Abstract Powellite ceramic represent one candidate to immobilize minor actinides and Mo from reprocessed UMo nuclear fuel. In this work, the Ca1-xLix/2Cex/2MoO4 (0 ≤ x ≤ 1) series is prepared via a solid-state reaction using Ce3+ as trivalent minor actinide (Am3+) surrogate, with structure/microstructure characterized by XRD, XPS, HRTEM, and SEM as well. The Ca1-xLix/2Cex/2MoO4 (0 ≤ x ≤ 1) compositions crystallize in tetragonal and are isostructural with scheelite. Rietveld refinements show that Ce3+ and Li+ simultaneously enter into the eight-fold coordinated Ca site of powellite crystal. The chemical durability of powellite phases is evaluated by the ASTM C1285-14 product consistency test method B. The leaching behaviours of Ce and Mo are accordance with the interfacial dissolution-reprecipitation mechanism. For all the Ca1-xLix/2Cex/2MoO4 (0 ≤ x ≤ 1) ceramics, 7-days NLCe and NLMo are found to be in the order of 10−3-10−5 g·m−2 and 10−2-10−4 g·m−2 respectively, which exhibit the great retention of Ce and Mo. Interestingly, the values of 7-days NLCe and NLMo are predominantly controlled by the distortion of MoO4 tetrahedra and disordered arrangements of Ce3+ and Li+. Thus, our initial understanding on the structure and chemical durability relation will provide insight to design new waste forms for the Mo-rich HLW condition.

中文翻译：

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富钼 HLW 条件下 Powellite 陶瓷 Ca1-xLix/2Cex/2MoO4 (0 ≤ x ≤ 1) 的制备和表征

摘要 Powellite 陶瓷是从再加工 UMo 核燃料中固定次锕系元素和 Mo 的一种候选材料。在这项工作中，Ca1-xLix/2Cex/2MoO4 (0 ≤ x ≤ 1) 系列是通过使用 Ce3+ 作为三价次锕系元素 (Am3+) 替代物的固态反应制备的，其结构/微观结构由 XRD、XPS、HRTEM 表征，以及 SEM。Ca1-xLix/2Cex/2MoO4 (0 ≤ x ≤ 1) 组合物在四方晶系中结晶并且与白钨矿同构。Rietveld 精修表明 Ce3+ 和 Li+ 同时进入 Powellite 晶体的八重配位 Ca 位点。Powellite 相的化学耐久性通过ASTM C1285-14 产品一致性测试方法B 进行评估。Ce 和Mo 的浸出行为符合界面溶解-再沉淀机制。对于所有 Ca1-xLix/2Cex/2MoO4 (0 ≤ x ≤ 1) 陶瓷，发现 7 天 NLCe 和 NLMo 的数量级为 10-3-10-5 g·m-2 和 10-2-分别为 10-4 g·m-2，表现出对 Ce 和 Mo 的大量保留。有趣的是，7 天 NLCe 和 NLMo 的值主要受 MoO4 四面体的畸变和 Ce3+ 和 Li+ 的无序排列控制。因此，我们对结构和化学耐久性关系的初步了解将为为富钼 HLW 条件设计新的废物形式提供见解。