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 significant effect on the sealing performance within the test range from room temperature to 600{degree}C. Piping damage to the sealing performance is small if the maximum hydraulic gradient does not exceed 120 and 280 for samples with a bentonite content of 25 and 35%, 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 plug design. A permeability model is developed for the prediction of permeability in clays, especially in view of the difficulties in obtaining this property experimentally. A piping model is derived based on plastic flow theory. This piping model permits the estimation of critical hydraulic gradients at which flow of bentonite takes place. The model can also be used to define the maximum allowable pore diameter of a protective filter layer.

  2. Sorption of metals on zeolites and bentonite

    International Nuclear Information System (INIS)

    This contribution presents the recently obtained results on the sorption of heavy metals by natural microporous materials (especially zeolites and bentonite) of different origin. The sorption of caesium and strontium from its aqueous solutions by ten clinoptilolite-mordenite-containing sedimentary materials from Slovakia, Bulgaria, Ukraine and Greece and bentonite was investigated a batch-type procedure and radiotracer techniques. The experimental results provide information on suitability of the individual materials for the treatment of radioactive waste and their application as backfills in potential nuclear waste repositories. Furthermore, the sorption of cadmium, mercury and zinc-ions by zeolites and bentonite was investigated using batch techniques and radioactive tracers. Uptake values and distribution coefficients were calculated in order to study the suitability of these materials for utilization in the environmental technology (i.g. treatment of industrial waste). (author)

  3. MANU. Purchase of Bentonite. Process Description

    International Nuclear Information System (INIS)

    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.)

  4. Erosion properties and dispersion-flocculation behavior of bentonite particles

    International Nuclear Information System (INIS)

    Experimental and theoretical studies have been performed to clarify the ability of flowing groundwater in contact with bentonite to generate bentonite colloidal particles and disperse such colloids. This information is required to determine (a) the long-term stability of bentonite as a buffer material for borehole disposal of radioactive wastes in deep geologic media and (b) the potential influence of bentonite colloidal particles on radionuclide transport, specifically for use in scenario analyses in the performance assessment of waste disposal. In this study, the minimum groundwater velocity required to erode particles of Na-bentonite or Ca-bentonite from a bentonite surface in contact with groundwater was derived from shear strengths of aqueous bentonite gel suspensions, as determined by viscometer tests. The shear strengths were used to estimate the corresponding shear force on bentonite particle-particle bonds, using an estimated value for the number of initial bentonite particle-particle bonds in the experimental systems studied. The derived shear force was converted to corresponding groundwater velocity by using Stokes' equation and simplifying assumptions. The results indicate that groundwater velocities in a range of about 10-5 to 10-4 m/s would be required to initiate bentonite erosion. This range is higher than the groundwater flow velocity generally found in deep geologic media in Japan. In addition, known groundwater electrolyte concentrations were compared with theoretical estimates of aqueous electrolyte concentrations required to flocculate colloidal bentonite particles (for example 1 x 10-3 mol/l Na+). The comparison indicates that, even if erosion of bentonite occurred, the colloidal bentonite particles formed would flocculate. As a result, this study has shown that the effect of bentonite colloids on radionuclide transport is likely to be negligible in the performance assessment of radioactive waste disposal in deep geologic media

  5. 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.

  6. Preparation and characterization of bentonite organo clay

    International Nuclear Information System (INIS)

    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)

  7. Retention of chromium by modified Al-Bentonite

    OpenAIRE

    Volzone C.; Garrido L. B.

    2002-01-01

    Retention of chromium (III) from a tanning wastewater by modified Al-bentonites was studied. One bentonite from San Juan province, Argentina, was used. Al-bentonite was prepared by contact of bentonite with hydrolyzed OH-Al solutions (0.10 M in Al) for 24 hours. The modified Al-bentonites were obtained by: a) treatment with 0.5 M sodium chloride; b) with 0.5 M sodium chloride adjusted at pH 8; and c) treatment with an hexametaphosphate solution after sodium addition. Then, the samples were dr...

  8. Effects of silica sol on bentonite

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. Compacted bentonite will be used in Sweden as an engineered barrier in the disposal of nuclear waste, mainly due to bentonites sorption and swelling capacity, where the latter property is warranted in order to seal possible future intersecting fractures. However during the actual construction and deposition period other grouting agents must be used in order to seal already existing fractures. In Sweden Silica sol is currently being investigated in situ at Aespoe Hard Rock Laboratory as a fine fracture (< 100 μm) grouting agent by injection. During this period, there is a plausible risk of Silica sol coming into contact with bentonite. The effect of Silica sol, either in colloidal form or as a gel, on the chemical and physical properties of bentonite has not been properly addressed and has to be further investigated. The Silica sol (Meyco MP320, EKA Chemicals) consists of amorphous SiO2 particles, average size approximately 20 nm. Due to the small particle size Silica sol can penetrate and seal finer fractures than more coarse grouting agents commonly used. Upon injection NaCl (approx 0.3 M) is used as a gel accelerator, leading to a hydrological barrier in the form of a ductile gel after < 1 hour, which then hardens with time (months) increasing its strength significantly, depending on water content, ionic strength and temperature. Upon aggregation, either due to high ionic strength or drying, the silica colloids aggregate seemingly irreversible forming siloxane bonds by condensation of the silanol surface groups. These silanol groups can react at the montmorillonite edges in a similar way. In a worst case scenario the Silica sol would act as an inorganic glue, creating a pillared montmorillonite or modify the edges of the clay particles. Such effects would irreversibly reduce the overall swelling capacity of the affected bentonite. An experimental program has been developed to characterize the Silica sol

  9. Manufacture and homogeneity of highly dense bentonite samples

    International Nuclear Information System (INIS)

    A project study on behalf of Nagra for high radioactive waste disposal in deep geological formations as well as literature studies have shown that bentonite could be a suitable filling and sealing material. The Institute for Foundation and Soil Mechanics of the Swiss Institute of Technology is under contract by Nagra to investigate different bentonites. The investigations concentrate on the Na-bentonite MX-80 from Wyoming, which is foreseen by the Swedes, and on the geographically more favorable Ca-bentonite Montigel from Bavaria. Montigel powder and granulate, which show certain manufacturing advantages, were investigated. Numerous experiments, mostly for manufacturing of sample bodies for swelling experiments, were performed and evaluated with the aim to clarify the condensation properties of bentonites in a highly dense field. Especially the relationship between water content, pressure and attained dry density for the three bentonites: MX-80 (granulate), Montigel (powder) and Montigel K (granulate) were investigated. It was shown that the delivery water contents of the three bentonites favorably lie within the 8-10 % necessary to prepare high density samples with dry densities of about 2.0 Mg/m3. The comparison of the three bentonites shows that both bentonites in granular form allow lower pressures at condensation than the bentonite in powder form. Based on x-ray and pressure porosimetry investigations the high density bentonites are largely homogeneous sample bodies considering their density and pore radius distribution. 15 figs., 2 tabs

  10. 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.

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

    International Nuclear Information System (INIS)

    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

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

    International Nuclear Information System (INIS)

    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

  13. Ion-migration through bentonite/zeolite and bentonite/quartz sand mixture

    International Nuclear Information System (INIS)

    In the geological disposal system of the high level radioactive wastes radionuclides begin leaching from the waste form when the canister is degraded by corrosion. The buffer materials, as one of the engineered barriers can retard the migration of the radionuclides to the biosphere. In this study, the diffusivity of radionuclides has been obtained in the compacted clay materials, such as mixtures of bentonite-zeolite, and bentonite-quartz sand for buffer materials. For the bentonite and zeolite mixture, Kd-value for cesium has been increasing with zeolite contents. The increase in the Kd-value has also been obtained for strontium, though the inclination is found to be smaller than that for cesium. In the case of bentonite and quartz sand mixture, the Kd-value has increased with quartz content (up to 70%), though the increasing rate is smaller than that in the zeolite mixture. The purpose of the quartz sand mixing is to improve the thermal conductivity of the buffer materials. It is to be noted that the sorption capability of bentonite and quartz sand mixture is found to be a little bit larger than that of bentonite. As for cesium, the Kd-values obtained in diffusion experiment agree well with those from batch experiments within a factor of 2, while for strontium good agreement has not been obtained

  14. Ga migration through MX-80 bentonite

    International Nuclear Information System (INIS)

    Highly compacted bentonite is known to let gas ghrough at a very low rate but earlier invetigations have indicated the possible existence of a critical gas pressure at which the gas forms highly conductive passages through the clay. The present study was primarily aimed at testing the hypothesis of the critical pressure concept by measuring the gas pressure, and by trying to identify microstructural evidence of how gas percolates clay. Eight tests were run with MX-80 bentonite saturated with strongly brackish NAGRA water, the density of the water saturated bentonite ranging from 1.7 to somewhat more than 2.1 t/m3. In all the tests it was observed that gas break-through, manifested by largely increased conductivity, took place at a gas pressure of the same order of magnitude as the swelling pressure. One of the samples was analysed with respect to the microstructure and it revealed the existence of discrete gas-filled voids, some of which released gas when the trimmed clay specimen was placed into the embedding substance used for the microstructural analysis. This confirms that gas percolates through a number of narrow passages that are formed when the gas pressure is sufficiently high. In soft and medium-dense bentonite the 'capillary retention' is probably the major resistance to gas propagation, while in dense bentonite the penetrating gas has to make its way by displacing clay aggregates. In the latter case the critical gas pressure is therefore logically very high and close to the swelling pressure. (author)

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

    International Nuclear Information System (INIS)

    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 Fe2+ 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/cm3 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 temperatures. The

  16. pH buffering in compacted bentonite

    International Nuclear Information System (INIS)

    In almost all high-level waste and spent fuel repository concepts, highly compacted bentonite in one form or another is the preferred material for backfilling and sealing. During re-saturation the bentonite swells and seals against the emplacement tunnels. The very low transmissivity to water movement and good sorption characteristics make compacted bentonite an extremely effective near-field diffusion barrier to the movement of radionuclides. The ability to give a chemically well founded pore water composition is essential since such knowledge is a pre-requisite for understanding sorption and diffusion processes, assessing the influence of long term groundwater-bentonite interactions and also predicting near-field solubilities and developing sorption data bases. In this context the pH of the pore water is of central importance, particularly for sorption. Almost invariably the compositions given for highly compacted bentonite pore waters are calculated values because reliable water samples are virtually impossible to obtain, even by squeezing under very high pressures. Assumptions and simplifications are made in the geochemical models used to perform such calculations and the predictions are seldom if ever tested. One of the main hypotheses in a recently proposed model for bentonite pore water was that the initial pH is determined by the state of the amphoteric surface hydroxy groups, ≡SOH type sites, and these buffer the pH of the pore water in to a value close to 8. Surface site types, site capacities and proto-lysis constants were obtained from previous montmorillonite titration measurements and were fixed in the calculations. The aim of this work was to test the Bradbury and Baeyens (2003) model in terms of its ability to the predict one of the most important parameters for any pore water, namely the pH. Tests against the real system are not practicable for the reasons mentioned above. Hence the experiments had to be indirect but nevertheless devised to

  17. Evaluation of factors affecting diffusion in compacted bentonite

    International Nuclear Information System (INIS)

    The information available from the open literature and studies on exclusion, sorption and diffusion mechanisms of ionic and neutral species in bentonite has been compiled and re-examined in relation to the microstructure of bentonite. The emphasis is placed on a more thorough understanding of the diffusion processes taking place in compacted bentonite. Despite the scarcity of experiments performed with neutral diffusants, these imply that virtually all the pores in compacted bentonite are accessible to neutral species. Anion exclusion, induced by the overlap of electrical double layers, may render the accessible porosity for anions considerably less than the porosity obtained from the water content of the clay. On the basis of the compiled data, it is highly probable that surface diffusion plays a significant role in the transport of cations in bentonite clays. Moreover, easily soluble compounds in bentonite can affect the ionic strength of porewater and, consequently, exclusion, equilibrium between cations, and surface diffusion

  18. Development and validation of THM coupling model of methane-containing coal

    Institute of Scientific and Technical Information of China (English)

    Tao Yunqi; Xu Jiang; Liu Dong; Liang Yongqing

    2012-01-01

    Based on nine necessary basic assumptions for THM coupling model,this research comprehensively applied the theories of elastic mechanics,seepage mechanics and heat transfer,and established a real three-field and two-way coupled mathematical model to reveal the connections among seepage field,deformation field and temperature field within the system of methane-containing coal.In comparison between numerical and analytical solutions,the coupling modeling for THM of methane-containing coal was proved to be correct by model application in the physical simulation experiment of coal and gas outburst.The model established in this paper was the improvement of traditional seepage theory of methane-containing coal and fluid-solid coupled model theory,which can be widely used in prevention of coal and gas outburst as well as exploitation of coal bed methane.

  19. GTRF Calculations Using Hydra-TH (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 body-fitted computational meshes have been generated by Numeca's Hexpress/Hybrid, a.k.a. 'Spider', meshing technology for the V5H 3x3 and 5x5 rod bundle geometry 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 3x3 and 5x5 geometries, using different mesh resolutions. The results analyzed show good agreement with Star-CCM+ simulations and experimental data.

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

    International Nuclear Information System (INIS)

    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.

  1. GTRF Calculations Using Hydra-TH (THM.CFD.P5.05)

    International Nuclear Information System (INIS)

    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 body-fitted computational meshes have been generated by Numeca's Hexpress/Hybrid, a.k.a. 'Spider', meshing technology for the V5H 3x3 and 5x5 rod bundle geometry 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 3x3 and 5x5 geometries, using different mesh resolutions. The results analyzed show good agreement with Star-CCM+ simulations and experimental data.

  2. 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.

  3. Iron content and reducing capacity of granites and bentonite

    International Nuclear Information System (INIS)

    The iron contents in various granites and in bentonite have been determined. For granites, the content is usually in the range 1-9% (weight) and 2.5-3% for bentonite. Most of the iron is divalent in the granites (70-90%); in bentonite the divalent fraction is 25-50%. A large part of the divalent iron in the granites appears to be accessible for the reduction of dissolved oxygen in an aqueous system. (author)

  4. Mechanical Properties of Plastic Concrete Containing Bentonite

    OpenAIRE

    Peng Zhang; Qiaoyan Guan; Qingfu Li

    2013-01-01

    Plastic concrete consists of aggregates, cement, water and bentonite, mixed at a high water cement ratio, to produce a ductile material. It is used for creating an impermeable barrier (cut-off wall) for containment of contaminated sites or seepage control in highly permeable dam foundations. The effects of water to binder ratio and clay dosage on mechanical properties of plastic concrete were investigated. The results indicate that the water to binder ratio and clay dosage have great influenc...

  5. Bentonites in powder detergents: softness and perfum

    OpenAIRE

    Bernal, Cristóbal; Carrión Fité, Francisco Javier

    2011-01-01

    The sodium bentonite is a mineral composed by hydrated aluminium silicates with a great capacity for absorbing several types of substrates. In cotton articles, softeners are added after the washing process. Softeners are organic products which are absorbed within the last rinse. These types of softeners can present some disadvantages as the possible lack of biodegradability, solidity and higher hydrophobicity which might reduce the sensation of comfort in the clothes as water absorption is di...

  6. Borehole sealing with highly compactd Na bentonite

    International Nuclear Information System (INIS)

    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)

  7. Stability of bentonite gels in crystalline rock

    International Nuclear Information System (INIS)

    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 106 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)

  8. 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.

  9. Removal of Phosphate from Aqueous Solution with Modified Bentonite

    Institute of Scientific and Technical Information of China (English)

    唐艳葵; 童张法; 魏光涛; 李仲民; 梁达文

    2006-01-01

    Bentonite combined with sawdust and other metallic compounds was used to remove phosphate from aqueous solutions in this study. The adsorption characteristics of phosphate on the modified bentonite were investigated, including the effects of temperature, adsorbent dosage, initial concentration of phosphate and pH on removal of phosphate by conducting a series of batch adsorption experiments. The results showed that 98% of phosphate removal rate was obtained since sawdust and bentonite used in this investigation were abundantly and locally available. It is concluded that modified bentonite is a relatively efficient, low cost and easily available adsorbent for the removal of phosphate from aqueous solutions.

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

    International Nuclear Information System (INIS)

    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-Fe2O3 was identified by means of colorimetry. (author)

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

    Science.gov (United States)

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

    2016-04-01

    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.

  12. KAJIAN ADSORPSI LINEAR ALKYL BENZENE SULPHONATE (LAS DENGAN BENTONIT-KITOSAN

    Directory of Open Access Journals (Sweden)

    Miftah Rifai

    2013-11-01

    Full Text Available Deterjen pada umumnya tersusun atas surfaktan anionik seperti LAS (Linear alkyl Benzene sulphonate. pada percobaan ini LAS dapat menyerap sinar pada daerahuv dengan panjang gelombang maksimumnya adalah 223,5 nm. LAS dalam perairan dapat menimbulkan potensi masalah pencemaran.Tujuan dari penelitian ini adalah sebagai salah satu alternatif penanganan masalah pencemaran limbah domestik dengan cara menguji kinerja bentonit alam dan bentonit termodifikasi kitosan dalam mengadsorpsi LAS. Untuk mengetahui bahwa kitosan telah bereaksi dengan bentonit maka diuji dengan FTIR dan XRD pada bentonit alam dan bentonit-kitosan. Kemudian ditentukan waktu kontak optimum antara LAS dengan bentonit alam dan bentonit-kitosan. Serta penentuan isoterm adsorpsi LAS dengan bentonit alam dan bentonit-kitosan dengan cara membuat variasi konsentrasi larutan LAS. Uji kinerja bentonit alam dan bentonit-kitosan dalam mengadsorpsi LAS dilakukan dengan menggunakan sistem batch. Didapat waktu kontak optimum antara LAS berinteraksi dengan bentonit alam adalah 15 menit dengan kapasitas adsorpsi sebesar 3,265 mg/g. Sedangkan Waktu kontak optimum interaksi LAS dengan bentonit-kitosan terjadi pada waktu 15 menit dengan kapasitas adsorpsi sebesar 1,7mg/g. Dari hasil yang didapat maka dapat terlihat bahwa bentonit alam memiliki kapasitas adsorpsi yang lebih besar dibandingkan bentonit hasil modifikasi dengan kitosan. Interaksi antara bentonit alam dan bentonit–kitosan dengan LAS terjadi secara fisik dengan energi adsorpsi bentonit alam dengan LAS adalah 19,31 KJ/mol dan energi adsorpsi bentonit-kitosan dengan LAS adalah 19,60 KJ/mol.

  13. Hydrothermal alterations of Bentonites in Almeria (Spain)

    International Nuclear Information System (INIS)

    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)

  14. Study on bentonite-based buffer material of radioactive waste disposal facility. Influence of cement leachate on bentonite impermeability

    International Nuclear Information System (INIS)

    Cementitious materials and bentonite are planned for use as engineered barriers for the disposal of TRU waste from nuclear fuel reprocessing. When groundwater penetrates cementitious material, hyperalkaline water containing Ca ions may leach out and change bentonite physicochemically, resulting in degradation of its barrier performance. Furthermore, ion concentration of groundwater may increase due to dissolution of nitrate salt in some wastes. To investigate the hydraulic characteristics of bentonite under the disposal environment, hydraulic conductivity tests were performed using hyperalkaline solutions that imitate cement leachate and sodium nitrate solution. It was shown that ion concentration of permeant solution and exchangeable cation type of smectite had a large impact on bentonite impermeability. (author)

  15. Dual swelling mechanism model for saturated and unsaturated compacted bentonite

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. In the current concept of repository for radioactive waste disposal, compacted bentonite as well as bentonite-based material will be used as an engineered barrier mainly for inhibiting migration of radioactive nuclides. Since compacted bentonite swells when it is saturated, dry density of compacted bentonite will be redistributed and container of radioactive wastes will move during infiltration of underground water. Accurate evaluation of these events is effective in decreasing uncertainty in long term safety evaluation of radioactive waste facilities. However, sufficient evaluation is not conducted because behaviour of bentonite material during saturation process is not clarified sufficiently. Thus, stress-strain model of bentonite material during saturation process is proposed and applicability of the model is investigated. It is well known that compacted bentonite swells with large deformation by infiltration of water. Swelling behaviour of bentonite is mainly attributable to osmotic pressure caused by the difference between concentration of ions inside of montmorillonite flakes and that outside of montmorillonite flakes. Thus, swelling which is attributable to osmotic pressure is named 'swelling by osmotic pressure' here. By contrast, unsaturated ordinary clay swells or shrinks during infiltration of water without effect of osmotic pressure. Since this phenomenon is mainly attributable to reduction of suction during infiltration of water, it is reasonable to assume that unsaturated bentonite swells or shrinks during infiltration of water by reduction of suction. Thus, swelling which is attributable to reduction of suction is named 'swelling by reduction of suction' here. It is assumed in this paper that swelling by osmotic pressure occurs when bentonite is fully saturated, while swelling by reduction of suction occurs when bentonite is unsaturated. Swelling deformation under a constant vertical load is measured

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

    International Nuclear Information System (INIS)

    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)

  17. Influence of selected factors on strontium sorption on bentonites

    International Nuclear Information System (INIS)

    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 Ca2+ exhibit higher effect on cesium sorption than the Na2+ ions. Results indicate that the sorption of Sr2+ on bentonite will be affected by the presence of high concentrations of various salts in the waste water

  18. 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

    International Nuclear Information System (INIS)

    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 SKB should conduct further

  19. 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 the b

  20. Modelling the induced polarization of bentonite-sand mixtures

    OpenAIRE

    Leroy, Philippe; Ghorbani, Ahmad; Revil, André; Cosenza, P.; Okay, G.

    2014-01-01

    Spectral induced polarization (SIP) has become an increasingly popular geophysical method for hydrogeological and environmental applications. These applications include for instance the non-intrusive characterization of the textural and interfacial physicochemical properties of bentonites used as permeability barriers in landfills or to store various types of contaminants including radioactive wastes. Bentonites are mainly constituted of smectites, which have very high specific surface areas ...

  1. Filtration behavior of organic substance through a compacted bentonite

    International Nuclear Information System (INIS)

    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/cm3. 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)

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

    International Nuclear Information System (INIS)

    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/m3. Bentonite samples were immersed with distilled water and saturated before the experiments. The experiments for Se were carried out under N2 atmospheric condition (O2: 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 SeO32-, 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 HZrO3-. Distribution coefficient measured for Zr on the bentonite was about 1.0 m3/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

  3. Long-term Corrosion of Copper Container in Bentonite Buffer

    International Nuclear Information System (INIS)

    The experimental method for the evaluation of copper corrosion was discussed in this report. Especially, the corrosion behavior of a copper container in a compacted bentonite environment was reviewed in detail. Several previous studies on the copper corrosion in a bentonite environment were summarized and the applied methods were illustrated firstly. On the basis of the review, it is discussed how to execute long-term copper corrosion test as regarding korean disposal environment. The selection of bentonite medium and the composition of a medium such as bentonite-sand mixture or bentonite-sand double layer was mentioned in this report. The need for protection layer on copper surface was also discussed for reducing initial copper corrosion rate. As key aspects on the corrosion test, a measuring of corrosion rate, an observation of surface morphology, an analysis of corrosion product, and a measuring of corrosion potential were pointed out. For the purpose of a experimental consistency, the necessity of standard composition for a bentonite and a underground water might be confirmed before the test. Consequently, three experimental designs were derived for the corrosion test such as a corrosion testing design at creep condition, a simple corrosion design for the evaluation for other candidate materials, and lastly, a corrosion testing design in compacted bentonite. Through this survey and discussion for a copper corrosion in bentonite environment it would be very helpful for a high level radioactive waste disposal plan in the future

  4. Remediation of distilleries wastewater using chitosan immobilized Bentonite and Bentonite based organoclays.

    Science.gov (United States)

    El-Dib, F I; Tawfik, F M; Eshaq, Gh; Hefni, H H H; ElMetwally, A E

    2016-05-01

    Organic-inorganic nanocomposite, namely chitosan immobilized Bentonite (CIB) with chitosan content of 5% was synthesized in an acetic acid solution (2%). Organically modified CIB and Bentonite (mbent.) were prepared by intercalating cetyl trimethylammonium bromide (CTAB) as a cationic surfactant at doses equivalent to 1.5 and 3 times the cation exchange capacity (CEC) of clay. The prepared samples were characterized using FTIR, XRD and SEM to explore the interlayer structure and morphology of the resultant nanocomposites. The remediation of distilleries (vinasse) wastewater process was carried out using different adsorbents including CIB, modified CIB (mCIB), Bentonite (bent.), modified Bentonite (mbent.) and chitosan at different contact time. The results showed that the packing density of surfactant used in the synthesis of organoclays strongly affects the sorption capacity of the clay mineral and also showed that (mCIB)3 was found to be the most effective sorbent in the purification of distilleries wastewater with 83% chemical oxygen demand (COD) reduction and 78% color removal. PMID:26840179

  5. Effect of sulfuric acid concentration of bentonite and calcination time of pillared bentonite

    Science.gov (United States)

    Mara, Ady; Wijaya, Karna; Trisunaryati, Wega; Mudasir

    2016-04-01

    An activation of natural clay has been developed. Activation was applied by refluxing the natural bentonite in variation of the sulfuric acid concentration and calcination time of pillared bentonite (PLC). Calcination was applied using oven in microwave 2,45 GHz. Determination of acidity was applied by measuring the amount of adsorbed ammonia and pyridine. Morphological, functional groups and chrystanility characterizations were analyzed using SEM, TEM, FTIR and XRD. Porosity was analyzed using SSA. The results showed that the greater of the concentration of sulfuric acid and calcination time was, the greater the acidity of bentonite as well as the pore diameter were. FTIR spectra showed no fundamental changes in the structure of the natural bentonite, SEM, and TEM images were showing an increase in space or field due to pillarization while the XRD patterns showed a shift to a lower peak. Optimization was obtained at a concentration of 2 M of sulfuric acid and calcination time of 20 minutes, keggin ion of 2.2 and suspension of 10 mmol, respectively each amounted to 11.7490 mmol/gram of ammonia and 2.4437 mmol/gram of pyridine with 154.6391 m2/gram for surface area, 0.130470 m3/gram of pore volume and 3.37484 nm of pore diameter.

  6. Mineralogical investigations of Wyoming bentonite MX-80 and Montigel

    International Nuclear Information System (INIS)

    A project study for the final disposal of high-level radioactive wastes in deep geological formations, carried out on behalf of Nagra has shown that bentonite could serve as backfilling and sealing material for the final repository concept foreseen by Nagra. Subsequently, the Institute for Foundation and Ground Mechanics of the ETH-Zurich was charged by Nagra with the investigation of various bentonites. The investigations concentrated on the Na-bentonite MX-80 from Wyoming, which is favoured by the Swedes, and on the geographically more favourable Ca-bentonite Montigel from Bavaria. The mineral composition, surface, exchange capacity and exchangeable ions, charge distribution and density of both bentonites have been investigated

  7. Adsorption behavior of 239Pu by Gaomiaozi bentonite

    International Nuclear Information System (INIS)

    Adsorption behavior of 239Pu by Gaomiaozi bentonite as a function of the factors of aqueous phase pH value, 239Pu initial concentration and ionic species is studied by static adsorption experiments in this paper. The following results are obtained. Adsorption equilibrium time of 239Pu by Gaomiaozi bentonite samples is about 24 h, and the adsorption distribution ratio Kd value of 239Pu increases with the pH value, but decreases with increasing initial concentration of 239Pu. And adsorption of 239Pu by bentonite samples with different ionic species show that anions affect the most on adsorption of bentonite is CO32-, followed by HCO3- and SO42-, whereas Cl- and NO3- hardly have any influence on the adsorption of bentonite. (authors)

  8. Enhanced shear strength of sodium bentonite using frictional additives

    Energy Technology Data Exchange (ETDEWEB)

    Schmitt, K.E. [GeoSyntec Consultants, Huntington Beach, CA (United States); Bowders, J.J.; Gilbert, R.B. [Univ. of Texas, Austin, TX (United States); Daniel, D.E. [Univ. of Illinois, Urbana, IL (United States)

    1997-12-31

    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{sup -9} cm/sec, while increasing the shear strength parameters of the bentonitic mixture to {phi}{prime} = 17{degrees} and c{prime} = 0.

