Caesium out of the body relatively quickly in sweat and urine. The remaining 90% has a biological half-life between 50 and 150 days. Radiocaesium follows potassium and tends to accumulate in plant tissues, including fruits and vegetables. Plants vary widely in the absorption of caesium, sometimes displaying great resistance to it. It is also well-documented that mushrooms from contaminated forests accumulate radiocaesium (caesium-137) in the fungal sporocarps. Accumulation of caesium-137 in lakes has been a great concern after the Chernobyl disaster. Experiments with dogs showed that a single dose of 3.8 millicuries (140 MBq, 4.1 μg of caesium-137) per kilogram is
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