Natural radioactivity assessment of coal combustion residues produced in Indian thermal power plants using high-purity germanium detector

Huge amount of coal combustion residue (CCR) is being generated in India every year. Since coal contains some natural radionuclides, the CCR may contribute to the enhanced natural radiation background. Hence, it is important to monitor the natural radioactivity levels in Indian CCR samples. The present study aims to estimate the natural radioactivity levels in CCRs produced in Indian thermal power plants. Accordingly, six CCR samples from different thermal power plants were collected and packed to achieve secular equilibrium among daughter products of 226 Ra. The samples were counted for activity of gamma radionuclides using high purity germanium detector based high resolution gamma spectrometer. Results show that 40 K is the most abundant among analyzed radionuclides, and the lowest was observed for 226 Ra. Secular equilibrium was observed between 228 Ra and 228 Th, whereas no equilibrium was observed between 226 Ra and 238 U. The activity concentration for 226 Ra and its daughter products ( 214 Pb and 214 Bi) was found to be similar in CCR sample before and after equilibrium, indicating that progenies are in secular equilibrium in CCR. The X ray diffraction analysis of CCR indicates the presence of aluminosilicate as major fraction, which has potential of trapping of 226 Ra and daughter products. The values observed are very low and similar to those observed in naturally occurring radioactive materials such as coal, soil, and sediment, hence are not of radiological concern with respect to human/environment.