The European Pressurised Reactor (EPR) in Flamanville, Normandy -- supposed to be the model for a new generation of nuclear plants pushed by President Emmanuel Macron for the coming decades -- has been completed 12 years late at a cost of 13.2 billion euros ($14.6 billion).

French state-owned energy company EDF had said its new Flamanville 3 nuclear reactor started up earlier this week but stopped automatically on Wednesday as part of a long and complex startup process.

A spokesman for EDF said on Saturday that the Flamanville 3 reactor had been carrying out divergence operations since early morning, referring to the creation of a stable nuclear reaction.

"Teams are resuming activities," he added, confirming that the unit was expected to be connected to the grid by "the end of autumn".

French nuclear safety authority ASN told AFP that Wednesday's shutdown was the result of a "human error".

Reactors of the same design have been completed in China and Finland.

"The start-up of the EPR is a long and complex process," EDF said, warning that further automatic shutdowns were likely.

EDF had on Monday secured approval from ASN to begin fission reaction, after loading uranium fuel into the reactor in May and carrying out a battery of tests.

The Flamanville plant was scheduled gradually to ramp up to 25-percent output before being connected to the grid by late autumn, a further delay from its previous target of the end of summer.

At full power, officials predict it will be France's top-producing nuclear reactor at 1,600 megawatts, enough to supply around three million homes with electricity.