Geochemical characterization of tailings at the McArthur River Mine, Saskatchewan

This paper presents the results of geochemical testing of tailings from two of the world’s largest uranium deposits, Key Lake (average grade 2.5% U 3 O 8 ), and McArthur River (average grade 15% U 3 O 8 ), both located in northern Saskatchewan. As major co-owner and operator of these deposits, Cameco Corporation, plans to dispose of tailings from the McArthur River deposit in the Deilmann tailings management facility (TMF) at the Key Lake Mine. Steffen Robertson and Kirsten (Canada) Inc. conducted a geochemical testing program of tailings obtained from bench scale tests on McArthur River ore, and modeled the long term pore water quality. Results are compared to results of a similar testing program completed for Key Lake ore in order to estimate the effect of adding McArthur River tailings to the TMF. Because of its high radioactivity, the high grade McArthur River ore cannot be processed in the Key Lake mill without major adjustments in the mill and tailings systems. Therefore, McArthur River ore will be blended with Key Lake Special Waste (~0.09% U 3 O 8 ) prior to milling, resulting in a more conventional average grade of 4% U 3 O 8 . Several blended samples with various proportions of McArthur River ore and Key Lake Special Waste, including an optimized blend, were produced and tested. In addition, to determine the chemistry that can be expected from processing of very high grade ore with U 3 O 8 content of greater than 30%, a tailings sample of this material was also produced and tested. Results indicate that, unlike Key Lake tailings, McArthur River tailings are potentially acid generating, but that uranium, molybdenum, arsenic, and nickel concentrations in tailings pore water are lower than in pore waters from Key Lake tailings. Predicted long term concentrations of uranium and arsenic are also lower. Predicted long-term radium-226 concentrations are the same.