Quantification of performance shaping factors (PSFs)' weightings for human reliability analysis (HRA) of low power and shutdown (LPSD) operations

Recently, human actions during low power and shutdown (LPSD) operation has been recognized as important contributors to the safe operation of nuclear power plants (NPPs). The features of human actions differ between LPSD operation and full power operation because automatic control may be disabled, most control room annunciation tiles indicate alarmed status, and procedures are prepared with less than sufficiency. The goal of this study is to quantify the weightings of performance shaping factors (PSFs) when performing HRA during LPSD operation. In HRA, PSFs are the conditions under which an operator performs the tasks, and PSFs can increase or decrease the probability of human error. In this study, in order to quantify the weightings of PSFs, a profiling technique was adopted. To this end, human error data were collected from domestic NPP operational experience and the PSFs were investigated for describing each human error datum by using a root cause analysis method. As a result, the probabilities of human errors were provided and the weightings of several single PSF and combined PSFs which affect the probabilities of human errors were quantified when implementing HRA during LPSD operation.