EDF, the French electricity service company, has discovered new defects in two reactors after uncovering a significant fissure in a reactor at a nuclear power plant in Normandy. The discovery of these defects may affect the maintenance schedule of French power plants. The Nuclear Safety Authority (ASN) reported that inspections “detected the presence of thermal fatigue cracks” in emergency pipes at reactor 2 of the Penly nuclear plant (Normandy, northwest) and reactor 3 of the Cattenom plant (Lorraine, east).
In Penly 2, the crack is 57mm long, representing less than 10% of the circumference, with a maximum depth of 12mm. The crack detected in Catechome 3 is 165mm long (about a quarter of the circumference) with a maximum depth of 4mm. Two days prior, a significant crack was discovered in an emergency pipe used to flood the reactor with water in case of a nuclear accident at Penly 1.
The phenomenon of “stress corrosion cracking” has been identified at several sites since October 2021, generating smaller cracks in other areas of the pipes. However, the crack mentioned by the ASN is not related to this phenomenon but rather to thermal fatigue, which appears in stainless steels when a piece is subject to temperature variations. This phenomenon is “well-known and has been monitored for a long time under historical preventive maintenance programs,” EDF emphasized.
Although not expected in the area where it was discovered, this finding will not change the short-term inspection program. However, EDF will have to adjust its maintenance program to include thermal fatigue inspections in more extensive areas, according to Julien Collet, the Deputy Director General of the ASN. EDF will have to present a revised control strategy to the ASN in the coming days. In total, the electricity company will have to review 200 welds in all its plants, which could cause prolonged reactor shutdowns and uncertainty about nuclear production in 2023.
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