Japan's Nuclear Safety Commission blames problems with the Fukushima Daiichi reactor suppression pool for large radiation releases.
It said that much of the radiation was released on 15 and 16 March, after the pool began to run into trouble, , according to a report from Japanese newswire NHK republished by the Japan Atomic Industrial Forum. Although radiation continues to be released, the volume of release has dropped by a large extent since then. The incident at units 1, 2 and 3 was reclassified as a INES level 7 major accident partly because of the large amount of radiation released.
In other news, TEPCO has finally began pumping contaminated water that has pooled in low-lying areas. On 12 April it began pumping water out of the unit 2 trench into the unit 2 turbine condenser, it reported.
In other news, NHK reports that Fukushima prefecture has begun a comprehensive programme to measure radiation levels at 2725 locations across the region beyond the 20km exclusion zone. The study began on Tuesday 12 April and will continue until Friday 15 April. The survey will also include studies of iodine and caesium in the soil.
Hiroshima University professor Kiyoshi Shizuma said that most of the radiation observed in Fukushima is radioactive caesium that has fallen to the ground. He advised residents to wear masks to reduce the risk of inhaling radioactive dust, NHK also reported.
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