核电厂安全系统冗余度研究

Study on the Redundant Degree of Nuclear Power Plant Safety System

本文对核电厂安全系统冗余度的概念进行了澄清,认为不能简单地将安全系列的数量机械地等效于冗余度。N+1的冗余度满足单一故障准则的强制性要求,N+2的冗余度是实现在线维修的可选项。进而介绍了国际上主要核电机型的安全系统配置和冗余度,说明了冗余度与运行灵活性的具体关系。在冗余度研究的基础上,对三环路压水堆的两种安全系统配置方案(两个系列带母管和三个独立系列)进行了分析比较。两种方案均为N+1冗余度,但是对非能动部件(母管)单一故障的考虑有所差异。通过对我国和国际核安全法规、用户要求文件及相关标准的研究发现,非能动部件的单一故障问题不应成为这两个方案选择的决定因素。综合考虑安全性利益及经济性代价,两个系列带母管的方案是更加优化更平衡的设计。

This article makes a clarification for the concept of the redundant degree of nuclear power plant safety system,which cannot be simply equivalent to the number of safety trains.The redundant degree of N＋1 satisfies the single failure criteria which is a mandatory requirement,and the redundant degree of N＋2 is an option for In-service Maintenance.The configurations and redundant degrees of safety systems of the main nuclear power models in the world are further introduced,and the specific relations between the redundant degree and operational flexibility are interpreted.On the basis of the study,the analysis and comparison is performed for two kinds of safety system configurations of three-loop pressurized water reactor,i.e.two trains with a common header and three independent trains.Both designs are of redundant degree of N＋1,but are different in the way whether to consider the single failure of passive component（common header）.The studies on nuclear safety codes,standards and utility requirements reveal that,the single failure of passive component should not be the decisive factor in selecting the two designs.With the comprehensive consideration of the safety benefit and economic cost,the design of two trains with a common header is more optimized and balanced.