A survey of environmental radiation Aichi, Gifu and Mie Prefectures

The natural radiation dose rates in Aichi, Gifu and Mie Prefectures were es timated with a car-borne survey system using NaI(T1) scintillation spectrom eters and a handy-type barometer from which cosmic radiation was estimated. The following factors were taken into consideration the shielding effect o f the car body, the effect of the road pavement, radon progeny borne by pre cipitation, and increases in tunnels and near the walls. Absorbed dose rate s of air due to terrestrial gamma rays were estimated to be 39.1+/-6.7, 53. 0+/-6.1 and 44.5+/-7.7 nGy/h in Aichi, Gifu and Mie Prefectures, respective ly. The absorbed dose rates of air due to the sum of terrestrial gamma rays and cosmic radiation were 68.1+/-6.8, 83.5+/-7.6 and 73.6+/-47.7nGy/h in t he same prefectures, respectively. Also, radiation maps of the terrestrial gamma rays as well as maps of the sum of both terrestrial gamma rays and co smic radiation were drawn.