STP1125

    A Theoretical Model of Accelerated Irradiation Creep at Low Temperatures by Transient Interstitial Absorption

    Published: Jan 1992


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    Abstract

    A theoretical model has been developed using the reaction rate theory of radiation effects to explain experimental results that showed higher than expected values of irradiation creep at low temperatures in the Oak Ridge research reactor (ORR). The customary assumption that the point-defect concentrations are at steady state was not made; rather, the time dependence of the vacancy and interstitial concentrations and the creep rate were explicitly calculated. For temperatures below about 100 to 200°C, the time required for the vacancy concentration to reach steady state exceeds the duration of the experiment. For example, if materials parameters typical of austenitic stainless steel are used, the calculated vacancy transient dose at 100°C is about 100 dpa. At 550°C this transient is over by 10-8 dpa. During the time that the vacancy population remains lower than its steady-state value, dislocation climb is increased since defects of primarily one type (interstitials) are being absorbed. Using the time-dependent point-defect concentrations, the dislocation climb velocity has been calculated as a function of time and a climb-enabled glide creep model has been invoked. The extended transient time for the vacancies leads to high creep rates at low temperatures. In agreement with experimental observations, a minimum in the temperature dependence of creep is predicted at a temperature between 50 and 350°C. The temperature at which the minimum occurs decreases as the irradiation dose increases. Predicted values of creep at 8 dpa are in good agreement with the results of the ORR-MFE-67/7J experiment.

    Keywords:

    creep, dislocation climb, dislocation glide, fusion, irradiation creep, point defects, theoretical models, transient effects


    Author Information:

    Stoller, RE
    Research staff members and group leader, Oak Ridge National Laboratory, Oak Ridge, TN

    Grossbeck, ML
    Research staff members and group leader, Oak Ridge National Laboratory, Oak Ridge, TN

    Mansur, LK
    Research staff members and group leader, Oak Ridge National Laboratory, Oak Ridge, TN


    Paper ID: STP17891S

    Committee/Subcommittee: E10.08

    DOI: 10.1520/STP17891S


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