TRITIUM PERMEATION THROUGH AUSTENITIC STAINLESS-STEEL WITH CHEMICALLY DENSIFIED COATING AS A TRITIUM PERMEATION BARRIER

Chemically densified coating formed on the surface of austenitic stainless steel (SUS 316) was examined for compatibility with molten lithium-lead eutectic alloy (Li17-Pb83) and tritium permeability. The chemically densified coating (CDC) consisting of SiO2 particles and a Cr2O3 matrix with a thickness of 60 mu m was unstable in contact with the molten alloy as predicted from a thermodynamic calculation at 600 degrees C, and it was degraded in several days. In an in-pile experiment, specimens with the coating on the front surface or the rear surface were immersed in Li17-Pb83 molten alloy, and their tritium permeabilities were measured. The permeability of the former was reduced to 1/10 of the ideal value in the diffusion-limited case, while that of the latter was less than 1/100 of the diffusion-limited value even in a pure H-2 atmosphere. It is concluded that CDC is quite effective to reduce tritium permeability in the condition of not contacting molten Li17-Pb83 alloy.