No abstract

Currently, uranium production occupies a decisive place in the world energy industry. In Kazakhstan, to meet the demand for uranium, hydrogenous deposits with technologically and economically favorable natural indicators are being developed, including the large Semizbai deposit. The deposit by genesis belongs to the hydrothermal-hydrogenous polygenic type in terrigenous sandy-clayey deposits. As a result of geological studies, the stratification of the ore-bearing deposits of the Semizbai suite was established: the lower and upper ore-bearing sub suites, the geometrization of the deposit was performed, and the morphology, number, and size of ore bodies were identified. Most of the balance reserves of the Semizbai deposit are concentrated in large and medium ore bodies. Analytical work and description of thin sections and polished sections under a microscope determined the material composition, textures, and structures of uranium ores, the main ore minerals, and their distribution in ores. When carrying out field and laboratory work, geological indicators of the deposit were obtained to select the technology for extracting ores. To select and justify the field development technology, special technological studies were carried out in the experimental area. Based on the geological indicators of uranium ores for the Semizbay deposit, well-in-situ leaching was chosen as the most rational for hydrogenous deposits. The characteristic of associated useful components of uranium ores is given, and the increased content of selenium, germanium, and scandium in them is established. The obtained research results can serve as a basis for improving the technology used for mining uranium ores and extracting associated components from them.

The current goal in uranium mining is to ensure the maximum effect at minimized costs. One of the problems when using the in-situ leaching (ISL) technology consists in the incomplete mining of the process blocks due to premature uranium content reduction in the pregnant solutions, leading to increased mining times and excessive reagent consumption. The required complete block mining shall be ensured with the highest possible efficiency. The ISL technology is currently used for the mining of all hydrogenous uranium deposits in the Republic of Kazakhstan, which are often characterized by complex geological and hydrogeological conditions. One of these deposits, Semizbay, rates as complexity type III. The conditions at the deposit require increasing the redox potential of the solution by oxidizing Fe2+ into Fe3+. The article considers the addition of hydrogen peroxide to the leaching solutions to improve the redox potential with due account of the mining and geological features of the Semizbay deposit. The pilot tests have established that this oxidizing agent has a positive effect on the uranium content in the pregnant solution with the concentrations of 0.2–0.3 l/m3, provided that the concentration of sulfuric acid in the leaching solutions is within the range of 13–15 g/l. The studies allowed increasing the concentration of uranium in the pregnant solutions from 74 to 114 g/l (i.e., by over 50 %). The authors are grateful to the staff of the geotechnology department of the Semizbay mine, Semizbay-U LLP, for collecting the data and to the staff of the IVT-Zerde LLP laboratory (branch of the Semizbay mine) for the high-quality laboratory experiments during the pilot tests at the mine.