Naturally Occurring Radioactive Materials in Uranium-Rich Coals and Associated Coal Combustion Residues from China

摘要

Most coals in China have uranium concentrations up to 3 ppm, yet several coal deposits are known to be enriched in uranium. Naturally occurring radioactive materials (NORM) in these U-rich coals and associated coal combustion residues (CCRs) have not been well characterized. Here we measure NORM (Th, U, ~(228)Ra, ~(226)Ra, and ~(210)Pb) in coals from eight U-rich coal deposits in China and the associated CCRs from one of these deposits. We compared NORM in these U-rich coals and associated CCRs to CCRs collected from the Beijing area and natural loess sediments from northeastern China. We found elevated U concentrations (up to 476 ppm) that correspond to low ~(232)Th/~(238)U and ~(228)Ra/~(226)Ra activity ratios («1) in the coal samples. ~(226)Ra and ~(228)Ra activities correlate with ~(238)U and ~(232)Th activities, respectively, and ~(226)Ra activities correlate well with ~(210)Pb activities across all coal samples. We used measured NORM activities and ash yields in coals to model the activities of CCRs from all U-rich coals analyzed in this study. The activities of measured and modeled CCRs derived from U-rich coals exceed the standards for radiation in building materials, particularly for CCRs originating from coals with U > 10 ppm. Since beneficial use oi high-U Chinese CCRs in building materials is not a suitable option, careful consideration needs to be taken to limit potential air and water contamination upon disposal of U- and Ra-rich CCRs.