■Faculty | Atomic Energy Research Institute |

■Position | Professor |

■Degree | |

■Commentator Guide | https://www.kindai.ac.jp/meikan/258-hashimoto-kengo.html |

■URL | |

Last Updated :2020/09/01

- - 1989 , Nagoya University
- - 1989 , Nagoya University, Graduate School of Engineering
- - 1980 , Nagoya University, School of Engineering
- - 1980 , Nagoya University, School of Engineering

- 1981 , - 1984 , Japan Atomic Energy Research Institute, Research Scientist

- Energy, Nuclear engineering

- Nuclear Power Science

- Measurements and Analysis of Neutron Flux Distribution in UTR-KINKI, J.Nucl.Sci.Technol., J.Nucl.Sci.Technol., 40(5), 349 - 355, May 2003
- Measurement of Subcritical Reactivity in Unsteady State with Digital Time-Series Data Acquisition System Using Difference Filter Technique, IEEE Trans.Nucl.Sci., IEEE Trans.Nucl.Sci., 49(5), 2508 - 2512, Oct. 2002
- Measurement of varying sub-critical reactivity with digital time-series data acquisition system using difference filter technique, G Wakabayashi, Y Yonemura, H Heguri, M Matoba, K Hashimoto, T Horiguchi, 2001 IEEE NUCLEAR SCIENCE SYMPOSIUM, CONFERENCE RECORDS, VOLS 1-4, 2001 IEEE NUCLEAR SCIENCE SYMPOSIUM, CONFERENCE RECORDS, VOLS 1-4, 1, 403 - 405, 2002 Summary:Digital Time-Series Data Acquisition System has been developed for the monitoring of sub-critical reactivity. The system registers arriving time of the signal from a neutron detector as digital data in a FIFO (First In First Out) memory module, and the time data is read and stored by PC (Personal Computer). This system can measure time series data more efficiently than conventional Multi Channel Scaler (MCS) system, and it has been applied for the monitoring of steady or slowly varying sub-critical reactivity using conventional Feynman-alpha method. In the present work, this system was applied for the monitoring of rapidly varying sub-critical reactivity using the difference filter technique. The test experiment was carried out with a research reactor of Atomic Energy Institute in Kinki University. From the result, it was shown that the present system is useful for the monitoring of rapidly varying sub-critical reactivity by application of the difference filter technique.
- Nonlinear Behavior under Regional Neutron Flux Oscillations in BWR Cores, J.Nucl.Sci.Technol., J.Nucl.Sci.Technol., 38(5), 312 - 323, May 2001
- Rapid Estimation of Core-Power Ratio in Coupled-Core System by Rod Drop Method, J.Nucl.Sci.Technol., J.Nucl.Sci.Technol., 37(7), 565 - 571, Jul. 2000
- Numerical instability of time-discretized one-point kinetic equations, Kengo Hashimoto, Hideaki Ikeda, Toshikazu Takeda, Annals of Nuclear Energy, Annals of Nuclear Energy, 27(9), 791 - 803, 2000 Summary:The one-point kinetic equations with numerical errors induced by the explicit, implicit and Crank-Nicolson integration methods are derived. The zero-power transfer functions based on the present equations are demonstrated to investigate the numerical stability of the discretized systems. These demonstrations indicate unconditional stability for the implicit and Crank-Nicolson methods but present the possibility of numerical instability for the explicit method. An upper limit of time mesh spacing for the stability is formulated and several numerical calculations are made to confirm the validity of this formula.

