Abstract：
Silicon carbide (SiC) is a promising structural and cladding material for accident tolerant fuel cladding of nuclear reactor due to its excellent properties. However, when exposed to severe environments (e.g., during neutron irradiation), lattice defects are created in amounts significantly greater than normal concentrations. Then, a series of radiation damage behaviors (e.g., radiation swelling) appear. Accurate understanding of radiation damage of nuclear materials is the key to the design of new fuel cladding materials. Multi-scale computational simulations are often required to understand the physical mechanism of radiation damage. In this work, the effect of neutron irradiation on the volume swelling of cubic-SiC film with 0.3 mm was studied by using the combination of molecular dynamics (MD) and rate theory (RT). It was found that for C-vacancy (CV), C-interstitial (CI), Si-vacancy (SiV), Si-interstitial (SiI), and Si-antisite (SiC), the volume of supercell increases linearly with the increase of concentration of these defects, while the volume of supercell decreases linearly with the increase of defect concentration for C-antisite (CSi). Furthermore, according to the neutron spectrum of a certain reactor, one RT model was constructed to simulate the evolution of point defect under neutron irradiation. Then, the relationship between the volume swelling and the dose of neutrons can be obtained through the results of MD and RT. It was found that swelling typically increases logarithmically with radiation dose and saturates at relatively low doses, and that the critical dose for abrupt transition of volume is consistent with the available experimental data, which indicates that the rate theory model can effectively describe the radiation damage evolution process of SiC. This work not only presents a systematic study on the relationship between various point defect and excess volume, but also gives a good example of multi-scale modelling through coupling the results of binary collision, MD and RT methods, etc., regardless of the multi-scale modelling only focus on the evolution of primary point defects.
摘要：
碳化硅(SiC)具有优异的性能,是一种具有良好应用前景的核反应堆耐事故燃料包壳材料。然而,当暴露于恶劣环境时(例如，在中子辐照期间)，晶格缺陷的产生量显著大于正常浓度。然后，一系列的辐射损伤行为(例如，辐射肿胀)出现。准确理解核材料的辐射损伤是设计新型燃料包壳材料的关键。通常需要多尺度计算模拟来了解辐射损伤的物理机制。在这项工作中,结合分子动力学（MD）和速率理论（RT）研究了中子辐照对0.3mm立方SiC薄膜体积溶胀的影响。发现对于C空缺(CV)，C-间质（CI），Si-空位(SiV),Si-间隙(SiI),和Si-反位（SiC），超晶胞的体积随着这些缺陷浓度的增加而线性增加，而超细胞的体积随着C反位点（CSi）缺陷浓度的增加而线性减小。此外，根据某反应堆的中子能谱,建立了一个RT模型来模拟中子辐照下点缺陷的演化。然后，通过MD和RT的结果可以获得体积膨胀与中子剂量之间的关系。发现肿胀通常随着辐射剂量的对数增加，并且在相对较低的剂量下饱和。体积突变的临界剂量与现有的实验数据一致，表明速率理论模型能够有效地描述SiC的辐射损伤演化过程。这项工作不仅对各种点缺陷与过量体积之间的关系进行了系统的研究，而且还通过耦合二元碰撞的结果给出了多尺度建模的一个很好的例子，MD和RT方法，等。,不管多尺度建模只关注初级点缺陷的演化。
