The synergy of heavy-ion irradiation and lithium-lead corrosion on deuterium permeation behavior of ceramic coating

Abstract

Functional ceramic coatings have been investigated for several decades to mitigate tritium permeation through structural materials in a fusion reactor blanket. For the establishment of a liquid blanket system, the coatings require not only tritium permeation reduction but also the tolerance to irradiation damage induced by neutrons and corrosion by liquid tritium breeders. In this study, deuterium permeation measurements under exposure to liquid lithium–lead were performed for a heavy-ion-irradiated zirconium oxide coating sample to elucidate the synergy of irradiation and corrosion on hydrogen isotope permeation. The irradiated coating decreased the deuterium permeation flux under lithium–lead exposure by more than two orders of magnitude in comparison with the unirradiated one. Each activation energy of permeation and diffusion of the coating sample was larger than that of the unirradiated one at around 450 °C and decreased to the level of the unirradiated one at 600 °C. The results indicated that the voids formed by ion irradiation aggregated in grain boundaries of the coating, resulting in an increase in the energy barrier of diffusion at low temperatures and then a decrease due to the defect recovery at high temperatures. Besides, a corrosion product layer formed on the coating during lithium–lead exposure increased the energy barrier of solution. The synergy of irradiation and corrosion on permeation was developed at lower temperatures before the defect recovery.

Keywords

• Tritium
• Permeation
• Ceramic coating
• Irradiation
• Corrosion