F.S. Altamimi, Maddison Coke, B.F. Spencer, Sadia Sheraz, Emily Aradi, Matthew Lindley, NP Lockyer, RJ Curry, S.J. Haigh, C.A. Sharrad, A.N. Jones
Nuclear graphite, used as a moderator and structural component in nuclear reactors, is a key candidate material for advanced systems operating at temperatures up to 1000 °C. Integrity of the crystal lattice is critical for graphite performance as a moderator. Here, we present a systematic investigation of low-energy heavy-ion implantation in nuclear-grade graphite (IG-110). Heavy ion irradiation produces severe lattice fragmentation and near-complete loss of long-range order within the top ∼50 nm. Upon exposure to 750–1100 °C under helium, replicating advanced reactor conditions, partial recrystallisation occurs through the formation of short-range ordered graphitic domains rather than full lattice restoration, yielding nanocrystalline graphite. Novel nanoscale Electron Energy-Loss Spectroscopy (EELS) hybridisation mapping quantified lattice re-ordering, revealing ∼50% recovery of sp 2 bonding after heating to 1100 °C. A consistent microscale recovery was observed via Raman spectroscopy, confirming nanocrystalline graphite formation. Experimentally measured damage profiles exceeded ballistic implantation predictions, while ion distribution was shallower than predicted in implantation models, highlighting limitations of conventional ion–solid interaction models in disordered graphitic systems. Further chemical analysis revealed the presence of metallic, carbide, and oxide forms of cobalt after irradiation. Collectively, this work establishes a correlative multiscale structural–chemical framework for understanding radiation damage, lattice recovery at reactor conditions, and impurity distribution in nuclear graphite after low-energy heavy-ion irradiation, advancing the understanding of graphite behaviour in advanced reactor systems. • Partial recovery of severe ion-irradiation damage in graphite was achieved under HTGR conditions, with reformation of short-range ordered domains and basal-plane features. • Distribution of sp 2 /sp 3 using nanoscale mapping with EELS revealed ∼50% recovery of the sp 2 fraction toward the virgin state was achieved after heating at 1100 °C. • Implanted cobalt was identified in metallic, oxide, and carbide forms, providing valuable insights into ion speciation and mobility. • Observed structural recovery improves understanding of the in-service behaviour of HTGR graphite, suggesting potential lifetime extension compared to current operational environments.