  9. Sorption of Cadmium on Na-Bentonite

    International Nuclear Information System (INIS)

    The sorption of Cd radionuclide into Na-bentonite as candidate for buffer material in the radioactive waste disposal system has been performed. Cadmium was used for this study as a model for bivalence elements. Batch experiment was adopted to study sorption isotherm, influence of carbonate and influence of EDTA. In a simple media, pure water, Cd was retained with a high affinity. Two stages Freundlich sorption isotherm was shown, with high coefficient distribution and sorption capacities. It is shown that the presence of carbonate in solution was not affect significantly to the sorption. While the presence of EDTA, decrease the distribution coefficient value. (author)

  10. Adsorption of aniline, phenol, and chlorophenols on pure and modified bentonite

    Science.gov (United States)

    Yildiz, A.; Gür, A.; Ceylan, H.

    2006-11-01

    In the present study, pure bentonite and bentonite modified by HNO3, EDTA, and HDTMA are adsorbents. The changes on the surfaces of bentonite samples are studied by IR spectroscopy. The adsorption of aniline, phenol, and phenol derivatives on these adsorbents is examined by means of gas chromatography. As the result of these examinations, it is seen that the adsorption capacities of clay-organic complexes (bentonite-EDTA and bentonite-HDTMA) are higher than those of bentonite-HNO3 and pure bentonite.

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

    International Nuclear Information System (INIS)

    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.

  12. 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.

  13. DECOVALEX Simulations Results Related to the Engineered Barrier System (EBS)

    International Nuclear Information System (INIS)

    Over the past decade SKI supported a collaborative research effort between Lawrence Berkeley National Laboratory (LBNL) and the Royal Institute of Technology (KTH) to provide SKI with independent codes and model experience for investigation of SKB's work on EBS. The emphasis is on coupled thermo-hydro-mechanical (THM) processes in the bentonite buffer and surrounding rock mass. Two numerical models are adapted and utilized for the studies of EBS. The first one is ROCMAS, which is a finite element code for three-dimensional analysis of coupled THM processes of unsaturated/saturation porous and fractured geological media. A version of this code has been tailor-made for a rigorous analysis of EBS including bentonite swelling and rock interaction. The second code is TOUGHFLAC, which has the capability of solving coupled THM problems under multi-phase flow conditions. The multi-phase flow capability means that it can used for studying migration of gas and its interaction with the liquid in more detail. The TOUGH-FLAC code utilizing two established codes; TOUGH2 for TH analysis and FLAC3D code for rock and soil mechanics analysis. Both ROCMAS and TOUGH-FLAC are currently applied to various problems within the DECOVALEX project. Participation in the DECOVALEX project has been extremely valuable for developing and strengthening SKI's ability of an independent examination of SKB's works on EBS. Thus, SKI currently has available these two numerical models that have the same capabilities as SKB's numerical models, and in certain aspects far exceeds the capabilities of SKB's numerical models. This is important because SKI needs not only to investigate what SKB do but also investigate what they are not doing, thus providing them with insightful comments and guidelines. Maybe the most important gain of the DECOVALEX project is the experience in solving realistic problems related to EBS, which provides experience and depths of knowledge for the future analysis of a real site

  14. Catalytic Polymerization of Acrylonitrile by Khulays Bentonite

    Directory of Open Access Journals (Sweden)

    Matar M. Al-Esaimi

    2007-04-01

    Full Text Available The aqueous polymerization of acrylonitrile (AN catalyzed with exchanged Khulays bentonite . The influence of various polymerization parameters ( e.g., concentrations of Potassium Persulfate (K2S2O8 and monomer , various of organic solvents, and different temperature has been investigated. It was found that the rate of polymerization of AN was found to be dependent on monomer concentration, initiator and temperature. The activation energy of polymerization was calculated .Thermal properties of the polymer were studied by TGA and DSC techniques. © 2007 CREC UNDIP. All rights reserved.Received: 5 February 2007; Received in revised: 19 April 2007; Accepted: 7 May 2007[How to Cite: M. M. Al-Esaimi. (2007. Catalytic Polymerization of Acrylonitrile by Khulays Bentonite. Bulletin of Chemical Reaction Engineering and Catalysis, 2 (2-3: 32-36.  doi:10.9767/bcrec.2.1.4.6-10][How to Link/DOI: http://dx.doi.org/10.9767/bcrec.2.1.4.6-10 || or local: http://ejournal.undip.ac.id/index.php/bcrec/article/view/4] 

  15. Sorption of Uranium(VI) and Thorium(IV) by Jordanian Bentonite

    OpenAIRE

    Fawwaz I. Khalili; Salameh, Najla'a H.; Mona M. Shaybe

    2013-01-01

    Purification of raw bentonite was done to remove quartz. This includes mixing the raw bentonite with water and then centrifuge it at 750 rpm; this process is repeated until white purified bentonite is obtained. XRD, XRF, FTIR, and SEM techniques will be used for the characterization of purified bentonite. The sorption behavior of purified Jordanian bentonite towards and Th4+ metal ions in aqueous solutions was studied by batch experiment as a function of pH, contact time, temperature,...

  16. 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.

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

    International Nuclear Information System (INIS)

    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

  18. Study on adsorption of 237Np on bentonite

    International Nuclear Information System (INIS)

    The performance of adsorbing 237Np for bentonite as buffer/backfill material was investigated. The adsorption coefficients of 237Np were determined for three kinds of bentonite under atmosphere and anoxic atmosphere. Further, it was studied that Kd values were affected by pH and CO32-. The results are shown as follows: (1) Distribution coefficients Kd under atmosphere: for mixed-bentonite is 47.3 mL/g, for Mg-bentonite 52.0 mL/g and for Ca-bentonite 42.4 mL/g; and the corresponding Kd under anoxic atmosphere: 89.3 mL/g, 38.8 mL/g and 29.0 mL/g, respectively. (2) When pH was lower than 9.2, Kd of the mixed-bentonite increased with the increase of pH and the maxi-mumt Kd value appeared at pH 9.2. (3) Kd of the mixed-bentonite got lower in high carbonate concentration when the total neptunium concentration was smaller than the solubility of NaNpO2CO3. (author)

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

    International Nuclear Information System (INIS)

    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

  20. Effects of polyethyleneimine adsorption on rheology of bentonite suspensions

    Indian Academy of Sciences (India)

    A Alemdar; N Öztekin; F B Erim; Ö I Ece; N Güngör

    2005-06-01

    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 their rheological properties and stability of bentonite suspensions were studied. The adsorption rates for the bentonite suspensions are very fast. The XRD results showed that the PEG molecules did not intercalate into the layers of the clay.

  1. Diffusion of chloride and uranium in compacted sodium bentonite

    International Nuclear Information System (INIS)

    The authors discuss the measurement of sorption and diffusion of chloride (Cl-36) and uranium in compacted sodium bentonite MX-80. No sorption was observed in the sorption tests, however, in the diffusion tests slight sorption of uranium was noticed. The diffusivities of Cl-36 were found to be strongly dependent on the compaction of bentonite and on the salt concentration of the solution. Ion-exclusion can propably explain these phenomena. The diffusivities of uranium were also strongly dependent on the compaction of bentonite. Uranium shows features of both ion-exclusion and sorption

  2. Growth of detector-grade CZT by Traveling Heater Method (THM): An advancement

    Energy Technology Data Exchange (ETDEWEB)

    ROY, U.N.; JAMES, R.; WEILER, S.; STEIN, J.; GROZA, M.; BURGER, A.; BOLOTNIKOV, A.E.; CAMARDA, G.S.; HOSSAIN, A.; YANG, G.

    2011-04-25

    In this present work we report the growth of Cd{sub 0.9}Zn{sub 0.1}Te doped with In by a modified THM technique. It has been demonstrated that by controlling the microscopically flat growth interface, the size distribution and concentration can be drastically reduced in the as-grown ingots. This results in as-grown detector-grade CZT by the THM technique. The three-dimensional size distribution and concentrations of Te inclusions/precipitations were studied. The size distributions of the Te precipitations/inclusions were observed to be below the 10-{micro}m range with the total concentration less than 10{sup 5} cm{sup -3}. The relatively low value of Te inclusions/precipitations results in excellent charge transport properties of our as-grown samples. The ({mu}{tau}){sub e} values for different as-grown samples varied between 6-20 x 10{sup -3} cm{sup 2}/V. The as-grown samples also showed fairly good detector response with resolution of {approx}1.5%, 2.7% and about 3.8% at 662 keV for quasi-hemispherical geometry for detector volumes of 0.18 cm{sup 3}, 1 cm{sup 3} and 4.2 cm{sup 3}, respectively.

  3. Gas transport through saturated bentonite and interfaces

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. The aim of this investigation was the determination of the gas transport properties of saturated compacted bentonite and its interfaces. The bentonite used was the Spanish FEBEX bentonite, which is mainly composed of montmorillonite (more than 90%). For a dry density of 1.6 g/cm3 the saturated permeability of the bentonite is about 5.10-14 m/s, with deionised water used as percolating fluid. The saturated swelling pressure for the same dry density has a value of about 6 MPa. To perform the gas breakthrough tests a series of stainless steel cells were designed and manufactured. The cells consisted of a body, in which the cylindrical sample was inserted, pistons with o-rings at both ends of the samples and threaded caps. The samples, of 3.8 and 5.0 cm in diameter and 2.5 or 5.0 in height, were obtained by uniaxial compaction of the bentonite with its hygroscopic water content directly inside the cell body. Saturation with deionised water was accomplished by applying injection pressures of between 2 and 10 bar. The water content of the bentonite after saturation was higher than 27% for all the dry densities. Once the samples saturated, the filters on top and bottom of the samples were replaced by dry ones, the cells were again closed, and they were connected to a setup specially designed to measure breakthrough pressure. It consisted of two stainless steel deposits connected to the ends of the cell. One of the deposits was pressurised with nitrogen at 2 bar, whereas vacuum was applied to the other one. The pressures were measured by means of pressure transmitters. If no changes in pressure were recorded during 24 h, the injection pressure in the upstream deposit was increased by 2 bar and kept constant for 24 h. The process was repeated until gas started to flow through the sample. The time required for the completion of a particular experiment was determined by the conditions of the sample being studied. Although

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

    International Nuclear Information System (INIS)

    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

  5. Experimental Setup to Characterize Bentonite Hydration Processes

    International Nuclear Information System (INIS)

    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

  6. Buffer construction technique using granular bentonite

    International Nuclear Information System (INIS)

    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/m3, 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)

  7. Influence of seawater on swelling characteristics of bentonite buffer material

    International Nuclear Information System (INIS)

    High-level-radioactive-waste disposal facility can be built on the coastal area. One reason is that transportation of the wastes is easy. Groundwater in the coastal zone which flows into disposal pit contains large amount of seawater salts. So, it is important to investigate the influence of seawater on bentonite buffer material which is one of the Barrier materials in the nuclear disposal facility. The purpose of this study is to investigate the influence of artificial seawater on swelling pressure and swelling deformation characteristics of five typical kinds of bentonites. Various factors, such as density, montmorillonite contents, sort of exchangeable-cation of the bentonite have been investigated. This experimental works clarified the some factors for which the influence of artificial sea water on swelling characteristics of bentonite depends. Based on experimental results, a specification for the buffer material which can overcome the influence of seawater was defined. (author)

  8. Diffusion of Fission Product Elements in Compacted Bentonite

    International Nuclear Information System (INIS)

    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)

  9. A study on the thermal conductivity of compacted bentonites

    CERN Document Server

    Tang, Anh-Minh; Le, Trung Tinh; 10.1016/j.clay.2007.11.001

    2008-01-01

    Thermal conductivity of compacted bentonite is one of the most important properties in the design of high-level radioactive waste repositories where this material is proposed for use as a buffer. In the work described here, a thermal probe based on the hot wire method was used to measure the thermal conductivity of compacted bentonite specimens. The experimental results were analyzed to observe the effects of various factors (i.e. dry density, water content, hysteresis, degree of saturation and volumetric fraction of soil constituents) on the thermal conductivity. A linear correlation was proposed to predict the thermal conductivity of compacted bentonite based on experimentally observed relationship between the volumetric fraction of air and the thermal conductivity. The relevance of this correlation was finally analyzed together with others existing methods using experimental data on several compacted bentonites.

  10. Modified Ponorogo bentonite for the removal of ampicillin from wastewater.

    Science.gov (United States)

    Rahardjo, Andi Kurniawan; Susanto, Maria Josephine Jeannette; Kurniawan, Alfin; Indraswati, Nani; Ismadji, Suryadi

    2011-06-15

    The adsorption of ampicillin onto natural and organo-bentonite was studied. Organo-bentonite was obtained by modifying the natural bentonite obtained from Ponorogo, Indonesia, using CTAB surfactant by microwave heating. The temperature dependent form of the Langmuir, Freundlich, Sips and Toth equations was employed to correlate equilibrium data. Based on the evaluation of the physical meaning of fitted isotherm parameters of each model, it is clear that Toth equation can represent the equilibrium data better than other models. The adsorption performance of natural and organo-bentonite for the removal of ampicillin from pharmaceutical company wastewater was also studied. In real wastewater, both adsorbents could not completely remove the ampicillin due to the sorption competition with other substances which also present in the wastewater. PMID:21550716

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

    International Nuclear Information System (INIS)

    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)

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

    International Nuclear Information System (INIS)

    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

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

    International Nuclear Information System (INIS)

    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)

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

    OpenAIRE

    Biljana Kovačević Zelić; Dubravko Domitrović; Želimir Veinović

    2007-01-01

    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 lo...

  15. The Effect of Bentonite on External Corrosion of Well Casings

    OpenAIRE

    Orayith, Mohammed

    2012-01-01

    ABSTRACTThe overall goal of this research is concerned with understanding the effects of bentonite on the external corrosion of bare mild steel well casing. Na-bentonite is mainly used in enormous amounts in drilling processes, so it used as the main electrochemical environment surrounding the casing at different condition. The major part of the current study was divided into 3 stages; the first stage is constant current cathodic protection (CP) with a range of 0.0 (Open Circuit Potential) to...

  16. The interaction of bentonite and glass with aqueous media

    International Nuclear Information System (INIS)

    It has been demonstrated that Si(OH)4 is an important constituent of bentonite. In bentonites natural state the Si(OH)4 in the bentonite is permeable to the diffusible components of the aqeous medium in contact with it. As a consequence, the pH of the medium is a sensitive function of its ionic strength. Permeability of the Si(OH)4 to salt is lost, however, by pretreatment of the bentonite with dilute acid to protonate fully the Si(OH)4. The pH-producing property of the Si(OH)4 then is associated with its surface properties. The glasses (ABS-39 and ABS-Y Marcoule) studied in this research program also contain hydroxylated oxide as an important constituent. These materials, however, are not observed to exhibit gel-like (three-dimensional) properties prior to or after acid pretreatment. Instead they function always as a surface (two-dimensional) and are impermeable to the diffusible components of the aqueous media that come in contact with them. As a result, the pH of the medium is depentdent on ionic strength only so far as it affects the counter-ion screening efficiency of the charged surface. In both systems, bentonite and glass, the pH of the medium is affected by the presence of CO2. The lowering of medium pH by CO2 dissolution results in the neutralization of Si(OH)4 in the untreated bentonite gel phase or in the surface of the acid pretreated bentonite or glass in contact with the medium. If glass and bentonite are in contact the action of CO2 at their interface results in both systems striving to reach different equilibria. The result is enhanced chemical reactivity at the interface. To minimize such reactivity CO2 must be excluded from the atmosphere in contact with the solid-liquid phases. (author)

  17. Unified theory for swelling deformation and swelling pressure of bentonite

    International Nuclear Information System (INIS)

    The correlation of the water volume to vertical overburden pressure (p) is obtained as Vw/ Vm=KÞDs-3 for bentonite with fractal-textured surface. The maximum swelling strain is predicted according to the correlation of the water volume to vertical overburden pressure. The predictions of the maximum swelling strain and swelling pressure are in satisfactory agreement with the experimental data of Tsukinuno and Wyoming bentonite. (authors)

  18. Sorption of strontium on bentonites from Slovak deposits

    International Nuclear Information System (INIS)

    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+, NH4+, Ca2+, Mg2+ and Ba2+ 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)

  19. Effect of activation on swelling property in Ca-bentonite

    International Nuclear Information System (INIS)

    Compacted bentonite is attracting greater attention as buffer material for deep geological repository of high-level radioactive waste under current design concept. Swelling behavior is a significant property in achieving the low-permeability sealing function. The potential buffer material used is a locally available clayey material known as Zhisin clay in Taiwan. Zhisin clay is a Ca-type bentonite. Experimental data indicated that the swelling potential of Zhisin clay is much lower than that of Na-bentonite due to its exchangeable cation type and capacity. To enhance the swelling potential of Zhisin clay, a cation exchange process by addition of Na2CO3 powder is introduced in this research. Addition of Na2CO3 reagent to Zhisin clay caused precipitation of CaCO3 to occur and induced a replacement of Ca2+ ions by Na+ ions on the surface of bentonite in liquid phase. Experimental results show that Na2CO3-activated Zhisin clay is superior in swelling potential to untreated Zhisin clay. Due to the ion exchange hysteresis, activated bentonite shows different type of time-swell curve from traditional sigmoid-shaped curve. The optimal amount of Na2CO3 addition is found to be 1%, and the maximum swelling strain was found to be 3 times as much as that of untreated Zhisin clay. The Na2CO3 -activated Zhisin clay exhibited improved resistance to thermal environments and behaved similar to the Na-type bentonites under different hydrothermal temperatures. (authors)

  20. Lot A2 test, THC modelling of the bentonite buffer

    Science.gov (United States)

    Itälä, Aku; Olin, Markus; Lehikoinen, Jarmo

    Finnish spent nuclear fuel is planned to be disposed of deep in the crystalline bedrock of the Olkiluoto island. In such a repository, the role of the bentonite buffer is considered to be central. The initially unsaturated bentonite emplaced around a spent-fuel canister will become fully saturated by the groundwater from the host rock. In order to assess the long-term safety of a deep repository, it is essential to determine how temperature influences the chemical stability of bentonite. The aim of this study was to achieve an improved understanding of the factors governing the thermo-hydro-chemical evolution of the bentonite buffer subject to heat generation from the disposed fuel and in contact with a highly permeable rock fracture intersecting a canister deposition hole. TOUGHREACT was used to model a test known as the long-term test of buffer material adverse-2, which was conducted at the Äspö hard rock laboratory in Sweden. The results on the evolution of cation-exchange equilibria, bentonite porewater chemistry, mineralogy, and saturation of the buffer are presented and discussed. The calculated model results show similarity to the experimental results. In particular, the spatial differences in the saturation and porewater chemistry of the bentonite buffer were clearly visible in the model.

  1. Lot A2 test, THC modelling of the bentonite buffer

    International Nuclear Information System (INIS)

    Finnish spent nuclear fuel is planned to be disposed of deep in the crystalline bedrock of the Olkiluoto island. In such a repository, the role of the bentonite buffer is considered to be central. The initially unsaturated bentonite emplaced around a spent-fuel canister will become fully saturated by the groundwater from the host rock. In order to assess the long-term safety of a deep repository, it is essential to determine how temperature influences the chemical stability of bentonite. The aim of this study was to achieve an improved understanding of the factors governing the thermo-hydro-chemical evolution of the bentonite buffer subject to heat generation from the disposed fuel and in contact with a highly permeable rock fracture intersecting a canister deposition hole. TOUGHREACT was used to model a test known as the long-term test of buffer material adverse-2, which was conducted at the Aespoe hard rock laboratory in Sweden. The results on the evolution of cation-exchange equilibria, bentonite pore water chemistry, mineralogy, and saturation of the buffer are presented and discussed. The calculated model results show similarity to the experimental results. In particular, the spatial differences in the saturation and pore water chemistry of the bentonite buffer were clearly visible in the model. (authors)

  2. Chitosan/bentonite bionanocomposites: morphology and mechanical behavior

    International Nuclear Information System (INIS)

    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)

  3. Behaviour of bentonite accessory minerals during the thermal stage

    Energy Technology Data Exchange (ETDEWEB)

    Arcos, David; Bruno, Jordi [Enviros-QuantiSci, Barcelona (Spain); Benbow, Steven; Takase, Hiro [Quintessa Limited, Henley-on-Thames (United Kingdom)

    2000-03-15

    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{sub 4}(aq) is the predominant aqueous species, then anhydrite dissolves at the initial groundwater migration times through bentonite. However, if Ca{sup 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.

  4. The oolitization rate determination of bentonite moulding mixtures

    Directory of Open Access Journals (Sweden)

    F. Miksovsky

    2008-07-01

    Full Text Available Bentonite mixtures belong and will always belong among the most widespread sand mixtures for the “green sand” technology of castings production. This technology’s essential advantage is bentonite mixtures application reversibility in the closed circulation after composition modifications and circulation losses replenishment. After the casting of a mould, the surrounding sand mixture is strained by the solidifying casting heat and bentonite degradation occurs. In case of appropriate conditions the oolitization occurs. This phenomenon is specific only for bentonite-bonded mixtures. The oolitization of opening material silica grains brings a number of negative as well as positive features with it. It is not only a technological problem but economical and ecological as well because for minimization of mixture regeneration with a help of new sand it is necessary to know bentonite mixtures quality control tools even in term of the oolitization rate. This paper deals with the description of undemanding physical method of the oolitization rate evaluation with a help of powder density assessment and its examination with actual sand mixtures which were obtained from the Czech Republic foundry plants. There are foundry plants of heavier weight castings and in one case there was an operation where bentonite mixtures regeneration was applied. Moreover, the oolitization effect on metal penetration in test castings was verified.

  5. Study on Preparation and Properties of Grease Based on Ultraifne Bentonite Powder

    Institute of Scientific and Technical Information of China (English)

    Wang Jing; Guo Xiaochuan; Jiang Mingjun; He Yan

    2016-01-01

    The feasibility for preparation of ultraifne bentonite powder by different milling methods was studied. And the comparison of comprehensive performance between ultraifne bentonite grease and traditional bentonite grease was also investigated. The results indicated that the statistic Z-average size of ultraifne bentonite prepared by sand milling was 250 nm with a narrow size distribution and the lattice structure of ultraifne bentonite maintained good character despite a slight distortion occasioned. The mechanical stability, colloid stability, antiwear ability and friction-reducing property of ultraifne bentonite grease were superior to the traditional one.

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

    International Nuclear Information System (INIS)

    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

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

    International Nuclear Information System (INIS)

    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 SiO2 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 extensive

  8. UTILITY OF THE METHOD T.H.M. (MACHINE - HOUR - RATE PRODUCTION CENTURY PROCESS AUTOMATION

    Directory of Open Access Journals (Sweden)

    Cristina-Otilia, ȚENOVICI

    2014-11-01

    Full Text Available The method T.H.M. (machine - hour - rate gives greater accuracy in the factories or departments, where production is largely by machinery. In the specialty literature, the notion of price - the time - the car is defined as "œa rate calculated by dividing the budgeted or estimated overhead or labour and overhead cost attributable to a machine or group of similar machines by the appropriate number of machine hours. The hours may be the number of hours for which the machine or group is expected to be operated, the number of hours which would relate to normal working for the factory, or full capacity". In a highly mechanised cost centre, majority of the overhead expenses are incurred on account of using the machine, such as, depreciation, power, repairs and maintenance, insurance, etc. This method is currently offering the most equitable basis for absorption of overheads in machine intensive cost centres.

  9. Electrochemical removal of bromide and reduction of THM formation potential in drinking water.

    Science.gov (United States)

    Kimbrough, David Eugene; Suffet, I H

    2002-11-01

    Trihalomethanes (THMs), a by-product of the chlorination of natural waters containing dissolved organic carbon and bromide, are the focus of considerable public health concern and regulation due to their potential as a carcinogen by ingestion. This paper presents a promising new water treatment process that lowers the concentration of bromide in drinking water and thus, lowers the THM formation potential. Bromide is oxidized by electrolysis to bromine and then the bromine apparently volatilized. The electrolyzed water, when chlorinated, produces measurably lower amounts of THMs and proportionately fewer brominated THMs, which are of greater public health concern than the chlorinated THMs. Removing bromide should also reduce the formation of other disinfection by-products such as bromate and haloacetic acids. PMID:12448534

  10. 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.

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

    International Nuclear Information System (INIS)

    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.

  12. 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

  13. Mechanisms and models for bentonite erosion

    International Nuclear Information System (INIS)

    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

  14. Modification of bentonite with cationic surfactant for the enhanced retention of bisphenol A from landfill leachate.

    Science.gov (United States)

    Li, Yi; Jin, Fenglai; Wang, Chao; Chen, Yunxiao; Wang, Qing; Zhang, Wenlong; Wang, Dawei

    2015-06-01

    Bentonite was modified with cationic surfactant hexadecyl trimethyl ammonium bromide (HTAB) as landfill liner to retard the transportation of bisphenol A (BPA) for the first time. The modification was confirmed to form a lateral bi-layer in the interlayer space of bentonite by scanning electron microscope, X-ray diffraction, and Fourier transform infrared spectroscopy. The introduction of HTAB into the internal position of bentonite led to an increased interlayer space of bentonite from 15.0 to 20.9 Å and a higher sorption affinity for BPA (10.449 mg/g of HTAB-bentonite and 3.413 mg/g of raw bentonite). According to the Freundlich model, the maximum adsorption capacity of the HTAB-bentonite was found to be 0.410 mg/g. The sorption capacity of raw bentonite and HTAB-bentonite both decreased at alkaline conditions. Although the hydraulic conductivity of HTAB-bentonite was higher than that of raw bentonite, results of laboratory permeability and column tests indicated that HTAB-bentonite obviously extended the BPA breakthrough time by 43.4 %. The properties of the HTAB-bentonite revealed its notable advantages as components of landfill liners material to retain BPA in leachate. PMID:25874420

  15. Numerical analysis for heating and infiltration test at model deposition hole in underground hard rock laboratory

    International Nuclear Information System (INIS)

    Various insitu tests for the safety disposal of radioactive waste are conducted in the Swedish underground hard rock laboratory. Canister Retrieval Test (CRT) is a heating and infiltration test at a full-scale deposition hole. In this paper, we conducted thermo-hydro-mechanical coupled analysis for CRT and compared the results with measured data. The evolution of temperature and relative humidity and the profiles of bentonite's dry density were well reproduced by numerical analysis. Sensitivity analysis was also conducted in order to investigate the influence of hydraulic properties of surrounding rock mass on re-saturation behavior of bentonite in a deposition hole. (author)

  16. Diffusion in crushed rock and in bentonite clay

    International Nuclear Information System (INIS)

    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 m2/s and 6.0*10-12 m2/s, respectively, but these values are questionable, as experimental results good enough for fitting are not available. (orig.). (74 refs., 27 figs., 12 tabs.)

