Search Results (16)

The CO₂+O₂ in-situ leaching (ISL) mining process has been widely applied in the exploitation of sandstone-type uranium deposits; however, evaluating leaching efficiency remains a challenging issue. In this study, a sandstone-type ISL uranium deposit was selected, and based on comprehensive investigations of hydrogeological conditions and mineral geochemistry, a multi-physics coupled numerical model of uranium solute reactions during CO₂+O₂ leaching was established. The model fully accounts for variations in the groundwater flow field between injection and production wells and, on this basis, couples the chemical reaction field between the ore and the leaching solution. The model simulates the evolution of uranium concentration in the leaching solution and further calculates the leaching efficiency of the ore. The results indicate that groundwater flow velocity is highest between injection and production wells, where groundwater dynamics are strongest, and gradually decreases toward the interwell zones as hydrodynamic intensity weakens. Uranium concentration in the leaching solution is closely related to the groundwater flow field. In the early stage, high-uranium-concentration zones are mainly concentrated between injection and production wells. As time progresses, ore reactions in high-flow regions become more complete, leading to a decline in uranium concentration, while residual uranium ions within the formation diffuse outward under concentration gradients, causing high-concentration zones to expand outward. Sensitivity analysis shows that increasing CO₂ and O₂ concentrations significantly enhances uranium leaching concentrations, with increases of approximately 22.1% and 11.3%, respectively. Lower injection-production flow rates reduce dilution and promote more complete reactions, but may also introduce risks such as ore layer clogging. These results provide a theoretical basis and scientific guidance for flow-field regulation in situ leaching uranium mining. Full article

In situ leaching (ISL) of uranium faces challenges in solid–liquid separation of pregnant leaching solution, with conventional bag filters showing suboptimal performance. This study investigates wellbore and ore-bearing layer clogging in neutral ISL uranium mining, characterizing particle size distribution in the leaching solution. Results show that leaching solution particles consist mainly of clay and silt-grade debris (<200 μm). A novel hybrid separation system integrating an optimized hydro cyclone with a bag filter was developed using theoretical fluid mechanics and CFD simulations. The optimized hydro cyclone with a novel swirl chamber and conical inverted wire mesh collector achieves complete separation of particles > 60 μm and 99.9% efficiency for particles > 50 μm. The hybrid system significantly reduces operating pressure and filter bag replacement frequency from three times to once weekly, mitigating ore-bearing layer clogging. This research provides insights into particle migration mechanisms and offers an efficient solid–liquid separation solution for uranium mining operations. Full article

This study presents an integrated geophysical and hydrogeological characterization of fault systems in the sandstone-hosted uranium deposit within the K₁b² Ore Horizon of the Bayin Gobi Basin. Employing 3D seismic exploration with 64-fold coverage and advanced attribute analysis techniques (including coherence volumes, ant-tracking algorithms, and LOW_FRQ spectral attenuation), the research identified 18 normal faults with vertical displacements up to 21 m, demonstrating a predominant NE-oriented structural pattern consistent with regional tectonic features. The fracture network analysis reveals anisotropic permeability distributions (31.6:1–41.4:1 ratios) with microfracture densities reaching 3.2 fractures/km² in the central and northwestern sectors, significantly influencing lixiviant flow paths as validated by tracer tests showing 22° NE flow deviations. Hydrogeological assessments indicate that fault zones such as F11 exhibit 3.1 times higher transmissivity (5.3 m²/d) compared to non-fault areas, directly impacting in situ leaching (ISL) efficiency through preferential fluid pathways. The study establishes a technical framework for fracture system monitoring and hydraulic performance evaluation, addressing critical challenges in ISL operations, including undetected fault extensions that caused lixiviant leakage incidents in field cases. These findings provide essential geological foundations for optimizing well placement and leaching zone design in structurally complex sandstone-hosted uranium deposits. The methodology combines seismic attribute analysis with hydrogeological validation, demonstrating how fault systems control fluid flow dynamics in ISL operations. The results highlight the importance of integrated geophysical approaches for accurate structural characterization and operational risk mitigation in uranium mining. Full article

