EDF, which is leading the project to build Britain’s new nuclear plant at Hinkley Point in Somerset, also conceded that sub-standard parts had been found in a new-generation reactor under construction in Normandy.

The reactor, at Flamanville, which is of the same kind as those planned for Hinkley Point, has been beset by flaws and cost-overruns and will not open until 2022 at the earliest, a decade behind its initial schedule. EDF declined to say whether the latest problem would delay the launch still further.

The company revealed last week that some welds on steam generators made in a factory in Saint-Marcel in central France had been found to suffer from a “a deviation from technical standards governing the manufacture of nuclear-reactor components”. In a statement yesterday, it said that sixteen of the affected generators had been installed in six reactors — two at Blayais near Bordeaux and in others at Dampierre-en-Burly and Bugey in central France, Fessenheim in eastern France and Paluel in the north of the country.

Régis Clement, deputy head of EDF’s nuclear fleet, said: “None of this parts present a risk in terms . . . of the safety of the reactors. We are confident,” he said. EDF said in a statement that “no immediate action” was necessary, although the final decision on whether to shut down reactors for repairs lies with the Nuclear Safety Authority. The watchdog has a track record of demanding repairs that EDF deems unnecessary.

EDF added that sub-standard welds also had been found on four of the steam generators installed in the reactor in Flamanville, along with three steam generators earmarked for a new plant at Gravelines, near Dunkirk. All the steam generators were made in the Saint-Marcel factory, which is owned by Framatome, controlled by EDF.