MAINTENANCE RELATED EVENTS IN NUCLEAR POWER STATIONS

This paper presents the essential results of a study performed by the European Clearinghouse on Operational Experience Feedback, in cooperation with IRSN and GRS; aiming to analyse events where their direct or root cause was an inappropriate maintenance at nuclear power stations. The databases of IRSN, GRS, U.S. NRC and IAEA IRS were screened to select relevant events related to maintenance that took place in the period 2002-2013. The examination of the selected events resulted in their classification into nine categories or groups with sub-division in families and, if necessary, sub-families. In total 921 events were analysed. One of the event classifications performed was according to the type of maintenance (periodic, predictive, planned and corrective). The operational experience data analysis indicated that 47% of the events reported were related to periodic maintenance. The main affected components were valves", followed by electric power components". The main root causes observed are maintenance performed incorrectly" (e.g., improper use of tools, breach of authorization, lapse, etc), deficiencies in written procedures or documents" and deficiencies in management or organization". Regarding the impact on safety, the dominant family is potential effects on safety function" (57%), followed by significant effect on operation" (20%). Based on a detailed analysis of selected events, recommendations were developed and some of them are presented in this paper This study highlights that the continuous analysis ofmaintenance related events and the efficient utilization of operational experience provide important insights for improving the quality of maintenance and for preventing the occurrence of unusual events and thus helps to enhance nuclear safety.