Final report: Phase stability and segregation in Alloy 22 base metal and weldments

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LaCombe, Jeffrey
Alloys – Corrosion; Alloys – Testing; Chromium alloys – Testing; Chromium alloys – Corrosion; Metallurgy; Molybdenum alloys – Testing; Molybdenum alloys – Corrosion; Nevada – Yucca Mountain; Radioactive waste canisters; Radioactive wastes – Storage – Research; Tungsten alloys – Testing; Tungsten alloys – Corrosion; Materials Science and Engineering; Metallurgy
report description
At the outset of this project, the design of the waste disposal containers relied heavily on encasement in a multi-layered container, featuring a corrosion barrier of Alloy 22, a Ni-Cr- Mo-W based alloy with excellent corrosion resistance over a wide range of conditions. The fundamental concern from the perspective of the Yucca Mountain Project, however, was the inherent uncertainty in the (very) long-term stability of the base metal and welds. Should the properties of the selected materials change over the long service life of the waste packages, it was conceivable that the desired performance characteristics (such as corrosion resistance) would become compromised, leading to premature failure of the system. To address this, we studied aspects of the phase stability and solute segregation characteristics of Alloy 22 base metal, and the manner in which these affected corrosion resistance. This work was conducted as an independent validation, to add to confidence in the extrapolated behavior of the container materials over time periods that are not feasibly tested in a laboratory.