A hybrid simulation methodology for modeling dynamic recrystallization in UO2 LWR nuclear fuels

High burn-up, rim structures within uranium dioxide (UO2) light water reactor fuels exhibit marked differences in microstructure that are attributed to dynamic recrystallization. The recrystallization process has three distinct, interacting components: damage accumulation, nucleation and growth of damage-free regions, and subsequent evolution of recrystallized grains. In this paper, microstructural-scale simulation techniques for all three processes are presented and assembled into a hybrid tool for modeling the entire dynamic recrystallization process. The components of the model include a phenomenological model for damage accumulation and nucleation, a Cellular Automaton (CA) model for the growth and impingement of recrystallized grains, and a kinetic Monte Carlo (kMC) Potts model for subsequent grain growth. Preliminary results of the hybrid model demonstrate the evolution of a steady state grain size. Parametric simulations show the dependence of the steady state grain size on physical variables and on system size.