@article{46eba00d79504f3ba8ed7fdaaab61ef0,

title = "A modal-based reduced-order model of BWR out-of-phase instabilities",

abstract = "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.",

author = "Turso, {J. A.} and J. March-Leuba and Edwards, {R. M.}",

note = "Funding Information: A three dimensional representation of a fully developed OOPS oscillation, for several points during one cycle (approx. 2.5 s), is presented in Fig. 4 . Fig. 5 Fig. 6 present the individual contributions of each mode in three dimensions. As shown in Fig. 5 the first harmonic oscillates at the same frequency as the total oscillation, which is essentially a combination of the fundamental and first harmonic modes, approx. 0.4 Hz. The fundamental mode ( Fig. 6 ) oscillates at exactly twice the frequency of the OOP oscillation. The APRM power spectrum presented above [ Fig. 3 (b)] shows the same fundamental frequency of oscillation i.e. 0.8 Hz. Thus, the APRM signal during an out-of-phase oscillation appears to be a direct indication of the fundamental mode component. This is verified by examination of Fig. 2 (b), the APRM signal during the OOP oscillation, and Fig. 1 (b), the contribution of the fundamental mode from 300 to 310 s. To obtain an indication of the behavior of the first harmonic during an actual OOP event, one would simply subtract the APRM signal from the representative LPRM signal. This conclusion could only have been obtained via a dynamic low-order modal analysis of an OOP oscillation. Larger, three-dimensional nodal analysis codes typically do not present the essential physics of the process in a manner necessary to draw such a conclusion. The results above present remarkable correspondence between actual observed OOP oscillations and those obtained with the low-order phenomenological model. The work presented in this paper was supported by the National Science Foundation (NSF/ECS-916504) and the Electric Power Research Institute (EPRI-RP8030-04). Copyright: Copyright 2017 Elsevier B.V., All rights reserved.",

year = "1997",

month = aug,

doi = "10.1016/S0306-4549(96)00069-2",

language = "English (US)",

volume = "24",

pages = "921--934",

journal = "Annals of Nuclear Energy",

issn = "0306-4549",

publisher = "Elsevier Limited",

number = "12",

}