British Nuclear Fuels (BNFL) has sold its US nuclear clean-up unit for £51m ($91m) to Utah-based Energy Solutions.
A number of nations are planning to boost nuclear power output
BNFL, which also plans to sell its US-based nuclear power station construction unit Westinghouse, wants to focus on its UK businesses.
State-owned, loss-making BNFL operates the Sellafield waste reprocessing plant in Cumbria and the UK's remaining older Magnox stations.
Plans to sell off its businesses is proving controversial.
Many critics argue that the company is getting rid of valuable assets just as demand for nuclear power is about to pick up, a development that could make large amounts of money for the firm.