The Prime Minister will welcome plans for a new nuclear power station at Sellafield during a visit to the site today.
The Nuclear Decommissioning Authority (NDA) will announce its willingness to provide land for the building of two nuclear power stations on land adjacent to the Sellafield site.
As well as the plans for Sellafield, the NDA was also officially announcing today the nomination of Wylfa on Anglesey, Oldbury in Gloucestershire, and Bradwell in Essex as potential sites for new nuclear power stations.
A Downing Street spokesman said the Prime Minister would welcome all of the nominations.
The NDA owns the Sellafield site and rural land around it, near the picturesque village of Seascale in west Cumbria.
An NDA spokesman said he expected any new nuclear power stations would be built by a commercial organisation.
Sellafield was the world's first commercial nuclear power station. It started generating electricity in 1956 and stopped in 2003.
It is home to the nuclear power stations Calder Hall and Windscale, which are being decommissioned.
Sellafield is also used to reprocess nuclear fuel and to store large amounts of the UK's high and intermediate-level radioactive waste.
The site sits to the west of the Lake District, which attracts millions of tourists every year. It is a major employer in west Cumbria.
Derek Simpson, joint leader of Unite, who joined the Prime Minister on his visit today, welcomed the announcement, adding: "Pushing ahead with Britain's nuclear new build addresses the real concerns of real-life people. They want cheaper household bills.
"Building a new generation of nuclear power stations will create thousands of jobs in manufacturing in the UK. Nuclear energy can reduce our reliance on foreign gas and oil, and start to reduce household bills by 2015.
"It won't be popular with the Russians or the French or even the Greens but they don't vote Labour.
"The union will continue to campaign for a repository to be based at Sellafield. This will secure thousands more skilled jobs in the area."
Unite said it was also campaigning to ensure the UK's manufacturing industry carried out the majority of the work associated with any new nuclear reactors to be built in the UK.
The union said it feared that the UK's dependency on imported oil and gas from Russia will be replaced by a dependency on France to supply nuclear technology.
Mr Simpson added: "The Tory policies of the 1980s sought to make British manufacturing a relic of the industrial revolution with a horrendous human cost.
"In this post-credit crunch world, we can see just how wrong they were. The North West is a hub of excellence for manufacturing. It's high time for the resurgence of British manufacturing."
Nathan Argent, head of Greenpeace's energy solutions unit, said: "Nuclear power is fast becoming the most expensive way to produce electricity.
"Costly schemes like this will mean higher household bills and won't do anything to drag Britain out of recession. It certainly won't help us to create tens of thousands of green collar jobs or beat climate change.
"Sellafield doesn't even have the right grid connections, so there's no way it could deliver electricity.
"It would cost a fortune in subsidies to put these connections in, and, ultimately, it's the taxpayer that will have to foot the bill.
"Instead, Brown should be making a clever investment in energy efficiency. This would create tens of thousands of British jobs, and also tackle fuel poverty and climate change in the fastest possible way."