西北某铀矿山强化地浸实践

西北某铀矿山采用酸法地浸对其低渗透性砂岩铀矿床进行开采,但其7#、8#采区投产后浸出效率低。为了提高浸出效率,对采区已有生产数据进行了分析,在两采区开展了“洗孔”、“采区浸出环境优化”、“加压下注”等强化浸出方法的现场实践,结果表明:洗孔后普遍钻孔生产能力恢复;“采区浸出环境优化”后8#采区浸出液量及铀浓度明显增长,产能增加;“加压下注”后8#采区注液量涨幅达25.7%,液固比增长稳定,与采区浸采时间呈线性关系。     

铀尾矿砂基质吸力对铀尾矿坝力学性能影响试验探究

通过对某铀尾矿库坝体材料现场取样和室内土工试验,进行应变直剪试验,得到铀尾矿砂不同含水率下最大剪应力的实验数据。结果表明:随着含水率的增大,非饱和铀尾矿砂的基质吸力在逐渐减小,黏聚力与内摩擦角随含水率的增大呈先增大后变小的变化规律。根据基质吸力对铀尾矿库坝体剪应力的变化规律,随着基质吸力的逐渐减小,剪应力先增大后减小。     

The Effect of Guest Metal Ions on the Reduction Potentials of Uranium(VI) Complexes: Experimental and Theoretical Investigations

Two mononuclear uranyl complexes, [UO₂L¹] ( 1 ) and [UO₂L²] ⋅ 0.5 CH₃CN ⋅ 0.25 CH₃OH ( 2 ), have been synthesized from two multidentate N₃O₄ donor ligands, N,N′-bis(5-methoxysalicylidene)diethylenetriamine (H₂L¹) and N,N′-bis(3-methoxysalicylidene)diethylenetriamine (H₂L²), respectively, and have been structurally characterized. Both complexes 1 and 2 showed a reversible U^VI/U^V couple at −1.571 and −1.519 V, respectively, in cyclic voltammetry. The reduction potential of the U^VI/U^V couple shifted towards more positive potential on addition of Li⁺, Na⁺, K⁺, and Ag⁺ metal ions to acetonitrile solutions of complex 2 , and the resulting potential was correlated with the Lewis acidity of the metal ions and was also justified by theoretical DFT calculations. No such shift in reduction potential was observed for complex 1 . All four bimetallic products, [UO₂L²Li_0.5](ClO₄)_0.5 ( 3 ), [UO₂L²Na(ClO₄)]₂ ( 4 ), [UO₂L²Ag(NO₃)(H₂O)] ( 5 ), and [(UO₂L²)₂K(H₂O)₂]PF₆ ( 6 ), formed on addition of the Li⁺, Na⁺, Ag⁺, and K⁺ metal ions, respectively, to acetonitrile solutions of complex 2 , were isolated in the solid state and structurally characterized by single-crystal X-ray diffraction. In all the species, the inner N₃O₂ donor set of the ligand encompasses the equatorial plane of the uranyl ion and the outer open compartment with O₂O′₂ donor sites hosts the second metal ion.     

Visible-Light-Enabled C−H Functionalization by a Direct Hydrogen Atom Transfer Uranyl Photocatalyst

The development of the uranyl cation as a powerful photocatalyst is seriously delayed in comparison with the advances in its fundamental and structural chemistry. However, its characteristic high oxidative capability in the excited state ([UO₂]²⁺* (+2.6 V vs. SHE; SHE=standard hydrogen electrode) combined with blue-light absorption (hv=380 – 500 nm) and a long-lived fluorescence lifetime up to microseconds have reveals that the uranyl cation approaches an ideal photocatalyst for visible-light-driven organic transformations. Described herein is the successful use of uranyl nitrate as a photocatalyst to enable C(sp³)−H activation and C−C bond formation through hydrogen atom transfer (HAT) under blue-light irradiation. In particular, this operationally simple strategy provides an appropriate approach to the synthesis of diverse and valuable diarylmethane motifs. Mechanistic studies and DFT calculations have provided insights into the detailed mechanism of the photoinduced HAT pathway. This research suggests a general platform that could popularize promising uranyl photocatalytic performance.     

