A practical formula for inferring eigenvalue separation from flux tilt measurements in nuclear reactors

Hashimoto, Kazuo; Ohsawa, Takaaki; Miki, Ryota; Shibata, Toshikazu

doi:10.1016/0306-4549(91)90048-3

Cited by 21 publications

(5 citation statements)

References 7 publications

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“…Using Hashimoto's formulae (13) in consideration of up to the first order term, the perturbed neutron flux is described as follows: (1) where p': Perturbed neutron flux p : Unperturbed neutron flux m n: Inverse of the nth lambda-mode eigenvalue m0…”

Section: Application Of the Ehp Methods To An Axially Decoupled Corementioning

confidence: 99%

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Measurement of Flux Tilt and Eigenvalue Separation in Axially Decoupled Core.

Andoh

Misawa

Nishina

et al. 1997

J. Nucl. Sci. Technol.

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A study on the nuclear characteristics of an axially decoupled core was performed through a series of experiments using the solid moderator core in the Kyoto University Critical Assembly (KUCA). In the axially decoupled core which has an internal blanket between the upper and lower cores, the measured differential reactivity worth of a control rod moving axially was apparently asymmetric between the two core regions. Since it was considered that this phenomenon was attributed to the neutron flux tilt caused by the axial movement of control rods during the measurement of differential worth, the axial reaction rate distributions were measured by gold wires with and without a cadmium tube. It was found that the reaction rate distribution was remarkably tilted by changing the pattern of control rods inserted in the core to maintain the critical state, and that the flux distribution was tilted without energy dependency. The value of first-order eigenvalue separation was obtained using the relation between the neutron flux tilt and the first-mode eigenvalue separation based on the Explicit Higher-order Perturbation (EHP) method. This value agreed with the calculated result by the SRAC system.

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Section: Application Of the Ehp Methods To An Axially Decoupled Corementioning

confidence: 99%

“…The method used in Ref. (13) was to multiply the left of Eq. (1) by the production operator M and adjoint eigenfunction p+n.…”

Section: Application Of the Ehp Methods To An Axially Decoupled Corementioning

confidence: 99%

Measurement of Flux Tilt and Eigenvalue Separation in Axially Decoupled Core.

Andoh

Misawa

Nishina

et al. 1997

J. Nucl. Sci. Technol.

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“…In the KUCA B-core experiment, 14) which is a polyethylene solid-moderated core, it has been shown that the change in the neutron flux distribution is independent of neutron energy, by measuring reaction rate distributions of gold and Cd-covered wires activated. However, in not only the KUCA B-core experiment but also other ones, 1,[16][17][18][19][20][21] theoretical formulation of the relationship utilized is derived from the Explicit Higher-Order perturbation method (the EHP method) 15) with one-energy-group approximation.…”

Section: Introductionmentioning

confidence: 99%

“…Withdrawal of the 3-rd and 4-th fuel plates of the fuel Case 3 4 frames [08] and [09] from the opposite side to the core gap, respectively. Withdrawal of the 1-st and 2-nd fuel plates of the fuel frame Case 4 4[09] from the opposite side to the core gap and of the 1-st and 2-nd fuel plates of fuel frame[19] from the closer side to the core gap. [ ]: Name of fuel frame shown inFig.…”

mentioning

confidence: 99%

Experiments and Analyses for Relationship between Flux Tilt in Two-Energy-Group Model and First-Mode Eigenvalue Separation

Pyeon

Misawa

Unesaki

et al. 2004

Journal of Nuclear Science and Technology

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For a relationship between the flux tilt in two-energy-group model and the first-mode eigenvalue separation, it was found that the flux tilt in two-energy-group model is proportional to the perturbed reactivity and inversely proportional to the first-mode eigenvalue separation on the basis of the Modified Explicit Higher Order Perturbation method with two-energy-group approximation, by taking account of only the first-order perturbation and the first-mode expansion approximations. As a result, one could obtain the same formulation of the flux tilt in one-energy-group model based on a conventional higher-order perturbation theory with one-energy-group approximation. To show the validity of this relationship, flux tilt experiments were carried out by using a coupled-core at the Kyoto University Critical Assembly, and analyses of the experiments were performed for inferring the first-mode eigenvalue separation from both the perturbed reactivity and the degree of flux tilt induced by a perturbation. Through the comparison between the analyses and the experiments, the validity of the relationship derived was demonstrated, and it was concluded that the flux tilt is independent of the neutron energy.

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“…In a two-core reactor such as UTR-KINKI, the first-harmonic azimuthal mode dominantly excited has the zero between the two cores, 7) and hence, the neutron detector for the rod drop method and the neutron source are usually placed between the cores to reduce the influence of the mode. Further modes higher than the first are scarcely excited.…”

Section: Extended Extrapolation Techniquementioning

confidence: 99%

An Extended Rod Drop Method Applicable to Subcritical Reactor System Driven by Neutron Source

Taninaka

Hashimoto

Ohsawa

2010

J. Nucl. Sci. Technol.

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Control rod drop method based on the integral count technique and the extrapolation one was extended to apply to a subcritical reactor system driven by a neutron source. Similarly to the conventional method, the extended method is capable of rapid estimation of rod reactivity worth and is essential from the educational viewpoint. For the demonstration of the applicability, a series of rod drop experiments was carried out in subcritical and critical states of a reactor system, and rod reactivity worth and effective neutron source strength were determined from the counting data of a neutron detector. In addition, the time-sequence count data were acquired and the least-squares inverse kinetics analysis was made to justify the present extended method. The rod worth and source strength obtained by the present method were consistent with those obtained by the least-squares inverse kinetics method.

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A practical formula for inferring eigenvalue separation from flux tilt measurements in nuclear reactors

Cited by 21 publications

References 7 publications

Measurement of Flux Tilt and Eigenvalue Separation in Axially Decoupled Core.

Measurement of Flux Tilt and Eigenvalue Separation in Axially Decoupled Core.

Experiments and Analyses for Relationship between Flux Tilt in Two-Energy-Group Model and First-Mode Eigenvalue Separation

An Extended Rod Drop Method Applicable to Subcritical Reactor System Driven by Neutron Source

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