The safety of uranium tailings pond is especially important, while static and dynamic mechanical characteristic of uranium tailings is the basement of safety analysis and evaluation of tailings pond. This paper took one of southern uranium tailings pond as research target, and by means of function fitting and picturizing, systematically studied the regularity of space-time distribution of uranium tailings layers, as well as transformation law and inner mechanism of physical, mechanical and dynamic characteristic of uranium tailings, including indexes such as density, void ratio, coefficient of consolidation, filtration coefficient, internal friction angle, cohesion, dynamic modulus of elasticity, dynamic shear modulus and damping ratio. The result can provide an important guiding significance for the construction, operation and safety analysis of uranium tailings pond.

Uranium tailings pond is a major safety and environmental hazard, and it is very important to ensure the safety and reliability under all conditions (including extreme disaster condition). Seismic condition is an important extraordinary working condition affecting the safety of uranium tailings ponds. Focused on the renovation project of a uranium tailings pond, the three-dimensional dynamic finite element method is applied to simulate and analyze seismic condition of uranium tailings pond for the first time. HS small model and UBC3D-PLM model constitutive model are selected to simulate and analyze a uranium tailings pond by dynamic finite element method. Seismic wave characteristic parameters and tailings dynamic characteristic parameters are taken into the finite element seismic dynamic simulation calculation, and the extreme conditions of rare earthquake are considered in the calculation, the displacement nephogram, acceleration nephogram, acceleration time history curve, potential liquefaction range and incremental displacement nephogram are obtained. The results show that the displacement of the dam body increases continuously under earthquake action, and the displacements of dam body decrease obviously after the implementation of the renovation project; there is no obvious change in the acceleration response caused by the renovation project; the liquefaction area is mainly distributed in the slope of the filled dam below the rock-filled platform, mainly in shallow layers (depth of about 3~6 m), and the improvement of liquefaction is limited. The stability safety factor of the dam body under rare earthquake increases from 0.975 to 1.061, the security of rare earthquake condition gets fundamental improvement.

Hard rock uranium mines are an important part of China's natural uranium production capacity. Due to policy adjustments, many hard rock uranium mines are currently in a maintenance state. Production facilities such as ore mining and hydrometallurgy processes are stopped, and only tailings(slag) storage, wastewater treatment and other waste treatment facilities maintain operation. There is a significant difference in radioactive waste emissions from the production period, with an overall reduction in the number and release of source items, and significantly reducing the radiation impact on the surrounding environment and the public. After the shutdown of a typical hard rock uranium mine, the radon concentration and individual dose contribution values decreased by 25.4% to 44.5%. Based on the characteristics of the source terms during the maintenance period, optimization suggestions for environmental protection measures during the maintenance period of hard rock uranium mines are proposed to further reduce the source terms. At the same time, an adjustment plan for effluent and environmental monitoring is provided to ensure timely detection of problems while reducing manpower and increasing maintenance workload, ensuring the radiation safety and controllability of the shutdown mines.

Some uranium mining and metallurgy soil ²²⁶Ra background value can not be determined, because of historical background and decommissioning knowledge in the early year. Based on analyzing the influencing factors of soil ²²⁶Ra value, natural factors determine soil ²²⁶Ra background value and human factors cause the soil ²²⁶Ra value to rise. It is difficult to investigate soil ²²⁶Ra background value at the contaminated site. In order to reduce the influence of human factors, monitoring plan, minimum sample size, and investigation statistical method are researched from surrounding soil of the site. Based on an example of the uranium mining and metallurgy decommissioning site, the feasibility of the supplemental investigation method is verified. The investigation statistical method can provide support for the engineering design and practice of uranium mining and metallurgy decommissioning.

The radioactivity of investigation, analysis and evaluation of liquid effluent such as mine water, tailings pond effluent and process wastewater produced by a uranium mine were conducted, the radioactivity level of liquid effluent and the pollution of accepted water were mastered, and the radiation impact of liquid effluent on local residents through various pollution channels was evaluated. The results show that the discharge concentrations of U, ²²⁶Ra, ²¹⁰Pb and ²¹⁰Po in the mine water, process wastewater and tailings pond effluent meet the limit requirements. The concentration of U in the middle and lower reaches of the accepted water body is slightly higher than the background level, and the concentrations of ²²⁶Ra, ²¹⁰Pb and ²¹⁰Po are among the normal background levels. The maximum personal dose caused by liquid effluent from uranium mine was 1.45×10^-3 mSv/a of 20 km, and the maximum collective effective dose was 2.35×10^-4 man·Sv/a of 20 km. The key resident group was the population group of WNW orientation in the >2~5 km area. The liquid effluent of uranium mining is discharged into the receiving water after reaching the standard, which has little impact on local radiation.

