铀钼金属型核燃料因为其高铀含量和高热导率等优点，被认为是一种有潜力的新型核燃料，其辐照肿胀行为尚需进行深入研究。为此，本论文构建了一个新的U–Mo势函数，通过分子动力学方法研究了γ-U–Mo固溶体合金中的初级辐照损伤行为，并进一步探讨了裂变产物Xe对辐照损伤的影响。同时本论文还研究了Al镀层对U腐蚀防护的机制，探讨了初级辐照损伤对U–Al界面结构的影响。基于本课题组提出的新型角度相关多体势形式，本论文构建了一个新的U–Mo势函数，该势函数可以较好地还原U–Mo系统主要物相的宏观性质。此外，我们对该势函数和文献中的U–Mo–Xe三元势函数在原子短近程作用范围内进行了修正，得到了与第一性原理计算高度吻合的结果。这些势函数的开发和修正，为开展更加准确的U–Mo合金辐照损伤模拟奠定了工作基础。采用本论文新开发的角度相关势函数，我们研究了γ-U–Mo固溶体合金中的辐照损伤行为，并发现在大于5 wt.%Mo的成分范围内Mo含量的降低会提高辐照损伤剩余缺陷的数量，这可能会加速缺陷结构的演化进程，并在一定程度上解释了实验上观察到的Mo贫化区不利于控制U–Mo核燃料加速辐照肿胀行为这一现象。采用短近程修正后的U–Mo–Xe三元势，我们进一步研究了裂变气体Xe在γ-U–Mo固溶体初级辐照损伤过程中的影响，模拟结果显示裂变气体Xe的积累会显著提高剩余缺陷的数量，留下大量的高压Xe气团。同时本论文还发现，提高Mo含量可以有效降低高裂变气体含量条件下的辐照损伤剩余缺陷数量，并抑制Xe在级联碰撞过程中的扩散行为，这进一步说明了适当提高Mo的含量有助于控制U–Mo核燃料的辐照肿胀行为。本论文采用第一性原理计算方法对U–Al界面上腐蚀元素H和O的分布规律做出了一些探讨，H和O在界面附近截然相反的聚集倾向表明Al镀层可能对氧腐蚀会有更好的防护效果。本论文还发现U–Al界面对于U晶相内的空位缺陷表现出明显的吸附作用，而这些界面上的空位同时又会对H和O间隙子表现出强烈的吸纳效果，这说明U基体内部初级辐照损伤所产生的空位缺陷可能会在U–Al界面上不断集中，并引发腐蚀元素H和O在界面上的聚集。同时U–Al界面附近的初级辐照损伤模拟研究结果显示，U–Al界面会让级联碰撞过程产生更多的辐照剩余缺陷，并在界面附近留下空洞，不利于界面的稳定结合。
U–Mo alloy is a promising nuclear fuel due to high values of uranium density and thermal conductivity. In efforts to explore underlying mechanism and improve prediction of irradiation swelling behavior in U–Mo fuel, this work constructed a new angular dependent U–Mo potential and studied the primary irradiation damage in U–Mo system. The implication of Xe for the primary irradiation damage has been further discussed. Besides, the distribution of corrosion elements including H and O near U–Al interface and potential influence of primary irradiation damage on the interface have also been investigated.The study has applied a new angular dependent formalism proposed by the author’s group by fitting to macroscopic properties of reference structures in U–Mo system, which obtained moderately well reproduction. Moreover, the newly constructed potential, together with a reported U–Mo–Xe ternary potential, have been further improved at intermediate and short atomic distance benchmarked with the threshold displacement energy surface calculated under the density functional theory framework (DFT). The construction and modification of the interatomic potentials paved the way for more accurate molecular dynamics (MD) simulations of energetic particles in U–Mo system.Primary irradiation damage in U–Mo solid solutions has been simulated with the new angular dependent potential. Within composition range over 5 wt.%Mo, the decrease of Mo content brings about an uplift in the residual defect population, which lends support to the harmful role of local Mo depletion in mitigation of irradiation swelling. Meanwhile, simulations of U–Mo–Xe system with the corrected ternary potential have found that the increase of Xe content could promote the number of residual defects remarkably, leaving over-pressurized Xe bubbles in cascade region. It could be further inferred that the accumulation of the fission gas accelerates the generation and evolution of defect structures under irradiation environment. Meanwhile, high content of Mo has been revealed to reduce considerably the production of residual defect and hinder the irradiation induced diffusion of Xe at high density of the fission gas, which further confirms the detrimental potential of local Mo depletion observed in in-pile U–Mo fuels.The distribution of H and O impurities near the U–Al interface have been investigated by DFT. The stark contrast between the residence preference of H and O near the interface structure suggests a more robust role of Al coating against oxidation. Meanwhile, the U–Al interface appears to be a significant adsorption position for vacancies from U lattice and a U vacancy at the interface has been demonstrated to be a strong sink for H and O impurities, suggesting trends of segregation to the U–Al interface of vacancies produced by primary irradiation damage in U bulk and consequent accumulation of corrosion elements. In MD simulations of displacement cascades near the U–Al interface, it has been observed that cascade processes intersected with the interface produces more residual defects than those far from the interface, where voids on the interface have been found. It could be further deduced that the interface structure plays a harmful role in terms of cascade damage.
