STP918: Analysis of the Unstable Fracture of a Reactor Pressure Tube Using Fracture Toughness Mapping

    (Peter) Chow, CK
    Research officer and manager, Materials and Mechanics Branch, Whiteshell Nuclear Research Establishment, Atomic Energy of Canada Limited, Pinawa Manitoba,

    Simpson, LA
    Research officer and manager, Materials and Mechanics Branch, Whiteshell Nuclear Research Establishment, Atomic Energy of Canada Limited, Pinawa Manitoba,

    Pages: 24    Published: Jan 1986


    Abstract

    On 1 August 1983, a Zircaloy-2 pressure tube in Ontario Hydro's Pickering-2 reactor failed by the unstable propagation of an axial crack. The reactor was quickly and safely shut down, without the need for any emergency cooling, and an extensive investigation into the event was initiated. One factor requiring explanation was the apparent failure of the leak-before-break principle, that is, why was the initiating flaw not detected by leakage prior to growing to an unstable size? This paper describes part of a program to address this question, which involved mapping the fracture toughness of the pressure tube as a function of position over the cracked region. The results of the fracture toughness mapping, plus selected fractography, are used to explain the sequence of events that occurred during the tube failure.

    Keywords:

    zirconium, pressure tube, zirconium hydride, critical crack length, fracture toughness, J, -resistance curve


    Paper ID: STP19328S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP19328S


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