Levels of radioactive cesium 137 in waters off Fukushima Prefecture are 58 times higher than before the March 11 quake that crippled a nuclear power plant there, a government survey shows.
The science ministry conducted sophisticated sensitive analysis of seawater sampled in 11 locations, mostly about 45-320 kilometers off the coasts of Fukushima, Miyagi, Ibaraki and Chiba prefectures, in late August.
Cesium 137 levels about 140 kilometers east of the stricken Fukushima No. 1 nuclear power plant came to 0.11 becquerel per liter, or 58 times more than in 2009, the ministry said Oct. 5.
Still, the figures for all locations were less than 1 percent of the legal standard of 90 becquerels for ocean waters.
It was the first sensitive analysis covering large areas.
In a 2009 ministry survey off the four prefectures, maximum readings were between 0.0015 and 0.0023 becquerel per liter.
The latest survey detected 0.10 becquerel about 215 kilometers southeast of the Fukushima No. 1 plant, 50 times more than in 2009, and 0.076 becquerel about 200 kilometers northeast of the plant, 33 times more.
Seawater sampled off Chiba Prefecture contained 0.0012-0.0023 becquerel, roughly unchanged from 2009.
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