The most widespread generation of reactors is suspected of having major technical problems, while nuclear electricity production has never been so low.
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Will the so-called stress corrosion phenomenon cause the French nuclear fleet to falter? There is a risk of cracks appearing on the safety system of the primary circuit, the one which is in contact with the reactor core. This phenomenon was detected on five reactors, in particular at the Civeaux, Penly and Chooz power stations.
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So far, this stress corrosion problem has been identified on recent 1,500 MW or 1,300 MW reactor models, between the end of 2021 and the beginning of 2022. Since then, six other units are suspected and in particular a 900 MW reactor at the Chinon plant. This is the Chinon 3 unit, commissioned in 1987. It is part of the oldest generation of the fleet and represents the bulk of French reactors: 32 out of 56.
There is no certainty for the moment but suspicions strong enough for EDF and the Nuclear Safety Authority to decide to take a closer look. “It is an echo that is seen during an ultrasonic inspection but it is not necessarily linked to the presence of stress corrosionexplains Julien Collet, Deputy Director of the Nuclear Safety Authority. The next step will be to cut the weld in question for laboratory expertise.”
To cut the piping, it will therefore be necessary to shut down this reactor. The six units suspected will be added to the five already shut down because of this corrosion problem, so 11 units in total. A temporary figure because EDF is continuing its checks on the entire fleet. Without however having to stop everything as a precaution, believes Julien Collet: “EDF showed that the pipes could in fact resist larger cracks than those observed so far. And EDF also studied the consequences of a pipe breaking and showed that it could be managed by the reactor safety equipment.
But the production of nuclear electricity will never have been as low as this year 2022. Thursday, April 21, it barely exceeded 50% of its capacity.