Rajapaksha Harindu, Kruse Samantha J, LaVerne Jay A, Mason Sara E, Forbes Tori Z
Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, United States.
Department of Physics and Astronomy, University of Notre Dame, Notre Dame, Indiana 46556, United States.
Inorg Chem. 2025 May 19;64(19):9652-9661. doi: 10.1021/acs.inorgchem.5c00693. Epub 2025 May 7.
Nuclear materials, such as uranium-bearing solids, are exposed to high levels of ionizing radiation throughout the nuclear fuel cycle; thus, it is important to develop a molecular-level understanding of how these materials behave and degrade in the presence of gamma (γ) irradiation. In the current study, three U(VI) tetrachloride complexes, M[UOCl]·HO (where M = K, Rb, or Cs and = 0 or 2), and their respective chloride salts were exposed to 1-50 kGy of γ radiation using a Co source. Irradiated materials were evaluated by using electron paramagnetic resonance (EPR) and Raman spectroscopy and were further explored by using density functional theory (DFT) methods. EPR spectra of the irradiated materials suggest the formation of a Cl-based radical for both the alkali salts and the uranyl tetrachloride compounds, and DFT calculations provide evidence that the Cl radical is formed within these materials. The presence of water in the K and Rb compounds leads to additional spectroscopic signatures that could be traced back to water radiolysis and the formation of peroxide and superoxide species. DFT results support the formation of HO in the lattice and potentially the formation of a [UOCl(O)] species, highlighting the impact of water within the hydrated material to alter U(VI) speciation by radiolysis.
核材料，如含铀固体，在整个核燃料循环过程中都会受到高水平的电离辐射；因此，从分子层面了解这些材料在伽马（γ）辐射下的行为和降解方式非常重要。在本研究中，三种四氯化铀酰配合物M[UOCl]·H₂O（其中M = K、Rb或Cs且n = 0或2）及其各自的氯化物盐，使用钴源接受了1 - 50千戈瑞的γ辐射。通过电子顺磁共振（EPR）和拉曼光谱对辐照后的材料进行了评估，并使用密度泛函理论（DFT）方法进行了进一步探究。辐照材料的EPR光谱表明，碱金属盐和四氯化铀酰化合物都形成了基于氯的自由基，DFT计算提供了证据证明这些材料中形成了氯自由基。钾和铷化合物中存在水会导致额外的光谱特征，这些特征可追溯到水的辐射分解以及过氧化物和超氧化物物种的形成。DFT结果支持晶格中形成了·OH，并且可能形成了[UOCl(O)]物种，突出了水合材料中的水通过辐射分解改变铀酰（VI）形态的影响。
