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
Fukushima Daiichi nuclear disaster experimental agricultural research fields around the affected area) has noted that "the fallout was found at the surface of anything exposed to air at the time of the accident. The main radioactive nuclides are now caesium-137 and caesium-134", but these radioactive compounds have not dispersed much from the point where they landed at the time of the explosion, "which was very difficult to estimate from our understanding of the chemical behavior of cesium". In February 2018, Japan renewed the export of fish caught off Fukushima's nearshore zone. According to prefecture officials, no seafood had been found with radiation levels exceeding