Assessment of progeny concentrations of 222 Rn/ 220 Rn and their related doses using deposition-based direct progeny sensors

Abstract

Indoor radon and thoron concentrations in the domestic environment result in natural radiation exposure to the public due to the inhalation of their short-lived decay products. Keeping this in view, the annual effective dose and other radiation risks due to radon/thoron progenies have been calculated. In this study, newly developed time deposition-based progeny sensors (DTPS/DRPS) were used for long-term passive determination of progeny concentrations in the environment of Jammu and Kashmir, Himalayas, India. The total equilibrium equivalent radon (EECR_A + U) and thoron (EECT_A + U) concentrations ("A" and "U" referring to attached and unattached fractions) were found to vary from 5 to 38 Bq m⁻³ with an average value of 18 Bq m⁻³ and from 0.48 to 5.49 Bq m⁻³ with an average value of 1.69 Bq m⁻³, respectively. The aerosol concentration, equilibrium factors, and unattached fractions for radon and thoron progeny have been estimated in normal living conditions and their dependence on each others have also been studied. The annual equilibrium factor for radon and thoron progeny has been determined from the calculated data. The estimated annual effective dose due to radon progeny (0.34 to 2.42 mSv y⁻¹) and thoron progeny (0.13 to 1.54 mSv y⁻¹) is found to be below the world's recommended level. Based on measurements of mean values of the unattached fraction, dose conversion factors (DCFs) in units of mSv per working level month (WLM) has been calculated and the average calculated values of DCFs are 24, 10, and 13 mSv WLM⁻¹. The variability of equilibrium factor and radon/thoron progeny with different seasons, ventilation conditions, and types of houses were also analyzed.