EDF should repair eighty faulty weldings at unit 3 of the Flamanville NPP France, L'Institut de Radioprotection et de Sûreté Nucléaire (IRSN), the technical arm of the Autorite de Surete Nucleaire (ASN - Nuclear Safety Authority) said on 11 April. The recommendation by IRSN, which could be confirmed by ASN in a June ruling, could further delay construction of the EPR reactor and also increase costs.
“Given the importance of the identified defects, IRSN has concluded that EDF, rather than trying to justify that the weldings are fit for service in their current state, should proceed to repair the weldings,” IRSN said in a statement. ASN’s permanent group of experts has demanded EDF repair eight defective welds in secondary main cooling loop pipes inside the reactor containment, despite EDF objections, the ASN said. The weld faults are “a major obstacle to the exclusion” of a sudden rupture of the main steam-discharge pipes. ASN said it would announce its decision on the welds “in the near future” following a consultation with its group of experts.
EDF said in a statement that the experts’ recommendations could have an impact on Flamanville 3’s commissioning schedule and construction cost, which it will update again following ASN’s final ruling. In July 2018, EDF said that the welding problems had increased the reactor cost estimate by €400 million to €10.9 billion ($12.3 billion), from an initial budget of €3 billion euros, and had delayed start-up to mid-2020. In July 2018, EDF had said 53 welds on the secondary circuits would have to be redone, while for 10 others it was confident it could convince ASN that they were fit for service. Another 85 needed no repairs, it said. However, in January ASN had questioned the quality of eight weldings on pipes between the reactor building and the turbine building.
This followed earlier problems related to excessive carbon concentrations in the components manufactured at Areva’s Creusot Forge, which weakened the steel in the cover for the reactor vessel. Although IRSN had advised the cover was fit for service, ASN finally ruled that while the reactor would be allowed to start up, its cover would have to be replaced by 2024.