In situ leaching represents an efficient and safe method for uranium mining, where a suboptimal well flow rate distribution leads to solution imbalances between wells, forming stagnant zones that increase operational costs. This study examines a real technological block from the Budenovskoye deposit, applying reactive transport modeling to optimize well flow rates and reduce operational time and reagent consumption. A reactive transport model was developed based on mass conservation and Darcy’s laws coupled with chemical kinetics describing sulfuric acid interactions with uranium minerals ($U{O}_2$ and $U{O}_3$). The model simulated a technological block with 4 production and 18 injection wells arranged in hexagonal cells over 511–542 days to achieve 90% uranium recovery. Six approaches for well flow rate redistribution were compared, based on different weighting factor calculation methods: advanced traditional, linear distance, squared distance, quadrilateral area, and two streamline-based approaches utilizing the minimum and average time of flight. The squared distance method achieved the highest efficiency, reducing operational costs by 5.7% through improved flow redistribution. The streamline-based methods performed comparably and offer potential advantages for heterogeneous conditions by automatically identifying hydraulic connections. The reactive transport modeling approach successfully demonstrated that multi-criteria optimization methods can improve ISL efficiency by 3.9%–5.7% while reducing operational costs. Full article

In traditional in situ leaching (ISL) uranium mining, the injection volume depends on technicians’ on-site experience. Therefore, applying artificial intelligence technologies such as machine learning to analyze the relationship between injection volume and leaching rate in ISL uranium mining, thereby reducing human factor interference, holds significant guiding importance for production process control. This study proposes a novel uranium leaching rate prediction method based on a CNN–LSTM–LightGBM fusion model integrated with an attention mechanism. Ablation experiments demonstrate that the proposed fusion model outperforms its component models across three key metrics: Mean Absolute Error (MAE), Mean Absolute Percentage Error (MAPE), and Root Mean Square Error (RMSE). Furthermore, comparative experiments reveal that this fusion model achieves superior performance on MAE, MAPE, and RMSE metrics compared to six extensively utilized machine learning methods, including Multi-Layer Perceptron, Support Vector Regression, and K-Nearest Neighbors. Specifically, the model achieves an MAE of 0.085%, an MAPE of 0.833%, and an RMSE of 0.201%. This attention-enhanced fusion model provides technical support for production control in ISL uranium mining and offers valuable references for informatization and intelligentization research in uranium mining operations. Full article

This study was conducted to assess the applicability of artificial neural networks (ANN) for forecasting the dynamics of uranium extraction over exploitation time during the process of In Situ Leaching (ISL). Currently, ISL process simulation involves multiple steps, starting with geostatistical interpolation, followed by computational fluid dynamics (CFD) and reactive transport simulation. While extensive research exists detailing each of these steps, machine learning techniques may offer the potential to directly obtain extraction curves (i.e., the concentration of the mineral produced over the exploitation time of the deposit), thereby bypassing these computationally expensive steps. As a basis, both an empirical experimental configuration and reactive transport simulations were used to generate training data for the neural network model. An ANN was constructed, trained, and tested on several test cases with different initial parameters, then the expected outcomes were compared to those derived from conventional modeling techniques. The results indicate that for the employed experimental configuration and a limited number of features, artificial intelligence technologies, specifically regression-based neural networks can model the recovery rate (or extraction degree) of the ISL process for mineral production, achieving a high degree of accuracy compared to traditional CFD and mass transport models. Full article

The application of In Situ Leaching (ISL) has significantly boosted uranium production in countries like Kazakhstan. Given that hydrodynamic and chemical processes occur underground, mining enterprises worldwide have developed models of reactive transport. However, modeling these complex processes demands considerable computational resources. This issue is particularly significant in the context of numerical analyses of mining processes or when modeling production scenarios in uranium mining by the ISL technique, given that a substantial portion of computational resources is allocated to solving the hydraulic head equation. This work aims to explore the applicability of PINNs to accelerate hydrodynamic simulations of the ISL process. The solution of the Poisson equation is accelerated by generating an initial approximation for the iterative method through the application of the Inverse Distance Weighting (IDW) interpolation and PINNs. The impact of various factors, including the computational grid and the spacing between wells, on both the accuracy and efficiency of initial approximation and the overall solution of the elliptic equation are explored. Employing the hydraulic head distribution obtained through PINNs as the initial approximation led to a significant reduction in computation time and a decrease in the number of iterations by a factor of 2.8 to 7.10. Full article

