French nuclear regulator highlights “anomaly” over steel forgings in 18 reactors

French regulatory agency the Nuclear Security Authority (ASN) has revealed that it has concerns that 18 reactors operated by EDF could have similar anomalies to that discovered at the Flamanville reactor in Normandy.

A statement on the ASN’s website said that analyses carried out by EDF since 2015 concluded that the steel making up some steam generators could have higher carbon concentrations than expected, which "may lead to lower mechanical properties than expected".

The investigation was conducted at the request of ASN to check if any other EDF plants had anomalies similar to that found in the containment vessel of the EPR third-generation pressurised water reactor at Flamanville. An excess of carbon could lead to weaknesses in parts of the reactor that have to withstand high pressures.

Work on the 1.65GW Flamanville 3 reactor began in December 2007 and was expected to be completed in 2012 at a cost of €3.3bn. It is presently expected to be completed in 2018 at a cost of more than €10bn.

The area of the reactors under investigation are forgings in the shape of a half-sphere that form the lower structure of the steam generators. ASM comments that these components are "essential for safety", and that "the quality of design, manufacture and monitoring conducted during operations is an important issue".

ASN added that its investigations into the forgings will continue until "all possible consequences on plant safety are identified".
The 18 reactors suspected of having areas of high carbon are in nine power stations. They are:

  • Blayais 1 in the Gironde (pictured)
  • Bugey 4 in the Ain
  • Chinon B1 and B2 in Indre-et-Loire
  • Civaux 1 and 2 in Vienne
  • Dampierre 2, 3 and 4 in Loiret
  • Fessenheim 2 in Haut-Rhin
  • Gravelines 2 and 4 in the Nord
  • Saint-Laurent-des-Eaux B1 and B2 in Loir-et-Cher
  • Four reactors at Tricastin in the Drôme.

The suspect forgings were carried out by Areva and Japanese company JCFC.

EDF has issued a statement saying that "the analyses carried out since September 2015 have demonstrated that the margin of safety in the forgings was such that they can be relied on to function safely, and no halt of production is required".

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