UPDATE 2-EDF's Flamanville nuclear plant faces new delay over faulty welding

* ASN rules weldings must be fixed before reactor startup

* EDF had hoped to fix weldings in 2024, after startup

* Flamanville debacle weighs on future of French nuclear (Adds ASN, EDF, Greenpeace comments)

PARIS, June 20 (Reuters) - EDF faces new cost overruns and delays of up to three years at the nuclear reactor it is building in Flamanville in northern France after the French regulator ordered repairs.

ASN, the French nuclear watchdog, said on Thursday that state-owned EDF would have to repair eight faulty weldings in the reactor’s containment building, adding that it had rejected a request to delay repairs until 2024, after its startup.

“Delaying the repairs until after startup would raise issues about reactor safety during the transition period,” ASN said.

In a similar procedure two years ago, ASN ruled that Flamanville would be allowed to start up despite weak spots in the steel of its reactor vessel cover, but ordered it to replace the reactor cover by 2024 at the latest.

EDF said in a statement it is analysing the impact of the ASN ruling on the Flamanville startup schedule and costs and that it will give a detailed update in the coming weeks.

ASN director Bernard Doroszczuk told reporters that EDF had estimated it could repair the weldings by the end of 2022.

This means the Flamanville startup would again be delayed by two or three years from the most recent startup target of loading fuel in the reactor by the end of this year.

Problems with the weldings were first reported early last year and in July EDF said that a total of 53 weldings on the reactor’s secondary circuit would have to be redone, while it was confident it could convince ASN that 10 others were fit for service.

The state-owned utility delayed the reactor startup by a year and targeted the loading of fuel in the reactors during the fourth quarter of 2019, with commercial operation by mid-2020.

When construction of Flamanville started in 2007, the original target launch date was 2012.

In July 2018 EDF also said the welding problems would add an extra 400 million euros in costs, pushing the total cost of the project up to 10.9 billion euros, compared to an initial estimate of 3 billion euros.

Greenpeace France said in a statement the repairs would push the cost up by another two billion euros at least.

“EDF has been in denial about this since 2013, first denying there was a problem, then refusing to fix it, then by wanting to fix it after startup. It is a scandalous attitude towards nuclear safety,” Greenpeace France’s chief nuclear campaigner Yannick Rousselet said.

EDF wants to build new reactors as its current fleet of 58 reactors is ageing and Flamanville’s problems are weighing heavily on the future of the nuclear industry in France.

French President Emmanuel Macron has asked EDF to draw up a plan for building new reactors, with a view to making a decision about nuclear newbuild in 2021, but that plan hinges on the EPR reactor model in Flamanville being operational.

Problems with Flamanville and another EPR under construction in Finland are also weighing on EDF’s ability to sell reactors abroad. EDF is building two EPRs at Hinkley Point, Britain, for its UK subsidiary. ($1 = 0.8864 euros) (Reporting by Sudip Kar-Gupta and Bate Felix Writing by Geert De Clercq Editing by Alexander Smith)