Thursday, September 1, 2011

Extreme soil contamination detected near Fukushima plant

The first comprehensive radiometric survey of accident-derived radiocesium contamination was released August 29, 2011.

The measurements were taken June 6 to June 14, about three months after the Great East Japan Earthquake, by 780 members of 129 universities and specialized organizations from around the nation. Soil samples were collected from about 2,200 locations to identify the concentration levels of radioactive cesium… The map shows that areas with high radiation levels are concentrated in a zone to the northwest of the plant within a 40-km radius of the facility… The finding emerged in a map published Aug. 29 that for the first time shows contamination levels of areas within a 100-km radius of the plant. One location in the town of Okuma had the highest value at about 30 million becquerels of cesium of all types per square meter. About 8 percent of the measured areas recorded more than 555,000 becquerels, the figure that required forcible relocation by residents in the 1986 Chernobyl nuclear incident… Soil samples were collected for each 2-square-km area within an 80-km radius of the plant. Samples were also collected from each 10-square-km area within an 80- to 100-km radius of the facility. The number of sample locations total five for each radius zone. The sample was drawn from the soil 5 centimeters from the surface. The concentration levels of cesium-134 and cesium-137-the half-life periods of which are two years and 30 years, respectively-were estimated as of June 14 in this project.”

The contaminated soil map legend uses the following reporting units. Concentration level of cesium-137 per square meter unit becquerel: 3 million and over; 1 million – under 3 million; 0.6 million – under 1 million; 60,000 – under 0.6 million; and 10,000 – under 60,000. (

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