Geotechnical behavior of uranium mill tailings from Saskatchewan,Canada

This paper investigates the geotechnical behavior of uranium mill tailings from Saskatchewan, Canada.The 4% tailings were well-graded with 29% fines whereas the 5% and 6% tailings were gap-graded with 49% fines. All samples exhibited a negligible strength(0.4 k Pa) up to 60% solids, followed by a rapid increase. The 4% tailings exhibited a lower rate and amount of settlement than 5% and 6% tailings. The kidecreased from 10^(-2)to 10^(-4)m/s with a decrease in eifrom 16 to 4 and a decrease in ef from 8 to 4 such that 4% tailings showed one order of magnitude lower values than the 5% and 6%tailings. The settling potential decreased ten times(50%–5%) for 4% tailings and four times(60%–15%)for 5% and 6% tailings. The effective stress increased from 80 to 260 Pa in the settling tests. The 4%tailings were less prone to segregation when compared with 5% and 6% tailings. The average solids content after settling was 35% for 4% tailings, 40% for 5% tailings and 39% for 6% tailings with a solids content deviation of ±3%, ±8%, ±6%, respectively. All materials were essentially non-segregating at 40%initial solids.

Estimating Radon Flux and Environmental Radiation Dose from Decommisioning Uranium Mill Tailings and Mining Debris

Based on a case study on uranium mine No.765 of China National Nuclear Corporation (CNNC), the paper briefly describes disposal program and effect of decommissioning uranium mine/mill facilities and quantitatively evaluates radon fluxes and doses to man of gaseous airborne pathway from mill tailings and mining debris before and after decommissioning, including annual individual effective dose to critical groups and annual collective effective dose to the population within 80 km region of the facilities.

Effect of Natural Zeolite on Pore Structure of Cemented Uranium Tailings Backfill

The use of some environmental functional minerals as backfill-modified materials may improve the leaching resistance of cemented uranium tailings backfill created from alkali-activated slag(CUTB),but these materials may participate in the hydration reaction of the cementitious materials,which could have a certain impact on the pore structure of the CUTB,thus affecting its mechanical properties and leaching resistance.In this paper,natural zeolite is selected as the backfill-modified material,and it is added to alkali-activated slag paste(AASP)and CUTB in cementitious material proportions of 4%,8%,12%,and 16%to prepare AASP mixtures and CUTB mixtures containing environmental functional minerals.After the addition of natural zeolite,the porosity of the CUTB generally increases,but when the content is 4%,the porosity decreases to 22.30%.The uniaxial compressive strength(UCS)of the CUTB generally decreases,but the decrease is the smallest when the content is 4%,and the UCS is 12.37 MPa.The addition of natural zeolite mainly reduces the number of fine pores in the CUTB,but the pores with relaxation times T_(2)of greater than 10 ms account for about 10%of the total pores,and there are a certain number of large pores in the CUTB.The main product of alkali-activated slag is calcium(alumino)silicate hydrate(C-(A)-S-H gel).When natural zeolite is added,the hydration products develop towards denser products with a high degree of polymerization and the formation of low polymerization products is reduced.This affects the internal fracture pores of the hydration products and the interface pores of the CUTB,has an irregular effect on the pore characteristics of the CUTB,and influences the UCS.

Radioecological Assessment of the Uranium Tailings in Tuyuk-Suu （Kyrgyzstan）

Radioecological Assessment of the Uranium Tailings in Tuyuk-Suu （Kyrgyzstan）. The aim of our research is the radioecological assessment of the current state of uranium tailings in Tuyuk-Suu. The methods of field and laboratory analysis were conducted with the modem radiological and nuclear physics equipment. Gamma survey was shown that the surface of the tailings Tuyuk-Suu and Taldy-Bulak may effectively reduce the exposure dose of gamma radiation, the body Tuyuk Suu is flooding with water flowing near the river in a concrete channel, so it should be constantly monitoring the state of the tailings and the river Tuyuk-Suu. In this article is given the analysis and estimates of the current radiation condition of the tailings dam and Min-Kush settlement. It was for the first time made the radiological analysis after closing of the uranium tailings in a body of the most tail material and it is estimated states possible pollution to environment.

