AUTHOR=Ma Cong , Zhao Min , Xin Tianyuan , Wu Lu , Pan Rongjian , Qin Jiantao , Zhang Jing 

TITLE=Phase-field simulation of grain nucleation, growth, and Rayleigh distribution of U3Si2 nuclear fuel

JOURNAL=Frontiers in Energy Research

VOLUME=Volume 10 - 2022

YEAR=2023

URL=https://www.frontiersin.org/journals/energy-research/articles/10.3389/fenrg.2022.1080819

DOI=10.3389/fenrg.2022.1080819

ISSN=2296-598X

ABSTRACT=U3Si2 is a potential accident-tolerant fuel (ATF) due to its high thermal conductivity and uranium density relative to UO2. Grain size and distribution play an essential role in the service performance of U3Si2. However, the grain evolution is quite complicated and remains unclear, which limits the further application of U3Si2 in ATF assembly. In the present work, a phase-field model is employed to investigate the nucleation and growth of grains in U3Si2, and a statistical Rayleigh distribution is formulated to depict the grain size distribution. Our results show that the grain area increases in time according to the linear law, while the mean grain radius increases with time in a power law form with scaling growth exponent z =0.42, which is quite close to the theoretically predicted value. Grain number rises rapidly at the nucleation stage until these grains occupy the whole system. After that, grain radius and area continue to grow, and the grain number decays. Our statistical analysis shows that grain size evolution behavior in U3Si2 obeys Rayleigh distribution. Our simulation not only elucidates the nucleation and evolution of grains in U3Si2 during the thermal treatment process unambiguously but also provides a fundamental study on the investigation of grain growth, subdivision, and even amorphization in the irradiated condition, which is very important for U3Si2 used as ATF in the light water reactor.