The giant Sellafield nuclear reprocessing plant in Cumbria is being hived off by owners British Nuclear Fuels Limited (BNFL).
Sellafield will be one of the main assets of the new business
The company is creating a new business called British Nuclear Group, in readiness for the creation of a new decommissioning agency.
The new firm will have an annual turnover of almost £2bn and employ 15,000 people.
The new company will also look to carry out decommissioning work abroad.
From April 2005 the new operation will face competition for decommissioning work following the creation of the Nuclear Decommissioning Authority (NDA), which will be based in Cumbria.
As part of the Energy Bill, which still needs parliamentary approval, the majority of BNFL's assets and liabilities will transfer to the NDA.
This will include responsibility for decommissioning plants at Sellafield, which state-owned BNFL has owned and operated for more than 30 years.
BNFL says the new company will also look to use its 30 years of experience in decommissioning and cleaning up more than 50 nuclear facilities worldwide to
secure international business.
Current contracts include cleaning parts of the former Chernobyl complex in Ukraine and power plants in Bulgaria.
A third strand to the work carried out by the British Nuclear Group will be to apply UK-based expertise to the US market.
During the run-up to April, British Nuclear Group will be a separate part of BNFL.
Lawrie Haynes, who is chief executive of British Nuclear Group, said the new company would "significantly enhance the clean-up of the nuclear legacy".
"In the UK, our focus will be on delivering innovative clean-up programmes for the NDA to enable them to demonstrate value for money for the UK