The Federal Energy Regulatory Commission Thursday authorized Electricite de France's (1024251.FR) $4.5 billion purchase of nearly half of Constellation Energy Group Inc.'s (CEG) nuclear business.

The agreement with the state-controlled company will keep Constellation a publicly traded company. The agreement includes an immediate $1 billion cash investment by EDF and an option for the French company, the world's largest nuclear operator, to buy up to $2 billion of Constellation Energy's non-nuclear power plants.

FERC said the Commission approved the terms of an agreement that gives Constellation Energy the option but not the obligation to sell its ownership interests in various non-nuclear generating plants and associated assets to EDF at agreed prices totaling up to $2 billion.

The closing of the sale of the 49.9% ownership interest in Constellation Nuclear is expected in late 2009. The put options relating to Constellation Energy's non-nuclear assets will remain in effect until the end of 2010, FERC said.

The companies also agreed to give EDF the right to nominate one director to Constellation Energy's board, expanding the board from 12 to 13 directors.

-By Ian Talley, Dow Jones Newswires; 202-862-9285; ian.talley@dowjones.com