2020 年 19 巻 p. 1-9
The airborne dispersion of 223Ra and its descendent nuclides from an aqueous 223Ra2+ solution containing sodium chloride/citrate was investigated. The dispersion of 223Ra was not detected, and γ-rays of 211Pb and 211Bi caused by the 219Rn dispersion were observed by means of γ-ray spectrometry. The detected radioactivity of 211Pb was found to decrease as the inner diameter of the vessel containing the 223Ra solution was decreased because of the decreasing surface area of the solution exposed to the air. The dispersal rate of 219Rn from the aqueous solution was determined by the ratio of the number of the dispersed 219Rn atoms calculated from the detected radioactivity of 211Pb on the samples. The values at room temperature were in the range of (1.6 ± 0.1) × 10−3–(2.0 ± 0.1) × 10−2. These rates were found to decrease with decreasing exposed surface area of the vessel used.
