(GRS 184) Assessment of the Accidental Risk of Advanced Pressurized Water Reactors in Germany

Originally the safety of nuclear power plants was evaluated by means of purely deterministic methods. In the deterministic approach it is verified that pre-determined (“deterministic”) safety requirements are met under predefined conditions. Uncertainties of the evaluation, which are unavoidable for any kind of safety analysis, are taken into account by applying appropriate safety margins.
Since many years the probabilistic safety assessment (PSA) has been developed and applied as an important instrument for the safety evaluation, complementing – and using as a basis - the deterministic safety evaluation. The PSA is integrating the influences of system design, plant management and operational experience into a systematic approach. Furthermore the probabilistic approach is evaluating – as far as possible – the quantitative uncertainties of the analysis. The PSA is providing insights into the safety status of the plant under investigation, which cannot be gained by a purely deterministic approach. Therefore it became common practice, to use PSA for the support of safety relevant decision making.
This report is presenting the methods and the results of the PSA to the experts and to a broader public. GRS invites interested persons and institutions in Germany and abroad to critically review and comment the PSA. We intend to evaluate critical comments and to consider them in a revised version of the PSA.