Safety improvement and operational optimization based on shutdown PSA

Traditionally, safety analyses have been focused on operational modes with critical reactor and large power output. In recent years, however, an increasing interest has been focused on the shutdown mode. This report gives a short summary of methods used in studies made so far on safety assessment on shutdown and low power states (LPS) at Vattenfall reactors. Furthermore, it describes the measures taken because of the results of the shutdown studies, to reduce the risks during LPS. (author)