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.