Fukushima Nuclear Accident Update Log

Fukushima Nuclear Accident Update Log
2. Radiation monitoring

• On 12th April, deposition of both iodine-131 and cesium-137 was detected in 7 and 6 prefectures respectively. The values reported for iodine-131 ranged from 1.6 to 460 Bq/m2 and for cesium-137 from 31 to 700 Bq/m2. The highest deposition was observed in the Ibaraki prefecture.
• Gamma dose rates are measured daily in all 47 prefectures, the values tend to decrease. For Fukushima, on 12th April a dose rate of 2.1 μSv/h, for the Ibaraki prefecture a gamma dose rate of 0.14μSv/h was reported. The gamma dose rates in all other prefectures were below 0.1 µSv/h.
• Only in a few prefectures, iodine-131 or cesium-137 is detectable in drinking water at very low levels. As of 12th April, a restriction for infants related to iodine-131 (100 Bq/l) is in place as a precautionary in a small scale water supply in one village of the Fukushima prefecture.
• MEXT reported on measurements of strontium-89 (half-life: 50.5 days) and strontium-90(half-life: 28.8 years) in three samples taken in one village in the Fukushima prefecture on 16 March. The activities in soil for Sr-89 ranged from 13 and 260 Bq/kg and for Sr-90 between 3.3 and 32 Bq/kg. Sr-90 was also distributed globally during nuclear weapons’ testing in the atmosphere, typical global levels of Sr-90 in surface soils are in the order of one to a few becquerel per kg. Strontium was also measured in plant samples in four others villages, with values ranging from 12 to 61 Bq/kg for Sr-89 and 1.8 to 5.9 Bq/kg for Sr-90.
• On 12th April, the IAEA Team made measurements at 7 different locations in the Fukushima area at distances of 32 to 62 km, North and Northwest from the Fukushima nuclear power plant. At these locations, the dose rates ranged from 0.6 to 1.6 µSv/h. At the same locations, results of beta-gamma contamination measurements ranged from 0.6 to 1.7 Megabecquerel/m2.
• […]
• Analytical results related to food contamination were reported by the Japanese Ministry of Health, Labour and Welfare on 12th April that covered a total of 55 samples taken on the 8th and 10th — 12th April. Analytical results for 53 of the samples of various vegetables, fruit (strawberry), seafood and unprocessed raw milk in eight prefectures (Chiba, Fukushima, Gunma, Ibaraki, Kanagawa, Niigata, Saitama and Yamagata) indicated that I-131, Cs-134 and/or Cs-137 were either not detected or were below the regulation values set by the Japanese authorities. In Ibaraki prefecture for samples taken on 11th April, one sample of seafood (sand lance) was above the regulation values set by the Japanese authorities for I-131 and one sample of spinach was above the regulation values set by the Japanese authorities for Cs-134/Cs-137.