Monte Carlo simulation of intragranular Xe bubble re-solution in UZr nuclear fuels

The bubble re-solution in UZr alloys plays a key role in the nucleation and growth of fission gas bubble, but its mechanism is still unclear. In this work, the behavior of Xe bubble re-solution due to binary collision affected by bubble radius, matrix composition, and fission fragments in UZr fuels has been carried out by 3D Monte Carlo method. The re-solution coefficient (b₀) decreases with the increase of bubble radius (R_b), and it will increase with the increase of Zr concentration (C_Zr) because of the higher energy entering the bubble. Using typical fission fragments (Sr, and I), it is found that the re-solution coefficient with small atomic numbers is higher than that of low-energy fission fragments with large atomic numbers. Further, we obtain the re-solution coefficient as a function of bubble radius and Zr concentration, and give the effective re-solution coefficients ($b_0^{\prime }$) in the intermediate region and the inner region according to the available experimental data. The value of the intermediate region is close to that of existing model, while the re-solution coefficient in the inner region is 3 orders of magnitude higher. This also shows that the fission gas behaviors in different phases are obviously different, which need more atomic-scale calculations in future.