France's Areva on Monday clinched the biggest commercial nuclear power contract on record, agreeing to sell China two reactors and to provide atomic fuel for nearly two decades in a deal worth far more than expected.

At 8 billion euro ($11.86 billion) the contract would be more than double the price tag first mooted 10 months ago, when Beijing signaled it would give the French state-owned firm a slice of its ambitious nuclear expansion plan.