Summary of survey

Results of the Measurement of Depth Distribution of Radioactive Substances in Soil at 39 Locations in Fukushima Prefecture and Neighboring Prefectures ( December 2011, April 2012 )
  1. Analysis results show the 1/10 attenuation depths (mm). The depth distributions of cesium were found to be of exponential shapes. The 1/10 attenuation depth is defined as the distance in which radioactivity decreases by a factor of 10.
  2. Prior to the preparation of the data, in order to confirm the condition in the depth distribution of radioactive cesium comprehensively mainly within a 80 km radius of the Fukushima Dai-ichi NPP, we collected soil samples at various depths using an iron pipe (51 sampling points) and researched the depth distribution of radioactive cesium.
  3. Soil sampling were conducted from April 3, 2012 to April 5, 2012, within the 20 km area from the Fukushima Dai-ichi NPP (27 locations), from December 12, 2011 to December 22, 2011 within the 20 km - 80 km area from the Fukushima Dai-ichi NPP (21 locations) and from December 12, 2011 to December 22, 2011 outside an 80 km radius from the Fukushima Dai-ichi NPP (3 locations).
  4. Soil samples were obtained by driving an iron pipe (circular pipe, length 300 mm, outer diameter 60 mm and bore diameter 56 mm) into the ground by a hammer.
  5. The measurements were conducted using germanium semiconductor detectors
  6. Blank in the column "Air Dose Rate": Air dose rate was not measured at the soil sampling point.
Results of the Measurement of Depth Distribution of Radioactive Substances in Soil at 77 Locations in Fukushima Prefecture and Neighboring Prefectures ( From June 2011 to July 2011 )
  1. Analysis results show the 1/10 attenuation depths (mm). The depth distributions of cesium were found to be of exponential shapes. The 1/10 attenuation depth is defined as the distance in which radioactivity decreases by a factor of 10.
  2. Prior to the preparation of the data, in order to confirm the condition in the depth distribution of radioactive cesium comprehensively mainly within a 80 km radius of the Fukushima Dai-ichi NPP, we collected soil samples at various depths using an iron pipe and researched the depth distribution of radioactive cesium.
  3. Soil sampling was conducted from June 4, 2011 to July 4, 2011 outside an 20 km range from the Fukushima Dai-ichi NPP. It was difficult to measure radioactive cesium in the soil sample from the areas where radioactivity concentrations of radioactive ceisum were small and thus so far depth distributions were confirmed at 77 sampling points.
  4. Soil samples were obtained by driving an iron pipe (circular pipe, length 300 mm, outer diameter 60 mm and bore diameter 56 mm) into the ground by a hammer.
  5. The measurements were conducted using germanium semiconductor detectors
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