非能动核电厂SBO事故风险重要序列耦合定量化

Coupling Quantification of SBO Risk Significant Sequences of Passive NPP

风险指引的安全裕度特性分析(RISMC)方法旨在运用耦合概率论安全分析和确定论安全分析的方法对事故序列的动态进程、事故发生概率和堆芯损伤频率进行评估。文章运用RISMC方法针对非能动核电厂全厂断电(SBO)事故中风险最显著的序列进行耦合定量化,通过筛选重要序列,确定重要不确定性参数、重要系统,热工模拟事故场景,计算条件失效概率和最终耦合分析得到更具现实意义的堆芯损伤频率(CDF)。在解除了重要系统的成功准则(自动卸压系统的阀门有效数),并且综合考虑了随机参数不确定性(外电恢复时间)和认知参数的不确定性(堆芯补水箱阀门阻力)之后,SBO事故风险重要序列的CDF存在一定程度的下降,这说明原始PSA分析存在一定的保守性,并且由精细的计算分析结论对处理SBO事故得出建设性意见。文章所述计算分析不仅有效地实践了一种新的耦合定量化安全分析方法,重新量化了SBO事故的风险重要序列,而且对优化SBO事故运行规程有一定的指导意义。

Risk-informed safety margin characteristic methodology(RISMC)aims at evaluating the dynamic accident process,accident probability and core damage frequency of accident sequence by using the method of coupling probability safety analysis and deterministic safety analysis.This method requires to deal with stochastic uncertainty parameters and epistemic uncertainty parameters at the same time.In this paper,the RISMC method is used to re-quantify the core damage frequency of risk significant sequence in Station Black Out(SBO)accident of passive nuclear power plant with the coupling way.A risk significant sequence S is chosen as analysis subject.After removing the success criterion of the important system heading,the sequence has been developed to a discrete event tree to be detail analyzed.By considering and sampling the uncertainty of both the random parameters and the epistemic parameters,lots of thermal-hydraulic condition has been modeled with system coeds.A new core damage frequency(CDF)coupled with sequence frequency and exceedance probability based on RISMC has been obtained.The CDF of the important sequence of SBO accident risk has a certain degree of decline,indicating that there is a certain conservatism in the original probabilistic safety analysis(PSA),and the constructive suggestions for operators responding to the SBO accident are put forward by calculation and analysis conclusions.