Effect of Logic Degradation on Reliability of Digital Reactor Protection System

The paper primarily discussed the advantages of the digital reactor protection systems（RPR） compared to the analog system and the effect of the voting logic degradation on the system reliability.Based on the current common four-channel reactor protection system and the traditional reliability block diagrams（RBD） technology,two system reliability models were established and different logic degradation cases were discussed.The results showed that,the digital system is better than analog systems,which logic degradation can reduce the system risk when the reliability of system is weakened and the diagnostic coverage（DC） is large.DC contributes greatly to the system reliability.This paper also provided a method to obtain the basic data for PSA of whole system or plant.