Mill tailings based composites as paste backfill in mines of U-bearing dolomitic limestone ore

This paper elaborates on the development of paste backfill using mill tailings generated during the processing of a uranium ore deposit hosted in dolomitic limestone. The tailings have been characterized in terms of the physical, chemical and mineralogical properties. Time-dependent rheological behaviors and geotechnical properties of cemented paste backfill(CPB) are also determined. The studies show that the mill tailing has the potential to form paste and the CPB has adequate strength to provide support to mine pillars, roofs, and walls.

Natural Radioactivity in Miscanthus floridulu Plant from the Uranium Tailing Pile at Guangdong, South China

Large amounts of uranium waste rocks and tailings resulting from the exploitation and treatment of uranium ore at the Northern Guangdong mine (South China) have been accumulated in dams (tailing ponds). To reduce the dispersion of natural radionuclides into the environment, some dams were revegetated with arbor, bush and sward. Besides these plants, Miscanthus floridulu is the dominant plant growing in some of the dams. The uptake and distribution of naturally occurring uranium (238U), thorium (232Th), radium (226Ra) and potassium (40K) by Miscanthus floridulu plant from different sample sites of uranium mine were studied under native conditions. The bioconcentration factors (BCFs) of soil to Miscanthus floridulu above-ground and root were calculated and observed to be in the range of 0.14 to 7.74 and 2.71 to 17.83 for 238U, 0 to 3.02 and 0 to 3.29 for 232Th, 0.15 to 79.76 and 1.01 to 50.22 for 226Ra and 3.00 to 8.41 and 2.69 to 11.22 for 40K, respectively. The transfer factors (TFs) of Miscanthus floridulu root to aboveground were also calculated and observed to be in the range of 0.01 to 0.73 for 238U, 0 to 0.99 for 232Th, 0.08 to 1.50 for 226Ra and 0.57 to 1.94 for 40K, respectively. The results showed that, Miscanthus floridulu is 238U and 226Ra-accumulating plant with significant absorption and accumulation characteristics.

铀尾矿库渗排水中氨氮电氧化去除影响因素研究

氨氮废水是全球水处理难点之一。在铀矿开采、选冶过程中会产生放射性固体废物并存储在铀尾矿库中,由于雨水的作用尾矿库产生大量废水,将有害物质浸出到水中形成渗排水,铀尾矿渗排水具有高盐、高氨氮、可生化性差、含较高氯离子的特点,现有方法无法有效处理此类废水。电氧化法可清洁高效地去除废水中的氨氮,氨氮去除率主要受Cl−浓度、极板材料、电流密度、pH等的影响。本文通过单因素实验对这些因素进行研究,通过正交分析,探索各因素对氨氮去除率的影响程度,根据影响程度由高到低排序为Cl−浓度>极板材料>电流密度;pH为次要影响因素,为电化学反应提供碱性环境。通过比较各条件对氨氮去除率提高的明显程度,推荐使用Ti/RuO_(2)-IrO_(2)-SnO_(2)电极组,其最优条件为Cl−浓度1000 mg/L、电流密度20 mA/cm^(2)、电解时间3 h、pH=9~11,在此条件下氨氮的去除率达100%,氨氮出水满足《铀矿冶辐射防护和辐射环境保护规定》(GB 23727—2020)和《污水综合排放标准》(GB 8978—1996)的要求。

铀矿尾矿氡射气系数测量方法及主要影响因素研究

放射性矿物以及放射性伴生矿物在开采过程中,由于岩石破碎处理,改变了矿石原有的物理结构,引起氡气射气系数和迁移特性的改变,造成尾矿氡气排放超标等环境问题。测定尾矿射气系数以及研究射气系数主要影响因素,对尾矿氡气防护与治理具有重要意义。本文以铀矿尾矿射气系数为研究对象,搭建了射气系数测量装置,并利用装置测量了不同粒径和温度条件下样品的射气系数。依据实验数据建立了射气系数与温度和粒径的关系和经验公式。实验结果表明,在5目~30目的粒径范围内,射气系数与样品成幂指数关系,随着样品粒径减小而增大;射气系数与温度存在正相关性,在20~40℃范围内,存在线性关系。得到的经验公式可用于铀矿尾矿氡气浓度模拟计算,为尾矿氡气治理提供基础数据。