As a strategic mineral and energy resource, the enrichment and metallogenic mechanism of sandstone-hosted uranium deposits are highly dependent on hydrogeological conditions. However, the relationship between sandstone uranium mineralization and hydrogeological conditions has not received sufficient attention yet. The pumping test, hydrogeological parameters and hydrochemical characteristics were employed to analyze the change characteristics of hydrogeological conditions and evaluate the suitability of in situ leaching (ISL). The results showed that the study area in the Inner Mongolia Autonomous Region could be divided into two groundwater subsystems, namely Quanzha-Engeriyin and Luhai-Zhendai. The latter with relatively high water richness is confined and a main ore-bearing aquifer, which consists of four orebodies. The well discharge (Q) and hydraulic conductivity (K) of Orebody II ranged from 98.40 to 867.36 m³/d and 0.25 to 5.64 m/d, respectively, indicating the aquifer is suitable for the migration, enrichment and mineralization of uranium due to relatively high permeability and fast flow rate. The water storage of Orebodies III-IV gradually deteriorated from east to west in a stepped pattern. And the highest values of Q and K in Orebodies III-IV decreased from 1200 m³/d to 120 m³/d and 1.75 m/d to 0.035 m/d, respectively, suggesting these were conducive to a reduction in and accumulation of uranium under poor hydrodynamic conditions. Additionally, the study area would be defined as three grades, including favorable, relatively favorable and unfavorable areas of ISL according to a comprehensive evaluation. This study provided a scientific basis for evaluating the possibility of in situ leaching for sandstone-hosted uranium deposit. Full article

Uranium, a cornerstone for nuclear energy, facilitates a clean and efficient energy conversion. In the era of global clean energy initiatives, uranium resources have emerged as a vital component for achieving sustainability and clean power. To fulfill the escalating demand for clean energy, continual advancements in uranium mining technologies are imperative. Currently, established uranium mining methods encompass open-pit mining, underground mining, and in situ leaching (ISL). Notably, in situ leaching stands out due to its environmental friendliness, efficient extraction, and cost-effectiveness. Moreover, it unlocks the potential of extracting uranium from previously challenging low-grade sandstone-hosted deposits, presenting novel opportunities for uranium mining. This comprehensive review systematically classifies and analyzes various in situ leaching techniques, exploring their core principles, suitability, technological advancements, and practical implementations. Building on this foundation, it identifies the challenges faced by in situ leaching and proposes future improvement strategies. This study offers valuable insights into the sustainable advancement of in situ leaching technologies in uranium mining, propelling scientific research and practical applications in the field. Full article

