British Nuclear Fuels (BNFL) is expected to confirm on Thursday that it has sold nuclear power station builder Westinghouse to Toshiba.
BNFL manages 11 nuclear power stations in the UK
The Japanese conglomerate, which has been selected as the preferred bidder, is expected to be pay about $5bn (£2.8bn) for Westinghouse.
State-owned BNFL has described the deal as a "win-win", benefiting employees and the UK taxpayer.
Toshiba beat bids from General Electric and Mitsubishi Heavy Industries.
"Toshiba is a strong company with a long record of business success, and will ensure that the decades-long contributions of Westinghouse to the nuclear industry - and to the US and global economies - continue to grow," said BNFL's chief executive Mike Parker.
Westinghouse was bought by BNFL for $1.1bn in 1999. It employs 9,000 people and has annual sales of about $1.8bn.
The Westinghouse sale will provide a windfall for the UK Treasury.
But industry experts have expressed concern that such an asset is being sold off when the demand for new nuclear power stations is set to surge.
More countries are looking at nuclear energy as they look to tackle rising fuel costs and cut carbon emissions.
The UK government has just launched a three-month public consultation into the UK's future energy needs and has asked the Health and Safety Executive to examine the safety, cost and suitability of the country's existing nuclear power stations.
State-owned BNFL operates four active UK power stations and seven that are being decommissioned.