Decommissioning Sellafield is one of the UK’s most significant and technically demanding environmental challenges. Located on the Cumbrian coast in Northwest England, the site has played a pivotal role in the nation’s nuclear history – from hosting the world’s first commercial-sized nuclear power station to becoming the heart of the nation’s nuclear fuel reprocessing operations.
Today, the focus is on safely and sustainably managing its seven-decade nuclear legacy. The Design Services Alliance (DSA) was set up in 2012 to support this mission. A 15-year contract between Sellafield Ltd and key partners in the nuclear supply chain that brings together multidisciplinary expertise to support a wide range of decommissioning-related projects.
As a key delivery partner for the DSA, we’re playing a vital part in making Sellafield safer for future generations – bringing over 60 years of experience and expertise in the sector.
What is the DSA – and how does AECOM fit in?
The DSA framework is made up of two delivery alliances: the Progressive Alliance (a partnership between AECOM and Cavendish Nuclear) and AXIOM (a joint venture between Assystem, Amentum and Mott MacDonald) – and is split into four specialist engineering lots:
- Mechanical
- Electrical, Controls and Instrumentation (EC&I)
- Process
- Civil, Structural and Architectural (CS&A)
As part of the Progressive Alliance, we are the lot holder for CS&A services and share joint leadership of the Process Engineering lot.
In addition to these roles, we also provide architecture, engineering, BIM management, specialist BIM coordination and project management services for all stages of the contract projects. These range from small-scale refurbishments to major facilities valued at up to £1 billion and encompass hundreds of individual work packages.
Partnership: a vital ingredient for success
On a site as complex and tightly regulated as Sellafield, partnership is essential. The scale of the DSA projects – which includes nuclear new build, asset care, outage support, decommissioning and post-operational clean-out – requires large, multidisciplinary teams to work together over many years.
Strong collaboration helps align workstreams, meet safety case requirements, and keep delivery coordinated. The DSA framework enables this by bringing the client and contractors together under a long-term, integrated approach.
To further strengthen collaboration and improve delivery, the contract uses a range of contract types – including reimbursable, target price and fixed-price models – tailored to the size and complexity of each work package. This helps teams manage change, allocate risk appropriately and deliver better value for Sellafield Ltd. All profit is linked to performance, with incentives tied to agreed project KPIs.
While the DSA is currently active on more than 170 projects, the following are three of the most significant projects we have been involved in as part of the DSA:
1 / Designing essential infrastructure for legacy silo clean-up
The £160-million Silo Maintenance Facility (SMF) supports the safe retrieval and decontamination of hazardous waste stored in Sellafield’s Magnox Swarf Storage Silos and Pile Fuel Cladding Silos.
Delivered as part of a design and build contract, we worked within the Balfour Beatty-Babcock joint venture from concept through to detailed design as the CS&A designers.
Constructed on the site of the former Calder Hall South Cooling Towers, the facility includes a reinforced concrete process cell, decontamination areas, an import/export road bay and a series of storage zones – all housed within a steel-framed structure supporting a 63-tonne overhead crane.
The design – which was completed to level 2 BIM standards – also included external works such as drainage systems, a permanent electrical substation, a bridge culvert over an existing stream, and two pipe bridges connecting low-pressure steam and piped services to the site.
2/ Engineering remote access to one of Sellafield’s oldest waste stores
Built in the early 1950s, the Pile Fuel Cladding Silo (PFCS) is one of Sellafield’s oldest waste stores. Originally used to hold fuel cladding from the site’s first reactors, it now contains a mix of hazardous materials that must be safely retrieved and transferred to secure, modern storage – a priority for Sellafield Ltd and the Nuclear Decommissioning Authority (NDA).
We led the design of the retrieval building, supporting the project from concept through to detailed design and on-site delivery. This covered all key elements, including the piled foundations, superstructure, control room and the modular structures used to access and remove the waste.
The retrieval method uses remotely operated equipment – including a telescopic arm fitted with a ‘petal grab’ and Brokk robotics – to reach inside the silo compartments and extract the waste safely, without direct human contact.
To meet the specific challenges of the site, we designed modular systems that could be built off site, reducing construction work in a high-risk area. The project also used low-height piling rigs to reduce the risk of collapse and created systems that could be fully tested before being installed.
3/ Shaping the delivery of a critical storage facility
The BEPPS DIF BEP facility is central to Sellafield’s long-term strategy for managing intermediate-level waste retrieved from legacy ponds and silos. (This refers to waste that is radioactive enough to require shielding but not cooling.)
The project comprises two key facilities housed in the same building – the Box Encapsulation Plant (BEP) and the Box Encapsulation Plant Product Store and Direct Import Facility (BEPPS DIF) – plus supporting infrastructure including service buildings, a transporter bay, underground tunnels and a double storage vault.
We delivered the CS&A detailed design through the Design Group Partnership (DGP) for the original facilities, constructed more than 20 years ago. When the project was paused partway through construction due to changes in Sellafield’s process requirements, we remained fully involved – with team members seconded into the client’s offices to provide CS&A design support to client design teams and act as employer’s agent during construction.
We also worked alongside the contractor to maintain continuity and support coordinated delivery through to completion. The facility, which is now commissioned and operational, was designed to BIM Level 2 standards. BIM was used to support programme sequencing, coordination and cost planning too – helping to deliver this complex facility efficiently and cost-effectively.
A safer Sellafield for current and future generations
By combining long-standing nuclear expertise with truly integrated working, the DSA is well placed to support delivery on one of the UK’s most complex and highly regulated sites.
Through close partnership with Sellafield Ltd and the wider supply chain, we’re helping to reduce risks, protect the environment and deliver a safer, more sustainable legacy for the surrounding landscape, workforce and community.