The EDF group presented Thursday, March 16 its battle plan to control the pipes considered most at risk of a new type of cracks in its nuclear power plants, after the recent surprise discovery of very deep corrosion in the piping of a Seine-Maritime reactor.
But this file “does not require 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 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 microcrack 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.
ASN considers that EDF is responsible for implementing the strategy
EDF has since been forced to launch a major control and repair plan, reviewed last December, which has led to the shutdown of many reactors in the midst of an energy crisis… The company finally believed it was ready to turn the page with its latest plan. providing for ex officio 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”says the nuclear policeman.
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 “stress corrosion”, or CCS. The discovery changed everything.
“This weld was not located on an area considered sensitive, but 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.
320 repaired and suspect welds, including 69 priority ones
“So you have to go first and see the welds that have been repaired several times and speed up. We prioritize and we accelerate, that’s what we propose to do “, declared for his part Régis Clément, of EDF. He also insisted that Penly’s big crack 1 had “never called into question the fundamental safety assumptions underlying the operation of this reactor”.
In total, there are 320 repaired and therefore now suspect welds, out of the 56 French reactors, alerted 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 at the beginning of 2024, during the planned shutdown of the reactors concerned.
“At the time of the construction of the reactor [de Penly], 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 peculiarity could explain the presence of such a deep stress corrosion crack.”explain the nuclear safety experts of the Institute for Radiation Protection and Nuclear Safety (IRSN), in a note published Thursday evening.
Other cracks, say “thermal fatigue”, discoveries in Penly 2 and Cattenom 3 require “additional analysis”, according to ASN. EDF explained that it was indeed necessary “extend surveillance”.