France generates some 70 percent of its electricity from a fleet of 56 reactors, but 32 are currently offline either for routine maintenance or to evaluate the corrosion risks.

EDF said the stress corrosion -- which produces tiny cracks -- was found at four sites near welds on pipes of cooling circuits that are crucial in case of shutdowns or accidents, prompting shutdowns and inspections of eight similar reactors.

The four reactors are now set to resume output between November 1 and January 23 of next year.

Overall output for 2022 is now expected at the lower end of its forecast of 280 to 300 terawatt-hours (TWh), an EDF spokesman told AFP.

If its own production is insufficient for France's needs, EDF imports electricity from elsewhere in Europe, where prices are soaring as Russia clamps down on exports of natural gas, also a main source for electricity.

The emergency work added to the financial woes of the heavily indebted state-controlled company, which the government now plans to fully nationalise as it moves to relaunch France's nuclear industry.

President Emmanuel Macron called earlier this year for the construction of up to 14 new reactors to power the country's transition away from fossil fuels.

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EDF - ELECTRICITE DE FRANCE