Bayinqinggeli uranium deposit in the northern of the Ordos Basin is hosted in the lower sub-member，lower member of Zhiluo Formation，with an average uranium grade of 0.057 1% and an average uranium mass per square meter of 6.69 kg/m²，but its permeability coefficient is only 0.065 m/d，which is a typical low-permeable sandstone uranium deposit. For this deposit，the well Z5，which has poor injection capacity，is selected to carry out the high energy gas fracturing experiments. The uranium deposit aquifer of the well is located at 619~639 m，and the depth of the propellant is placed at 632.5~637.4 m，626.6~631.6 m，620.6~625.6 m. The amount of the propellant is 40 kg for each time. At the same time of fracturing，microseismic monitoring is carried out around well Z5. There are 59，61 and 49 events generated by the fracturing of three times，and the event profiles show that the fractures formed in the reservoir are trending at 46.8°NW，31.0°NW and 72.3°N，respectively. After fracturing，the injection volume of well Z5 is significantly improved，with an increasement of 126.34%. The high energy gas fracturing can improve the permeability of the near-well area. It is easy to implement and the cost is low.

Based on the efficiency of uranium extraction drilling, a new type of cut-window drilling was developed. The advantages and disadvantages of two different drilling structures were analyzed by comparing the site construction and leaching effect of gravel filling drilling and cut-window drilling. The results show that the construction quality of cut-window drilling is controllable, the drilling operation stability is long, the leaching effect is good, the uranium concentration in the leachate rises quickly, and the recovery rate is high. The comparative use of the two structures provides important theoretical basis and practical application experience for the mining of uranium mine, and the cut-window drilling is helpful to improve the exploitation and utilization of uranium resources.

Blockage of ore bearing layers is the most common technical problem in in-situ leaching of uranium. A certain experimental mining area has been operating for about 200 days, and the injection pressure of the injection well has increased to 1.65 MPa, and the average injection flow rate has decreased by 51.87%, and serious blockage has occurred in the surrounding ore-bearing layers. The calculation shows that when the natural flow field conditions are transformed into the leaching flow field conditions, the groundwater flow velocity can be rapidly increased by tens to hundreds of times. Hydraulic erosion is the dynamic condition for the migration and precipitation of debris in the ore-bearing layers around the pumping well. The mineral debris and chemical precipitation carried in the leaching solution, which are retained in the tail liquid after surface filtration and resin bed adsorption, are re-deposited and accumulated in the ore bearing layer around the injection well, which is the direct cause of its blockage. During the research period, mechanical blockage was the main factor, accompanied by chemical precipitation blockage. Based on the research results of the maximum pore throat diameter of previous ore bearing layers, combined with underground television observation, the particle size of the leaching solution, well washing water, and the chemical composition analysis of the settling dry residue of the well washing water, it is determined that the mineral debris is mainly clay powder sand particle level debris, and the chemical precipitation is mainly CaCO₃, MgCO₃, Fe(OH)₃, with a small amount of FeCO₃. For this reason, with the goal of “preventing blocking”, a hydrocyclone separator has been added. The surface solid-liquid separation system coupled with “natural sedimentation-hydrocyclone separation-mechanical screening” has achieved obvious results, which is expected to be popularized and applied after further research.

Aiming at the steeply sloping broken thin orebody in the Mianhuakeng mine, the continuous mining method of deep hole blasting without inter-pillar was proposed. According to the technological characteristics of the method, the "inverted step shape" + up and down hole layout continuous mining, "positive step shape" + upward hole layout continuous mining and "positive step shape" + top pillar + upward hole layout continuous mining were proposed. The GRA-AHP and cloud model were combined to evaluate and optimize the three mining schemes, and it was concluded that the scheme of "positive step shape" + top pillar + upward hole layout is relatively safe and efficient, which provides a feasible technical scheme for the mining of broken orebody in Mianhuakeng mine.

In order to reduce project construction and land acquisition costs, and shorten the project construction cycle, a in-situ leaching mine adopts a quasi-closed circulation system. Compared with traditional in-situ leaching uranium mines, the liquid distribution tank is cancelled and replaced with a liquid collection tank. As the main power source in the quasi-closed circulation system, the liquid distribution pump is prone to tank overflow when it runs unstable, resulting in imbalanced pumping volume in the circulation system and affecting the production progress of the mining area. By adopting measures such as automated real-time monitoring and optimizing the adjustment mode of the mixing pump, the operational stability of the mixing pump in the quasi-closed circulation system of in-situ uranium leaching has been effectively improved.