A modal-based reduced-order model of BWR out-of-phase instabilities

J. A. Turso, J. March-Leuba, R. M. Edwards

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


A low-order model of BWR out-of-phase instabilities is developed via modal analysis. The modal point kinetics equations are derived using the fundamental and first harmonic modes of the neutron diffusion equation. Parameter estimation in the frequency domain is used to determine the coefficients of the transfer functions (or differential equations) representing the necessary BWR feedback characteristics. Combined with well-known non-linear reactor kinetics, the resulting simple structure of the model provides physical insight into the mechanisms behind the out-of-phase coupled thermalhydraulic/neutronic BWR instability. This investigation is specifically oriented toward the LaSalle Unit II BWR. An out-of-phase simulation of the LaSalle BWR illustrates the ability of these equations to effectively reproduce the phenomenon.

Original languageEnglish (US)
Pages (from-to)921-934
Number of pages14
JournalAnnals of Nuclear Energy
Issue number12
StatePublished - Aug 1997

All Science Journal Classification (ASJC) codes

  • Nuclear Energy and Engineering


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