三代核电厂SGTR事故应对改进分析

Analysis on Improvement of Response to SGTR Accident in Third Generation Nuclear Power Plant

蒸汽发生器(SG)传热管作为一回路冷却剂系统压力边界,与一回路其它压力边界共同构成防止放射性裂变产物逸出的第二道安全屏障,但其容易产生腐蚀损伤,是一回路压力边界中的薄弱环节。蒸汽发生器传热管破裂(SGTR)事故发生后,放射性裂变产物将有可能突破一回路压力边界及安全壳的屏蔽,进入环境。SG破口大小、SGTR事故、故障SG位、故障SG水位控制等都将直接影响放射性裂变产物进入环境的总量。从SG本体设计、SGTR事故探测、SGTR事故缓解措施等方面进行对比分析,发现三代核电机组进行了多项改进,提高了机组应对SGTR事故相关系统可靠性、冗余性,降低了事故处理时人员干预要求,提升了机组固有安全性。

Steam Generator(SG)heat exchange tube serves as the pressure boundary of the primary coolant system.Together with other pressure boundaries of the primary circuit,it forms a second safety barrier to prevent the escape of radioactive fission products.However,SG heat exchange tube is most prone to corrosion damage and it is the weak point in the pressure boundaries of the primary circuit.After SGTR accident,radioactive fission products may break through the pressure boundary of the primary circuit and the containment shield and enter the environment.The size of SG breach,SGTR accident,location of faulty SG,faulty SG water level control,etc.will directly affect the total amount of radioactive fission products into the environment.Through comparative analysis of SG body design,SGTR accident detection and SGTR accident mitigation measures,it is found that the third generation nuclear power unit has made many improvements,which improves the reliability and redundancy of SGTR accident related system,reduces the requirements of personnel intervention,and improves the inherent safety of the unit.