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Distribution of metallic fission-product particles in the cladding liner of spent nuclear fuel
npj Materials Degradation ( IF 5.1 ) Pub Date : 2020-01-30 , DOI: 10.1038/s41529-019-0107-0
Richard A. Clark , Michele A. Conroy , Timothy G. Lach , Edgar C. Buck , Kristi L. Pellegrini , Bruce K. McNamara , Jon M. Schwantes

We have made observations of noble metal phase fission-product agglomerates and gaseous xenon within the fuel-cladding interaction (FCI) zone of a high-burnup UO2 fuel. The FCI is the boundary between the UO2 pellet outer surface and the inner wall of the oxidized Zr-liner/cladding of the fuel rod. These fission-product agglomerates are well known to occur within the spent fuel matrix, and although radionuclides have been reported by others, we reveal aspects of their speciation and morphology. That they occur as discrete particles in the oxidized Zr liner, suggests the occurrence of hitherto unknown processes in the FCI zone during reactor operation, and this may have implications for the long-term storage and disposal of these types of materials. As expected, the particle agglomerates, which ranged in size from the nanometer scale to the micrometer scale, contained mainly Mo, Ru, Tc, Rh, and Pd; however, we also found significant quantities of Te associated with Pd. Indeed, we found nanometer scale separation of the distinct Pd/Te phase from the other fission products within the particles. Often associated with the particles was concentrations of uranium, sometimes appearing as a “cloud” with a tail emanating from the fuel into the oxidized cladding liner. Many of the noble metal phase particles appeared as fractured clusters separated by Xe-gas-filled voids. Possible mechanisms of formation or transport in the cladding liner are presented.



中文翻译:

金属裂变产物颗粒在乏核燃料包壳衬里的分布

我们已经观察到高燃烧UO 2燃料的燃料-包层相互作用(FCI)区域内的贵金属相裂变产物附聚物和气态氙。FCI是UO 2之间的边界颗粒的外表面和燃料棒氧化Zr内衬/覆层的内壁。众所周知,这些裂变产物附聚物会在乏燃料基质中发生,尽管其他人已经报告了放射性核素,但我们揭示了它们的形态和形态。它们以离散的颗粒形式出现在氧化的Zr衬里中,表明在反应堆运行期间FCI区域中发生了迄今未知的过程,这可能对这类材料的长期存储和处置产生影响。不出所料,颗粒团聚体的大小从纳米级到微米级不等,主要包含Mo,Ru,Tc,Rh和Pd;其中的Mo含量最高。但是,我们还发现了与Pd有关的大量Te。确实,我们发现颗粒中不同的Pd / Te相与其他裂变产物的纳米级分离。铀的浓度通常与颗粒有关,铀有时表现为“云”状,尾巴从燃料散发到氧化覆层衬里。许多贵金属相颗粒表现为被Xe气体填充的空隙分隔开的破裂簇。提出了包层衬里中可能形成或运输的机制。

更新日期:2020-01-30
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