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    Use of a Ductile Tearing Instability Procedure in Establishing Pressure-Temperature Limit Curves

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    Fracture mechanics analysis procedures have been used in the nuclear power industry for almost 15 years to establish allowable pressure-temperature limit curves. In this procedure, a reference flaw is assumed to exist, and the pressure-temperature limits that will allow safe operation of the plant are determined. As a plant ages, the analysis must be updated periodically to take into account any possible degradation of the pressure vessel material due to irradiation.

    Until recently, this procedure was based on linear elastic fracture mechanics and was applicable only over a limited portion of the operating temperature range. This paper describes a proposed new approach to this analysis procedure which makes use of both elastic fracture mechanics techniques and a new ductile tearing instability analysis to establish allowable pressure-temperature limit curves over the entire operating temperature range.

    The ductile tearing instability analysis is based on the deformation plasticity failure assessment diagram. The paper describes in detail how this procedure will be applied. Safety factors and acceptance criteria are proposed.

    A discussion of the materials properties needed to perform the analysis is presented. The properties used in the analysis include the KIR curve from the American Society of Mechanical Engineers Boiler and Pressure Vessel Code, J-R curves, and stress-strain properties of the vessel material. An example problem showing the application of the overall approach is included in the paper.


    fracture mechanics, tearing instability, pressure-temperature limit, elastic-plastic fracture, deformation plasticity failure assessment diagram, nonlinear fracture mechanics

    Author Information:

    Yoon, KK
    Advisory engineer, Babcock & Wilcox Co., Lynchburg, VA

    Bloom, JM
    Technical advisors, Structural Mechanics and Materials,

    Van Der Sluys, WA
    Technical advisors, Structural Mechanics and Materials,

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP27720S