STP909

    Reactor Pressure Vessel Structural Implications of Embrittlement to the Pressurized-Thermal-Shock Scenario

    Published: Jan 1986


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    Abstract

    A deterministic fracture-mechanics parametric-type analysis of a generic pressurized-water reactor pressure vessel has been conducted for loading conditions imposed by a specific category of hypothetical pressurized-thermal-shock transients. The time in the life of the vessel for which the calculations were made corresponds to attainment of the limiting nil-ductility transition reference temperature specified by the U. S. Nuclear Regulatory Commission's pressurized thermal-shock-issue-related screening criteria.

    The transients considered were characterized by a constant pressure and an exponential decay of the downcomer coolant temperature. The decay constant, the final temperature of the coolant, and the fluid-film heat-transfer coefficient were the variable parameters. A search was performed to determine the critical pressure corresponding to incipient crack initiation for a range of crack depths up to 20% of the wall thickness. Results indicate that the critical pressure is greater than the normal operating pressure, if the coolant final temperature is greater than 150°C.

    The fracture mechanics model used in the study tends to be conservative in the sense that it ignores possible beneficial effects of warm prestressing and cladding.

    Keywords:

    pressure vessel steels, radiation effects, screening criteria, reactor pressure vessels, over-cooling accident, pressurized thermal shock, neutron embrittlement, linear elastic fracture mechanics, crack initiation, reference temperature, flaws (materials), stress intensity factor


    Author Information:

    Iskander, SK
    Resident engineer, U. S. Nuclear Regulatory Commission,

    Universitaet Stuttgart (MPA),

    Sauter, AW
    Staff members, Universitaet Stuttgart (MPA),

    Föhl, J
    Staff members, Universitaet Stuttgart (MPA),


    Paper ID: STP23035S

    Committee/Subcommittee: E10.07

    DOI: 10.1520/STP23035S


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