[en] This paper deals with the limitation and its further development of Seismic PSA (probabilistic safety assessment) in the view point of human error in structural design and construction process, and also logical failure of safety-related computers, instrumentation systems, logical mechanics such as pilot-operated safety valves under seismic events. Shibata, one of the authors, has been collecting the data on damages of industrial facilities due to past destructive earthquakes since 1964, and he concluded that both logical problems were also significant factors for Seismic PSA as well as the factors which had been discussed such as local seismicity, response fluctuation, and fragility curve. The authors recognized this fact through the cooperative study on Seismic PSA as an activity of the Subcommittee on Seismic Risk Study, to which the authors belong, in the Japan Atomic Energy Research Institute (JAERI). This paper consists of three parts. The first part deals with the summary of the JAERI's work and their issues. The second and third parts deal with human error which will be expected in structural design process and logical failure of logical systems