Distribution of natural radioactivity in coal and combustion residues of thermal power plants

In India about 70 % of the total power generation originates from thermal power plants. Increasing demands of power in a developing country like India has resulted in rapid increase in thermal generation capacity. Coal fired power generation results in huge amounts of fly ash and bottom ash of varying properties. Coal which contains the naturally occurring radionuclides, on burning results in enrichment of these radionuclides in the ashes. Despite the implementation of best possible mechanisms to restrict release of fly ash from the stack, huge amounts of the same gets released in the environment. Fly ash samples from and around six coal-fired power station across India were measured for U-238, Ra-226, Th-232 and K-40 activity by an HPGe gamma-ray spectrometer. Radium equivalent activity and external hazard index were calculated to assess the radiation hazards arising due to fly ash.