  17. Adsorption of cesium and strontium on natrified bentonites

    International Nuclear Information System (INIS)

    The influence of chemical activation-natrification of bentonites on adsorption of Cs and Sr was studied with regards to utilization of bentonites for depositing high-level radioactive waste and spent nuclear fuel. Bentonite samples from three Slovak deposits in three different grain-size (15, 45 and 250 μm), natural and natrified forms (Na-bentonites); under various experimental conditions, such as contact time, adsorbent and adsorbate concentration have been studied. When comparing the Na-bentonites and their natural analogues, the highest adsorbed Cs and Sr amounts were reached on the natrified samples. After the Sr adsorption a drop in the pH equilibrium value was observed together with the increase of the initial Sr concentration. A disadvantage of the natrified bentonite forms is formation of colloid particles. After 2 h of phase mixing a gentle turbidity was observed as well as formation of a gel-like form. The above findings were confirmed by observing the particle distribution in dry and wet dispersion and centrifugation at two different speeds. Natrification as a technological process of bentonite quality improvement cannot be applied when constructing a long-term repository for high-level radioactive waste and spent nuclear fuel. The main problem of natrification is a technological process which leads to a significant pH increase. Alkaline environment in combination with the K presence and increased temperature in the vicinity of radio-active waste can lead to a rapid illitization of smectite and loss of the original adsorption qualities. Moreover, sodium additions are a significant point of uncertainty since it is not possible to state what amount of Na enters the interlayer space and what amount stays in the inter-partition space. (author)

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

    International Nuclear Information System (INIS)

    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)

  19. Performance characteristics of EZhou bentonite of Hubei province and its modification

    Institute of Scientific and Technical Information of China (English)

    Long Wei; Fan Zitian; Hu Xueting

    2009-01-01

    Both the chemical compositions and performance characteristics of the bentonite raw ores in Ezhou area of Hubei province and Honghuoshan area of Liaoning province were compared and analyzed. The properties of these two kinds of bentonites were tested before and after Na+- and Li+-modification. The results show that the Ezhou bentonite ore possesses higher montmorillonite content than the Honghuoshan bentonite ore, but the Ezhou Na-bentonite has weaker castability (e.g. Wet compression strength and hot wet tensile strength) than the Honghuoshan Na-bentonite, while the performance of Ezhou Li-bentonite, such as colloid index, swelling value, swelling volume and mould coating performance, is equivalent to that of the Honghuoshan Na-bentonite.

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

    International Nuclear Information System (INIS)

    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

  1. Geochemical discrimination of the Upper Ordovician Kinnekulle Bentonite in the Billegrav-2 drill core section, Bornholm, Denmark

    Directory of Open Access Journals (Sweden)

    Tarmo Kiipli

    2014-12-01

    Full Text Available The content of the trace elements Ti, Nb, Zr and Th has been analysed in 34 Upper Ordovician bentonites from the Billegrav-2 drill core, Bornholm, Denmark. The section contains two 80–90 cm thick bentonites, which potentially may represent the Kinnekulle Bentonite, as well as several rather thick but composite bentonite layers with thin terrigenous shale interbeds. Comparison of the four immobile trace elements with data from the Kinnekulle Bentonite reported from other locations in Baltoscandia indicate that the 80 cm thick bentonite between 88.30 and 89.10 m in the Billegrav-2 core represents this marker bed. The other thick (90 cm bentonite in the Billegrav-2 core, exceeding the thickness of the Kinnekulle Bentonite, belongs to the Sinsen or uppermost Grefsen Series bentonites. Bentonites in the Grefsen Series frequently contain much higher concentrations of trace elements than the Kinnekulle Bentonite.

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

    International Nuclear Information System (INIS)

    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

  3. 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

  4. Radioassay of vitamin B-12 employing bentonite

    International Nuclear Information System (INIS)

    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

  5. Measurement of pH of the Compacted Bentonite under the Reducing Condition

    OpenAIRE

    Nessa, Syeda Afsarun; Idemitsu, Kazuya; Yamasaki, Yosuke; Inagaki, Yaohiro; Arima, Tatsumi

    2007-01-01

    Compacted bentonite and carbon steel have been considered as the good buffer and over-pack materials in the repositories of high-level radioactive waste disposal. Sodium bentonite, Kunipia-F contains approximately 95wt% of montmorillonite. It has a high cation-exchange capacity and a high specific surface area, and its properties determine the behavior of bentonite. The pH of the pore water in compacted bentonite is an extremely important parameter because of its influence on radionuclide sol...

  6. 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

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

    International Nuclear Information System (INIS)

    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)

  8. ADSORPTION FROM AQUEOUS SOLUTION ONTO NATURAL AND ACID ACTIVATED BENTONITE

    Directory of Open Access Journals (Sweden)

    Laila Al-Khatib

    2012-01-01

    Full Text Available Dyes have long been used in dyeing, paper and pulp, textiles, plastics, leather, paint, cosmetics and food industries. Nowadays, more than 100,000 commercial dyes are available with a total production of 700,000 tones manufactured all over the world annually. About 10-15% of dyes are being disposed off as a waste into the environment after dyeing process. This poses certain hazards and environmental problems. The objective of this study is to investigate the adsorption behavior of Methylene Blue (MB from aqueous solution onto natural and acid activated Jordanian bentonite. Both bentonites are firstly characterized using XRD, FTIR and SEM techniques. Then batch adsorption experiments were conducted to investigate the effect of initial MB concentration, contact time, pH and temperature. It was found that the percentage of dye removal was improved from 75.8% for natural bentonite to reach 99.6% for acid treated bentonite. The rate of MB removal followed the pseudo second order model with a high correlation factor. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms. The Langmuir isotherm model was found more representative. The results indicate that bentonite could be employed as a low cost adsorbent in wastewater treatment for the removal of colour and dyes.

  9. Tracer diffusion in compacted, water-saturated bentonite

    International Nuclear Information System (INIS)

    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

  10. Utilization of locally available bentonites for water purification by activation

    International Nuclear Information System (INIS)

    Acid activation of commercial bentonite was conducted and tested for adsorption of impurities in water and industrial products. The properties of adsorption/absorption of bentonite are also used to remove impurities for the processing of edible oils and fats, as well as for the purification of products like honey and alcohol. The design of various experiments in order to assess and simulate the effects of acid activation of commercial bentonite on the adsorption capacity of methylene blue dye is described in this paper. The key parameters of the acid activation, namely acid concentration, contact time, temperature and type of acid, were established. The results indicated effects of these variables on the effectiveness of adsorption. The Swelling Index value of activated bentonite was 20 ml per 2 gram in deionized water as compared to 8 ml per 2 gm in unactivated samples. The acid concentration exerts a predominant individual effect as compared to other parameters. Bentonite activated by 5N HCl has more adsorption capacity than 40% HSO. Excessive 2 4 activation is discussed in terms of loss in both porosity and acid strength. (author)

  11. 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

  12. DECOVALEX II PROJECT Technical Report - Task 2C

    International Nuclear Information System (INIS)

    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

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

    International Nuclear Information System (INIS)

    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

  14. 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

  15. Decantation time of evaluation on bentonite clays fractionation

    International Nuclear Information System (INIS)

    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)

  16. Comparison of two approaches to forced convection in crystal growth of II-VI compounds by THM

    OpenAIRE

    Bloedner, R. U.; Presia, M.; Gille, Peter

    1994-01-01

    Hg1 - xCdxTe and Cd1 - xZnxTe single crystals were grown by the tracwelling heater method (THM), applying two different techniques of artificially stirring the solution zone. Accelerated crucible rotation (ACRT) was used in a vertical growth arrangement and compared a technique with constant rotation around the horizontal axis of the ampoule. The dominant hydrodynamic mechanisms of noth methods are discribed by the rotating disc model and are suggested to be almost identical with respect to t...

  17. Structure and forces in bentonite MX-80

    International Nuclear Information System (INIS)

    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 explain the

  18. 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.

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

    International Nuclear Information System (INIS)

    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.)

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

    International Nuclear Information System (INIS)

    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 CO2), 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

  1. Study on long-term performance of bentonite layer in radioactive waste repository

    International Nuclear Information System (INIS)

    It is important to appropriately evaluate the long-term performance of the bentonite layer in a radioactive waste repository because it can considerably affect the repository function for containment and delay of nuclides. Thus far, limited knowledge has been available on alkali alteration phenomena of highly compacted bentonite and their effect on its physical properties. In this study, we developed an apparatus for testing alkali alteration phenomena of highly compacted bentonite and its physical properties. Through studies conducted using the apparatus, we concluded that the alkali dissolution rate of montmorillonite in highly compacted bentonite is less than 9.7 x 10-13 mol/m2/sec and that the hydraulic conductivity of the bentonite layer is affected by the pore structure, which can be refined by the effect of dissolution and precipitation of minerals in bentonite, as well as by the density of the bentonite layer and the electrolyte concentration of pore solution. (author)

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

    International Nuclear Information System (INIS)

    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

  3. 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

    =17 min; t½,4=18 min). For drinking water, ozone decomposition was fast for the first dose of ozone (t½,1=4 min) and then decreased for the second and third dose of ozone (t½,2=19 min; t½,3=17 min). Chlorination after ozonation revealed that ozone removed reactivity of the dissolved organic carbon toward......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...... 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...

  4. Application of Rotating Magnetic Fields to THM Growth Process: Te-CdTe

    Science.gov (United States)

    LeClair, Mark; Worlikar, Ani; Motakef, Shariar; Gillies, Donald C.

    1998-01-01

    The numerical simulation of ongoing traveling heater method (THM) solution growth experiments of CdTe from Te solvent and the influence of a Rotating Magnetic Field (RMF) on control of convection in the solution zone is presented. The application of RMF is pursued as a means to actively control thermo-solutal convection in the solution zone which otherwise would be dominated by buoyancy forces. Numerical simulation and scaling analysis are used to generate a flow-regime map demarcating the boundary separating the buoyancy- and RMF-driven convection in the solution zone. Results indicate that whereas at low gravity levels the application of RMF can completely overwhelm buoyancy-induced convection, at normal gravity levels the successful control of convection by RMF requires use of fairly thin solvent zones. Simulation results also indicate that field strengths required to dominate natural convection on earth may lead to instabilities and transition to turbulence, and an associated deleterious effect on the quality of grown crystals. These and other simulations results are discussed in reference to experimental evidence.

  5. 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

  6. Magnesium incorporated bentonite clay for defluoridation of drinking water

    International Nuclear Information System (INIS)

    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.

  7. A review of porosity and diffusion in bentonite

    International Nuclear Information System (INIS)

    Porosity in bentonite can be subdivided in free porewater, diffuse double layer (DDL) water, and interlayer water in montmorillonite, the most important mineral of bentonite. The proportions of these water types can be calculated from the internal and external specific surface area of montmorillonite and the width of interlayer- and DDL-water. Stacking of the TOT layers in montmorillonite in the c-direction is the master variable that determines the specific internal and external surface areas. The thickness of the water layers depends on the ionic strength and the composition of the free porewater, and on the packing density of the bentonite. When the proportions of the water types change, the diffusion of cations, anions and neutral molecules is affected in different ways since the diffusional properties vary. Diffusive fluxes are proportional with accessible porosity, chemical potential gradient, and diffusion coefficient, but not with concentration as has been proposed often in diffusion models. The equations for calculating the diffusive flux through interlayer water are derived. The potential gradient here is given by the gradient of the equivalent (or molar) fraction of the cation in the cation exchange capacity. The latter is expressed as concentration in the interlayer water. An example calculation illustrates that the flux in interlayer water can be dominant and opposite to the one in free porewater. Retardation by ion exchange is an important process in bentonite that can be modeled if the concentrations of major ions are known. Unfortunately, the analyses are almost never done in diffusion experiments.(orig.)

  8. Sodium Bentonite-Based Fire Retardant Coatings Containing Starch

    Science.gov (United States)

    Sodium bentonite (SB) gel and foam coatings were tested for their ability to suppress the rate of heat increase at the surface of commercial lap siding. Starch was added to some treatments to determine whether it stabilized the coating and prevented vertical slumping. A commercial fire protection ge...

  9. Experimental study on bentonite gel migration from a deposition hole

    International Nuclear Information System (INIS)

    The experimental study on bentonite gel migration from a deposition hole into a surrounding joint has been performed by using a transparent acrylic resin cell with a slot. Cylindrical blocks of pure bentonite and a bentonite-sand mixture have been used as the buffer material, and the slot width simulating the joint aperture is set between 0.3 to 1.5 mm. The time-dependence displacement of migrating gel fronts in the slots and the swelling pressure of the sample in the core, which simulate a deposition hole, have been measured. It has been observed that the migrating gel front separates two distinct zones, and the displacement of the front is proportional to the square-root of time before the separation. With wider slots, the swelling pressure of the sample in the core has rapidly decreased. Applying theoretical models to the experimental results, the viscosity of the migrating gel in the slot (ca. 200 MPa·s) and the diffusion coefficient of bentonite clay (ca. 3 x 10-11m2/s) have been obtained. (author)

  10. Diffusion of anions and cations in compacted sodium bentonite

    International Nuclear Information System (INIS)

    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 Sr2+ 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 Sr2+ 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.)

  11. 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.

  12. Polypropylene–clay composite prepared from Indian bentonite

    Indian Academy of Sciences (India)

    Madhuchhanda Sarkar; Kausik Dana; Sankar Ghatak; Amarnath Banerjee

    2008-02-01

    In the present work, a set of experimental polypropylene (PP) clay composites containing pristine bentonite clay of Indian origin has been prepared and then characterized. The polymer clay composites are processed by solution mixing of polypropylene with bentonite clay using a solvent xylene and high speed electric stirrer at a temperature around 130°C and then by compression molding at 170°C. The mechanical properties of PP–clay composites like tensile strength, hardness and impact resistance have been investigated. Microstructural studies were carried out using scanning electron microscope and transmission electron microscope and the thermal properties were studied using differential scanning calorimeter. Mechanical properties of the prepared composites showed highest reinforcing and toughening effects of the clay filler at a loading of only 5 mass % in PP matrix. Tensile strength was observed to be highest in case of 5 mass % of clay loading and it was more than 14% of that of the neat PP, while toughness increased by more than 80%. Bentonite clay–PP composite (5 mass %) also showed 60% increase in impact energy value. However, no significant change was observed in case of hardness and tensile modulus. Higher percentages of bentonite clay did not further improve the properties with respect to pristine polypropylene. The study of the microstructure of the prepared polymer layered silicate clay composites showed a mixed morphology with multiple stacks of clay layers and tactoids of different thicknesses.

  13. Preliminary assessment of DOC and THM precursor loads from a freshwater restored wetland, an agricultural field, and a tidal wetland in the Sacramento-San Joaquin River Delta

    Science.gov (United States)

    Fujii, R.; Bergamaschi, B.A.; Ganju, N.K.; Fleck, J.A.; Burow-Fogg, K.R.; Schoellhamer, D.; Deverel, S.J.

    2003-01-01

    Water exported from the Sacramento-San Joaquin River Delta supplies drinking water to more than 22 million people in California. At certain times of the year, Delta waters contain relatively high concentrations of dissolved organic carbon (DOC) and bromide. During these times, chlorination of Delta water for drinking water disinfection will form disinfection byproducts, such as trihalomethanes (THMs), that can exceed the U.S. Environmental Protection Agency's maximum contaminant level for THMs of 80 mg/L. Important sources of DOC and THM precursors (types of DOC that form THMs when chlorinated) to the Delta include rivers, drainage water from peat islands, water from wetlands and areas with extensive riparian vegetation, and in-channel growth of algae and macrophytes. Due to proposed ecosystem restoration and creation of wetlands in the Delta, there is an urgent need for information on the relative loads of DOC and THM precursors produced from three different land uses: restored wetlands constructed for subsidence mitigation, tidal wetlands, and agricultural operations. We have been conducting research in the Delta to provide this information. A restored wetland and agricultural field located on Twitchell Island, and a tidal wetland on Browns Island have been monitored for flow, DOC, and THM precursors. Initial results indicate that the loads of DOC and THM precursors are similar for the restored wetland (surface water only) and the agricultural field. These land uses produce DOC loads of about 14 and 11 g C/m2/yr, respectively, and THM precursor loads of about 1.7 and 1.0 g THM/m2/yr, respectively. Estimates of DOC and THM precursor loads for the tidal wetland site on Browns Island and seepage associated with the restored wetland are being developed.

  14. Activation of a Ca-bentonite as buffer material

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. 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

  15. 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

  16. Effects of the injection grout Silica sol on bentonite

    International Nuclear Information System (INIS)

    Silica sol, i.e., colloidal SiO2, may be used as a low-pH injection grout for very fine fractures in the construction of deep geological repositories for radioactive waste in Sweden and in Finland. If the bentonite barrier encounters SiO2-colloid particles under conditions favorable for aggregation, there is concern that it will modify the bentonite barrier at the bentonite/bedrock interface. In this study qualitative experiments were performed with mixed dispersions of SiO2-colloids and bentonite or homo-ionic Na/Ca-montmorillonite. Samples were prepared at different colloid concentrations and treated under various conditions such as low and high ionic strength (0.3 M NaCl), as well as dehydration and re-dispersing. Free swelling and settling experiments were performed in order to qualitatively compare the conditions in which SiO2-colloids affect the bulk/macro properties of bentonite. In order to study specific SiO2-colloid/montmorillonite interactions and preferred type of initial aggregation, dilute dispersions of homo-ionic montmorillonite dispersions mixed with varying concentrations of SiO2-colloids were prepared and selected samples were characterized by PCS, SEM/EDS, AFM and PXRD. The results from this study show that bentonite and montmorillonite particles can be modified by SiO2-colloids when mixed in comparable amounts, due to dehydration or high ionic strength. Some indications for increased colloidal stability for the SiO2-colloid modified clay particles were also found. From the AFM investigation it was found that initial attachment of the SiO2-colloids in Na+ dominated samples seemed to occur on the edges of the montmorillonite layers. In Ca2+ dominated samples not subjected to excess NaCl, SiO2-colloid sorption onto the faces of the montmorillonite layers was also found. In all, contact between the bentonite barrier and un-gelled Silica sol should preferably be avoided. (authors)

  17. 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

  18. Study of cesium and strontium adsorption on slovak bentonite

    International Nuclear Information System (INIS)

    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 Kd 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)

  19. Evaluation of the outflow characteristic of bentonite buffer material. 2

    International Nuclear Information System (INIS)

    The outflow behaviour of bentonite buffer material was experiment to assess the physical stability in the geological disposal system, the parameters of experiment are the dry density of bentonite, mixtures ratio silica sand, fracture width, and flow velocity. The outflow phenomena were identified as extrusion and erosion, and the experimental results are as follows; 1) Extrusion: The proportional coefficient obtained from the relation between time and extrusion distance was arranged by the relation with effective clay density. The experimental equation of the proportional coefficient is as follows; A = 6.7587x10-7∼ exp(5.7261d)∼ exp((6.1598+(-0.5398d)+(-0.9272d2))∼ Pb). By model experiment, the density distribution into fracture was measured. The density distribution of an extrusion region obtained 0.8-0.2 Mgm-3. The average dry density into fracture of bentonite gel was about 0.4 Mgm-3 below. The influence of density of bentonite/sand mixtures material (30 wt%, 1.6 Mgm-3) by the extrusion phenomenon was calculated. It was assumed that the average fracture density is about eight fractures parameter. The reduction in density of the bentonite/sand mixtures material is about 4.5% (1.527 Mgm-3) of the initial value after 10,000 years. 2) Erosion: The colloid concentration and the particle size in drainage liquid were measured as parameter of flow velocity into fracture. The result of measurement, colloid concentration decreased with the increase in the flow velocity. Moreover, the particle size of colloid became large. In the case of average flow velocity 1E-5 ms-1, the colloid was generated in drainage liquid. Therefore, the flow velocity for occurrence of erosion was suggested smaller than 1E-5 ms-1. (author)

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

    International Nuclear Information System (INIS)

    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

  1. Experimental Investigation of Near-Borehole Crack Plugging with Bentonite

    Science.gov (United States)

    Upadhyay, R. A.; Islam, M. N.; Bunger, A.

    2015-12-01

    The success of the disposal of nuclear waste in a deep borehole (DBH) is determined by the integrity of the components of the borehole plug. Bentonite clay has been proposed as a key plugging material, and its effectiveness depends upon its penetration into near-borehole cracks associated with the drilling process. Here we present research aimed at understanding and maximizing the ability of clay materials to plug near-borehole cracks. A device was constructed such that the borehole is represented by a cylindrical chamber, and a near-borehole crack is represented by a slot adjacent to the center chamber. The experiments consist of placing bentonite clay pellets into the center chamber and filling the entire cavity with distilled water so that the pellets hydrate and swell, intruding into the slot because the cell prohibits swelling in the vertical direction along the borehole. Results indicate that the bentonite clay pellets do not fully plug the slot. We propose a model where the penetration is limited by (1) the free swelling potential intrinsic to the system comprised of the bentonite pellets and the hydrating fluid and (2) resisting shear force along the walls of the slot. Narrow slots have a smaller volume for the clay to fill than wider slots, but wider slots present less resistive force to clay intrusion. These two limiting factors work against each other, leading to a non-monotonic relationship between slot width and intrusion length. Further experimental results indicate that the free swelling potential of bentonite clay pellets depends on pellet diameter, "container" geometry, and solution salinity. Smaller diameter pellets possess more relative volumetric expansion than larger diameter pellets. The relative expansion of the clay also appears to decrease with the container size, which we understand to be due to the increased resistive force provided by the container walls. Increasing the salinity of the solution leads to a dramatic decrease in the clay

  2. Transport of Iodide Ion in Compacted Bentonite Containing Ag2O - 12111

    International Nuclear Information System (INIS)

    Observations of the transport of iodide through compacted bentonite containing Ag2O as additive and that without additive were made. Compacted bentonite samples with densities of 1.41 g/cm3 and 1.60 g/cm3 were used in the experiment. The amount of Ag2O added to the compacted bentonite was in the range of 0.0064 ∼ 0.0468 wt/wt%. Two diffusion solutions were used: one in which iodide ion was dissolved in demineralized water (pure iodide solution), and one in which iodide ion was dissolved in 0.1 M NaCl solution (0.1 M NaCl-iodide solution). Experimental results confirmed that iodide ion was transported by the diffusion process in the compacted bentonite containing Ag2O as well as in the compacted bentonite without Ag2O. The time-lag of diffusion of iodide ion in the compacted bentonite containing Ag2O is larger than that in the compacted bentonite without Ag2O. The increase of the time-lag of diffusion was observed in pure iodide ion solution as well as in 0.1 M NaCl-iodide solution. The apparent diffusion coefficient of iodide ion in the compacted bentonite containing Ag2O was smaller than in the compacted bentonite without Ag2O. The effective diffusion coefficient decreased as the amount of Ag2O in the compacted bentonite increased. (authors)

  3. An Investigation of Diffusion of Iodide Ion in Compacted Bentonite Containing Ag2O

    International Nuclear Information System (INIS)

    In the compacted bentonite containing Ag2O, the transport of iodide ion was investigated by Through-diffusion method. It is confirmed that Iodide ion is transported by diffusion process in the compacted bentonite containing Ag2O as well as in the compacted bentonite without Ag2O. However, the lag-time of iodide ion in the compacted bentonite containing Ag2O is larger than that in the compacted bentonite without Ag2O. The increase of the lag-time was observed in pure iodide ion solution and also in 0.1M NaCl-iodide ion solution. The apparent diffusion coefficient of iodide ion in the compacted bentonite containing Ag2O has lower value than that in the compacted bentonite without Ag2O. The effect of Ag2O on the effective diffusion coefficient was not clearly investigated in the compacted bentonite containing Ag2O while the values of effective diffusion coefficient of iodide ion in the compacted bentonite without Ag2O obtained in this study were similar to those in the compacted bentonite reported in the literature

  4. Coupled thermo-hydro-chemical models of swelling bentonites

    Science.gov (United States)

    Samper, Javier; Mon, Alba; Zheng, Liange; Montenegro, Luis; Naves, Acacia; Pisani, Bruno

    2014-05-01

    The disposal of radioactive waste in deep geological repositories is based on the multibarrier concept of retention of the waste by a combination of engineered and geological barriers. The engineered barrier system (EBS) includes the solid conditioned waste-form, the waste container, the buffer made of materials such as clay, grout or crushed rock that separate the waste package from the host rock and the tunnel linings and supports. The geological barrier supports the engineered system and provides stability over the long term during which time radioactive decay reduces the levels of radioactivity. The strong interplays among thermal (T), hydrodynamic (H), mechanical (M) and chemical (C) processes during the hydration, thermal and solute transport stages of the engineered barrier system (EBS) of a radioactive waste repository call for coupled THMC models for the metallic overpack, the unsaturated compacted bentonite and the concrete liner. Conceptual and numerical coupled THMC models of the EBS have been developed, which have been implemented in INVERSE-FADES-CORE. Chemical reactions are coupled to the hydrodynamic processes through chemical osmosis (C-H coupling) while bentonite swelling affects solute transport via changes in bentonite porosity changes (M-H coupling). Here we present THMC models of heating and hydration laboratory experiments performed by CIEMAT (Madrid, Spain) on compacted FEBEX bentonite and numerical models for the long-term evolution of the EBS for 1 Ma. The changes in porosity caused by swelling are more important than those produced by the chemical reactions during the early evolution of the EBS (t < 100 years). For longer times, however, the changes in porosity induced by the dissolution/precipitation reactions are more relevant due to: 1) The effect of iron mineral phases (corrosion products) released by the corrosion of the carbon steel canister; and 2) The hyper alkaline plume produced by the concrete liner. Numerical results show that

  5. Experimental indications of effects of surface deprotonation on Na-bentonite pore water chemistry in a geological repository

    International Nuclear Information System (INIS)

    Bentonite-water interaction was studied using a simple equilibrium model based on experimental measurements in order to describe bentonite porewater chemistry. Direct pH measurements for highly compacted bentonite and batch-type bentonite-water interaction experiments were performed under anaerobic conditions. In the direct pH measurements, resin particles doped with a pH indicator were sandwiched between a pair of bentonite columns immersed in a test solution. The experimental results showed that the solution compositions in equilibrium with bentonite depended on the bentonite to liquid ratio (B/L) and the initial solution composition. An equilibrium model assuming only fast equilibration processes between the bentonite minerals and the solution could be used to calculate the trends of pH and other ion concentrations with B/L. This study indicates that the surface deprotonation of smectite is a very important factor influencing the porewater chemistry in highly compacted bentonite. Copyright (2001) Material Research Society

  6. Temperature effect on the behaviour of engineered clay barriers

    International Nuclear Information System (INIS)

    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)

  7. 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)

  8. 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.

  9. General purpose steam table library : CASL L3:THM.CFD.P7.04 milestone report.

    Energy Technology Data Exchange (ETDEWEB)

    Carpenter, John H.; Belcourt, Noel; Nourgaliev, Robert

    2013-08-01

    Completion of the CASL L3 milestone THM.CFD.P7.04 provides a general purpose tabular interpolation library for material properties to support, in particular, standardized models for steam properties. The software consists of three parts, implementations of analytic steam models, a code to generate tables from those models, and an interpolation package to interface the tables to CFD codes such as Hydra-TH. Verification of the standard model is maintained through the entire train of routines. The performance of interpolation package exceeds that of freely available analytic implementation of the steam properties by over an order of magnitude.

  10. Resonance Strength Measurement at Astrophysical Energies: The 17O(p,α)14N Reaction Studied via THM

    Science.gov (United States)

    Sergi, M. L.; Spitaleri, C.; La Cognata, M.; Lamia, L.; Pizzone, R. G.; Rapisarda, G. G.; Mukhamedzhanov, A.; Irgaziev, B.; Tang, X. D.; Wischer, M.; Mrazek, J.; Kroha, V.

    2016-05-01

    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,α)14N 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.

  11. Resonance Strength Measurement at Astrophysical Energies: The 17O(p,α)14N Reaction Studied via THM

    OpenAIRE

    Sergi M.L.; Spitaleri C.; La Cognata M.; Lamia L.; Pizzone R.G.; Rapisarda G.G.; Mukhamedzhanov A.; Irgaziev B.; Tang X.D.; Wischer M.; Mrazek J.; Kroha V.

    2016-01-01

    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,α)14N 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 ...

