Research on Key Problems of Digital Instrument and Control System Reliability Analysis for Probabilistic Safety Assessment

Under accident conditions, the support of digital instrument control system especially the normal operation of protection and safety monitoring system has an important impact on the safety of nuclear power plants. As the basic core components of digital I&C system, the card modules integrate and cooperate to perform nuclear power plant operation, data display, control, protection and safety monitoring functions. The existing card reliability analysis methods appeared to be too conservative, and lack enough operation experience and field test as sample data. In this paper, analysis tools such as RiskSpectrum PSA professional software are used, through the methods of static fault tree model refinement, card reliability test, Bayesian/frequentist statistical analysis, a quantification method of card reliability parameter are put forward, which is more suitable for PSA. The PSA model of digital I&C PMS is refined and optimized according to the results, truly reflects the reliability level of the digital I&C system. While verifying the advancement of digital I&C system, this work provides technical basis for design and operation revision or optimization decision, thus improving the safety and economy of nuclear power plants.