双层安全壳压水堆LOCA事故的放射性后果分析审查

Radiological Consequences Analysis of a PWR with Dual Containments Loss-of-Coolant Design Basis Accident

压水堆冷却剂丧失设计事故后果分析主要涉及释放源项、大气弥散和场外辐射后果三个方面。针对具有双层安全壳的压水堆冷却剂丧失设计基准事故,简述了放射性后果分析方法,计算了场外放射性后果,并对放射性后果审查中应当注意的几个问题进行讨论:(1)事故源项。通常可分别考虑为释放到内层安全壳的源项,以及释放到环境的源项。前者主要取决于堆芯裂变产物的积存量,后者不仅与释放到内层安全壳的裂变产物有关,而且与自然的和工程的清除过程以及外层安全壳的缓解作用密切相关。(2)大气弥散因子的计算。根据环境资料的获取情况,可以按照NRC R.G.1.4给出的确定论方法进行保守的估计,也可以按照NRC R.G.1.145描述的概率论方法进行估算。(3)场外放射性后果。主要考虑隔离区边界和低人口区外边界的个人剂量,包括全身剂量和甲状腺剂量。

The radiological consequence analysis mainly involves accident source terms, atmospheric dispersion and offsite radiological consequences. This paper described briefly the radiological consequence analysis methods for a Loss-of-Coolant Design Basis Accident （LOCA DBA） in allusion to a PWR with dual containments. The offsite radiological consequences were calculated. The following issues in the review of the radiological consequences were discussed; （1） accident source terms can be considered as the source terms to the inner containment and source terms to the environment. The former strongly depend on the inventory of fission products in the reactor core, and the latter is not only related to fission products in the reactor core, also to the removal mechanisms including natural process and engineered safety feature as well as the mitigation by outer containment; （2） the determination or probability methodology in NRC Regulatory Guide 1.4 or 1. 145 can be used in atmospheric dispersion estimation based on the collected environmental data information, and （3） the doses to persons located at the boundary of the exclusion area and outer boundary of low population zone are more concerned in the determining offsite radiological consequences, including whole body dose and the thyroid doses.