Regulator ASN in June ordered EDF to repair 8 hard-to-reach weldings in the reactor's containment building.

EDF said in its first-half earnings statement that "at this stage, commissioning cannot be expected before end of 2022".

"Given the time needed to prepare, execute and test the repairs ... there will be a delay of more than three years," EDF CEO Jean-Bernard Levy said on a call.

He reiterated EDF will give a cost estimate in coming months, after a detailed examination of three repair scenarios.

In July 2018, just months after the weldings problems were first reported, EDF had already delayed fuel loading to end 2019, and added 400 million euros to the budget, pushing total cost to 10.9 billion euros.

When construction of Flamanville started in 2007, the original target launch date was 2012, which means that this new delay will push the overall delay to more than a decade.

Levy also said the utility had not had problems coping with the hot weather of the past weeks and that despite power demand in July hitting a record of 60 gigawatts, EDF was able to provide sufficient power in France and was even able to export.

He said 40 of EDF's 58 reactors were currently available, as several are out for planned maintenance or refuelling.

In recent weeks, several reactors have been shut temporarily in order to prevent them from releasing hot cooling water in rivers that already suffer low flow rates and high temperatures.

"(Despite this) our fleet is robust and the temporary closure of one or other reactor has no effect on availability of power," Levy said.

EDF's French nuclear production was up 0.5 percent to 203.7 terawatt hours and Levy said he trusts the firm will be able to reach its 2018 target of 395 TWh.

EDF's first-half core earnings rose 3.5% to 8.35 billion euros ( £7.47 billion ), with revenues up 4.3% to 36.46 billion, despite its UK nuclear output falling 19 percent to 24.5 TWh.

UK core earnings plunged 76% to 128 million euros, from 485 million. The introduction of a cap on standard variable tariffs and the suspension of capacity revenues also weighed.

French hydropower output fell 32 percent to 20.1 TWh as the first half of 2019 ranked as the second-driest halfyear over the last 30 years, EDF said.

Net earnings jumped 45 percent to 2.5 billion euros thanks to effect of strong stock and bond markets on the value of EDF's "dedicated assets", which it holds to cover nuclear liabilities.

EDF confirmed its 2019 earnings guidance for core earnings of 16-16.7 billion euros.

(Reporting by Geert De Clercq; Editing by Sudip Kar-Gupta, William Maclean)

By Geert De Clercq