Effect of liquid lithium corrosion on deuterium permeation behavior of niobium membranes

• Liquid-lithium corrosion leads to a pronounced enhancement of deuterium permeation in niobium membranes. • The apparent activation energy for permeation decreases by ∼ 14 kJ·mol −1 after prolonged lithium exposure. • Corrosion-induced lattice strain and defect accumulation enable an approximately one-order-of-magnitude increase in deuterium permeability. Efficient extraction of bred hydrogen isotopes from liquid-lithium breeder blankets is essential for fuel self-sufficiency in deuterium–tritium (D–T) fusion reactors, yet the behavior of candidate permeation membranes such as niobium under direct liquid-lithium corrosion remains inadequately characterized. In this study, high-purity niobium membranes were exposed to static liquid lithium at 673 K for 200, 400, and 600 h. After exposure, the samples were analyzed using scanning electron microscopy (SEM), grazing-incidence X-ray diffraction (GIXRD), surface profilometry, and Vickers hardness testing, while deuterium permeation fluxes were measured as a function of temperature to determine permeability and apparent activation energy. The corrosion rate was nearly constant (∼8.0 × 10 -4 μm·h −1 ), suggesting an approximately linear corrosion behavior under the present static conditions. SEM revealed progressive pitting and surface roughening, whereas GIXRD showed a shift of the Nb (110) peak from 38.252° to 38.287° and peak broadening, indicative of lattice contraction and defect accumulation. Surface hardness decreased systematically. Most notably, the steady-state deuterium flux of the 600 h–corroded sample increased by approximately one order of magnitude, with the apparent activation energy decreasing from 119.8 to 105.9 kJ·mol −1 . These results suggest that corrosion-induced defects and surface roughening modify the effective transport resistance and create additional pathways for deuterium transport. Overall, niobium remains a promising membrane candidate for hydrogen isotope transport under liquid-lithium exposure, and the present results suggest that corrosion-induced surface and near-surface modifications can influence permeation behavior under temperature-relevant laboratory conditions.