STP1475: Assessment of Neutron Irradiation-Induced Grain Boundary Embrittlement by Phosphorous Segregation in a Reactor Pressure Vessel Steel

    Kimura, A
    ProfessorGraduate StudentResearch Associate, Institute of Advanced Energy, Kyoto University, Kyoto,

    Shibata, M
    ProfessorGraduate StudentResearch Associate, Institute of Advanced Energy, Kyoto University, Kyoto,

    Kasada, R
    ProfessorGraduate StudentResearch Associate, Institute of Advanced Energy, Kyoto University, Kyoto,

    Fujii, K
    Senior Researcher, Institute of Nuclear Safety System, Inc., Fukui,

    Fukuya, K
    Senior Researcher, Institute of Nuclear Safety System, Inc., Fukui,

    Nakata, H
    Senior Researcher, Institute of Nuclear Safety System, Inc., Fukui,

    Pages: 13    Published: Jan 2006


    Abstract

    The materials used were two sorts of reactor pressure vessel steels (RPVSs), which contain different amounts of impurity phosphorous (P) and copper (Cu). The specimens for Charpy V-notch impact tests and Auger electron spectroscopy (AES) were irradiated in the Japan Materials Test Reactor (JMTR) at 290°C up to fluences of 6 × 1021 and 1 × 1024 n/m2 using a multi-division temperature control capsule which enables removal of a part of the sub-capsules during operation of the reactor.

    Neutron irradiation resulted in a significant shift in the ductile-brittle transition temperature (DBTT) accompanied by a large irradiation hardening in the high P and high Cu steel. The AES measurements following the irradiations revealed that almost no phosphorous segregation occurred at grain boundaries. The DBTT shifts by neutron irradiation were reasonably interpreted in terms of a so-called hardening mechanism. The SEM observations of the fractured surface indicated that a very small amount of grain boundary fracture was induced at the irradiation conditions, and resultantly no grain boundary embrittlement was observed.

    Based on the results of irradiation experiments as well as long-term thermal aging experiments beyond 16 000 h, neutron irradiation-induced grain boundary embrittlement is considered to rarely happen to the RPVS that contains 110 wppm of phosphorous.

    Keywords:

    grain boundary fracture ratio, DBTT shift, phosphorous segregation, non-hardening embrittlement


    Paper ID: STP37579S

    Committee/Subcommittee: E10.02

    DOI: 10.1520/STP37579S


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