  12. Tabular water properties interface for Hydra-TH : CASL THM.CFD.P6.03 milestone report.

    Energy Technology Data Exchange (ETDEWEB)

    Carpenter, John H.; Belcourt, Noel

    2013-04-01

    Completion of the CASL L3 milestone THM.CFD.P6.03 provides a tabular material properties capability to the Hydra code. A tabular interpolation package used in Sandia codes was modified to support the needs of multi-phase solvers in Hydra. Use of the interface is described. The package was released to Hydra under a government use license. A dummy physics was created in Hydra to prototype use of the interpolation routines. Finally, a test using the dummy physics verifies the correct behavior of the interpolation for a test water table. 3

  13. EBS behaviour immediately after repository closure in a clay host rock: the HE-E experiment (Mont Terri URL) - 59288

    International Nuclear Information System (INIS)

    The evolution of the engineered barrier system (EBS) of geological repositories for radioactive waste has been the subject of many research programmes during the last decade. The emphasis of the research activities was on the elaboration of a detailed understanding of the complex thermo-hydro-mechanical- chemical processes, which are expected to evolve in the early post closure period in the near field. It is important to understand the coupled THM-C processes and their evolution occurring in the EBS during the early post-closure phase so it can be confirmed that the safety functions will be fulfilled. Especially, it needs to be ensured that interactions during the re-saturation phase (heat pulse, gas generation, non-uniform water uptake from the host rock) do not affect the performance of the EBS in terms of its safety-relevant parameters (e.g. swelling pressure, hydraulic conductivity, diffusivity). The 7. Framework PEBS project (Long Term Performance of Engineered Barrier Systems) aims at providing in depth process understanding for constraining the conceptual and parametric uncertainties in the context of long-term safety assessment. As part of the PEBS project a series of laboratory and URL experiments are envisaged to describe the EBS behaviour after repository closure when re-saturation is taking place. In this paper the very early post-closure period is targeted when the EBS is subjected to high temperatures and unsaturated conditions with a low but increasing moisture content. So far the detailed thermo-hydraulic behaviour of a bentonite EBS in a clay host rock has not been evaluated at a large scale in response to temperatures of up to 140 deg. C at the canister surface, produced by HLW (and spent fuel), as anticipated in some of the designs considered. Furthermore, earlier THM experiments have shown that up-scaling of thermal conductivity and its dependency on water content and/or humidity from the laboratory scale to a field scale needs further

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

    International Nuclear Information System (INIS)

    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)

  15. Synthesis, characterization and antimicrobial activity of alkaline ion-exchanged ZnO/bentonite nanocomposites

    Institute of Scientific and Technical Information of China (English)

    Hamideh Pouraboulghasem; Mohammad Ghorbanpour; Razieh Shayegh; Samaneh Lotfiman

    2016-01-01

    Nanocomposites of zinc/bentonite clay were synthesized for use as an antibacterial material by a quick and simple alkaline ion exchange method. The synthesis of zinc doped bentonite nanocomposite was accomplished by placing bentonite in a melting bath of ZnSO4 for 10, 20, 40, 60 and 90 min. The complexes were characterized by XRD, SEM and DRS. XRD analyses and SEM observations confirmed the diffusion of zinc to the clay surfaces. Antibacterial activity tests againstEscherichia coli showed that bentonite did not present any antibacterial properties, but after alkaline ion exchange treatment, inhibition was noted. The highest antibacterial activity was observed with ZnO/bentonite composite alkaline ion exchange for 60 and 90 min. Interestingly, the leaching test indicated that ZnO/bentonite did not present any risk for drinking water treatment.

  16. Characteristics of thermally-enhanced bentonite grouts for geothermal heat exchanger in South Korea

    Institute of Scientific and Technical Information of China (English)

    Chulho; LEE; Kangja; LEE; Hangseok; CHOI; Hyo-Pum; CHOI

    2010-01-01

    The thermal conductivity and viscosity of bentonite grouts have been evaluated and compared each other to determine the suitability of these materials for backfilling vertical boreholes of ground heat exchangers.Seven bentonite grouts from different product sources were considered in this paper.Two additives,silica sand and graphite were added in bentonite grouts to enhance thermal performance.The bentonite grouts indicate that both the thermal conductivity and the viscosity increase with the content of silica sand and graphite.Therefore,it is recommended to select cautiously the amount of silica sand and graphite considering not only thermal conductivity but also viscosity for the optimum condition of backfilling.Finally,the effect of salinity in the pore water on the change of swelling potential of the bentonite-based grouts has been quantitatively evaluated to show the feasibility of bentonite grouts in the coastal area.

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

    International Nuclear Information System (INIS)

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

    International Nuclear Information System (INIS)

    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

  19. Sorption of Lithium on Bentonite, Kaolin and Zeolite

    OpenAIRE

    Mandy Hoyer; Nicolai-Alexeji Kummer; Broder Merkel

    2015-01-01

    Li sorption was studied on natural bentonite, kaolin and zeolite in batch experiments at variable Li and Na concentrations (0, 1.5, 15, 150, 750 mM LiCl and 0.01, 0.1, 1, 3, 5 M NaCl). The solid-to-solution ratio was 1:4 and pH ranged from 2 to 10. Maximum Li sorption was determined at 0.01 M NaCl and 750 mM LiCl concentration in solution. It was 3800 ± 380 ppm, 1300 ± 130 ppm and 3900 ± 390 ppm on bentonite, kaolin and zeolite, respectively, which is in the average to upper range typical fo...

  20. 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 .

  1. Thermal stability of the thermoluminescence trap structure of bentonite

    International Nuclear Information System (INIS)

    This work reports about the thermal stability of the blue thermoluminescence (TL) of a well-characterised natural bentonite from Almeria (Spain). The main interest of this clay, mainly composed of montmorillonite, is because of its application in the field of high-level radioactive waste (HLW) repository in deep-lying rocks. As observed in other aluminosilicates, bentonite exhibits a very complex structure of the emission spectra based on a wide broad maximum peaked at ∼265 deg. C that can be associated to physico-chemical processes such as dehydroxylation processes, consecutive breaking linking of bonds, formation of hydrolysed ions and redox reactions. The thermal stability tests performed at different temperatures confirm a continuum in the distribution of traps. Hence, the glow curve analysis methods commonly used for synthetic materials based on single discrete traps cannot be applied for this material and the kinetic parameters were fitted assuming an exponential distribution of trapped electrons. (authors)

  2. Formation, modeling and validation of trihalomethanes (THM) in Malaysian drinking water: a case study in the districts of Tampin, Negeri Sembilan and Sabak Bernam, Selangor, Malaysia.

    Science.gov (United States)

    Abdullah, Md Pauzi; Yew, C H; Ramli, Mohamad Salleh bin

    2003-11-01

    A modeling procedure that predicts trihalomethane (THM) formation from field sampling at the treatment plant and along its distribution system using Tampin district, Negeri Sembilan and Sabak Bernam district, Selangor as sources of data were studied and developed. Using Pearson method of correlation, the organic matter measured as TOC showed a positive correlation with formation of THM (r=0.380,P=0.0001 for Tampin and r=0.478,P=0.0001 for Sabak Bernam). Similar positive correlation was also obtained for pH in both districts with Tampin (r=0.362,P=0.0010) and Sabak Bernam (r=0.215,P=0.0010). Chlorine dosage was also found to have low correlation with formation of THM for the two districts with Tampin (r=0.233,P=0.0230) and Sabak Bernam (r=0.505,P=0.0001). Distance from treatment plant was found to have correlation with formation of THM for Tampin district with r=0.353 and P=0.0010. Other parameters such as turbidity, ammonia, temperature and residue chlorine were found to have no correlation with formation of THM. Linear and non-linear models were developed for these two districts. The results obtained were validated using three different sets of field data obtained from own source and district of Seremban (Pantai and Sg. Terip), Negeri Sembilan. Validation results indicated that there was significant difference in the predictive and determined values of THM when two sets of data from districts of Seremban were used with an exception of field data of Sg. Terip for non-linear model developed for district of Tampin. It was found that a non-linear model is slightly better than linear model in terms of percentage prediction errors. The models developed were site specific and the predictive capabilities in the distribution systems vary with different environmental conditions. PMID:14568050

  3. Preparation and performance of Ecobras/bentonite biodegrading films

    International Nuclear Information System (INIS)

    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)

  4. Sorption of cesium on bentonite: The role of calcite

    International Nuclear Information System (INIS)

    Full text: Since bentonite is investigated for its use in Engineered Barriers Systems as backfill material, many studies of their surfaces properties have been performed in the past years to qualify and quantify adsorption on their surfaces, which can be one of the major processes limiting migration of radionuclides away from a disposal site. Nevertheless, most of these studies concerned simplified systems, such as Na-montmorillonite in mono-electrolyte solution. As ion-exchange processes are of importance in water-clays interactions, adsorption of natural major ions has also to be taken into account for natural systems. The aim of this work is (i) to quantify the sorption of the natural major cations on the montmorillonite surface; (ii) to compare the sorption of cesium, in two different systems, a simple one ( Na-montmorillonite in NaNO3 0.05 Mol.L-1) and a complex one (natural bentonite in a synthetic natural water) and then; (iii) to assess the influence of the natural major ions on this sorption, and to identify the role of the calcite phase present in bentonite. The methodology used consists in several batch experiments, first considering a very simple solution (NaNO3), then using mixtures of two different electrolytes, and lastly using a synthetic natural water. A surface complexation model, describing the surface of clays as a mixture of ion-exchange and complexation surface sites, is used to provide interpretations and quantifications of the sorption processes. Observed results indicate that affinity for the montmorillonite surface is greatest for Ca, then Mg and then K. The sorption of cesium is strongly affected by the presence in solution of Ca, witch can come from the partial dissolution of calcite. This study is one part of a work supported by ANDRA on the retention properties of bentonite materials. (author)

  5. Soil-Bentonite Cutoff Walls: Hydraulic Conductivity and Contaminant Transport

    OpenAIRE

    Britton, Jeremy Paul

    2001-01-01

    ABSTRACT Soil-bentonite cutoff walls are commonly used to contain contaminants in the subsurface. A key property in determining the effectiveness of a cutoff wall is its hydraulic conductivity. There are important difficulties and uncertainties regarding the accuracy of commonly used methods of measuring the hydraulic conductivity of cutoff walls. When predicting contaminant transport through cutoff walls, common practice is to use the average hydraulic conductivity of the wall. ...

  6. Post examination of copper ER sensors exposed to bentonite

    International Nuclear Information System (INIS)

    Highlights: • Copper sensors were used for monitoring corrosion in bentonite during 4.2-y exposure. • Corrosion rates were estimated by applying three different methods. • Average corrosion rates for copper in bentonite are several µm/year. - Abstract: Copper corrosion in saline solutions under oxic conditions is one of concerns for the early periods of disposal of spent nuclear fuel in deep geological repositories. The main aim of the study was to investigate the corrosion behaviour of copper during this oxic period. The corrosion rate of pure copper was measured by means of thin electrical resistance (ER) sensors that were placed in a test package containing an oxic bentonite/saline groundwater environment at room temperature for a period of four years. Additionally, the corrosion rate was monitored by electrochemical impedance spectroscopy (EIS) measurements that were performed on the same ER sensors. By the end of the exposure period the corrosion rate, as estimated by both methods, had dropped to approximately 1.0 μm/year. The corrosion rate was also estimated by the examination of metallographic cross sections. The post examination tests which were used to determine the type and extent of corrosion products included different spectroscopic techniques (XRD and Raman analysis). It was confirmed that the corrosion rate obtained by means of physical (ER) and electrochemical techniques (EIS) was consistent with that estimated from the metallographic cross section analysis. The corrosion products consisted of cuprous oxide and paratacamite, which was very abundant. From the types of attack it can be concluded that the investigated samples of copper in bentonite underwent uneven general corrosion

  7. Sorption of Lithium on Bentonite, Kaolin and Zeolite

    Directory of Open Access Journals (Sweden)

    Mandy Hoyer

    2015-04-01

    Full Text Available Li sorption was studied on natural bentonite, kaolin and zeolite in batch experiments at variable Li and Na concentrations (0, 1.5, 15, 150, 750 mM LiCl and 0.01, 0.1, 1, 3, 5 M NaCl. The solid-to-solution ratio was 1:4 and pH ranged from 2 to 10. Maximum Li sorption was determined at 0.01 M NaCl and 750 mM LiCl concentration in solution. It was 3800 ± 380 ppm, 1300 ± 130 ppm and 3900 ± 390 ppm on bentonite, kaolin and zeolite, respectively, which is in the average to upper range typical for clay minerals. Under these conditions, kaolin was saturated with Li, whereas Li in bentonite and zeolite occupied only about 55%–79% and 9%–26% of the typical cation exchange capacity (CEC of smectites and zeolites, respectively. This is explained by differences in the way Li is bound in the materials studied. Li sorption on bentonite was independent of pH due to strong pH buffering. Above pH 5, kaolin was transformed to gibbsite, which completely changed its Li sorption capabilities. Extremely low as well as extremely high pH destabilized the crystal lattice of zeolite. All in all it was shown that, under the studied conditions, Li sorption on the studied materials occurs in detectable quantities. So, clay minerals and zeolites can act as a sink for Li if Li concentrations in solution are sufficiently high.

  8. Bentonite-cement interaction. Preliminary results from model calculations

    International Nuclear Information System (INIS)

    The interaction between the bentonite buffer and alkaline plume from degrading cementitious material used in the construction and operation of the repository is envisaged to constitute a risk to the long-term chemical stability of bentonite. In this report, first model calculations to shed light on the possible extent of mineralogical alteration of bentonite due to the plume have been carried out. A common feature of the model outcome for every case is the clogging of the pore space at the interface between the buffer and the rock fracture carrying the plume. Depending on the pH considered in the calculations for the plume (12.17, 11.60 and 9.70), this clogging will occur after 10, 18 and 5,900 years after the onset on interaction, respectively. For each case, the heavily altered zone in bentonite is confined very close to the interface. There are uncertainties related to the present calculations, the greatest ones pertaining to the poor knowledge of mineral dissolution/precipitation kinetics and to constraining the set of secondary minerals possible to form. The effects of the latter were clearly illustrated in two model cases (pH 11.60 and 9.70), where initially supersaturated secondary mineral phases were omitted; the pore clogging did not take place at the fracture-buffer interface and the buffer was continuously exposed to the alkaline plume. According to the present model calculations, it seems that the evolution of the interfacial porosity in the model system with pH 12.17 is not very sensitive to the selection of the secondary minerals as the pore space was clogged regardless. (orig.)

  9. Post examination of copper ER sensors exposed to bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Kosec, Tadeja, E-mail: tadeja.kosec@zag.si [Slovenian National Building and Civil Engineering Institute, Dimičeva 12, SI-1000 Ljubljana (Slovenia); Kranjc, Andrej [Slovenian National Building and Civil Engineering Institute, Dimičeva 12, SI-1000 Ljubljana (Slovenia); Rosborg, Bo [Royal Institute of Technology, Div. Surface and Corrosion Science, Drottning Kristinas väg 51, SE-100 44 Stockholm (Sweden); Legat, Andraž [Slovenian National Building and Civil Engineering Institute, Dimičeva 12, SI-1000 Ljubljana (Slovenia)

    2015-04-15

    Highlights: • Copper sensors were used for monitoring corrosion in bentonite during 4.2-y exposure. • Corrosion rates were estimated by applying three different methods. • Average corrosion rates for copper in bentonite are several µm/year. - Abstract: Copper corrosion in saline solutions under oxic conditions is one of concerns for the early periods of disposal of spent nuclear fuel in deep geological repositories. The main aim of the study was to investigate the corrosion behaviour of copper during this oxic period. The corrosion rate of pure copper was measured by means of thin electrical resistance (ER) sensors that were placed in a test package containing an oxic bentonite/saline groundwater environment at room temperature for a period of four years. Additionally, the corrosion rate was monitored by electrochemical impedance spectroscopy (EIS) measurements that were performed on the same ER sensors. By the end of the exposure period the corrosion rate, as estimated by both methods, had dropped to approximately 1.0 μm/year. The corrosion rate was also estimated by the examination of metallographic cross sections. The post examination tests which were used to determine the type and extent of corrosion products included different spectroscopic techniques (XRD and Raman analysis). It was confirmed that the corrosion rate obtained by means of physical (ER) and electrochemical techniques (EIS) was consistent with that estimated from the metallographic cross section analysis. The corrosion products consisted of cuprous oxide and paratacamite, which was very abundant. From the types of attack it can be concluded that the investigated samples of copper in bentonite underwent uneven general corrosion.

  10. Diffusion and sorption properties of radionuclides in compacted bentonite

    International Nuclear Information System (INIS)

    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 10-10 m2/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 10-12 m2/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 10-8 m2/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

  11. Production of smectite organophylic clays from three commercial sodium bentonite

    International Nuclear Information System (INIS)

    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)

  12. The sorption of aniline on organically modified bentonites

    Czech Academy of Sciences Publication Activity Database

    Plevová, Eva; Vaculíková, Lenka; Vítámvásová, E.; Valovičová, Věra

    Ostrava: VŠB TUO, 2015. s. 47-47. ISBN 978-80-248-3745-1. [Nanomaterials and Nanotechnology Meeting, Nano Ostrava 2015 /4./. 18.05.2015-21.05.2015, Ostrava] R&D Projects: GA MŠk ED2.1.00/03.0082; GA MŠk(CZ) LO1406 Institutional support: RVO:68145535 Keywords : bentonites * alkylammonium cations * sorption * aniline Subject RIV: JI - Composite Materials

  13. 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.

  14. Comparative study of bentonite properties with respect to the application as geotechnical barrier in HLRW repositories

    International Nuclear Information System (INIS)

    In concepts for the storage of high level radioactive waste (HLRW) the application of bentonite as sealing material is envisaged. Relevant properties of bentonites are cation exchange capacity (retention of pollutants), swelling (sealing of cracks), and low hydraulic conductivity. These properties significantly vary with the type of counter ion which is dominant in the smectite (commonly montmorillonite) interlayers. However, the variability of bentonites - not depending on the type of counter ion - is frequently underestimated. Bentonites vary in the mineralogical and chemical composition, and the arrangement of all components (intergrowth and micro fabric). Additionally, the main component (smectite) varies with respect to the degree of structural order, particle size, crystallite size, chemical composition, morphology, and amount and location of negative charges. This variation, of course, strongly affects bentonite properties in almost all fields of industrial application. Measurable parameters only occasionally explain the different properties. The common approach, therefore, is to perform application tests. In this study an attempt is made to identify the variation of bentonite properties with respect to the application in HLRW repositories. The study is based on the comparative investigation of 30 different bentonites from important bentonite mining areas worldwide. The bentonites were characterized intensively by mineralogical, optical, and chemical methods: XRD, IR, SEM, CEC, XRF, granulometry, layer charge density. (authors)

  15. Characteristics study of bentonite as candidate of buffer materials for radioactive waste disposal system

    International Nuclear Information System (INIS)

    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. Compression characteristics and permeability of saturated Gaomiaozi ca-bentonite

    International Nuclear Information System (INIS)

    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/cm3 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)

  17. Segregation of bentonite components in order to achieve nano montmorillonite

    International Nuclear Information System (INIS)

    Nano technology makes the possibility to achieve specific properties for materials. In this process, by reducing the size of materials in the range of nano size, new noticeable behaviour for material can be observed. Such behaviour cannot be observed for larger particles from that material. Bentonite soils contain more than 76% montmorillonite and some other minerals. Pure montmorillonite with nano size has a vast industrial application in which its production is relatively costly and time consuming. This research is aimed to propose a method for segregation of bentonite components to reach nano montmorillonite. To achieve this objective, a mechanical method is proposed. Based on this method, a nano montmorillonite with micro and nano size is achieved. The segregation process is monitored with PSA, XRD, SSA and SEM experiments. The results of this research show that a nano montmorillonite with SSA of 522.58 m2/g and average diameter of 6.13 micron is attained. The achieved nano montmorillonite has larger purity in comparison to Cloisite Na+. In addition, it has lower average particle size than Cloisite Na+. Furthermore, according to the results of this research the extracted nano clay is free from carbonate and quartz particles. The SSA of this nano montmorillonite was 25% more than that of bentonite. The proposed method is relatively inexpensive. Moreover, since no chemical is used in its production process, it is a suitable sample for practical, research, and industrial projects.

  18. Ageing effects on swelling behaviour of compacted GMZ01 bentonite

    International Nuclear Information System (INIS)

    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 K0 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 K0 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

  19. Phenol determination on HDTMA-bentonite-based electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Mojovic, Z., E-mail: zoricam@nanosys.ihtm.bg.ac.rs [University of Belgrade, Institute of Chemistry, Technology and Metallurgy, Department of Catalysis and Chemical Engineering, Njegoseva 12, 11000 Belgrade (Serbia); Jovic-Jovicic, N.; Milutinovic-Nikolic, A.; Bankovic, P.; Rabi-Stankovic, A. Abu; Jovanovic, D. [University of Belgrade, Institute of Chemistry, Technology and Metallurgy, Department of Catalysis and Chemical Engineering, Njegoseva 12, 11000 Belgrade (Serbia)

    2011-10-30

    Highlights: {yields} HDTMA-modified bentonites were tested as electrode materials in the electro-oxidation of phenol. {yields} The influences of the surfactant loading and pH of the supporting electrolyte were investigated. {yields} Rapid deactivation of electrodes occurred in an acidic environment. {yields} Good stability of the investigated electrodes was obtained in alkaline medium. {yields} The sensitivity toward phenol and stability of the electrodes was markedly improved with increasing HDTMA loading. - Abstract: The partial and complete substitution of cations in the interlayer region of clay with different amounts of hexadecyl trimethylammonium bromide (HDTMABr) was performed. The aim was to synthesize organo-bentonites to be used as constituents of porous electrodes for the electrooxidation of phenol. Domestic clay from Bogovina was subjected to a common procedure of the production of organo-bentonites. It included the following steps: grinding, sieving, Na-exchange, cation exchange and drying. The samples were characterized by X-ray diffraction (XRD) analysis, while the textural properties were evaluated by nitrogen physisorption. The multisweep cyclic voltammetry was applied to analyze the behavior of the clay modified glassy carbon electrode. The influences of the surfactant loading and pH of the support electrolyte were investigated. Rapid deactivation of electrodes occurred in an acidic environment, while good stability of the investigated electrodes was obtained in alkaline medium.

  20. Study on model for bentonite buffer intrusion. 2

    International Nuclear Information System (INIS)

    Modelling study on the extrusion phenomenon of the bentonite in a geological repository for the high-level radioactive is performed to enhance the reliability of latest model studied on fiscal year 2003 (H14), on the matter of density distribution of extruded bentonite gel. In this study, the model is reconsidered and revised based on the result of comparison between experimental and calculated results. The numerical analyses for BENTFLOW type experiments and model experiments on extrusion in a pipe are performed using the revised model. The analyses for the BENTFLOW about distribution of extrusion density reproduce the experimental results tolerably. The agreement between the calculated and experimental results of the model experiments are not good. Our model is originated in solid diffusion model of swelling clay proposed by Nakano et al. To enhance the reliability of our model, the latest model is reviewed by experts. At last, the numerical analyses for H12 type repository are performed by revised model to evaluate the long-term reduction of bentonite density for the extrusion phenomenon. The analytical results are compared with the results described in H12 report. (author)

  1. Study on model for bentonite buffer intrusion phenomenon

    International Nuclear Information System (INIS)

    Modelling study on the extrusion phenomenon in a geological repository for the high-level radioactive is performed to enhance the reliability of existing model described in H12 report. Main conclusions of this study are as follows: (1) The methods and physical interpretation of bentonite gel viscosity measurements are clarified and input data of the viscosity for the solid diffusivity are obtained. (2) The input data of the swelling pressure and hydraulic conductivity of bentonite in the low- density region necessary for the solid diffusivity are determined. (3) The consolidation-type model proposed by Ahn et al. is surveyed and compared with that used in this study. The consolidation-type model is thought to be equivalent to the solid diffusion model used in this study. (4) The numerical analyses for BENTFLOW experiments and model experiments on extrusion in a pipe are performed. The analyses for the BENTFLOW reproduce the experimental results better than the past studies. The agreement between the calculated and experimental results of the model experiments is not good. Thus further study is required for the evaluation of density distribution in extruding bentonite gel. (author)

  2. The sealing performance of bentonite/crushed basalt borehole plugs

    International Nuclear Information System (INIS)

    Mixtures of crushed rock and bentonite are considered for backfilling and sealing high-level nuclear waste repositories. Many variables affect the hydraulic conductivity of such mixtures, including the size and shape of the rock particles, method of mixing and emplacement, water content and density of the clay, and the weight ratio of rock to clay. Mixtures of crushed basalt and bentonite have been tested in two types of permeameters, 20 cm diameter stainless steel permeameters and 10 cm diameter PVC permeameters. Plugs were installed as a single lift or in many lifts; the water content of the clay ranged from air-dry to as high as 200%. Preliminary results show that a mixture of 75% crushed basalt and 25% bentonite has a hydraulic conductivity between 1 x 10-9 cm/s and 2.5 x 10-8 cm/s. In some cases, preferential flow paths have developed (possibly as a result of the montmorillonite washing out of the crushed rock matrix), giving hydraulic conductivities as high as 1 x 10-4 cm/s. Other ratios of rock to clay have similar bimodal results. The probability of failure is decreased by including a higher percentage of clay in the plug, crushing the rock finer, and evenly mixing the crushed rock and clay. 136 refs., 50 figs., 7 tabs

  3. Transient nuclide release through the bentonite barrier -SKB 91

    International Nuclear Information System (INIS)

    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)

  4. Bentonite as a colloid source in groundwaters at Olkiluoto

    Energy Technology Data Exchange (ETDEWEB)

    Vuorinen, U. [VTT Processes, Espoo (Finland); Hirvonen, H.

    2005-02-15

    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 {mu}m filters before entering the glove-box, because only colloids smaller than 0.45 {mu}m 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 {mu}m, 300kD and 10kD). The ultrafiltrations produced the colloid-containing concentrate fractions and the soluble substances-containing filtrate fractions. In

  5. Preparation and thermal properties of chitosan/bentonite composite beads

    Directory of Open Access Journals (Sweden)

    Teofilović Vesna

    2014-01-01

    Full Text Available Due to their biodegradable and nontoxic nature, biopolymer composites are often used as remarkable adsorbents in treatment of wastewater. In this study chitosan/bentonite composite beads were obtained by addition of clay into the polymer using solution process. Before the composite preparation, bentonite was modified with surfactant cetyltrimethyl ammonium bromide (CTAB. The morphology of beads was examined by scanning electron microscopy (SEM. Thermal properties of the composite beads were studied by simultaneous thermogravimetry coupled with differential scanning calorimetry (SDT and differential scanning calorimetry (DSC. TG results showed that the complex decomposition mechanism of the composites depends on the preparation procedure. It was observed that the concentration of NaOH used for composites precipitation affects the final structure of beads. The influence of preparation procedure on the glass transition temperature Tg of chitosan/bentonite samples was not found (Tg values for all samples were about 144 °C. [Projekat Ministarstva nauke Republike Srbije, br. III45022 and ON172014 and Provincial Secretariat of Vojvodina for Science and Technological Development 114-451-2396/2011-01.

