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

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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.