RD&D-Programme 2004 - SKB

A thermal model will be constructed for the Prototype Repository in the Äspö HRL using the
proposed techniques for measurement and estimation of the thermal properties and distribution
of the different rock type components. By means of back-calculation from the results from the
Prototype Repository, it will be possible to test and evaluate the accuracy and reliability of the
thermal model.
The results of this work will be used to refine the strategy for the thermal site descriptive model.
The Prototype Repository and the Canister Retrieval Test in the Äspö HRL will be modelled
with THMC codes. The purpose of these calculations is to test and verify models that describe
simultaneous transport of heat, water, vapour, gas and dissolved salts in the incompletely
saturated buffer. The heat transport conditions in the geosphere, i.e. in the near-field rock,
are not crucial for these calculations, but need to be included and reconciled with data from
thermal geosphere models.
19.2.3 Groundwater flow
Conclusions in RD&D 2001 and its review
It was observed in RD&D-Programme 2001 that model development using the codes
Connectflow and DarcyTools would continue, and that model studies of recharge and
discharge areas had high priority.
Kasam observed in its review of the programme that modelling of groundwater flow in a
regional perspective and modelling of the magnitude of groundwater formation at different
depths were important to determine.
SKI observed in its assessment that studies of recharge and discharge areas are important, but
that the development of a general hydrogeological process understanding of these matters is
also important. Further, SKI pointed out that the use of a stochastic continuum hypothesis for
modelling on a site scale has not been adequately justified.
Newfound knowledge since RD&D 2001
Fundamental knowledge concerning groundwater flow is good. Current efforts are focused
more on development of calculation tools (numerical models). Certain theoretical studies have,
however, been conducted to acquire more knowledge concerning specific issues such as nearsurface
groundwater flow and large-scale groundwater flow in order to better understand the
problems surrounding recharge and discharge areas.
The two modelling tools Connectflow /19-6 to 19-8/ and DarcyTools /19-9 to 19-11/ have been
further developed over the past three-year period. Today, Connectflow can handle nested models
(models where different scales are nested). It is, for example, possible to have a continuum
description of the repository with deposition tunnels and deposition holes nested in a local-scale
discrete network model, which is in turn nested in a regional-scale continuum model. Transient
density-driven flow can also be handled (density-driven flow only in the continuum model).
Furthermore, functionality for incorporating discrete zones has been developed, known as
implicit fracture zone functionality. Different interfaces against the modelling tool RVS have
been developed, as well as new tools for post-processing of results (for example routines for
Tecplot).
The development of the code Connectflow, where modelling of groundwater flow through
individual deposition holes and tunnels in a closed repository is possible, enables detailed
information to be produced for further calculations of radionuclide transport. This is further
described in section 19.2.12. Connectflow has also been developed to make it possible to
describe groundwater flow around an open repository, i.e. for tunnels at atmospheric pressure
/19-12/. The important issues to highlight in this type of analysis are upconing of salt water
to repository depth, inflow of water to the tunnel system in an open repository, and time for
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