The day after the parliamentary hearing of the new head of EDF Luc Rémont, the Senate this morning hosted a more technical session within the walls of the Luxembourg Palace. The main actors of the French nuclear industry met in a public hearing on the problems of corrosion under tension (SCC), which is at the origin of the shutdown of a dozen reactors. The hearing was organized by the Parliamentary Office for the Evaluation of Scientific and Technological Options (Opecst).
Deputy Pierre Henriet and Senator Gérard Longuet hoped to get answers to several questions: Under what conditions could these corrosions be identified? Why couldn’t it be sooner? What is its origin, extension, gravity? How will the necessary repair checks be carried out? What guarantee do you offer? The first to speak, the CEO of EDF in charge of managing the nuclear and thermal park, Cédric Lewandowski, wanted to reassure the audience about the company’s ability to meet the schedule for restarting the reactors:
A risk of “foreign emissions”
The EDF representative returned to the story of the CCS problem in nuclear power plants, “an unexpected and unprecedented phenomenon that disrupts the operation of our nuclear fleet.” There was only one French precedent dating to the 1980s at the Bugey site, except that the corrosion was related to contamination. It was in the fall of 2021 during a ten-year visit to the first reactor in Civaux (Vienne) that the first signs were observed. They give rise to controls and a probe reveals cracks of more than 5 millimeters while the thickness of the metal of the pipes is only 3 centimeters.
EDF extends the tests to the Viennese plant and then immobilizes the four N4-type reactors before realizing at the Penly site that the problem is not limited to just the N4 level but also to the P’4. In total, 12 additional reactors are closed in the first half of 2022 while 15 welds and 230 metallurgical samples are analyzed in laboratories. All the sites in question have an operating capacity of 1,300 megawatts, while the 900 megawatt sites appear to be less sensitive to corrosion.
ASN approved EDF’s repair strategy last July with 16 reactors identified as priorities. Three are in the verification process, while six remain to be verified by mid-2023 at the latest. The agency has already conducted 38 inspections and continues to monitor the sites closely.
“We had to develop a new ultrasound monitoring technique which is a real feat, said Cédric Lewandowski. It’s not perfect yet, but we hope to be able to make the most of it next year.” Depending on the results of this, the renewal of the reactors will be immediate or deferred according to Bernard Doroszczuk who recalls that all the reactors will be reviewed before the end of 2025.
Nuclear safety, “absolute priority”?
The representatives of EDF and ASN were asked in particular about the advantages and disadvantages that guided their strategy to repair the reactors affected by CSC. The spokesman for the négaWatt association, Yves Marignac, considered that electrical safety implicitly took precedence over nuclear safety: “There is a weakness in the French nuclear park to deal with the simultaneous unavailability of several nuclear reactors. This situation exposes us to a trade unhealthy”. gap between electrical safety and nuclear safety and contributes to speeding up repairs by relaxing the application of the rules”.
Faced with these accusations, Cédric Lewandowski insisted on the priority given to nuclear safety. “There is no compromise between security and security of supply, he razed. If we have the slightest doubt about a reactor, we shut it down and we have proven it by doing so. For 12 nuclear reactors in the dead of winter. We will always be on the side of safety.” For his part, Bernard Doroszczuk recalled that security must be considered a common good.
“Sleeving” as a workaround
Still, the big shutdown operation led RN deputy Alexandre Sabatou to suggest that EDF had perhaps shown “overzealousness”: “Was it really necessary to stop the production of ‘a third of French nuclear power to to deal with the incident or would it have been possible to soften this closure? A question to which the president of the ASN replied that “it was not possible to ask EDF to keep the reactors in service and that it was essential to carry out the controls to know the scope of the damage to the entire nuclear park”. : “We were blind for half a year!”
Some voices such as Senator Stéphane Piednoir argued that there were alternatives to sectioning and replacing the pipes, citing “sleeving” which consists of adding an additional layer to temporarily protect the crack. “We do not keep the jacket because it is not a qualified process compared to French standards,” replied the EDF representative. Qualifying it requires several months or even years of training to be successful and it was impossible to do it in relation to our safety objectives. supply, but we are going to discuss it and start a dialogue on this issue with the ASN”.
In any case, the French nuclear sector should learn lessons from this vast episode of stress corrosion cracking. The director of the National Association of Local Information Committees and Commissions (ANCCLI), Yves Lheureux, expects more frequent controls and maintenance for sites with more than 35 years of activity. Bernard Doroszczuk, for his part, would like the future French energy mix to provide a greater safety margin to be able to suspend the operation of several reactors simultaneously if necessary.
Source: BFM TV
