Modelling design basis accidents LOCA and RIA from the perspective of single fuel rods: Dissertation

    Research output: ThesisDissertationCollection of Articles


    When designing a nuclear power plant and its fuel, certain accidents are postulated to occur with a predetermined low frequency. The consequences of these accidents are mitigated by various passive and active safety features, and an adequate safety level is implemented by the regulatory authority in the safety requirements.
    The dissertation considers computational modelling of two main design basis accidents in current light water reactors: loss-of-coolant accident (abbreviated LOCA) and reactivity initiated accident (RIA). The applied computer programmes are designed for modelling the behaviour of a single fuel rod in transient and accident conditions.
    LOCA modelling is focused on developing a statistical analysis methodology for the evaluation of fuel failures in LOCA. The statistical system is applied to a large break LOCA in an EPR type reactor, and fulfilment of the regulations included in the Regulatory Guides on nuclear safety set by the Finnish nuclear safety authority STUK is studied. In order to determine the underlyingfactors affecting the fuel rod failures, a sensitivity analysis is performed. A systematic multistage procedure is developed for the sensitivity analysis.
    RIA modelling focuses on adaptation of the single rod RIA modelling code SCANAIR for boiling water reactor (BWR) conditions. The SCANAIR code, developed by the French research organisation Institut de Radioprotection et de Sûreté Nucléaire (IRSN), is specifically designed for modelling RIAs in pressurized water reactors (PWRs). In this dissertation, the code is adapted totake into account BWR specific properties and conditions.
    Original languageEnglish
    QualificationDoctor Degree
    Awarding Institution
    • Aalto University
    • Tuomisto, Filip, Supervisor, External person
    • Hämäläinen, Anitta, Advisor
    Award date8 Mar 2018
    Place of PublicationHelsinki
    Print ISBNs978-952-60-7846-5, 978-951-38-8617-2
    Electronic ISBNs978-952-60-7847-2, 978-951-38-8616-5
    Publication statusPublished - 2018
    MoE publication typeG5 Doctoral dissertation (article)


    • loss-of-coolant accident
    • reactivity initiated accident
    • fuel rod modelling


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