Deuterium permeation behavior in iron-irradiated erbium oxide coating

Abstract

Tritium permeation barrier has been developed for mitigating fuel loss and radiological concern at a fuel breeding/recovery system in a D-T fusion reactor. Recent research effort has been dedicated to erbium oxide coatings, and various hydrogen permeation behaviors except for irradiation effects have been elucidated. In this study, irradiation effects on deuterium permeation through erbium oxide coatings have been investigated by iron-ion irradiation at elevated temperature followed by deuterium gas-driven permeation experiments. The coatings deposited on reduced activation ferritic steel substrates with displacement damages of 0.01–1 dpa showed one or two orders of magnitude different permeabilities at 300–500°C; however, the permeabilities became comparable and lower than that of unirradiated at 550–700°C, indicating the grain growth and the formation of grain boundaries with a lower permeability. Cross-sectional transmission electron microscopy with selected-area electron diffraction for the coatings before and after the permeation experiments indicated the formation of a defect-accumulated region. The stability of the region strongly depends on the irradiation condition: damage concentration and annealing time, resulting in the difference of the permeability and diffusivity in the lower temperature range.