In an attempt to avoid a $2 billion obligation, energy giant Electricite de France SA – EDF, has agreed to purchase the half of a nuclear venture it doesn’t own from partner Constellation Energy Group Inc. for an amount said to be worth $249 million – in both cash and shares.

Constellation, which is based in Baltimore, is set to receive $140 million in cash together with 3.5 million of its own shares – in exchange for its stake in UniStar Nuclear Energy – which owns sites for at least four new reactors at existing plants.

Under the terms of the deal, Constellation will give up its right (under a previous contract) to sell $2 billion of plants to EDF.

EDF is Europe’s biggest power producer and already owns half of UniStar. The company offered to buy the remaining half at “fair market value” – on the condition that Constellation ceased to exercise the option to sell 12 of its non-nuclear plants to EDF.

Constellation is believed to have considered exercising the option, which was devised in 2008 when the companies were fighting off a bid by Warren Buffett’s Berkshire Hathaway Inc., on account of government delays in loan guarantees.

In a letter to investors, Martin Young, a London-based analyst for Nomura International Plc, stated:

“The threat of the put option has been removed… EDF will need a new partner. New nuclear in the US is not attractive at this juncture”