Insights from the analysis of flooding-related international operating experience at NPPs

Abstract

The structured review of operating experience provides useful insights for improved operation and regulation. This paper presents insights and the related statistical analysis from the topical study of flooding-related international operating experience during the last 20 years. The study is the result of the European Clearinghouse activity and covers four databases: French, German, US Licensee Events Reports and the IAEA/NEA International Reporting System (IRS).The methodology applied includes both a qualitative and a quantitative assessment: screening, review and statistical analysis. All relevant events (263) are characterised, and a selection of these (109) are further analysed to derive insights. The paper presents 16 generic insights synthesised from 94 specific insights. The insights are grouped based on the systems causing the events and on the purpose for corrective actions.The statistical analysis shows the contribution, the trend and the correlation between the events databases and the insights. The US and IRS events contribute the most to insights, with important contributions from two other databases. A slightly increasing linear trend of the yearly number of events is missing only for the German events. The correlation analysis for the number of events contributing to the insights shows a noticeable correlation between the US and IRS databases’ and the BWR and PWR reactor type events.The analysis of the relative contribution of the events to the insights shows a statistically significantly smaller or larger contribution to several insights from different databases and reactor types. This could be the basis for a decision about the relevance and the applicability of some insights in certain countries and to specific reactor types.The fact that the most important events contributing to the insights are well distributed over the entire 20 years period shows their continuous relevance. Equally, the fact that all four databases and reactor types contribute sufficiently to the most relevant events shows that the insights are similarly relevant for all of them. The insights from this analysis seem internationally relevant recommendations and they could help the licensees and regulatory authorities to prevent flooding events from occurring, to protect safety systems from flood and to improve flooding protection and mitigation.