电化学滤池处理铀尾矿渗滤液的效能研究

为高效、低碳处理铀尾矿渗滤液,研发了一种新型石墨基电化学滤池,以石墨颗粒为填料、碳毡为导电体,通过直流电源提供电压,蠕动泵驱动,自下而上将铀尾矿渗滤液通过不循环连续运行的滤池,实验探究施加电压和水力停留时间等操作参数对模拟含铀废水以及实际铀矿废水的铀去除效能。结果表明:4.0 V和10 h分别为电化学滤池处理铀尾矿渗滤液的最优电压和水力停留时间,该工况下铀的去除率可达到97%以上。采用场发射电子扫描显微镜及能谱(FESEM-EDS)、X射线光电子能谱(XPS)等对反应后石墨颗粒上的产物进行了表征,表征结果表明:铀均匀地分布在石墨颗粒表面,吸附-还原为铀去除的主要机制,铀回收产物以U(Ⅳ)和U(Ⅵ)的混合物的形式沉积于电极表面。同时,通过成本估算可得,利用本装置从铀尾矿渗滤液中回收铀的运行成本为176.6~587.5元/kg(以U计),远低于常规陆地铀资源开发成本,具备良好的经济性。

基于信赖域策略寻优的后退虚源法面源氡扩散模型

在使用面源高斯扩散模型模拟铀尾矿库核素氡扩散浓度时,面源积分模型计算复杂,后退虚源模型模拟结果不准确且不具备保守性。针对上述问题,提出了基于信赖域算法的函数与参数寻优方法。通过构建近似后退虚源模型的非线性函数集,将面源积分模型与函数库中每个函数模拟值之间的误差作为目标函数,在信赖域策略下调用函数库并迭代寻优,输出函数库中最优函数与其最优参数值。通过浓度分布对比与拟合测验得出:优化函数在近源处的模拟值略大于面源积分模型,表明优化函数具备一定的保守性;模拟值与面源积分模型的拟合决定系数在近源处高于0.91,大部分区域高于0.98,说明其模拟结果可靠;同时,优化函数保留了后退虚源模型计算简便的特点。此外,根据误差的影响因素分析,优化函数对于面源面积和大气稳定度不变时,能适应其他参数的变化,大大简化了实际氡浓度评估时的计算过程。

华南铀尾矿附近土壤和水体中铀的分布与污染评价

在统计近10年来我国南方铀尾矿土壤和水体中铀污染相关文献数据的基础上,采用单因子指数法和潜在生态危害指数法对铀尾矿的土壤和水体中铀的分布及其污染状况进行了分析探讨。结果显示,当以各地区的背景值作为参照时,土壤和水体铀含量的变异系数(CV)分别为109.9%和103.5%,表明铀的分布不均匀。土壤、水体中铀的单因子污染指数范围分别为0.45~17.63和1.44~140.31,平均值分别为4.83和24.63;内梅罗综合污染指数范围分别为0.90~13.42和4.40~425.53,平均值分别为13.42和46.35,潜在生态风险危害系数E_(r)^(i)范围分别为17.82~705.24和57.42~5612.24,平均值分别为193.19和985.03。华南地区铀尾矿土壤、水体中铀的含量较高,且各分区中铀的分布不均匀,存在较大差异。华南地区铀尾矿土壤和水体的污染及生态风险值得进一步关注。

