Pidchenko Ivan, Bauters Stephen, Sinenko Irina, Hempel Simone, Amidani Lucia, Detollenaere Dirk, Vinze Laszlo, Banerjee Dipanjan, van Silfhout Roelof, Kalmykov Stepan N, Göttlicher Jörg, Baker Robert J, Kvashnina Kristina O
The Rossendorf Beamline at ESRF - The European Synchrotron CS40220 38043 Grenoble Cedex 9 France
Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Resource Ecology PO Box 510119 01314 Dresden Germany.
RSC Adv. 2020 Jul 6;10(43):25529-25539. doi: 10.1039/d0ra03375h. eCollection 2020 Jul 3.
Herein, a multi-technique study was performed to reveal the elemental speciation and microphase composition in altered granitic rock collected from the Krunkelbach Valley uranium (U) deposit area near an abandoned U mine, Black Forest, Southern Germany. The former Krunkelbach U mine with 1-2 km surrounding area represents a unique natural analogue site with the rich accumulation of secondary U minerals suitable for radionuclide migration studies from a spent nuclear fuel (SNF) repository. Based on a micro-technique analysis using several synchrotron-based techniques such as X-ray fluorescence analysis, X-ray absorption spectroscopy, powder X-ray diffraction and laboratory-based scanning electron microscopy and Raman spectroscopy, the complex mineral assemblage was identified. While on the surface of granite, heavily altered metazeunerite-metatorbernite (Cu(UO)(AsO) (PO) ·8HO) microcrystals were found together with diluted coatings similar to cuprosklodowskite (Cu(UO)(SiOOH)·6HO), in the cavities of the rock predominantly well-preserved microcrystals close to metatorbernite (Cu(UO)(PO)·8HO) were identified. The Cu(UO)(AsO) (PO) ·8HO species exhibit uneven morphology and varies in its elemental composition, depending on the microcrystal part ranging from well-preserved to heavily altered on a scale of ∼200 μm. The microcrystal phase alteration could be presumably attributed to the microcrystal morphology, variations in chemical composition, and geochemical conditions at the site. The occurrence of uranyl-arsenate-phosphate and uranyl-silicate mineralisation on the surface of the same rock indicates the signatures of different geochemical conditions that took place after the oxidative weathering of the primary U- and arsenic (As)-bearing ores. The relevance of uranyl minerals to SNF storage and the potential role of uranyl-arsenate mineral species in the mobilization of U and As into the environment is discussed.
在此，开展了一项多技术研究，以揭示从德国南部黑森林一座废弃铀矿附近的克伦克尔巴赫山谷铀（U）矿床采集的蚀变花岗岩中的元素形态和微相组成。以前的克伦克尔巴赫铀矿及其周边1 - 2公里区域是一个独特的天然模拟场地，富含次生铀矿物，适合用于研究乏核燃料（SNF）储存库中放射性核素的迁移。基于使用多种基于同步加速器的技术（如X射线荧光分析、X射线吸收光谱、粉末X射线衍射）以及基于实验室的扫描电子显微镜和拉曼光谱进行的微观技术分析，确定了复杂的矿物组合。在花岗岩表面，发现了严重蚀变的变水铀矿 - 变铜铀云母（Cu(UO₂)(AsO₄)(PO₄)₂·8H₂O）微晶，以及类似于铜硅钙铀矿（Cu(UO₂)(SiO₄OH)₂·6H₂O）的稀释涂层；在岩石的空洞中，主要识别出了接近变铜铀云母（Cu(UO₂)(PO₄)₂·8H₂O）的保存完好的微晶。Cu(UO₂)(AsO₄)(PO₄)₂·8H₂O物种呈现出不均匀的形态，其元素组成也有所不同，这取决于微晶部分，在约200μm的尺度上，从保存完好到严重蚀变。微晶相的蚀变可能归因于微晶形态、化学成分的变化以及该场地的地球化学条件。同一岩石表面出现铀酰砷酸盐 - 磷酸盐和铀酰硅酸盐矿化，表明了原生含铀和砷（As）矿石氧化风化后发生的不同地球化学条件的特征。讨论了铀酰矿物与SNF储存的相关性以及铀酰砷酸盐矿物物种在将U和As迁移到环境中的潜在作用。
