Survey of the natural radionuclides concentrations using a car-borne survey method

In 1992 similar to 1996, we estimated the environmental radiation dose rate s and the natural radionuclides concentrations in soil Tokai area in centra l Japan using a car-borne survey method. In this paper, the distribution and the variation of natural radionuclides (potassium, uranium and thorium) concentrations were described, because the natural radiation dose rates were reported in the former paper. In this survey, all concentrations of potassium, uranium and thorium were h ighest in Gifu Prefecture, followed by Mie Prefecture and Aichi Prefecture, and the variation of radionuclide concentration due to region was observed . And, from the correlation analysis between concentration of natural radio nuclides and absorbed dose rates in air due to gamma -ray, it was shown tha t potassium and thorium have greatly contributed to dose rates in air, and among concentrations of potassium, uranium and thorium, strong correlation was shown between potassium and thorium. Lastly, we showed results of correlation analysis between terrestrial gamma -ray dose rates obtained from this survey and annual mean radon concentrat ion obtained by other researchers.