A nuclear reprocessing site which has been in operation for 20 years is to close in 2018 after current contracts are completed, it was confirmed on Thursday.
The Thermal Oxide Reprocessing Plant (Thorp) at Sellafield in Cumbria, which employs up to 800 workers, was commissioned in the early 1990s.
The Prospect union said the news had come as a "great disappointment", adding that only a fraction of the existing workforce will remain during the clean-out phase prior to decommissioning.
National officer Mike Graham said: "Today's announcement comes as a great disappointment to our members at Thorp who believe firmly that the plant has a future and have been actively campaigning for new reprocessing contracts.
"The announcement, though not surprising, is sudden and it is fair to say that the way this was communicated to the workforce could have been better.
"The closure will see a reduction in the numbers employed on the plant once operations cease, with only a fraction of the existing staff remaining during the clean-out phase prior to decommissioning."
Prospect said it will press the Nuclear Decommissioning Authority (NDA) on the potential redeployment of staff affected by the decision.
The NDA said in a statement that the closure decision was confirmed after it completed a strategic review of the options for the management of oxide fuels.
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