Modeling of indoor 222Rn distribution in ventilated room and resulting radiation doses measured in the respiratory tract

Most of radiation hazard of indoor radon is largely due to the radon progenies, which are inhaled and deposited in the human respiratory tract. It is therefore important to understanding the distribution of radon and their progeny in indoor environment helps in calculating the inhalation doses due to them. This paper focuses on effects of exhalation from different sources (wall, floor and ceiling) and the ventilation profile on distribution of the concentrations of radon and their progeny indoor. The radon exhalation rate from walls, floor and ceiling, and ventilation rate were measured as a part of this study and are used as input in Finite Volume Method (FVM) simulation. The findings show that the radon concentration which is distributed in a non-homogeneous way in the room is due to the difference in the radon concentration of different sources (wall, floor and ceiling). Moreover, the radon concentration is much larger near walls, and decreases in the middle of the room because of the effect of air velocity. It has also been found that the distributions of unattached and attached fraction of 218Po, 214Pb and 214Po radionuclides are similar to that of 222Rn. In addition, equilibrium fraction F and the unattached fraction ( fj) of 218Po, 214Pb and 214Po radionuclides for different values of the attachment rate were evaluated. The committed equivalent doses due to 218Po and 214Po radon short-lived progeny were evaluated in different tissues of the respiratory tract of workers from the inhalation of indoor air.