Precursors and startling lessons: Statistical analysis of 1250 events with safety significance from the civil nuclear sector
分析了1250起全球核安全事件，发现重大事故后监管变化持续5-6年，多机组事件主因是外部触发和设计问题，共因失效频繁发生且显著削弱安全，建议加强设计审查、操作程序更新和经验共享。
We analyze the ETH Zurich open curated database of 1250 worldwide nuclear events focused on safety significance with potentials for precursors, presented in the companion paper. We find that major accidents always trigger a wave of “reactive” reporting as well as changes in regulatory or corporate management that last 5 to 6 years, mostly due to increased alertness, improved transparency, uncovering latent design errors, and heightened public pressure. The leading causes for multi-unit events are found to be external triggers and design issues, confirming the need to adapt PSAs to cover multi-unit events accordingly. Common-cause failures (CCF) are found to occur fairly frequently, at different levels, and can significantly erode the safety of the plant. From the lessons learned from this analysis, we suggest that frequent review of components design and operating procedures, employing different teams for testing and maintenance activities on redundant trains, and sharing operational experience between plants of similar designs, are some of the steps that should be taken in order to limit future occurrences of CCFs and beyond that further improve plant safety. We identify some quantitative signs of aging for plants after the age of 25. Our findings stress the need for larger recording, reliance, and sharing of operational data to support learning from experience and avoid reoccurrence of accidents and events.