Caesium-137 or approximately 44 μg/kg) of caesium-137 (and 950 to 1400 rads), they die within 33 days, while animals with half of that burden all survived for a year. Accidental ingestion of caesium-137 can be treated with Prussian blue, which binds to it chemically and reduces the biological half-life to 30 days. Caesium-134 and caesium-137 were released into the environment during nearly all nuclear weapon tests and some nuclear accidents, most notably the Chernobyl disaster and the Fukushima Daiichi disaster. As of 2005 and for the next few hundred years, caesium-137 is the principal source of radiation in the zone of
Koeberg Alert strontium-90, which are responsible for most of the radioactivity of spent nuclear fuel Caesium-137 beta decays to barium-137m (a short-lived nuclear isomer) then to nonradioactive barium-137, and is also a strong emitter of gamma radiation. Caesium-137 has a very low rate of neutron capture and cannot be feasibly disposed of, but must be allowed to decay. The committee is also told how both the Tweelopiespruit and Wonderfonteinspruit in the Krugersdorp-Randfontein area have been contaminated by uranium mine tailings caused by South Africa's nuclear and mining industry. 16 March 2009, a leak of radioactive gases from Pelindaba is reported by NECSA.