Inhalation dose from exposure to radon, thoron and their progeny in indoors around a nuclear power generation facility in Uttar Pradesh, India

Radon, thoron and their progeny concentration have been measured in dwellings located within a 90 km2 area around a nuclear power plant using solid-state nuclear track detectors. Time-integrated measurements were carried out on a four-month cycle, making three measurements in each dwelling throughout the year. In total, 145 dwellings were selected for the study. The measured values of gas and their progeny concentrations were used to determine the equilibrium factor for radon and thoron indoors and annual inhalation dose. The average value of the equilibrium factor indoors was found to be 0.44 ± 0.23 for radon and 0.015 ± 0.010 for thoron. The annual inhalation dose for the public living around this plant was found to be 0.97 ± 0.55 mSv. Results were analysed for different seasons and different categories of dwellings for their construction type.

Radon/thoron and progeny levels in dwellings: Regional variations and effect of dwelling characteristics – A case study in Jalandhar district of Punjab, India

An extensive survey to measure natural radioactivity in human environment in Jalandhar district of Punjab was undertaken. Results of measurements of indoor radon/thoron and their progeny concentrations are being presented here. Single-entry, pin-hole dosemeters were used for the measurement of radon/thoron concentrations. Deposition-based direct radon/thoron progeny sensors were used for measurement of progeny concentrations. The results have been analysed on the basis of regional characteristics, type of construction and building material used. The radon concentration was found to vary from 6.64 ± 1.72 Bq/m3 to 47.18 ± 4.43 Bq/m3 with geometric mean value of 17.9 ± 2.91 Bq/m3 while the thoron concentration varies from 7.75 ± 2.54 Bq/m3 to 82.68 ± 8.33 Bq/m3 with geometric mean value of 33.54 ± 5.09 Bq/m3. The geometric mean value of equilibrium factor for indoor radon and thoron was found to be 0.43 and 0.02, respectively. The estimated annual inhalation dose varies from 0.22 mSv to 1.76 mSv with geometric mean value of 0.66 mSv. Correlation of indoor radon and air gamma dose rate was also studied.

Estimation of indoor radon, thoron and their decay products’ concentrations along with annual inhalation dose in dwellings of Punjab, India

In the present study, indoor radon and thoron concentrations were assessed using a newly developed pin hole-based twin cup dosimeter with a single-entry face in some areas of Punjab state, India. The equilibrium equivalent concentrations of radon and thoron were estimated directly by using the newly developed progeny (decay products) sensors designed by Bhabha Atomic Research Centre, Mumbai, India. The average radon and thoron concentrations in the study region were found to be 61.6 ± 18.6 Bq/m3 and 68.0 ± 30.8 Bq/m3, respectively, while the average equilibrium equivalent concentrations of radon and thoron were 25.9 ± 7.7 Bq/m3 and 2.2 ± 0.7 Bq/m3, respectively. Calculated average equilibrium factor for radon and thoron was 0.45 and 0.04, respectively, in the present study. The annual inhalation dose that was calculated from the present observed concentrations varied from 1.1 to 4.1 mSv/year with an average value of 2.4 mSv/year, which is well within the reference level of 10mSv/year recommended by International Commission on Radiological Protection. The study shows that thoron is a significant contributor to the inhalation dose, which is about 29% of the total inhalation dose.