基于RISMC方法论的核电厂小幅功率提升风险响应的量化评估

Quantitative Evaluation of the Impact of Small Power Uprate on Significant SBO Sequence Based on RISMC Methodology

在核反应堆安全分析过程中,确定论安全分析及概率论安全分析方法虽然可用于量化显著的设计变更对核电厂运行的影响,但是对于小幅设计变更的风险变化并不能敏感合理量化。为了解决这一问题,本文综合考虑认知不确定性及随机不确定性等多种不确定性的影响,以风险告知安全裕度特性分析(RISMC)方法论为指导,整合现有的两种安全分析方法,开发先进的安全分析方法——计算风险评估方法 (CRA)。运用该方法以典型三回路压水堆的全厂断电事故为研究对象,选取其中一组概率显著序列并对其重要的不确定性参数进行随机抽样,通过RELAP5程序建模模拟,得到该事故序列的PCT概率密度函数和相应的条件失效概率。以此为依据可以计算所选事故序列的堆芯熔毁概率,并进一步分析比较功率提升5%对核电厂风险评估计算的影响。

In the nuclear reactor safety analysis,deterministic safety analysis and probabilistic safety analysis methods can be used to analyze the impact of significant modifications,such as power uprate in nuclear power plants.However,without consideration of impact of various uncertainties,the traditional PSA modeling technique is insensitive to the limited range of design changes,such as power uprate of MUR or SPU.In the paper,with consideration of impact of the stochastic and mechanistic uncertainties,one probabilistically significant SBO sequence of three-loop PWR is revised with a advanced safety analysis method called computational risk assessment based on Risk Informed Safety Margin Characterization(RISMC)method.The new safety analysis method combines deterministic safety analysis and probabilistic safety analysis methods.Based on the distribution of PCTs and the conditional exceedance probability calculated,the differences between the standard case and the case with 5% power uprate show the new model based on the new method can be sensitive to power uprate,and the CDF can be reduced by the traditional PSA modeling case.