Development of safety assessment of nuclear power plants using indicators

The study is based on an indicator system which is under development at the Radiation and Nuclear Safety Authority (STUK). The goal of this study was to define and develop both PSA-based indicators and indicators from failure statistics. As PSA-based indicators the possibility was studied to define and express the risk importance of exemptions from the Technical Specifications, failures, preventive maintenance and other disconnections of devices covered by the Technical Specifications, operating events covered by Guide YVL 1.5 and plant modifications. In this piece of research the applicability of plant specific living PSA-models used for calculation of indicators was examined. The research included both Loviisa and Olkiluoto nuclear power plants in Finland