Materials Behavior in HTGR Environments (NUREG/CR-6824, ANL-02/37)

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Publication Information

Manuscript Completed: February 2003
Date Published: July 2003

Prepared by:
K. Natesan, A. Purohit, S.W. Tam
Argonne National Laboratory
9700 South Cass Avenue
Argonne, Illinois 60439

C.A. Greene, NRC Project Manager

Prepared for:
Division of Engineering Technology
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

NRC Job Code Y6537

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The report reviews and evaluates data currently available on materials performance and long-term behavior in High-Temperature Gas-Cooled Reactors (HTGRs), including the Gas Turbine-Modular Helium Reactor (GT-MHR) and the Pebble Bed Modular Reactor (PBMR). As part of the evaluation, the report identifies the materials that have been used in HTGRs, their functions, and the environmental conditions under which they need to perform adequately. The report identifies the materials used for structural applications (such as pressure vessel and reactor primary circuit components, including internals) and for the power conversion system, with emphasis on gas-turbine-based HTGRs. The report examines the chemistry of the primary-circuit helium environment from the standpoint of type and concentration of impurities. A framework is presented for analyzing gas-solid interactions in single and bioxidant conditions, and the data on materials scaling behavior are compared from several research programs. This report discusses the available data on the mechanical properties (such as creep, fatigue, creep fatigue, and crack growth) of candidate materials in a helium environment. Available information on the carburization, decarburization, oxidation, and aging of structural materials and their effects on mechanical properties is summarized. From the materials standpoint, the report also discusses the role of particulate-laden gases in corrosion-erosion and the possible effects on materials from off-normal situations in the operation of the reactors. The report makes several recommendations to supplement the data on environmental effects on materials, on mechanical properties of structural and power conversion materials, and on alternative candidate alloys for application in HTGRs.

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