Quantification of U, Th and specific radionuclides in coal from selected coal fired power plants in South Africa

Most of South Africa's energy is derived from the combustion of coal in pulverized coal-fired power plants (CFPP). However, when compared with the rest of the world, limited information regarding the main radioactive elements (U and Th) and specific radionuclides of interest (K-40, Ra-226 and Th-232) from South African CFPP is available in the public domain. This paper aims to quantify the U, Th and specific radionuclides found in the coal used in selected South African CFPP in comparison to world averages found in literature. The U and Th concentrations were obtained by ICP-MS. The main radionuclides, K-40, Ra-226 and Th-238, were quantified using gamma spectrometry. The U concentration and Th concentrations for the coal used in all the power plants was above the world average of 1.9 mg/kg and 3.2 mg/kg respectively. The coals with the highest Th content originated from the Mpumalanga power plant, while the U content in the Freestate power plant samples was the highest of the three. The concentrations of the K-40 were between 88.43 +/- 10.75-110.76 +/- 8.92 Bq/kg, which are inline with world averages of 4-785 Bq/kg. Similarly, the Ra-226 and Th-232 values were between 21.69 +/- 2.83-52.63 +/- 4.04 Bq/kg and 19.91 +/- 1.24-22.97 +/- 1.75 Bq/kg respectively, which are also in line with the world averages of 1-206 Bq/kg and 1-170 Bq/kg respectively. Radiological hazard indices such as radium equivalent (Ra-eq); external hazard index (H-ex) and internal hazard index (H-in), that were estimated from these average radionuclide concentrations were less than the prescribed values found in literature. This indicated that no significant health risk was posed by the coal being used from these coal fields.