抄録
A new systematic framework of "risk monitor system" has been recently proposed by Harbin Engineering University in order to enlarge the evaluation scope of "risk" of NPP throughout the whole process of design, operation and maintenance for normal operation of NPP and applicable for various accident situations from "prior to" to "after" core melt. The proposed risk monitor system concept is constituted by two layers systems of Plant Defense-in-Depth (DiD) risk monitor and reliability monitors: The DiD risk monitor is to predict and evaluate plausible risk state from the perspective of whole plant system, while several Reliability Monitors are to evaluate the reliability of individual subsystems to fulfill their expected functions successfully under the prescribed conditions given by the DiD risk monitor. The objective of present study is to develop the reliability monitor of AP1000 passive safety systems for dynamic reliability assessment. And how many types of failure modes and factors leading to disturbance in performance of passive safety systems should be considered in the reliability analysis. As an example, a single loop model of passive core cooling system (PXS) of AP1000 is considered for analysis. The transient behavior of PXS is summarized under the large break LOCA accident and reliability analysis is conducted by GO-FLOW. Calculated results indicated that dynamic reliability of passive safety systems can be conducted by GO-FLOW method and there are main two types of potential failure modes to be considered for reliability evaluation of passive safety systems. And AP1000 would depend on the full reliability of ADS system that it would work surely when needed.
