Sellafield Names Preferred Suppliers for £3.6bn PACE Framework

#

Sellafield Ltd has named preferred suppliers for a single asset management framework worth up to $4.8 billion (approximately £3.6 billion), collapsing two previously separate procurement streams into one integrated vehicle at the largest nuclear complex in Western Europe. The Project and Asset Care Execution (PACE) framework was announced on 30 September 2026 and will run for up to 15 years, potentially through 2041.

PACE replaces two predecessor programmes, Sellafield’s Integrated Asset Care framework and the Design Service Alliance. Two joint ventures have been identified as preferred suppliers across distinct missions: spent fuel management and retrievals under Lot 1, and specialist batch and decommissioning facilities under Lot 2. Formal contract awards remain subject to finalisation of contractual arrangements.

Here is what the framework covers, who will deliver it, and what a 15-year commitment of this scale signals about the direction of Sellafield’s asset management strategy and the wider UK nuclear sector.

What the PACE framework covers and how it is structured

PACE stands for Project and Asset Care Execution, and its defining feature is integration. Rather than contracting asset care and asset creation separately, the framework delivers both under a single vehicle, replacing the Integrated Asset Care framework and the Design Service Alliance in one move.

The duration is deliberately long. PACE runs for an initial nine-year operational period with an option to extend by a further six years, taking it potentially through 2041. Procurement notices put the estimated value range at £1.9 billion to £3.6 billion across the framework life, with a mid-point of £2.4 billion once inflation is factored in.

The framework also embeds off-site construction as a structural principle rather than an afterthought. Assets are built and readied away from the site before installation, covering three stages:

• Prefabrication of components and modules
• Inspection and quality assurance
• Preparation of assets ready for on-site installation

That off-site methodology is what distinguishes PACE from a conventional on-site delivery contract, and it matters more in a radiologically controlled environment where on-site working time is costly and tightly constrained.

Sellafield’s off-site construction methodology, prefabrication, inspection, and staged preparation before on-site installation, draws on the same disciplines that underpin advanced nuclear engineering for new-build projects, where modular construction is promoted precisely because it reduces on-site radiological exposure and accelerates overall programme delivery.

The consolidation of two procurement streams into one is the signal worth reading here. Sellafield is shifting from project-by-project contracting toward a programme-scale model, choosing long-term contractor relationships over repeated competitive re-tendering across a fragmented supply chain.

For investors and sector observers, the structure matters as much as the headline value. A 15-year integrated framework creates multi-year revenue visibility for the preferred suppliers and locks in a particular approach to nuclear asset management at the UK’s most complex site well into the next decade.

Lot 1 and Lot 2: who won what, and for how much

The framework splits cleanly into two lots, and the value arithmetic confirms the total is fully accounted for. Lot 1 carries a maximum value of £2.1 billion, Lot 2 up to £1.5 billion, and the two sum precisely to the £3.6 billion ceiling.

Lot 1 has gone, on a preferred-supplier basis, to OneAxIoM, a joint venture between Amentum Clean Energy Limited and Mitie Ltd, supported by supply chain partners Assystem and Mott MacDonald. The scope covers process and mechanical handling nuclear facilities across the Spent Fuel Management and Retrievals East River area. OneAxIoM carries forward the partnership from OneAIM, the predecessor Amentum and Mitie joint venture that delivered the Integrated Asset Care framework.

Lot 2 has been awarded to HOCHTIEF Infrastructure UK, a subsidiary of Germany’s HOCHTIEF AG, which is majority-owned by Spanish group ACS (Actividades de Construcción y Servicios, S.A.). Its scope covers Special Nuclear Materials, nuclear infrastructure, and remediation, much of it in operational and radiologically controlled environments demanding the highest safety and technical standards.

According to Amentum, OneAxIoM’s remit under Lot 1 spans the full asset lifecycle:

• Engineering and design
• Procurement
• Installation and plant modification
• Project management and controls
• Commissioning
• Dismantling and removal
• Ongoing asset maintenance and care

An existing facility in Egremont, West Cumbria is earmarked for refurbishment to support Lot 1, building on infrastructure established under the predecessor framework. HOCHTIEF’s Lot 2 partners are still evaluating potential new off-site locations, with the stated aim of generating local employment and business opportunities in the region.

Both lots remain at preferred supplier or identified partner stage as at 30 September 2026, with formal awards subject to finalisation.

The £2.1 billion weighting toward Lot 1 tells you where Sellafield’s most resource-intensive near-term challenge sits. Managing process and mechanical handling for spent fuel is the single largest cost driver in this framework, and OneAxIoM’s incumbency reduces transition risk while concentrating that responsibility in one joint venture.

The spent fuel management mission under Lot 1 sits at the intersection of decommissioning and resource recovery: nuclear fuel recycling at commercial scale has evolved from a linear waste disposal model into one where irradiated material is increasingly treated as a recoverable asset, a shift that informs how Sellafield prices and structures long-duration asset care contracts.

