Wolverhampton-based support services and construction company Carillion has won a £118 million contract with British Nuclear Group.
It will build a store at Sellafield, Cumbria, for waste materials arising from decommissioning.
Carillion has been working with BNG on the product and residue store since 2003.
It is the first major construction contract to be let since the formation of the Nuclear Decommissioning Authority, for whom BNG now manages and operates the Sellafield site.
One of the key purposes of the store is to accommodate materials already at Sellafield which need to be retrieved from older facilities, repackaged and placed in a modern complex. It will receive materials recovered from historic fuel manufacturing buildings that are now being decommissioned.
Work on the three-year contract will start this month.
Carillion chief executive John McDonough said: "We are delighted to have secured this contract with British Nuclear Group."
Tom Gilroy, project manager, said: "This is a very important project for the Sellafield site. The store will be built to exacting standards and will afford an enhanced level of protection and security for nuclear materials."