Phase Plane Analysis of Nuclear-Coupled Density-Wave Oscillations

  • John C. Lee
  • Anozie Onyemaechi


Due to a tight coupling between thermal-hydraulic and neutronic performance of boiling water reactors (BWRs), there exists the potential for nonlinear limit cycle oscillations in coolant flowrate and core power. Physical understanding of the limit cycle oscillations is of considerable importance for safe and reliable operation of BWRs, especially in regard to anticipated transient without scram (ATWS) events. Although considerable attention1–8 has been given to these potential instability problems, most of the earlier investigations1–3 have focused mainly on frequency-domain linear models for prediction of the instability threshold, assessment of the stability margins, and establishment of the stability boundary. While these linear analyses are intended for use as a design tool to avoid the inception of flow oscillations, they are not capable of predicting the severity of oscillations in an unstable configuration. More recently,6–8 the potential for large-amplitude limit cycle oscillations has been explicitly studied with nonlinear BWR models for linearly unstable operating regimes.


Relaxation Oscillation Fuel Temperature Void Reactivity Limit Cycle Oscillation Nuclear Regulatory Commission 
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Copyright information

© Plenum Press, New York 1989

Authors and Affiliations

  • John C. Lee
    • 1
  • Anozie Onyemaechi
    • 1
  1. 1.Department of Nuclear EngineeringThe University of MichiganAnn ArborUSA

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