Effect of moisture in sweep gas on chemical compatibility between ceramic breeder and EUROFER97

Effect of moisture in sweep gas on chemical compatibility between ceramic breeder (Li4SiO4 with 20 mol% of Li2TiO3) and EUROFER97 was examined in this study. These materials were contacted and heated at 623, 823, and 1073 K for up to 12 weeks where the H2O concentrations of the outlet gas were 0.13-0.24 vol.%. In the two-phase breeder specimen, Li4SiO4 was preferably decomposed into Li2SiO3 with a possible formation of Li2O or LiOH depending on environmental condition. Formation of corrosion layers on the EUROFER specimen was enhanced in the wet condition, especially at the elevated temperatures of 823 and 1073 K. Though these results showed parabolic growth rates, an extrapolation from data of the elevated temperatures to 623 K was not feasible in the wet atmosphere, which could derive from the difference of the chemical form in the breeder specimen. Effective diffusion coefficient of oxygen into EUROFER at 623 K was given to be 4.5 × 10−14 cm2/s and a possible thickness of the corrosion layer after a 2-year use was predicted.