Study on Hydrogen Absorption of Titanium Overpack
Wada, Ryutaro*; Nishimura, Tsutomu*; Nakanishi, Tomoaki*; Fujiwara, Kazuo*; Inoue, Takao*; Tateishi, Tsuyoshi*; Masugata, Tsuyoshi*
Titanium is being studied for the high-level radioactive waste package material. Titanium has good corrosion resistance, however there is the possibility of hydrogen embrittlement with absorption of hydrogen in reducing condition. Experimental studies were performed to evaluate the hydrogen absorption behaviors of titanium in reducing condition. The failure model of the titanium overpack was also examined from the viewpoint of fracture mechanism in order to evaluate the fracture behavior of the titanium overpack caused by the hydrogen absorption. (1) Scratch test was conducted in reduce condition. The surface films on the titanium specimen were analyzed to examine the changes of the existing films and the growth phenomena of the regenerated films on the titanium specimen. (2)The long-term reaction test of the titanium specimen using the glass-seal ampoules maintaining reducing condition was conducted and analyses of the hydrogen gas generation and absorption quantitative as well as the generated film evaluation were performed. (3) Under reducing condition, the electrochemical acceleration tests of the titanium specimen were conducted. The effect of acceleration rate on the hydrogen absorption and surface film was evaluated, and the prediction as to the hydrogen absorption behavior at a natural state was also made. (4) The prediction of the maximum residual stress and the evaluation of crack growth of the titanium overpack based on the previous studies were performed. Feasibility of the modeling of fracture phenomenon with existing analysis technique was examined and the items to be developed were also discussed.