Development of a model for irradiation-assisted grain growth for nanocrystalline UO₂

In this work, we have developed a model for irradiation-assisted grain growth in nanocrystalline UO₂ using the MARMOT code. We include the impact of irradiation on UO₂ grain growth by coupling a phase field grain growth model with a heat conduction simulation that features a random heat source representing thermal spikes. Our model parameters have been calibrated against experimental measurements at 300 K. The calibrated model predicts grain growth in an irradiated UO₂ thin film that compares well with experimental data at 50 K. These results suggest that thermal spikes are the major cause of the irradiation-assisted grain growth observed in the UO₂ experiments. They also indicate that irradiation-assisted grain growth is only significant with average grain sizes less than 35 nm, and thus can be neglected when considering fuel performance of typical UO₂ fuel pellets.