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Windscale Advanced Gas Cooled Reactor
The Windscale Advanced Gas Cooled Reactor (WAGR) was a nuclear power plant constructed on the Sellafield nuclear site in Cumbria, England.
1. History
Commissioned in 1962, the structure was the prototype for the advanced gas-cooled reactor, the United Kingdom's second generation of commercial nuclear reactors. The station had a rated thermal output of approximately 100 MW and 30 MWe. The WAGR spherical containment, known colloquially as the "golfball", is one of the iconic buildings on the site. Construction was carried out by Mitchell Construction. This reactor was shut down in 1983, and was subsequently the subject of a pilot project to demonstrate techniques for safely decommissioning a nuclear reactor.
1. Role
While Windscale was described as a 'prototype advanced gas-cooled reactor' by the United Kingdom Atomic Energy Authority, the authors of a British Nuclear Energy Society conference paper state that the reactor was not intended to be a prototype, but rather a test bed for the fuel element of the APG program. The Windscale reactor differed from the commercial reactors in the following aspects:
reactor scale was much smaller (30 MWe against 600 MWe) the reactor pressure vessel was of stainless steel, unlike the prestressed concrete vessels used in the commercial reactors the gas temperature, at 500 °C (932 °F), was lower than the commercial design, at 640 °C (1,184 °F) the reactor fuel element used 18-pin clusters, unlike the 36-pin clusters used in the commercial reactors The paper authors state that the Windscale and commercial reactor designs were in fact different in almost every respect.
1. References
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Sellafield
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 one of the world's worst nuclear incidents. This was the Windscale fire which occurred when uranium metal fuel ignited inside Windscale Pile no.1. Radioactive contamination was released into the environment, which it is now estimated caused around 240 cancers in the long term, with 100 to 240 of these being fatal. The incident was rated 5 out of a possible 7 on the International Nuclear Event Scale.
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Windscale Piles
The Windscale Piles were two air-cooled graphite-moderated nuclear reactors on the Windscale nuclear site in Cumberland (now known as Sellafield site, Cumbria) on the north-west coast of England. The two reactors, referred to at the time as "piles", were built as part of the British post-war atomic bomb project and produced weapons-grade plutonium for use in nuclear weapons.
Windscale Pile No. 1 became operational in October 1950 followed by Pile No. 2 in June 1951. They were intended to last five years, but operated for seven until shut down following the Windscale fire on 10 October 1957. Nuclear decommissioning operations commenced in the 1980s and are estimated to last beyond 2040. Visible changes have been seen as the chimneys were slowly dismantled from top-down; Pile 2's chimney being reduced to the height of adjacent buildings in the early 2000s. However, the demolition of pile 1 chimney has taken much longer as it was significantly contaminated after the 1957 fire. The reactor cores still remain to be dismantled.
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Windscale fire
The Windscale fire of 10 October 1957 was the worst nuclear accident in the United Kingdom's history, and one of the worst in the world, ranked in severity at level 5 out of 7 on the International Nuclear Event Scale. The fire was in Unit 1 of the two-pile Windscale site (now Sellafield) on the north-west coast of England in Cumberland. The two graphite-moderated reactors, referred to at the time as "piles", had been built as part of the British post-war atomic bomb project. Windscale Pile No. 1 was operational in October 1950, followed by Pile No. 2 in June 1951.
The fire burned for three days and released radioactive fallout which spread across the UK and the rest of Europe. The radioactive isotope iodine-131, which may lead to cancer of the thyroid, was of particular concern at the time. It has since come to light that small but significant amounts of the highly dangerous radioactive isotope polonium-210 were also released. Calculations based on the amount of radiation released estimate that the accident may have caused 190 cases of cancer, with around 100 of these being fatal, however recent epidemiological studies indicate that the accident caused fewer cases of cancer than predicted.
At the time of the incident, no one was evacuated from the surrounding area, but milk from about 500 km2 (190 square miles) of the nearby countryside was destroyed for about a month afterward due to concerns about it being contaminated with iodine-131. The UK government played down the events at the time, and reports on the fire were subject to heavy censorship, as Prime Minister Harold Macmillan feared the incident would harm British-American nuclear relations.
The event was not an isolated incident; there had been a series of radioactive discharges from the piles in the years leading up to the accident. In early 1957, there had been a leak of radioactive material in which strontium-90 was released into the environment. Like the later fire, this incident was covered up by the British government. Later studies on the release of radioactive material due to the Windscale fire revealed that much of the contamination had resulted from such radiation leaks before the fire.
A 2010 study of workers involved in the cleanup of the accident found no significant long-term health effects from their involvement.
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Calder Hall nuclear power station
Calder Hall Nuclear Power Station is a former Magnox nuclear power station at Sellafield in Cumbria in North West England. Calder Hall was the first full-scale nuclear power station to enter operation in the West, and was the sister plant to the Chapelcross plant in Scotland. Both were commissioned and originally operated by the United Kingdom Atomic Energy Authority. The primary purpose of both plants was to produce weapons-grade plutonium for the UK's nuclear weapons programme, but they also generated electrical power for the National Grid.
Decommissioning by Sellafield Ltd started in 2005. The site is partially demolished and is expected that only the reactor cores and associated radiation shielding will remain by 2027, when it will enter a period of extended care and maintenance using the "safestore" principle, before final demolition.