Windscale fire
The Windscale fire of 10 October 1957 was the worst nuclear accident in Great Britain's history, ranked in severity at level 5 out of a possible 7 on the International Nuclear Event Scale. The fire took place in Unit 1 of the two-pile Windscale facility on the northwest coast of England in Cumberland (now Sellafield, Cumbria). The two graphite-moderated reactors, referred to at the time as "piles", had been built as part of the British 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 there was a release of radioactive contamination that spread across the UK and Europe. Of particular concern at the time was the radioactive isotope iodine-131, which may lead to cancer of the thyroid, and it has been estimated that the incident caused 240 additional cancer cases. No one was evacuated from the surrounding area, but there was a worry that milk might be dangerously contaminated. Milk from about 500 km2 of nearby countryside was diluted and destroyed for about a month. A 2010 study of workers directly involved in the cleanup found no significant long term health effects from their involvement.
After the Second World War, the British government embarked on a programme to build nuclear weapons. Skipping the lower-performance uranium-based weapons in favour of those based on plutonium, a plutonium-breeding reactor system was designed to produce this material. The design was based on the graphite-moderated B Reactor built at the Hanford Site, which was known to British physicists who had been involved in the Manhattan Project during the war. The reactors were built in a short time near the village of Seascale, Cumberland. They were known as Windscale Pile 1 and Pile 2, housed in large concrete buildings a few hundred feet apart.
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