RD&D-Programme 2004 - SKB

23 Alternative methods
In practice, we in Sweden have already prioritized geological disposal as a method for disposing
of our spent nuclear fuel. We are pursuing a main line with a system based on deep geological
disposal according to the KBS-3 method. Various alternatives to this main line have been
described and analyzed in depth /23-1/. The results of this analysis provide strong support for
the choice of the main line (deep disposal according to the KBS-3 method). At the same time,
however, SKB has decided to continue to follow and support the development of alternatives
to the main line. The two alternatives currently attracting the most interest are Partitioning and
Transmutation (P&T) and Very Deep Holes (VDH).
23.1 Partitioning and transmutation (P&T)
The purpose of transmutation is to greatly reduce the quantity of long-lived radionuclides that
have to be disposed of. One technical goal that is sometimes expressed for transmutation is
to reduce the quantity of long-lived radionuclides by a factor of 100. If this goal was attained,
the radiotoxicity of the remaining high-level waste after approximately 500 years would be
at a level comparable to the level the spent fuel would reach after about 100,000 years. The
remaining long-lived substances would still require a deep repository, however.
Transmutation or conversion of long-lived nuclides to stable or short-lived nuclides is mainly
done by neutrons in a nuclear reactor, i.e. the same nuclear reactions as those that occur in an
ordinary nuclear reactor. For transuranics it is primarily nuclear fission that provides effective
conversion. For other long-lived nuclides it is neutron capture. In nuclear fission, large quantities
of energy are evolved which can be utilized for electricity production, for example.
In order for the process to achieve its purpose, the long-lived nuclides to be transmuted have
to be separated from the remaining uranium. Otherwise new long-lived nuclides would be
formed by nuclear reactions between uranium and neutrons, which is how the transuranics were
originally formed (neutron capture) in the power reactors. Uranium constitutes approximately
95 percent of the remaining fuel from a light water reactor. Reprocessing, including separation
(partitioning) of different nuclides, is thus a prerequisite for transmutation. Partitioning and
transmutation, or P&T, is therefore considered a unified concept.
Conclusions in RD&D 2001 and its review
In RD&D 2001, SKB concluded that accelerator-driven systems is currently the alternative line
of development for partitioning and transmutation that is attracting the greatest interest, both
in Sweden and in other countries. The development of such systems is very costly and highly
dependent on international collaboration. SKB further observed that several fundamental
technical questions must be further clarified by research before major projects regarding
accelerator-driven systems can be defined. Considering the development situation, the required
resources and the current energy policy in Sweden, SKB does not deem it reasonable to undertake
major development projects on its own.
The reviewing bodies had no specific comments on this policy. However, some bodies
(including KTH and Uppsala University) were of the opinion that Swedish efforts in this area
are inadequate. This was commented on by SKI /23-2/, who stated that the evaluation of SKB’s
research within partitioning and transmutation is complicated by several factors, of which the
following points were mentioned:
• It is a question of extremely cost-intensive research and development where the Swedish
funding will always be marginal.
RD&D-Programme 2004 307