EDF is to buy a majority share in a nuclear reactor business owned by French firm AREVA.
The energy company plans to buy between 51% and 75% of AREVA NP.
AREVA said it would sell at least 75% for €2 billion (£1.4bn).
AREVA expects the transaction to be completed in 2016 following regulatory approvals.
The companies have signed a memorandum of understanding, which includes plans to improve and develop their co-operation in areas including research and development, international sales of new reactors, the storage of spent fuel and dismantling.
They also plan to set up a company – 80% owned by EDF and 20% owned by AREVA NP – aimed at optimising the design and management of new reactor projects.