An Accurate derivation of the air dose-rate and the deposition concentration distribution by aerial monitoring in a low level contaminated area

Nishizawa, Yukiyasu; Sugita, Takeshi*; Sanada, Yukihisa   ; Torii, Tatsuo  

For a precise assessment of the distribution of radioactive cesium dispersed over a wide area, one must accurately evaluate the background radiation due to natural radionuclides. We have developed a new method that accurately evaluates the spatial distribution of the background radiation in areas contaminated by radioactive cesium. Using the data from aerial monitoring, we analyzed such distribution while excluding the effect of radioactive cesium. This method made it possible to evaluate not only the precipitation of radioactive cesium with quite well accuracy, but also the spatial distribution of the natural radionuclides all over Japan.