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Evaluation of Gas Transport Properties of Backfill Materials for Waste Disposal: H2 Migration Experiments in Compacted Fo-Ca Clay

Published online by Cambridge University Press:  28 February 2024

C. Gallé  and
K. Tanai
C. Gallé
Affiliation:
Direction du Cycle du Combustible DESD/SESD CEA Saclay, 91191 Gif-sur-Yvette, France
K. Tanai
Affiliation:
Geological Isolation Technology Section, PNC Tokai Works, Tokai-mura, Ibaraki, 319-11 Japan
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Abstract

Swelling clays may play a major role in the underground disposal of high-level nuclear waste (HLW) in deep geological formations. A multibarrier concept including a waste container, a steel overpack, an engineered barrier consisting of compacted clay (buffer) and the host rock is a potential technique for such HLW disposal. It is anticipated that H2 will be the main gas generated, mainly by anaerobic metal corrosion during disposal lifetime. After complete resaturation, the clay barrier will have a very low permeability and H2 may accumulate in the space between the overpack and the clay barrier. This could result in pressures exceeding the resistance of the clay and damage to the entire engineered barrier system (EBS).

The French Atomic Energy Commission (CEA) has performed an experimental program on H2 gas migration in a French clay referenced Fo-Ca. The tests were conducted with a specific odometer-type cell developed by the Power Reactor and Nuclear Fuel Corporation (PNC) in Japan. Permeability tests on compacted Fo-Ca clay samples of specific dry densities between 1.6 and 1.9 and for water saturation degrees between 70 and 100% provided significant H2 permeability data (ranging from 10−15 to 10−21 m2). Gas migration experiments were also performed to study the behavior of Fo-Ca clay under high gas pressure. Two kinds of gas transport threshold pressures were detected in unsaturated compacted clay. The first one, called “critical pressure”, is the pressure over which a gas outflow migrates into the clay. This pressure probably exceeds the capillary pressure of the largest pores within the clay. The second one, called “breakthrough pressure”, is detected with increasing gas injection pressure. A sudden rise of gas outflow is subsequently observed. The occurrence of the gas breakthrough is associated with the aperture and propagation of preferential gas transport pathways in the clay. This is apparently linked to the hydromechanical properties and stress state of the clay. When clay samples are not fully watersaturated, the critical pressure is always lower than the breakthrough pressure. However, when the clay is saturated, the 2 pressures appear to be very close. Finally, this study showed that breakthrough pressure—a key parameter for the long-term stability of the clay buffer—varies considerably with the gas injection increments and with the size of the sample. The results of these experiments are consistent with those reported previously by other investigators.

Keywords

DensityFo-Ca ClayGas Critical and Breakthrough PressuresGas Preferential PathwaysH2 MigrationWater Saturation Degree
Type
Research Article
Information
Clays and Clay Minerals , Volume 46 , Issue 5 , October 1998 , pp. 498 - 508
Copyright
Copyright © 1998, The Clay Minerals Society

