Materials for high-level waste canister/overpacks in salt formations

Studies on the corrosion and mechanical behavior of TiCode-12 and other titanium alloys to be used as candidate canister or overpack barriers in a high-level waste (HLW) repository or test facility in salt have been in progress at Sandia National Laboratories since 1976. Titanium alloys were selected as the primary materials for detailed testing based on candidate screening analyses (general corrosion and economic assessments) of about 20 different alloys. The corrosion behavior of TiCode-12 has been evaluated as a function of: brine composition, temperature, time, pH, oxygen concentration, and gamma radiolysis. Uniform corrosion rates are in the range of 0.1 to 10 μm/yr; no significant pitting or crevice corrosion has been observed. This can be compared to the long-term measured rate of 0.13 mm/yr for ductile cast iron in Brine A, analyzed as a corrosion allowance canister material