The firm, which runs the Cumbria nuclear site, is rolling out a new collaborative procurement model that will change how major projects are delivered.

The four successful programme and project partners will work alongside Sellafield’s in-house engineers in integrated teams over the next 20 years.

This collaborative model will be used to deliver the huge works programme more safely, efficiently and cost effectively.

The selected firms will work together to deliver three initial major projects.  The SPRS Retreatment Plant, SIXEP Contingency Plant and Replacement Analytical Project, together estimated at £1bn – £1.7bn).

Further major projects in the pipeline still need more detailed project definition and are valued at £1.9bn-2.8bn.

Firms have until 7 June to submit bids and can find tender information on the Sellafield web portal.

Sellafield projects director Steve Livingstone, said: “This is a hugely important step for Sellafield Ltd – it is a game change for the way we deal with our supply chain.

“Instead of procuring supply chains for each major project, we’ll establish a new project delivery environment based upon long term relationships with selected partners, developing closer working practices on the way.