The Coal Combustion and Gasification Products journal has published the following paper:

Distribution of Uranium and Other Radionuclides in Coal and Coal Combustion Products, with Discussion of Occurrences of Combustion Products in Kentucky Power Plants written by authors: James C. Hower, Shigeng Dai, Greta Eskenazy.

Abstract: Uranium and thorium are part of the mineral assemblages within coals. Uranium can also occur in organic associations, particularly in low-rank coals. While the average U concentration in coals is 2.9 ppm for low-rank coals and 1.9 ppm for bituminous and higher rank coals, high concentrations are known from certain low-rank and thin coals and from coals in areas associated with U mineralization. No high-U coals are mined for power production in the United States. Uranium and Th in coal combustion products are found in amounts more or less in proportion to their concentrations in the feed coal. Not being volatile elements, both U and Th are concentrated in the

Full text of article is at the CCGP Journal