Probabilistic safety assessment (PSA) is the standard method for assessing and improving safety of nuclear power plants. Shutdown PSA is a version that has been developed relatively later compared to that associated with the assessment of plant power operation. Many common features and some differences exist between power PSA and shutdown PSA. The main PSA methods are presented jointly with the procedures for their application in order to provide a reference for successful realization of shutdown PSA. In addition, simple examples are given to facilitate the understanding of methods and models. Examples of results are shown to highlight what can be expected based on application of the methods. The results show a notable variability connected with the related variability of time durations of specific plant operating states, which affect the related risks, which in turn impact the accident frequency calculation and calculation of importance factors for specific equipment. Consequently, it is more difficult to identify the entities for safety improvements.
S. Guarro and M. Yau, “Dynamic Flowgraph Methodology (DFM) Modeling of Nuclear and Advanced Technology System Risk and Reliability Scenarios,” in Advanced Concepts in Nuclear Energy Risk Assessment and Management, T. Aldemir