RD&D-Programme 2004 - SKB

As a complement to the numerical models, analytical simplified descriptions of near- and
far-field models have been developed. They are extremely fast and can be used, for example, to
make scoping calculations and supplementary probabilistic calculations in future safety assessments.
The work in the safety assessment is concentrated on the repository concept KBS-3V, but the
KBS-3H variant with horizontal deposition of the canisters is also being studied. Long-term
safety of KBS-3H will be analyzed under the leadership of Posiva, with the goal of presenting
a safety assessment in 2007 with Olkiluoto as the reference site.
13.2 Research on long-term safety
The goal of the research on long-term safety which SKB is conducting is to understand
the processes (long-term changes) that occur in a deep repository and how they affect the
repository’s ability to isolate the spent nuclear fuel.
Detailed accounts of the programmes for fuel, canister, buffer, backfill and geosphere follow in
Chapters 15 to 19. Possible research and development needs for the initial state are discussed
for each repository section. The time for the initial state may be different for different repository
sections. Many analyses concern the evolution of conditions around individual deposition holes.
All deposition holes will undergo more or less the same evolution from the time the canister and
bentonite are deposited in them.
After the discussion of the research and development need for the initial state, all processes
are dealt with. The processes are divided into radiation-related (R), thermal (T), hydraulic (H),
mechanical (M) and chemical (C), plus processes related to radionuclide transport. Biological
processes – microbial – are included in the chemical processes (C). In some cases a treatment
of individual processes is not sufficient for understanding the course of events. The subdivision
of processes has therefore sometimes been augmented with descriptions characterized as
integrated studies. One example is the hydro-mechanical-chemical (HMC) evolution of a
damaged canister, another the thermo-hydro-mechanical (THM) evolution of an unsaturated
buffer.
Chapters 20 and 21 discuss the research that is needed to chart the changes to which the
evolution of the biosphere and the climate give rise.
There is no separate chapter on natural analogues this time, as there was in RD&D 2001.
Activities in the field are now fully integrated in the research programmes for the different
barriers. This is described in greater detail in section 13.2.8.
Table 13-1 shows all processes of importance for long-term safety that are dealt with in
Chapters 15 to 19. The colour code provides a rough idea of the magnitude of the planned
initiatives for the different processes during the upcoming three-year period. The scope of
the planned research does not necessarily reflect the importance of the process for long-term
safety. The corresponding information for the initial state is found in Table 13-2. The following
sections provide a brief overview of the most important research areas for the different parts of
the repository, the biosphere and the climate.
146 RD&D-Programme 2004