Plan for safety case of spent fuel repository at Olkiluoto

Posiva aims to present the Safety Case supporting the construction license application of the spent fuel repository at Olkiluoto by 2012. An outline and preliminary assessments will be presented in 2009. Interim reporting and an update of the Safety Case plan will be presented in 2006, as required by the authorities. The KBS-3 disposal concept aims at long-term isolation and containment of spent fuel assemblies in durable copper-iron canisters emplaced in a repository to be constructed at a depth between 400 and 600 metres in crystalline bedrock. By 2012, studies on the KBS-3 disposal concept and site investigations at Olkiluoto will have been continued over about thirty years. The construction of an underground rock characterisation facility (called ONKALO) was started in June 2004. The investigations are carried out in close cooperation with the Swedish SKB developing and assessing the same disposal concept at candidate sites, resembling Olkiluoto, at the other side of the Baltic Sea. A safety case is the synthesis of evidence, analyses and arguments that quantify and substantiate the safety, and the level of expert confidence in the safety, of a planned repository. Posiva's Safety Case will be organised in a portfolio including ten main reports, which will be periodically updated according the overall schedule presented in the plan. The Site report describing the present state and past evolution of the Olkiluoto site, as well as the disturbances caused by the construction of ONKALO and the first stage of the repository, forms the geoscientific basis of the Safety Case. The engineering basis is provided by the reports on the Characteristics of spent fuel, Canister design, and Repository design. The Process report containing descriptions and analyses of features, events and processes potentially affecting the disposal system, and the report on the Evolution of site and repository form the scientific basis of the Safety Case. The latter report will describe and analyse the evolution of the disposal system from the emplacement of the first canisters in the repository over the various transient phases into the far future. Radiation safety and fulfilment of regulatory requirements will mainly be dealt with in the Biosphere assessment, Radionuclide transport (safety assessment) and Complementary evaluations of safety (e.g. natural analogues) reports. The Summary report draws together the key findings and arguments. According to the outlined overall schedule, new reports on Site, Characteristics of spent fuel, Canister design, Repository design, and Evolution of site and repository should be available by 2006. The central contents for the Safety Case interim reporting will then be provided by the Process report (published in 2004) and the Evolution report. By 2009, a first or second version of each main report of the Safety Case should already be available. The central contents for the outline and preliminary assessments of the Safety Case will then be provided by the Site, Process, Radionuclide transport and Complementary evaluations reports compiled between 2007 and 2009. The final reports for the Safety Case supporting the construction license application will be compiled in 2010-2012. The Safety Case Plan will be updated along the progress of the Safety Case, for example, in association with the interim reporting of 2006 and 2009.