Material integrity of welded copper overpack: Annual report 2014

    Research output: Book/ReportReport

    Abstract

    The research programme on the creep issues of the nuclear waste disposal canister copper material has continued with long-running uniaxial and multiaxial experiments as well as relaxation testing to support the material modelling activities, which produce appropriate material models to be used in the FE analysis, which will be used to assess the stresses and strains in the critical locations of the canister. The relaxation testing is ongoing and it has proven necessary to use a servo-mechanical testing machine in order to generate good quality test data. The initial FE prediction of strain rates calculated by the LCSP creep model and a relaxation model suggests a clear difference, but this needs to be verified after a better relaxation model is defined based on much more data. The most important result of this year has been the observation of cracking in the oxide particle zone at the friction stir weld root in the longest running CT test, which was terminated after 50 000 hours for sectioning and metallographic investigations. The oxide particles have nucleated creep cavities which have eventually lead to cracking of the oxide particle zone in spite of the low stress state 8 mm ahead of the notch tip. This observation is in line with the earlier results from uniaxial creep tests with a radial sample from the weld root. The weakness only manifests itself in long-term testing because the cavity nucleation and growth process is a slow process. Because of the low strength of the oxide particle zone welding in air should be avoided and vacuum or inert gas should be used instead.
    Original languageEnglish
    PublisherVTT Technical Research Centre of Finland
    Number of pages17
    Publication statusPublished - 2015
    MoE publication typeD4 Published development or research report or study

    Publication series

    SeriesVTT Research Report
    VolumeVTT-R-00773-15

    Fingerprint

    integrity
    copper
    cans
    oxides
    waste disposal
    creep tests
    cavities
    radioactive wastes
    notches
    test equipment
    welding
    strain rate
    rare gases
    friction
    nucleation
    vacuum
    air
    predictions
    gases

    Keywords

    • creep
    • corrosion
    • copper
    • repository
    • life

    Cite this

    Rantala, J., Auerkari, P., Laukkanen, A., Andersson, T., & Saukkonen, T. (2015). Material integrity of welded copper overpack: Annual report 2014. VTT Technical Research Centre of Finland. VTT Research Report, Vol.. VTT-R-00773-15
    Rantala, Juhani ; Auerkari, Pertti ; Laukkanen, Anssi ; Andersson, Tom ; Saukkonen, Tapio. / Material integrity of welded copper overpack : Annual report 2014. VTT Technical Research Centre of Finland, 2015. 17 p. (VTT Research Report, Vol. VTT-R-00773-15).
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    title = "Material integrity of welded copper overpack: Annual report 2014",
    abstract = "The research programme on the creep issues of the nuclear waste disposal canister copper material has continued with long-running uniaxial and multiaxial experiments as well as relaxation testing to support the material modelling activities, which produce appropriate material models to be used in the FE analysis, which will be used to assess the stresses and strains in the critical locations of the canister. The relaxation testing is ongoing and it has proven necessary to use a servo-mechanical testing machine in order to generate good quality test data. The initial FE prediction of strain rates calculated by the LCSP creep model and a relaxation model suggests a clear difference, but this needs to be verified after a better relaxation model is defined based on much more data. The most important result of this year has been the observation of cracking in the oxide particle zone at the friction stir weld root in the longest running CT test, which was terminated after 50 000 hours for sectioning and metallographic investigations. The oxide particles have nucleated creep cavities which have eventually lead to cracking of the oxide particle zone in spite of the low stress state 8 mm ahead of the notch tip. This observation is in line with the earlier results from uniaxial creep tests with a radial sample from the weld root. The weakness only manifests itself in long-term testing because the cavity nucleation and growth process is a slow process. Because of the low strength of the oxide particle zone welding in air should be avoided and vacuum or inert gas should be used instead.",
    keywords = "creep, corrosion, copper, repository, life",
    author = "Juhani Rantala and Pertti Auerkari and Anssi Laukkanen and Tom Andersson and Tapio Saukkonen",
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    Rantala, J, Auerkari, P, Laukkanen, A, Andersson, T & Saukkonen, T 2015, Material integrity of welded copper overpack: Annual report 2014. VTT Research Report, vol. VTT-R-00773-15, VTT Technical Research Centre of Finland.

    Material integrity of welded copper overpack : Annual report 2014. / Rantala, Juhani; Auerkari, Pertti; Laukkanen, Anssi; Andersson, Tom; Saukkonen, Tapio.

    VTT Technical Research Centre of Finland, 2015. 17 p. (VTT Research Report, Vol. VTT-R-00773-15).

    Research output: Book/ReportReport

    TY - BOOK

    T1 - Material integrity of welded copper overpack

    T2 - Annual report 2014

    AU - Rantala, Juhani

    AU - Auerkari, Pertti

    AU - Laukkanen, Anssi

    AU - Andersson, Tom

    AU - Saukkonen, Tapio

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    N2 - The research programme on the creep issues of the nuclear waste disposal canister copper material has continued with long-running uniaxial and multiaxial experiments as well as relaxation testing to support the material modelling activities, which produce appropriate material models to be used in the FE analysis, which will be used to assess the stresses and strains in the critical locations of the canister. The relaxation testing is ongoing and it has proven necessary to use a servo-mechanical testing machine in order to generate good quality test data. The initial FE prediction of strain rates calculated by the LCSP creep model and a relaxation model suggests a clear difference, but this needs to be verified after a better relaxation model is defined based on much more data. The most important result of this year has been the observation of cracking in the oxide particle zone at the friction stir weld root in the longest running CT test, which was terminated after 50 000 hours for sectioning and metallographic investigations. The oxide particles have nucleated creep cavities which have eventually lead to cracking of the oxide particle zone in spite of the low stress state 8 mm ahead of the notch tip. This observation is in line with the earlier results from uniaxial creep tests with a radial sample from the weld root. The weakness only manifests itself in long-term testing because the cavity nucleation and growth process is a slow process. Because of the low strength of the oxide particle zone welding in air should be avoided and vacuum or inert gas should be used instead.

    AB - The research programme on the creep issues of the nuclear waste disposal canister copper material has continued with long-running uniaxial and multiaxial experiments as well as relaxation testing to support the material modelling activities, which produce appropriate material models to be used in the FE analysis, which will be used to assess the stresses and strains in the critical locations of the canister. The relaxation testing is ongoing and it has proven necessary to use a servo-mechanical testing machine in order to generate good quality test data. The initial FE prediction of strain rates calculated by the LCSP creep model and a relaxation model suggests a clear difference, but this needs to be verified after a better relaxation model is defined based on much more data. The most important result of this year has been the observation of cracking in the oxide particle zone at the friction stir weld root in the longest running CT test, which was terminated after 50 000 hours for sectioning and metallographic investigations. The oxide particles have nucleated creep cavities which have eventually lead to cracking of the oxide particle zone in spite of the low stress state 8 mm ahead of the notch tip. This observation is in line with the earlier results from uniaxial creep tests with a radial sample from the weld root. The weakness only manifests itself in long-term testing because the cavity nucleation and growth process is a slow process. Because of the low strength of the oxide particle zone welding in air should be avoided and vacuum or inert gas should be used instead.

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    Rantala J, Auerkari P, Laukkanen A, Andersson T, Saukkonen T. Material integrity of welded copper overpack: Annual report 2014. VTT Technical Research Centre of Finland, 2015. 17 p. (VTT Research Report, Vol. VTT-R-00773-15).