EDF said on 19 May that it is continuing its inspection programme and is preparing, along with the nuclear industry, to repair sections of the pipes affected by stress corrosion. At this stage for 2022, EDF considers that it is not necessary to schedule new reactor outages and updates its French nuclear output estimate. Currently 12 reactors are shut down and are being inspected for stress corrosion:
- The result of metallurgical examination of samples taken from the pipes of the auxiliary circuits of the reactors at Civaux 1, Chooz 1 and Penly 1 confirmed the presence of stress corrosion near welds of the RIS (safety injection circuit) and RRA (shutdown reactor cooling circuit) circuits;
- Checks and examinations carried out on Chinon B3 confirmed the absence of stress corrosion on the RIS circuit. Evidence of stress corrosion was located on a weld of the RRA circuit;
- Checks and investigations are ongoing on the other eight prioritised reactors (Civaux 2, Chooz 2, Cattenom 3, Bugey 3, Bugey 4, Flamanville 1, Flamanville 2 and Golfech 1).
EDF said it had carried out ultrasonic inspections, investigations on pipes samples, digital welding simulations and studies to calculate the speed of propagation of stress corrosion. At this stage, these analyses allow EDF to confirm slow stress-corrosion propagation and to observe the existence of a compression zone which blocks the propagation of the phenomenon. EDF has defined an inspection programme for the entire nuclear fleet:
- In 2022, 900MWe reactors will be inspected as part of their ten-year inspections. This concerns the Tricastin 3, Gravelines 3, Dampierre 2, Blayais 1, and Saint-Laurent B2 reactors;
- The inspection programme for the 1,300MWe reactors will be established after integrating the lessons learned from the appraisals and checks in progress on the auxiliary circuits of the Penly 1 reactor.
At this stage for 2022, EDF considers that new reactor outages do not need to be scheduled to carry out checks. Discussions are ongoing with the Autorité de sûreté nucléaire (ASN - Nuclear Safety Authority) on the stress corrosion phenomenon inspection and repair programme. EDF said the nuclear industry “is making an unprecedented, concerted effort to replace the portions of the pipes affected by stress corrosion”. EDF has started to procure tubes and elbows from European steelmakers. Production rates have been optimised to deliver the first spare parts before summer. All suppliers qualified to carry out these activities are now preparing for the work. Dozens of welders have been specially trained to guarantee high-quality workmanship.
In view of all of these aspects and EDF’s decision to shut down impacted reactors and inspect the reactors likely to be impacted, ASN took note of EDF’s actions.
These events required EDF to adjust its French nuclear output estimate for 2022 to 280-300TWh compared with 295-315TWh previously. At this stage and in the expectation of checks and repairs to be completed, the 2023 French nuclear output estimate is unchanged (300-330TWh).