* Repairs could cause further delays and increase cost
* EDF sought to convince regulator to leave welds in place (Adds EDF statement, expert group comments)
By Geert De Clercq
PARIS, April 11 (Reuters) - EDF should repair faulty weldings at the nuclear plant it is building in northern France, according to the technical arm of French nuclear regulator ASN.
The recommendation by IRSN, which could be confirmed by ASN in a ruling expected as early as June, could cost the utility hundreds of millions of euros and lead to further delays at the reactor in Flamanville.
“Given the importance of the identified defects, the 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.
In a separate statement, ASN said a group of independent nuclear experts had also recommended that EDF either repair the weldings or make improvements to the reactor’s design so that it could withstand breakage of the weldings.
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.
Last July, EDF said that due to the weldings problems it had increased the reactor cost estimate by another 400 million euros to 10.9 billion euros ($12.3 billion), from an initial budget of 3 billion euros, and delayed startup again to mid-2020.
The utility had planned to redo 53 of the weldings on the reactor’s secondary circuit and hoped that for another 10 it could convince ASN they are fit for service.
But ASN said in January there were questions about the quality of eight weldings on pipes between the Flamanville 3 reactor building and the turbine building, and that there was a problem with one of them.
ASN is unlikely to disregard IRSN’s recommendations when it makes its ruling.
In 2017, Flamanville faced a similar cliffhanger situation, when ASN had to rule on whether weak spots found in its steel cover made that component unfit for service.
At the time, IRSN had advised the cover was fit for service, but ASN finally ruled that while the reactor would be allowed to start up, its cover would have to replaced by 2024. ($1 = 0.8864 euros) (Reporting by Geert De Clercq; Editing by Georgina Prodhan, David Evans and Susan Fenton)