- Dependence of Post-Drop Reactivity on Data Analysis Model for Rod Drop Experiment in a Subcritical Reactor with External Source, International Topical Meeting on Reactor Physics(PHYSOR-2006), 2006 09 , International Topical Meeting on Reactor Physics(PHYSOR-2006)
- Derivation of an Improved Correction Formula for Dynamic Rod Worth Measurement, International Topical Meeting on Mathematics and Computation(M&C-2005), 2005 09 , International Topical Meeting on Mathematics and Computation(M&C-2005)
- Numerical Instability of Neutron Diffusion Finite-Difference Equation, International Meeting on Mathematical Methods for Nuclear Applications(M&C-2001), 2001 09 , International Meeting on Mathematical Methods for Nuclear Applications(M&C-2001)

- Reduction of Delayed-Neutron Contribution to Variance-to-Mean Ratio by Application of Difference Filter Technique(共著), Journal of Nuclear Science and Technology, 36, 7, 555, 559, 1999 , 10.3327/jnst.36.555
- Spatial-harmonic Neutron Spectrum Effect on Frequency-domain Modal Analysis of Regional Stability in BWR(共著), Journal of Nuclear Science and Technology, 36, 1, 81, 94, 1999 , 10.3327/jnst.36.81
- A Simple Analytical Method for Evaluation of Limit-Cycle Oscillation Amplitude in Boiliing Water Reactors(共著), Annals of Nuclear Energy, 25, 17, 1455, 1464, 1998 , 10.1016/S0306-4549(98)00016-4
- Analysis of First-Harmonic Eigenvalue Separation Experiments on KUCA Coupled-Core(共著), Journal of Nuclear Science and Technology, 35, 3, 216, 225, 1998 , 10.3327/jnst.35.216
- Variance-to-Mean Method Generalized by Linear Difference Filter Technique(共著), Annals of Nuclear Energy, 25, 9, 639, 652, 1998 , 10.1016/S0306-4549(97)00077-7
- Feynman-α Correlation Analysis by Prompt-Photon Detection(共著), Annals of Nuclear Energy, 25, 1/3, 13, 22, 1998 , 10.1016/S0306-4549(97)00049-2
- Experimental Investigation on Secondary-Count Effect in Feynman-α Measurement by Fission Counter(共著), Annals of Nuclear Energy, 24, 11, 907, 915, 1997 , 10.1016/S0306-4549(96)00064-3
- Neutronic model for modal multichannel analysis of out-of-phase instability in boiling water reactor cores, Kengo Hashimoto, Akitoshi Hotta, Toshikazu Takeda, Annals of Nuclear Energy, 24, 2, 99, 111, 1997 , 10.1016/0306-4549(96)00006-0Summary:A neutronic model for linear multichannel analysis of out-of-phase (regional) instability in a BWR core is derived. In this model, the zero-power transfer function of a spatial-harmonic mode, the nodal component of the harmonic amplitude and the node-wise feedback coefficients for the mode appear. Applying the modal expansion technique to a transient flux, we can formulate the above transfer function, nodal component and feedback coefficients. When the A-mode eigenvalues, eigenfunctions and adjoint-eigenfunctions are numerically obtained by a three-dimensional calculation, these quantities can be evaluated. We derive a lumped neutronic model by the reduction of the present multi-channel model. Consequently, the lumped feedback coefficients for the first-harmonic mode and the nodal component of the harmonic amplitude can be explicitly expressed. Copyright © 1996 Elsevier Science Ltd.
- Dead-Time Measurement for Radiation Counters by Variance-to-Mean Method(共著), Journal of Nuclear Science and Technology, 33, 11, 863, 868, 1996 , 10.3327/jnst.33.863
- Experimental Investigations of Dead-Time Effect on Feynman-α Method(共著), Annals of Nuclear Energy, 23, 14, 1099, 1104, 1996 , 10.1016/0306-4549(95)00121-2
- Determination of Pseudo Multi-Pulse Production Rate in GM Counters by Correlation Analysis between Signal Pulses(共著), Kengo HASHIMOTO, Taizou UEDA, Journal of Nuclear Science and Technology, 33, 1, 83, 86, 1996 , 10.3327/jnst.33.83
- Space-Dependent Effect Observed in Subcriticality Measurements for Loosely Coupled-Core System(共著), Annals of Nuclear Energy, 32, 10, 1054, 1060, 1995 , 10.3327/jnst.32.1054
