In the process of acid in situ leaching of sandstone uranium ore, pyrite, which is a common associated mineral of pitchblende, would inevitably participate in the reaction. Therefore, it is important to study the influence of pyrite on the leaching kinetics of pitchblende. In this study, we compared the difference leaching rates of pitchblende in the systems of sulfuric acid–hydrogen peroxide, sulfuric acid–hydrogen peroxide–pyrite and sulfuric acid–pyrite and studied the influence of temperature and pyrite quantity on the leaching rate of pitchblende. The results show that the leaching process of pitchblende follows the shrinking particle model controlled by a chemical reaction, and the apparent activation energy Ea of the leaching reaction is (3.74 ± 0.40) × 10 kJ/mol. Pyrite itself cannot promote the dissolution of pitchblende; however, it can promote the leaching of pitchblende in the presence of an oxidizer. Increasing the quantity of pyrite in a certain range can increase the leaching rate of pitchblende, and the reaction order of pyrite is 0.36.

Reasonable control of the leaching range is one of the critical indicators of the in-situ leaching uranium mining process. However, there is currently no mature control technology. To verify and improve the current control technology of the leaching range in the industry, this work proposes an injection control mode for a small flow around the well-site and establishes a hydrodynamic model of the leaching range under eight different pumping and injection conditions by using the groundwater modeling system (GMS). The model calculation, range prediction, comparative analysis, and on-site SO₄²⁻ and S isotope verification tests were carried out. Results show that with the change of liquid injection ratio, the area ratios of fixed pumping injection ratio (total pumping flowrate is greater than 0.3% of the total injection flowrate) and model leaching range under four pumping injection equilibrium conditions were 99.10%, 99.99%, 98.30%, and 97.95%, respectively. The farthest migration distance ratios of the leaching solution were 99.37%, 100%, 98.02%, and 97.58%, respectively. It is considered that the operation mode with a fixed pumping injection ratio has no noticeable control effect on the leaching range; selecting a reasonable proportion to regulate the flowrate of injection wells at different positions can effectively reduce the area of the groundwater flow field and realize the effective control of the leaching range. The research results are conducive to saving a lot of evaporation pool construction, land acquisition, human and material resource investment, and environmental policy pressure.

Uranium resource distribution and accurate reserve evaluation are important references for mineral investment and production. Eight kinds of interpolation methods in the Groundwater Modeling System (GMS), including ordinary kriging (OK), are used in this study to predict the spatial distribution of reserve-related parameters, such as uranium grade, ore thickness and uranium content per square meter. The present study draws the following conclusions: (1) Cross-validation found that the uranium grade value using the spherical method is the closest to the actual value. The spherical method has the best interpolation effect. (2) The relative error, which is +3.62%, between the uranium reserves that is calculated by the spherical interpolation method and that by the traditional calculation value is the smallest. (3) The setting of the number of interpolation grids is related to the actual number of boreholes. The ratio between the two will affect the accuracy of reserve estimation, and different interpolation methods have different degrees of influence on reserve estimation. This method is applicable to all in-situ leaching sandstone uranium mines. Further study needs to be carried out toward heterogeneity of three-dimensional space, which will make the estimation more accurate.

In situ leaching (ISL) uranium mining technology is an in situ mining technology in which the chemical solution is injected into the ore-bearing strata through drilling wells, and the solution moves along the ore bed by controlling the hydraulic gradient of the flow field and reacts with the ore to form uranium-bearing solution. To reduce leaching dead angle in the process of leaching, each pumping and injection unit should achieve uniform leaching at the end of production, and appropriate pumping and injection mode should be adopted for pumping and injection wells of each unit in the mining area. In this paper, on the basis of the actual production data of a sandstone uranium mine, we established the unit flow model of ISL uranium mining area by using GMS software. The unit flow balance of 72 boreholes in the whole mining area was analyzed and optimized through the model. The concept of flow microbalance of pumping and injection unit in the mining area is put forward for the first time, and the calculation equation of supply and receive the flow of pumping and injection well is determined. The calculation and analysis process of flow microbalance of pumping and injection unit in mining area is established. The simulation results showed that the application effect of the model was good, and the correlation coefficient of the solute transport model reached 0.8.