Modelling and simulation of vacuum filtration of ore slurry: a case study on limestone-hosted Indian uranium ore

This paper discusses the results of vacuum filtration studies carried out on a finely ground uranium ore slurry with the objective of maximizing the filtration rate. Constant-pressure experiments were carried out to determine the filtration parameters such as specific cake resistance, cake permeability and medium resistance. The experimental data were analysed using the well-known power law function of the cake-forming pressure with specific cake resistance and cake concentration. The power law model equation developed was experimentally validated and the predicted values agreed very well with the experimental findings with >95% confidence level. This study helps in design and scale-up of filtration units to be used at industrial – size.

Cet article discute des résultats d’études de filtration sous vide effectuées avec une suspension de minerai d'uranium moulu finement, ayant pour objectif de maximiser la vitesse de filtration. On a effectué des expériences à pression constante afin de déterminer les paramètres de filtration comme la résistance spécifique du comprimé, la perméabilité, la résistance moyenne etc. On a analysé les données expérimentales en utilisant la fonction bien connue de la loi exponentielle de la pression de formation du comprimé, avec sa résistance spécifique et sa concentration. On a validé expérimentalement l’équation développée pour le modèle de loi exponentielle. Les valeurs prédites s'accordaient très bien avec les données expérimentales, avec un niveau de confidence > 95%. Cette étude aide à la conception et à l'agrandissement à l’échelle d'unités de filtration pour utilisation à l’échelle industrielle     

国营二二一厂核设施退役实践

本文介绍原核工业国营二二一厂的核设施退役实践。文中概述了退役工程的前期准备,退役执行标准或限值,退役工程的组织管理和质量保证体系,退役工程的施工,去污方法,施工辐射监测,污染物处置,终态验收以及退役中的辐射防护等。退役工程经国家验收后,原二二一厂的厂房、设施和场地已经移交青海省安排使用。     

贫化铀的环境污染影响及其对人体健康的危害

贫化铀是铀富集过程中产生的副产品。由于其独特的物理特性,被广泛开发利用到民用和军事用途。“海湾战争综合症”和“巴尔干综合症”引起了人们对贫铀使用后,对环境污染的影响和对人体健康效应研究的重视。贫铀的危害来自化学毒性和放射性毒性两个方面。由于贫铀的放射性比活度低,而且主要发射α粒子,所以来自贫铀的辐射伤害主要是吸入贫铀气溶胶后对肺和其他器官较长时间的内照射。     

尾矿库中U、Th和226Ra在亚粘土层的垂向迁移

在某铀尾矿库运行了31年后,取库底下方的亚粘土样,测量了从库底迁移的U、Th和226Ra的比活度分布.为研究其迁移规律,还测量了尾矿的颗粒分布、不同颗粒尾矿中核素的比活度和浸出因子、核素在亚粘土层的分配系数等参数,并采用一维对流弥散模式拟合得到核素在亚粘土层中比活度分布曲线.结果表明,矿泥是尾矿中的主要成分,其中的核素比活度高于矿砂;而浸出因子则低于矿砂.库底下方天然的和建库时人工铺垫的亚粘土层对三种核素具有较强的吸附滞留能力,从而有效地减少了核素的垂向迁移;U、Th和226Ra在亚粘土中的分配系数分别为62、1.3×103和9.8×102 mL/g,在库底下方核素比活度降到本底水平的距离,U为1.2 m,Th和226Ra为0.2 m.     

Recovery of oxalate from scrubbing solution containing rare earths and iron produced during uranium recovery from phosphoric acid

A solution containing oxalate complexes of rare earths, yttrium and iron (III) is obtained during the processing of wet process phosphoric acid for uranium recovery by solvent extraction. A process is described to recover oxalic acid from such a solution. The process is based on the conversion of iron (III) oxalate into calcium oxalate by calcium chloride followed by the metathesis of calcium oxalate with sulphuric acid to produce calcium sulphate and free oxalic acid. Data is presented to illustrate the influence of various parameters such as pH, temperature, digestion time and amount of calcium chloride on effective conversion of calcium oxalate. Under optimized conditions of pH 1, digestion time 2 h, twice the stoichiometric ratio of calcium chloride at ambient temperature (30±1°C) the recovery of calcium oxalate was found to be >94%. An overall schematic material balance flow -sheet for treating the oxalate solution of rare earths, yttrium and iron (III) to oxalic acid recovery has been presented. An improvement in the second cycle of patented process flow-sheet based on 1.5 M D2EHPA + 0.2 M TBP incorporating oxalic acid scrubbing / recycle for uranium recovery from phosphoric acid has been tested and found to be simple in terms of operations and capable of meeting product specifications..     

