核电厂抗震设计取消OBE原因和措施浅析

Preliminary Research on Elimination of OBE in Seismic Design Requirements for NPPs

通过分析对比美国核管理委员会(US NRC)和美国电力研究院(EPRI)出版的文件,结合核一级管道应力比的统计数据,对核电厂抗震设计中取消运行基准地震(OBE)的原因进行分析。结果表明,降低OBE对安全停堆地震(SSE)的比例,并且在抗震分析中不再把OBE作为直接的载荷因素,仅作为停堆检查的限值,能够达到优化核电厂抗震设计的目的。为了防止因此而降低核电厂抗震方面的安全性能,还需制定相关措施。

Literatures and reports by US NRC and EPRI are reviewed and the statistical data of stress ratios of some class 1 pipes are analyzed to demonstrate the reasons of elimination of OBE from the design basis of NPPs. It is reasonable to decrease the ratio of OBE to SSE, to eliminate OBE from the loading combinations, and to use OBE only as a limit to shutdown the nuclear power plants in earthquake, which can optimize the seismic design. It is shown that measures shall be taken to maintain overall safety level against earthquake.