Abstract:Acid leaching and alkali leaching of uranium are the most important in-situ leaching processes for uranium mining and smelting in China and ore-bearing layer will be blocked during uranium leaching. Ore-bearing layer blockage is a common phenomenon in in-situ leaching of uranium, and it is also a major bottleneck restricting the efficiency of uranium leaching. According to the results of acid column immersion test of Bayan Ula uranium ore and alkaline column immersion test of Shihongtan uranium ore, the causes of ore-bearing layer blockage during acid and alkali uranium leaching were systematically studied. The results show that mineral clay alteration is an important cause of blockage of ore-bearing layer in acidic in-situ leaching, while calcium carbonate precipitation is the main reason for blockage of ore-bearing layer in alkaline in-situ leaching. The pH value, HCO3- concentration and Ca2+ concentration of leaching solution would cause calcium carbonate precipitation in alkaline in-situ leaching of uranium-bearing layer. The solubilization profile of calcium carbonate is controlled by the boundary values of pH value, concentration of Ca2+ and HCO3-.