Measurement and analysis of radiation distribution images in Hamadori, Fukushima Prefecture

Kawahara, Rika*; Ochi, Kotaro   ; Yamaguchi, Katsuhiko*; Torii, Tatsuo*  

After the accident at the Fukushima Daiichi Nuclear Power Plant in March 2011, there are still areas in Fukushima Prefecture where residents cannot return due to radiation. In this study, we evaluated where radioactive materials would accumulate by visualizing the radiation distribution. Measurements were taken with a Compton camera (H400, H3D) in the area where residents cannot return. Gamma plotters (Gamma Plotter F, Japan Radiation Engineering) were used to measure the air dose rates at 0.05 and 1m above the ground in the entire area. It was found that the air dose rates were high around houses, near roads, and near puddles in depressions. The Compton camera measurements also confirmed the existence of hot spots along the side of the road. This is thought to be due to the accumulation of radionuclides that ran off from gravel and flat concrete where rainwater flows easily, in areas where rainwater tends to accumulate, such as rubble and ditches.