ASN requires that inspections be carried out within the next three months on the steam generators of five EDF reactors in which the steel contains a high carbon concentration

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ASN has asked EDF to carry out additional inspections within three months on certain channel heads of the steam generators^[1] on 5 of its reactors, in which the steel is affected by a high carbon concentration. The performance of these inspections will require shutdown of the reactors concerned.

The analyses performed by EDF at ASN’s request since 2015 conclude that certain channel heads of the steam generators manufactured by Areva Creusot Forge or JCFC^[2], contain a significant carbon concentration zone which could lead to lower than expected mechanical properties. These steam generators equip 18 reactors of the 900 and 1450 MWe plant series. Of these reactors, 12 are equipped with channel heads manufactured by JCFC liable to contain a particularly high carbon concentration.

EDF has provided ASN with data aiming to demonstrate the operating safety of the 12 reactors concerned. Further to the analysis carried out with the support of IRSN and after technical discussions with EDF, ASN has concluded that additional inspections should be carried out within three months, without waiting for the scheduled refuelling outage of these reactors. The purpose of these inspections will be to verify whether each of the channel heads concerned is in conformity with the file transmitted by EDF.

These inspections have been carried out or are in progress for 7 of the 12 reactors concerned^[3], on the occasion of scheduled outages. EDF has confirmed that it will carry out these inspections on the other 5 reactors within three months. ASN today issued a resolution requiring the performance of inspections on these reactors:

• Civaux NPP, reactor 1;
• Fessenheim NPP, reactor 1;
• Gravelines NPP, reactor 4;
• Tricastin NPP, reactors 2 and 4.

With the support of IRSN, ASN is also examining the substantiating data transmitted by EDF. This examination will take several weeks, or possibly longer, if additions are required to the file transmitted.

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On 7^th April 2015, ASN made public the discovery of an anomaly in the composition of the steel in certain zones of the vessel closure head and the vessel bottom head of the Flamanville EPR reactor. The detection of this anomaly led ASN to ask Areva NP and EDF to learn all possible lessons from this event. Three processes are currently under way:

• on other components of the EDF reactors, the search for technical anomalies similar to that detected on the Flamanville EPR vessel. This search enabled EDF to identify similar anomalies on the channel heads of certain steam generators, which are the subject of this press release;
• manufacturing quality reviews on parts in the Areva NP manufacturing plants, which enabled Areva NP to detect irregularities in the manufacturing files from Creusot Forge;
• initiation of a review of BNI licensee monitoring of their contractors and subcontractors, of ASN oversight and of the alert mechanisms.