Popel Aleksej J, Spurgeon Steven R, Matthews Bethany, Olszta Matthew J, Tan Beng Thye, Gouder Thomas, Eloirdi Rachel, Buck Edgar C, Farnan Ian
Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, United Kingdom.
Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States.
ACS Appl Mater Interfaces. 2020 Sep 2;12(35):39781-39786. doi: 10.1021/acsami.0c09611. Epub 2020 Aug 18.
Our present understanding of surface dissolution of nuclear fuels such as uranium dioxide (UO) is limited by the use of nonlocal characterization techniques. Here we discuss the use of state-of-the-art scanning transmission electron microscopy (STEM) to reveal atomic-scale changes occurring to a UO thin film subjected to anoxic dissolution in deionized water. No amorphization of the UO film surface during dissolution is observed, and dissolution occurs preferentially at surface reactive sites that present as surface pits which increase in size as the dissolution proceeds. Using a combination of STEM imaging modes, energy-dispersive X-ray spectroscopy (STEM-EDS), and electron energy loss spectroscopy (STEM-EELS), we investigate structural defects and oxygen passivation of the surface that originates from the filling of the octahedral interstitial site in the center of the unit cells and its associated lattice contraction. Taken together, our results reveal complex pathways for both the dissolution and infiltration of solutions into UO surfaces.
我们目前对二氧化铀（UO₂）等核燃料表面溶解的理解受到非局部表征技术应用的限制。在此，我们讨论使用最先进的扫描透射电子显微镜（STEM）来揭示在去离子水中进行缺氧溶解的UO₂薄膜所发生的原子尺度变化。在溶解过程中未观察到UO₂薄膜表面的非晶化现象，溶解优先发生在作为表面凹坑呈现的表面反应位点，随着溶解的进行，这些凹坑尺寸增大。通过结合STEM成像模式（STEM成像模式）、能量色散X射线光谱（STEM - EDS）和电子能量损失光谱（STEM - EELS），我们研究了源于晶胞中心八面体间隙位置填充及其相关晶格收缩的表面结构缺陷和氧钝化。综合来看，我们的结果揭示了溶液在UO₂表面溶解和渗透的复杂途径。
