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 just like caesium-137 as indicated on an earlier map. But I-131 was also found south of the plant at relatively high levels, even higher than those of caesium-137 in coastal areas south of the plant. According to the ministry, clouds moving southwards apparently caught large amounts of iodine-131 that were emitted at the time. The survey was done to determine the risks for thyroid cancer within the population. On 31 October the Japanese ministry of Education, Culture, Sports, Science and Technology released a map showing the contamination of radioactive tellurium-129m within a 100-kilometer radius around the Fukushima No. 1 nuclear