Nuclear industry powerhouse AREVA said Tuesday that it would continue to analyze a steam generator for the Fessenheim Nuclear Power Plant's Unit 2 reactor after French regulators suspended a test certificate for the component in which steel construction anomalies had been revealed in June.
The French regulator, ASN – in English, the Nuclear Safety Authority – said they had “suspended the test certificate it issued to AREVA NP in 2012 for a stream generator currently installed on reactor 2 of the Fesseheim nuclear power plant.”
The plant has been shut down the reactor since late June for a maintenance outage that was expected to last until August 29, Platts reported. But the certificate suspension may mean the reactor will remain offline for longer than that.
A preliminary report on Fessenheim components was submitted to the ASN June 15.
Reportedly, the lower shell for one of the generators is the focus of the investigation. It was manufactured in 2008 at Le Creusot Forge, which was first discovered to manufacture components with high-carbon anomalies when similar problems were found in the composition of the reactor vessel head and the reactor vessel bottom head at the Flammanville nuclear power plant construction project.
AREVA said Tuesday that the generator remained safe to operate and that it would continue to make its case to regulators. “The technical analyses conducted by AREVA NP experts have concluded, at this stage, that the irregular findings are not detrimental to operational safety.” the company said. “In order to substantiate the robustness of the case, a similar part has just been cast and forged at Le Creusot plant to validate its mechanical and chemical characteristics,” AREVA said.
In the wider investigation of the Le Creusot facility initiated after the component anomalies were discovered at Flammanville, AREVA said that 85 reports on components forged at Le Creusot, out of 10,000 that were reviewed, included irregularities.
But the presence of areas of high-carbon steel in the components is a safety concern, given the anomaly increases the brittleness of the steel. In the case of the steam generator “knowledge of this non-compliance would have led ASN not to issue a test certificate in 2012,” the agency said.
The statement follows a June release from ASN that points to a far wider potential problem. Analysis carried out by EDF since 2015 concluded that certain steam generator channel heads could contain high carbon concentrations, which could compromise the integrity of the components. The steam generators in question equip 18 reactors of the 900 and 1450 MWe plant series, the agency said.
The analysis was conducted as a follow up to the Flammanville vessel investigation. It involved channel heads manufactured at Creusot Forge and by a foundry in Japan.
The steam generator channel heads are hemispherical forged parts that make up the lower part of the steam generators. They contribute to containment of the primary system water and are essential for safety. “The quality of their design, manufacture, and in-service monitoring is, therefore, extremely important,” ASN said.
Other reactors that may be implicated in a broader investigation include one at Le Blayais NPP, reactor 4 at Bugey, B1 and B2 at Chinon, units 1 and 2 at Civaux, reactors 2, 3, and 4 at Dampierre, reactors 2 and 4 at Gravelines, reactors B1 and B2 at Saint-Laurent-des-Eaux and reactors 1, 2, 3, and 4 at Tricastin, the ASN said.
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