LINGHU Feng, WANG Huacai
(Reactor Engineering Technology Research Institute, China Institute of Atomic Energy, Beijing 102413, China)

Abstract: As a core component of commercial reactors such as light water reactors (LWRs), changes in UO₂ ceramic fuel pellets during operation affect the operational safety of the reactors. Extending the life of fuel elements to achieve higher economic efficiency is the future development direction of nuclear power plants. With the increase of fuel burnup, the microstructure of the fuel pellets undergoes certain changes, the generation and migration of fission products increase, the probability of pellet-cladding interaction increases, and the safety factor of reactor operation decreases, so the study of the microstructural evolution of ceramic fuel pellets under high burnup has been emphasized. This paper was aimed to summarize the research progress in fission products of ceramic UO₂ pellets, including the characteristics and formation mechanism of high burnup structures, the distribution and influence of fission products, and the links between microstructure evolution and fission product migration. The microstructure evolution of the pellets under high burnup and its impact on fission product migration will be discussed. Finally, the prospect of further research on fuel pellets under high fuel consumption is proposed.
Key words: UO₂ ceramic fuel pellet; microstructure; high burn-up; fission product