Maintenance of emergency electricity generators: ASN clarification

Following publication of EDF internal documents concerning maintenance of the emergency electricity generators for its nuclear reactors, ASN makes the following clarifications.

These documents are summaries produced by EDF as part of its oversight of the maintenance of its installations. They are not transmitted to ASN, who may however consult them during its inspections if it so considers necessary.

Since 2010, EDF has used a new preventive maintenance methodology, called AP-913, the aim of which is to increase the reliability of the equipment, thus enhancing reactor safety and availability.

ASN is in favour of this approach. It does however consider that EDF needs to keep a closer watch on its implementation by the various nuclear power plants (See letter)

The summaries produced as part of this approach evaluate the performance of the preventive maintenance carried out by the licensee. They do not directly address the availability of this equipment to ensure reactor safety.

When a reactor is in operation, its emergency electricity generators must be available at all times in order to deal with an incident or accident leading to the loss of the other electricity power supplies. The general operating rules, approved by ASN, require that the licensee periodically carry out tests on the equipment to ensure that it is functioning correctly. If an equipment item required for safety is unavailable, these rules define a maximum time to repair. If this time cannot be met, the reactor must be stopped and ASN notified of the event.

ASN regularly carries out inspections on the maintenance of equipment important for reactor safety. In the light of these inspections, it more particularly considers that EDF needs to make progress in dealing with anomalies affecting its equipment, something that is also shown by the summaries published.