Report on radioactive contamination due to the Fukushima Daiichi Nuclear Power Plant accident, 2022. Air dose rates in the areas of continuous survey (Motomiya City, Mt. Yomogita-dake, Mt. Takashiba-yama)

An accident occurred at the Fukushima Daiichi Nuclear Power Plant following the Tohoku Pacific Coast Earthquake on March 11, 2011. As a result of this accident, eastern Japan was heavily contaminated with radioactive materials. The author has continuously conducted radioactive contamination surveys since 2011. In this paper, the author reports the results of surveys conducted in 2022, at Motomiya City, Mt. Yomogita-dake, and Mt. Takashiba-yama, in Fukushima Prefecture. In a series of surveys, air dose rates. were measured at 1 m above ground level using a Hitachi ALOKA TCS-171 scintillation survey meter. The survey in Motomiya City was conducted in the central part of the city for a total of 22 days from December 2022 to February 2023. The number of measurement points was 2,717, with air dose rates raging from 0.07 to 1.06 μSv/h, and an average value of 0.19 μSv/h. Measurement results was classified as follows: 1,788 points (65.8 %) where the air dose rates were less than 0.20 μSv:/h, and 25 points (0.86 %) where the air dose rates were 0.50 μSv/h or higher. The survey in Mt. Yomogita-dake was conducted in a mountain trail on July 8, 2022. The number of measurement points was 129, and the range of air dose rates was 0.08 - 1.22 μSv/h, with an average value of 0.26 μSv/h. The survey of Mt. Takashiba-yama was conducted in mountain trails and forest roads on May 12, 2022. The number of measurement points was 205, and the range of air dose rates was 0.06 - 0.41 μSv/h, with an average value of 0.15 μSv/h. (author)