Abstract
Understanding irradiation damage and tritium transport in LiAlO2 ceramics is essential for their deployment in tritium-producing burnable absorber rods (TPBARs). Grain boundaries (GBs) play an important role in governing radiation response and tritium transport in LiAlO2 and its secondary phase LiAl5O8. Using molecular dynamics simulations, we investigated defect evolution and tritium diffusion during displacement cascades in single-crystal and bicrystal LiAlO₂ and LiAl₅O₈ at 600 K. The results reveal that GBs suppress the damage in the LiAlO2 bicrystals as compared to single crystals, via interstitial emission. The effect is more pronounced for Li defects, than for Al and O. In LiAl₅O₈, the damage reduction due to the introduction of GB is less pronounced overall. Tritium diffusion coefficients at GBs are higher by factors of 2–10 relative to diffusion inside the grain bulk. The effect is particularly pronounced in LiAlO₂, where Σ5, Σ17, and Σ25 GBs promote rapid tritium transport, whereas LiAl₅O₈ exhibits slower diffusion due to reduced free volume at its GBs. These findings evince a trade-off that while GBs mitigate radiation damage by absorbing interstitials, they simultaneously provide fast pathways for tritium migration, which is not desirable for TPBAR application. The mechanistic insights gained here establish a foundation for microstructural design strategies to balance radiation tolerance and tritium retention in ceramic breeder materials.
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The datasets generated and analyzed during the current study are not publicly available due to their use in an ongoing study, but are available from the corresponding author on reasonable request.
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The Python code used for this study is not publicly available, but hints/discussion about the code may be provided on reasonable request from the corresponding author.
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Acknowledgements
This work was funded by the Tritium Modernization Program within the National Nuclear Security Administration (NNSA) of the US Department of Energy (DOE) through the Tritium Technology Program at Pacific Northwest National Laboratory. This research was carried out using institutional computing resources at Pacific Northwest National Laboratory. PNNL is a multiprogram national laboratory operated by Battelle Memorial Institute for the US DOE under DE-AC06-76RLO 1830.
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A.R.: conceptualization, investigation, visualization, writing—original draft, and writing— review and editing. W.J.: investigation, writing—original draft, and writing—review and editing. A.M.C.: writing—review and editing, conceptualization, resources, and funding acquisition, D.J.S.: writing—review and editing. R.D.: writing—review and editing. A.S.: writing—review and editing.
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Roy, A., Jiang, W., Casella, A.M. et al. Grain boundary effects on radiation damage and tritium diffusion in Li–Al–O ceramics from molecular dynamics and experiments. npj Mater Degrad (2026). https://doi.org/10.1038/s41529-026-00766-z
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DOI: https://doi.org/10.1038/s41529-026-00766-z
