STP1325

    Irradiation Creep in Nickel Containing and in Manganese Containing Stainless Steel Alloys

    Published: Jan 1999


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    Abstract

    This is a final report on the results of measurements of neutron irradiation creep which have been performed in non-instrumented creep rigs (Trieste) on many different stainless steel alloys during the last fifteen years in high flux positions in the High Flux Reactor (HFR) at Petten. The creep elongations were measured in hot cells during reactor shut down periods. A few investigations of the creep elongation were performed in fully instrumented creep rigs (Crisp).

    All the materials were irradiated in the as-received state, which was usually a type of solution-annealed state, after annealing at 400, or at 600, or at 800°C, and after 20% cold work. The irradiation temperature ranged from 300 to 500°C and the applied stresses were between 25 and 300 MPa.

    The variations in length found up to irradiation doses of about 5 dpa are mainly attributed to the formation of radiation-induced microstructural changes, which are connected either with increases or with decreases in the volume of the materials. We are advancing an interpretation of the data which is not without contradictions. We believe that among the many microstructural changes only the formation of carbides, which is connected with an increase in volume, and only the formation of α-ferrite, which is connected with a decrease in volume, are of importance. The α-ferrite phase is very brittle, decreasing the ductility of the stainless steels dramatically.

    An almost thermal equilibrium state of microstructure while irradiating with high energy particles is obtained after about 5 dpa, depending also on the irradiation temperature. The increase in length obtained for doses larger than 5 dpa is attributed mainly to irradiation creep. The normalized creep rates for all stainless steel materials are almost equal in HFR, ORR, and in EBR II. The creep rates increase linearly with stress and flux, and they are slightly dependent on the irradiation temperature (Qirr= 0.132 eV) for irradiation temperatures below about 450°C. For irradiation temperatures above 450°C a contribution of thermal vacancies to irradiation creep is noticed and the irradiation creep rates can no longer be ascribed to a simple irradiation creep relation.

    Keywords:

    neutron irradiation creep, High Flux Reactor at Petten, Oak Ridge Research Reactor, and Experimental Breeder Reactor II at Idaho, stainless steel alloys, microstructure, α-ferrite, carbides, radiation damage, phase diagram


    Author Information:

    Hausen, H
    Institut für Angewandte Physik der Johann Wolfgang Goethe-Universität Frankfurt, Frankfurt,

    Schüle, W
    Institut für Angewandte Physik der Johann Wolfgang Goethe-Universität Frankfurt, Frankfurt,


    Paper ID: STP13901S

    Committee/Subcommittee: E10.07

    DOI: 10.1520/STP13901S


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