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Summary:
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¿̐ưC. 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¿̐ưC, 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.
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Electronic reproduction. W. Conshohocken, Pa. : ASTM International, 1989. Mode of access: World Wide Web. System requirements: Web browser. Access may be restricted to users at subscribing institutions.
