900,000 Terabecquerels Were Released at Fukushimas Daiichi
On May 24th, Tokyo Electric Power Company (TEPCO) announced that the estimated amount of radioactive material released into the atmosphere after the Fukushima Dai-ichi Nuclear Power Plant accident was 900,000 terabecquerels. TEPCO reported for the first time that around 80% of the radioactive material was released from reactors 2 and 3 and one-third of the material spread over the Iitate area (northwest direction) from March 15 to 16.
They back calculated the measurements of radioactive material in the atmosphere, soil and seawater immediately following the accident (3/12/11-2/31/11). They measured against the time the containment buildings pressure changed and exploded and exhaust gas was released to estimate which reactor, when and how much material was released.
According to the analysis, on the 15th the pressure suddenly dropped in the suppression chamber of reactor 2 and 160,000 terabecquerels were released. Reactor 3, which caused a hydrogen explosion on March 14th, released 180,000 terebecquerels two days later on March 16th.
At the time of the explosion 5000 terabecquerels were released and only 1400 was released from the venting, while more than half was released from the damaged areas of the containment chamber. A total of 17% (approximately 5.2 million terebecquerels) of the 1986 Chernobyl accident was released into the atmosphere.
Various reports of total release were announced, starting in June of 2011 with 770,000 reported by Nuclear and Industrial Safety, in February of 2012 480,000 was announced and last August the Nuclear Safety Commission of Japan estimated 570,000.