Combined peridynamics and finite element crystal plasticity modelling of the oxidation of zirconium alloys

该项目涉及在微观尺度上对核燃料包壳上不断增长的氧化锋进行建模。这是一个复杂的多物理过程，涉及离子在温度和应力梯度下的扩散，以及脆性氧化相中裂纹形成的机制。裂缝的形成既可以增加（通过垂直裂缝）也可以阻碍（通过横向裂缝）氧和水分子进入金属-氧化物界面。最重要的是，随着氧化物变厚，裂缝减轻了压力。对氧化过程的机理理解是该项目的目的。这将反过来为氧化物生长行为的更高尺度模型提供信息，从而最终确定包层，从而确定燃料寿命。提高燃料寿命既提高了电厂运行的经济性，又减少了废物负担。为此，我们将使用两种最终将耦合在一起的技术：(1)周动力学，这是一种非局部伪无网格方法，可以模拟氧化相的脆性开裂；(2)由于这是一种微尺度现象，我们将使用有限元晶体塑性模型来模拟潜在的锆金属。这些方法结合在一起，将给出在这种规模下燃料包壳氧化过程的最完整模型。

This project involves modelling the growing oxidation front on nuclear fuel cladding at the microscale. This is a complex multi-physics process involving diffusion of ionic species under temperature and stress gradients coupled to the mechanics of crack formation in the brittle oxide phase. Crack formation can both increase (through vertical cracking) or hinder (through lateral cracking) the oxygen and water molecule ingress to the metal-oxide interface. On top of this the cracking relieves the stresses that build up as the oxide thickens. Mechanistic understanding of the oxidation process is the aim of the project. This will in turn inform higher scale models of the oxide growth behaviour, which can ultimately determine the cladding and hence fuel life. Improving fuel life improves both the economics of plant operation and reduces the waste burden. To do this we will use two techniques that will ultimately be coupled together: (1) peridynamics, which is a non-local pseudo-meshless method that can model brittle cracking in the oxide phase, and (2) because this is a microscale phenomenon we will use finite element crystal plasticity modelling for the underlying zirconium metal. Together these methods will give the most complete model yet of the oxidation process of fuel cladding at this scale.