What is the First Generation Magnox Storage Pond?
The First Generation Magnox Storage Pond (FGMSP) is one of 4 older pond and silo facilities on the Sellafield site.
Today, the pond is part of our high hazard risk reduction programme.
The open-air storage pond was built and commissioned in the 1950s to support the UK’s early nuclear programme.
It was used to store and process used Magnox fuel after it had been removed from the reactors.
The construction of the First Generation Magnox Storage Pond in the late 1950s
The facility includes
-
an inlet building where fuel arrived
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an open-air outdoor storage pond
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an area where fuel is handled in water (wet bays)
In the 1960s, it was expanded so it could store more fuel and improve how the fuel covering (cladding) was removed.
The pond operated for over 30 years. During that time, it stored and processed about 27 tonnes of fuel (around 2.5 million fuel rods).
The facility continued to operate until a replacement plant, the Fuel Handling Plant, opened in 1986. The final fuel was received into the facility in 1992.
What did it do?
The pond was designed to receive, store and prepare used nuclear fuel from Magnox power stations in the UK. This including the operation of nearby Calder Hall, the world’s first commercial sized nuclear power station.
The fuel was stored underwater to
- keep it cool
- keep it safe
It was meant to stay in the pond for about 90 days. After that
- the outer metal layer (called cladding) was removed
- the fuel was sent for chemical reprocessing
At its busiest, the pond handled hundreds of fuel elements every day to keep up with power stations across the UK.
What changed?
In 1974, the reprocessing plant shut down for an extended period of time due to an increased electricity demand.
This meant fuel had to stay in the pond much longer than planned.
Over time
- the metal fuel started to break down (corrode)
- sludge began to form
- radiation levels increased
- it became harder to see and work safely underwater
How was this managed?
In 1976, special containers called zeolite skips were added to the pond.
These worked like sponges
- pond water was passed through them
- they removed caesium from the water
- they also helped trap some sludge
Operational records show the skips were used until 1985. After this, a new plant called the Site Ion exchange Effluent Plant (SIXEP) began operating at Sellafield, cleaning radioactive water on a much larger scale.
Zeolite skips in the pond
Build-up of waste
Over the years, different types of waste built up in the pond, including
- sludge from corroded fuel
- old fuel and fuel parts
- zeolite skips
- debris from outside
This made the pond more hazardous and harder to clean up.
How do we get waste out of the pond?
Removing waste from the pond is one of the most complex clean-up tasks at Sellafield.
The pond was not designed to be emptied. This makes the job harder. It means we need specialist equipment, careful planning and new ways of working to remove waste safely.
The task is being delivered in stages.
Accessing the waste to inspect it
We use specialist tools and equipment to reach waste stored underwater, including sludge, solid materials and fuel.
Much of the waste is hard to reach because of its age and condition. That means most of the work is done remotely using specially designed tools and machines.
This helps keep employees safe and allows work to continue in difficult conditions.
Retrieving and packaging materials
Waste is carefully removed and placed into purpose-built containers. These containers are designed to keep the material safe.
Each type of material must be removed safely and treated in different ways.
Moving waste to modern safe storage
Once packaged, the waste is moved to modern storage buildings, such as the Intermediate Storage Facility (ISF) on the Sellafield site. It can then be stored safely for a long time.
Key improvements
To help keep the facility safe as it gets older, improvements are needed. These also ensure it is easy to maintain.
These include
- an emergency pumping system, which was added to address issues with old pipes and systems
- a pond cleaning system, which was installed to clean the water and reduce radiation levels for workers
Progress so far
Good progress has already been made across waste retrieval, processing and supporting capabilities
Waste and skip removal
Fuel 70 fuel skips have been exported to the Fuel Handling Plant (FHP), removing around 120 tonnes of waste from the pond.
Zeolite 35 zeolite skips have been exported since 2024 via the Self-Shielded Box (SSB) route to the Interim Storage Facility (ISF). This is around a quarter of the total number. Over 230 remain.
Storage of the repackaged Zeolite skips in the Interim Storage Facility
Redundant equipment Nine redundant fuel receipt containers (magazines) have been cleared of fuel debris and safely exported from the facility.
Sludge retrieval and pond condition
Targeted areas of the pond have been cleared of sludge. This creates space to organise remaining skips, help reduce risk. This work has so far covered almost a quarter of the pond floor.
A new high-performance pump has been installed and is being tested. Early results show significantly faster sludge removal compared to the previous system.
Technology and innovation
A quadrupedal (four-legged) robot is being used to support radiological monitoring. This helps reduce worker exposure and improves how work is carried out.
Key milestones
Progress has been built over time through a series of important developments
Early operations Sludge was initially removed using an eductor pump. This has since been replaced by a more effective high-performance system.
2014 The inlet building was converted into an export facility. This provides a safe, shielded route for skips containing fuel, fuel materials and zeolite to leave the pond.
2015 Sludge retrieval began, with material sent to the Sludge Packaging Plant (SPP1) for safe storage ahead of further treatment.
2016 Fuel removal operations began, with fuel skips exported to the FHP for safer storage.
2024 Introduction of Self-Shielded Boxes (SSBs) for transporting zeolite skips to the ISF.
2025 The SSB method was extended to fuel and fuel material skips, improving safety and efficiency.
Next steps
Work to empty the pond will continue in stages and is expected to continue into the 2040s.
Sludge removal and treatment
Sludge from the pond and bays will continue to be removed and sent to the Sludge Packaging Plant (SPP1).
It will then be treated and placed into large containers so it can be safely transported for long-term storage.
Fuel and waste removal
Remaining fuel and other waste are organised into skips using Remotely Operated Vehicles (ROVs). They are also used for mapping and locating items in the pond.
This inventory will be removed and sent to the Fuel Handling Plant (FHP) or Interim Storage Facility (ISF) in Self-Shielded Boxes (SSBs). These facilities offer safer storage for nuclear waste before further treatment or disposal.
Zeolite skips
Zeolite skips are being exported to the Intermediate Storage Facility (ISF) in Self-Shielded Boxes (SSBs).
The Interim Storage Facility
As fuel is consolidated from various skips into one, it leaves some skips empty. Because these no longer contain waste, they can be washed and exported in a sealed bag to the Skip Size Reduction Facility (SSRF) prior to final disposal.
Preparing the pond floor
We use the Bulk Sludge Retrieval Tool (BSRT) to retrieve sludge. ROVs help us clear space on the pond floor. This makes it easier to organise skips and access remaining waste.