Abstract:Effects of pH values, particle sizes and soaking time on release of uranium and thorium radioactive elements in waste uranium tailings were investigated. Tailings samples to be tested were divided into three particle size ranges, i.e., -0.45 mm, 0.45-8 mm and +8 mm, and continuously soaked for 42 days with pH values of 4.0, 5.0 and 6.0 respectively. The results show that the smaller the size of tailings is, the greater the release amount of radioactive uranium and thorium is. Thorium is more difficult to be leached than uranium under the same environmental conditions. The maximum release amount of uranium and thorium with particle sizes of -0.45 mm is 8.42 mg/L and 0.151 mg/L, respectively.