Sellafield, formerly known as Windscale, is a large multi-function nuclear site close to Seascale on the coast of Cumbria, England. As of August 2022, primary activities are nuclear waste processing and storage and nuclear decommissioning. Former activities included nuclear power generation from 1956 to 2003, and nuclear fuel reprocessing from 1952 to 2022. The licensed site covers an area of 265 hectares (650 acres), and comprises more than 200 nuclear facilities and more than 1,000 buildings. It is Europe's largest nuclear site and has the most diverse range of nuclear facilities in the world on a single site. The site's workforce size varies, and before the COVID-19 pandemic was approximately 10,000 people. The UK's National Nuclear Laboratory has its Central Laboratory and headquarters on the site. Originally built as a Royal Ordnance Factory in 1942, the site briefly passed into the ownership of Courtaulds for rayon manufacture following World War II, but was re-acquired by the Ministry of Supply in 1947 for the production of plutonium for nuclear weapons which required the construction of the Windscale Piles and the First Generation Reprocessing Plant, and it was renamed "Windscale Works". Subsequent key developments have included the building of Calder Hall nuclear power station - the world's first nuclear power station to export electricity on a commercial scale to a public grid, the Magnox fuel reprocessing plant, the prototype Advanced Gas-cooled Reactor (AGR) and the Thermal Oxide Reprocessing Plant (THORP). Decommissioning projects include the Windscale Piles, Calder Hall nuclear power station, and historic reprocessing facilities and waste stores. The site is owned by the Nuclear Decommissioning Authority (NDA) which is a non-departmental public body of the UK government. Following a period 2008–2016 of management by a private consortium, the site was returned to direct government control by making the Site Management Company, Sellafield Ltd, a subsidiary of the NDA. Decommissioning of legacy facilities, some of which date back to the UK's first efforts to produce an atomic bomb, is planned for completion by 2120 at a cost of £121 billion. Sellafield was the site in 1957 of the UK's worst nuclear accident. This was the Windscale fire which occurred when uranium metal fuel ignited inside Windscale Pile no.1. Radioactive contamination was released into the environment, it has been estimated that this caused around 240 cancers in the long term, with 100 of these predicted to be fatal, though epidemiological studies have failed to find any such increase. The incident was rated 5 out of a possible 7 on the International Nuclear Event Scale.
Site development
Royal Ordnance Factory The site was established with the creation of Royal Ordnance Factory ROF Sellafield by the Ministry of Supply in 1942; built by John Laing & Son at the hamlet of Low Sellafield. The nearby sister factory, ROF Drigg, had been constructed in 1940, 3 miles (5 km) to the south-east near the village of Drigg. Both sites were classed as Explosive ROFs, producing high-explosive at ROF Drigg, and propellant at ROF Sellafield. They were built in this location to be remote from large centres of population because of the hazardous nature of the process, and to reduce the risk of World War II enemy air attack. There were also existing rail links, and a good supply of high quality water from Wastwater. Production ceased at both factories immediately following the defeat of Japan.
Start of nuclear activity
After the War, the Sellafield site was briefly in the ownership of Courtaulds for development as a rayon factory, but was re-acquired by the Ministry of Supply for the production of plutonium for nuclear weapons. Construction of the nuclear facilities commenced in September 1947 and the site was renamed Windscale Works. The building of the nuclear plant was a huge construction project, requiring a peak effort of 5,000 workers. The two air-cooled and open-circuit, graphite-moderated Windscale reactors (the "Windscale Piles") and the associated First Generation Reprocessing Plant, producing the first British weapons grade plutonium-239, were central to the UK nuclear weapons programme of the 1950s. Windscale Pile No.1 became operational in October 1950, just over three years from the start of construction, and Pile No.2 became operational in June 1951.
Calder Hall power station
With the creation of the United Kingdom Atomic Energy Authority (UKAEA) in 1954, ownership of Windscale Works passed to the UKAEA. At this time the site was being expanded across the River Calder where four Magnox reactors were being built to create the world's first commercial-scale nuclear power station. This became operational in 1956 and was the world's first nuclear power station to export electricity on a commercial scale to a public grid. The whole site became known as "Windscale and Calder Works".
British Nuclear Fuels Ltd (BNFL) Following the break-up of the UKAEA into a research division (UKAEA) and a newly created company for nuclear production British Nuclear Fuels Ltd (BNFL) in 1971, a major part of the site was transferred to BNFL ownership and management. In 1981 BNFL's Windscale and Calder Works was renamed Sellafield as part of a major reorganisation of the site and there was a consolidation of management under one head of the entire BNFL Sellafield site. The remainder of the site remained in the hands of the UKAEA and was still called Windscale.
Reprocessing Sellafield was the centre of UK nuclear reprocessing operations, which separated the uranium and plutonium from minor actinides and fission products present in spent nuclear fuel. The uranium could be used in the manufacture of new nuclear fuel, or in applications where its density was an asset. The plutonium was originally used for weapons, and later in the manufacture of mixed oxide fuel (MOX) for thermal reactors. Reprocessing ceased on 17 July 2022, when the Magnox Reprocessing Plant completed its last batch of fuel after 58 years of operation. In January 2025, the government announced that the 140 tonnes civil plutonium stockpile produced by reprocessing, originally considered a valuable asset, would be immobilised and eventually disposed of in a geological disposal facility, rather than used to produce MOX fuel which was evaluated as an uneconomic option. Sellafield Site has had three separate fuel reprocessing facilities:
… excerpt ends here. Continue reading the full article.
