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Tesi etd-05132007-145646


Thesis type
Tesi di dottorato di ricerca
Author
Lombardi Costa, Antonella
URN
etd-05132007-145646
Title
BWR Instability Analysis by Coupled 3D Neutron-Kinetic and Thermal-Hydraulic Codes
Settore scientifico disciplinare
ING-IND/19
Corso di studi
SICUREZZA NUCLEARE E INDUSTRIALE
Commissione
Relatore Prof. Ambrosini, Walter
Relatore Prof. D'Auria, Francesco
Parole chiave
  • PARCS
  • Decay Ratio
  • Coupled Codes
  • BWR instability
  • BWR
  • Peach Bottom
  • Power Oscillation
  • RELAP5
Data inizio appello
15/03/2007;
Consultabilità
completa
Riassunto analitico
The main aim of this thesis is to contribute to the study of the Boiling Water Reactor (BWR) instability phenomena. The RELAP5-MOD3.3 thermal-hydraulic system code and the PARCS-2.4, 3D neutron kinetic code, were coupled to simulate BWR transients. Different algorithms were used to calculate the decay ratio (DR) and the natural frequency (NF) from the power oscillation signals obtained from the transient calculations, as two typical parameters used to provide a quantitative description of instabilities. The validation of a code model set up for the Peach Bottom-2 BWR plant is performed against Low-Flow Stability Tests (LFST). <br>The thesis has the following organisation. Chapter 1 deals with general aspects, starting with the present level of the Light Water Reactor (LWR) development, addressing the specific problem of instability in BWRs and finally analysing the issue of the current tools to investigate the phenomenon. Chapter 2 describes the LFST performed in the Peach Bottom BWR, the perturbations events studied and the methodology adopted to perform them. Chapter 3 presents the codes and the methodology utilized to perform the calculations and the analyses of the events. In Chapter 4, results considering steady state and transient reactor conditions will be presented and discussed. Finally, Chapter 5 describes the obtained conclusions and the contributions of this work to study of BWR stability. <br>
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