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POSIVA Report 1998-8

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Name:

Modelling Gas Migration in Compacted Bentonite A Report Produced for the GAMBIT Club

Writer:

P.J. Nash; B. T. Swift; M. Goodfield; W.R. Rodwell

Language:

English

Page count:

82

ISBN:

951-652-046-4; 1239-3096

Summary:

Working report: POSIVA Report POSIVA 98-08, 81 pages
ISBN 951-652-046-4


MODELLING GAS MIGRATION IN COMPACTED BENTONITE


ABSTRACT

This report describes the first phase of a programme of work that has as its overall
objective the development of a computational model that can simulate the results of
experiments on gas migration through highly compacted bentonite, and will provide the
basis of a model suitable to assess the effects of bentonite barriers on the build-up of
pressure and the escape of hydrogen gas from disposal canisters in a radioactive waste
repository.

In this first phase of the project, the possible mechanisms and controlling features of gas
migration through compacted bentonite have been reviewed, and a preliminary
computational model of the process has been implemented and evaluated.

In the model it is assumed that gas invasion of the clay occurs by induced
microfissuring, and that the permeability of the pathways thus created depends on the
gas pressure (or the effective stress).

Experimental data on gas migration in compacted bentonite that was collected under
well controlled conditions by Horseman and Harrington was used in a preliminary
evaluation of the new model. The model was able to reproduce qualitatively all the
features seen in the subset of the experimental data used in the evaluation, and to
provide quantitative agreement to substantial sections of the results of test sequences,
but quantitative agreement between simulation and experimental results over a whole
test sequence was not obtained. As part of the model evaluation, the dependence of the
results obtained on key model parameters is reported.

Outline plans for a further phase of work are suggested.


Keywords: bentonite, gas migration, modelling, repository


POSIVA Report POSIVA 98-08, 81 pages
ISBN 951-652-046-4


MODELLING GAS MIGRATION IN COMPACTED BENTONITE


ABSTRACT

This report describes the first phase of a programme of work that has as its overall
objective the development of a computational model that can simulate the results of
experiments on gas migration through highly compacted bentonite, and will provide the
basis of a model suitable to assess the effects of bentonite barriers on the build-up of
pressure and the escape of hydrogen gas from disposal canisters in a radioactive waste
repository.

In this first phase of the project, the possible mechanisms and controlling features of gas
migration through compacted bentonite have been reviewed, and a preliminary
computational model of the process has been implemented and evaluated.

In the model it is assumed that gas invasion of the clay occurs by induced
microfissuring, and that the permeability of the pathways thus created depends on the
gas pressure (or the effective stress).

Experimental data on gas migration in compacted bentonite that was collected under
well controlled conditions by Horseman and Harrington was used in a preliminary
evaluation of the new model. The model was able to reproduce qualitatively all the
features seen in the subset of the experimental data used in the evaluation, and to
provide quantitative agreement to substantial sections of the results of test sequences,
but quantitative agreement between simulation and experimental results over a whole
test sequence was not obtained. As part of the model evaluation, the dependence of the
results obtained on key model parameters is reported.

Outline plans for a further phase of work are suggested.


Keywords: bentonite, gas migration, modelling, repository


Keywords:

bentonite; gas migration; modelling; repository

File(s):

Modelling Gas Migration in Compacted Bentonite A Report Produced for the GAMBIT Club (pdf) (1.3 MB)


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