Operating Experience for Valves at the Nuclear Power Plants of Ukraine and the European Union

Abstract

The paper presents information on the results of analyzing operational events at nuclear power plants (NPP) of Ukraine and the European Union that were caused or related to the failures of valves. The first part of the paper provides a brief overview of the European Clearinghouse on Operational Feedback for Nuclear Power Plants study on operational events with failure of the valves important to NPP safety. The abovementioned study considered events for the period from 1997 to 2016, which were taken from the IAEA database, databases of technical support organizations of France and Germany, as well as those provided by the Swiss and Spanish regulatory authorities. The main results of the study were presented in the paper, and the main causes of operational events caused by valve failures were observed. In addition, technical areas that required the development of recommendations were indicated. The paper includes a statistical assessment and a detailed analysis of the root causes of operational events at Ukrainian NPPs caused by or related to the failure of valves of all types, regardless of the effect on safety, for the period from 1998 to 2018. The approach for the analysis of operational events at Ukrainian NPPs is similar to that used in the above-mentioned study. Within the framework of the statistical analysis, the distribution of operational events at Ukrainian NPPs related to the failure of valves by years, nuclear power plants and systems was presented. The results of the analysis of the root causes of valve failures was presented within three groups referring to equipment, documentation, personnel and management system. In the final part of the paper, a comparative analysis of the contribution of the root causes obtained from the results of both studies was carried out, and the general lessons and specific recommendations for further consideration during the oversight activity are presented.