STUDY OF RATIONALIZED SAFETY DESIGN BASED ON THE SEISMIC PSA FOR AN LMFBR

Seismic PSA was carried out for a typical liquid metal cooled fast bre eder reactor (LMFBR) in order to study the rationalized seismic design , maintaining and/or improving safety during seismic event. The seismi c sequence quantification identifies the dominant structures, systems and components (SSCs) to the seismic core damage frequency (CDF). The sensitivity analyses by reducing or increasing the seismic capacity fo r SSCs are used to examine the optimized seismic design in view of saf ety and economical aspects. The LMFBR-specific risk-significant SSCs a re reactor coolant boundary, decay heat removal coolant path and react or control rod, which are different from those of light water reactors (LWRs). The electrical power supply system has a minor contribution t o the seismic CDF. The sensitivity study shows that passive safety fea tures of LMFBRs are important to maintain and/or enhance seismic capac ity. The passive safety includes the decay heat removal capability via natural circulation and safety measures without depending on the supp ort systems such as alternating current (AC) electrical power, for exa mple. On the course of seismic sequence quantification, a methodology to evaluate the probability of seismic-induced multiple failure has be en developed and applied to the decay heat removal function. The resul ts suggest the multiplicity of the triply redundant system is to be co nsidered for the significant components such as the decay heat removal path when one considers the difference in the seismic response. (C) 1 998 Elsevier Science Ltd. All rights reserved.