222Rn in private well water in the vicinity of uranium mines over ten years

Abstract

There are many small uranium mines of the sedimentary type in Kamisaibara, Okayama Prefecture, Japan. As inhabitants in Kamisaibara consume water from privately-dug wells, it is important to investigate distributions of 222Rn in privately-dug well water in the vicinity of the mines. The determination of 222Rn in well water was carried out from April 1980 to October 1990. Though small in area (16 km 2), each well water has its own characteristic activity concentrations of 222Rn. The activity concentrations of 222Rn are almost constant for each specific well over a long period (about 10 years). In general, the correlation coefficients for several sampling points are small. As Akawase and Tennoh are situated in the same rock type, the correlation coefficient is the highest value in this area. The estimated dose equivalent for the human stomach is approximately 0.4–54 μSv/year. The type of distribution of 222Rn in privately-dug well water is log normal.