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
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