Seismic response and its analysis for components of Kashiwazaki-Kariwa Nuclear Power Plants in 2007 Niigata-ken Chuetsu-Oki Earthquake

Abstract

The Niigata-ken Chuetsu-Oki Earthquake (hereinafter referred to as "the NCO Earthquake") occurred in 2007 with a hypocenter very close to Kashiwazaki-Kariwa Nuclear Power Station of Tokyo Electric Power Company Holdings, Inc. (hereinafter referred to as "TEPCO"). TEPCO's subsequent plant investigation, earthquake response analysis using observation records and large-scale shaking table tests have provided us valuable experiences, including the fact that safety related components were undamaged and non-safety-related components sustained only limited damage. This paper describes the time history analysis of components whose damage states are based on excessive stress or deformations due to elastoplastic behavior. The input ground motions for the time history response analysis were records from the NCO Earthquake. The components were modeled with simplified bi-linear models representing their load-deflection characteristics; one of the analysis results was the maximum ductility factor of each component when subjected to the NCO Earthquake motions. Based on the assumption that increasing ductility factor values is correlated with damage to components, this paper discusses the threshold of the ductility factor that affected to the damages to components. This paper concludes that the ductility factor could be considered as a damage indicating parameter (DIP) to components whose damage states are a function of plastic deformation. If this ductility factor is reflected in the seismic design, it is considered to contribute to the improvement of the diversity and the reliability of the seismic design system of nuclear power plants.