Applicability of titanium to overpack material for high-level radioactive waste disposal and current status of lifetime assessment of titanium overpack

Taniguchi, Naoki 

Titanium is one of the candidate materials for overpacks for geological isolation of high-level radioactive waste. This paper outlines the basic concept of titanium overpack and its long term integrity from the view point of resistance to crevice corrosion, general corrosion and hydrogen embrittlement. Crevice corrosion can be avoided by selecting appropriate alloy that are compatible with environmental condition based on the data on the critical condition for the initiation of crevice corrosion. Titanium is not suitable to overpack in high carbonate or high pH environment since its corrosion rate under aerobic condition is relatively large. Except for such environments, titanium overpack would not be penetrate by general corrosion and hydrogen embrittlement for over 1000 years by designing adequate thickness.