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References

Apted, M.J. Arthur, R.C. Cole, C.R. Conca, J. and Ohnishi, Y., 1991 Review workshop for the Engineering Scale Test and Research Facility (Entry) Programme .Google Scholar
Besnus, F., 1991 Contribution à l’étude de l’influence des gaz générés par les déchets radioactifs “Alpha” sur la sûreté des stockages en formation géologique profonde France Univ de Paris Sud.Google Scholar
Besnus, F. and Voinis, S., 1991 Gas formation in ILW and HLW repositories. Evaluation and modeling of the production rates and consequences on the safety of the repository 212 901–908.Google Scholar
Coulon, H., 1987 Propriétés physico-chimiques de sédiments argileux français. Contribution au stockage des déchets radioactifs France Lille.Google Scholar
Gallé, C., 1997 Migration des gaz et pression de rupture dans une argile destinée à la barrière ouvragée d’un stockage profond [abstract] France Montpellier.Google Scholar
Geneste, P. Raynal, M. Atabek, R. Dardaine, M. and Oliver, J., 1990 Characterization of a French clay barrier and outline of the experimental programme Eng Geol 28 443–454 10.1016/0013-7952(90)90027-X.CrossRefGoogle Scholar
Gras, J.M., 1996 Corrosion assessment of metal containers for the geological disposal of HLW France EDF, Moret-Sur-Loing.Google Scholar
Gray, M.N. Kirkham, T.L. Wan, A.W.L. and Graham, J., 1996 On the gas-breakthrough resistance of engineered clay barrier materials proposed for use in nuclear fuel waste disposal .Google Scholar
Harrington, J.F. and Horseman, S.T., 1997 Gas transport properties of clays and mudrocks. Mudrocks at the basin scale: Properties, controls and behavior [abstract] .Google Scholar
Harrington, J.F. and Horseman, S.T., 1997 Gas migration in clay: Task B3.1 155–174.Google Scholar
Horseman, S.T. and Harrington, J.F., 1997 Study of gas migration in MX80 buffer bentonite .CrossRefGoogle Scholar
Horseman, S.T. Higgo, J.J.W. Alexander, J. and Harrington, J.F., 1996 Water, gas and solute movement through argillaceous media Paris, France OECD Nuclear Agency.Google Scholar
Horseman, S.T. and Volckaert, G., 1995 Disposal of radioactive wastes in argillaceous formations 11 179–189.Google Scholar
Ishikawa, H. Amemiya, K. Yusa, Y. and Sasaki, N., 1989 Comparison of fundamental properties of Japanese bentonites as buffer material for waste disposal 107–116.Google Scholar
Lajudie, A. Raynal, J. Petit, J.C. and Toulhoat, P., 1995 Clay-based materials for engineered barriers: A review 353 221–230.Google Scholar
Lineham, T.R., 1989 A laboratory study of gas transport through intact clay samples UK NIREX, Harwell.Google Scholar
Mano, T. and Ishikawa, H., 1993 Outline of geological isolation research facility and test programme of R&D in this facility Japan PNC Tokai.Google Scholar
Neretnieks, I., 1985 Some aspects of the use of iron canisters in deep lying repositories for nuclear waste Baden, Switzerland NAGRA.Google Scholar
Ortiz, L. Impey, M. and Einchomb, S., 1996 Characterization of gas flow in Boom clay, a low permeability plastic rock Switzerland Bern.Google Scholar
Ortiz, L. Volckaert, G. De Canniére, P. Put, M. Sen, M.A. Horseman, S.T. Harrington, J.F. Impey, M. and Einchomb, S., 1997 MEGAS: Modelling and experiments on gas migration in repository host rocks Brussels, Belgium European Commission, Nuclear Science and Technology.Google Scholar
Ortiz, L. Volckaert, G. Put, M. and Impey, M., 1995 The MEGAS E5 experiment: A large 3-D in situ gas injection experiment for model validation France Paris 151–162.Google Scholar
Pusch, R. and Forsberg, T., 1983 Gas migration through bentonite clay Stockolm, Sweden SKBF-KBS.Google Scholar
Pusch, R. Ranhagen, L. and Nilsson, K., 1985 Gas migration through MX-80 bentonite Baden, Switzerland NAGRA.Google Scholar
Tanai, K. and Asano, T., 1994 Hydrogen migration test plan Japan PNC Tokai.Google Scholar
Tanai, K. Kanno, T. and Gallé, C., 1997 Experimental study of gas permeabilities and breakthrough pressures in clays 465 995–1002.Google Scholar
Volckaert, G. Grindrod, P. Impey, M. Fioravante, V. and Horseman, S.T., 1992 MEGAS: Modeling and experiments on gas migration in argillaceous host rocks France Aix-en-Provence 405–416.Google Scholar
Volckaert, G. Ortiz, L. De Canniére, P. Put, M. Horseman, S.T. Harrington, J.F. Fioravante, V. and Impey, M., 1995 MEGAS: Modeling and experiments on gas migration in repository host rocks European Commission, Nuclear Science and Technology Brussels, Belgium.Google Scholar
Wikramaratha, R.S. and Goodfield, M., 1994 A proposed programme of experimental and theoretical modelling studies of gas migration through bentonite UK AEA Technology.Google Scholar
Wikramaratha, R.S. Goodfield, M. Rodwell, W.R. Nash, P.J. and Agg, P.J., 1993 A preliminary assessment of gas migration from the copper/steel canister Stockholm, Sweden SKB.Google Scholar
Wood, G.P. Impey, M.D. Grindrod, P. and Brown, R.C., 1997 Single capillary model of gas pathway propagation in Boom clay Mol Belgium 211–225.Google Scholar