Acid in situ leaching (ISL) is a common approach to the recovery of uranium in the subsurface. In acid ISL, there are numerous of chemical reactions among the injected sulfuric acid, groundwater, and porous media containing ore layers. A substantial amount of radioactive elements including U, Ra, Rn, as well as conventional elements like K, Na, and Ca, and trace elements such as As, Cd, and Pb, are released into the groundwater. Thus, in acid ISL, understanding the transport and reactions of these substances and managing pollution control is crucial. In this study, a three-dimensional reactive transport modeling (RTM) using TOUGHREACT was built to investigate the dynamic reactive migration process of UO₂²⁺, H⁺, and SO₄²⁻ at a typical uranium mine of Bayan-Uul. The model considering the partial penetration through wellbore in confined aquifer and complex chemical reactions among main minerals like uranium, K-feldspar, calcite, dolomite, anhydrite, gypsum, iron minerals, clay minerals, and other secondary minerals. The results show that after mining for one year, from the injection well to the extraction well, the spatial distribution of uranium volume fraction does not consistently increase or decrease, but it decreases initially and then increases. After mining for one year, the concentration front of UO₂²⁺ is about 20 m outside the mining area, the high concentration zone is mainly inside the mining area. The concentration front of H⁺ is no more than 50 m. SO₄²⁻ is the index with the highest concentration among the three indexes, the concentration front of SO₄²⁻ is no more than 100 m. The concentration breakthrough curve of the observation well 10 m from the mining area indicates that the concentrations of the three indicators began to significantly rise approximately after mining 0.05 years, reached the maximum value after mining 0.08 to 0.1 years, and then stabilized. The parameter sensitivity of absolute permeability and specific surface area of minerals shows that the concentration of H⁺ and SO₄²⁻ is positively correlated with absolute permeability. The concentration of H⁺ is negatively correlated with the specific surface area of calcite, anhydrite, K-feldspar, gypsum, hematite, and dolomite. The concentration of SO₄²⁻ is positively correlated with the specific surface area of K-feldspar and Hematite, and negatively correlated with the specific surface area of calcite, anhydrite, gypsum, and dolomite. The influence analysis of pumping ratio and non-uniform injection ratio shows that the non-uniform injection scheme has a more significant impact on pollution control. The water table, streamline, capture envelope, and the concentration breakthrough curve of five schemes with different pumping ratios and non-uniform injection ratio were obtained. The water table characteristics of five schemes shown that increase in the pumping ratio and the non-uniform injection ratio, the water table convex near the outer injection well is weakened and the groundwater depression cone near the pumping well is strengthened. This characteristic of water table exerts a notable retarding influence on the migration of pollutants from the mining area to the outside. For the scheme with a pumping ratio is 0 (the total pumping flow rate is equal to the total injection flow rate) and a non-uniform injection ratio is 0 (the flow rate of inner injection well Q1,Q2,Q3 is equal to the flow rate of outer injection well Q4,Q5,Q6), the streamline characteristics shown that a segment of the streamline of is diverging from inner region to the outer region. For other schemes, the streamline exhibits a convergent feature. It is indicated that by increasing the pumping ratio and non-uniform injection ratio, a closure flow field can be established, confining the groundwater pollutants resulting from mining within the capture envelope. Hence, the best scheme for preventing pollution migration is the scheme with a pumping ratio is 0 (the total pumping flow rate is equal to the total injection flow rate) and a non-uniform injection ratio is 0.1 (the flow rate of inner injection well Q₁,Q₂,Q₃ is 10% more than the flow rate of outer injection well Q₄,Q₅,Q₆). In this scheme, the optimal stable concentration of UO₂²⁺, H⁺, and SO₄²⁻ at the observation well obtained by RTM is lower than other schemes, and the values are 0.00316 mol/kg, 2.792 (pH), and 0.0952 mol/kg. The inner well injection rate is 194.09 m³/d, the outer well injection rate is 158.89 m³/d, and the pumping rate is 264.00 m³/d. Numerical simulation analysis suggests that a scheme with a larger non-uniform injection ratio is more conducive to the formation of a strong hydraulic capture zone, thereby controlling the migration of pollutants in the acid ISL. A reasonable suggestion is to adopt non-uniform injection mining mode in acid ISL. Full article

The uranium required for power plants is mainly extracted by two methods in roughly equal amounts: quarries (underground and open pit) and in situ leaching (ISL). Uranium mining by in situ leaching is extremely attractive because it is economical and has a minimal impact on the region’s ecology. The effective use of ISL requires, among other things, the accurate assessment of the host rocks’ filtration characteristics. An accurate assessment of the filtration properties of the host rocks allows optimizing the mining process and improving the quality of the ore reserve prediction. At the same time, in Kazakhstan, this calculation is still based on methods that were developed more than 50 years ago and, in some cases, produce inaccurate results. According to our estimates, this method provides a prediction of filtration properties with a determination coefficient $R^2$ = 0.32. This paper describes a method of calculating the filtration coefficient of ore-bearing rocks using machine learning methods. The proposed approach was based on nonlinear regression models providing a 20–75% increase in the accuracy of the filtration coefficient assessment compared with the current methodology. The work used different types of machine learning algorithms based on the gradient boosting technique, bagging technique, feed-forward neural networks, support vector machines, etc. The results of logging, core sampling, and hydrogeological studies obtained during the exploration stage of the Inkai deposit were used as the initial data. All used machine learning models demonstrated significantly better results than the old method. This resulted in improved results compared with previous studies. The LightGBM regressor demonstrated the best result ($R^2$ = 0.710). Full article

