The nuclear clear up company is developing commercial arrangements to cover construction and related work over the next ten years under the Construction Infrastructure and Enablers Strategic Framework.

The huge programme of work at Magnox sites dotted around the country attracted a big field of bidders, including Bam Nuttall, Black & Veatch, Galliford Try, Interserve, J Murphy & Sons, Kier, Mace and Vinci.

A source close to the bidding told the Enquirer: “All firms have been told to sit on the news until an official announcement but Balfour and Costain have been told they have got it.

“The framework is due to start this month so an official announcement is due shortly.”

The scope of CIESF encompasses requirements for design, construction, modification, repairs and refurbishment of buildings, structures and infrastructure.

Meanwhile, the winners of the four regional frameworks covering smaller work packages are due to be announced in August.