Performance Assessment Modelling for the Geological Siting Regions for the L/ILW and HLW Repositories in the Context of the Swiss Site Selection Plan

In Switzerland, the Nuclear Energy Law requires the disposal of all radioactive waste in deep geological repositories. The procedure for selecting the repository sites is defined in the Sectoral Plan for Deep Geological Repositories and consists of three stages. In Stage 1, the National Cooperative for the Disposal of Radioactive Waste (Nagra) proposed geological siting regions based on criteria relating to safety and engineering feasibility. As part of Stage 2, Nagra has to select at least one site within each siting region, to carry out a provisional safety analysis for each site and a safety-based comparison of the sites. In order to achieve these objectives, the state of knowledge of the geological conditions in the siting regions has to be sufficient to perform the provisional safety analyses. In October 2010, Nagra submitted a report which documents Nagra’s technical-scientific assessment of this precondition, based on a comprehensive list of processes and parameters relevant for safety and engineering feasibility. A part of this assessment consists of test calculations for the provisional safety analyses. This paper summarizes how the numerous test calculations have been identified, how the concepts of radionuclide release from the repository are implemented into numerical codes and how input data and results are organized in order to ensure transparency and traceability.