RD&D-Programme 2004 - SKB

DarcyTools is being developed internally by SKB. During the coming period, version 2.1, which
has primarily been developed for the needs of the site analysis, will be further developed to a
version that can meet the specific needs of the safety assessment.
Another modelling tool that will continue to be developed is the channel network model
Chan3D /19-20/. Even if it isn’t used for production purposes in site modelling and safety
assessment, this model serves an important purpose for shedding light on some specific issues.
One such issue is radionuclide transport in transient flow fields. This issue can be handled by
Chan3D, since flow and transport are simulated coupled in the same model /19-21/. The effects
of transient flow fields, for example due to shoreline displacement, will be further studied. This
is described in greater detail in section 19.2.12.
19.2.4 Gas flow/dissolution
Conclusions in RD&D 2001 and its review
No questions for further research were identified in RD&D 2001 or its review.
Newfound knowledge since RD&D 2001
Knowledge concerning the processes of gas flow and transport in the gas phase has been
compiled for the EU project Retrock /19-22/, and it is observed there that there is no great need
for further research for the intended application. Certain open questions are noted, however,
namely that it is not clear whether the gas quantities generated in a deep repository for spent
nuclear fuel are great enough to constitute a possible problem. If so, i.e. if a free gas phase
can be formed, this question should be further investigated. Specifically, better and above all
experimentally verified models for bubble flow are needed, as well as methods for devising
representative K-S-P (permeability-saturation-pressure) relationships.
Programme
Another question that should be investigated is whether gas flow (or rather two-phase flow
with water and gas phases) should be incorporated in the analysis of the resaturation process in
a previously open repository. The imagined sequence is an air-filled repository at atmospheric
pressure that is packed with backfilling material, after which pumping ceases so that the repository
slowly refills with water. In other words, we are dealing with a system that goes from a
complete gas phase to a complete water phase. It is an open question whether this situation can
be approximated with water flow alone, i.e. the gas phase in the repository is neglected when
the water pressure rises and the repository is resaturated. A probable limitation in a two-phase
description is, however, that the parameterization of the model may be associated with great
uncertainties.
19.2.5 Movements in intact rock
Conclusions in RD&D 2001 and its review
RD&D 2001 described the plans for site descriptive rock mechanical models. The need for
research initiatives regarding movements in intact rock was to be identified and analyzed within
the framework of this work.
The authorities have not made any comments on this process.
Newfound knowledge since RD&D 2001
The fundamental issues relating to characterization of the rock’s mechanical properties as well
as relevant scales for this and description and/or modelling of the stress state were addressed
within the framework of the development of a strategy for a site descriptive model /19-23/.
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