In order to confirm the radiation safety for an active volcanic island, Miyake-jima, environmental radiation and radioactivity have been investigated. The average, minimum and maximum of the environmental gamma-ray dose rates were estimated to be 18.6nGy·h
-1, 6.7nGy·h
-1 and 29.2nGy·h
-1, respectively. For the radioactivity in soils, the averages of
238U,
232Th and potassium concentrations were found from calculations to be 0.38μg·g
-1, 0.43μg·g
-1 and 0.38%, respectively. The radon exhalation rate was below the detection limit, and the average value of thoron exhalation rate was estimated to be 38mBq·m
-2·s
-1. These results are clear evidence that the radiation level and radioactivity on Miyake-jima are lower than the averages in other parts of Japan. It was confirmed that Miyake-jima is presently a safe island in terms of environmental radiation and radioactivity level.
抄録全体を表示