The Mox nuclear fuel plant at Sellafield will be closed on Wednesday afternoon, with the loss of about 600 jobs.
The closure is a consequence of the Fukushima incident in Japan, in March.
Workers at the plant were told on Wednesday morning that there was “considerable scope” for them to be re-employed in other parts of the Sellafield complex.
It will take several months for the plant to close fully.
The West Cumbrian mixed-oxide fuel plant has cost the taxpayer £1.4bn since it was commissioned in the early 1990s.
The plant, operated by the government-owned Nuclear Decomissioning Authority, was set up to create mixed-oxide fuel for use in nuclear power plants, with its chief customers the Japanese nuclear industry, including the Fukushima complex.
The plant was built in 1996 and became operational in 2001.
NDA denied there were any repercussions for the troubled Thorp reprocessing plant, although Thorp is also involved in generating Mox fuel, which is made from plutonium and uranium.
The announcement will officially be made public at 2.30pm on Wednesday afternoon.