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The new crack on the reactor number 1 of Penly (Seine-Maritime), detected in this first quarter of 2023 and already publicized, is however not the only one. The operator of the French nuclear fleet, EDF, also noted it on two other units: that of Penly 2 and that, in Moselle, of Cattenom 3. The Nuclear Safety Authority (ASN) mentioned it on Thursday March 9 , the day after an update sent by EDF.
Still shut down for checks, reactors number 1 and 2 at Penly are not supposed to restart until May and June respectively. The end of the unavailability of Cattenom 3 is scheduled for March 26. At least according to the operator’s current forecasts. The shutdown of several reactors for prolonged control has already led, in 2022, nuclear production to its lowest level in France since 1988.
The three cracks in question concern the pipes of the safety injection system, an emergency system intended to cool the installation in the event of an accident. However, they are not of the same nature. Those of Penly 2 and Cattenom 3 are due to a phenomenon of thermal fatigue, which can occur in the event of temperature variations.
In the case of Penly 1, it is a stress corrosion phenomenon, caused by the action of mechanical stress and an aggressive environment. ASN attributes the origin to a “double repair” on a weld during the construction of this reactor, in the 1980s. This differs from previous stress corrosion cracking detected on several reactors, including Penly 1, since October 2021: these were rather due to the very design of their lines of piping.
“It’s not unusual”
The ASN classified as an incident – that is to say at level 2 on the INES scale, the international scale of nuclear events – the Penly 1 crack linked to the repair of a weld. Conversely, the independent administrative authority only considers the Penly 2 and Cattenom 3 cracks at level 1, that of anomalies. About these two, “the pipes concerned were replaced as part of the program initiated by EDF on the lines of the system (safety injection) »specifies the ASN.
The phenomenon observed at Penly 2 is 57 millimeters (mm) long, less than 10% of the circumference. Maximum depth: 12 mm (against 23 mm for that of Penly 1). “It’s not unusual. This is a significant depth », according to Julien Collet, deputy director general of ASN, quoted by Agence France-Presse. As for Cattenom 3, the defect found is longer (165 mm, or approximately a quarter of the circumference), but shallower (4 mm maximum).
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