Generation and control of radon from soil

摘要

In this study, we developed a simple radon generator which can control the radon generated from soilby changing humidity. The weathering granite soil of central Ibaraki prefecture was used as a radon source in thisexperiment, and the soil particle size was adjusted under 106 μm, using the standard sieve. The humidity of the airwas controlled by changing the volume ratio between the dry and humidified air. The air was then introduced intoa column packed with the soil sample. Radon emanated from the soil sample was measured using a device ofelectrostatic collection type (RAD7, Durridge Co. Inc., USA). Radon concentration increased with absolutehumidity. This might be because the water adsorbed to the soil particles works as a promoter of radon exhalationup to a certain moisture level. Thoron concentration also has the same tendency as radon and its dependency onabsolute humidity was larger than radon. The generation of radon from the soil column was controllable byabsolute humidity of supplied air.