Abstract:In order to study process of water - rock reaction and uranium leaching characteristics of sandstone-type uranium deposit during leaching without oxidant, two lab study of distilling water immersion and alkali leaching without oxidant was carried out. The results show that reagent-free water-rock salt ion complex and natural dissolved oxygen in water can weakly migrate uranium into water. Uranium migration intensity in oxidant-free alkali leaching is positively correlated with HCO3- concentration. The HCO3- concentration of 700~900 mg/L is a relatively significant interval for uranium migration. UO2(CO3)22- and UO2(CO3)34- are main dissolved forms of uranium complex in these two lab leaching study, and their proportion is related to HCO3- concentration and pH value. The alkali-impregnated uranium concentration is low since lacking oxidation. Uranium leaching rate for 40 days with L/S=1.5 is 17.17%~22.37%. Uranium leaching rate decays fast, which probably is related to tetravalent uranium content in ore. Nevertheless, the total migration amount of uranium over a long period of time cannot be ignored in alkaline groundwater systems, especially in alkali-drained mining areas.