Construction of the new reactor at Flamanville began in 2007 and was initially due for completion in 2012.

But a string of development problems have tripped up the project, and France's EDF on Wednesday raised the expected construction costs by 400 million euros to 10.9 billion euros ($12.7 billion) -- more than three times the initial budget.

Problems were found in dozens of the 150 welds in the reactor's "main secondary system", where steam produced by the generator is returned to the turbine.

Just 85 of the welds inspected were deemed compliant, the company said, adding that it would delay by a year the loading of nuclear fuel, to the fourth quarter of 2019.

EPR reactors promise advances in safety and efficiency over conventional reactors, while producing less waste.

Yet EDF has managed to sell just a handful of the reactors as construction problems have piled up.

Two reactors being built for the Hinkley Point project in Britain are far behind schedule, as is the Olkiluoto 3 reactor in western Finland, which was supposed to be the first EPR to go online.

But it was beaten last month by the start of operations at the Taishan 1 reactor in southern China, though commercial power production at the site is still several weeks off.

France is the world's most nuclear-dependent country, with 58 reactors providing 75 percent of its electricity.

A parliamentary report last month "failings" in the safety and defences of the country's nuclear power plants, citing a series of temporary shutdowns at sites across the country.

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EDF - ELECTRICITE DE FRANCE

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