French nuclear inspectors noticed a higher-than-expected concentration of carbon in the reactor being built at Flamanville in northwestern France

The French state electricity group at the head of the project to build Britain’s new nuclear power station received a welcome boost yesterday when it was authorised to restart seven reactors in France closed after safety fears.

However, EDF was told that four other reactors would stay shut while tests continue.

The decision by France’s nuclear safety authority came with the country’s atomic industry facing one of its biggest ever crises, a scandal that erupted weeks after Theresa May had approved EDF’s plans to build two new generation European Pressurised Reactors at Hinkley Point in Somerset at a cost of £18 billion.

French inspectors discovered what they called a significant carbon concentration in steel in 18 of France’s 58 reactors. They said that the carbon