Windscale

In 1957 one of the twin military reactors caught fire, resulting in a release of radionuclides into the environment. It has been claimed that this was the worst nuclear accident until Three Mile Island (TMI) in 1979. However since neither event resulted in immediate casualties (unlike for example the accident at the SL-1 plant in Idaho which killed the three operators, or the prompt criticality which killed Louis Slotin in 1946) this assertion is dependent upon epidemiological assessments. Both were later overshadowed by the Chernobyl accident in 1986. An estimated 750 terabecquerels (TBq) (20,000 curies) of radioactive Iodine-131 were released, and milk and other produce from the surrounding farming areas had to be destroyed. For comparison, 250,000 terabecquerels (7 million curies) of Iodine-131 were released by Chernobyl, and only 0.55 terabecquerels (15 curies) of Iodine-131 by TMI. In comparing only Iodine-131 released as a measure of the severity of an accident care must be taken, since it is estimated that TMI released 480 petabecquerels of radioactive noble gases, and had a low Iodine-131 release.