EDF confirms the presence of “two indications” of microcracks at the Civaux nuclear power plant

The electricity group EDF confirmed, on Monday, June 16, the presence of "two indications" of microcracks on pipes linked to the cooling circuit of nuclear reactor number 2 at Civaux (Vienne), while ensuring that at this stage it is an "isolated" event, with no impact on the production of the entire nuclear fleet.

The first results of analyses carried out by EDF on welds in sections of pipes crucial for cooling power plants in the event of an accident confirm "the presence of defects" at Civaux 2, said Régis Clément, deputy director of EDF's nuclear production division, during a press briefing, less than a week after the announcement of an expert appraisal.

Among these defects, one concerns "thermal fatigue" , a "historical" phenomenon in the nuclear fleet, which affects stainless steels under the effect of temperature variations. The second defect detected is "stress corrosion cracking (SCC)" .

This is the same phenomenon discovered at the end of 2021 in the nuclear fleet, which caused an unprecedented industrial crisis for EDF: nuclear power production had fallen to a historically low level in 2022 due to numerous reactors being shut down for repairs or checks, threatening France with power cuts in the midst of an energy crisis.

Well-known in the industry, stress corrosion cracking means that a material degrades and cracks upon contact with a chemical environment, over a few millimeters. According to Régis Clément, the detection of SCC – a crack of "1 to 2 millimeters" on a pipe several centimeters thick – during a maintenance shutdown of Civaux 2 is an "isolated event at this stage ." This discovery will have a "fairly minor impact" on the duration of the shutdown, assured Mr. Clément, mentioning a postponement of the restart of about two weeks, to July 30.

Of the approximately 350 inspections planned for 2025 on five reactors (including Civaux), more than 200 have been carried out and have shown "no" other signs of corrosion, Mr. Clément added. "Concerning the nuclear fleet more broadly, there too, there is no impact projected to date on the fleet's availability and production, whether in 2025 or in subsequent years," he reassured.

Since the implementation of a large-scale monitoring campaign on the sixteen reactors most sensitive to the phenomenon, EDF has deployed "much more efficient and earlier" detection methods, which can identify "very small cracks" , he explained.