STP1170: Sensitivity Analysis of Thermal and Stress Fields in the Core Belt of a Pressurized Water Reactor

    Glumac, B
    Headresearch counselor, University of Ljubljana, “Jozef Stefan” Institute, Ljubljana,

    Najžer, M
    Headresearch counselor, University of Ljubljana, “Jozef Stefan” Institute, Ljubljana,

    Pages: 13    Published: Jan 1993


    Abstract

    Reactor pressure vessel (RPV) steel undergoes significant changes in brittle to ductile transition temperature shift ΔRTNDT when irradiated with fast neutrons leaking from the pressurized water reactor (PWR) core. This means that, according to American Society of Mechanical Engineers (ASME) III-G Code, pressure-temperature limits have to be recalculated periodically. Heatup-cooldown limits require intensive calculations of time-dependent thermal and stress fields, brittle to ductile transition temperature RTNDTdetermination, and so forth, and often with highly scattered material properties data. The error induced by those scattered data is then compensated for with introduction of additional safety factors specified by the ASME code.

    By using sensitivity analysis and performing only moderately complicated calculations, one can not only calculate certain quantities, but also their variance-covariance matrixes, based on a known (either measured or modeled) variance-covariance matrix of input parameters (i.e., material data).

    This contribution deals with an approach to sensitivity analysis of the calculated timedependent temperature [{Ti(t)}, < δTi(t)∣δTi(t) >] and both hoop and thermal stress profiles [{σi(M)(t)}, < δσi(M)(t)∣δσi(M)(t) >] and [{σi(T)(t) < δσi(T)t)∣δσj(T)(t) >] in the core belt of the pressure vessel wall. The contribution only briefly outlines what has to be done to calculate stress intensity factors together with their variance-covariance information, and, on the other hand, determine adjusted RTNDT and reference stress intensity factor KIR together with their variances.

    Keywords:

    pressurized water reactor, pressure-temperature limit curves, neutron embrittlement, nonstationary thermal and stress fields, sensitivity analysis, variance-covariance matrices


    Paper ID: STP24789S

    Committee/Subcommittee: E10.08

    DOI: 10.1520/STP24789S


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