A Mechanism for Out-of-Phase Power Instabilities in Boiling Water Reactors

March-Leuba, J.; Blakeman, E.D.

doi:10.13182/nse91-a15730

Cited by 113 publications

(32 citation statements)

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“…Higher harmonics in the azimuthal mode are associated with the regional stability (15). Since regional instability was observed in the KKK BOC-9 core, the higher harmonics analysis was performed using the HARMO code.…”

Section: Higher Harmonics Analysismentioning

confidence: 99%

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Analysis of Core Stability Measurement Data of Advanced 9*9 Fuel Assembly in a BWR Core.

Tsuda¹,

Itami²,

Kubo³

et al. 1997

J. Nucl. Sci. Technol.

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The core stability measurements were taken during the cycle-9 startup of the 1,300MWe BWR, Kernkraftwerk Kruemmel (KKK). The core contained advanced 9x9 type high burn-up design reload fuel with a higher enrichment than current 8x8 fuel. A design feature of the advanced 9x9 fuel assembly (FA) is a large square water channel for enhanced neutron moderation. The measurement data as a function of core flow and power showed almost the same stability characteristics as those of the past measurement during the cycle-3 startup of the KKK core with the 8x8 FA. The local power range monitors (LPRM) detected neutron flux oscillations in both core-wide in-phase and half-core out-of-phase modes.The frequency-domain stability analysis using the STAIF-PK code well reproduced the measurement result that the onset of unstable operation in KKK first occurs when about half of the reactor internal pumps are operating and the other half are stopped. The stability performance of the advanced 9x9 FA in the core was compared with the 8x8 FA by a design parameter analysis with respect to thermal-hydraulic and neutronic design. It has been demonstrated by the analysis that the stability performance of the advanced 9x9 FA is comparable with current 8x8 FA.

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Section: Higher Harmonics Analysismentioning

confidence: 99%

“…Regional Stability Analysis Method The regional stability analysis method in frequencydomain has been proposed by March-Leuba et al (15) This method has been implemented into the STAIF-PK code. The following describes the basis of this method.…”

Section: Frequency-domainmentioning

confidence: 99%

Analysis of Core Stability Measurement Data of Advanced 9*9 Fuel Assembly in a BWR Core.

Tsuda¹,

Itami²,

Kubo³

et al. 1997

J. Nucl. Sci. Technol.

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“…For this reason, xenon induced spatial power instabilities have been analyzed for most of the reactor types, including Boiling Water Reactors [12,13], Heavy Water Reactors [14], High Temper ature Gas Cooled Reactors [15], and the Russian design VVER and RBMK reactors [16]. Among these studies, the PWR is the most commonly used reactor type.…”

Section: Chapter 2 Control Of Spatial Xenon Oscillationsmentioning

confidence: 99%

Knowledge base expert system control of spatial xenon oscillations in pressurized water reactors

Alten

Danofsky

1993

Annals of Nuclear Energy

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“…Normally, these subcritical modes would be damped out because the eigenvalues of these modes are less than one. However, when these subcritical flux modes are coupled with parallel-channel oscillations, sustained power oscillations can be realized [14] [15].…”

Section: Modes Of Bwr Instabilitiesmentioning

confidence: 99%

“…From the one-group diffusion theory, the eigenvalue of a harmonic mode can be expressed as [21] These eigenvalues are less than one except for the fundamental mode which is equal to one for steady-state conditions. The reactivity separation between fundamental and subcritical modes can be expressed as [14] B . A small subcritical reactivity means less damping of the subcritical mode.…”

Section: Dependence Of Stability On Changes In Operating Variablesmentioning

confidence: 99%

Predictive Methods for Stability Margin in BWR

Román¹

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iii This dissertation is dedicated to my mother, wherever she is now, who always gave me encouragement, love and support, my father raised me with infinite patience and advised me to obtain a degree in physics, my sister Pilar, example to follow both in the study and teaching and, especially my family, because this work has been done during the time I had to spend with my wife Marina, and my children Cecilia and Jose Andrés.I also want to thank my supervisors, Alberto Escrivá and José Luis Muñoz-Cobo without them this thesis would not have been possible. I also thank this work to José María Izquierdo Rocha who taught me to be rigorous and convinced me of the need for a thorough knowledge of nuclear engineering. To all my colleagues who have made me what I am today.Thanks to all v SUMMARY Power and flow oscillations in a BWR are very undesirable. One of the major concerns is to ensure, during power oscillations, compliance with GDC 10 and 12. GDC 10 requires that the reactor core be designed with appropriate margin to assure that specified acceptable fuel design limits will not be exceeded during any condition of normal operation, including the effects of anticipated operational occurrences. GDC 12 requires assurance that power oscillations which can result in conditions exceeding specified acceptable fuel design limits are either not possible or can be reliably and readily detected and suppressed.If the oscillation amplitude is large, before the scram occurs the fuel rods may experience periodic dry-out and rewetting, or if the oscillation is larger enough, extended dry-out.The Decay Ratio (DR) is the typical linear stability figure of merit. For analytical estimation of DR frequency domain codes are very useful. These types of codes are very fast and their results are very robust in comparison with time domain codes, whose results may be dependent on numeric scheme and nodalization. The only drawback of frequency domain is that you are limited to the linear domain; however, because of regulatory requirements imposed by GDC-12, reactors must remain stable and, thus, reactors always operate in the linear domain.LAPUR is a frequency domain stability code that contains a mathematical description of the core of a boiling water reactor. It solves the steady state governing equations for the coolant and fuel, and the dynamic equations for the coolant, fuel and the neutron field in the frequency domain. Several improvements have been performed to the current version of the code, LAPUR5, in order to upgrade it for use with new fuel design types. The channel geometry has been changed from constant area to variable area. The local losses due to the spacers and contractions along the flow path have been upgraded to use industry standard correlations. This new version is LAPUR 6.In this work, in order to check the correct implementation of these changes, a two-fold LAPUR 6 validation has been performed: vi First, an exhaustive validation of the models implemented has been performed, comparing single channels LAPUR 6 outputs...

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A Mechanism for Out-of-Phase Power Instabilities in Boiling Water Reactors

Cited by 113 publications

References 1 publication

Analysis of Core Stability Measurement Data of Advanced 9*9 Fuel Assembly in a BWR Core.

Analysis of Core Stability Measurement Data of Advanced 9*9 Fuel Assembly in a BWR Core.

Knowledge base expert system control of spatial xenon oscillations in pressurized water reactors

Predictive Methods for Stability Margin in BWR

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