Liu Xiang-Yang, Uberuaga Blas P, Sickafus Kurt E
Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
J Phys Condens Matter. 2009 Jan 28;21(4):045403. doi: 10.1088/0953-8984/21/4/045403. Epub 2009 Jan 8.
In order to close the nuclear fuel cycle, advanced concepts for separating out fission products are necessary. One approach is to use a dispersion fuel form in which a fissile core is surrounded by an inert matrix that captures and immobilizes the fission products from the core. If this inert matrix can be easily separated from the fuel, via e.g. solution chemistry, the fission products can be separated from the fissile material. We examine a surrogate dispersion fuel composition, in which hafnia (HfO(2)) is a surrogate for the fissile core and alkaline earth metal oxides are used as the inert matrix. The questions of fission product incorporation in these oxides and possible segregation behavior at interfaces are considered. Density functional theory based calculations for fission product elements (Xe, Sr, and Cs) in these oxides are carried out. We find smaller incorporation energy in hafnia than in MgO for Cs and Sr, and Xe if variation of charge state is allowed. We also find that this trend is reversed or reduced for alkaline earth metal oxides with large cation sizes. Model interfacial calculations show a strong tendency of segregation from bulk MgO to MgO-HfO(2) interfaces.
为了实现核燃料循环闭合，需要先进的裂变产物分离概念。一种方法是使用弥散燃料形式，其中易裂变核心被惰性基体包围，该基体捕获并固定来自核心的裂变产物。如果这种惰性基体能够通过例如溶液化学方法轻松地与燃料分离，那么裂变产物就可以从易裂变材料中分离出来。我们研究了一种替代弥散燃料成分，其中氧化铪（HfO₂）作为易裂变核心的替代物，碱土金属氧化物用作惰性基体。考虑了裂变产物在这些氧化物中的掺入问题以及在界面处可能的偏析行为。对这些氧化物中的裂变产物元素（Xe、Sr和Cs）进行了基于密度泛函理论的计算。我们发现，如果允许电荷态变化，对于Cs和Sr以及Xe，氧化铪中的掺入能比氧化镁中的小。我们还发现，对于具有大阳离子尺寸的碱土金属氧化物，这种趋势会反转或减弱。模型界面计算表明，从块状氧化镁到MgO-HfO₂界面有很强的偏析倾向。
