Alkali metal from the Chernobyl accident. Caesium-137 undergoes high-energy beta decay and eventually becomes stable barium-137. It is a strong emitter of gamma radiation. Caesium-137 has a very low rate of neutron capture and cannot be feasibly disposed of in this way, but must be allowed to decay. Caesium-137 has been used as a tracer in hydrologic studies, analogous to the use of tritium. Small amounts of caesium-134 and caesium-137 were released into the environment during nearly all nuclear weapon tests and some nuclear accidents, most notably the Goiânia accident and the Chernobyl disaster. As of 2005, caesium-137 is the principal source
Radiation effects from the Fukushima Daiichi nuclear disaster radioactivity before consumption. Also in July citizens groups reported that a survey of soil at four places in the city of Fukushima taken on 26 June proved that all samples were contaminated with radioactive caesium, measuring 16,000 to 46,000 becquerels per kilogram and exceeding the legal limit of 10,000 becquerels per kg, A study published by the PNAS found that caesium 137 had "strongly contaminated the soils in large areas of eastern and northeastern Japan." After the find of 8,000 becquerels of caesium per kilogram in wild mushrooms, and a wild boar that was found with radioactivity amounts about 6