Powellite ceramic represents a waste form matrix material to immobilize minor actinides and Mo from reprocessed UMo nuclear fuel. In this paper, the Ca1−xLix/2Gdx/2MoO4 (0 ≤ x ≤ 1) series is prepared by solid-state reaction using Gd3+ as trivalent minor actinide (Cm3+) surrogate, and the structure/microstructure is characterized by XRD, HRTEM, Raman spectroscopy and SEM. Rietveld refinements show that the couple (Gd3+ and Li+) enters into the eightfold coordinated Ca site of the powellite structure. With the increase in the contents of Gd and Li, Raman bands broaden due to the distortion of MoO4 tetrahedra and disordered arrangements of Gd3+ and Li+. The chemical durability analyzed by the PCT-B indicates that the leaching behaviors of Gd and Mo are related to the interfacial dissolution–reprecipitation mechanism. For the Ca0.5Li0.25Gd0.25MoO4 ceramic, 7-day NLGd and NLMo are shown in the order of ~ 10−4 and ~ 10−4 g m−2, respectively. Thus, our initial results of the structure and chemical durability will provide insights to design new single- or multiphase waste forms for the Mo-rich HLW conditioning.

中文翻译：

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用于放射性废物储存的 Powellite 陶瓷 Ca1−xLix/2Gdx/2MoO4 (0 ≤ x ≤ 1) 的结构和化学耐久性研究

Powellite 陶瓷代表一种废物形式的基质材料，用于固定来自再加工 UMo 核燃料的次要锕系元素和 Mo。在本文中，Ca1−xLix/2Gdx/2MoO4 (0 ≤ x ≤ 1) 系列是以 Gd3+ 作为三价次锕系 (Cm3+) 替代物通过固相反应制备的，并通过 XRD、HRTEM、拉曼光谱和扫描电镜。Rietveld 改进表明，这对（Gd3+ 和 Li+）进入了 powellite 结构的八重配位 Ca 位点。随着Gd和Li含量的增加，由于MoO4四面体的畸变和Gd3+和Li+的无序排列，拉曼谱带变宽。PCT-B 分析的化学耐久性表明 Gd 和 Mo 的浸出行为与界面溶解-再沉淀机制有关。对于 Ca0.5Li0.25Gd0。25MoO4 陶瓷、7 天 NLGd 和 NLMo 分别以~10-4 和~10-4 gm-2 的顺序显示。因此，我们对结构和化学耐久性的初步结果将为设计用于富钼 HLW 调节的新单相或多相废物形式提供见解。