Long Term Hydrogen Absorption Behavior and Hydrogen Embrittlement of Titanium Overpack under Anaerobic Condition

Abstract

The long term hydrogen absorption behavior and the possibility of hydrogen embrittlement were studied for titanium overpack for high level radioactive waste disposal. The results of galvanostatic cathodic polarization tests showed that as the cathodic current density was decreased, the amount of absorbed hydrogen for a constant amount of cathodic charge was increased and hydrogen permeated into inside of titanium specimen. The results of mechanical property tests of hydrogen-charged titanium specimens showed that the most remarkable embrittlement was observed in the titanium specimens in which hydrogen was distributed uniformly. The amount of absorbed hydrogen for 1000 years in titanium overpack of 6 mm thickness was estimated to be about 400 ppm. It was expected that the rupture of titanium overpack with uniform hydrogen distribution would be initiated in case that the crack size in titanium was over about 2-3 mm under the stress condition correspond to yield strength.