Dynamic containment event tree modelling techniques and uncertainty analysis

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    Abstract

    VTT has developed a probabilistic risk analysis (PRA) model of a generic boiling water reactor nuclear power plant for PRA levels 1 and 2. The model can be used in research, training, education and demonstration. In this report, some refinements to the level 2 (severe accidents) part of the model are described. Particularly, dynamic modelling of timings of depressurization, emergency feedwater system recovery, emergency core cooling system recovery and lower drywell flooding is implemented. Different techniques to model emergency core cooling system recovery time and its effects are presented in a simplified case study. The techniques are evaluated concerning uncertainty analysis. A two-phase method of uncertainty analysis is presented. The purpose is to separate the treatment of aleatoric and epistemic uncertainties, to get rid of certain issues and inconsistencies in more traditional one-phase uncertainty analysis. The method is demonstrated by the emergency core cooling system case study. A drawback of the two-phase uncertainty analysis is that it is computationally very demanding. Therefore, it is proposed that first limited dynamic models would be constructed and analysed by the two-phase procedure; this would give input to a simplified full-scope model, allowing one-phase uncertainty analysis.
    Original languageEnglish
    Place of PublicationEspoo
    PublisherVTT Technical Research Centre of Finland
    Number of pages31
    Publication statusPublished - 4 Jan 2019
    MoE publication typeD4 Published development or research report or study

    Publication series

    SeriesVTT Research Report
    NumberVTT-R-06892-18

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    Keywords

    • probabilistic risk analysis
    • severe accident
    • uncertainty

    Cite this

    Tyrväinen, T., & Karanta, I. (2019). Dynamic containment event tree modelling techniques and uncertainty analysis. VTT Technical Research Centre of Finland. VTT Research Report, No. VTT-R-06892-18