Treatment of tissue paper containing radioactive waste and electrochemical recovery of valuables using ionic liquids

Dissolution of tissue paper waste containing valuable contaminants such as uranium and palladium in 1-butyl-3-methylimidazolium chloride (bmimCl) has been studied. Dissolution of 5-7 wt.% tissue paper in bmimCl is complete within 60 min at 373 K and the time required for dissolution increases with increase of loading. It is difficult to dissolve more than 10 wt.% tissue paper in bmimCl and the limiting solubility of tissue paper is 15-17 wt.% at 373 K. Uranium(VI) and Pd(II) in chloride/nitrate form dissolve in bmimCl along with tissue paper. The electrochemical behaviour of uranium(VI) and palladium(II) in the resultant solution in the presence and absence of a co-solvent, DMSO, has been investigated by transient voltammetric techniques at glassy carbon working electrode and the diffusion coefficients have been determined. Electrolysis of a solution of uranium(VI) and palladium(II) loaded tissue paper in bmimCl results in deposition of uranium oxide (UO₂) and metallic palladium, respectively, which were characterized by X-ray diffraction and scanning electron microscopy. The study established the possibility of dissolving tissue paper and other cellulose based materials containing soluble uranium(VI) and Pd(II) compounds in bmimCl, and their recovery from the resultant solution. Cellulose pulp can be regenerated by adding surplus water after the recovery of valuables and the ionic liquid, bmimCl, can be regenerated for further use by vacuum distillation of DMSO and water.     

Effect of uranium (VI) on two sulphate-reducing bacteria cultures from a uranium mine site

This work was conducted to assess the impact of uranium (VI) on sulphate-reducing bacteria (SRB) communities obtained from environmental samples collected on the Portuguese uranium mining area of Urgeiriça. Culture U was obtained from a sediment, while culture W was obtained from sludge from the wetland of that mine. Temperature gradient gel electrophoresis (TGGE) was used to monitor community changes under uranium stress conditions. TGGE profiles of dsrB gene fragment demonstrated that the initial cultures were composed of SRB species affiliated with Desulfovibrio desulfuricans, Desulfovibrio vulgaris and Desulfomicrobium spp. (sample U), and by species related to D. desulfuricans (sample W). A drastic change in SRB communities was observed as a result of uranium (VI) exposure. Surprisingly, SRB were not detected in the uranium removal communities. Such findings emphasize the need of monitoring the dominant populations during bio-removal studies. TGGE and phylogenetic analysis of the 16S rRNA gene fragment revealed that the uranium removal consortia are composed by strains affiliated to Clostridium genus, Caulobacteraceae and Rhodocyclaceae families. Therefore, these communities can be attractive candidates for environmental biotechnological applications associated to uranium removal.     

CL-5209萃淋树脂分离铀、二安替比林甲烷光度法测定八氧化三铀中微量钛

文章介绍了用CL-5209萃淋树脂分离铀、二安替比林甲烷光度法测定八氧化三铀中微量钛的方法研究。该法选择性高、形成的络合物稳定性好。方法的相对标准偏差为±3%,回收率为100～104%。在含0～20μg钛的范围内,服从朗伯-比耳定律。     

激光荧光法测定八氧化三铀中的痕量钐、铕、铽和镝

本文确定了钐、铕在噻吩甲酰三氟丙酮(TTA)和三辛基氧膦(TOPO)体系及铽、镝在钛铁试剂(Tiron)体系的最佳测定条件。对钐、铕、铽、镝的测定下限分别为20ppt、5ppt、5ppt及40ppt。同时采用P507萃淋树脂在4mol/L酸介质中达到大量铀与痕量稀土的定量分离,再利用不同酸度的盐酸-氯化钠混合溶液分别淋洗钐、铕、铽、镝、达到分离的目的。用该法进行了光谱纯八氧化三铀样品分析及加入回收,方法精密度为±10％,加入回收为95—105％     

测定水中微量铀的高灵敏显色体系的研究

本文介绍了一种用于测定水中微量铀的高灵敏显色体系。水样中加入菸酸、乙基紫和硫酸后,用混合溶剂环己烷+甲基异丁基甲酮(MIBK)(1:1)萃取,分光光度法测定。该方法的表观摩尔吸光系数为1.62×10~(-6)L·mol~(-1)·cm~(-1),回收率为97.8—106.0％,探测下限为2×10~(-9)g/mL,避免了使用有害的溶剂苯;Ca~(2+)、W~(6+)、Cu~(2+)和Hg~(2+)等离子对铀的测定干扰较严重。