Sellafield’s place in the UK nuclear landscape and why this contract is different

To understand why a £3.6 billion asset care framework carries strategic weight, you have to understand the site it serves. Sellafield, in Cumbria, is the largest nuclear complex in Western Europe, spanning over 1,000 buildings and missions that reach back to the 1950s.

Those missions are unusually varied. The site handled Magnox reprocessing, operated the Thermal Oxide Reprocessing Plant (THORP), runs nuclear waste treatment, and manages legacy defence-related facilities dating from the era when plutonium was produced for weapons purposes. Sellafield Ltd operates the site as a wholly-owned subsidiary of the Nuclear Decommissioning Authority (NDA).

Sellafield’s Special Nuclear Materials scope under Lot 2 sits within a broader international pivot: plutonium disposal strategies at legacy sites worldwide are shifting from recycling pathways toward permanent disposal solutions, a transition that shapes both the technical demands on contractors and the long-run cost profile of sites like Sellafield.

PACE departs from standard government procurement in two ways: the up-to-15-year framework horizon, and the off-site construction methodology built into the delivery model. The closest structural precedent sits on the same site, in Sellafield’s Programme and Project Partners (PPP) framework, a multi-contractor, multi-decade vehicle designed to provide stability and sustained supply chain investment.

The partner mix also reflects how globalised the specialist nuclear supply base has become. Amentum brings US-headquartered nuclear engineering, HOCHTIEF Infrastructure UK German-parentage construction, and Mitie, Assystem and Mott MacDonald UK facilities and engineering expertise.

The NDA’s programme context

PACE aligns directly with the NDA’s multi-decade decommissioning programme. The 15-year duration through 2041 matches the long-run timelines of Sellafield’s asset management and decommissioning obligations, embedding the framework within the government’s strategic effort to reduce nuclear liabilities.

Both lots cover missions central to that programme:

• Spent fuel management and retrievals
• Special nuclear materials management
• Remediation of contaminated infrastructure
• Ongoing asset care of operational facilities

The scale of the estate is what makes long-duration contracting the established model rather than the exception. A 15-year framework is not gold-plating; specialist contractors need multi-year revenue visibility to justify investment in the skills, equipment, and off-site fabrication capacity that work in radiologically controlled environments demands. International analogues at US sites such as Hanford and Savannah River follow the same logic of programme-scale, integrated contracting.

What comes next as preferred supplier status moves toward contract award

The preferred supplier designations are a significant milestone, but they are not the finish line. As at 30 September 2026, both lots sit at preferred supplier or identified partner stage, with formal contract awards subject to finalisation of contractual arrangements.

Two infrastructure decisions remain outstanding. Under Lot 1, the plan to refurbish the Egremont facility in West Cumbria still has to be confirmed. Under Lot 2, HOCHTIEF and its partners are still evaluating potential new off-site locations, and both decisions will shape the regional economic footprint and the delivery model going forward.

The regional dimension is real but not yet quantified. Sellafield is a dominant employer in West Cumbria, the Egremont refurbishment represents a tangible infrastructure commitment under Lot 1, and Lot 2 is explicitly expected to generate local employment and business opportunities. No detailed job numbers or regional economic figures have been published alongside the announcement.

For investors and sector observers, the gap between preferred supplier designation and formal award is where the real commercial work happens. That is the window in which contract terms are finalised and the full risk and reward structure of a 15-year, £3.6 billion commitment becomes binding.

The read to take from this is straightforward: PACE is not yet a signed contract. The preferred supplier status is a major step, but the next milestone to watch is formal contractual close for both lots.

A £3.6 billion commitment that reshapes Sellafield’s contractor landscape through 2041

Three structural features make PACE a consequential procurement rather than a routine award. It consolidates two predecessor frameworks into one, it commits to a 15-year duration that gives specialist suppliers multi-year visibility, and it embeds off-site construction methodology into nuclear asset management at scale.

Those features come with a familiar trade-off. Long-duration frameworks of this type, seen in precedents such as PPP and US programmes at Hanford and Savannah River, concentrate responsibility within a small set of major contractors. That supports coordinated delivery but reduces competitive tension across a 15-year horizon.

The PACE framework’s integration of asset creation and asset care under a single long-duration vehicle mirrors a logic visible elsewhere in global nuclear programmes: fleet-based nuclear construction, where a consistent contractor relationship across many facilities drives down unit costs and embeds institutional knowledge that would be lost under project-by-project re-tendering.

The forward signal is the more important takeaway. The choice of a single integrated framework over separate procurement streams indicates Sellafield’s strategy has shifted toward programme continuity over competitive flexibility.

For anyone tracking UK nuclear infrastructure spending or decommissioning market dynamics, PACE sets a reference point. This is the scale, the structure, and the partner profile that long-duration nuclear asset management contracts at a complex legacy site look like in 2026, and it is worth treating as a template signal rather than a one-off award.