Abstract
Effects of bentonite clay, applied potential, pH of solution and cathodic polarization time on hydrogen absorption into titanium, which is one of the candidate materials of over-pack for high-level radioactive waste container, have been investigated in artificial underground water. Considering the result at various test time, and assuming the hydrogen absorption is ruled by the parabolic law, the amount of hydrogen after 1000 year exposure calculated to about 17 ppm, which will be absorbed at the applied potential of -0.51V vs. SHE corresponds to equilibrium potential of hydrogen. It seems that the assumption of the parabolic law and the test period up to 1440 h are proper, because the linear relations were obtained between the amount of absorbed hydrogen and the logarithm of the averaged cathodic current and between the slopes of the lines and a square root of the test time. Titanium seems to have a life over 1000 years in deep underground depository according to assumption that about 500 ppm absorbed hydrogen is critical for hydrogen embrittlement of titanium.
