2012 年 47 巻 3 号 p. 198-203
We developed a Ge semiconductor detector system that allows real-time mapping of radionuclides using a vehicle. We used this system to conduct a background survey in the Chugoku Region of Japan. 214Bi (U-series) concentration was high in the east and west of Hiroshima Prefecture; 208Tl (Th-series) concentration was high in Oki-island in Shimane Prefecture and in the western part of Hiroshima Prefecture, and 40K was high in the entire area of Hiroshima Prefecture, while the concentrations of all types of radionuclides were low in the plains in the eastern part of Shimane Prefecture. The artificial radionuclide 137Cs was detected in Tottori, Shimane and Yamaguchi Prefectures as well as in the Chugoku Mountains. The results of the survey did not indicate that Shimane Prefecture had been affected by the accident at the Fukushima Daiichi Nuclear Power Plant.