Sellafield Ltd priorities and progress

About Sellafield Ltd

We are delivering against national safety, security and energy needs. In operating, developing, and decommissioning the Sellafield site, we are also delivering the largest environmental restoration project in Europe.

In short, we solve complex nuclear, engineering, and infrastructure challenges for the UK every single day.

In the past, we have been responsible for breakthroughs such as the world’s first full-scale commercial nuclear power station, and today we are helping to keep lights on across the UK by safely receiving and storing spent nuclear fuel from the UK’s fleet of power stations.

Sellafield is the only site in the country that can safely manage all forms of nuclear waste, with our teams finding new ways to ensure it is kept safe until a permanent disposal facility is ready.

We are also guardians of the UK’s largest stockpile of nuclear materials.

Our world-class engineers and nuclear professionals tackle these challenges with the same spirit of innovation that has always run through our organisation.

All our activities are driven by a single purpose: to create a clean and safe environment for future generations.

We deliver on that purpose while providing value to:

• Ourour people – helping them to grow, develop and flourish

• Ourour communities – creating a positive social impact in West Cumbria, Warrington and beyond

• Ourour industry – supporting the nation’s nuclear infrastructure, completing our decommissioning mission, and shaping best-practice standards.

Priorities

NDA strategy

We are one1 of four4 vital component parts of the Nuclear Decommissioning Authority (NDA) Group, which shares a collective mission to safely decommission the UK’s legacy sites and facilities.

The Sellafield Ltd priorities are embedded within the NDA strategy.

Sellafield Ltd strategy

Our strategy outlines the type of organisation Sellafield wants to be, whilst clearly setting our 2020 - 2025 objectives.

Progress overview

An overview of our past progress across all our activities, within previous financial years can be found in our catalogue of annual review documents.

High-hazard risk reduction priorities and progress

Among the more than 200 nuclear facilities on the site are some of the most hazardous nuclear buildings in the country – our legacy ponds and silos.

These legacy facilities include:

• Pile Fuel Storage Pond (PFSP)

• Pile Fuel Cladding Silo (PFCS)

• First Generation Magnox Storage Pond (FGMSP)

• Magnox Swarf Storage Silo (MSSS)

They present complex decommissioning challenges and getting the waste out of them remains one of our top priorities. By doing so we are actively reducing these hazards and protecting the environment.

To support our retrievals work, we have continued to maintain the integrity of the facilities, and deliver the projects required to establish the required waste routes.

Pile Fuel Storage Pond

Built between 1947 and 1949, the Pile Fuel Storage Pond (PFSP) is the oldest nuclear pond on the Sellafield site. It is also the largest open air nuclear fuel storage pond in the world.

It provided storage, cooling and decanning of irradiated fuel and isotopes from the two2 Windscale Pile reactors in preparation for reprocessing.

Although taken out of operation in 1962 it continued to receive irradiated fuel and miscellaneous intermediate level waste (ILW) from the UK nuclear programme until the early 1970s.

By the mid-1970s, the import of waste ceased and the plant, with its inventory, was placed into a passive care and maintenance regime.

The priority

Retrievals from the PFSP commenced in the 1990s. The facility is now entering its final phase of retrievals.

Our priority today is to continue to retrieve the remaining inventory of waste in the pond – solid ILW, sludge, sludge debris and fuel materials - so it can be placed treated appropriately and placed into safe, modern storage.

Our progress

76% of the radioactivity has now been removed from the PFSP. WeWe’re are accelerating the removal of ILW with a series of decommissioning dives which started in 2023.

We have established proven waste routes for the waste coming out of the pond (whilst continuing to explore further future opportunities).

Pile Fuel Cladding Silo

Commissioned in 1952, The Pile Fuel Cladding Silo (PFCS), is the oldest store on the Sellafield site. The six-compartment silo was built to store cladding from nuclear fuel used by the Windscale Piles.

As the UK’s civil nuclear power industry grew, the silo also received and stored cladding from used Magnox fuel from power stations around the country.

In 1972, the facility was full and placed into care and maintenance.

The priority

We started retrievals from the PFCS in August 2023.

Our priority today is to continue waste retrievals from the legacy silo so it can be placed a safe and modern store called the Box Encapsulation Plant Product Store (BEPPS).

Our end goal is to empty the facility.

Our progress

We met our retrievals target for 2024/25 by retrieving enough waste to fill 18 3-metre cubed storage boxes.

As we move out of the early retrievals phase of this project, our focus now is to safely accelerate the pace of routine retrievals from PFCS.

First Generation Magnox Storage Pond

Constructed in the 1950’s, the First Generation Magnox Storage Pond (FGMSP) was commissioned to receive and store irradiated fuel from Magnox reactors and remove the fuel cladding prior to fuel being reprocessed.

The legacy pond predominantly received fuel from Calder Hall, the UK’s first nuclear power station, on the Sellafield site. However, the pond also received and processed fuel from the UK’s fleet of 26 reactor units, Latina in Italy and Tokai in Japan.

The plant operated safely for over 30 years with the final fuel being received into the facility in 1992. During this period 27,000 tonnes of fuel were processed – nearly 2.5 million fuel rods.

The priority

We started retrievals from the FGMSP in 2015.

Our priority today is to continue with the retrievals of the sludge, intermediate level waste (ILW) and spent fuel within the pond. The various forms of retrieved waste will be treated appropriately and placed in safe, modern stores.

