熔盐堆丧失厂外电源事故的概率安全评价

Probability safety assessment of LOOP accident to molten salt reactor

以熔盐堆丧失厂外电源(Loss of offsite power,LOOP)为例,采用概率安全评价(Probabilistic safety assessment,PSA)程序Risk Spectrum对其进行PSA分析,同时假设一回路没有任何阀门,且设备可靠性数据基于现有成熟电站设备的可靠性数据,得到了熔盐堆LOOP事故引发的放射性物质向堆芯释放的事故序列及其频率。结果表明,熔盐堆LOOP事故引发的放射性物质向堆芯的释放频率为2×10-11/(堆·年),获得了不确定性分析的点估计和区间估计,重点找出了对LOOP事故引发的放射性物质向堆芯的释放频率贡献最大的因素是反应堆舱室冷却功能失效,为后期熔盐堆系统的设计与改进提供了有效的帮助。

Background： Loss ofoffsite power （LOOP） is a possible accident to any type of reactor, and this accident can reflect the main idea of reactor safety design. Therefore, it is very important to conduct a study on probabilistic safety assessment （PSA） of the molten salt reactor that is under LOOP circumstance. Purpose： The aim is to calculate the release frequency of molten salt radioactive material to the core caused by LOOP, and find out the biggest contributor to causing the radioactive release frequency. Methods： We carried out the PSA analysis of the LOOP using the PSA process risk spectrum, and assumed that the primary circuit had no valve and equipment reliability data based on the existing mature power plant equipment reliability data. Results： Through the PSA analysis, we got the accident sequences of the release of radioactive material to the core caused by LOOP and its frequency. The results show that the release frequency of molten salt radioactive material to the core caused by LOOP is about 2~ 10-11/（reactor＇year）, which is far below that of the AP1000 LOOP. In addition, through the quantitative analysis, we obtained the point estimation and interval estimation of uncertainty analysis, and found that the biggest contributor to cause the release frequency of radioactive material to the core is the reactor cavity cooling function failure. Conclusion： This study provides effective help for the design and improvement of the following molten salt reactor system.