Natural radionuclides from coal fired thermal power plants - estimation of atmospheric release and inhalation risk

Coal, bottom ash and fly ash samples were collected from three different coal-fired thermal power plants in India and subjected to gamma spectrometry analysis for natural radioactivity contents. The results of present study show that fly ash and bottom ash contains two to five times more natural radionuclides than feed coal. None of the fly-ash and bottom ash samples had radium equivalent activities and external hazard index values more than 370 Bq kg(-1) and unity respectively. However the absorbed dose rate at 1 m above the ash pond was 79.19n Gy h(-1) (average of 3 plants) higher than the global average value of 55 nGy h(-1). The corresponding annual external effective dose is estimated to be 0.68 mSv y(-1), which is also more than that (0.46 mSv y(-1)) in areas of natural background radiation. The 5th percentile, 95th percentile and mean values for total inhalation risk arising from radionuclides (Ra-226, Th-228, pb(210) and Nat-U) were found to be 3.83 x 10(-9), 6.50 x 10(-8) and 2.08 x 10(-8) respectively.