French nuclear safety regulator Autorité de Sûreté Nucléaire (ASN) has agreed to give EDF more time to complete safety upgrades at its 32 900 MWe nuclear power reactors in operation at the Blayais, Bugey, Chinon, Cruas-Meysse, Dampierre, Gravelines, Saint-Laurent and Tricastin NPPs. These include France’s oldest nuclear units, which began operation between 1977 and 1988.

Every 10 years. France’s reactors are reviewed by ASN, first undergoing an initial generic review phase, which covers subjects common to all 900 MWe reactors. This is followed by a 'specific' review phase, which relates to each reactor individually.

In February 2021, ASN prescribed the implementation of the major safety improvements planned by EDF for the fourth periodic review of the 900 MWe reactors, as well as additional provisions that ASN considered necessary to achieve the review’s objectives. ASN said this closed the generic phase of the review, “which concerned the studies and modifications of the installations common to all 900 MWe reactors, which are designed on a similar model”.

Moving to the specific review phase, ASN said EDF must deploy the modifications linked to this review on all 32 900 MWe reactors. “Currently, EDF has carried out or initiated the fourth ten-yearly inspections of 16 of its reactors, during which the majority of safety improvements were deployed,” it noted.

However, in a letter dated 13 October 2023, EDF requested a postponement of the deadlines for some of the requirements of this phase, “given the difficulties in being able to respect them”. EDF justified its request by:

  • the occurrence of technical hazards during implementation of certain requirements;
  • changes in the scheduling of outages for fuel renewal, linked in particular to the discovery of stress corrosion on auxiliary lines, to long-term accidental outages and to tensions affecting the electrical network; and
  • the concomitance of other periodic reviews, causing strain on its engineering capabilities.

ASN said the modifications requested by EDF “also aim to standardise the deadlines between the reactors, in order to facilitate the industrial programming of the work, to limit the number of different configurations of the reactors and thus to facilitate the appropriation of safety improvements by the teams. responsible for operations”.

ASN concluded that, “taking into account the difficulties presented by EDF and the justifications provided regarding the deadline extensions”, it “considers the request acceptable”. It added that EDF’s application and ASN’s draft amending decision would be subject to public consultation for a period of three weeks from 10 November.

Image: The Bugey nuclear power plant site (courtesy of EDF)