Development of seismic counter measures against cliff edges for enhancement of comprehensive safety of nuclear power plants, 2; Nuclear building system, reactor vessel and piping

Choi, B.  ; Nishida, Akemi  ; Guo, Z.; Yamano, Hidemasa   ; Takada, Tsuyoshi*  

In this research, the seismic safety of nuclear power plants (NPPs) is treated as a system, in which the various cliff edge effects are identified and quantified based on the concepts of risk and defense in depth, and a methodology is then developed for avoiding these cliff edge effects. As the first step, preliminary elastic-plastic analyses of the NPP building system are carried out, and knowledges on the dependency of cliff edge effects on various modeling factors are obtained. Based on these knowledges, preliminary fragility evaluations of the reactor vessel and piping are carried out, and the effectiveness of a horizontal seismic isolation system against the cliff edges is addressed.