基于微生物还原的铀尾渣修复技术实验研究

通过实验,探索了初始pH值、温度、菌液添加量和固液比对铀尾渣微生物修复效果的影响,对比了修复前后尾渣中铀赋存形态和微生物群落结构变化。结果表明:从铀尾渣中筛选的硫酸盐还原菌能够有效降低铀尾渣浸出水中的铀浓度;修复效果与初始pH值、温度、菌液添加量正相关,与固液比无显著相关关系;即使在pH=3或温度为15℃的不利条件时,铀尾渣浸出水铀浓度可分别降至0.04 mg/L和0.019 mg/L,修复效率分别为96.9%和93.6%,仍有较好的修复效果;修复后铀尾渣中残渣态铀含量提高了14.6%~18.7%,功能微生物丰度上升2.9%~12.2%,难溶解铀的质量占比和还原性微生物数量显著增加,修复具有稳定性。研究结果证明了铀尾渣污染微生物修复技术的可行性。

降低铀尾矿库浸润线的技术实践

尾矿库溃坝的主要原因有渗流破坏、坝坡失稳、地震液化和超高堆坝等,尾矿坝内浸润线过高可能产生渗流破坏,严重的将造成坝坡失稳、破坏甚至溃坝。降低坝体浸润线的常用方法存在施工难度大、人工维护成本高、设备维护管理复杂等问题,采用水平排渗方式在接近水平的排渗盲沟内装设水平滤管,以达到降低浸润线的目的。本工程采用在坝体内部打设水平孔,并在孔内安装渗水管形成水平排渗体,排渗管通过坝体外的集水总管形成排渗网;坝体内的水渗入排渗管,然后汇至集水总管,最终通过自流排至坝外。该法具有造价低、能耗小、便于管理等优点,是降低尾矿坝浸润线的切实可行的方法。

某铀尾矿库尾矿物理力学特性研究

铀尾矿库的安全至关重要,铀尾矿的静动力学特性是进行尾矿库设计和安全分析评价的基础。以中国南方某铀尾矿库为研究对象,通过对现场钻探和室内试验数据进行函数拟合化和图像化分析,系统研究了该铀尾矿库地层的时空分布规律,以及密度、孔隙比、固结系数、渗透系数、内摩擦角、粘聚力、动弹性模量、动剪切模量、阻尼比等铀尾矿物理力学及动力特性的变化规律和内在机理,研究成果可为铀尾矿库的安全分析和安全运行提供指导。

某铀矿液态流出物放射性调查及环境影响评价

对某铀矿产生的矿井水、尾矿库流出水、工艺废水等液态流出物的放射性进行调查、分析和评价,掌握液态流出物的放射性水平和受纳水体的污染情况,评价液态流出物通过各种污染途径对当地居民造成的辐射影响。结果表明,矿井水、工艺废水和尾矿库流出水经处理后,废水中的U天然、^(226)Ra、^(210)Pb和^(210)Po的排放浓度均满足限值要求;受纳水体下游河段中的U天然浓度稍高于本底水平,^(226)Ra、^(210)Pb和^(210)Po浓度均属正常本底水平。铀矿排放的液态流出物致20 km范围内居民最大个人剂量为1.45×10^(-3)mSv/a,最大集体有效剂量为2.35×10^(-4)人·Sv/a,关键居民组为WNW方位、>2~5 km区的人口组。该铀矿液态流出物在处理达标后排入受纳水体,对当地的辐射影响较小。

某铀尾矿库渗滤液综合处理工艺研究

针对含铀、锰、氨氮等多种污染物的铀尾矿库渗滤液,采用离子交换法回收铀、电絮凝除重金属和气膜回收氨氮工艺进行综合回收处理。验证了离子交换法回收铀的效果;考察了电絮凝法在不同原水pH、曝气时间和电絮凝时间等条件下,对铀、锰等重金属离子的去除效果;研究了在不同氨氮浓度下,气膜对废水中氨氮的分离效果。结果表明,树脂对铀的一级去除率可达95.7%;在不调整原水pH(pH=7.5)和不曝气的条件下,电絮凝效果较好,电絮凝5 min出水中的铀和锰质量浓度分别降至99.79μg/L和0.06 mg/L;当原水中氨氮质量浓度低于297.00 mg/L时,经过气膜一次处理对氨氮的去除率大于99%,出水氨氮质量浓度降至1.91 mg/L。该渗滤液综合处理工艺可实现铀和氨氮的回收,以及多类污染物的达标。