- INTERPRETATION OF POSITIVE SCRAM REACTIVITY IN THE RBMK-1000 REACTOR, K HASHIMOTO, M HIROSE, T SHIBATA, ANNALS OF NUCLEAR ENERGY, 21, 4, 211, 217, 1994 04 , 10.1016/0306-4549(94)90002-7Summary:The positive scram reactivity in the Chernobyl-4 reactor is interpreted by breaking it up into three components by the use of the exact perturbation method. The three components are absorption, diffusion and slowing down. The negative reactivity contribution of the absorber elements inserted is significantly reduced by the distortion of the axial flux shape and the removal of water from the bottom of the core by the graphite follower contributes to the positive reactivity predominantly through absorption and diffusion effects. The total scram reactivity thus becomes positive. Further, theoretical expression of the higher-order reactivity component induced by the flux distortion is developed on the basis of explicit higher-order perturbation formulation. The expression shows that the positive magnitude of the higher-order term is inversely proportional to the lambda-mode eigenvalue separation. The significantly small separation between the fundamental and the first axial-harmonic eigenvalue, which indicates spatial decoupling of the core is confirmed in the lambda-mode eigenvalue calculation. It is suggested that to ensure total scram reactivity is negative, the axial burnup distribution should be flattened and the follower dimensions should be modified.
- DEAD-TIME MEASUREMENT OF NEUTRON COUNTERS BY REACTOR-POWER VARIATIONAL TECHNIQUE, K HASHIMOTO, T OHSAWA, JOURNAL OF THE ATOMIC ENERGY SOCIETY OF JAPAN, 36, 3, 227, 231, 1994 03 , 10.3327/jaesj.36.227Summary:The measurements of dead time of BF3, He-3, fission and proton-recoil neutron counters were performed on the basis of the reactor-power variational technique in the reactor, UTR-KINKI reactor. The advantage of this method consists in making it possible to change the flux of irradiation field continuously and over a wide range. The reactor UTR-KINKI is well suited for the measurements since the power of the reactor can be easily changed and the range of flux is just appropriate to evaluate the dead time. The results indicate that the nonparalysable model for the dead time characteristics is applicable to the counters employed. The measured dead time of fission counter is about 1.4 mus, while those of others range of 6-9 mus.
- LINEAR MODAL-ANALYSIS OF OUT-OF-PHASE INSTABILITY IN BOILING WATER-REACTOR CORES, K HASHIMOTO, ANNALS OF NUCLEAR ENERGY, 20, 12, 789, 797, 1993 12 , 10.1016/0306-4549(93)90072-WSummary:An eigenvalue problem governing BWR core nuclear thermal-hydraulic modes which result in out-of-phase power oscillations is formulated. This formulation is based on the linearization approximation to nonlinear feedback terms and the very simple models for neutronics and thermal-hydraulics. The eigenvalue problem in 5 x 5 matrix formulation can be easily solved without using a computer. A series of the calculations are carried out, at a high-power and low-core-flow condition, to investigate the dependence of the eigenvalues and eigenfunctions on the void reactivity coefficient and the subcriticality of spatial neutronic modes, where the latter parameter is identical to the eigenvalue separation of the higher-harmonic neutronic mode. These results show that the threshold value of the void coefficient for initiating the unstable out-of-phase oscillation strongly depends on the subcriticality. The oscillation mode becomes more unstable with an increase in the absolute value of the negative void coefficient, whereas the mode becomes more stable, almost linearly, with increasing subcriticality. The resonant frequency of the oscillation and the phase shifts between the nuclear thermal-hydraulic variables are consistent with previous measured or calculated values.
