Grant: Alliance Grants

The natural resource sector is an important area of Canada's economy. Of the many natural resources that are mined, uranium mining is centred in northern Saskatchewan. The uranium ore bodies contain many mineral phases beside uranium oxide that need to be disposed of in a responsible fashion. Solid mining waste can be placed in a tailings management facility (TMF), which is designed to contain the waste elements and limit interaction with the external environment. To understand how a tailings facility will behave throughout the lifetime of the mining operations that feed the TMF, and after the site has been decommissioned, it is important to understand the chemistry of the tailings and how they change with time. In 2015, the McClean Lake mill began extracting uranium oxide from ore received from the Cigar Lake mine. Owing to the differences in mineralogy from one ore body to another, the mill process needs to be modified to efficiently extract uranium oxide and this can also result in a change in the chemistry of the tailings that report to the TMF. This has resulted in the concentrations of dissolved ions changing compared to historical values. For example, a study of the pore water collected at different depths in the tailings in 2018 found a considerable increase in the concentration of dissolved Pb, Ni, and Cu compared to samples collected in 2013 and earlier. In this collaboration, we will investigate how the solid species containing Pb, Ni, Cu, and U change depending on the depth (and therefore age) of where the samples were collected. To achieve the goal of having the tailings having no negative impact on the downstream environment, it is necessary to confirm that elements that might have negative environmental impacts on the environment (e.g., Pb, U, Ni) will precipitate under the near-neutral conditions of the TMF to form stable solid endpoints that are unable to transport into the surrounding environment. This investigation will use a combination of X-ray absorption spectroscopy, X-ray microprobe, X-ray photoelectron spectroscopy, and X-ray diffraction to identify the solid Pb-, Ni-, Cu-, and U-bearing species present in the TMF.