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Molecular dynamics investigation of xenon, uranium, and oxygen diffusion in UO2 nuclear fuel
Computational Materials Science ( IF 3.1 ) Pub Date : 2022-05-29 , DOI: 10.1016/j.commatsci.2022.111553
Seyed Mehrdad Zamzamian , Ahmadreza Zolfaghari , Zahra Kowsar

In this paper, atomistic simulations based on molecular dynamics (MD) are used to calculate the diffusion coefficients of xenon, uranium and oxygen in uranium dioxide containing different percentages of xenon atoms replaced by uranium from 2%Xe to 10%Xe at ten temperatures between 300 and 2500 K (covering three temperature regimes of athermal, intermediate and intrinsic). Since we did not take the irradiation conditions into account in the simulations, the calculated diffusion coefficients are “out-of-pile”. Initially, the validity of the interatomic potential was performed by calculating the formation energies of interstitial, vacancy, Frankel and Schottky defects by using molecular statics (MS) simulations. Then, the migration energies of Xe/U/O based on considering various mechanisms were obtained by employing the Nudge Elastic Band (NEB) method. The results were generally in good agreement with those reported in the literature and the potential was validated. The simulations of UO2 containing different percentages of xenon (percentage of replacement of uranium atoms with xenon atoms) from 2 to 10 showed that with increasing the xenon percentage, the number of xenon clusters, cluster size, and radius of gyration considerably increases, and bubble nucleation was considerable in the case of 10%Xe. Then, by determining the slope of the mean square displacements, diffusion coefficients of xenon, uranium and oxygen were obtained. The results showed that they are both temperature-dependent and also dependent on the percentage of xenon (which was previously assumed to be independent of concentration). In the end, three temperature and xenon percentage dependent equations were proposed for the diffusion coefficients of xenon, uranium and oxygen. Finally, by applying a reduction factor (constant) to the diffusion coefficients, they were compared with experimental data available in the literature and significant satisfaction was obtained.



中文翻译:

UO2 核燃料中氙、铀和氧扩散的分子动力学研究

在本文中,基于分子动力学(MD)的原子模拟用于计算氙、铀和氧在含有不同百分比的氙原子被铀取代的二氧化铀中,从 2%Xe 到 10%Xe,在 10 个温度范围内的扩散系数。 300 和 2500 K(涵盖无热、中间和本征三个温度范围)。由于我们在模拟中没有考虑辐照条件,因此计算出的扩散系数是“堆外的”。最初,通过使用分子静力学 (MS) 模拟计算间隙、空位、弗兰克尔和肖特基缺陷的形成能来执行原子间势的有效性。然后,采用 Nudge Elastic Band (NEB) 方法获得了基于各种机制的 Xe/U/O 迁移能。结果与文献报道的结果大体一致,潜力得到了验证。UO的模拟2含有不同百分比的氙(铀原子被氙原子取代的百分比)从 2 到 10 表明,随着氙百分比的增加,氙团簇的数量、团簇大小和回转半径显着增加,气泡成核明显10%Xe 的情况。然后,通过确定均方位移的斜率,得到氙、铀和氧气的扩散系数。结果表明,它们既依赖于温度,也依赖于氙气的百分比(以前假设与浓度无关)。最后,针对氙、铀和氧气的扩散系数,提出了三个温度和氙百分比相关的方程。最后,通过对扩散系数应用缩减因子(常数),

更新日期:2022-05-30
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