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=10

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=<p>U<sub>3</sub>Si<sub>2</sub> is a potential accident-tolerant fuel (ATF) due to its high thermal conductivity and uranium density relative to UO<sub>2</sub>. The grain size and distribution play an essential role in the service performance of U<sub>3</sub>Si<sub>2</sub>. However, the grain evolution is quite complicated and remains unclear, which limits further application of U<sub>3</sub>Si<sub>2</sub> in the ATF assembly. In the present work, a phase-field model is employed to investigate the nucleation and growth of grains in U<sub>3</sub>Si<sub>2.</sub> Our results show that the number of grains rises rapidly at the nucleation stage until they occupy the whole system. After that, the grain radius and area continue to grow, and the grain number decays. 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 the scaling growth exponent z = 0.42, which is quite close to the theoretically predicted value. Finally, we performed statistical analysis and found that the grain size evolution of U<sub>3</sub>Si<sub>2</sub> obeys Rayleigh distribution. Our simulation not only elucidates the nucleation and evolution of grains in U<sub>3</sub>Si<sub>2</sub> 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 U<sub>3</sub>Si<sub>2</sub> used as ATF in the light water reactor.</p>