Our progress

We are currently in the bulk waste retrievals phase of this project. We successfully removed the first zeolite skip from the pond in 2024.

The solid waste retrieved from the pond is being transferred and self-shielded boxes and safely-stored in a new purpose-built legacy facility called the Intermediate Storage Facility (ISF).

Magnox Swarf Storage Silo

The Magnox Swarf Storage Silo (MSSS) is the most hazardous building on the Sellafield site.

The silo contains approximately 10,000 cubic metres of historic waste within 22 individual compartments of the silo.

MSSS was built more than 50 years ago for the underwater storage of Magnox fuel cladding (or swarf) that was removed from used nuclear fuel rods. This allowed the rods to be reprocessed.

It received swarf from the First Generation Magnox Storage Pond and the Fuel Handling Plant, along with a range of other items of intermediate level waste.

The final batch of waste was tipped into the legacy silo in June 2000, at which point the facility was put under a regime of care and maintenance.

The priority

We started to retrieve the stored waste from Magnox Swarf Storage Silo (MSSS) in 2022.

Our priority today is to continue to retrieve the stored waste and silo liquor so it can be placed in a safe and modern store. Most of the solid waste from MSSS will be placed in the Box Encapsulation Plant Product Store (BEPPS).

There is an ongoing leak of radioactive liquid from the MSSS facility at Sellafield into the ground. The risk to the off-site environment and public is expected to be very low. There is no risk to public water supply boreholes from the leak.

Working closely with the Environment Agency (EA) and the Office of Nuclear Regulation (ONR), the priority for our teams is to continue to monitor the leak. We must do this whilst continuing to retrieve waste from the silo and exploring the possible implementation of measures to reduce the consequences of the leak. Read more about the leak.

Our progress

Waste retrievals were temporarily halted but successfully restarted in February 2024. This was following the successful commissioning of the new Nitrogen Generation Plant and the completion of some electrical repairs needed on the Silo Emptying Plant machine.Machine.

The second Silo Emptying Plant machineMachine has been installed. Preparation and commissioning work on the machine is being conducted inside the silo. Once completed, retrieval operations will commence.

We are also continuing to closely monitor the ongoing leak of radioactive liquid from the MSSS facility. inIn 2023/24 we added sixteen16 more boreholes close to the silo to enhance this monitoring capability.

Major projects priorities and progress

In order to deliver our mission, we are building on an epic scale. In fact, we have one of the largest portfolios of complex major projects in the country.

Once established, our new fleet of nuclear facilities will support operations to ensure we can continue to keep nuclear waste and materials safe and secure.

In 2019 we formed a new model for project delivery at Sellafield, the Programme and Project Partners (PPP). We brought together KBR, Amentum, Morgan Sindall Infrastructure, Altrad Babcock, and a wider supply chain to deliver a 20-year pipeline of major infrastructure projects.

This new approach was designed to ensure faster and more effective project delivery, with greater workforce flexibility, and local economic benefit.

Some of the current major projects delivered by PPP:

• SIXEP Continuity Plant (SCP)

• Sellafield Product and Residue Store Retreatment Plant (SRP)

Many other projects that are ongoing across the Sellafield site are not delivered by PPP. While they are supported by our supply chain, they are managed within Sellafield Ltd.

SIXEP Continuity Plant

Our SIXEP Continuity Plant (SCP) will ensure the site’s existing Site Ion Exchange Effluent Plant (SIXEP) facility can continue its vital work for decades to come. 

Operational from 1985, SIXEP receives and filters contaminated water from a range of nuclear buildings and processes, so it can be safely discharged to sea. The plant is often described as the ‘kidneys’ of the Sellafield site.

Our need for SIXEP will go on beyond the original design life of the plant. Which is why we’re currently building an extension.

The new-build SCP facility is being build next door to the current SIXEP building and will ensure that we can continue to treat the water used in our processes for decades to come.

The priority

Today’s priority is to continue to meet key construction milestones to ensure we can make SCP operations by 2029.

This includes manufacturing and installing pipework, tanks, vessels, pumps and valves and eventually fitting a pipe bridge which will connect SCP with the existing SIXEP plant.

Our progress

The SCP project team recently celebrated a significant delivery milestone as they completed the manufacture of 14 bespoke pump and valve modules that will form the inner workings of the plant.

It is on course to be operational by 2029.

Sellafield Product and Residue Store Retreatment Plant

Our Sellafield Product and Residue Store Retreatment Plant (SRP) will play an essential role in managing the UK’s plutonium stockpile in support of the government’s plutonium disposition strategy.

Stored safely and securely at Sellafield since the 1940’s, the UK’s inventory of civil plutonium arose from the reprocessing of spent fuel.

In doing so we have developed world leading expertise and are recognised as the UK’s centre of excellence for plutonium management.

Once SRP becomes operational, it will receive and repackage existing special nuclear material packages from across the Sellafield site. This will ensure it can be safely stored for the next 100-years.

The priority

The priority is to progress the internal and mechanical fit-out of the facility before entering the inactive commissioning phase.

The installation of these systems is a key step in ensuring that SRP will become operational by 2028.

Our progress

In May 2025, the new-build plant hit a major milestone when its process building became weathertight.

The plant is now in a new delivery phase to progress its internal and mechanical fit-out.

The integrated glovebox systems which will be installed across the facility are currently being manufactured and tested off-site to ensure that they are ready for inactive commissioning.

The plant is on track to be commissioned in late 2028.