Measurements of Radon and its Short-lived Decay Products and Unattached Fraction in Air

Measurements of radon and its short-lived daughters in air in tunnels were carried out. The mean value of the unattached fraction of potential a energy fp for 218Po (RaA) was 0.12 with a minimum of 0.09 and a maximum of 0.14 and the unattached fraction f was 0.49 ± 0.14. Measurements indicated a good correlation between RaA concentration and equilibrium equivalent RaA concentration obtained assuming equilibrium between daughter products. This correlation was also supported by the other measurements in room air. From this fact, a good correlation between the unattached fraction and an equilibrium equivalent unattached fraction f* derived from equilibrium equivalent RaA concentration can be expected. This suggests that the equilibrium equivalent unattached fraction obtained using a single filter pack method may be helpful in assessments of a dose to the respiratory tract due to the inhalation of radon daughters. From the equilibrium equivalent unattached fraction measured in various atmospheres, agreement between observed and calculated equilibrium equivalent unattached fractions was confirmed.