Suppression of radon exhalation from soil by covering with clay-mixed soil

Ota, Masakazu*; Iida, Takao*; Yamazawa, Hiromi*; Nagara, Shuichi; Ishimori, Yuu  ; Sato, Kazuhiko ; Tokizawa, Takayuki

A study on the effectiveness of clay-mixed soil as a barrier against radon exhalation from soil surface was carried out at a closed uranium mine in Japan. Continuous observations of radon flux at a clay-covered soil surface and a bare soil surface, radon concentration in soil air and soil moisture content were carried out for 80 days. The mean of radon flux of the clay-covered plot was one fifth of that of the bare plot. This result indicates that clay-mixed soil worked effectively for reduction of radon exhalation from the soil surface. A numerical analysis with a one-dimensional radon transport model for unsaturated soil was carried out to evaluate the effectiveness of the barrier under dry weather conditions. Calculation results suggested that the barrier works effectively even under the dry condition.