核电厂重要厂用水系统的物项分级及其影响分析

Analysis on Safety Classification of Essential Service Water System and Its Impact Analysis in a Nuclear Power Plant

[目的]重要厂用水系统负责向核岛提供冷却水源,并把热量带到最终热阱,实行物项分级有助于力求经济的前提下实现安全功能最优。[方法]SSG-30方法是按照物项所承担安全功能的重要性以及失效后果的严重程度进行分级,依据系统流程对物项的安全功能进行分解,同一系统的不同功能可以采用不同的安全分类和分级,同一功能的不同设备可以采用不同的安全分级,同一设备的不同部件可以进一步分级,可以采用功能冗余的方法满足单一故障准则。[结果]分级结果可以用来复核系统功能,如安全级部件必须满足抗震要求并配置应急电源后方可投入运行。不能依据既有压水堆设计中成熟的“工程经验”来降低物项的安全等级。[结论]运用功能分解进行物项分级的方法可为其他项目设计提供参考。

[Introduction]Essential service water system is responsible for providing cooling water to the nuclear island and bringing heat to the ultimate heat sink,implementing safety classification is helpful to achieve the optimal safety function under the premise of economy.[Method]SSG-30 was the method to classify items according to the importance of their safety functions and the severity of their failure consequences.The security functions of the items were decomposed according to the system process,different functions of the same system could be classified and graded differently,different devices of the same function could be classified differently,and different components of the same equipment could be further graded,functional redundancy could be used to satisfy the single failure criterion.[Result]Grading results can be used to review system functions,for example,the safety level components must meet the seismic requirements and be equipped with emergency power supply before they can be put into operation.The safety level of items can not be reduced according to the mature"engineering experience"in the design of existing PWR.[Conclusion]The method of item classification by functional decomposition can provide references for other PWR project design.