STP1423: Characteristics of Hydride Precipitation and Reorientation in Spent-Fuel Cladding

    Chung, HM
    Argonne National Laboratory, Argonne, IL

    Daum, RS
    Argonne National Laboratory, Argonne, IL

    Hiller, JM
    Argonne National Laboratory, Argonne, IL

    Billone, MC
    Argonne National Laboratory, Argonne, IL

    Pages: 22    Published: Jan 2002


    Abstract

    Transmission electron microscopy (TEM) was used to examine Zircaloy fuel ladding, either discharged from several PWRs and a BWR after irradiation to fluence levels of 3.3 to 8.6 × 1021 n cm-2 (E > 1 MeV) or hydrogen-charged and heat-treated under stress to produce radial hydrides; the goal was to determine the microstructural and crystallographic characteristics of hydride precipitation. Morphologies, distributions, and habit planes of various types of hydrides were determined by stereo-TEM. In addition to the normal macroscopic hydrides commonly observed by optical microscopy, small “microscopic” hydrides are present in spent-fuel cladding in number densities at least a few orders of magnitude greater than that of macroscopic hydrides. The microscopic hydrides, observed to be stable at least up to 333°C, precipitate in association with <c>-type dislocations. While the habit plane of macroscopic tangential hydrides in the spent-fuel cladding is essentially the same as that of unirradiated unstressed Zircaloys, i.e., the {107}Zr plane, the habit plane of tangential hydrides that precipitate under high tangential stress is the {104}Zr plane. The habit plane of radial hydrides that precipitate under tangential stress is the {011} Zr pyramidal plane, a naturally preferred plane for a cladding that has 30° basal-pole texture. Effects of texture on the habit plane and the threshold stress for hydride reorientation are also discussed.

    Keywords:

    spent-fuel cladding, radial and tangential hydrides, macroscopic and microscopic hydrides, habit plane, texture, <c>-type dislocations


    Paper ID: STP11406S

    Committee/Subcommittee: B10.02

    DOI: 10.1520/STP11406S


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