Radiometric measurement of lignite coal and its by-products and assessment of the usability of fly ash as raw materials in Turkey

Abstract

Lignite coal (LC) is a key energy source for electricity generation in Turkey. During lignite burning, huge amounts of fly ash (FA), bottom ash and slag are produced as by-products which contain radionuclides in the natural radioactive series of uranium and thorium, and radioactive potassium. These radionuclides may lead to radiological exposure of workers and the public and cause environmental problems. Therefore, finding diverse uses for the by-products in the construction sector and earthwork applications has considerable economic and environmental importance. In this study, the activity concentrations of Ra-226, Th-232 and K-40 in and radon emanating power (EP) and radon mass exhalation rate (EXRM) from LC, slag and FA obtained from the Kangal lignite-burning power plant with a power of 457 MWe were measured using gamma-ray spectroscopy. The major chemical components (SiO2, Al2O3, Fe2O3, CaO and MgO) of fly ash samples were analysed using an energy dispersive X-ray fluorescence spectrometer. The annual effective doses received by workers and members of the public were estimated using different scenarios specified in Radiation protection 122. The average activity concentrations of Ra-226, Th-232 and K-40 in LC, slag and FA samples were 187 +/- 21, 16 +/- 1 and 99 +/- 9 Bq kg(-1), 620 +/- 18, 41 +/- 2 and 330 +/- 13 Bq kg(-1), and 937 +/- 30, 38 +/- 2 and 272 +/- 17 Bq kg(-1), respectively. The average values of EP and EXRM of the lignite, slag and FA samples were 8 %, 7 % and 10 %, and 0.1, 0.3 and 0.7 Bq kg(-1) h(-1), respectively. The highest average of the total annual effective dose is estimated at 153 mu Sv for members of the public and 74 mu Sv for workers, lower than the recommended annual limit of 1000 mu Sv.