About this Abstract |
| Meeting |
Materials in Nuclear Energy Systems (MiNES) 2025
|
| Symposium
|
Materials in Nuclear Energy Systems (MiNES) 2025
|
| Presentation Title |
How Faulted Loops Form in Fluoride Oxide Under Irradiation: Insights From Atomistic Simulations |
| Author(s) |
Lin-Chieh Yu, Shuxiang Zhou, Linu Malakkal, Marat Khafizov, David Hurley, Yongfeng Zhang |
| On-Site Speaker (Planned) |
Lin-Chieh Yu |
| Abstract Scope |
Understanding how defects evolve under irradiation – where atomic displacements generate defects of vacancy and interstitial types – is critical for unlocking the full potential of fluorite oxides in nuclear energy applications. In fluorite oxides fuel like UO2 and ThO2, interstitials often aggregate into dislocation loops, degrading thermal conductivity and promoting swelling, which undermines fuel performance and safety. Yet, the mechanism behind loop formation remains obscure due to challenges in scale, even for state-of-the-art techniques: the atomic evolution processes are too small for direct observation and too complex for modeling. Notably, the low mobility of cation interstitials predicted by density functional theory (DFT) cannot account for the widespread experimental observation of loop formation. Using ThO2 as a model system, we employed computationally efficient molecular dynamics (MD) simulations to capture the real-time evolution of initially isolated thorium and oxygen interstitials to identify stable and mobile interstitial clusters. The thermal stability and mobility of kinetically favorable interstitial clusters were further validated through high-accuracy DFT calculations. Three critical steps are identified that lead to faulted loop formation: i) enhanced diffusion of immobile thorium interstitials via absorption of oxygen interstitials, ii) formation and growth of fast, 1D-migrating thorium interstitial clusters, and iii) transformation of large clusters into faulted loops, which eventually unfault into full loops. This novel mechanism differs from that in metals and also operates in UO2 and CeO2, offering new insights into defect evolution and ion transport in fluorite oxides. |
| Proceedings Inclusion? |
Undecided |