Browsing by Author "Virtanen, Julia"

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  • Quasi-two-dimensional oil droplets in a Hele-Shaw cell
    (2023-06-07) Virtanen, Julia
     Perustieteiden korkeakoulu | Bachelor's thesis
  • Reliability analysis of passive Safety systems: Heat removal dependency on steam generator mass balance.
    (2017-09-25) Virtanen, Julia
     Insinööritieteiden korkeakoulu | Master's thesis
    This master’s thesis is a case study of the reliability of Passive Heat Removal System via Steam Generators in VVER-1200 design. The purpose of the study is to indicate problematic issues related to passive safety systems’ reliability assessment and identify an optimized passive safety system reliability analysis approach. The optimized analysis approach described in this thesis combines probabilistic (Fault Tree analysis) and deterministic (simulation with computer code) methodology features and focuses on the analysis of natural circulation failure. The case study focuses on natural circulation failures caused by deviations in steam generator mass balance, but also other physical phenomena are assessed. The analysis steps synthesized in this thesis, include description of system design and operational modes, definition of system performance failure criteria via Fault Tree analysis, identification and classification of root causing processes, dynamic simulations of nominal case and cases with parameter deviations with APROS (advanced process simulation environment) software, deterministic evaluation of selected parameters, analysis of code model uncertainties and quantitative reliability evaluation. Within the scope of this thesis the analysis of PHRS SG safety system performance dependency of on steam generator mass balance was performed via APROS simulation. Total loss of power supply was selected as an initiating event. The nominal state parameters as well as deviating system parameter configurations were assigned to parameters of interest in the code model. The impact of physical phenomena –related failures on the overall system performance was estimated. The results show, that the steam generator mass balance has an insignificant impact on the risk of failure of the passive heat removal system. Based on the analysis results, proposal for further research was made.