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Experimental Study of Gas Permeabilities and Breakthrough Pressures in Clays

Published online by Cambridge University Press:  03 September 2012

K. Tanai ,
T. Kanno  and
C. Gallé
K. Tanai
Affiliation:
Geological Isolation Technology Section, PNC Tokai Works, Tokai-mura, Ibaraki, JAPAN.
T. Kanno
Affiliation:
Geological Isolation Technology Section, PNC Tokai Works, Tokai-mura, Ibaraki, JAPAN.
C. Gallé
Affiliation:
Département d'Entreposage et de Stockage des Déchets, CEA Saclay, 91191 Gif-sur-yvette, FRANCE.
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Abstract

In this study, gas migration experiments in unsaturated and saturated states were carried out to clarify the fundamental gas migration characteristics in compacted bentonite to be used for the geological disposal of high-level radioactive waste. In unsaturated experiments, the gas permeability for Japanese bentonite (Kunigel VI) as a function of degree of saturation was measured to examine the applicability of conventional two-phase flow models to compacted bentonite. The intrinsic permeability obtained in this study was about five orders of magnitude larger than that obtained in water permeation tests with the same density. The difference seems to originate from the change of pore structure due to the swelling phenomenon of the bentonite. Since these effects have not been evaluated quantitatively yet, various relative gas permeability functions of conventional two-phase flow models were applied as a first approximation.

Saturated experiments designed to simulate the gas migration phenomenon in a repository for the waste were carried out to obtain relationship between breakthrough and swelling pressures using Kunigel VI and French Fo-Ca clay in saturation state. The reproducibility of the breakthrough pressure was also examined for Kunigel VI bentonite. The breakthrough pressure was almost the same as swelling pressure irrespective of the type of clay. As to the reproducibility of breakthrough pressure, it was observed that first and second breakthrough pressures were almost the same for Kunigel VI specimens with the dry densities of 1.7 and 1.8 g/cm3.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 465: Symposium II – Scienfific Basis for Nuclear Waste Management XX , 1996 , 995
Copyright
Copyright © Materials Research Society 1997

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References

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