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 fish was 510,000 Bq/kg detected in another greenling. On the sea floor a net was installed by TEPCO, in order to prevent migrating fish to escape from the contaminated area. As of July 2011, the Japanese government has been unable to control the spread of radioactive material into the nation's food, and "Japanese agricultural officials say meat from more than 500 cattle that were likely to have been contaminated with radioactive caesium has made its way to supermarkets and restaurants across Japan". On 22 July it became known that at least 1400 cows were shipped from 76 farms that were