Japanese conglomerate Mitsubishi and French engineering consulting firm Assystem have taken stakes in French nuclear reactor business New NP, created from Areva, electricity firm EDF said Monday.

The operation will value New NP at 2.5 billion euros, it said. 

EDF had obtained the green light in May from EU anti-trust regulators to buy out the troubled Areva Group's nuclear reactors business.

It said Mitsubishi Heavy Industries would take a stake of between 15 and 19.5 percent and Assystem 5 percent. 

"EDF remains open to the entry of other strategic partners," the state-owned electricity supplier said.

Assystem had said in May that it was targeting a stake in Areva NP as it shifts focus away from the automobile and aeronautical sectors.

In a statement on Monday, it said it was investing 125 million euros ($142 million) in the deal.

Areva, France's national champion in nuclear construction, has been in difficulty since the 2011 Fukushima disaster in Japan dealt a crippling blow to the prospects of the sector.

Areva's woes have been compounded by construction problems affecting its first EPR reactor in Finland -- now expected to open nine years late in 2018.

Areva's former CEO Anne Lauvergeon has been charged in a case linked to the company's disastrous 2007 purchase of a Canadian uranium mining firm.

EDF agreed in June 2015 to purchase up to 75 percent of Areva's reactor unit at an initial valuation of around 2.7 billion euros, with the deal expected to be finalised this year.

In April, Paris notified the EU Commission of a restructuring plan to save Areva, incorporating a previously-approved 4.5 billion euros ($4.75 billion) payout from public coffers.

France sees nuclear energy as a key national industry, which explains the government's close involvement in talks to restructure the sector.