ASSESSMENT OF INHALATION DOSE FROM THE INDOOR 222Rn AND 220Rn USING RAD7 AND PINHOLE CUP DOSEMETERS

Radon and thoron exhalation rate in the soil of Western Haryana, India

This study reports the exhalation rates of radon and thoron from surface soil collected from 60 rural sites of district Hisar, Haryana, India. The exhalation rates of Rn²²² (radon) and Rn²²⁰ (thoron) were measured by portable SMART RnDuo (AQTEK SYSTEMS) using a mass accumulation chamber which was equipped with a scintillation material-coated cell. Dose rates due to natural gamma radiations ranged from 0.526 to 1.139 mSv y^-1. The Rn²²² mass exhalation rate in soil samples varied from 0.14 to 94.65 mBq kg^-1 h^-1. Thoron surface exhalation rates ranged from 46.42 to 619.88 Bq m^-2 h^-1. This study gives an idea about the differences in Rn²²² and Rn²²⁰ exhalation at different locations which may be due to variations in geological features of the locations and characteristics of the topsoil. The findings show that usage of study area soil as building material is safe.

Statistical inferences from measured data on concentrations of naturally occurring radon, thoron, and decay products in Kumaun Himalayan belt

Regional averages of radon, thoron, and associated decay product concentration are reported to be higher than their respective global averages in recent studies conducted in Indian Himalayan belt. The present study explores another region in Indian Himalayan belt by conducting measurements of radon, thoron, and decay product's activity concentration in 92 dwellings of Bageshwar district. The year-long measurements were performed in all 3 seasons distinguishing dwellings as per their construction material. The average radon and thoron concentration for the study region was measured as 57 Bq/m³ and 66 Bq/m³, respectively. Analysis of the measured data in terms of seasonal effects and construction material led to well established inferences, i.e., higher concentration for mud houses and for winter season. In addition, the present study focuses on lesser probed statistical inferences. One of them is related to the appropriateness of frequency distribution function for the measured data and other dwells upon the correlation analysis of inter-related factors for high concentration cases. Three distribution functions (Lognormal, Weibull, and Gamma) were found to be following the trend of frequency distribution curve of the measured data. For mud houses in winter season, variations of radon/thoron concentration were attempted to correlate with mass/surface exhalation rate, emanation rate, and source term content. More than 80% of the dwellings of the study region were found to have gas and decay product's concentration levels, higher than the respective global average values. However, these values were mostly within the reference levels for residential environments. Nevertheless, this region requires further studies to pinpoint the causes for elevated levels and suggest simple remedial modifications if required.

Residential radon exposure and seasonal variation in the countryside of southeastern Brazil

Poorly ventilated environments such as residences can accumulate radon gas to levels that are harmful to humans and thus produce a public health risk. To assess the risk from natural radiation due to indoor radon exposure, ²²²Rn measurements, using an alpha RAD7 detector, were conducted in Timóteo, Minas Gerais state, southeastern Brazil. Indoor radon concentrations, along with meteorological parameters, were measured every 2 h during both wet and dry seasons in 2017 and 2018. The mean concentration of indoor radon varied between 18.0 and 412.8 Bq m^-3, which corresponded to an effective annual dose of 1.2 and 7.6 mSv y^-1. Average radon concentrations were significantly higher during the winter dry season, and there was a strong positive correlation with humidity in both wet and dry season. Furthermore, concentrations showed an inverse correlation with atmospheric pressure, wind speed, air temperature, and solar radiation. The radon levels are generally above the limits recommended by international standards, meaning that mitigation measures are needed to improve air quality to reduce human exposure and risk. Finally, through the statistical analysis, it was possible to determine the differences and similarities between the sampling points concerning the geology of the place and the geographical location.

Quantification of an alpha flux based radiological dose from seasonal exposure to 222Rn, 220Rn and their different EEC species

This study summarizes the seasonal experimental data on the activity concentrations of indoor 222Rn (Radon), 220Rn (Thoron) and their progeny in Mansa and Muktsar districts of Punjab (India) using LR-115 solid state nuclear track detector based time integrated pin-hole cup dosimeters and deposition based progeny sensors for the assessment of radiological dose. The indoor 222Rn concentration was observed higher in the rainy and winter seasons while 220Rn concentration was observed higher in the winter season. However, Equilibrium Equivalent Concentrations (EECs) of 222Rn and 220Rn exhibited distinct seasonal behaviour unlike their parent nuclides. The average equilibrium factors for 222Rn (FRn) and 220Rn (FTn) were found 0.47 ± 0.1 and 0.05 ± 0.01, respectively. The annual arithmetic means of unattached fractions of 222Rn ([Formula: see text]) and 220Rn ([Formula: see text]) were found to be 0.09 ± 0.02 and 0.10 ± 0.02, respectively. The attachment rate (XRn) and attachment rate coefficients (β) of 222Rn progeny were also calculated to understand the proper behaviour of progeny species in the region. A new alpha flux based technique has been proposed and used for the assessment of absorbed dose rate and annual effective dose rate for radiation protection purpose.

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

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.