| Abstract Scope |
Hydrogen isotopes play a critical role in the performance and safety of nuclear materials, yet their direct characterization remains challenging due to low mass and high mobility. Atom probe tomography (APT), particularly in its cryogenic implementation (cryo-APT), offers a unique pathway for three-dimensional mapping of hydrogen at near-atomic resolution. Here, we highlight the potential of cryo-APT to quantify hydrogen and deuterium distributions, identify trapping sites, and correlate isotope localization with microstructural features in steels and model nuclear alloys. By integrating cryogenic specimen preparation and transfer with correlative micromechanical testing, our approach minimizes artefacts from hydrogen ingress and redistribution. Recent studies demonstrate identification of lattice, interface, and defect-associated trapping, providing insight into hydrogen embrittlement mechanisms. Extending these capabilities to irradiated and tritium-bearing materials could enable unprecedented understanding of isotope behavior in nuclear environments, supporting the design of embrittlement-resistant, radiation-tolerant structural materials. |