Analysis of probability of defects in the disposal canisters

Jan-Erik Holmberg, Pirkko Kuusela

    Research output: Book/ReportReport

    Abstract

    This report presents a probability model for the reliability of the spent nuclear waste final disposal canister. Reliability means here that the welding of the canister lid has no critical defects from the long-term safety point of view. From the reliability point of view, both the reliability of the welding process (that no critical defects will be born) and the non-destructive testing (NDT) process (all critical defects will be detected) are equally important. In the probability model, critical defects in a weld were simplified into a few types. Also the possibility of human errors in the NDT process was taken into account in a simple manner. At this moment there is very little representative data to determine the reliability of welding and also the data on NDT is not well suited for the needs of this study. Therefore calculations presented here are based on expert judgements and on several assumptions that have not been verified yet. The Bayesian probability model shows the importance of the uncertainty in the estimation of the reliability parameters. The effect of uncertainty is that the probability distribution of the number of defective canisters becomes flat for larger numbers of canisters compared to the binomial probability distribution in case of known parameter values. In order to reduce the uncertainty, more information is needed from both the reliability of the welding and NDT processes. It would also be important to analyse the role of human factors in these processes since their role is not reflected in typical test data which is used to estimate “normal process variation”. The reported model should be seen as a tool to quantify the roles of different methods and procedures in the weld inspection process.
    Original languageEnglish
    Place of PublicationOlkiluoto, Eurajoki
    PublisherPosiva
    Number of pages60
    Publication statusPublished - 2011
    MoE publication typeD4 Published development or research report or study

    Publication series

    SeriesPosiva Working Report
    Number2011-36

    Fingerprint

    Defects
    Nondestructive examination
    Welding
    Probability distributions
    Welds
    Human engineering
    Radioactive wastes
    Waste disposal
    Inspection
    Uncertainty

    Keywords

    • Encapsulation and final disposal
    • spent nuclear fuel
    • defect
    • NDT
    • welding
    • probability
    • Bayes

    Cite this

    Holmberg, J-E., & Kuusela, P. (2011). Analysis of probability of defects in the disposal canisters. Olkiluoto, Eurajoki: Posiva. Posiva Working Report, No. 2011-36
    Holmberg, Jan-Erik ; Kuusela, Pirkko. / Analysis of probability of defects in the disposal canisters. Olkiluoto, Eurajoki : Posiva, 2011. 60 p. (Posiva Working Report; No. 2011-36).
    @book{17c5ceab45184ae3916d8b09af3560de,
    title = "Analysis of probability of defects in the disposal canisters",
    abstract = "This report presents a probability model for the reliability of the spent nuclear waste final disposal canister. Reliability means here that the welding of the canister lid has no critical defects from the long-term safety point of view. From the reliability point of view, both the reliability of the welding process (that no critical defects will be born) and the non-destructive testing (NDT) process (all critical defects will be detected) are equally important. In the probability model, critical defects in a weld were simplified into a few types. Also the possibility of human errors in the NDT process was taken into account in a simple manner. At this moment there is very little representative data to determine the reliability of welding and also the data on NDT is not well suited for the needs of this study. Therefore calculations presented here are based on expert judgements and on several assumptions that have not been verified yet. The Bayesian probability model shows the importance of the uncertainty in the estimation of the reliability parameters. The effect of uncertainty is that the probability distribution of the number of defective canisters becomes flat for larger numbers of canisters compared to the binomial probability distribution in case of known parameter values. In order to reduce the uncertainty, more information is needed from both the reliability of the welding and NDT processes. It would also be important to analyse the role of human factors in these processes since their role is not reflected in typical test data which is used to estimate “normal process variation”. The reported model should be seen as a tool to quantify the roles of different methods and procedures in the weld inspection process.",
    keywords = "Encapsulation and final disposal, spent nuclear fuel, defect, NDT, welding, probability, Bayes",
    author = "Jan-Erik Holmberg and Pirkko Kuusela",
    note = "Project code: 74108",
    year = "2011",
    language = "English",
    series = "Posiva Working Report",
    publisher = "Posiva",
    number = "2011-36",
    address = "Finland",

    }

    Holmberg, J-E & Kuusela, P 2011, Analysis of probability of defects in the disposal canisters. Posiva Working Report, no. 2011-36, Posiva, Olkiluoto, Eurajoki.

