The Nuclear Decommissioning Authority

The world's largest open-air fuel pond and Sellafield's oldest, began operations in 1952 after a four-year construction period. It was initially used for cooling irradiated fuel from the Windscale Piles before reprocessing.

Subsequent modifications also allowed it to receive spent fuel from the Magnox reactors at nearby Calder Hall.

An adjoining building, the decanning plant, was used for removing the fins and other metallic components surrounding the fuel elements.

The pond is divided into sections, with a series of sub-ponds known as bays which are connected under water.

Kevin Newland, Pile Fuel Storage Pond (PFSP) Technical Manager, said: "The pond is open to the elements, and so we have to be extremely cautious as we remove the contents as there is no building to contain any radioactive contamination. We need to prevent any radioactive materials being released into the environment and so we're always looking for new and innovative techniques to complete the decommissioning."

Operations were scaled down following the closure of the Windscale Pile reactors and the commissioning of the First Generation Magnox Fuel Storage Pond, although the facility was still used as a cooling and decanning facility for some materials.

When decanning stopped in 1962, the pond continued to be used as storage for fuel, contaminated items and operational waste. All operations at the pond ceased in the 1970s.

During its life, the pond processed 2,100 tonnes of pile fuel and 300 tonnes of Magnox fuel.

It now contains skips of used nuclear fuel, accumulated sludge, intermediate level waste and pond water, all of which need to be safely removed and subject to separate processes.

The area round the pond is very congested, posing practical difficulties, while levels of radiation are high.

The ultimate aim is to empty the pond and reduce the building to a slab. With a total programme cost of almost £330 million until 2025/26, work will focus on safe removal of the radioactive contents, including the sludge and spent fuel which can be processed, and the construction of a new plant for treating and storing the sludge before it is transferred to the deep Geological Disposal Facility (GDF).

Fuel retrieval milestone

Towards the end of last year, fuel was retrieved from the pond for the first time in 50 years and five years earlier than expected.

The retrieval marks an important step towards decommissioning and reflects the drive to meet the new Sellafield Performance Plan, which details the step-by-step decommissioning of the Sellafield site.

Following approval from the regulators, the half-tonne of retrieved fuel was transferred from the pond to a transport flask and exported to the modern fuel storage pond where it will be held pending final disposal.

Mark Steele, NDA's Interim Head of Programme for Sellafield, said:

"Successfully achieving this milestone in our priority work area is extremely encouraging. The combination of the expertise of the Sellafield workforce alongside targeted support from NMP to improve delivery and make the site more efficient, is exactly what we envisaged when NMP won the Sellafield contract and what the recently published Performance Plan demands across the site."

Dorothy Gradden, Head of Programme Delivery, said:

"It's the first time since 1964 that we've been in a position to safely export nuclear fuel, the majority of which was burnt in the Windscale Piles reactors. There are almost 50 skips, containing 6-12 tonnes of spent nuclear fuel, to be exported from the legacy pond."