6 October 2026
United Kingdom nuclear site operator Sellafield Ltd has selected the OneAxIoM joint venture as preferred supplier for an asset care and asset creation program valued at up to $2.78 billion (£2.1 billion).
Under the Projects and Asset Care Execution (PACE) framework contract, the joint venture and Assystem, as a key supply chain partner, will support Sellafield Ltd’s spent fuel management and retrievals mission by providing full lifecycle capabilities including engineering and design, procurement, installation and plant modification, project management and controls, commissioning, dismantling, removal and ongoing asset care.
OneAxIoM, led by Amentum and Mitie Plc, is the synergy of two Sellafield Ltd’s most successful collaborations: the 16 year AXIOM Joint Venture comprising Assystem, Amentum, and Mott MacDonald, and the OneAIM Joint Venture, comprising Amentum and Mitie Plc.
Assystem’s proven track record in delivering complex engineering design solutions and project management support and capability across one of the world’s most challenging nuclear environments has established it as a trusted delivery partner. This expertise, coupled with its long-standing contribution to the Sellafield site’s mission, was a key factor in Assystem being selected as a strategic supply chain partner to OneAxIoM, strengthening Assystem’s delivery capability in support of Sellafield’s long-term programme objectives.
As a key supply chain parter to OneAxIoM, we’re bringing together decades of experience in nuclear engineering, asset care and expert project delivery to support one of the UK's most complex nuclear sites. This marks a major milestone for Assystem. Not only does it provide a significant growth opportunity, but it also strengthens our long-standing partnership with Sellafield Ltd, enabling us to play an even greater role in maintaining the critical infrastructure that will shape the UK’s nuclear legacy and future ambitions.