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Title: Investigation of rotating mode behavior in BWR out-of-phase limit cycle oscillations – Part 1: Reduced order model

Abstract

Previous neutronic/thermal-hydraulic (TH) coupled numerical simulations using full-core TRACE/PARCS and SIMULATE-3K BWR models have shown evidence of a specific “rotating mode” behavior (steady rotation of the symmetry line, i.e. constant phase shift of approximately 90° between the first two azimuthal modes) in out-of-phase limit cycle oscillations, regardless of initial conditions and even if the first two azimuthal modes have different natural frequencies. This suggests a nonlinear coupling between these modes; otherwise, the phase shift between these modes would change at a constant rate during the limit cycle. The goal of the present work is to gain further insights on the rotating mode behavior using a simplified mathematical model which contains all of the important physics for this application while providing sufficient flexibility and simplicity to allow for in-depth understanding of the underlying phenomena. This was accomplished using a multi-channel, multi-modal reduced-order model, using a modification of the fixed pressure drop boundary condition to simulate channel coupling via the inlet and outlet plena, in order to destabilize the out-of-phase mode over the in-phase mode. Examination of the time-dependent solution of the nonlinear system showed a clear preference for rotating mode behavior in the four-channel model under stand-alone TH conditions and formore » conditions with weak neutronic feedback. Furthermore, when neutronic feedback was strengthened (i.e., larger reactivity feedback coefficients), the side-to-side mode (stationary symmetry line) was favored instead. Additional analyses using higher-fidelity numerical modeling, as well as a physical explanation for the rotating behavior seen in both sets of analyses, will be provided in a companion paper (“Part 2”).« less

Authors:
ORCiD logo [1];  [2];  [2];  [3]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Univ. of Michigan, Ann Arbor, MI (United States)
  3. MRU, Knoxville, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1481708
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Annals of Nuclear Energy (Oxford)
Additional Journal Information:
Journal Name: Annals of Nuclear Energy (Oxford); Journal Volume: 122; Journal Issue: C; Journal ID: ISSN 0306-4549
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
22 GENERAL STUDIES OF NUCLEAR REACTORS; BWR stability; Limit cycle; Rotating mode; Out-of-phase oscillations; Reduced-order model

Citation Formats

Wysocki, Aaron J., Manera, Annalisa, Downar, Thomas, and March-Leuba, Jose. Investigation of rotating mode behavior in BWR out-of-phase limit cycle oscillations – Part 1: Reduced order model. United States: N. p., 2018. Web. doi:10.1016/j.anucene.2018.08.032.
Wysocki, Aaron J., Manera, Annalisa, Downar, Thomas, & March-Leuba, Jose. Investigation of rotating mode behavior in BWR out-of-phase limit cycle oscillations – Part 1: Reduced order model. United States. doi:10.1016/j.anucene.2018.08.032.
Wysocki, Aaron J., Manera, Annalisa, Downar, Thomas, and March-Leuba, Jose. Fri . "Investigation of rotating mode behavior in BWR out-of-phase limit cycle oscillations – Part 1: Reduced order model". United States. doi:10.1016/j.anucene.2018.08.032. https://www.osti.gov/servlets/purl/1481708.
@article{osti_1481708,
title = {Investigation of rotating mode behavior in BWR out-of-phase limit cycle oscillations – Part 1: Reduced order model},
author = {Wysocki, Aaron J. and Manera, Annalisa and Downar, Thomas and March-Leuba, Jose},
abstractNote = {Previous neutronic/thermal-hydraulic (TH) coupled numerical simulations using full-core TRACE/PARCS and SIMULATE-3K BWR models have shown evidence of a specific “rotating mode” behavior (steady rotation of the symmetry line, i.e. constant phase shift of approximately 90° between the first two azimuthal modes) in out-of-phase limit cycle oscillations, regardless of initial conditions and even if the first two azimuthal modes have different natural frequencies. This suggests a nonlinear coupling between these modes; otherwise, the phase shift between these modes would change at a constant rate during the limit cycle. The goal of the present work is to gain further insights on the rotating mode behavior using a simplified mathematical model which contains all of the important physics for this application while providing sufficient flexibility and simplicity to allow for in-depth understanding of the underlying phenomena. This was accomplished using a multi-channel, multi-modal reduced-order model, using a modification of the fixed pressure drop boundary condition to simulate channel coupling via the inlet and outlet plena, in order to destabilize the out-of-phase mode over the in-phase mode. Examination of the time-dependent solution of the nonlinear system showed a clear preference for rotating mode behavior in the four-channel model under stand-alone TH conditions and for conditions with weak neutronic feedback. Furthermore, when neutronic feedback was strengthened (i.e., larger reactivity feedback coefficients), the side-to-side mode (stationary symmetry line) was favored instead. Additional analyses using higher-fidelity numerical modeling, as well as a physical explanation for the rotating behavior seen in both sets of analyses, will be provided in a companion paper (“Part 2”).},
doi = {10.1016/j.anucene.2018.08.032},
journal = {Annals of Nuclear Energy (Oxford)},
number = C,
volume = 122,
place = {United States},
year = {2018},
month = {9}
}

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