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    Effects of Hydride Morphology on Zr-2.5Nb Fracture Toughness


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    The effects of hydride morphology on the axial fracture toughness of cold-worked Zr-2.5Nb pressure tube material have been determined between room temperature and 240°C. Tests were performed on small compact tension specimens machined from samples of material prepared with different morphologies and hydrogen concentrations. The morphologies were characterized by a parameter referrred to as the hydride continuity coefficient (HCC), which provides a measure of the extent to which hydrides are oriented in the axial-radial plane of the pressure tube. Hydrides in this orientation are known to be detrimental to the fracture properties of the tube. Fracture toughness was characterized by a J-R curve technique, from which it is possible to estimate the maximum stable size of a through-wall axial crack for typical reactor operating conditions. Material with HCC values greater than 0.5 exhibited low toughness from room temperature to 240°C, at which temperature there was an abrupt transition to an upper shelf toughness value. As HCC decreases, the transition to upper shelf toughness occurs more gradually and is complete at a lower temperature.


    Zr-2.5Nb, fracture toughness, hydride morphology, hydrogen concentration, hydride continuity coefficient, J-R, curve, pressure tubes

    Author Information:

    Wallace, AC
    Engineers, Ontario Hydro Research Division, Toronto,

    Shek, GK
    Engineers, Ontario Hydro Research Division, Toronto,

    Lepik, OE
    Engineers, Ontario Hydro Research Division, Toronto,

    Committee/Subcommittee: B10.05

    DOI: 10.1520/STP18858S