核电厂SBO事故小幅功率提升风险响应量化评估

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

传统的安全分析方法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。本文综合考虑认知不足不确定性及随机不确定性等多种不确定性的影响,运用风险指引的安全裕度特性分析(RISMC)方法论,整合现有的两种安全分析方法,以典型三回路压水堆的全厂断电事故中轴封失效为主因的序列为研究对象,着重分析电力恢复时间对事故后果的影响,计算额定功率工况和小幅功率提升(5%)工况下该事故序列的堆芯损伤频率。结果证明改进的方法能够计算得到更加真实的堆芯损伤频率,并且可以敏感量化小幅功率提升(5%)的风险响应。结合丧失热阱为主因的序列,全厂断电事故的风险重要序列的风险增长值为12.6%。

With consideration of impact of the stochastic and mechanistic uncertainties,one probabilistically significant SBO sequence of three-loop PWR is revised with an advanced safety analysis method called computational risk assessment(CRA)based on risk informed safety margin characterization(RISMC)method.The new safety analysis method combines deterministic safety analysis and probabilistic safety analysis methods.The difference ofcoredamagefrequency(increase 12.6%)between the standard case and the case with 5%power uprate evaluatedby CRA method showsthat the new PSA model can be sensitive to the issue of limited scope of power uprate,and the CDF can be reduced reasonable compared with traditional PSA method.