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Reccuring events data processing in France


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J. Tirira, P. Quentin, Workshop "how to prevent recurring events more effectively". Bottstein (Suisse), Rapport IRSN-DES/483

Résumé

The specificity of the French Nuclear power plants park (58 PWRs operated by a single utility Electricité de France – EDF), has lead this company to establish a powerful, but complex organisation to analyse operating experience events. This organisation involves both the local level, i.e. the plant itself and the national level. The local level is involved in plant event analysis whereas the national level performs the treatment of the event for all units. This inner organisation is supported by the regulator’s (Nuclear Industry Divisions and Nuclear Safety Authority) and their technical support, the IPSN. The aims of both organisations are quite similar mainly to draw lessons from feedback experience in order to set measures to prevent the events recurrence. Despite those redundant organisations, safety significant events still happen and their average rate of recurrence remains more or less the same after a period of few operation years (between 5 and 10 events per year). In fact, in most of the events records reported by the utility, it is possible to identify recurring events, especially regarding their root causes, their effects or their actual or potential consequences. Through some examples of recurring events (mid-loop operation, small pipe breaks on the RHR circuit, thermal fatigue cracks), IPSN tried to find factors to explain the recurrence of this type of event, despite efforts of the organisation involved in the operational experience feedback. It appears that operating experience feedback process and decision-making can take a long time, several years in France, especially if design modifications on safety systems are needed to solve recurring problems. Periodic review of this analytic general process by both the operators and the safety authority is probably a practical way to improve efficiency in the event treatment and response-time of corrective actions. The identification and the selection of the events to be treated at the level of the nuclear park are carried out in a methodical, systematic and regular way. Nevertheless, the finding of recurring events indicates that the operating experience process needs improvement in terms of the root causes analysis, defence in depth treatment and corrective action efficiency.