The U.S. Department of Energy (DOE) is currently preparing a license application for the permanent disposal of high level radioactive waste at Yucca Mountain, Nevada. The proposed waste package design consists of an outer container made of Alloy 22, a corrosion resistant Ni-Cr-Mo-W alloy, surrounding an inner container made of Type 316 nuclear grade stainless steel. Under environmental conditions where passivity is maintained, the uniform corrosion rate of Alloy 22 is slow and long waste package lifetimes are projected. However, the initiation of localized corrosion processes such as pitting or crevice corrosion promoted by chloride ions may significantly decrease waste package lifetimes. An assessment of waste package performance in a range of possible in-drift conditions resulting from the evolution of the near field environment is presented in this paper. Fabrication processes such as welding increase the localized corrosion susceptibility and may also decrease waste package lifetimes. Oxyanions such as nitrate, carbonate, bicarbonate, and sulfate can inhibit localized corrosion leading, in turn to long waste package lifetimes.

Subject
Water, Aqueous environments, Sodium chloride, Corrosion initiation, Nitrates, Seepage, Crevice corrosion, Environments, Localized corrosion, Alloys, Chlorides, Wastes, Relative humidity
Keywords:
Alloy 22, localized corrosion, performance assessment, high-level waste repository
Government work published by the Association for Materials Protection and Performance (AMPP) with permission of the author(s). Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
2005
GOV
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