Coal-fired power plants (CFPP) provide approximately 40% of the world’s energy demand. Naturally occurring radioactive materials (NORM) contained in coal become enriched in coal combustion residues as a result of the elimination of carbon during combustion. The fly ash and bottom ash produced from CFPP may be significant sources of exposure to naturally occurring radionuclides for the population near the combustion plant or ash dumps. Despite this fact, very few studies have actually addressed the relationship of the NORM enrichment factors and the quality of coal used. This paper aims to relate the quality of coal to the enrichment factors for the radionuclides of interest (K 40 , Ra 226 , Th 232 and Po 210 ) in coal combustion residues from three South African CFPP. The data from other CFPP was also taken into account to establish this correlation. The feedstock coal used in these CFPP is typically low quality, with ash content in the range of 25 - 45 wt%. The radionuclides investigated were determined by gamma spectrometry with the exception of Po 210 , which was determined by alpha spectrometry. The enrichment factors for the radionuclides of K 40 , Ra 226 , Th 232 and Po 210 in the fly ash and bottom ash (except Po 210 ) was found to be directly proportional to the quality of coal. That is when the ash percentage increased (coal quality decreased) the enrichment factor decreased. The Po 210 radionuclide in the bottom ash had an enrichment factor less than one. The relationship between coal quality and enrichment factors for the radionuclides of K 40 , Ra 226 , Th 232 and Po 210 in both the fly ash and bottom ash (except Po 210 in the bottom ash) was demonstrated by the following mathematical equation: . This equation may be used as a good indication in obtaining an estimate in determining the enrichment of the mentioned radionuclides in coal combustion products such as fly ash and bottom ash.
International Energy Outlook (2011). https://www.eia.gov/outlooks/ieo/
Energy.gov.za. (2019) Energy Sources: Coal. Department: Energy, Republic of South Africa. http://www.energy.gov.za/files/coal_frame.html
Tang, Q., Liu, G., Yan, Z. and Sun, R. (2012) Distribution and Fate of Environmentally Sensitive Elements (Arsenic, Mercury, Stibium and Selenium) in Coal-Fired Power Plants at Huainan, Anhui, China. Fuel, 95, 334-339. https://doi.org/10.1016/j.fuel.2011.12.052
Lauer, N.E., Hower, J.C., Hsu-Kim, H., Taggart, R.K. and Vengosh, A. (2015) Naturally Occurring Radioactive Materials in Coals and Coal Combustion Residuals in the United States. Environmental Science & Technology, 49, 11227-11233. https://doi.org/10.1021/acs.est.5b01978
Flues, M., Camargo, I., Silva, P. and Mazzilli, B. (2006) Radioactivity of Coal and Ashes from Figueira Coal Power Plant in Brazil. Journal of Radioanalytical and Nuclear Chemistry, 270, 597-602. https://doi.org/10.1007/s10967-006-0467-0
Tadmor, J. (1986) Radioactivity from Coal-Fired Power Plants: A Review. Journal of Environmental Radioactivity, 4, 177-204. https://doi.org/10.1016/0265-931X(86)90010-X
Zeevaert, T., Sweeck, L. and Vanmarcke, H. (2006) The Radiological Impact from Airborne Routine Discharges of a Modern Coal-Fired Power Plant. Journal of Environmental Radioactivity, 85, 1-22. https://doi.org/10.1016/j.jenvrad.2005.04.015
Sahu, S.K., Bhangare, R.C., Ajmal, P.Y., Sharma, S., Pandit, G.G. and Puranik, V.D. (2009) Characterization and Quantification of Persistent Organic Pollutants in Fly Ash from Coal Fueled Thermal Power Stations in India. Microchemical Journal, 92, 92-96. https://doi.org/10.1016/j.microc.2009.02.003
Mishra, U.C. (2004) Environmental Impact of Coal Industry and Thermal Power Plants in India. Journal of Environmental Radioactivity, 72, 35-40. https://doi.org/10.1016/S0265-931X(03)00183-8
Sahu, S.K., Tiwari, M., Bhangare, R.C. and Pandit, G.G. (2014) Enrichment and Particle Size Dependence of Polonium and Other Naturally Occurring Radionuclides in Coal Ash. Journal of Environmental Radioactivity, 138, 421-426. https://doi.org/10.1016/j.jenvrad.2014.04.010
Daish, S.R., Dale, A.A., Dale, C.J., May, R. and Rowe, J.E. (2005) The Temporal Variations of 7 Be, 210 Pb and 210 Po in Air in England. Journal of Environmental Radioactivity, 84, 457-467. https://doi.org/10.1016/j.jenvrad.2005.05.003
Ozden, B., Guler, E., Vaasma, T., Horvath, M., Kiisk, M. and Kovacs, T. (2018) Enrichment of Naturally Occurring Radionuclides and Trace Elements in Yatagan and Yenikoy Coal-Fired Thermal Power Plants, Turkey. Journal of Environmental Radioactivity, 188, 100-107. https://doi.org/10.1016/j.jenvrad.2017.09.016
Bhattacharyya, S., Donahoe, R.J. and Patel, D. (2009) Experimental Study of Chemical Treatment of Coal Fly Ash to Reduce the Mobility of Priority Trace Elements. Fuel, 88, 1173-1184. https://doi.org/10.1016/j.fuel.2007.11.006
Amin, Y.M., Uddin Khandaker, M., Shyen, A.K.S., Mahat, R.H., Nor, R.M. and Bradley, D.A. (2013) Radionuclide Emissions from a Coal-Fired Power Plant. Applied Radiation and Isotopes, 80, 109-116. https://doi.org/10.1016/j.apradiso.2013.06.014
Sahoo, S.K., Parami, V.K., Quirit, L.L., Yonehara, H., Ishikawa, T. and Tokonami, S. (2011) Determination of Uranium Concentrations and Its Activity Ratios in Coal and Fly Ash from Philippine Coal-Fired Thermal Power Plants Using ICP-MS and TIMS. Radiochimica Acta, 1, 257-261.
