Quantitative imaging of hydrogen in zirconium alloy cladding by Laser Induced Breakdown Spectroscopy

Hydrogen in solids is of high importance in several industries as it may induce embrittlement or stress in metallic materials. In zirconium-based nuclear fuel claddings, assessing its concentration and distribution at micro- and macro-scales is critical to understanding hydrogen uptake and embrittlement mechanisms. Despite its importance, hydrogen remains one of the most challenging elements to quantify and spatially map in solids due to its low atomic number, high mobility, susceptibility to contamination, and limited availability of spatially resolved analytical techniques. This paper presents a methodology for quantitative hydrogen analysis in zirconium alloys using Laser-Induced Breakdown Spectroscopy (LIBS), combining atmospheric-pressure operation, rapid acquisition, and micrometric spatial resolution. To ensure reliable LIBS-based hydrogen quantification, the methodology focused on the control of sample preparation, ambient hydrogen contribution, signal stability, and calibration robustness. Hydrogen calibration curves were established using hydrogen-charged zirconium alloy standards covering 12–4100 wppm. After optimization, a linear response between the H I 656.28 nm emission line and hydrogen concentration was obtained, with excellent linearity (R² = 0.99) and an estimated detection limit lower than 100 wppm. ... mehrRepeatability and reproducibility studies demonstrated robust measurement stability, while the use of both Zircaloy-4 and M5Framatome alloys confirmed limited matrix effects under
the selected conditions. Hydrogen maps acquired at 12 μm spatial resolution on steam-oxidized cladding revealed heterogeneous distributions consistent with oxidation-induced microstructural transformations. Quantitative comparison with Neutron Imaging showed excellent agreement, confirming the validity of LIBS for quantitative hydrogen mapping and highlighting its potential as an accessible alternative.