A study on indoor radiation dose, radon, thoron and progenies concentrations in a hilly area

The background indoor gamma radiation in the residential places was estimated using CaSO₄:Dy-based thermoluminescent dosimeters. The indoor gamma dose varied from 71 to 327 nGy h⁻¹ with a mean value of 162 ± 31 nGy h⁻¹. The highest gamma dose was observed in summer and the lowest in winter. The indoor gamma radiation was also found to vary with the type of house and building materials used. Indoor radon, thoron and progeny levels were measured for different types of dwellings during four seasons of a year using LR 115 type II film-based solid state nuclear track detectors loaded in twin chamber plastic cups. The average highest radon, thoron and progeny were observed during winter, and the corresponding lowest values were observed during summer. The concentrations of radon, thoron and progenies were found to vary with the type of houses and building materials used. The highest values were observed in mud houses, and the lowest values were recorded in wooden houses. This observed variation may be attributed to changes in ventilation conditions and exhalation rate of ²²²Rn and ²²⁰Rn from the floor and walls of the houses. The effective dose received by the general public due to indoor gamma radiation was found to be 0.79 mSv y⁻¹ and the corresponding values due to radon, thoron were 1.02, and 0.54 mSv y⁻¹, respectively. The inhalation dose received by the general public of the study area was found to be lesser than the action limit of International Commission on Radiological Protection (ICRP), 2009.