Lauer, N., Vengosh, A. and Dai, S. (2017) Naturally Occurring Radioactive Materials in Uranium-Rich Coals and Associated Coal Combustion Residues from China. Environmental Science & Technology, 51, 13487-13493. https://doi.org/10.1021/acs.est.7b03473
Benedette Cuffari, M. (2019) How Radioactive Coal Is Limiting Its Use. https://www.azomining.com/Article.aspx?ArticleID=1377
Council for Geoscience (2018) Council for Geoscience. http://www.geoscience.org.za/index.php/publication/downloadable-material
ISO (2006) Hard Coke and Coal Manual Sampling. South African Bureau of Standards.
ISO (2001) Hard Coal and Coke-Mechanical Sampling Part 6: Coke-Preparation of Test Samples. South African Bureau of Standards.
ISO (2005) Classification of Coals. South African Bureau of Standards.
Asaduzzaman, K., Khandaker, M.U., Amin, Y.M., Bradley, D.A., Mahat, R.H., Nor, R.M. (2014) Soil-to-Root Vegetable Transfer Factors for 226 Ra, 232 Th, 40 K, and 88 Y in Malaysia. Journal of Environmental Radioactivity, 135, 120-127. https://doi.org/10.1016/j.jenvrad.2014.04.009
Khandaker, M., Wahib, N., Amin, Y. and Bradley, D. (2013) Committed Effective Dose from Naturally Occuring Radionuclides in Shellfish. Radiation Physics and Chemistry, 88, 1-6. https://doi.org/10.1016/j.radphyschem.2013.02.034
Baeza, A., Corbacho, J.A., Guillén, J., Salas, A., Mora, J.C., Robles, B. and Cancio, D. (2012) Enhancement of Natural Radionuclides in the Surroundings of the Four Largest Coal-Fired Power Plants in Spain. Journal of Environmental Monitoring, 14, 1064-1072. https://doi.org/10.1039/c2em10991c
Mora, J.C., Baeza, A., Robles, B., Corbacho, J.A. and Cancio, D. (2009) Behaviour of Natural Radionuclides in Coal Combustion. Radioprotion, 44, 577-580.
Pinheiro, H.J. (1999) A Techno-Economic and Historical Review of the South African Coal Industry in the 19th and 20th Centuries, and Analyses of Coal Product Samples of South African Collieries 1998-1999. Bulletin 113, SABS, 97 p.
IAEA (2003) Extent of Environmental Contamination by Naturally Occurring Radioactive Material (NORM) and Technological Options for Mitigation. International Atomic Energy Agency, Vienna.
UNSCEAR (1993) Sources and Effects of Ionizing Radiation. United Nations Scientific Committee on the Effects of Atomic Radiation, United Nations, New York.
Xinwei, L., Xiaodan, J. and Fengling, W. (2006) Natural Radioactivity of Coal and Its Byproducts in the Baoji Coal-Fired Power Plant, China. Current Science, 91, 1508-1511.
Papastefanou, C., Manolopoulou, M. and Charalambous, S. (1984) Exposure from the Radioactivity in Building Materials. Health Physics, 47, 775-783.
Bem, H., Wieczorkowski, P. and Budzanowski, M. (2002) Evaluation of Technologically Enhanced Natural Radiation Near the Coal-Fired Power Plants in the Lodz Region of Poland. Journal of Environmental Radioactivity, 61, 191-201. https://doi.org/10.1016/S0265-931X(01)00126-6
Gu, H., Zheng, R., Zhang, W., Wu, Z. and Kong, L. (1996) Natural Radioactive Level in Coal and Ash and Building Material Products from Coal-Fired Power Plants in Beijing. Radiation Protection, 16, 309-316.