ASN Report 2017

351 ASN report on the state of nuclear safety and radiation protection in France in 2017 Chapter 12  - EDF Nuclear Power Plants “Real time” verification The performance of periodic tests and preventive maintenance programmes on the equipment and systems helps identify deviations. Routine field inspections are also an effective means of detecting faults. Verifications during reactor outages EDF takes advantage of nuclear reactor outages to carry out maintenance work and inspections that cannot be performed when the reactor is in production. These operations are mainly used to remedy anomalies already identified, but also lead to the detection of new ones. Before each reactor restart, ASN asks EDF to identify any anomalies not yet remedied, to take appropriate compensatory measures and to demonstrate the acceptability of these anomalies with respect to the protection of persons and the environment for the coming production cycle. FUNDAMENTALS Deviation handling A deviation is non-compliance with a defined requirement or a requirement set by the licensee’s integrated management system. A deviation may thus affect a structure, a system or a component of the facility. It may also concern compliance with an operating document or an organisation. The regulations require that the licensee identify all deviations affecting its facilities and handle them. The activities related to the handling of deviations are activities important for the protection of interests. They are thus subject to oversight and monitoring requirements, the implementation of which is regularly checked by ASN. FOCUS Significant safety event rated level 2 on the INES scale concerning a seismic resistance flaw on the auxiliary systems of the backup diesel generating sets On 20th June 2017, ASN gave a level 2 rating on the INES scale to a significant safety event concerning the seismic resistance of the auxiliary systems of the backup diesel generating sets for reactors 2 and 5 of the Bugey NPP, reactors 1 and 2 of the Fessenheim NPP and all the 1,300 MWe reactors (Belleville-sur-Loire, Cattenom, Flamanville, Golfech, Nogent-sur-Seine, Paluel, Penly and Saint-Alban/Saint-Maurice NPPs). Each of the 900 MWe and 1,300 MWe reactors of the French NPPs has two backup diesel generators. This equipment provides a redundant electrical power supply to certain safety systems in the event of the loss of off- site electrical power, more particularly in the wake of an earthquake. The emergency diesel generator sets comprise a generator, a diesel engine and auxiliary systems (cooling, pre-lubrication, etc.). The significant event concerns the inability to demonstrate the capacity of the civil engineering anchors of the auxiliary systems of the diesel generator sets to withstand an earthquake. In the event of a total loss of off-site electrical power as a result of an earthquake, the operation of the backup diesel electricity generating sets would not have been guaranteed. In the light of the other deviations notified to ASN by EDF, this situation could have led to a main primary system leak from the reactor coolant pumps and loss of cooling of the spent fuel pool. Following the ASN requirements of 22nd June 2017 and 26th October 2017, EDF carried out the necessary work to reinforce the anchors of the auxiliary systems of the backup diesel generator sets for all the 900 MWe and 1,300 MWe reactors concerned. Backup Diesel electricity generator set on the Penly site, June 2017.