- INTERPRETATION OF SPATIAL KINETICS FOR ROD DROP EXPERIMENT IN LOOSELY COUPLED-CORE SYSTEMS, K HASHIMOTO, T OHSAWA, T MISAWA, Y YAMANE, K NISHINA, S SHIROYA, JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY, 30, 10, 981, 990, 1993 10 , 10.1080/18811248.1993.9734578Summary:The coupled two-core reactor systems with various degrees of spatial coupling were constructed in the Kyoto University Critical Assembly (KUCA) to study the spatial kinetics observed in the control rod drop experiment. By applying the two-mode and the two-point kinetic models to the space-dependent rod worths measured on the basis of the one-point model, the first-harmonic lambda-mode eigenvalue separation and the reactivity coupling coefficient were inferred. The present values of these parameters agreed with the results obtained by the reactor noise measurements and the diffusion calculations. The experimental results show that the magnitudes of the spatial kinetic phenomena including the dependence of the rod reactivity worth on the detector position, the reactivity interaction effect between control rods and the transient flux tilts induced by the rod drop, which have been significantly observed in large thermal and fast power reactors, are inversely proportional to the eigenvalue separation. Applying the two-mode model, the inherent reactivity worths of control rods were also inferred from the space-dependent ones.
- Comment on Geometric Core Models for Two-Dimensional Xenon Oscillation Analysis in Large Graphite-Moderated Reactors, Journal of Nuclear Science and Technology, 30, 8, 834, 836, 1993
- Comment on Control-Rod Interference Effects Observed during Reactor Physics Experiments with Nuclear Ship MUTSU, Journal of Nuclear Science and Technology, 30, 11, 1201, 1203, 1993
- FORMULATION OF SPACE-DEPENDENT RATIOS OF CALCULATED TO EXPERIMENTAL VALUES FOR NUCLEAR CHARACTERISTICS IN SPATIALLY DECOUPLED CORES, K HASHIMOTO, ANNALS OF NUCLEAR ENERGY, 19, 9, 483, 493, 1992 09 , 10.1016/0306-4549(92)90038-DSummary:A theoretical expression of the C/E (ratio of calculation to experiment) distributions for reaction rates and reactivity worths is developed on the basis of the explicit first-order perturbation formulation. The expression shows that the degree of the C/E spatial dependence depends on not only the magnitude of the Boltzmann operator errors due to cross-section errors, but also the lambda-mode eigenvalue separations and the adjoint eigenfunctions of higher harmonics, and that the spatial shape of the dependence is described by the higher-harmonic forward eigenfunctions. Sensitivity analyses of the C/E radial dependence to various cross-section changes, based on the present expression, are carried out for a one-dimensional model of a large fast reactor assembly, ZPPR-13A. These results indicate that the first radial-harmonics dominantly contribute to the C/E radial dependence, and the sensitivity to a local change in a macroscopic fission cross-section is very high compared to the other perturbations.
- INTERPRETATION OF CONTROL ROD INTERACTION EFFECT ON THE BASIS OF MODAL APPROACH, K HASHIMOTO, A TATEMATSU, K NISHINA, T SHIBATA, ANNALS OF NUCLEAR ENERGY, 19, 4, 237, 241, 1992 04 , 10.1016/0306-4549(92)90062-GSummary:A theoretical expression of reactivity interaction between control rods is developed on the basis of the explicit higher-order perturbation method. The expression shows that the magnitude of the interaction is inversely proportional to the lambda-mode eigenvalue separation and dependence on the rod patterns is governed by the higher-harmonic eigenfunctions and the adjoint ones. Application of the formula is illustrated by numerical calculations carried out for a 1-D model of a large fast reactor core. The results indicate that the first harmonics dominantly contribute to the interaction, consequently the first-harmonic eigenvalue separation can be employed as a quantitative indication of interaction effect.
