Abstract
The concentrations of primordial radionuclides (226Ra, 232Th and 40K) in commonly used building materials (brick, cement and sand), the raw materials of cement and the by-products of coal-fired power plants (fly ash) collected from various manufacturers and suppliers in Bangladesh were determined via gamma-ray spectrometry using an HPGe detector. The results showed that the mean concentrations of 226Ra, 232Th and 40K in all studied samples slightly exceeded the typical world average values of 50 Bq kg−1, 50 Bq kg−1 and 500 Bq kg−1, respectively. The activity concentrations (especially 226Ra) of fly-ash-containing cement in this study were found to be higher than those of fly-ash-free cement. To evaluate the potential radiological risk to individuals associated with these building materials, various radiological hazard indicators were calculated. The radium equivalent activity values for all samples were found to be lower than the recommended limit for building materials of 370 Bq kg-1, with the exception of the fly ash. For most samples, the values of the alpha index and the radiological hazard (external and internal) indices were found to be within the safe limit of 1. The mean indoor absorbed dose rate was observed to be higher than the population-weighted world average of 84 nGy h–1, and the corresponding annual effective dose for most samples fell below the recommended upper dose limit of 1 mSv y–1. For all investigated materials, the values of the gamma index were found to be greater than 0.5 but less than 1, indicating that the gamma dose contribution from the studied building materials exceeds the exemption dose criterion of 0.3 mSv y-1 but complies with the upper dose principle of 1 mSv y−1.
Highlights
Primordial radionuclides are always present in the environment throughout the world in various isotopic forms, and human beings are constantly exposed to natural sources of ionizing radiation
Gamma rays emitted from the uranium and thorium decay series and from 40K are the primary sources of whole-body external radiation exposure in buildings, whereas internal radiation exposure, with potential effects on the respiratory area, typically results from inhaling radon and its progeny, which emit alpha particles that are exhaled from building materials into the indoor atmosphere [4, 8,9,10,11,12]
The variations in activity concentration among the building materials may be attributed to their radioactive mineral content and the geological, geochemical and geographical origins of the raw materials, among other factors [21]
Summary
Primordial radionuclides are always present in the environment throughout the world in various isotopic forms, and human beings are constantly exposed to natural sources of ionizing radiation. The natural decay series radionuclides (238U, 232Th and 235U) represent the most significant sources of ionizing radiation on Earth, contributing approximately 83% to the total effective dose received by the global population [1, 2]. The radioactive isotope 40K contributes approximately 16% of the annual effective dose experienced by individual members of the global populace due to ionizing radiation [1, 2, 3]. These naturally occurring radionuclides and their associated progenies are the radionuclides that are most commonly found in building materials, and exposure dose result predominantly from these radionuclides [4]. The radiological risk to inhabitants may be significant if the materials used for building construction contain elevated levels of radioactivity
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