基于SBAS-InSAR和BPNN的铀尾矿坝形变智能监测与预测

为提高铀尾矿库退役治理的监测工作效率,提出一个基于小基线合成孔径雷达干涉测量(SBAS-InSAR)技术和反向传播神经网络(BPNN)的铀尾矿库形变智能监测与预测模型。首先,利用SBAS-InSAR技术得到铀尾矿库2020年12月—2022年12月的累计形变量与年均形变速率,并用第一拦水坝的7个全球导航卫星系统(GNSS)监测站验证InSAR监测值的精度;然后,选取铀尾矿库中的雷公塘坝、南坡横坝、战斗坝和松林坝4个坝段的累计沉降量并结合降雨量进行沉降分析;最后,随机提取铀尾矿坝100个沉降点的累积沉降数据,通过BPNN预测铀尾矿坝的形变。结果表明:2年间铀尾矿库的形变速率在-60.06~34.94 mm/a,铀尾矿坝整体处于下沉状态,累计沉降量最大为-46.67 mm。BPNN预测值与实际监测值的平均绝对误差为0.586 mm,均方误差为0.624 mm。

某铀尾矿库整治工程的三维地震动力响应研究

铀尾矿库是重大危险源,在各种工况(包括极端灾害条件)下均应确保其安全可靠。地震工况是影响铀尾矿库安全的重要工况之一,采用三维动力有限元法对某铀尾矿库整治工程进行了地震模拟分析,选择考虑小应变刚度的硬化土模型和液化土模型作为本构模型,考虑罕遇地震的极端工况,将地震波特征参数和尾矿动力特性参数输入有限元地震动力模拟计算中,得到各工况尾矿库的位移云图、加速度云图、加速度时程曲线、潜在液化范围、增量位移云图等。结果表明,在地震作用下,坝体位移呈现累积增大的特征,整治工程实施后坝体位移明显降低;整治工程未对加速度反应造成明显改变;液化区主要分布在块石反压平台以下的堆积坝体,以浅层(深度约3~6 m)液化为主,对液化情况改善有限;整治工程实施后,罕遇地震工况下的最小安全系数由0.975提升至1.061,安全性得到了根本提升。

某铀尾矿渗滤液在黏土层渗滤过程中铀形态的转化

铀尾矿存在着残留的铀,在水流的作用下,会溶解出来,随着渗滤液的流动而在包气带与地下水中迁移,渗滤液中铀的赋存形态会影响着铀的迁移。本研究采用动态柱进行铀尾矿淋溶与渗滤液在黏土中迁移实验,采用PHREEQC软件模拟计算铀的赋存形态,分析铀的迁移。实验结果表明,淋滤液从尾矿中浸出的铀质量浓度很低,尾矿底部的黏土层对低质量浓度铀的吸附效率不高,而且尾矿渗滤液呈酸性,尾矿中的H+与SO_(2)-4极易随淋滤液的迁移而迁移,黏土对其吸附能力不强。铀在尾矿渗滤液和黏土穿透液中的形态主要有四种,其相对质量浓度顺序为UO_(2)F^(+)>UO_(2)SO4>UO_(2)+2>UO_(2)(SO_(4))^(2-)2,铀的赋存形态在黏土层迁移过程中不会发生明显变化,F-、SO_(2)-4是影响溶解态铀迁移的主要因素。该研究可以为铀尾矿地下水修复与铀土壤污染修复提供理论基础。

铀尾矿中铀、钍及部分金属的模拟淋浸实验初探

模拟广东某地区降雨的几种要素,对该地某铀矿区的两种粒径(<0.45 mm和>6 mm)的铀尾矿,分别采用1 h及24 h的初始浸泡时间、pH=3.0及pH=6.0的淋浸剂,以开放体系,进行7周的半动态淋滤实验,初步考察铀尾矿中铀钍的释放规律及其与金属元素Al、K、Mg释放行为的相关性.结果表明:(1)对铀尾矿释放铀能力的影响作用依次为:粒径>pH>浸泡时间;对钍释放能力的影响作用依次为:pH>粒径>浸泡时间.(2)pH、粒径和浸泡时间的改变将影响U与Th、Al、K和Mg的释放相关性.