Zhang Zhanyuan, Hong Changshou, Li Xiangyang, Wang Hong
School of Resources, Environment and Safety Engineering, University of South China, Hengyang 421001, China.
ACS Omega. 2024 Apr 18;9(17):19295-19310. doi: 10.1021/acsomega.4c00374. eCollection 2024 Apr 30.
The majority of uranium mill tailing impoundments in the southern part of China are located in humid subtropical regions where persistent rainfall and rapid evaporation of water after rain often occur. Under the prolonged influence of alternating wet and dry conditions, the covering soil layer of uranium mill tailing impoundments develops cracks, leading to the issue of degradation or even failure of the radon retardation effect. A beach surface of uranium mill tailing impoundments in the southern part of China is selected as the research object. Through use of a self-made simulation test device, a degradation experiment of uranium mill tailing covering soil models under wetting-drying cycles was conducted indoors. The experimental results indicate that with a constant amplitude of wetting-drying cycles, microcracks characterized by a narrow width and high abundance were mainly generated in the early-to-mid-stage of wetting-drying cycles. The main cracks, characterized by their wide width and less abundance, were mainly formed in the mid-to-late stage of wetting-drying cycles. After seven wetting-drying cycles, the total length of cracks showed a "stair-step" increase and the surface crack ratio exhibited a trend of moving from rapid growth to stable growth and then to a slight decline. The cumulative damage degree showed a rapid increase to stable growth with an increase in the number of wetting-drying cycles. Grey relational analysis revealed that, compared to other surface crack indicators, radon exhalation rate was the most closely correlated with the surface crack ratio. With a constant amplitude of wetting-drying cycles, the radon exhalation rate underwent four stages as the number of wetting-drying cycles increased: stage I witnessed a rapid increase, stage II witnessed a rapid decrease, stage III witnessed a gradual increase, and stage IV witnessed a stable or even slight decrease. With a constant number of wetting-drying cycles, the radon exhalation rate correspondingly increased with the amplitude of wetting-drying cycles, particularly noticeable when the alternation amplitude was 30 ± 20%. From the early mid-stage to the late stage of wetting-drying cycles, the curves of the radon exhalation rate, surface crack ratio, and cumulative damage degree tended to be consistent, showing a gradual increase. The research provided in this study offers valuable insights into radon control measures and environmental assessments on the beach surface of uranium mill tailing impoundments.
中国南方的大多数铀矿尾矿库位于湿润亚热带地区，这里经常持续降雨且雨后水分蒸发迅速。在干湿交替条件的长期影响下，铀矿尾矿库的覆盖土层出现裂缝，导致氡气阻滞效应退化甚至失效的问题。选取中国南方某铀矿尾矿库的滩面作为研究对象。通过自制模拟试验装置，在室内开展了干湿循环作用下铀矿尾矿覆盖土模型的劣化试验。试验结果表明，在干湿循环幅度恒定的情况下，干湿循环中前期主要产生宽度窄、数量多的微裂缝，干湿循环中后期主要形成宽度宽、数量少的主裂缝。经过7次干湿循环后，裂缝总长度呈“阶梯式”增长，表面裂缝率呈现出从快速增长到稳定增长再到略有下降的趋势。累积损伤度随干湿循环次数增加呈快速增长至稳定增长。灰色关联分析表明，与其他表面裂缝指标相比，氡析出率与表面裂缝率的相关性最为密切。在干湿循环幅度恒定的情况下，随着干湿循环次数增加，氡析出率经历四个阶段：第一阶段快速上升，第二阶段快速下降，第三阶段逐渐上升，第四阶段稳定甚至略有下降。在干湿循环次数恒定的情况下，氡析出率随干湿循环幅度的增大而相应增加，当交替幅度为30±20%时尤为明显。从干湿循环中前期到后期，氡析出率、表面裂缝率和累积损伤度曲线趋于一致，呈逐渐上升趋势。本研究为铀矿尾矿库滩面的氡控制措施及环境评价提供了有价值的见解。
