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
Timeline of the Fukushima Daiichi nuclear disaster of a new leak of radioactive water into the sea. The Itabashi Ward Office announces that a concentration of caesium-134 at 2,700 becquerels per kilogram – in excess of the government's provisional limit – was detected in tea processed from leaves picked on 9 May in Tokyo. The water decontamination and water recycling systems are now both functional. 100% recycled water is now used for reactor cooling, and no additional volume of contaminated water is being generated. Radioactive caesium-137 is found in Tokyo's tap water for the first time since April. Radioactive caesium from Fukushima was expected to enter the