Since the 1990s, sandstone-type uranium in the northern basin of China has become the main target for mining. Uranium mining can cause a series of impacts on the environment. A conceptual model of the geo-environment for sandstone-type uranium in northern China was described, which covers the changes in the geo-environmental characteristics in the natural state, in the mining process, during decommissioning and after treatment. Sandstone-type uranium is mainly distributed in the Songliao, Erlian, Ordos, Turpan–Hami and Ili Basins, which have arid climates and poor stratum permeability. Pitchblende is the main uranium-bearing mineral and is associated with iron, copper, coal, organic matter and other minerals. The mineral often has a low ore grade (0.01–1.0%) and high carbonate content (2–25%). Uranyl carbonate accounts for more than 90% of the total uranium in groundwater. The uranyl content is closely related to the TDS. The TDS of groundwater in the eastern and central ore belts is usually lower than 2 g/L, while in the western region, such as Xinjiang, it can exceed 10 g/L. In situ leaching (ISL) is the main mining method that results in groundwater pollution. Acid leaching leads to a pH decrease (<3), and heavy metals represented by U and Fe exceed the background values by hundreds of times, resulting in groundwater pollution. CO₂ leaching is more environmentally friendly, and the excess ions are usually Ca²⁺, Mg²⁺, NO₃⁻ and HCO₃⁻. Soil chemical anomalies originate mostly from wind erosion and precipitation leaching of decommissioned tailings. Uranium pollution is mainly concentrated within 20 cm of the surface, and the exceedance generally varies from two to 40 times. During ISL, a series of environmental measures will be taken to prevent pollution from being exposed to the surface. After treatment, the decommissioned uranium mines will likely have no impact on the surrounding environment. In the future, the protection of groundwater should be strengthened during production, and remediation methods based on electrokinetic, microbial and permeable reactive barrier (PRB) technology should be further researched. Full article

Without a reliable design method for the leaching and seepage step of in situ leaching (ISL), problems such as low comprehensive resource recovery rate and frequent geological disasters such as landslides are prominent. This study established a simplified “liquid injection-collection” plane model of ISL with a linear barefoot type rare earth mine as the research object. The steady seepage line equation was derived based on groundwater dynamics and the Dupuit assumption. Then, engineering verification and calculation error analysis were performed. The seepage line equation is expressed as a piecewise function, where the seepage line in the liquid injection area is the upper half of the ellipse line, and the one in the non-liquid injection area is a parabola. The calculation error increases along the flow field direction. The seepage gradient, bedrock gradient, liquid injection range, and relative permeability coefficient have limited influence on the calculation error of the equation. The seepage line equation can be fairly applied in ISL. The seepage line equation can provide a theoretical basis for the “prior prediction (design)” of the “liquid injection/collection” leaching and seepage process in ISL. Full article

Unconsolidated sandstone uranium deposits exploited by the in situ leaching (ISL) method, contain complex tetravalent and hexavalent uranium compounds, mostly as UO₂ and UO₃ oxides that have different dissolution rates in sulfuric acid solutions. This work investigates a reactive transport model that takes into account the dissolution of both UO₂ and UO₃ in sulfuric acid solution together with possible interactions with rock minerals during the ISL uranium extraction. Several empirical reaction rate constants were determined during lab experiments on uranium extraction assays, including dissolution rates of tetravalent and hexavalent uranium oxides, and the dissolution rate of rock components by sulfuric acid solution. Effects on the recovery of solution flow rates and ratios between tetravalent and hexavalent uranium compounds are also investigated. The experimental dissolution constants were then used in the proposed reactive transport model to be applied to a real case study in Kazakhstan for comparing the 16 months history matching of an exploitation block consisting of 18 well injectors and 4 producers. The obtained numerical results show good agreement with empirical data gathered during exploitation. Full article

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. Full article