Problems with weldings have forced French utility EDF (EDF.PA) to delay the start-up date for its troubled Flamanville 3 nuclear reactor to the second quarter of 2020 and pushed its cost estimate up to three times the original budget. When construction started in 2007, the target launch date was 2012, but the project has suffered a string of serious technical problems – including the discovery of weak spots in its reactor vessel cover – and has been delayed several times, according to Reuters.

The cost estimate is now up by another 400 million euros to 10.9 billion euros ($12.75 billion), EDF said in a statement.

It said that loading of the nuclear fuel, last set for the fourth quarter of 2018, was now scheduled for the fourth quarter of 2019.

On a call with reporters, Flamanville project director Laurent Thieffry said that repairs to the weldings would start at the end of this month and continue till summer 2019.

He added that the reactor would be connected to the grid in the first quarter of 2020 and its commercial start at full power was now scheduled for the second quarter of 2020.

“The new planning for the EPR reactor in Flamanville is totally realistic,” EDF head of new nuclear projects Xavier Ursat said. But he added that the startup schedule would depend on the go-ahead of nuclear regulator ASN.

EDF said the 400 million euro extra cost consisted of 60 to 70 million euros in cost directly related to the welding repairs, with the rest due to the impact of the delay on the entire project.