On welding residual stresses in structural integrity analyses of NPP components

    Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientific

    Abstract

    It is typically assumed that weld residual stresses (WRSs) in the pipings of nuclear power plants (NPPs) are confined to the weld region and its immediate vicinity and have locally relatively high values, of the order of tensile yield stress in and near the inner surface. In many cases the welds have not been post weld heat treated, and thermal relaxation of the WRS levels is small due to the relatively modest operational temperatures. Therefore, the WRSs in NPPs can potentially affect the structural integrity through the risk of stress corrosion cracking (SCC). In this study the WRS assumptions of commonly used fitness-for-service procedures are compared for a set of representative NPP pipe sizes. Also, the behaviour of WRSs as a function of typical load transients, corresponding to several years of plant operation, is simulated with finite element analysis (FEA) for a nozzle connected to a safe-end and pipe. Finally, from the results of the computational analyses, conclusions and recommendations are given on the application of WRS assumptions.
    Original languageEnglish
    Title of host publicationBaltica VIII
    Subtitle of host publicationLife Management and Maintenance for Power Plants
    Place of PublicationEspoo
    PublisherVTT Technical Research Centre of Finland
    Pages126-150
    Volume1
    ISBN (Electronic)978-951-38-7592-3
    ISBN (Print)978-951-38-7591-6
    Publication statusPublished - 2010
    MoE publication typeB3 Non-refereed article in conference proceedings
    EventBALTICA VIII - International Conference on Life Management and Maintenance for Power Plants - Helsinki-Stockholm, Finland
    Duration: 18 May 201020 May 2010

    Publication series

    SeriesVTT Symposium
    Number264
    ISSN0357-9387

    Conference

    ConferenceBALTICA VIII - International Conference on Life Management and Maintenance for Power Plants
    CountryFinland
    CityHelsinki-Stockholm
    Period18/05/1020/05/10

    Fingerprint

    Structural integrity
    Nuclear power plants
    Residual stresses
    Welding
    Welds
    Pipe
    Stress corrosion cracking
    Yield stress
    Loads (forces)
    Nozzles
    Finite element method

    Cite this

    Cronvall, O. (2010). On welding residual stresses in structural integrity analyses of NPP components. In Baltica VIII: Life Management and Maintenance for Power Plants (Vol. 1, pp. 126-150). Espoo: VTT Technical Research Centre of Finland. VTT Symposium, No. 264
    Cronvall, Otso. / On welding residual stresses in structural integrity analyses of NPP components. Baltica VIII: Life Management and Maintenance for Power Plants. Vol. 1 Espoo : VTT Technical Research Centre of Finland, 2010. pp. 126-150 (VTT Symposium; No. 264).
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    title = "On welding residual stresses in structural integrity analyses of NPP components",
    abstract = "It is typically assumed that weld residual stresses (WRSs) in the pipings of nuclear power plants (NPPs) are confined to the weld region and its immediate vicinity and have locally relatively high values, of the order of tensile yield stress in and near the inner surface. In many cases the welds have not been post weld heat treated, and thermal relaxation of the WRS levels is small due to the relatively modest operational temperatures. Therefore, the WRSs in NPPs can potentially affect the structural integrity through the risk of stress corrosion cracking (SCC). In this study the WRS assumptions of commonly used fitness-for-service procedures are compared for a set of representative NPP pipe sizes. Also, the behaviour of WRSs as a function of typical load transients, corresponding to several years of plant operation, is simulated with finite element analysis (FEA) for a nozzle connected to a safe-end and pipe. Finally, from the results of the computational analyses, conclusions and recommendations are given on the application of WRS assumptions.",
    author = "Otso Cronvall",
    year = "2010",
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    Cronvall, O 2010, On welding residual stresses in structural integrity analyses of NPP components. in Baltica VIII: Life Management and Maintenance for Power Plants. vol. 1, VTT Technical Research Centre of Finland, Espoo, VTT Symposium, no. 264, pp. 126-150, BALTICA VIII - International Conference on Life Management and Maintenance for Power Plants, Helsinki-Stockholm, Finland, 18/05/10.

    On welding residual stresses in structural integrity analyses of NPP components. / Cronvall, Otso.

    Baltica VIII: Life Management and Maintenance for Power Plants. Vol. 1 Espoo : VTT Technical Research Centre of Finland, 2010. p. 126-150 (VTT Symposium; No. 264).

    Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientific

    TY - GEN

    T1 - On welding residual stresses in structural integrity analyses of NPP components

    AU - Cronvall, Otso

    PY - 2010

    Y1 - 2010

    N2 - It is typically assumed that weld residual stresses (WRSs) in the pipings of nuclear power plants (NPPs) are confined to the weld region and its immediate vicinity and have locally relatively high values, of the order of tensile yield stress in and near the inner surface. In many cases the welds have not been post weld heat treated, and thermal relaxation of the WRS levels is small due to the relatively modest operational temperatures. Therefore, the WRSs in NPPs can potentially affect the structural integrity through the risk of stress corrosion cracking (SCC). In this study the WRS assumptions of commonly used fitness-for-service procedures are compared for a set of representative NPP pipe sizes. Also, the behaviour of WRSs as a function of typical load transients, corresponding to several years of plant operation, is simulated with finite element analysis (FEA) for a nozzle connected to a safe-end and pipe. Finally, from the results of the computational analyses, conclusions and recommendations are given on the application of WRS assumptions.

    AB - It is typically assumed that weld residual stresses (WRSs) in the pipings of nuclear power plants (NPPs) are confined to the weld region and its immediate vicinity and have locally relatively high values, of the order of tensile yield stress in and near the inner surface. In many cases the welds have not been post weld heat treated, and thermal relaxation of the WRS levels is small due to the relatively modest operational temperatures. Therefore, the WRSs in NPPs can potentially affect the structural integrity through the risk of stress corrosion cracking (SCC). In this study the WRS assumptions of commonly used fitness-for-service procedures are compared for a set of representative NPP pipe sizes. Also, the behaviour of WRSs as a function of typical load transients, corresponding to several years of plant operation, is simulated with finite element analysis (FEA) for a nozzle connected to a safe-end and pipe. Finally, from the results of the computational analyses, conclusions and recommendations are given on the application of WRS assumptions.

    M3 - Conference article in proceedings

    SN - 978-951-38-7591-6

    VL - 1

    T3 - VTT Symposium

    SP - 126

    EP - 150

    BT - Baltica VIII

    PB - VTT Technical Research Centre of Finland

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    Cronvall O. On welding residual stresses in structural integrity analyses of NPP components. In Baltica VIII: Life Management and Maintenance for Power Plants. Vol. 1. Espoo: VTT Technical Research Centre of Finland. 2010. p. 126-150. (VTT Symposium; No. 264).