Japan’s Ministry of Education, Culture, Sports, Science and Technology (MEXT) has released results of the measurements of radionuclide concentrations in the soil within the 20 km evacuation zone, according to a report from the Japanese Atomic Industrial Forum.

Soil was sampled from the surface to 5 cm deep on April 2. In the Yamada district of Futaba Town, about 4km WNW of the Fukushima Daiichi Nuclear Power Station (NPS), the readings were 990 00 0 Bq/kg of I-131, 370 000 Bq/kg of Cs-134, and 380 000Bq/kg of Cs-137. In the Fusawa district of Okuma Town, about 2 km WSW of the plant, the readings were 1 000 000 Bq/kg of I-131; 120 000 Bq/kg of Cs-134, and 120 000Bq/kg of Cs-137, JAIF said.

MEXT says that it will soon be able to publish a soil map with additional measuring points.

It has also published a map showing the projected accumulated radiation dose rate in the air up to March 11, 2012. To estimate the expected radiation dose rate in the air for a one-year period, MEXT used the method adopted by the Nuclear Safety Commission (NSC) of Japan: namely, the exposure dose rate measured outdoors, multiplied by 0.6. That figure assumes that indoor exposure (in a wooden house) is 40% less than outdoor exposure, and that 16 hours is spent indoors each day and eight hours outdoors. The current dose rates were assumed to continue for a year. The distribution of radioactivity, wind direction and weather conditions on March 17 greatly affected the map, JAIF said.

Although it has not been stated officially, critics of the government are claiming that the map shows persistent high levels of projected dose and that areas as yet unevacuated exhibit cumulative radiation doses over the course of the next year far exceeding annual legal radiation exposure limits. Unconfirmed government statements suggest civilians in these areas will receive doses up to 23 times higher than annual legal limits over that period of time.

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