RD&D-Programme 2004 - SKB

Results of tests being done abroad, for example by CEA, under the auspices of Andra and by
Enresa can be evaluated and utilized to broaden the body of experimental data. CEA’s test is
being done on MX-80 bentonite which is exposed to large temperature gradients and relates
to one of the most important processes, namely redistribution of the initial water content by
heat-driven vapour transport.
In the TBT test, the work of applied simulation is continuing. As data are generated and trends
become clear in the test, a phase of evaluation modelling will be initiated. The purpose is to
evaluate the relevance of the models used in the blind predictions that were made at the start of
the test. The evaluation modelling is being done in cooperation with modelling groups organized
by Andra and Enresa.
As the material models are developed, they are applied in the Code Bright and Abaqus modellings
of the Prototype Repository, the Canister Retrieval Test, the Backfill and Plug test and
Lasgit. The modelling work is being conducted within the various projects, but will also be
included in a joint project where modelling groups from different organizations participate
(EBS Task Force).
The modelling work is also being conducted in the form of simulation of ongoing field tests
(see below) and follow-up and analysis of the measurement results. Modelling of the Buffer-
Container experiment at the URL in Canada and modelling of the continuation of the Febex
experiment at Grimsel, Switzerland, will also be done.
Field studies
The field studies are being conducted by follow-up of the ongoing Prototype Repository project,
Canister Retrieval Test and TBT test (Temperature Buffer Test) at Äspö. Dismantling of the
outer section in the Prototype Repository is planned to take place in 2008, and dismantling of
the Canister Retrieval Test with test of retrieval technology in certain parts is planned to take
place in 2007.
Laboratory experiments
In parallel with the model studies and follow-up and modelling of the field tests, laboratory
experiments on water-unsaturated bentonite will continue for the purpose of gaining a better
understanding of the unsaturated processes and gathering data to determine parameter values in
existing models. The following types of tests are planned:
• Oedometer tests on unsaturated samples with controlled negative pore pressure in the
bentonite (different constant relative humidities). These tests will be done to determine some
parameters in the mechanical model Code Bright.
• Tests with constant volume and measurement of negative pore pressure and swelling
pressure at changed water content. Supplementary tests for further verification and parameter
determinations in the model that is under development (of the relationship between negative
pore pressure, degree of water saturation, void ratio and swelling pressure).
• Tests with temperature gradients applied across bentonite samples under controlled forms.
The purpose of these tests is to improve the models for water redistribution in a temperature
gradient.
• Tests of vapour transport and water transport through unsaturated samples. The wetting
rate is measured by applying elevated relative humidity (RH) to one side of a bentonite
sample and measuring the inflow of water, and alternatively by applying free water on one
side of a bentonite sample. The samples are kept at constant volume during the tests. The
purpose of the tests is to obtain better data as a basis for the vapour and water transport
models.
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