Test Programs for Degraded Core Shroud and PLR Piping: Simulated Crack Models and Input Seismic Waves for Shaking Test

Since the age-related degradation of structures and components in nuclear power plants has been a key issue regarding assessments of seismic safety, the Japan Nuclear Energy Safety Organization (JNES) initiated seismic test programs in fiscal 2004 for the degraded core shroud and primary loop recirculation (PLR) system piping used in old BWR plants. The objectives were to: i) obtain a better understanding of the vibration characteristics and seismic strength of degraded structures and components having cracks due to aging, ii) ensure a margin of seismic design safety by considering age-related cracking, and iii) verify the JSME Code Rules on Fitness-for-Service for Nuclear Power Plants in Japan. Plans were made to test the components of the core shroud and PLR system piping under quasi-static displacement control of monotonous and cyclic load conditions. Plans were also made to test combined components on a shaking table by using a 1/2.5-scale core shroud model and an approximately 1/3-scale PLR piping model. All test models were designed to contain simulated cracking due to aging, involving cracks assumed to have the maximum allowable size according to the JSME Code Rules. The input seismic waves were prepared for the combined component tests of the scaled models based on a modified envelope of broadened response spectra of all S2 design seismic waves in Japan. Final evaluation of the simulated crack models and input seismic waves used for the tests will be conducted in fiscal 2005.