  6. Diffusion of radionuclides in concrete/bentonite systems

    International Nuclear Information System (INIS)

    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

  7. Modelling Ni diffusion in bentonite using different sorption models

    International Nuclear Information System (INIS)

    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

  8. Purification of Sardinella sp., Oil: Centrifugation and Bentonite Adsorbent

    Directory of Open Access Journals (Sweden)

    S.H. Suseno

    2014-01-01

    Full Text Available Centrifugation and purification using adsorbents is one example of a fish oil refining techniques applied to reduce impurities of fish oil. The study aimed to determine the sardine oil quality before treatment, to determine yield of fish oil after centrifugation treatment and to determine the influence of centrifugation speed and bentonite concentration on sardine oil quality. Factorial design with two factors was used in this study. Level of free fatty acid and peroxide value before purification was 35.53% and 170 mEq/kg. Yield of fish oil after centrifugation treatment has been ranged from 17.42±3.56 to 76.33±0.21%. The best treatment which could reduce the peroxide value and total oxidation was a treatment with centrifugation speed at 6500 rpm and bentonite concentration at 3%. Peroxide value and total oxidation of its treatment was 25.00±0.00 and 51.43±0.01 mEq/kg. The lowest value of p-anisidine was 1.29±0.05 mEq/kg and its value could be found in a treatment with centrifugation speed at 4500 rpm and bentonite concentration at 5%. The level of free fatty acid after purification process was ranged from 27.35 to 34.69%. Oil clarity tended to increase with the increase of centrifugation speed and adsorbent concentration.

  9. Hexacyanoferrates and bentonite as binders of radiocaesium for reindeer

    International Nuclear Information System (INIS)

    The effects of varying doses of caesium binders (Bentonite and several forms of iron-hexacyanoferrates) on radiocaesium accumulation in red blood cells and on radiocaesium transfer to urine and faeces were studied in feeding experiments with reindeer calves. The caesium binders were added to a ration of lichen (containing 9.5 kBq of 134Cs+137Cs originating from the Chernobyl accident) and fed together with a pelleted reindeer feed (RF-71) for 42 days. A 50% reduction in red blood cell radiocaesium concentration was obtained with a daily dose of 1 mg/kg body weigth of ammoniumironhexacyanoferrate (AFCF) and with 500 mg/kg of bentonite. Three mg/kg of AFCF or 2 g/kg of bentonite reduced both urinary excretion and RBC concentrations with more than 80%. It is concluded that iron-hexacyanoferrates, as a result of their high caesium binding capacity, are particularly useful as caesium binders for free ranging ruminants like the reindeer. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-08-02

    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.

  11. Integration of Hydra-TH in VERA (L2 Milestone THM.CFD.P5.01)

    Energy Technology Data Exchange (ETDEWEB)

    Christon, Mark A. [Los Alamos National Laboratory; Baksoi, Jozsef [Los Alamos National Laboratory; Barnett, Nathan [formerly in CCS-2; Francois, Marianne M. [Los Alamos National Laboratory; Lowrie, Robert B. [Los Alamos National Laboratory; Sankaran, Ramanan [Scientific Computing Group, Oak Ridge National Laboratory

    2012-06-21

    This report describes the work carried out for completion of the Thermal Hydraulics Methods (THM) Level 2 Milestone THM.CFD.P5.01 for the Consortium for Advanced Simulation of Light Water Reactors (CASL). This milestone focused primarily on the initial integration of Hydra-TH in VERA. The primary objective for this milestone was the integration of Hydra-TH as a standalone executable in VERA. A series of code extensions/modifications have been made to Hydra-TH to facilitate integration of Hydra-TH in VERA and to permit future tighter integration and physics coupling. A total of 61 serial and 64 parallel regression tests have been supplied with Hydra-TH. These tests are are being executed in the TriBITS environment. Once the VERA team enables the full suite of tests, the results can be posted to the VERA CDash site. Future work will consider the use of the LIME 2.0 interface for tighter integration in VERA with additional efforts focused on multiphysics coupling with radiation transport, fuel performance, and solid/structural mechanics.

  12. 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

  13. Comments regarding the bentonite barrier - SR 97 Post-closure safety

    International Nuclear Information System (INIS)

    This review only deals with the role of the bentonite for ensuring the integrity of the canister from the start and throughout the lifetime of the repository. It seems as the technical reports in question deliver convincing data and answers to most of the questions that can be raised concerning the bentonite and the interplay between the different processes at hand. However, there is one area where further analysis and discussions seem inevitable. This area is related to the thermo-hydrological behavior of the bentonite, especially during the first phase of the repository. This is discussed in some detail below. The bentonite is compacted to a high density before installation and has a degree of saturation of about 80 % when it is placed in the bedrock and around the canister. The bentonite is then expected to gradually increase its water content by uptake of water from the surrounding bedrock. Thereby, the bentonite will swell and completely fill the gap between the canister and the bentonite and between the bentonite and the bedrock as well as exert radial pressure on the canister itself. It is well known that the hydraulic conductivity and the heat conductivity of the bentonite to a large extent depend on the degree of saturation. In the reports it is obvious that the pore pressure in the surrounding bedrock is expected to be large, close to 500 kPa. This high pressure, together with the suction in the bentonite, is expected to result in a rather quick saturation of the bentonite around the canister. The same processes are expected to rather quickly saturate the backfill, consisting of a mixture of crushed bedrock and bentonite in the tunnels above the deposition holes. These processes have been analyzed by means of finite element analysis. The time required is comparatively short and the resulting temperatures in the bentonite close to the canister will be acceptable. Questions can, however, be raised regarding the boundary conditions assumed for the pressures

  14. Generation and stability of bentonite colloids at the bentonite/granite interface of a deep geological radioactive waste repository

    Science.gov (United States)

    Missana, Tiziana; Alonso, Úrsula; Turrero, Maria Jesús

    2003-03-01

    The possible mechanisms of colloid generation at the near field/far field interface of a radioactive repository have been investigated by means of novel column experiments simulating the granite/bentonite boundary, both in dynamic and in quasi-static water flow conditions. It has been shown that solid particles and colloids can be detached from the bulk and mobilised by the water flow. The higher the flow rate, the higher the concentration of particles found in the water, according to an erosion process. However, the gel formation and the intrinsic tactoid structure of the clay play an important role in the submicron particle generation even in the compacted clay and in a confined system. In fact, once a bentonite gel is formed, in the regions where the clay is contacted with water, clay colloids can be formed even in quasi-static flow conditions. The potential relevance of these colloids in radionuclide transport has been studied by evaluating their stability in different chemical environments. The coagulation kinetics of natural bentonite colloids was experimentally studied as a function of the ionic strength and pH, by means of time-resolved light scattering techniques. It has been shown that these colloids are very stable in low saline (˜1×10 -3 M) and alkaline (pH≥8) waters.

  15. Sorption and diffusion of FE(II) in bentonite

    International Nuclear Information System (INIS)

    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 (55Fe) 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. Qualitatively

  16. 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

  17. DECOVALEX Project: from 1992 to 2007

    Science.gov (United States)

    Tsang, Chin-Fu; Stephansson, Ove; Jing, Lanru; Kautsky, Fritz

    2009-05-01

    The DECOVALEX project is a unique international research collaboration, initiated in 1992, for advancing the understanding and mathematical modelling of coupled thermo-hydro-mechanical (THM) and thermo-hydro-mechanical-chemical (THMC) processes in geological systems—subjects of importance for performance assessment of radioactive waste repositories in geological formations. From 1992 up to 2007, the project has made important progress and played a key role in the development of numerical modelling of coupled processes in fractured rocks and buffer/backfill materials. The project has been conducted by research teams supported by a large number of radioactive-waste-management organizations and regulatory authorities, including those of Canada, China, Finland, France, Japan, Germany, Spain, Sweden, UK, and the USA. Through this project, in-depth knowledge has been gained of coupled THM and THMC processes associated with nuclear waste repositories, as well as numerical simulation models for their quantitative analysis. The knowledge accumulated from this project, in the form of a large number of research reports and international journal and conference papers in the open literature, has been applied effectively in the implementation and review of national radioactive-waste-management programmes in the participating countries. This paper presents an overview of the project.

  18. 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

  19. Corrosion of high-level radioactive waste iron-canisters in contact with bentonite

    International Nuclear Information System (INIS)

    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. Study of caesium sorption on Na and Ca-Mg bentonites using batch and diffusion experiments

    International Nuclear Information System (INIS)

    In most deep geological repository concepts sorption of radionuclides on bentonite represents a very important process in retarding radionuclide migration into geosphere. Despite a huge amount of studies concerning caesium sorption on bentonites, there are still some problems requiring deeper clarification. One of the most important issues is the difference between distribution coefficients (Kd) obtained using batch and diffusion experiments. The results of a comprehensive study of caesium sorption on Na bentonite (industrial sorbent Volclay KWK 20-80, Suedchemie, Germany) and Ca-Mg bentonite (raw bentonite, Rokle deposit, Czech Republic) using both of these methods suggest that the reasons of this difference can originate from different sources connected with conditions of experiments and the ways of their evaluation. The main uncertainties of caesium sorption on two different bentonites using the batch method were described and the influence on sorption has been demonstrated. Detailed mineralogical and chemical analysis of bentonite samples confirmed the differences in mineral composition and physical-chemical properties of selected bentonite types. These data are necessary for better understanding of their sorption behaviour and for sorption results evaluation. The results suggest that caesium-selective minerals present in bentonites as admixtures can govern the sorption behaviour of caesium on different bentonites at its trace concentrations. At higher concentrations, the ion exchange on non-selective sites dominates the sorption and can be well-described using sorption isotherms and ion-exchange models. It also follows from the performed experiments that the caesium sorption on studied bentonites cannot be described using the simple Kd method that is often used to evaluate distribution coefficients from diffusion experiments. The uncertainties of evaluation of sorption coefficients from diffusion experiments can also be connected with the way of diffusion

  1. Adsorption of Bezanyl Red and Nylomine Green from aqueous solutions by natural and acid-activated bentonite

    OpenAIRE

    BENGUELLA, B.; YACOUTA-NOUR, A.

    2009-01-01

    The adsorption of two acid dyes, namely, Red Bezanyl and Green Nylomine, onto natural bentonite and acid activated bentonite from aqueous solutions were studied in a batch system. The kinetic data show that at the equilibrium, the acid-activated bentonite fixes more Bezanyl Red and Nylomine Green than the natural bentonite. Adsorption equilibrium was reached within 2 h. The results also showed that the kinetics of adsorption is best descibed by a pseudo second-order expression than a first or...

  2. Silurian bentonites in Lithuania: correlations based on sanidine phenocryst composition and graptolite biozonation – interpretation of volcanic source regions

    OpenAIRE

    Tarmo Kiipli; Sigitas Radzevičius; Toivo Kallaste

    2014-01-01

    Integrated correlation of bentonites (altered volcanic ashes) and graptolite biozonation is presented. Detailed study of two Lithuanian drill core sections extended previous knowledge of the occurrence and composition of bentonites to the south. Identification of graptolite species allowed bentonites to be assigned their proper stratigraphical position. Silurian bentonites in Lithuania are mostly characterized by wide and very wide XRD 201 reflections of the main component of sanidine phenocr...

  3. Cellular uptake and cytotoxic potential of respirable bentonite particles with different quartz contents and chemical modifications in human lung fibroblasts.

    Science.gov (United States)

    Geh, Stefan; Yücel, Raif; Duffin, Rodger; Albrecht, Catrin; Borm, Paul J A; Armbruster, Lorenz; Raulf-Heimsoth, Monika; Brüning, Thomas; Hoffmann, Eik; Rettenmeier, Albert W; Dopp, Elke

    2006-02-01

    Considering the biological reactivity of pure quartz in lung cells, there is a strong interest to clarify the cellular effects of respirable siliceous dusts, like bentonites. In the present study, we investigated the cellular uptake and the cytotoxic potential of bentonite particles (Øbentonite samples were tested for endotoxins with the in vitro-Pyrogen test and were found to be negative. Cellular uptake of particles by IMR90-cells was studied by transmission electron microscopy (TEM). Cytotoxicity was analyzed in IMR90-cells by determination of viable cells using flow cytometry and by measuring of the cell respiratory activity. Induced apoptotic cells were detected by AnnexinV/Propidiumiodide-staining and gel electrophoresis. Our results demonstrate that activated bentonite particles are better taken up by IMR90-cells than untreated (native) bentonite particles. Also, activated bentonite particles with a quartz content of 5-6% were more cytotoxic than untreated bentonites or bentonites with a quartz content lower than 4%. The bentonite samples induced necrotic as well as apoptotic cell death. In general, bentonites showed a high membrane-damaging potential shown as hemolytic activity in human erythrocytes. We conclude that cellular effects of bentonite particles in human lung cells are enhanced after chemical treatment of the particles. The cytotoxic potential of the different bentonites is primarily characterized by a strong lysis of the cell membrane. PMID:16059726

  4. 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

  5. Freezing of bentonite. Experimental studies and theoretical considerations

    International Nuclear Information System (INIS)

    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 Ps(w,ΔT) = Ps(w,0 deg C) + Δs(w)*ΔT/νclay(w) where ΔT denotes a temperature difference from 0 deg C, Δs(w) is the difference in partial molar entropy between clay water and bulk water, νclay (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, Δs(w) has a different value dependent on whether ΔT is negative or positive. Above 0 deg C Δs(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 Δs(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 TC. TC 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 recorded continuously. The samples have been varied with respect to

  6. 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. PMID:25536393

  7. Microcapillary flow behavior of magnetic nanofluids in the presence of plate shaped bentonite particles

    International Nuclear Information System (INIS)

    Plate shaped bentonite particles of size ∼600 nm and thickness ∼2 nm are dispersed in a magnetic nanofluid. Magnetic field dependent flow behavior of this composite suspension is studied using a horizontal microcapillary placed between the poles of an electromagnet. The plate shaped bentonite particle produces extra hindrance to the flow under the application of moderate magnetic field and produces an enhanced magnetoviscous effect. 75% volume concentration of bentonite produces eight times larger change in magnetic field dependent viscosity than does the pure magnetic nanofluid. Hindrance to the flow is due to the chain like structure of magnetic nanoparticles, tumbling and rotational motion of bentonite particles and interaction between magnetic and bentonite particles. The field-induced structures are also observed using an optical microscope. Results offer several advantages over the inverse MR effect as well as to study the motion of biological cells and tissues under the effect of magnetic field. -- Highlights: ► Dispersed plate shaped bentonite particles in magnetic fluids to study capillary viscosity. ► Increased viscosity is due to the hindrance to the rotation of the bentonite particles. ► Increase in viscosity is five times larger for bentonite particles than the pure magnetic fluids. ► This is a new kind of magnetoviscous effect, dispersing anisotropic particles in magnetic fluids

  8. Synthesis and characterization of poly(sodium acrylate)/ bentonite superabsorbent composite

    International Nuclear Information System (INIS)

    Poly(sodium acrylate)/bentonite superabsorbent composite with water absorbency 1562 g·g−1 was synthesized by inverse suspension polymerization. The introduction of bentonite improves the water absorbency and facilitates the particle size even distribution of the composite. The network structure in the superabsorbent hydrogel is confirmed.

  9. Facile synthesis of carbon nanotube/natural bentonite composites as a stable catalyst for styrene synthesis.

    Science.gov (United States)

    Rinaldi, Ali; Zhang, Jian; Mizera, Jan; Girgsdies, Frank; Wang, Ning; Hamid, Sharifah Bee Abd; Schlögl, Robert; Su, Dang Sheng

    2008-12-28

    Natural bentonite mineral, without any wet chemical treatment, was used directly to catalyze the growth of multi-wall CNTs and the produced CNTs/bentonite as an integrated composite stably catalyzed the oxidative dehydrogenation reaction over a long period of time; this concept provides a highly economical way for large-scale synthesis of nanocarbons and manufacture of styrene synthesis catalysts. PMID:19057768

  10. 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.

  11. Physico-chemical characterization of bentonite and its application for Mn2+ removal from water

    Directory of Open Access Journals (Sweden)

    Ranđelović Marjan S.

    2011-01-01

    Full Text Available Bentonite is mainly composed of clay minerals from smectite group, therefore it has a well developed and chemically active surface area and high cation exchange capacity. Moreover, an interlayer space of smectite has unusual hydration properties, which manifest as swelling of bentonite in water. These properties make bentonite as a commonly used raw material in chemistry and industry, and it is very important in environmental protection and water treatment as an effective sorbent of heavy metals. The results of X-ray diffraction, a cationic exchange capacity, specific surface area, acid-base properties of the surface and the swelling index showed that the bentonite sample contains mostly montmorillonite. The aim of this study was to test the efficacy of bentonite in the removal of Mn2+ from aqueous systems. The experimental results of Mn2+ adsorption on the bentonite were interpreted by Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherms. The adsorption isotherm studies indicate that the adsorption of Mn2+ follows Langmuir isotherm very well. Theoretical monolayer saturation capacity according to Langmuir model was 12.41 mg/g. The removal of Mn2+ is achieved by ion exchange mechanism with naturally occurring cations in bentonite, as well as by forming the inner- and outer-sphere complexes with bentonite surface.

  12. Literature study on the microstructure of bentonite and its effect on diffusion

    International Nuclear Information System (INIS)

    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.)

  13. Iron and organo-bentonite for the reduction and sorption of trichloroethylene.

    Science.gov (United States)

    Cho, Hyun-Hee; Lee, Taeyoon; Hwang, Sun-Jin; Park, Jae-Woo

    2005-01-01

    Hybrid barriers using dechlorination and immobilization were studied to remove trichloroethylene (TCE) in this study. Hybrid barriers of iron filings and organo (hexadecyltrimethylammonium, HDTMA)-bentonite were simulated in columns to assess the performance of the hybrid barriers. TCE reduction rate for the mixture of zero valent iron (ZVI) and HDTMA-bentonite was approximately seven times higher than that for ZVI, suggesting the reduction of TCE was accelerated when HDTMA-bentonite was mixed with ZVI. For the column of two separate layers of iron and HDTMA-bentonite, TCE reduction rate was nearly similar to that for ZVI alone, but the partition coefficient (Kd) was 4.5 times higher than that for ZVI only. TCE was immobilized in the first layer with HDTMA-bentonite due to sorption, and then dechlorinated in the second layer with iron filings due to reduction. The HDTMA-bentonite and minimally-desorbed HDTMA from the organo-bentonite are believed to contribute the increase in TCE concentration on iron surface so that more TCE could be available for reduction. Therefore, the incorporation of HDTMA-bentonite into ZVI not only can effectively retard the transport of chlorinated organic contaminants from landfill leachate or oil shock in subsurface environment, also can expedite the reduction rate of TCE. PMID:15522338

  14. 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

  15. Bentonite barriers. New experiments and state of the art. Bentonite as barrier material for the sealing of underground disposal sites. Final report

    International Nuclear Information System (INIS)

    Bentonite is intensively investigated from many institutes for its properties and feasibility as engineering barrier material for many environmental facilities like landfill, underground landfill for chemotoxic waste and also HLW repositories. A summary of the current state of knowledge regarding the origin of bentonites and different processes through bentonite is provided together with the potential further research and development needs. Diffusion experiments with gas (CO2, H2, CH4 and SF6) and heavy metals Pb, Cd and Cs in highly saline solution (50 % and 90 % NaCl solutions, 90 % IP21 solution) at room temperature and atmosphere pressure conditions through compacted MX-80 bentonite with three different bulk dry densities (1,400 kg/m3,1,600 kg/m3 and/or 1,800 kg/m3) were performed. Numerical simulations of some experiments were undertaken.

  16. 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)

    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

  17. Preparation, characterization and thermal stability of bentonite modified with bis-imidazolium salts

    Energy Technology Data Exchange (ETDEWEB)

    Makhoukhi, B., E-mail: benamarmakh@yahoo.fr [Laboratory of Separation and Purification Technologies, Department of Chemistry, Tlemcen University, Box 119, Tlemcen (Algeria); Villemin, D. [Laboratoire de Chimie Moléculaire et Thio-organique, UMR CNRS 6507, INC3M, FR 3038, ENSICAEN and Université de Caen, 14050 Caen (France); Didi, M.A. [Laboratory of Separation and Purification Technologies, Department of Chemistry, Tlemcen University, Box 119, Tlemcen (Algeria)

    2013-02-15

    Sodium bentonite was modified with several organic bis-imidazolium salts. Organoclays with water soluble surfactants were prepared by the traditional cation exchange reaction. The bis-imidazolium-bentonites were characterized by Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction analysis (PXRD) and thermogravimetric analysis (TGA). The effect of chemical composition and molecular weight of the salts on the thermal stability and basal spacing were evaluated. The bis-imidazolium-bentonites showed enhanced thermal stability (300–400 °C) and may be potentially useful materials for melt processing of polymer/layered silicates nanocomposites. - Highlights: ► Geometry and volume of the molecule influence on interlayer spacing of modified bentonites. ► The intercalation increases with molecule length. ► The modified bentonites have an appreciably higher thermal stability.

  18. Corrosion behavior of carbon steel in wet Na-bentonite medium

    International Nuclear Information System (INIS)

    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)

  19. 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. PMID:21945787

  20. The Bentonite Barrier: Microstructural properties and the influence of γ-radiation

    International Nuclear Information System (INIS)

    The main objectives of this work were to investigate three different topics relevant for the bentonite barrier, namely: - The microstructural properties of compacted bentonite, by i) testing the possibility of colloid transport and ii) by determining the interparticle and interlayer porosity, i.e. the free porosity in the saturated compacted bentonite by a basal spacing analysis (Paper I and II, respectively). - Potential γ-radiation-induced effects on i) montmorillonite colloid stability and changes in sol/gel properties, ii) the structural Fe(II)/Fe(III) ratio in montmorillonite and its effect on the montmorillonites reactivity towards one of the major oxidants formed upon water radiolysis, H2O2, and iii) radionuclide retention in compacted bentonite (Paper III-V, respectively). - Potential interactions of bentonite particles with Silica sol, i.e. the SiO2-colloids that are planned to be used as an injection grout during construction of the repository (Paper VI)

  1. Erosion of bentonite by flow and colloid diffusion

    International Nuclear Information System (INIS)

    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

  2. Sorption of cesium on bentonite: The role of calcite

    International Nuclear Information System (INIS)

    Full text: Since bentonite is investigated for its use in Engineered Barriers Systems as backfill material, many studies of their surfaces properties have been performed in the past years to qualify and quantify adsorption on their surfaces, which can be one of the major processes limiting migration of radionuclides away from a disposal site. Nevertheless, most of these studies concerned simplified systems, such as Na-montmorillonite in mono-electrolyte solution. As ion-exchange processes are of importance in water-clays interactions, adsorption of natural major ions has also to be taken into account for natural systems. The aim of this work is (i) to quantify the sorption of the natural major cations on the montmorillonite surface, (ii) to compare the sorption of cesium, in two different systems, a simple one (Na-montmorillonite in NaNO3 0.05 Mol.L-1) and a complex one (natural bentonite in a synthetic natural water) and then (iii) to assess the influence of the natural major ions on this sorption, and to identify the role of the calcite phase present in bentonite. The methodology used consists in several batch experiments, first considering a very simple solution (NaNO3), then using mixtures of two different electrolytes, and lastly using a synthetic natural water. A surface complexation model, describing the surface of clays as a mixture of ion-exchange and complexation surface sites, is used to provide interpretations and quantifications of the sorption processes. Observed results indicate that affinity for the montmorillonite surface is greatest for Ca, then Mg and then K. The sorption of cesium is strongly affected by the presence in solution of Ca, witch can come from the partial dissolution of calcite. (author)

  3. Interactions between copper corrosion products and MX-80 bentonite

    International Nuclear Information System (INIS)

    The report presents results from a study of the possible interaction between copper corrosion products and MX-80 bentonite under conditions that might occur in a final repository for spent nuclear fuel in Finland. The first part of the report describes the results from a literature survey, the objective of which was to identify some relevant corrosion products that might form when copper corrodes in wet MX-80 bentonite. On the basis of the literature survey, atacamite and a green copper corrosion product produced in-house were used for experimental studies. Experiments were performed with both soft and compacted MX-80. The soft samples consisted of water-saturated MX-80 mixed with CuCl2 solutions of various concentrations. The samples were kept under anaerobic conditions at ambient room temperature or at 75 deg C for 330 days. Porewater samples were then squeezed from the samples and analysed. Compacted MX-80 samples were stored under anaerobic conditions and kept in contact with an NaCl solution. The samples were kept at room temperature and 75 deg C for 2.9 years and then analysed. The presence of either atacamite or the green copper corrosion product on the plates did not have any notable effects on the porewater chemistry. However, the Cu concentration profiles indicated that the corrosion products did dissolve, and then diffused into the surrounding bentonite. Concentration profiles were found to be roughly the same, irrespective of whether the samples had been stored at room temperature or at 75 deg C. (orig.)

  4. Influence of dry density on HTO diffusion in GMZ bentonite

    International Nuclear Information System (INIS)

    With the low permeability and high swelling property, Gaomiaozi (GMZ) bentonite is regarded as the favorable candidate backfilling material for a potential repository. The diffusion behaviors of HTO in GMZ bentonite were studied to obtain effective diffusion coefficient (De) and accessible porosity (ε) by through- and out-diffusion experiments. A computer code named Fitting for diffusion coefficient (FDP) was used for the experimental data processing and theoretical modeling. The De and ε values were (5.2-11.2) x 10-11 m2/s and 0.35-0.50 at dry density from 1,800 to 2,000 kg/m3, respectively. The De values at 1,800 kg/m3 was a little higher than that of at 2,000 kg/m3, whereas the D e value at 1,600 kg/m3 was significantly higher (approximately twice) than that of at 1,800 and 2,000 kg/m3. It may be explained that the diffusion of HTO mainly occurred in the interlayer space for the highly compacted clay (dry density exceeding 1,300 kg/m3). 1,800 and 2,000 kg/m3 probably had similar interlayer space, whereas 1,600 kg/m3 had more. Both De and ε values decreased with increasing dry density. For compacted bentonite, the relationship of De and ε could be described by Archie's law with exponent n = 4.5 ± 1.0. (author)

  5. Performance of bentonite/crushed tuff seals for nuclear waste repositories

    International Nuclear Information System (INIS)

    Mixtures of bentonite and crushed rock are potential sealing materials for high level nuclear waste repositories. To allow for overall repository performance assessments, evaluations of the sealing performance under diverse conditions are needed. American Colloid c/s granular bentonite 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. The sealing performance of bentonite/crushed rock mixtures can be enhanced by increasing the amount of bentonite to 35%. 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 takes place are deemed critical. The pressure required to generate a critical gradient probably is related to the yield stress of the bentonite in the mixture. A difference up to one or two orders of magnitude has been observed between the vertical and horizontal permeabilities. The high horizontal permeability results from the uneven bentonite distribution in the pores between the crushed rock particles due to particle segregation. Temperature seems to have no negative effects on the sealing performance within the test range from room temperature to 60. Recommendations for future research are included. 15 refs., 5 figs., 1 tab

  6. Effective diffusivities of iodine, chlorine, and carbon in bentonite buffer material

    International Nuclear Information System (INIS)

    Effective diffusivities of iodine, chlorine, and carbon in mixtures of bentonite and sand were determined by measuring the effective diffusivities of common chemical compounds labeled with radioactive isotopes of these elements. For carbon, both inorganic and organic carbon compounds were used in order to consider the variety of chemical forms of carbon possible in a radioactive waste repository. The bentonite content and dry density of the bentonite-sand mixture were varied. Two chemically different aqueous solutions, representing concrete pore water and bentonite pore water, were used to represent different conditions that could affect diffusivity in bentonite buffer material in a hypothetical radioactive waste disposal situation. The effective diffusivities of iodine, chlorine, and carbon tended to decrease with increasing bentonite content and dry density of the mixture. In the presence of simulated concrete pore water, the effective diffusivities for iodine, chlorine, and carbon in the bentonite mixtures were not higher than those obtained when simulated bentonite pore water was used. Except for some organic compounds, the measured effective diffusivities were lower than that of tritiated water under the same experimental conditions. This was attributed primarily to exclusion of anions from the bentonite pores. The effective diffusivity of carbon depended on its chemical form. The effective diffusivity of the anionic forms of organic carbon tested (carboxylic acids) was as low as that of inorganic anionic carbon. Measured effective diffusivities were compared with those calculated using a model based on electrical double layer theory. The theory was applied to calculate distributions of electrolyte ions and diffusion ions in the bentonite pores. The calculated effective diffusivities showed good agreement with the measured values

  7. Study of aggregation in a micellar solution within bentonite clay by SANS

    International Nuclear Information System (INIS)

    Aggregation studies of surfactant solutions exposed to different surfaces are relevant to their applications as detergents, oil recovery agents etc. The infusion of SDS micellar solutions into the pores of compacted normal bentonite clay and the clay saturated with sodium at different concentrations viz. 1, 2 and 5 molar percentages, has been studied here by small angle neutron scattering and X-ray diffraction. In the sodium saturated bentonite, the Na+ ion (having a positive scattering length) is held in the interlayer of the clay and on account of this, the scattering length density difference (i.e. contrast) between the bentonite matrix and the inter-layer pores is lower than the bentonite which has less sodium. The average pore size in normal bentonite clay is 13 Å while in the clay saturated with 1M Na+ ions it is 20 Å . For a 10% SDS solution, the micelles are prolate ellipsoids having average semi major and minor axes of 22.5 Å and 16.7 Å, respectively with an effective charge of 30 e.u. and an aggregation number of 75. Both aggregation number and effective charge increase with concentration of SDS solution. Sodium is present in normal bentonite but is enhanced in concentration in the case of sodium saturated bentonite. Aggregation number and micellar separation are reduced for SDS loaded into raw bentonite clay and then into Na saturated clay. Likewise, there is a reduction of fractional charge on the micelle in going from raw to sodium bentonite caused by the Na+ ions present on the surface of the clay pores which would be attracted to the negative surface of each micelle thereby reducing its net charge. The effective attraction between micelles and Na+ ion concentration control the growth of aggregates, their volumes and aggregation numbers. Hence the sodium ion in the bentonite plays a vital role in the change of these parameters by effectively reducing charge on the micellar aggregates.

