Department of Chemistry, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal institute of Technology, SE-10044 Stockholm, Sweden.
Dalton Trans. 2021 May 18;50(19):6568-6577. doi: 10.1039/d1dt00436k.
Two uranyl peroxides meta-studtite and studtite exist in nature and can form as alteration phases on the surface of spent nuclear fuel upon water intrusion in a geological repository. Meta-studtite and studtite have very low solubility and could therefore reduce the reactivity of spent nuclear fuel toward radiolytic oxidants. This would inhibit the dissolution of the fuel matrix and thereby also the spreading of radionuclides. It is therefore important to investigate the stability of meta-studtite and studtite under conditions that may influence their stability. In the present work, we have studied the dissolution kinetics of meta-studtite in aqueous solution containing 10 mM HCO3-. In addition, the influence of the added H2O2 and the impact of γ-irradiation on the dissolution kinetics of meta-studtite were studied. The results are compared to previously published data for studtite studied under the same conditions. 13C NMR experiments were performed to identify the species present in aqueous solution (i.e., carbonate containing complexes). The speciation studies are compared to calculations based on published equilibrium constants. In addition to the dissolution experiments, experiments focussing on the stability of H2O2 in aqueous solutions containing UO22+ and HCO3- were conducted. The rationale for this is that H2O2 was consumed relatively fast in some of the dissolution experiments.
两种铀过氧化物钙铀云母和水硅钙铀矿存在于自然界中，在地质处置库中，水侵入后，它们可以作为乏核燃料表面的交代相形成。钙铀云母和水硅钙铀矿的溶解度非常低，因此可以降低乏核燃料对辐射分解氧化剂的反应性。这将抑制燃料基质的溶解，从而也限制了放射性核素的扩散。因此，研究钙铀云母和水硅钙铀矿在可能影响其稳定性的条件下的稳定性是很重要的。在本工作中，我们研究了在含有 10 mM HCO3-的水溶液中钙铀云母的溶解动力学。此外，还研究了添加的 H2O2 的影响以及γ辐照对钙铀云母溶解动力学的影响。结果与以前在相同条件下研究的水硅钙铀矿的数据进行了比较。进行了 13C NMR 实验以确定水溶液中存在的物种（即含有碳酸盐的配合物）。将形态研究与基于已发表平衡常数的计算进行了比较。除了溶解实验外，还进行了聚焦于含有 UO22+和 HCO3-的水溶液中 H2O2 稳定性的实验。这样做的理由是，在一些溶解实验中，H2O2 相对较快地被消耗。