Synthesis and Structure of Uranium-Silylene Complexes

While carbene complexes of uranium have been known for over a decade, there are no reported examples of complexes between an actinide and a „heavy carbene.“ Herein, we report the syntheses and structures of the first uranium-heavy tetrylene complexes: (CpSiMe₃)₃U-Si[PhC(NR)₂]R’ (R=tBu, R’=NMe₂ 1 ; R=iPr, R’=PhC(NiPr)₂ 2 ). Complex 1 features a kinetically robust uranium-silicon bonding interaction, while the uranium-silicon bond in 2 is easily disrupted thermally or by competing ligands in solution. Calculations reveal polarized σ bonds, but depending on the substituents at silicon a substantial π-bonding interaction is also present. The complexes possess relatively high bond orders which suggests primarily covalent bonding between uranium and silicon. These results comprise a new frontier in actinide-heavy main-group bonding.     

基于生态安全理念的我国铀矿冶业可持续发展

生态安全是矿业可持续发展的重要问题．铀矿冶工业是核工业和核电事业发展的基础,但是铀矿采冶对生态环境的影响也是较大的,主要包括尾矿与废石、废水、辐射影响等．本文通过分析生态安全与可持续发展的辩证关系,结合从生态安全角度对我国铀矿冶工业受制约因素的分析,就如何充分发挥生态安全理念对我国铀矿冶工业可持续发展的作用进行深入探讨．我国铀矿冶工业要实现可持续发展,必须从以下四个方面建立生态安全理念：树立生态安全管理观;树立科学生态安全观;树立生态安全投入观;树立生态安全责任观．     

Surface reactivity of uranium hexafluoride (UF6)

The present article reviews a selection of results obtained in the AREVA/CNRS/UCA joint research laboratory. It focuses on interfaces formed by uranium hexafluoride (UF₆) with chemical filter (purification), carbon (UF₆ storage), and metallic substrate (corrosion). As a matter of fact, along the nuclear fuel cycle, metallic surfaces of the fluorination reactors, cooling systems (for the liquefaction of UF₆), and storage containers are in contact with UF₆, either in the gas or in the liquid phase. For the removal of volatile impurities before the enrichment, surface of chemical filters with a high specific surface area must be enhanced for both selectivity and efficiency. To store depleted UF₆ (²³⁸U), graphite intercalation compounds are proposed and preliminary results are presented.     

含铀凋落物腐解前后微生物群落结构特征及多样性分析

采集含铀凋落物腐解前后土壤样本,通过Illumina Miseq高通量测序技术研究腐解前后土壤微生物的多样性及群落结构,解析含铀凋落物腐解前后土壤微生物群落结构特征及其变化规律,为发掘潜在含铀生物质降解菌种提供理论基础。通过高通量测序,分别获得158 781条细菌和242 198条真菌的有效序列,菌群Alpha分析显示,腐解后细菌的多样性和丰富度增加,真菌的多样性和丰富度减少。通过微生物群落结构解析,发现腐解前后门水平上始终存在的优势菌群,细菌中为绿弯菌门(Chloroflexi)、放线菌门(Actinobacteria)、酸杆菌门(Acidobacteria)和变形菌门(Proteobacteria);真菌中为子囊菌门(Ascomycota)、担子菌门(Basidiomycota)、unclassified_Fungi和被孢囊门(Mortierellomycota)。结果表明,含铀凋落物腐解后,凋落物内的铀被释放到土壤中,改变了土壤微生物群落结构。腐解后土壤中可识别的优势菌群功能主要集中在对纤维素、半纤维素、木质素的降解和铀的浸出。热酸菌属(Acidothermus)和软盘菌属(Mollisia)可能是降解凋落物和浸出铀较好的微生物组合。     

基于分形理论的土壤氡浓度矿化异常的分析方法:以湖南郴州金狮岭地区为例

土壤氡浓度分布具有双分形特征,其分维值分别为D1=0.079 4和D2=1.4654,分形临界值为2 167.7 Bq/m~3.低于临界值的分形其分维值D1很小,代表了区域背景分布,其背景值为1 088.16 Bq/m~3.高于临界值的分形其分维值D2显著增大,反映该区发生了较强的成矿作用的叠加.分形临界值可以作为异常下限值.金狮岭地区土壤氡浓度异常区分布范围较大,表明具有较好的成矿远景.