SYMPOSIA PAPER Published: 01 January 1989

Effects of Hydride Morphology on Zr-2.5Nb Fracture Toughness


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.

Author Information

Wallace, AC
Ontario Hydro Research Division, Toronto, Canada
Shek, GK
Ontario Hydro Research Division, Toronto, Canada
Lepik, OE
Ontario Hydro Research Division, Toronto, Canada
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Developed by Committee: B10
Pages: 66–88
DOI: 10.1520/STP18858S
ISBN-EB: 978-0-8031-5084-3
ISBN-13: 978-0-8031-1199-8