The joint venture of WS Atkins, Mace and French firm Areva was selected as preferred bidder in April 2014.
The silos direct encapsulation plant project involves processing intermediate level waste recovered from one of the oldest nuclear waste silos on the Sellafield site, the Magnox Swarf storage silo, then packaging it for long-term storage.
Initial estimated value of the contract was £1.4bn but actual value of the contract AMA has signed is £1.72bn.
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