STP1295: Embrittlement of Reactor Core Materials

    Kreyns, PH
    Consultant, principal engineer, senior engineer, manager of Structural Materials Performance, and manager of PWR Materials Technology, Bertis Atomic Power Laboratory, Westinghouse Electric Corporation, West Mifflin, PA

    Bourgeois, WF
    Consultant, principal engineer, senior engineer, manager of Structural Materials Performance, and manager of PWR Materials Technology, Bertis Atomic Power Laboratory, Westinghouse Electric Corporation, West Mifflin, PA

    White, CJ
    Manager of Clad Test and Analysis, Knolls Atomic Power Laboratory, Martin Marietta Corporation, Schenectady, NY

    Charpentier, PL
    Consultant, principal engineer, senior engineer, manager of Structural Materials Performance, and manager of PWR Materials Technology, Bertis Atomic Power Laboratory, Westinghouse Electric Corporation, West Mifflin, PA

    Kammenzind, BF
    Consultant, principal engineer, senior engineer, manager of Structural Materials Performance, and manager of PWR Materials Technology, Bertis Atomic Power Laboratory, Westinghouse Electric Corporation, West Mifflin, PA

    Franklin, DG
    Consultant, principal engineer, senior engineer, manager of Structural Materials Performance, and manager of PWR Materials Technology, Bertis Atomic Power Laboratory, Westinghouse Electric Corporation, West Mifflin, PA

    Pages: 25    Published: Jan 1996


    Abstract

    Over a core lifetime, the reactor materials Zircaloy-2, Zircaloy-4, and hafnium may become embrittled due to the absorption of corrosion-generated hydrogen and neutron irradiation damage. Results are presented on the effects of fast fluence on the fracture toughness of: (1) wrought Zircaloy-2, Zircaloy-4, and hafnium; (2) Zircaloy-4 to hafnium butt welds; and (3) hydrogen-precharged beta-treated and weld-metal Zircaloy-4 for fluences up to a maximum of approximately 150 × 1024 n/m2 (>1 MeV). While Zircaloy-4 did not exhibit a decrement in KIC due to irradiation, hafnium and butt welds between hafnium and Zircaloy-4 are susceptible to embrittlement with irradiation. The embrittlement can be attributed to irradiation strengthening, which promotes void formation in the high-strain crack-tip region, and, in part, to the lower chemical potential of hydrogen in Zircaloy-4 compared to hafnium, which causes hydrogen to drift over time from the hafnium end toward the Zircaloy-4 end and to precipitate at the interface between the weld and base-metal interface. Neutron radiation apparently affects the fracture toughness of Zircaloy-2, Zircaloy-4, and hafnium in different ways. Possible explanations for these differences are suggested. It was found that Zircaloy-4 is preferred over Zircaloy-2 in hafnium-to-Zircaloy butt-weld applications due to absence of a radiation-induced reduction in KIC plus its lower hydrogen absorption characteristics compared with Zircaloy-2.

    Keywords:

    Zircaloys, hafnium, fracture toughness, irradiation effects, hydrides


    Paper ID: STP16200S

    Committee/Subcommittee: B10.01

    DOI: 10.1520/STP16200S


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