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Research on reliability models of HTR-PM reactor protection system

GUO Chao1, ZHOU Shuqiao1, and LI Duo1

1. Institute of Nuclear and New Energy Technology, Collaborative Innovation Centre of Advanced Nuclear Energy Technology, Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education, Tsinghua University, Beijing 100084, China (guochao@tsinghua.edu.cn)

Abstract: Nuclear safety is a critical issue for a nuclear power plant (NPP), while the Reactor Protection System (RPS) plays a significant role for the safety operation of an NPP. Digital RPSs have been widely used in newly-built and upgraded NPPs because of the advantages over the analogue ones. The reliability analysis of digital RPS, which is a research hotspot in the I&C field of NPP, is required by regulation authorities, development organizations, and the final users. The RPS of High Temperature Gas-Cooled Reactor Pebble bed Module (HTR-PM) is the first self-developed digital RPS to be operated commercially in China. In this paper, this digital RPS system is modelled with both static and dynamic methods. Firstly, the failure modes and effects analysis and the fault tree analysis is performed and special attention is focused on the “2-out-of-4” and the bypassed logic. Furthermore, a dynamic modelling method, the Markov chain theory is adopted. All states and corresponding dynamic transition processes are analyzed especially the degradation process from 2-out-of-4 to 2-out-of-3. Moreover, the interval of surveillance test was optimized based on this Markov model.
Keywords: reliability model; reactor protection system; fault tree analysis; Markov model
 
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