Naturally Occurring Radionuclides of AshProduced by Coal Combustion.The Case of the Kardia Mine in Northern Greece

摘要

West Macedonia Lignite Center (WMLC), located in Northwest Greece, releases intothe atmosphere about 21,400 tons/year of fly ash through the stacks of four coal fired plants. Thelignite ash contains naturally occurring radionuclides, which are deposited on the WMLC basin.This work investigates the natural radioactivity of twenty six ash samples, laboratory producedfrom combustion of lignite, which was sampled perpendicularly to the benches of the Kardia mine.The concentrations of radionuclides ~(40)K, ~(235)U, ~(238)U,~(226)Ra,~(228)Raand ~(232)Th,were measuredspectroscopically and found round one order of magnitude as high as those of lignite.Subsequently the Radionuclide Partitioning Coefficients of radionuclides were calculated and itwas found that they are higher for ~(232)Th,~(228)Raand ~(40)K, because the latter have closer affinity with the inorganic matrix of lignite. During combustion up to one third of the naturally occurringradioisotopes escape from the solid phase into the flue gases. With comparison to relative globaldata, the investigated ash has been found to have relatively high radioactivity, but the emissions ofthe WMLC radionuclides contribute only 0.03% to the mean annual absorbed dose.