French nuclear power regulator Autorite de Surete Nucleaire (ASN) said Wednesday that it had requested inspections of steam generators at five Electricite de France (EDF) reactors in which high concentrations of carbon had been found. The inspections will require shutting down the reactors and are expected to occur within the next three months.
The inspections are part of a widening hunt for abnormally high concentrations of carbon in steel components manufactured by AREVA's Le Creusot forge, which was responsible for manufacture of the upper and bottom reactor pressure vessel heads for the European Pressurized Reactor build of Flamanville Unit 3 in France. From inspections of those components in 2015, the hunt for components potentially weakened by high carbon concentrations has grown to include parts made at the forge since 1965, according to the World Nuclear Association.
The initial anomalies found at Flamanville involved parts made between September 2006 and January 2007. Since then, AREVA has said as many as 400 components could be involved. In June, ASN said that 18 reactors in France, all of them operated by EDF, had steam generators that with their integrity potentially affected by high carbon concentrations, which weakens the steel.
Japan Casting and Forging Corporation manufactured 12 of those components, however all but five were inspected during scheduled maintenance or refueling outages. The remaining five, including Civaux Unit 1, Fessenheim Unit 1, Gravelines Unit 4 and Units 2 and 4 at Triscastin, are to be inspected “without waiting for the scheduled refuelling outage” the ASN said.
ASN said that analysis performed by EDF at ASN's request since 2015 conclude that certain channel heads of the steam generators manufactured by Areva Creusot or JCFC “contain a significant carbon concentration zone which could lead to lower than expected mechanical properties.” The steam generators are in use at 18 reactors of the 900 and 1450 MWe plant series, ASN said.