AUTHOR=Guo Dingqing , Yang Manjiang , Wu Hongmei , Ge Daochuan , Cao Xuewu 

TITLE=Dynamic Reliability Evaluation of Diesel Generator System of One Chinese 1000MWe NPP Considering Temporal Failure Effects

JOURNAL=Frontiers in Energy Research

VOLUME=Volume 9 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/energy-research/articles/10.3389/fenrg.2021.793577

DOI=10.3389/fenrg.2021.793577

ISSN=2296-598X

ABSTRACT=Loss of power supply from the diesel generator system (DGS) after loss of offsite power (LOOP) will pose great threat to the safety of GEN-II pressurized water reactors (PWR). Therefore, it is very desirable to evaluate the DGS’s reliability. The traditional analyzing tools are limited to static approaches neglecting the dynamic sequence failure behaviors, such as reliability block diagram (RBD), static fault tree (SFT). Static reliability modeling techniques are not capable of capturing the dynamic sequence-dependent failure behaviors typically existing in NPP safety systems such as DGS, and thus often overestimate the unreliability of systems. In this paper, motivated to study the effects of sequence failure behaviors, dynamic fault tree (DFT) is applied to evaluate the reliability of the DGS of Chinese Daya Bay NPP, and an integrated two-phased Markov Chain model is also developed, which can be considered as a contribution of this article. Comparative study of DGS reliability between DFT and FT is carried out. The results indicate that the unreliability of DGS calculated by static FT is greatly overestimated by about one to two orders of magnitude compared with those derived from the DFT model, and hence DFT has a potential to relax the overestimated unreliability of nuclear power and other industrial systems to improve the economy.