- A PRACTICAL FORMULA FOR INFERRING EIGENVALUE SEPARATION FROM FLUX TILT MEASUREMENTS IN NUCLEAR-REACTORS, K HASHIMOTO, T OHSAWA, R MIKI, T SHIBATA, ANNALS OF NUCLEAR ENERGY, 18, 3, 131, 140, 1991 , 10.1016/0306-4549(91)90048-3Summary:A practical formula for inferring the lambda-mode eigenvalue separation from flux tilt measurements is derived. The advantages of the present formula consist in both the generality and the simplicity of data-analysis, even under a higher-order model, compared with the previous expressions. The applicability of the method, based on the first-order version of the formula, is confirmed by the demonstration in the UTR-KINKI reactor. The results indicate that the flux distortions induced by the asymmetric pattern of control rods are not spatially local but global, which is responsible for the dominant excitation of the first harmonics, consequently the analysis is successful in the extraction of the first-mode eigenvalue separation. The effects of higher-harmonics past the first on the first-mode eigenvalue separation, which is neglected in the previous formula, are also evaluated.
- DERIVATION OF CONSISTENT REACTIVITY WORTH AND EIGENVALUE SEPARATION FROM SPACE-DEPENDENT ROD WORTHS ON THE BASIS OF MODAL APPROACH, K HASHIMOTO, T OHSAWA, R MIKI, T SHIBATA, ANNALS OF NUCLEAR ENERGY, 18, 6, 317, 325, 1991 , 10.1016/0306-4549(91)90017-RSummary:A method is proposed to infer the consistent reactivity worth and the lambda-mode eigenvalue separation from space-dependent control rod worths in loosely-coupled reactors. Using the modal expansion approximation for a transient flux, we derive a two-mode version of the formula for an integral-count rod drop measurement. The formula is very simple and there is no need for the theoretical correction factor. The experimental procedures are convenient as well as standard rod drop measurements. Furthermore, the present formula is more general, compared with the previous two-point formula, and is anticipated to be applicable even to large single-core reactors. The applicability of the formula is confirmed by a demonstration in the UTR-KINKI reactor, a light-water moderated and graphite-reflected reactor.
- Calculation of Spatial Harmonics in Two-Dimensional Multiplicative Systems, Kengo HASHIMOTO, Kojiro NISHINA, Journal of the Atomic Energy Society of Japan, 33, 9, 882, 889, 1991 , 10.3327/jaesj.33.882
- Theoretical Analysis of Two-Detector Coherence Functions in Large Fast Reactor Assemblies, Journal of Nuclear Science and Technology, 28, 11, 1991 , 10.3327/jnst.28.1019
- Derivation of Coupling Coefficient from Rod Drop Measurements in Two-Point Reactors, Annals of Nuclear Energy, 17, 12, 667, 672, 1990 , 10.1016/0306-4549(90)90027-B
- Parameter B/l for Decoupled Fast Critical Assemblies by Noise Coherence, Transactions of American Nuclear Society, 60, 1989
- Determination of λ-Mode Eigenvalue Separation in Large Fast Reactor by Two-Detector Correlation Method, Kengo HASHIMOTO, Kojiro NISHINA, Journal of the Atomic Energy Society of Japan, 31, 9, 1050, 1052, 1989 , 10.3327/jaesj.31.1050
- COMBINED FORCED FREE LAMINAR HEAT-TRANSFER TO A HIGHLY HEATED GAS IN A VERTICAL ANNULUS, K HASHIMOTO, N AKINO, H KAWAMURA, INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, 29, 1, 145, 151, 1986 01 , 10.1016/0017-9310(86)90042-6
- Research on Crossflow in VHTR Core, (II), Numerical Analysis of Two-Block Crossflow, Hideo KABURAKI, Takakazu TAKIZUKA, Kengo HASHIMOTO, Journal of the Atomic Energy Society of Japan, 27, 5, 450, 456, 1985 , 10.3327/jaesj.27.450
- Laminar Heat Transfer to a Gas in Annular Channels at High Heating Rate, 101,8-14, 1982
- CALCULATION OF TEMPERATURE COEFFICIENTS FOR THE LIGHT-WATER-MODERATED CORE OF KYOTO-UNIVERSITY-CRITICAL-ASSEMBLY, S WAKAMATSU, K HASHIMOTO, K NISHINA, JOURNAL OF THE ATOMIC ENERGY SOCIETY OF JAPAN, 24, 12, 963, 972, 1982
- Tentative Set of Group Constants for C-Core of Kyoto University Critical Assembly, Journal of the Atomic Energy Society of Japan, 22, 12, 860, 870, 1980

- Study on Reactor Noise Analysis
- Study on Reactor Kinetics in Large Light-Water Reactor
- Study on Reactor Physics in Large Fast Breeder Reactor