  8. Adsorption of La(III) onto GMZ bentonite. Effect of contact time, bentonite content, pH value and ionic strength

    International Nuclear Information System (INIS)

    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)

  9. ADSORPTION STUDY OF RHODAMIN B DYE ON IRAQI BENTONITE AND MODIFIED BENTONITE BY NANOCOMPOUNDS TIO2, ZNO, AL2O3 AND SODIUM DODECYL SULFATE

    Directory of Open Access Journals (Sweden)

    Iqbal Salman AL-Jobouri

    2013-01-01

    Full Text Available The adsorption of Rhodamin B on Iraqi bentonite at the concentration range from 50 to 250 μg mL-1 was studied, Nano compounds; ZnO, TiO2, Al2O3 m and SDS in different amounts 0.01-0.1 g 10-1 g of Bentonite were used to modified the adsorption capacity of bentonite to remove the Rhodamin B from aqueous solutions. The study indicated that using 0.05 g and 0.1 of Sodium Dodecyl Sulfate (SDS lead to increase the percentage removal (%R from 79.3% for pure bentonite to 99.3%. While using 0.05 g TiO2 lead to increase the %R to 98.9%, 0.05 of ZnO to 98.6%. The other amount additives and Al2O3 using was not success to increase the %R for the Rhodamin B on bentonite surface. SEM measurement was achieved to discover the Nanoparticl exists in the bentonite surfaces.

  10. Microbial communities in bentonite formations and their interactions with uranium

    International Nuclear Information System (INIS)

    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

  11. 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...... 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 in...... saline waters need a careful risk evaluation due to potential lanthanum release....

  12. Swelling characteristics of immersed sand-bentonite mixtures

    Institute of Scientific and Technical Information of China (English)

    丰土根; 崔红斌; 孙德安; 杜冰

    2008-01-01

    A laboratory one-dimensional consolidation apparatus was employed to research the swelling stress and volume of the sand-bentonite mixture under immersed conditions. The stress-strain characteristics of mixtures under varied mixing ratios and loading statuses were analyzed. Based on the results of tests, the mechanism of mixture swelling and collapsing was further discussed. The results show that mixtures with low sand ratios are suitable as hydraulic barrier or containment barriers of general landfills, geological repository and other hydraulic infrastructure works.

  13. 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.

  14. 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.

  15. Influence of rotating magnetic fields on THM growth of CdZnTe crystals under microgravity and ground conditions

    Science.gov (United States)

    Stelian, Carmen; Duffar, Thierry

    2015-11-01

    The influence of rotating magnetic fields (RMF) on species transport and interface stability during the growth of Cd0.96Zn0.04Te:In crystals by using the traveling heater method (THM), under microgravity and terrestrial conditions, is numerically investigated. The numerical results are compared to ground and space experiments. The modeling of THM under ground conditions shows very deleterious effects of the natural convection on the morphological stability of the growth interface. The vertical flow transports the liquid of low Te concentration from the dissolution interface to the growth interface, which is consequently destabilized. The suppression of this flow, in low-gravity conditions, results in higher morphological stability of the growth interface. Application of RMF induces a two flow cell pattern, which has a destabilizing effect on the growth interface. Simulations performed by varying the magnetic field induction in the range of 1 - 3 mT show optimal conditions for the growth with a stable interface at low strength of the magnetic field (B = 1 mT). Computations of indium distribution show a better homogeneity of crystals grown under purely diffusive conditions. Rotating magnetic fields of B = 1 mT induce low intensity convection, which generates concentration gradients near the growth interface. These numerical results are in agreement with experiments performed during the FOTON M4 space mission, showing good structural quality of Cd0.96Zn0.04Te crystals grown at very low gravity level. Applying low intensity rotating magnetic fields in ground experiments has no significant influence on the flow pattern and solute distribution. At high intensity of RMF (B = 50 mT), the buoyancy convection is damped near the growth front, resulting in a more stable advancing interface. However, convection is strengthening in the upper part of the liquid zone, where the flow becomes unsteady. The multi-cellular unsteady flow generates temperature oscillations, having

  16. Efficient removal of Eu(III) from aqueous solutions using super-adsorbent of bentonite-polyacrylamide composites

    International Nuclear Information System (INIS)

    The bentonite has been studied extensively to preconcentrate radionuclides from aqueous solutions, however, the low sorption capacity limits it application in real work. Herein, bentonite embedded in the polyacrylamide (PAAm) gels is synthesized and used as a novel adsorbent for the removal of Eu(III) from aqueous solutions. The bentonite-PAAm composites show much higher sorption capacity for Eu(III) preconcentration than bare bentonite. The bentonite-PAAm composites can be used as super-adsorbent for the removal of Eu(III) from aqueous solution in radioactive pollution cleanup. (author)

  17. Retention of chromium by modified Al-Bentonite Retenção de cromo por Al-bentonita modificada

    OpenAIRE

    C. Volzone; L.B. Garrido

    2002-01-01

    Retention of chromium (III) from a tanning wastewater by modified Al-bentonites was studied. One bentonite from San Juan province, Argentina, was used. Al-bentonite was prepared by contact of bentonite with hydrolyzed OH-Al solutions (0.10 M in Al) for 24 hours. The modified Al-bentonites were obtained by: a) treatment with 0.5 M sodium chloride; b) with 0.5 M sodium chloride adjusted at pH 8; and c) treatment with an hexametaphosphate solution after sodium addition. Then, the samples were dr...

  18. 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.

  19. FEBEX-DP. Dismantling the ''full-scale engineered barrier experiment'' after 18 years of operation at the Grimsel Test Site, Switzerland

    International Nuclear Information System (INIS)

    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.

  20. Modeling erosion of unsaturated compacted bentonite by groundwater flow; pinhole erosion test case

    International Nuclear Information System (INIS)

    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

  1. Stress/strain/time properties of highly compacted bentonite

    International Nuclear Information System (INIS)

    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)

  2. 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)

  3. Buffer construction technique by means of granular bentonite

    International Nuclear Information System (INIS)

    Buffer construction technology using bentonite pellets as filling material is one of the promising technologies for enhancing the ease of buffer construction. In this study, a bentonite pellet filling test was conducted, using a filling system equipped with a screw conveyor system, in a full-scale simulated disposal drift. A simulated waste disposal drift configured as a half-cross-section model with a height of 2.22 m and a length of 6.0 m was constructed for the test, and two dummy overpacks were placed in the drift. The filling test was conducted in two phases. The average dry density of the buffer fill was 1.29 Mg/m3, which was close to the target value. The angle of repose was approximately 40 degrees. The test results indicate that the buffer construction technology using screw conveyor system for pellet conveyance in a waste disposal drift is a promising technology of the disposal of high level radioactive wastes. (author)

  4. Electrophysical characteristics of polyurethane/organo-bentonite nano composites

    International Nuclear Information System (INIS)

    Modification of the Egyptian Bentonite (EB) was carried out using organo-modifier namely; octadecylamine ODA. Before the modification, the cation exchange capacity (CEC) of the EB was measured, also it was purified from different impurities using HCl and distilled water. The Organo-bentonite OB was characterized using IR, XRD, and TEM. PU/ODA-B nano composites were prepared by in situ polymerization then characterized by XRD and TEM. An amount of ODA-B ranging from 0.25% up to 5% by weight was added to the polyol component of the resin before mixing with toluene diisocynate TDI. TEM showed that the nano composites achieved good dispersion in the polyurethane matrix. The mechanical, swelling and electrical properties of the nano composites were measured. The results indicate that the tensile strength of all the nano composites enhanced with the addition of OB compared with the pure PU. The crosslink density of the nano composites increases with increasing the content of OB. The Pool-Frenckel conduction mechanism predominates for all the nano composite samples and the blank one

  5. Evaluation of hydraulic conductivities of bentonite and rock under hyper alkaline and nitrate conditions

    International Nuclear Information System (INIS)

    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)

  6. Research on bed layer made from bentonite for system of radioactive waste storage

    International Nuclear Information System (INIS)

    Nowadays, bentonite is widely used in many different fields such as environment, building, nanocomposite material and so on. Vietnam has huge reserve of bentonite. Montmorillonite of bentonite deposit in BinhThuan and Lam Dong ore ranges from 25 to 45 %. This project presents the results of research on the bed layer made from bentonite for system of radioactive waste storage. Our project has also researched the absorption capability of UO22+, Th4+ and heavy metals such as Pb2+ and Cd2+ on BinhThuan and Lam Dong bentonite in different conditions such as absorption time, pH of solution, concentration, amount of absorbent, etc. The swelling characteristic, the endosmosis of BinhThuan and Lam Dong bentonite have been identified. Our experiments showed that the bed layer made from BinhThuan and Lam Dong bentonite with size: (100 x 100 x 10) mm, additives Na2SiO3 is widely used for system of radioactive waste storage. (author)

  7. Applicability of low alkaline cement for construction and alteration of bentonite in the cement. 2

    International Nuclear Information System (INIS)

    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)

  8. Project Caesium - An ion exchange model for the prediction of distribution coefficients of caesium in bentonite

    International Nuclear Information System (INIS)

    A surface chemical model is established to thermodynamically describe caesium sorption on bentonite. Caesium sorption is studied on Wyoming bentonite MX-80 in solutions of NaCl, KCl, MgCl2, CaCl2, NaNO3 and Ca(NO3)2 of concentrations varying between 0.025M and 1M, as well as in the weakly saline Allard groundwater and the strongly saline Aespoe groundwater. Based on these experiments it is shown that the sorption behaviour of caesium on bentonite can be described, within the experimental and model uncertainties, in terms of a one-site ion exchange model. The ion exchange constant for the replacement of Na+ on montmorillonite by Cs+ is logKex degrees = 1.6. The model predictions compare well with sorption data published in the open literature on both Wyoming bentonite MX-80 and other types of bentonite. For the analysis of diffusion experiments in compacted bentonite, the apparent diffusivity of tritiated water, HTO, is used as an analogue to estimate the pore diffusivity of Cs+. Since insufficient information is available at present to estimate the porosity actually available for diffusion in compacted bentonite, it is assumed that the diffusion porosity can be approximated by using the value of the bulk porosity. Under these circumstances, the cation ex change capacity (CEC) found to be available for the diffusing species in compacted bentonite corresponds to about 12% of the total CEC of bentonite. It is recognised that the errors made in the estimation of the pore diffusivity and of the diffusion porosity are contained in the reduction factor of the CEC. A discussion of the factors affecting the diffusivities of radionuclides and the problem of establishing consistent sets of diffusivity data is given in the Appendix. 33 refs, 7 figs, 12 tabs

  9. Characterization of organo-modified bentonite sorbents: The effect of modification conditions on adsorption performance

    International Nuclear Information System (INIS)

    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

  10. 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.

  11. 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 framework of the ENRESA programme for the assessment of the long-term behaviour of the bentonite-engineered barrier for a deep radwaste geological repository, analogue studies on several bentonite deposits are conducted at CIEMAT. Among these analogue studies, the thermal effect induced by volcanic intrusions on bentonite deposits is highlighted. In the Cabo de Gata volcanic region, there are several analogue scenarios where these studies have been performed, such as the Cala de Tomate bentonite deposit that was intruded by a pyroxene andesite volcanic dome. However, geological, mineralogical, physicochemical, geochemical and stable isotopic data obtained from the smectites do not allow to establish any analogy with the thermal effect expected on the bentonite-engineered barrier of a deep geological repository after burial. Thus, the bentonitisation processes took place after the intrusion of the dome, as a result of meteoric diagenesis intensively developed on faulting zone affecting the parent pyroclastic acid tuffs. This faulting process occurred after the dome intrusion. However, the physicochemical characteristics of these smectites, specially the exchangeable cations, allow to consider this bentonite deposit as a natural analogue of the saline effect on the clayey barrier. This analogy has been established because Na-smectites are present in this deposit and, up to our present knowledge, it is the first time that these smectites occur naturally in the Cabo de Gata-La Serrata de Nijar volcanic region. As a consequence, the main objectives of this work are: i) to characterise these smectites; ii) to establish their genesis and processes affecting them after their formation and iii) to identify the effects on the bentonite-engineered barrier should it were affected by a Na-rich saline waterfront. (authors)

  12. Concrete/Febex Bentonite Interaction: Results On Short-Term Column Experiments

    Energy Technology Data Exchange (ETDEWEB)

    Escribano, A.; Turrero, M.J.; Torres, E.; Martin, P.L. [CIEMAT, Environmental Department, Avda. Complutense, 22, 28040 Madrid (Spain)

    2008-07-01

    Interaction between the alkaline pore fluids from the concrete engineered barriers and the bentonite at the repository conditions may generate products that can diffuse through the porous structure of the bentonite affecting their properties. A comprehensive study based on series of short term experiments is being performed to provide experimental evidences on the physical, chemical and mineralogical changes during the concrete-compacted bentonite interaction. Samples were analyzed by XRD, SEM-EDS and FTIR. Measurements of swelling capacity, specific surface area and chemical analysis for cation exchange capacity and soluble salts analyses were also performed. (authors)

  13. Long-term dissolution behavior of spent fuel in compacted bentonite and synthetic granitic groundwater

    International Nuclear Information System (INIS)

    This contribution describes experimental work which aims to get the information on corrosion behaviour of Spent Fuel, and to obtain the release rate of radionuclides from the fuel within domestic bentonite and synthetic granitic ground water. Specimens of fuel with burn-up up to 39 GWd/tU, with and without bentonite, have been subjected to leaching. The effects of bentonite on the dissolution rate, and of structural materials, copper and stainless steel on caesium release have been identified and are reported. (author)

  14. The study on bentonite slurry grout with ethanol for fractured rock masses

    International Nuclear Information System (INIS)

    The purpose of this paper is to propose the grouting material and method for fractured rock masses. So experimental study is executed in order to grasp that the properties of grouting material is stable and impermeable. In this study, experiments of hydraulic test and grouting injection test are performed on bentonite slurry mixes in the laboratory. From the results of the tests, a mixer of ethanol and bentonite is found to be very suitable for a grouting material. Also, dynamic grouting method is able to inject the concentrated bentonite slurry in the fractured aperture. (author)

  15. NBR/ORGANOMODIFIED BENTONITE INTERCALATED HYBRIDS AND THEIR EFFECTS ON THE TOUGHNESS OF PVC

    Institute of Scientific and Technical Information of China (English)

    Chang-jiang You; De-min Jia; Zeng-yong Zhen; Kui Ding; Song Xi; Hai-lin Mo; Yong-hua Zhang

    2003-01-01

    Hybrids of intercalative nitrile-butadiene rubber/organomodified bentonite (NBR/OMB) were prepared by the latex intercalation technique. Investigation of their mechanical properties and the microstructure of NBR/OMB showed that the organomodified bentonite is an effective toughener for NBR. Transmission electronic microscopy (TEM) and X-ray diffraction (XRD) tests showed that the NBR macromolecule could be intercalated into the galleries of bentonite.Incorporation of NBR/OMB hybrids as tougheners into poly(vinyl chloride) (PVC) results in a substantial increase in the impact strength of PVC, but little decrease in its tensile strength and flexural strength, compared to the unmodified PVC.

  16. Concrete/Febex Bentonite Interaction: Results On Short-Term Column Experiments

    International Nuclear Information System (INIS)

    Interaction between the alkaline pore fluids from the concrete engineered barriers and the bentonite at the repository conditions may generate products that can diffuse through the porous structure of the bentonite affecting their properties. A comprehensive study based on series of short term experiments is being performed to provide experimental evidences on the physical, chemical and mineralogical changes during the concrete-compacted bentonite interaction. Samples were analyzed by XRD, SEM-EDS and FTIR. Measurements of swelling capacity, specific surface area and chemical analysis for cation exchange capacity and soluble salts analyses were also performed. (authors)

  17. Study of Interaction between Fly Ash-cement and Bentonite Matrices

    Directory of Open Access Journals (Sweden)

    Daněk Tomáš

    2015-01-01

    Full Text Available Among the important factors characterizing the quality of sealing mixtures is strength, durability, compatibility and permeability. Experimental work was therefore conducted to assess the use of cement, fly ash, gravel and bentonite in the form of artificial self-hardening sealing mixture. The results of the work show a good compatibility between the bentonite and cement during its fly ash replacement. Compactness of the structure was confirmed by studying of permeability and SEM microscopy, which in the system of ash-cement-bentonite matrix allowed assessing successive microstructure development of hydrating gel.

  18. Modified bentonite as adsorbent and catalyst for purification of wastewaters containing dyes

    Directory of Open Access Journals (Sweden)

    Žunić Marija J.

    2010-01-01

    Full Text Available Modification and characterization of bentonite from location Bogovina, Serbia was performed in order to obtain material applicable in wastewater purification. The <75μm bentonite fraction was used in organobentonite synthesis while the <2μm bentonite fraction, obtained by hydroseparation was used in pillaring procedure. Organo-modification of bentonite was performed with (1-hexadecyltrimethylammonium bromide (HDTMA-Br. Pillared bentonite was obtained using standard procedure. Al3+ and Fe3+ ions were incorporated in pillars in 4:1 ratio and applied as catalyst in catalytic wet peroxide oxidation. Differences in structure of starting and modified bentonites were established by XRD analysis and nitrogen physisorption on -196 °C. The (001 smectite peak around 2θ = 6° shifts during the modification process. The Na-exchange process lowered d001 from 1.53 nm (2θ = 5.78° for starting clay to 1.28 nm (2θ = 6.92°, but the clay retained its swelling properties. The pillaring process increased and fixed the basal spacing to 1.74 nm. Intercalation of HDTMA ions into smectite structure increased d001 to 2.00 nm for organobentonite. Specific surface area, SBET, was affected by particle size and type of modification. The samples with finer bentonite fraction had higher SBET due to increased smectite content. Na-exchanged bentonite samples had higher SBET value than starting clay samples of same granulation. Organomodification caused dramatic decrease in SBET value, while the pillaring process lead to an increase of SBET value. Adsorptive and catalytic purification of wastewaters containing dyes was tested using Acid Yellow 99 as a model dye. Na-exchanged bentonite had greater adsorption affinity for dye adsorption than raw bentonite owing to higher SBET. By organomodification this affinity was enhanced more than 70 times due to transition of bentonite surface from hydrophilic to organophilic. Al,Fe pillared bentonite was proven to be efficient in

  19. Removal of natural uranium from water produced in the oil industry using Algerian bentonite

    International Nuclear Information System (INIS)

    Batch sorption experiments have been carried out to remove natural uranium (NORM) from water obtained together with crude oil and natural gas, using Algerian bentonites. The effect of some important factors such as S/L ratio, pH, initial concentration, particle size was evaluated and a kinetic study performed. The value of the distribution coefficient (Kd) at equilibrium for natural uranium varied from 30 to 600 cm3 x g-1 and 50 to 1100 cm3 x g-1 (∼ 10% margin error) using natural bentonite and drilling bentonite, respectively. The isotherms showed that the data are consistent with both Freundlich and Langmuir models. (author)

  20. Experimental study on self-healing of bentonite/sand mixtures in hydraulic permeability

    International Nuclear Information System (INIS)

    Effects of gas permeation on the impervious characteristics of bentonite/sand mixtures were studied experimentally by conducting permeability tests with various fluids and microscopic observations. In this test, hydraulic permeabilities were measured before/after helium gas was applied to permeate through the mixtures. It was found that gas formed preferential paths to migrate through the mixtures, and that the bentonite/sand mixtures never deteriorated in impervious capacity because the paths were-filled with swelling bentonite in re-saturation. (author)

  1. Bentonite-stabilized CDA/CTA membranes for seawater desalination. Pt. 2

    International Nuclear Information System (INIS)

    The bentonite-stabilized seawater desalination membranes developed at GKSS were characterized by two transport coefficients. Both the hydrodynamic permeability as well as the electro-mechanical coefficient were significantly changed after 2000 hours RO rest runs. Their alterations were interpreted - applying the fively-porous membrane model - as an increase of the diffusion potential and a decrease of the streaming potential. The salt diffusion coefficient was analysed to be diminished by about 10%. The lowest performance changes of the membranes with 1000 ppm bentonite dope, support the experimental findings of flux-stabilization of bentonite-containing CDA/CTA membranes, published previously. (orig.)

  2. Thermo-hydro-geochemical modelling of the bentonite buffer. LOT A2 experiment

    Energy Technology Data Exchange (ETDEWEB)

    Sena, Clara; Salas, Joaquin; Arcos, David (Amphos 21 Consulting S.L., Barcelona (Spain))

    2010-12-15

    The Swedish Nuclear Fuel and waste management company (SKB) is conducting a series of long term buffer material (LOT) tests at the Aespoe Hard Rock Laboratory (HRL) to test the behaviour of the bentonite buffer under conditions similar to those expected in a KBS-3 deep geological repository for high level nuclear waste (HLNW). In the present work a numerical model is developed to simulate (i) the thermo-hydraulic, (ii) transport and (iii) geochemical processes that have been observed in the LOT A2 test parcel. The LOT A2 test lasted approximately 6 years, and consists of a 4 m long vertical borehole drilled in diorite rock, from the ground of the Aespoe HRL tunnel. The borehole is composed of a central heater, maintained at 130 deg C in the lower 2 m of the borehole, a copper tube surrounding the heater and a 100 mm thick ring of pre-compacted Wyoming MX-80 bentonite around the copper tube /Karnland et al. 2009/. The numerical model developed here is a 1D axis-symmetric model that simulates the water saturation of the bentonite under a constant thermal gradient; the transport of solutes; and, the geochemical reactions observed in the bentonite blocks. Two cases have been modelled, one considering the highest temperature reached by the bentonite (at 3 m depth in the borehole, where temperatures of 130 and 85 deg C have been recorded near the copper tube and near the granitic host rock, respectively) and the other case assuming a constant temperature of 25 deg C, representing the upper part of borehole, where the bentonite has not been heated. In the LOT A2 test, the initial partially saturated bentonite becomes progressively water saturated, due to the injection of Aespoe granitic groundwater at granite - bentonite interface. The transport of solutes during the bentonite water saturation stage is believed to be controlled by water uptake from the surrounding groundwater to the wetting front and, additionally, in the case of heated bentonite, by a cyclic evaporation

  3. Thermo-hydro-geochemical modelling of the bentonite buffer. LOT A2 experiment

    International Nuclear Information System (INIS)

    The Swedish Nuclear Fuel and waste management company (SKB) is conducting a series of long term buffer material (LOT) tests at the Aespoe Hard Rock Laboratory (HRL) to test the behaviour of the bentonite buffer under conditions similar to those expected in a KBS-3 deep geological repository for high level nuclear waste (HLNW). In the present work a numerical model is developed to simulate (i) the thermo-hydraulic, (ii) transport and (iii) geochemical processes that have been observed in the LOT A2 test parcel. The LOT A2 test lasted approximately 6 years, and consists of a 4 m long vertical borehole drilled in diorite rock, from the ground of the Aespoe HRL tunnel. The borehole is composed of a central heater, maintained at 130 deg C in the lower 2 m of the borehole, a copper tube surrounding the heater and a 100 mm thick ring of pre-compacted Wyoming MX-80 bentonite around the copper tube /Karnland et al. 2009/. The numerical model developed here is a 1D axis-symmetric model that simulates the water saturation of the bentonite under a constant thermal gradient; the transport of solutes; and, the geochemical reactions observed in the bentonite blocks. Two cases have been modelled, one considering the highest temperature reached by the bentonite (at 3 m depth in the borehole, where temperatures of 130 and 85 deg C have been recorded near the copper tube and near the granitic host rock, respectively) and the other case assuming a constant temperature of 25 deg C, representing the upper part of borehole, where the bentonite has not been heated. In the LOT A2 test, the initial partially saturated bentonite becomes progressively water saturated, due to the injection of Aespoe granitic groundwater at granite - bentonite interface. The transport of solutes during the bentonite water saturation stage is believed to be controlled by water uptake from the surrounding groundwater to the wetting front and, additionally, in the case of heated bentonite, by a cyclic evaporation

  4. A study on long term stability of bentonite. The preliminary study on the bentonite stability in the groundwater influenced by cementitious material

    International Nuclear Information System (INIS)

    In the geological disposal concept of radioactive wastes, a kind of clay with sorption ability and low permeability, called bentonite, is envisaged as an engineered barrier system in the geological repository. Also, the cementitious material is envisaged as the backfill material in the vaults and the structure material of the vaults. The groundwater in contact with the cementitious material will promote hyperalkaline conditions in the repository environment and these conditions will affect the performance of the bentonite. Therefore, it is necessary to investigate the interaction between the cementitious material and the bentonite for the evaluation of long term stability of the disposal system. In this study, for the identification and the investigation of the secondary minerals, the batch immersion experiments of the powder bentonite were carried out using synthetic cement leachates (pH=7, 12.5, 14) at 200degC. As the results, it was confirmed that Na as exchangeable cations in the bentonite can exchange relatively easily with Ca in the solution from the experiment results. And the ratio of cation exchange was estimated to be about 25% based on the amount of exchangeable cations Ca2+ between layers. Furthermore, it was concretely shown that the generation of analcime might be affected by the Na concentration from results of the solution analyses and a stability analysis of analcime using the chemical equilibrium model, in addition to the pH in the solution. (author)

  5. 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

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

    OpenAIRE

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

    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 undergro...

