RD&D-Programme 2004 - SKB

3 RD&D-programme
The long-term safety of the various repositories is at the focus of SKB’s research, development
and demonstration work. Safety is evaluated by means of safety assessments, which simply put
can be said to consist of first carefully describing the state of affairs in the repository at some
initial point in time, and then predicting what changes might take place in the repository and
finally describing the consequences for man and the environment.
There is a constant interplay between safety assessment, research and repository design.
The safety assessment is based on a given repository design and on the knowledge concerning
long-term changes in the repository environment delivered by research. The results of the safety
assessment can be used to prioritize new research and as a basis for designing the facility. New
materials or fabrication methods can give rise to a further need for research or analyses.
3.1 RD&D-Programme 2004 – nuclear fuel
The technical solutions for managing and disposing of spent nuclear fuel can be designed in
a variety of ways. SKB’s goal is to provide solutions that are safe, cost-effective and cause as
little impact on man and the environment as possible. All of society’s requirements on protection
of human health and the environment must be met. SKB’s existing facilities fulfil these
goals. The deep repository and the encapsulation plant must do the same.
SKB’s principal efforts in the RD&D-programme for spent nuclear fuel can be divided into two
main areas: 1) technology development, 2) safety assessment and research. Very brief overviews
of these areas are provided in sections 3.1.1 and 3.1.2. The complete programme for spent
nuclear fuel is presented in Chapters 4–23.
3.1.1 Technology development
A deep repository according to the KBS-3 method is based on the deposition of copper canisters
with spent nuclear fuel, embedded in a buffer of bentonite clay, at a depth of 400–800 metres.
The deep repository can take several different forms. The final design is affected by optimization
of the technical systems and by adaptation to the prevailing geological conditions on the
site. At the same time, the requirements on safety must be met, both during construction and
operation and in the post-closure period. SKB’s primary goal for the coming RD&D period is
to compile supporting material for an application for a permit to build an encapsulation plant
adjacent to Clab.
The canisters in which the spent nuclear fuel is to be deposited are designed to resist the
pressure to which they will be exposed in the repository. The copper shell is supposed to resist
corrosion processes so that it remains intact over a 100,000-year timespan. In the reference
design, the canister consists of a cast insert of nodular iron and a copper shell with a thickness of
five centimetres. The work of designing and evaluating fabrication, sealing and testing methods
for the canister continues. Much of this work is being done at the Canister Laboratory.
The experience gained at the Canister Laboratory will influence the final design of the
encapsulation plant. During the next few years we will conduct a systematic evaluation of the
encapsulation process and make improvements and simplifications where possible. This work
will then serve as a basis for a permit application for the encapsulation plant.
The current reference design of the deep repository is general and will be adapted to the conditions
on the sites in the municipalities of Oskarshamn and Östhammar where site investigations
are being conducted. In the further work with we will study, among other things, how different
repository layouts and different buffer and backfill materials affect safety and the external
RD&D-Programme 2004 35