RD&D-Programme 2004 - SKB

Experiments in situ
The laboratory experiments /25-15/ and the observations in Jordan indicate that water from
leaching of concrete will react with the minerals in the rock. The scientific literature contains
measurements of kinetics for reactions between minerals (for example quartz or feldspar) and
water with very high pH. It is found that reactions can occur, but are sensitive to temperature.
For this reason, most of the experiments are done at high temperatures.
In order to see how concrete pore water reacts with rock minerals in an actual repository
environment and how this can affect radionuclides, experiments are being conducted in
situ. SKB is participating together with Nagra, Andra, JNC and Sandia in the project HPF
(Hyperalkaline Plume in Fractured Rocks) in Grimsel, Switzerland. Simulated cement pore
water has been injected into fractures in the rock together with dissolved radionuclides. The
fractures will be overcored and investigated afterwards. The project is being led by Nagra. It
started in 1997 and will continue until 2004. A fracture has been selected in the underground
facility in Grimsel, boreholes have been drilled and thoroughly investigated. Tracer tests in
general, and with radionuclides in particular, require extensive preparations, but the results
that have been obtained are valuable /25-16/. The field test has run into special experimental
difficulties due to the use of highly alkaline solutions. Laboratory experiments and calculations
have been performed as a complement to the field test /25-17, 25-18/.
Programme
See section 25.5 below.
25.5 Programme for low- and intermediate-level waste
Many of the studies concerned with the waste are applicable to all categories of low- and
intermediate-level waste – both short-lived and long-lived – since the same materials and
radionuclides occur in all waste types, to a greater or lesser extent. The same applies to
packaging and handling, with the difference that long-lived waste must for the time being be
packaged so that it can be reconditioned if the final design of the repository should require this.
A final repository for the short-lived decommissioning waste must be ready to receive waste
when decommissioning is begun on a large scale. The plan is to add an extension to SFR and
license the entire facility for short-lived waste from both operation and decommissioning. Final
disposal of the long-lived core components is planned to take place at a later stage, when most
of the Swedish NPPs have been decommissioned. This means that the waste has to be kept in
interim storage for some time. This is possible today in Clab, but an extension of Clab may
be required if all long-lived decommissioning waste is to be interim-stored there. SKB has
therefore studied different alternatives for interim storage of this waste. The overall goals of
the work with LILW during the period 2005–2010 are to:
• Put into operation a system for dry interim storage of core components in order to relieve
the load on Clab.
• Prepare for future safety assessments.
• Develop handling and storage of the waste in cooperation with the NPPs.
• Carry out preliminary safety evaluations for final disposal of short-lived operational and
decommissioning waste in SFR.
• Study the prospects for a shallow repository for very low-level decommissioning waste.
The experience gained from the safety assessment of the final repository for other long-lived
waste and the update of the safety report for SFR (Safe) has given us valuable guidance for this.
We now know what we should attach importance to and what type of information needs to be
334 RD&D-Programme 2004