  7. Nanocomposites of PP and bentonite clay modified with different surfactants

    International Nuclear Information System (INIS)

    The aim of this work was the development of nano composites of polypropylene (PP) and national bentonite clay modified with different surfactants. The results of X-Ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) showed that the organophilization process was effective. The surfactants led to a significant increase in the basal spacing of Brasgel PA clay. XRD results of the mixture PP/Brasgel PA clay modified with Praepagem WB surfactant indicated that a nanocomposite with intercalated structure was formed. When the Brasgel PA clay was modified with Praepagem HY surfactant, DRX results indicated that a micro composite was formed. Screw speed, clay content and PP viscosity had no influence on the XRD pattern of the obtained materials. (author)

  8. Sorption behaviour of caesium on a bentonite sample

    International Nuclear Information System (INIS)

    Sorption of elements like Cs on clay is one of the principal processes delaying their release from deep repositories of nuclear wastes into the environment. The sorption processes taking place between non-purified natural clay material (bentonite) and synthetic groundwater (containing Ca, Mg, Na, K and carbonates) were therefore studied experimentally and modelled for Cs to determine whether thermodynamic computer codes capable of predicting the behaviour of this element in natural systems might be developed. The model used, based on the properties of a pure montmorillonite phase, incorporates the surface reactions for natural major ions and sorbing cations but does not have any adjustable parameters. The weight of each parameters used in the model is assessed. Surface reactions are classified as either major or minor, and a simplified model of Cs sorption that considers only the major processes is proposed. This simplified model might correspond to the less sophisticated thermodynamic model included in coupled geochemistry-transport models. (orig.)

  9. Sorption behaviour of caesium on a bentonite sample

    Energy Technology Data Exchange (ETDEWEB)

    Hurel, C. [Lab. de Chimie Analytique Bio-Inorganique et Environnement, UMR CNRS 5034, Univ. de Pau et des Pays de l' Adour, Helioparc Pau Pyrenees, Pau (France); GRECI, Univ. de Reims Champagne-Ardenne, Moulin de la Housse, Reims (France); Marmier, N.; Fromage, F. [GRECI, Univ. de Reims Champagne-Ardenne, Moulin de la Housse, Reims (France); Seby, F.; Bourg, A.C.M. [Lab. de Chimie Analytique Bio-Inorganique et Environnement, UMR CNRS 5034, Univ. de Pau et des Pays de l' Adour, Helioparc Pau Pyrenees, Pau (France); Giffaut, E. [ANDRA, Agence Nationale pour la Gestion des Dechets Radioactifs, Chatenay-Malabry (France)

    2002-07-01

    Sorption of elements like Cs on clay is one of the principal processes delaying their release from deep repositories of nuclear wastes into the environment. The sorption processes taking place between non-purified natural clay material (bentonite) and synthetic groundwater (containing Ca, Mg, Na, K and carbonates) were therefore studied experimentally and modelled for Cs to determine whether thermodynamic computer codes capable of predicting the behaviour of this element in natural systems might be developed. The model used, based on the properties of a pure montmorillonite phase, incorporates the surface reactions for natural major ions and sorbing cations but does not have any adjustable parameters. The weight of each parameters used in the model is assessed. Surface reactions are classified as either major or minor, and a simplified model of Cs sorption that considers only the major processes is proposed. This simplified model might correspond to the less sophisticated thermodynamic model included in coupled geochemistry-transport models. (orig.)

  10. Backfilling of deposition tunnels: Use of bentonite pellets

    International Nuclear Information System (INIS)

    The state of knowledge related to use of bentonite pellets as part of backfill or other gap filling components in repository applications is reviewed. How the pellets interact with adjacent sealing materials and the surrounding rock mass is a critical aspect in determining backfill behaviour. The key features and processes that determine how the pellet component of the KBS-3V deposition tunnel backfill will behave are discussed and recommendations related to what additional information needs to be developed are provided. Experiences related to pellet material composition, size, shape, placement options and more importantly, the density to which they can be placed all indicate that there are significant limitations to the achievable as-placed density of bentonite pellet fill. Low as-placed density of the pellet fill component of the backfill is potentially problematic as the outermost regions of tunnel backfill will be the first region of the backfill to be contacted by water entering the tunnels. It is also through this region that initial water movement along the length of the deposition tunnels will occur. This will greatly influence the operations in a tunnel, especially with respect to situations where water is exiting the downstream face of still open deposition tunnels. Pellet-filled regions are also sensitive to groundwater salinity, susceptible to development of piping features and subsequent mechanical erosion by through flowing water, particularly in the period preceding deposition tunnel closure. A review of the experiences of various organisations considering use of bentonite-pellet materials as part of buffer or backfill barriers is provided in this document. From this information, potential options and limitations to use of pellets or pellet-granule mixtures in backfill are identified. Of particular importance is identification of the apparent upper-limits of dry density to which such materials can to be placed in the field. These bounds will

  11. Effect of freezing and thawing on compacted bentonite buffer performance

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. Over the time scale of the lifecycle of the spent nuclear fuel repository at Olkiluoto, local conditions involving both permafrost and glacial climactic phases, possibly repeatedly, cannot be excluded. Permafrost typically occurs when cold and dry climate conditions prevail with no ice-sheet formation or during glaciation as sub-glacial permafrost. Permafrost is generally defined as ground (soil or rock) that remains at or below 0 deg. C for at least two consecutive years. The growth and development of permafrost to some depth of the geologic subsurface depends on a complex heat exchange process across the atmosphere/ground interface and on the geothermal heat flow. Due to the potential impact on hydraulic, mechanical, and chemical subsurface properties and conditions, permafrost penetration is of interest for the performance and safety assessment of a deep, geologic repository. Deleterious effects on porous soil material, resulting from freezing and thawing, are generally ascribed to the occurrence of ice formation. Of course exposure to permafrost does not necessarily imply the presence of ice in the affected material. Indeed the primary consequence of the confinement of water in small pores is a depression to lower temperature of the melting transition. However, when ice forms in porous material, there is a corresponding increase in volume and/or pressure depending on the particular confining stresses at hand and the permeability to water migration. If ice is not formed in the fully saturated buffer system, no increase in volume and/or pressure need be considered. If, on the other hand, ice does form, increased stress from the buffer on the canister and host rock will need to be taken into account. In order to evaluate the effect of freezing and thawing on compacted bentonite buffer performance a series of experiments were conducted using constant-volume swelling pressure cells as follows: - Pre- and post

  12. Hydrothermal stability of bentonite-based buffer materials

    International Nuclear Information System (INIS)

    The reactions expected in bentonite-based buffer materials under conditions typical of a nuclear fuel waste disposal include mineral transformations (e.g. smectite to illite; smectite to zeolite) and a range of low-temperature cementation reactions. The probable extent and significance of these reactions are reviewed, and other reactions involving proposed filler sands are also examined briefly. The effects of mineral transformations on buffer performance will be insignificant if disposal vault temperatures do not exceed 100-120 degrees C and pH remains in the range 4 to 8. At pH > 9, zeolitization and silica dissolution may occur and buffer stability cannot be assured. The effects of cementation reactions may be significant, but are difficult to predict and require further investigation

  13. Properties of zeolite a synthesized by natural bentonite

    International Nuclear Information System (INIS)

    Synthetic zeolite was prepared by using of natural bentonite from Kampo area and the application of detergent builder was investigated. The optimum synthetic condition was SiO2/Al2O3 = 2, Na2O/Al2O3 = 1, H2O/Al2O3 30 at 90 deg C for 3 hr and it was found by XRD analysis that the zeolite synthesized under this condition was type A. When the zeolite A synthesized under the optimum condition was contacted with 40 deg Dh CaCl2 solution at 30 deg C for 15 min, the cation exchange capacity was 264.9 mg CaO/g-zeolite. And the whiteness of the sample was 89% and the mean particle size was 9.95μm. (author)

  14. Behaviour of bentonite/montmorillonite gel at low ionic strength

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. In the Swedish KBS-3 concept for a geological deep storage of spent nuclear fuel, bentonite of high montmorillonite content is proposed to serve as a buffer surrounding copper canisters containing the spent fuel. Montmorillonite has an exceptional affinity for water which results in the build-up of a swelling pressure when bentonite is placed in a confined volume. There may be fractures intersecting the deposition hole and at those fractures the bentonite is not restricted but can continue to swell until a steady state is reached. Under present day Swedish groundwater conditions the swelling into fractures will be limited because the montmorillonite at the swelling front will coagulate. However, at the end of a glaciation one cannot exclude that glacial meltwater of low ionic strength will permeate the bedrock. This could cause erosion of the bentonite, due to colloidal sol formation at the swelling front. A homo-ionic Ca-montmorillonite would not pose any problem because it has limited swelling due to attraction forces caused by ion correlations. In homo-ionic Na-montmorillonite, on the other hand, the correlation interactions are weak and cannot prevent the sol formation in case the montmorillonite is contacted with water of low ionic strength. Under repository conditions the montmorillonite is not homo-ionic, but contains a variety of counterions, both mono- and divalent. It was demonstrated earlier that for mixed Ca/Na-montmorillonite the sol-formation ability is much more sensitive to the ionic strength of the electrolyte than homo-ionic Na-montmorillonite. In deionized water sol formation occurs unless the equivalent charge fraction of Ca2+ is 90% or higher. However in electrolyte solution it was found that the sol is unstable if the ionic strength is above 4 mM. The investigated cases indicate that this condition holds even if the charge fraction of Ca2+ in the interlayer is as low as 20%. In this work it is

  15. Characterization of Unye bentonite after treatment with sulfuric acid

    Directory of Open Access Journals (Sweden)

    Bulent Caglar

    2013-01-01

    Full Text Available Unye bentonite was found to consist predominantly of a dioctahedral smectite along with quartz, tridymite, cristobalite, and minor fractions of feldspar and anatase. A considerable amount of Al was retained as a constituent in acid-resistant impurities following the decomposition of the montmorillonite via acid treatment at an acid/clay ratio of 0.4. These impurities were mesoporous with a maximum surface area of 303.9±0.4 m² g-1. A sharp decrease in the d001 lattice spacing of the montmorillonite to 15.33 Å reflected the reduction of the crystallinity in the activated products. In addition, the increase in the ease with which newly formed hydroxyl groups were lost paralleled the severity of the acid treatment.

  16. Backfilling of deposition tunnels: Use of bentonite pellets

    Energy Technology Data Exchange (ETDEWEB)

    Dixon, David (Atomic Energy of Canada Limited (Canada)); Sanden, Torbjoern (Clay Technology AB (Sweden)); Jonsson, Esther (Swedish Nuclear Fuel and Waste Mangaement Co. (Sweden)); Hansen, Johanna (Posiva Oy (Finland))

    2011-02-15

    The state of knowledge related to use of bentonite pellets as part of backfill or other gap filling components in repository applications is reviewed. How the pellets interact with adjacent sealing materials and the surrounding rock mass is a critical aspect in determining backfill behaviour. The key features and processes that determine how the pellet component of the KBS-3V deposition tunnel backfill will behave are discussed and recommendations related to what additional information needs to be developed are provided. Experiences related to pellet material composition, size, shape, placement options and more importantly, the density to which they can be placed all indicate that there are significant limitations to the achievable as-placed density of bentonite pellet fill. Low as-placed density of the pellet fill component of the backfill is potentially problematic as the outermost regions of tunnel backfill will be the first region of the backfill to be contacted by water entering the tunnels. It is also through this region that initial water movement along the length of the deposition tunnels will occur. This will greatly influence the operations in a tunnel, especially with respect to situations where water is exiting the downstream face of still open deposition tunnels. Pellet-filled regions are also sensitive to groundwater salinity, susceptible to development of piping features and subsequent mechanical erosion by through flowing water, particularly in the period preceding deposition tunnel closure. A review of the experiences of various organisations considering use of bentonite-pellet materials as part of buffer or backfill barriers is provided in this document. From this information, potential options and limitations to use of pellets or pellet-granule mixtures in backfill are identified. Of particular importance is identification of the apparent upper-limits of dry density to which such materials can to be placed in the field. These bounds will

  17. Preparation and characterization of bentonite clay for formation of nanocomposites

    International Nuclear Information System (INIS)

    This study we used the linear medium density polyethylene (PELMD) as polymer matrix and introduced, as reinforcement to increase the mechanical and thermal properties, the green bentonite deposit of Boa Vista/PB, rich montmorillonite (MMT), previously characterized by XRD, that passed by three stages of purification. The first stage was to clean by washing and filtering for removal of coarse material (sand and organic matter), followed by an acid attack. In the second, we used the quaternary ammonium surfactant, in order to increase the distance between the layers of MMT, and the third was removed from the wastewater, using absolute ethanol, finishing the purification of process. Then, the clay was introduced into the polymer matrix by polymerization in solution by intercalation and characterized by XRD. The results showed a partial exfoliation, satisfying the increasing properties. (author)

  18. Evaluation of impact strength of polyamide 6/bentonite clay nanocomposites

    International Nuclear Information System (INIS)

    Nanocomposites of polymer/clay have had much attention in recent years, particularly those developed with layered silicates due to the need of engineering materials more efficient than pure polymers for certain applications. The level of exfoliation of layered silicates in crystalline structure of polymer matrices has been studied and has been observed that they affect the crystalline behavior and the physical and mechanical properties. In this study, nanocomposites of polyamide 6 were obtained by the melt intercalation method, using a regional bentonite modified with a quaternary ammonium salt in an amount of 3% by weight. XRD results showed that incorporation of salt among the layers of clay, making it organophilic and obtaining exfoliated and/or partially exfoliated structures. The impact properties of the nanocomposites showed inferior in relation to pure polyamide, in other words, lost of toughness. (author)

  19. Decontamination effectiveness of bentonite in pigs and sheep repeatedly contaminated with radiocesium

    International Nuclear Information System (INIS)

    The investigations were conducted on 10 pigs and 10 sheep contaminated daily for 21 days with 137CsCl and fed twice a day a normal diet or the same diet supplemented with 10% of bentonite. The animals were killed at days 7, 14 and 21 of radiocesium administration and after cessation of the administration. The abomasum, liver, kidneys, lung, spleen, brain, heart, muscles, tongue and skin were sampled for radiometric determinations. The animals fed a bentonite-supplemented diet revealed substantially lower contents of Cs-137 as compared to the controls. The radioactivities of pig and sheep organs after 21 d Cs-137 administration were lower by about 67.5 and 81.3%, respectively, compared to the controls. The cessation of Cs-137 administration decreased organ radioactivities in bentonite-fed sheep and pigs by about 74.5 and 64.1%, respectively, compared to those in animals without bentonite. (author). 12 refs, 2 tabs

  20. EVALUATION OF THE BENTONITE CONTENT IN SPENT FOUNDRY SANDS AS A FUNCTION OF HYDRAULIC CONDUCTIVITY COEFFICIENT

    Directory of Open Access Journals (Sweden)

    Schirlene Chegatti

    2013-06-01

    Full Text Available This study evaluates the relationship of the bentonite content and hydraulic conductivity coefficient (k of waste foundry sands in tests of hydraulic conductivity in a flexible wall permeameter. The test samples had concentrations of activated sodium bentonite and natural sodium bentonite between 4% and 15%. It was also analyzed chemically the liquid leachate (aluminum, barium, chromium, cadmium, lead, phenols, iron, fluoride, and manganese, following de standard tests of Standard Methods 3111 B e D for the determination of this components in liquid samples. The experiments were supplemented with cation exchange capacity analysis. The results indicate that the values of are is related to the content of bentonite in waste foundry sand and the percolation from this waste disposal.

  1. Swelling and hydraulic properties of Ca-bentonite for the buffer of a waste repository

    International Nuclear Information System (INIS)

    Swelling and hydraulic tests were carried out to provide the information for the selection of buffer material in a radioactive waste repository. Ca-bentonite and de-ionized water were used for the tests. The swelling pressures of compacted bentonite were in the wide range of 0.7 Kg/cm2 to 190.2 Kg/cm2, and they largely increased with an increase in the dry density and bentonite content. However, the swelling pressures decreased with increasing the initial water content and beyond about 12 wt.% of the initial water content, leveled off to a nearly constant value. The hydraulic conductivities were lower than 10-11 m/s for the compacted bentonite with the dry density higher than 1.4 Mg/m3. They increased with increasing temperature in the range of 20 deg. C to 150 deg. C. (author)

  2. Practical and theoretical basis for performing redox-measurements in compacted bentonite. A literature survey

    International Nuclear Information System (INIS)

    This report reviews the state-of-the-art with regard to redox measurements, especially in compacted water saturated bentonite, but also in natural systems like sediments and ground waters. Both theoretical and practical aspects of redox measurements are discussed, as well as some basic concepts like terminal electron-accepting processes (TEAPs) and oxidative capacity (OXC). The problems associated with the interpretation of measured electrode potentials are treated. Despite many practical and theoretical difficulties, redox measurements continue to be carried out by researchers all over the world. The over-all conclusion from the literature survey is that fruitful redox-measurements can be performed in compacted bentonite. Irrespective of whether the measured redox potentials are absolute or not, the use of electrodes provide a valuable tool for studying, e.g., long-term changes in the pore water of compacted bentonite and/or the diffusion of oxygen into a bentonite. (orig.)

  3. Temperature effects on geotechnical and hydraulic properties of bentonite hydrated with inorganic salt solutions

    DEFF Research Database (Denmark)

    Rashid, H. M. A.; Kawamoto, K.; Saito, T.;

    2015-01-01

    © 2015, International Journal of GEOMATE. This study investigated the combined effect of temperature and single-species salt solutions on geotechnical properties (swell index and liquid limit) and hydraulic conductivity of bentonite applying different cation types, concentrations, and temperatures...

  4. RECEIVING FUNCTIONAL FEED ADDITIVE ON THE BASIS OF BENTONITE CLAYS AND CAROTENE CONTAINING RAW MATERIALS

    Directory of Open Access Journals (Sweden)

    Zholobova I. S.

    2014-02-01

    Full Text Available In this article we have shown the results of studying of biologically active connections in bentonite clays, carotene containing raw materials for the purpose of receiving functional feed additive for agricultural birds

  5. Hydraulic permeability of bentonite-polymer composites for application in landfill technology

    Science.gov (United States)

    Dehn, Hanna; Haase, Hanna; Schanz, Tom

    2015-04-01

    Bentonites are often used as barrier materials in landfill technology to prevent infiltration of leachates to the natural environment. Since decades, geoenvironmental engineering aims at improving the hydro-mechanical performance of landfill liners. Various studies on the permeability performance of geosynthetic clay liners (GCLs) show effects of non-standard liquids on behaviour of Na+-bentonite regarding its sealing capacity. With increasing concentration of chemical aggressive solutions the sealing capacity decreases (Shackelford et al. 2000). An opportunity to improve the hydraulic permeability of the bentonites is the addition of polymers. The changes in hydraulic permeability performance of polymer treated and untreated bentonites while adding chemical aggressive solutions were studied by several authors. Results obtained by Scalia et al. (2014) illustrate that an increase in permeability can be prevented by adding polymer to Na+-bentonite. On the other hand, Ashmawy et al. (2002) presented results on the incapability of several commercial bentonite-polymer-products. The objective of this study is to characterize the influence of polymer addition on hydraulic performance of Na+-bentonite systematically. Therefore, the influence of 1% polymer addition of cationic and anionic polyacrylamide on the swelling pressure and hydraulic permeability of MX 80 bentonite was investigated. Preparation of bentonite-polymer composites was conducted (1) in dry conditions and (2) using solution-intercalation method. Experiments on hydraulic permeability were carried out using distilled water as well as CaCl2-solution. References Ashmawy, A. K., El-Hajji, D., Sotelo, N. & Muhammad, N. (2002), `Hydraulic Performance of Untreated and Polymer-treated Bentonite in Inorganic Landfill Leachates', Clays and Clay Minerals 50(5), 546-552. Scalia, J., Benson, C., Bohnhoff, G., Edil, T. & Shackelford, C. (2014), 'Long-Term Hydraulic Conductivity of a Bentonite-Polymer Composite Permeated

  6. An Evaluation of Models of Bentonite Pore Water Evolution

    International Nuclear Information System (INIS)

    The determination of a bentonite pore water composition and understanding its evolution of with time underpins many radioactive waste disposal issues, such as buffer erosion, canister corrosion, and radionuclide solubility, sorption, and diffusion, inter alia. The usual approach to modelling clay pore fluids is based primarily around assumed chemical equilibrium between Na+, K+, Ca2+, and Mg2+ aqueous species and ion exchange sites on montmorillonite, but also includes protonation- deprotonation of clay edge surface sites, and dissolution-precipitation of the trace mineral constituents, calcite and gypsum. An essential feature of this modelling approach is that clay hydrolysis reactions (i.e. dissolution of the aluminosilicate octahedral and tetrahedral sheets of montmorillonite) are ignored. A consequence of the omission of clay hydrolysis reactions from bentonite pore fluid models is that montmorillonite is preserved indefinitely in the near-field system, even over million-year timescales. Here, we investigate the applicability of an alternative clay pore fluid model, one that incorporates clay hydrolysis reactions as an integral component and test it against well-characterised laboratory experimental data, where key geochemical parameters, Eh and pH, have been measured directly in compacted bentonite. Simulations have been conducted using a range of computer codes to test the applicability of this alternative model. Thermodynamic data for MX-80 smectite used in the calculations were estimated using two different methods. Simulations of 'end-point' pH measurements in batch bentonite-water slurry experiments showed different pH values according to the complexity of the system studied. The most complete system investigated revealed pH values were a strong function of partial pressure of carbon dioxide, with pH increasing with decreasing PCO2 (log PCO2 values ranging from -3.5 to -7.5 bars produced pH values ranging from 7.9 to 9.6). A second set of calculations

  7. Highly compacted bentonite: a self-healing substance for nuclear waste isolation

    International Nuclear Information System (INIS)

    Granular Na bentonite acquires considerable microstructural homogeneity through water and particle redistribution processes. This yields a very low permeability and thus excellent barrier functions in repositories. This self-healing property also means that large bentonite volumes tend to reach a homogeneous condition. Thus, local voids or inhomogeneities produced, for instance, by minor displacement of the surrounding rock will be healed. The swelling potential also means that a perfect contact is established between the clay barrier and the rock

  8. Removal of formaldehyde from aqueous solution by adsorption on kaolin and bentonite: a comparative study

    OpenAIRE

    Salman, Muhammad; Athar, Makshoof; SHAFIQUE, Umer; Rehman, Rabia

    2012-01-01

    The adsorption of formaldehyde on bentonite and kaolin was studied in batch mode. Parameters like adsorbent dose, pH, contact time and agitation speed were investigated. Langmuir, Freundlich and Temkin isotherms were employed for describing adsorption equilibrium. The maximum amounts of formaldehyde adsorbed (qmax), as evaluated by Langmuir isotherm, were 3.41 and 5.03 milligrams per gram of ground kaolin and bentonite, respectively. The study results led to the conclusion that kaol...

  9. An investigation on physical properties of polyethylene composite with bentonite, kaolin and calcium carbonate additives

    OpenAIRE

    Karabeyoğlu, Sencer S.; , Nurşen Öntürk

    2014-01-01

    Bentonite, Kaolin, Calcium carbonate easily obtained in nature as mineral products are widely used in plastics industry for additive materials. In this study, Bentonite, Kaolin, and Calcium carbonate minerals were compounded with polyethylene matrix used in specific rates. Prepared compounds melted in sheet metal molds and cooled down under appropriate conditions. Thus, production of composite material was achieved. Hardness, water absorption, and physical properties of manufactured composite...

  10. Surface Modification of Bentonites. II. Modification of Montmorillonite with Cationic Poly(ethylene oxides)

    OpenAIRE

    Dau, Jörn; Lagaly, Gerhard

    1998-01-01

    Surface modification of clay minerals has become increasingly important for optimizing the practical application of bentonites, kaolins, and clays. We describe the reaction of montmorillonite, an important mineral in bentonites, with cationic poly(ethylene oxides). Poly(ethylene oxides), PEOs, with molecular masses between 1550 and 35000, were modified by substituting the OH end groups by bromine, then replacing Br by trimethylammonium (TMA) groups. Mono-endcapped PEOs were prepared from poly...

  11. Adsorption of and acidic dye from aqueous solution by surfactant modified bentonite

    International Nuclear Information System (INIS)

    The aim of this paper is to study the adsorption of an acidic dye S. Y. 4 GL (i.e: Supranol yellow 4GL) from aqueous solution on inorgano-organo clay. Bentonite is a kind of natural clay with good exchanging ability. By exchanging its inter lamellar cations with Cetyltrimethylammonium bromide (CTAB) and hydroxy aluminic or chromium poly cations, the properties of natural bentonite can be greatly improved. (Author)

  12. Research program to study the gamma radiation effects in Spanish bentonites

    International Nuclear Information System (INIS)

    The engineering barrier of a radioactive waste underground disposal facility, placed in a granitic host rock, will consist of a backfill of compacted bentonite blocks. At first, this material will be subjected to a gamma radiation field, from the waste canister, and heat from the spent fuel inside the canister. Moreover, any groundwater that reaches the repository will saturate the bentonite. For these reasons the performance of the engineered barrier must be carefully assessed in laboratory experiments. (Author)

  13. The effect of pore structural factors on diffusion in compacted sodium bentonite

    International Nuclear Information System (INIS)

    Four kinds of diffusion experiments; (1) through-diffusion (T-D) experiments for diffusion direction dependency to compacted direction, (2) in-diffusion (I-D) experiments for composition dependency of silica sand in bentonite, (3) I-D experiments for initial bentonite grain size dependency, and (4) I-D experiments for the effect of a single fracture developed in bentonite, were carried out using tritiated water (HTO) to evaluate the effect of pore structural factors on diffusion. For (1), effective diffusivities (De) in Na-bentonites, Kunigel-V1 and Kunipia-F, were measured for densities of 1.0 and 1.5 Mg.m-3 in the axial and perpendicular directions to compacted one. Although De values in Kunigel-V1 for both directions were similar over the density, De values for perpendicular direction to compacted one in Kunipia-F were higher than those for the same direction as compacted one. For (2), apparent diffusivities (Da) in Kunigel-V1 with silica sand were measured for densities of 0.8 to 1.8 Mg.m-3. No significant effect of the mixture of silica sand was found. For (3), Da values for densities of 0.8 to 1.8 Mg.m-3 were measured for a granulated Na-bentonite, OT-9607. However, no effect of initial bentonite grain size was found. For (4), Da values in Kunigel-V1, in which a single fracture was artificially reproduced and immersed in distilled water, were measured. No effect of the fracture on Da was found. Based on this, it may be said that the composition of smectite in bentonite affects the orientation property of clay particle and also affects diffusion. Furthermore, a penetrated fracture formed in bentonite is restored for a short while and does not affect diffusion. Copyright (2001) Material Research Society

  14. Chitosan/bentonite bionanocomposites: morphology and mechanical behavior; Bionanocompositos quitosana/bentonita: morfologia e comportamento mecanico

    Energy Technology Data Exchange (ETDEWEB)

    Braga, C.R.C.; Melo, F.M.A. de [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Programa de Pos-graduacao em Ciencia e Engenharia de Materiais; Vitorino, I.F. [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Dept. de Ciencia e Engenharia de Materiais; Fook, M.V.L.; Silva, S.M.L., E-mail: suedina@dema.ufcg.edu.b [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Unidade Academica de Engenharia de Materiais

    2010-07-01

    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. Investigation of Co(II) sorption on GMZ bentonite from aqueous solutions by batch experiments

    International Nuclear Information System (INIS)

    In this study, a local bentonite from Gaomiaozi county (Inner Mongolia, China) was converted to Na-bentonite and was characterized by FTIR and XRD to determine its chemical constituents and micro-structure. The removal of cobalt from aqueous solutions by Na-bentonite was investigated as a function of contact time, pH, ionic strength, foreign ions and temperature by batch technique under ambient conditions. The results indicated that the sorption of Co(II) was strongly dependent on pH. At low pH, the sorption of Co(II) was dominated by outer-sphere surface complexation or ion exchange whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The Langmuir, Freundlich, and D-R models were used to simulate the sorption isotherms of Co(II) at the temperatures of 293.15, 313.15 and 333.15 K, respectively. The thermodynamic parameters (ΔG0, ΔS0, ΔH0) of Co(II) sorption on GMZ bentonite calculated from the temperature-dependent sorption isotherms indicated that the sorption of Co(II) on GMZ bentonite was an exothermic and spontaneous process. The Na-bentonite is a suitable material for the preconcentration and solidification of Co(II) from aqueous solutions. (author)

