Windscale fire 2037. There was a release to atmosphere of radioactive material that spread across the UK and Europe. The fire released an estimated 740 terabecquerels (20,000 curies) of iodine-131, as well as 22 TBq (594 curies) of caesium-137 and 12,000 TBq (324,000 curies) of xenon-133, among other radionuclides. Later reworking of contamination data has shown national and international contamination may have been higher than previously estimated. For comparison, the 1986 Chernobyl explosion released approximately 1,760,000 TBq of iodine-131; 79,500 TBq caesium-137; 6,500,000 TBq xenon-133; 80,000 TBq strontium-90; and 6100 TBq plutonium, along with about a dozen other radionuclides in large amounts.
Isotopes of caesium not produced by nuclear weapons because Cs is created by beta decay of original fission products only long after the nuclear explosion is over. Cs also captures neutrons with a cross section of 13.00 barns, becoming medium-lived radioactive Cs. Caesium-136 undergoes beta decay (β−), producing Ba-136 directly. Caesium-137, with a half-life of 30.17 years, is one of the two principal medium-lived fission products, along with Sr, which are responsible for most of the radioactivity of spent nuclear fuel after several years of cooling, up to several hundred years after use. It constitutes most of the radioactivity still left from the