The Proposed Yucca Mountain Repository from a Corrosion Perspective
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The Proposed Yucca Mountain Repository from a Corrosion Perspective Joe H. Payer Department of Materials Science and Engineering Case Western Reserve University Cleveland, Ohio 44106-7204, U.S.A. ABSTRACT In this paper, the proposed Yucca Mountain Repository is viewed from a corrosion perspective. A major component of the long-term strategy for safe disposal of nuclear waste at the Yucca Mountain Repository is first to completely isolate the radionuclides in the waste packages for long times and to greatly retard the egress and transport of radionuclides from penetrated packages. Therefore, long-lived waste packages are important. The corrosion resistance of the waste package outer canister is reviewed, and a framework for the analysis of localized corrosion processes is presented. An overview is presented of the Materials Performance targeted thrust of the U.S. Department of Energy/Office of Civilian Radioactive Waste Management’s Office of Science and Technology and International. The thrust program strives for increased scientific understanding, enhanced process models and advanced technologies for corrosion control. INTRODUCTION Corrosion is a primary determinant of waste package performance at the proposed Yucca Mountain Repository and will control the delay time for radionuclide transport from the waste package. The terrain above the proposed repository and a schematic drawing of waste packages in a drift are shown in figure 1 and 2, respectively. Corrosion is the most probable and most likely degradation process that will determine when packages will be penetrated and the shape size and distribution of those penetrations. In this paper, the proposed Yucca Mountain Repository is viewed from a corrosion perspective. While the views expressed here are those of the author, this paper is based on a presentation to the Nuclear Waste Technical Review Board, May 18-19, 2004 [1]. A number of scientists and engineers working on the Yucca Mountain Project contributed to that presentation. CORROSION PERSPECTIVES Corrosion resistance of the waste package outer canister A major component of the long-term strategy for safe disposal of nuclear waste at the proposed Yucca Mountain Repository is first to completely isolate the radionuclides in the waste packages for long times and to greatly retard the egress and transport of radionuclides from penetrated packages. Highly corrosion resistant metals are selected for the waste packages and drip shields of the proposed Repository: Alloy 22, a nickel-chromium-molybdenum alloy and titanium, respectively. Both Alloy 22 and titanium have high corrosion resistance in the oxidizing environments of interest for the proposed Repository. This has been recognized by
Figure 1 Proposed Yucca Mountain Repository
Figure 2 Waste packages in a drift.
European Commission (EC) countries, who have investigated both metals for potential use as waste package materials in salt, clay and granite environments as part of the EC’s Fifth Framework Programme [2] Alloy 22 is a member of a corrosion resis
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