The framework deal for the delivery of Fuel Element Debris (“FED”) Dissolution is part of the station’s accelerated decommissioning programme.
It is the first of several big jobs due to be awarded as part of the programme to shutdown the country’s Magnox reactors at Hinkley Point, Sizewell and Oldbury.
The job is expected to be worth £75m over ten years with possible extensions.
Costain will procure, construct, operate and refurbish plant prior to transfer to further sites.
Magnox South sites are currently decommissioning at the end of operational life and this framework is key to the safe remediation and disposal of FED produced during the generating life of the power stations.
Andrew Wyllie, Costain chief executive, said: “We are delighted to have secured this contract.
“It is testimony to Costain’s growing reputation within the nuclear industry as one of the few major contractors in the UK with the capability to carry out such complex and critical work.”