Timeline of the Fukushima Daiichi nuclear disaster of caesium-137 by the Atmospheric Chemistry and Physics journal—an estimate about 42 percent of that released into the atmosphere in the Chernobyl explosion in 1986. Caesium-137 has a half-life of 30 years. TEPCO reports the completion of a cover for the reactor unit 1, which is 54 metres high, 47 metres wide and 42 metres deep. The cover has a built-in ventilation system that is supposed to filter radioactive material. Boric acid is injected into reactor number 2 after the discovery of xenon in its containment vessel. The presence of xenon may be an indication that a self-sustained fission reaction
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.