A Survey of a High Natural Radiation Spot in Tono Area, Japan

Abstract

We observed absorbed dose rate in air at a uranium ore outcrop which is known as one of the high natural radiation spot of the Tono area in central Japan. This outcrop was mainly Toki granite and weathered soil. The absorbed dose rate in air measured on the rock and surface soil using a pocket survey meter ranged from 572 to 9684 nGy h^-1, and significantly high values were observed at a small rock body and the bottom of a trench. The uranium concentration of the soil in the trench was 1220 ppm which is a significantly high value. The measured absorbed dose rates in air were reasonably high compared with the general environment.