Characterization of Chemical Densified Coating as Tritium Permeation Barrier

In a fusion blanket design, ceramic coating on structural materials has been considered to be used as a tritium permeation barrier. The Chemical Densified Coating (CDC) method has some advantage compared with another coating method. This method is capable to form densified coating on either the outer or the inner surface of a tube or a container. This process temperature is low (450°C). The fabrication technique of Cr₂O₃-SiO₂ coating had been developed using CDC method. However, Cr₂O₃-SiO₂ coating had open pores in the coating. For filling open pores, the densification treatment by CrPO₄ was examined. In this study, the verification of open pores, the thermal shock resistivity, the adhesion strength and the deuterium permeability were evaluated and compared with Cr₂O₃-SiO₂ (Type 1) coating and Cr₂O₃-SiO₂ including CrPO₄ (Type 2) coating. From these results, it was confirmed that Type 2 coating had a good adhesion property, and permeation reduction factor of SS316 with Cr₂O₃-SiO₂ including CrPO₄ coating reached about 1,000 at 600°C.