    Analysis of probability of defects in the disposal canisters. / Holmberg, Jan-Erik; Kuusela, Pirkko.

    Olkiluoto, Eurajoki : Posiva, 2011. 60 p. (Posiva Working Report; No. 2011-36).

    Research output: Book/ReportReport

    TY - BOOK

    T1 - Analysis of probability of defects in the disposal canisters

    AU - Holmberg, Jan-Erik

    AU - Kuusela, Pirkko

    N1 - Project code: 74108

    PY - 2011

    Y1 - 2011

    N2 - This report presents a probability model for the reliability of the spent nuclear waste final disposal canister. Reliability means here that the welding of the canister lid has no critical defects from the long-term safety point of view. From the reliability point of view, both the reliability of the welding process (that no critical defects will be born) and the non-destructive testing (NDT) process (all critical defects will be detected) are equally important. In the probability model, critical defects in a weld were simplified into a few types. Also the possibility of human errors in the NDT process was taken into account in a simple manner. At this moment there is very little representative data to determine the reliability of welding and also the data on NDT is not well suited for the needs of this study. Therefore calculations presented here are based on expert judgements and on several assumptions that have not been verified yet. The Bayesian probability model shows the importance of the uncertainty in the estimation of the reliability parameters. The effect of uncertainty is that the probability distribution of the number of defective canisters becomes flat for larger numbers of canisters compared to the binomial probability distribution in case of known parameter values. In order to reduce the uncertainty, more information is needed from both the reliability of the welding and NDT processes. It would also be important to analyse the role of human factors in these processes since their role is not reflected in typical test data which is used to estimate “normal process variation”. The reported model should be seen as a tool to quantify the roles of different methods and procedures in the weld inspection process.

    AB - This report presents a probability model for the reliability of the spent nuclear waste final disposal canister. Reliability means here that the welding of the canister lid has no critical defects from the long-term safety point of view. From the reliability point of view, both the reliability of the welding process (that no critical defects will be born) and the non-destructive testing (NDT) process (all critical defects will be detected) are equally important. In the probability model, critical defects in a weld were simplified into a few types. Also the possibility of human errors in the NDT process was taken into account in a simple manner. At this moment there is very little representative data to determine the reliability of welding and also the data on NDT is not well suited for the needs of this study. Therefore calculations presented here are based on expert judgements and on several assumptions that have not been verified yet. The Bayesian probability model shows the importance of the uncertainty in the estimation of the reliability parameters. The effect of uncertainty is that the probability distribution of the number of defective canisters becomes flat for larger numbers of canisters compared to the binomial probability distribution in case of known parameter values. In order to reduce the uncertainty, more information is needed from both the reliability of the welding and NDT processes. It would also be important to analyse the role of human factors in these processes since their role is not reflected in typical test data which is used to estimate “normal process variation”. The reported model should be seen as a tool to quantify the roles of different methods and procedures in the weld inspection process.

    KW - Encapsulation and final disposal

    KW - spent nuclear fuel

    KW - defect

    KW - NDT

    KW - welding

    KW - probability

    KW - Bayes

    M3 - Report

    T3 - Posiva Working Report

    BT - Analysis of probability of defects in the disposal canisters

    PB - Posiva

    CY - Olkiluoto, Eurajoki

    ER -

    Holmberg J-E, Kuusela P. Analysis of probability of defects in the disposal canisters. Olkiluoto, Eurajoki: Posiva, 2011. 60 p. (Posiva Working Report; No. 2011-36).