Nuclear waste management
Competence and challenges
VTT possesses the multidisciplinary expertise required in the assessment of the long-term safety of the final disposal of spent fuel and other nuclear waste. The long time perspective makes this task challenging, as there is no possibility to demonstrate the disposal system as a whole. Therefore confidence in the system’s overall safety is based on experimental data on subsystem behaviour, combined with mathematical modelling of involved phenomena.
Performance analyses of the technical and natural barriers of spent fuel repositories involve modelling the thermo-, hydro-, mechanical- and chemical evolution of the spent fuel repository and its geological environment over thousands of centuries, including modelling of the release and geosphere migration of radionuclides from the repository into the biosphere, and finally evaluation of possible radiological impacts from the disposed-of waste. Alongside these theoretical and experimental analyses, VTT is also involved in the technology development of engineered safety barriers, i.e. double-layer metal canisters and the buffer, backfilling and closure structures of the repository.
Comprehensive knowledge of the disposal system and the expertise for modelling enables the assessment of total system behaviour. The obtained results can be employed in comparison with safety criteria and prioritization of topics requiring additional research.
References and merits
Most of the key technical reports supporting Posiva Oy’s application to the Government for a Decision-in-Principle (DiP) were prepared by VTT. In May 2001, the Finnish Parliament ratified the DiP on the siting of a spent nuclear fuel disposal facility at Olkiluoto.
VTT continues to have an active role in the R&D for the ongoing stage (2001 – 2012) of the final disposal project, and in the design work on the underground research facility, ONKALO, being built at Olkiluoto.
The components of a final disposal canister of a double-layered copper/cast iron construction. Source: Posiva Oy