  16. Study of combined effect of proteins and bentonite fining on the wine aroma loss.

    Science.gov (United States)

    Vincenzi, Simone; Panighel, Annarita; Gazzola, Diana; Flamini, Riccardo; Curioni, Andrea

    2015-03-01

    The wine aroma loss as a consequence of treatments with bentonite is due to the occurrence of multiple interaction mechanisms. In addition to a direct effect of bentonite, the removal of aroma compounds bound to protein components adsorbed by the clay has been hypothesized but never demonstrated. We studied the effect of bentonite addition on total wine aroma compounds (extracted from Moscato wine) in a model solution in the absence and presence of total and purified (thaumatin-like proteins and chitinase) wine proteins. The results showed that in general bentonite alone has a low effect on the loss of terpenes but removed ethyl esters and fatty acids. The presence of wine proteins in the solution treated with bentonite tended to increase the loss of esters with the longest carbon chains (from ethyl octanoate to ethyl decanoate), and this was significant when the purified proteins were used. The results here reported suggest that hydrophobicity can be one of the driving forces involved in the interaction of aromas with both bentonite and proteins. PMID:25665100

  17. Adsorption of dye from wastewater using chitosan-CTAB modified bentonites.

    Science.gov (United States)

    Guo, Jianzhong; Chen, Shunwei; Liu, Li; Li, Bing; Yang, Ping; Zhang, Lijun; Feng, Yanlong

    2012-09-15

    Dyeing wastewater removal is important for the water treatment, and adsorption is an efficient treatment process. In this study, three modified bentonites, chitosan modified bentonite (CTS-Bent), hexadecyl trimethyl ammonium bromide (CTAB) modified bentonite (CTAB-Bent), and both chitosan and hexadecyl trimethyl ammonium bromide modified bentonite (CTS-CTAB-Bent) were prepared and characterized by FTIR and XRD analysis. Batch experiments were conducted to evaluate the adsorptive removal of weak acid scarlet from aqueous phase using modified bentonites under different conditions. The results show that the adsorption capacity of weak acid scarlet onto natural bentonite was low (4.9%), but higher for 1CTS-Bent and 1CTS-10CTAB-Bent. The optimal conditions for weak acid scarlet adsorption were 1% chitosan, 10% CTAB, at 80°C and reaction time 2.5h. The best removal efficiency was ∼85%, and the adsorption capacity of weak acid scarlet was around 102.0mg g(-1), much higher than that of commercial activated carbon (27.2mg g(-1)). These results suggest that 1CTS-10CTAB-Bent is an excellent adsorbent for effective weak acid scarlet removal from water. The adsorption isotherms of weak acid scarlet were investigated. It was found that Langmuir and Temkin models fitted the data very well (R(2)>0.99). PMID:22738850

  18. Monitoring of bentonite pore water with a probe based on solid-state microsensors

    International Nuclear Information System (INIS)

    Repositories for the disposal of radioactive waste generally rely on a multi-barrier system to isolate the waste from the biosphere. This multi-barrier system typically comprises Natural geological barrier provided by the repository host rock and its surroundings and an engineered barrier system (EBS). Bentonite is being studied as an appropriated porous material for an EBS to prevent or delay the release and transport of radionuclides towards biosphere. The study of pore water chemistry within bentonite barriers will permit to understand the transport phenomena of radionuclides and obtain a database of the bentonite-water interaction processes. In this work, the measurement of some chemical parameters in bentonite pore water using solid-state microsensors is proposed. Those sensors are well suited for this application since in situ measurements are feasible and they are robust enough for the long periods of time that monitoring is needed in an EBS. A probe containing an ISFET (ion sensitive field effect transistor) for measuring pH, and platinum microelectrodes for measuring conductivity and redox potential was developed, together with the required instrumentation, to study the chemical changes in a test cell with compacted bentonite. Response features of the sensors' probe and instrumentation performance in synthetic samples with compositions similar to those present in bentonite barriers are reported. Measurements of sensors stability in a test cell are also presented

  19. EFFECT OF BENTONITE ON SKIN WOUND HEALING: EXPERIMENTAL STUDY IN THE RAT MODEL

    Directory of Open Access Journals (Sweden)

    S. H. Emami-Razavi

    2006-08-01

    Full Text Available Wound healing in the skin depends upon the availability of appropriate trace metals as enzyme cofactors and structural components in tissue repair. The present study is a part of a series of experimental investigations to examine the influence of Bentonite on skin wound healing. Surgically induced skin wounds in 48 young adult male rats were exposed topically to Bentonite (12 round wound and 12 incisional wound and control wounds (12 round wound and 12 incisional wound received de-ionized water only. Skin wounds (round and incisional treated with Bentonite exhibited no significant difference in margins with erythema and edematous changes. Scab and wound debris was more extensive and persisted for at least 7 days after surgery in control group (P < 0.05. Skin wounds exposed to Bentonite exhibited a mild retarded re-epithelialization, the treatment wounds were characterized by a prominent central mass of inflammatory cells, cell debris and wound exudate. The intense infiltrate of lymphocytes, macrophages, monocytes and fibroblasts extended from the wound margin into the region of the panniculus carnosus muscle and hypodermis. Vascular dilatation and dermal oedema were prominent features of these wounds. External utilization of Bentonite for wound healing is safe and feasible, and we finalized that macroscopic healing of wound that treated by Bentonite was superior versus control group.

  20. Anti-fouling effect of bentonite suspension in ultrafiltration of oil/water emulsion.

    Science.gov (United States)

    Panpanit, S; Visvanathan, C; Muttamara, S

    2002-03-01

    The effect on membrane fouling resistance during ultrafilration of oil/water emulsion with the presence of bentonite suspension is experimentally evaluated. The fouling resistance was analyzed as a function of different membrane types and bentonite concentration. The total membrane fouling was categorized into reversible and irreversible, by adopting an appropriate chemical cleaning technique. The results revealed a 40% flux augmentation with the increase of bentonite concentration up to an optimum value of 300 mg l(-1) for cellulose acetate membrane. Further increase of bentonite concentration led to particle deposition on the membrane surface and reduced the flux. The polysulfone membrane did not show a similar flux improvement. This could be due to its high hydrophobicity. The absorption of oil/water emulsion on bentonite increased TOC removal rate from 65% to 80%, and this effect was the major cause of reduction in gel layer formation on the membrane surface. The extent of irreversible fouling of the hydrophilic cellulose acetate membrane was much smaller than that of the polysulfone membrane. These experiments demonstrated that, presence of bentonite could induce transformation of irreversible fouling caused by oil emulsion to reversible fouling, which could be periodically chemically cleaned. PMID:11999987

  1. The influence of the addition of polymers on the physico-chemical properties of bentonite suspensions

    Directory of Open Access Journals (Sweden)

    Stojiljkovic S.

    2014-01-01

    Full Text Available Bentonite clays have many applications in industries ranging from construction to cosmetics. Addition of polymers can profoundly influence the properties of bentonite suspensions and we now describe the influence of a range of different polymers. Whereas polyvinyl pyrolidone and soy isolate only slightly influenced the pH and the electrical conductivity of bentonite polymers in suspension, Carbopol solution caused decreases in both pH and electrical conductivity. As expected, strong electrolytes like sodium chloride caused big changes in the electrical conductivity of the suspensions. When the temperature of the bentonite suspensions was increased, the pH was almost unchanged, but the electrical conductivity increased. Bentonite treated with polymer suspensions can be used in purifying polluted water; for example, our results suggest that high pH caused by phosphorous salts can be addressed using bentonite modified with Carbopol. [Projekat Ministarstva nauke Republike Srbije: Stanisa Stojiljkovic, Vojkan Miljkovic, Goran Nikolic, Ivana Savic and Ivan Savic, TR 34020, Danijela Kostic 172047 and Biljana Arsic 174007

  2. Fundamental study on anisotropy of diffusion and migration pathway in compacted bentonite

    International Nuclear Information System (INIS)

    SEM observations for micropore structure in compacted bentonite and through-diffusion experiments for non-sorptive tritiated water (HTO) were conducted to evaluate the anisotropy of diffusive pathway in compacted bentonite used as a buffer material in the geological disposal of high-level radioactive waste. The SEM observations and thorough-diffusion experiments were conducted for axial and perpendicular directions to the compacted direction of bentonite as a function of bentonite's dry density. Two types of Na-bentonites, Kunigel-V1 and Kunipia-F with different smectite contents were used in both experiments. No orientation of clay particles was found for low-smectite content Kunigel-V1, while layers of clay particles orientated in the perpendicular direction to compacted direction were observed for Kunipia-F with approximately 100 wt% smectite content. This tendency is in good agreement with that for HTO's effective diffusivities obtained from diffusion experiments, indicating that smectite content in bentonite affects the orientation properties of clay particles and diffusive pathway. (author)

  3. [Study on performance of double mineral base liner using modified bentonite as active material].

    Science.gov (United States)

    Qu, Zhi-Hui; Zhao, Yong-Sheng; Wang, Tie-Jun; Ren, He-Jun; Zhou, Rui; Hua, Fei; Wang, Bing; Hou, Yin-Ting; Dai, Yun

    2009-06-15

    The absorbing capacity of clay,roasting bentonites by 450 degrees C and dual-cation organobentonites of the pollutions in landfill leachate was compared through static experiment, and investigations were conducted into availability of controlling the permeating of landfill leachate and feasibility of removing the main pollutants in leachate on the double mineral base liners of clay/roasting bentonites by 450 degrees C and clay/dual-cation organobentonites by using nice landfill leachate as the filter fluid. Experiment indicated that the adsorption equilibrium time of landfill leachate in clay, roasting bentonites by 450 degrees C and dual-cation organobentonites was 24 h; the absorbing capacity of roasting bentonites by 450 degrees C and dual-cation organobentonites was larger than that of clay. Simultaneous the penetration coefficients of the two liners were respective 1.31 x 10(-8) cm x s(-1) and 2.80 x 10(-8) cm x s(-1); Double mineral base liners of clay/roasting bentonites by 450 degrees C owned larger absorbing capacity of NH4+, however, double mineral base liners of clay/dual-cation organobentonites had strong absorbing capacity of organic pollutants and the attenuation rate of COD was 33.82% higher than the other. Conclusion was drawn that different types of modified bentonite should be chosen as "the active layer" according to different styles of landfill pollutants. PMID:19662882

  4. Salt content impact on the unsaturated property of bentonite-sand buffer backfilling materials

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Ming [Key Laboratory of Mechanics on Disaster and Environment in Western China, Lanzhou University, Lanzhou 730000 (China); Zhang Huyuan, E-mail: p1314lvp@yahoo.com.cn [Key Laboratory of Mechanics on Disaster and Environment in Western China, Lanzhou University, Lanzhou 730000 (China); Jia Lingyan; Cui Suli [Key Laboratory of Mechanics on Disaster and Environment in Western China, Lanzhou University, Lanzhou 730000 (China)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer SWCC and infiltration process of bentonite-sand mixtures is researched. Black-Right-Pointing-Pointer The k{sub u} of bentonite-sand mixtures was evaluated as the buffer backfilling materials. Black-Right-Pointing-Pointer Salt content impacting on the unsaturated property of bentonite-sand materials is small. - Abstract: Bentonite mixed with sand is often considered as possible engineered barrier in deep high-level radioactive waste disposal in China. In the present work, the vapor transfer technique and water infiltration apparatus were used to measure the soil water characteristic curve (SWCC) and unsaturated hydraulic conductivity (k{sub u}) of bentonite-sand mixtures (B/S) effected by salt content. Results show, the water-holding capacity and k{sub u} increase slightly with the concentration of Na{sup +} in pore liquid increasing from 0 g/L to 12 g/L, similar with the solution concentration of Beishan groundwater in China. Salt content in the laboratory produced only one order of magnitude increase in k{sub u}, which is the 'safe' value. The different pore liquid concentrations used in this study led to small differences in thickness of diffuse double layer of bentonite in mixtures, this might explain why some differences have been found in final values of k{sub u}.

  5. Influence of Water Salinity on the Hydraulic Conductivity of Compacted Bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Won Jin; Kim, Jin Seop; Choi, Jong Won [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2011-12-15

    The influence of water salinity on the hydraulic conductivities of compacted bentonite with several dry densities were studied. The hydraulic conductivity increases with increasing salinity only when the dry density of bentonite is relatively low. The degree of increase becomes more remarkable at a lower dry density of bentonite. For bentonite with the density of 1.0 Mg/m{sup 3} and 1.2 Mg/m{sup 3}, the hydraulic conductivity of the 0.4 M NaCl solution increases up to about 7 times and 3 times, respectively higher than that of freshwater. However, for the bentonite with a dry density higher than 1.4 Mg/m{sup 3}, the salinity has an insignificant effect on the hydraulic conductivity, and the hydraulic conductivity is nearly constant within the salinity range of 0.04 to 0.4 M NaCl. The pre-saturation of the bentonite specimen with freshwater has no significant influence on the hydraulic conductivity.

  6. Occurrence of Fe–Mg-rich smectites and corrensite in the Morrón de Mateo bentonite deposit (Cabo de Gata region, Spain): A natural analogue of the bentonite barrier in a radwaste repository

    OpenAIRE

    Pelayo Bayón, Marta; García Romero, Emilia; Labajo Rodillana, Miguel A.; Pérez del Villar Guillén, L.

    2011-01-01

    The Morrón de Mateo bentonite deposit is being studied as a natural analogue of the thermal and geochemical effects on a bentonite barrier in a deep geological repository of high level radioactive wastes. This bentonite deposit and its host rocks were intruded by a rhyodacitic volcanic dome that induced a hydrothermal metasomatic process affecting the biocalcarenite beds close to the dome. In this work, the mineralogical and chemical features of the clay minerals of the hydrotherm...

  7. Study of Japanese and Serbia bentonite on the fraction of 137Cs from cement-ion exchange resins-bentonite clay mixture

    International Nuclear Information System (INIS)

    Leaching tests in cement-ion exchange resins-bentonite matrix, were carried out in accordance with a method recommended by IAEA. The cement specimens were prepared from construction cement which is basically a standard Portland cement. The cement was mixed with saturated wet cation exchange resins, (100 g. of dry resins +100 g. of water containing 137Cs) and two bentonite clay, from Serbia, and another from Japan. After each leaching period the radioactivity in the leachant was measured. All results exhibit practically the same general characteristics. An enhanced initial period of leaching occurs during the first 25-30 days or so, followed by a distinct reduction in the leach rate which is broadly maintained up to the long period of leaching. The leach behaviour of cement-mortar materials can be explained as a combination of two processes: surface wash-off, which is not diffusion controlled, followed by a static diffusion stage. Enhanced initial period of leaching can be explained in terms of a rapid equilibrium being established between spaces present in the surface pores of the Portland cement and ions in solution in the leachant; hence the term wash-off. It is the second stage which is controlled by diffusion that dominates the long-term leaching behaviour of the material. We also prove that increasing amount of bentonite causes a significant reduction in the leaching rate, because of bentonite good sorption characteristics and ion selectivity. We showed that the bentonite from Serbia can successfully be used for the immobilisation of radioactive waste with same quality as Japanese bentonite

  8. Effect of pH, ionic strength and fulvic acid on the sorption and desorption of cobalt to bentonite

    International Nuclear Information System (INIS)

    Humic substances and bentonite have attracted great interest in radioactive waste management. Here the sorption of cobalt on bentonite in the presence and absence of fulvic acid (FA) under ambient conditions was studied. The effects of pH, ionic strength, FA and solution concentrations on cobalt sorption to bentonite were also investigated using batch techniques. The results indicate that the sorption of cobalt is strongly dependent on pH and is independent of ionic strength under our experimental conditions. Surface complexation is considered the main mechanism of cobalt sorption to bentonite. In the presence of FA, little effect of FA on cobalt sorption was found at pH8. The addition sequences of FA/Co2+ to the bentonite suspension on the sorption of cobalt to FA-coated bentonite were also studied. The results indicated that the sorption is not influenced by the addition sequences. Some possible mechanisms are discussed

  9. The Optimization of Aniline Adsorption from Aqueous Solutions by Raw Bentonite and Bentonite Modified with Cationic Surfactants Using the Taguchi Model

    Directory of Open Access Journals (Sweden)

    F. Taherkhani

    2015-04-01

    Full Text Available Introduction & Objectives: Aniline is an organic compound widely used in various industries. The release of this compound has had various environmental impacts. Thus, the assessment of efficient and practical methods for the removal of aniline from wastewater of these industries is remarkable. Taguchi model is a model for the analysis of experiments, that predicts both the effects of each factors and the optimum level of them using a certain number of experiment. The purpose of this study was the optimization of aniline adsorption on the raw and modified bentonite with a cationic surfactant using Taguchi model. Materials & Methods: In this experimental study, the raw bentonite and modified bentonite was prepared in a few steps. Then, 4 main factors (i.e. pollutant concentration, contact time, pH, and adsorbent dosage on 4 levels were selected by Matrix L16 trials and the experiments were conducted in this matrix. The factors were also ranked based on the R-value. Then , the data were analyzed with Minitab 17 software. Finally, the adsorption of aniline on raw and modified bentonite was determined in optimal conditions. Results: The optimization of adsorption process using Taguchi model showed that the factors of importance for optimizing respectively were: contact time of 360 minutes, pH =10 pH, ani-line initial concentration of 300 mg/L and adsorbent dosages of 40 g/L. The maximum ad-sorption of aniline onto raw bentonite and modified bentonite with cationic surfactant in op-timal conditions were determined 81.86 and 8.75, respectively. The results revealed that Freundlich isotherm and pseudo-second-order kinetic model provided a better ?t to the ex-perimental data. Conclusion: The results showed that the bentonite modified with cationic surfactant is efficient in the removal of aniline. At the same time, since bentonite is cheap and easily accessible ,it is considered a desirable adsorbant. (Sci J Hamadan Univ Med Sci 2015; 22 (1:55-64

  10. Effect of pH on the formation of disinfection byproducts in swimming pool water--is less THM better?

    Science.gov (United States)

    Hansen, Kamilla M S; Willach, Sarah; Antoniou, Maria G; Mosbæk, Hans; Albrechtsen, Hans-Jørgen; Andersen, Henrik R

    2012-12-01

    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 (NCl(3)), 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 NCl(3) formation increased at decreasing pH whereas the formation of HAAs remained constant. Under our experimental conditions, the formation of NCl(3) (suspected asthma inducing compound) at pH = 6.0 was an order of magnitude higher than at pH = 7.5. Furthermore, the effect of the presence of bromide on DBP 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 responsible for the majority of the toxicity from the measured DBPs in both absence and presence of bromide. PMID:23026126

  11. A comparative simulation study of coupled THM processes and their effect on fractured rock permeability around nuclear waste repositories

    Energy Technology Data Exchange (ETDEWEB)

    Rutqvist, Jonny; Barr, Deborah; Birkholzer, Jens T.; Fujisaki, Kiyoshi; Kolditz, Olf; Liu, Quan-Shen; Fujita, tomoo; Wang, Wenqing; Zhang, Cheng-Yuan

    2008-10-23

    This paper presents an international, multiple-code, simulation study of coupled thermal, hydrological, and mechanical (THM) processes and their effect on permeability and fluid flow in fractured rock around heated underground nuclear waste emplacement drifts. Simulations were conducted considering two types of repository settings: (a) open emplacement drifts in relatively shallow unsaturated volcanic rock, and (b) backfilled emplacement drifts in deeper saturated crystalline rock. The results showed that for the two assumed repository settings, the dominant mechanism of changes in rock permeability was thermal-mechanically-induced closure (reduced aperture) of vertical fractures, caused by thermal stress resulting from repository-wide heating of the rock mass. The magnitude of thermal-mechanically-induced changes in permeability was more substantial in the case of an emplacement drift located in a relatively shallow, low-stress environment where the rock is more compliant, allowing more substantial fracture closure during thermal stressing. However, in both of the assumed repository settings in this study, the thermal-mechanically-induced changes in permeability caused relatively small changes in the flow field, with most changes occurring in the vicinity of the emplacement drifts.

  12. Experimental study on self-healing of bentonite/sand mixtures and its impact on hydraulic permeability

    International Nuclear Information System (INIS)

    The effects of gas permeation on the hydraulic permeability of bentonite/sand mixtures were studied experimentally by conducting permeability tests with various fluids and by microscopic observations. In these tests, hydraulic permeabilities were measured before and after helium gas was applied to permeate the mixtures. Although gas formed preferential migration paths through the mixtures, the imperviousness of the bentonite/sand mixtures to the tested fluids never deteriorated because the paths became filled by swelling bentonite on re-saturation

  13. A meta-analysis of water quality and aquatic macrophyte responses in 18 lakes treated with lanthanum modified bentonite (PHOSLOCK®)

    OpenAIRE

    Spears, Bryan M.; Mackay, Eleanor B.; Yasseri, Said; Gunn, Iain D.M.; Waters, Kate E.; Andrews, Christopher; Cole, Stephanie; de Ville, Mitzi; Kelly, Andrea; Meis, Sebastian; Moore, Alanna L.; Nurnberg, Gertrud K.; van Oosterhout, Frank; Pitt, Jo-Anne; Madgwick, Genevieve

    2015-01-01

    Lanthanum (La) modified bentonite is being increasingly used as a geo-engineering tool for the control of phosphorus (P) release from lake bed sediments to overlying waters. However, little is known about its effectiveness in controlling P across a wide range of lake conditions or of its potential to promote rapid ecological recovery. We combined data from 18 treated lakes to examine the lake population responses in the 24 months following La-bentonite application (range of La-bentonite loads...

  14. Mineral alteration in a 4.5 years concrete-bentonite interface

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. Chemical processes occurring in the concrete-bentonite interface can affect the feasibility of the clay barriers implemented for the isolation of nuclear wastes. During the concrete degradation, highly alkaline waters from the concrete will diffuse through the clay barrier. This may produce geochemical and microstructural transformations in the bentonite. Particularly, the studies carried out with the FEBEX bentonite in contact with concrete showed montmorillonite dissolution, precipitation of zeolites, Mg-smectite, CSH gels and brucite. These studies focused mainly in a highly reactive alteration environment (pH>13). During the NF-PRO integrated project the concrete-compacted bentonite interaction was also studied containing the materials and conditions as close as possible to real ones, with simultaneous heating and hydration. Several experimental cells were designed and mounted at a time in CIEMAT, starting in 2006. Presently, in the context of the PEBS project a long-term cell has been dismounted after 4.5 years. The tests were performed in cells especially designed in CIEMAT for the experiments. Blocks of FEBEX bentonite were compacted with its hygroscopic water content at a dry density of 1.65 g/cm3. At the bottom of the cell, the bentonite block was inserted just in contact with the heater. On top of this, a 30-mm thick concrete block was placed. The hydration occurred through the concrete block. In a few days after the beginning of the test the sensor placed at the concrete/bentonite interface recorded stable relative humidities of 100% and temperatures of 45 deg. C. The 4.5 years cell was dismantled with the aim to preserve the concrete/bentonite interface. Then, a detailed sampling of the concrete/bentonite interface and the cement matrix of the concrete was performed for mineralogical, microscopy, and geochemical characterization. The water injected to hydrate the concrete/bentonite cells is synthetic

  15. Evaluation of long-term interaction between cement and bentonite for geological disposal (2) XAFS analysis of calcium silicate hydrate precipitates at cementitious and bentonite material interface

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. Numerical analyses of the long-term alteration of the engineered barriers used for the disposal of TRU waste predicted precipitation of C-S-H minerals at the interface between the cementitious materials and the bentonite-based buffer. When the C-S-H precipitates at this interface, the diffusion coefficient in the engineered barriers will decrease, resulting in reduced mass transport, which feeds back to reduce the rate of subsequent alteration. The C-S-H predicted to form at the cement-bentonite interface could not be identified directly using conventional analytical tools, including XRD, due to its low crystallinity. The authors propose that XAFS analysis, which provides spectra sensitive to the valency and coordination of the element of interest regardless of its crystallinity, would be capable of characterizing the C-S-H. The presence of the C-S-H precipitated as a secondary mineral has already been confirmed by applying chemical and XAFS analyses to bentonite specimens collected from the compacted bentonite-cement interface. However, because of the limitations on the width of specimens that can be collected by cutting from block samples, i.e. approximately 1 mm, detailed concentration profiles could not be obtained for this secondary C-S-H. In this study, XAFS spectra of thin specimens were measured using an X-ray detector in order to obtain detailed concentration profiles for the C-S-H formed at the interface between the cementitious material and the bentonite-based buffer. The X-ray detector used in the XAFS analysis consists of 1024 photodiodes arranged in line with a 0.025 mm pitch (photodiode array; PDA). Ca-K-edge XAFS measurements were conducted at the Photon Factory of the KEK. The synchrotron was operated in top-up mode with 450 mA during the measurements. Specimens were taken from a contact sample of compacted bentonite (Kunigel V1; dry density of 1.6 g/cm3) and hardened OPC (w/c = 0.6) immersed in

  16. Evaluation of Chlorophyll Fluorescence and Biochemical Traits of Lettuce under Drought Stress and Super Absorbent or Bentonite Application

    Directory of Open Access Journals (Sweden)

    Akram Valizadeh Ghale Beig

    2014-03-01

    Full Text Available The effects of two superabsorbents (natural-bentonite and (synthetic-A 200 on the chlorophyll fluorescence index, proline accumulation, phenolic compounds, antioxidant activity and total carbohydrate in lettuce (Lactuca sativa L. was evaluated. For this purpose, a factorial experiment using completely randomized design with superabsorbents at 3 levels (0, 0.15, 0.30 w/w%, drought stress at 2 levels (60 and 100% of field capacity and 4 replicates was conducted. Results showed that photosystem photochemical efficiency (Fv/Fm II under drought stress (60% FC as well as lower levels of bentonite superabsorbent polymer reduced. The minimum and maximum proline content were obtained in 0.3% bentonite, 100% FC and 0 benetonite, 60% FC, respectively. The lowest and highest phenolic compounds was corresponded to the highest levels in both super absorbents and control respectively, so that the super absorbent and bentonite, reduced phenolic compounds by 62.65 and 66.21% compared to control. 0 and 0.15 wt % bentonite in high drought stress (60% FC showed the highest and 0.3 wt % bentonite and 100% FC attained the lowest level of antioxidant activity. Control bentonite treatment beds at 60% FC and beds containing 0.3 wt. % bentonite in 100% FC, showed the lowest and the highest total carbohydrate content respectively. Results of this study indicate that bentonite can reduce the negative effects of drought stress similar to artificial super absorbent.

  17. The adsorption characteristics and porous structure of bentonite adsorbents as determined from the adsorption isotherms of benzene vapor

    Directory of Open Access Journals (Sweden)

    LEPA STOJANOVSKA

    2004-02-01

    Full Text Available The adsorption of benzene vapor on natural and acid activated bentonites was treated by the theory of volume filling of micropores. The micropore volume and characteristic values of the free energy of adsorption were determined from the adsorption isotherms. The Dubinin–Radushkevish–Stoeckli and Dubinin–Astakhov equations were used for this purpose. The results showed that natural bentonite has a more homogeneous micropore structure than the acid activated ones. The characteristic values of the free energy of adsorption for the natural bentonite were higher than those of the acid activated bentonite. This is due to differences in its structure and the pore size.

  18. Silurian bentonites in Lithuania: correlations based on sanidine phenocryst composition and graptolite biozonation – interpretation of volcanic source regions

    Directory of Open Access Journals (Sweden)

    Tarmo Kiipli

    2014-02-01

    Full Text Available Integrated correlation of bentonites (altered volcanic ashes and graptolite biozonation is presented. Detailed study of two Lithuanian drill core sections extended previous knowledge of the occurrence and composition of bentonites to the south. Iden