But this file "does not require any modification of the scheduling of reactor outages, whether for 2023 or 2024", wanted to reassure Régis Clément, deputy director of the EDF nuclear fleet, in a conference call Thursday evening, while recalling that the The Nuclear Safety Authority (ASN) would have its say.
EDF has also not changed its estimate of nuclear electricity production for this year, between 300 and 330 terawatt hours, which the network manager, RTE, generally confirmed in its forecasts on Thursday. It will be better than last year.
The black series began in October 2021 with the discovery of a micro-crack in one of EDF's most recent and powerful power plants, a phenomenon called "stress corrosion". This concerns a pipe used only in the event of an emergency, to flood the reactor with water during a nuclear accident. Cracks can cause leaks.
EDF has since been forced to launch a major inspection and repair plan, revised last December, which has led to the shutdown of many reactors in the midst of an energy crisis... The company finally thought it was ready to turn the page with its latest plan providing for compulsory repairs. Until the discovery of a new crack, very important, in a pipe of the number one reactor of the Penly power station, at a place which was until now considered to be non-sensitive. This discovery forced EDF to further revise its control program, submitted on March 10 to ASN.
The authority gave details of this updated strategy in a press release on Thursday.
"ASN takes note of this change in strategy and considers that it is EDF's responsibility to implement it", indicates the nuclear policeman.
69 welds to be checked as a priority
The new problem at Penly is on a pipe that was the subject of special repairs when the plant was built in the 1980s. Until now, these repairs dating back several decades were not considered to be sources. potential for "stress corrosion", or SCC. The discovery changed everything.
"This weld was not located on an area considered sensitive, but located near a repaired weld and this case changes the knowledge we had of the subject", explained Julien Collet, deputy director of the 'ASN in the evening.
"These repaired welds, EDF had planned to go and see them, but the fact that they alone can generate CSC requires reviewing the priorities of EDF's control program", he added.
"So we have to go and see the welds that have been repaired several times and speed up as a priority. We prioritize and speed up, that's what we propose to do", said Régis Clément of EDF separately.
He also insisted on the fact that the large crack in Penly 1 had "never called into question the fundamental safety assumptions underlying the operation of this reactor".
In total, there are 320 welds repaired and therefore now suspect, in the 56 French reactors, said the ASN.
Among them, 69 are priorities, according to EDF, and the announced objective is to control 92% by the end of the year. The remaining 8% will be in early 2024 during the planned shutdown of the reactors concerned.
"At the time of construction of the [Penly] reactor, this weld had been repaired twice, once to correct a misalignment of the sections of the circuit, a second time to correct a welding defect. This particularity could explain the presence of such a deep stress corrosion crack", explains IRSN nuclear safety experts in a note published Thursday evening.
Other so-called "thermal fatigue" cracks discovered at Penly 2 and Cattenom 3 require "additional analyses", according to ASN. EDF explained that it was indeed necessary "to widen the surveillance".