The Construction Infrastructure and Enablers Strategic Framework is expected to be worth up to £30m per annum, initially for five years with options to extend up to a further five years.

The huge programme of work at 10 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.

Project work includes the design, construction and maintenance of permanent buildings and structures, infrastructure maintenance and extension works incorporating construction, civil engineering and ground works projects.

Costain is already carrying out work for Magnox. In June 2011 the Group announced that, as part of a joint venture with AMEC and Jacobs Engineering Group Inc, it had been included on a framework to retrieve and process both wet and solid intermediate level radioactive waste across all the Magnox sites in the UK.

Andrew Wyllie, Chief Executive of Costain, said: “Construction, infrastructure and maintenance will form a major part of the work to deliver Magnox sites into a state of care and maintenance.

“Inclusion on this framework is testament to our growing reputation for providing specialised engineering solutions to customers and industry sectors which have highly complex requirements.”

Balfour Beatty chief executive Ian Tyler said: “Our role in the framework highlights Balfour Beatty’s strengths in the design, delivery and maintenance of infrastructure assets in the power sector. We look forward to working with Magnox.”