Faculty Profiles - YAMAMOTO, Akio

Papers - YAMAMOTO, Akio

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Data Assimilation Using Subcritical Measurement of Prompt Neutron Decay Constant Open Access

Endo Tomohiro, Yamamoto Akio

NUCLEAR SCIENCE AND ENGINEERING Vol. 194 ( 11 ) page： 1089 - 1104 2020.11

Implementation of the unscented transformation with low rank approximation in uncertainty analysis during large-break loss of coolant accident International coauthorship

Foad Basma, Yamamoto Akio, Endo Tomohiro

ANNALS OF NUCLEAR ENERGY Vol. 146 2020.10

Uncertainty and regression analysis of the MSLB accident in PWR based on unscented transformation and low rank approximation International coauthorship

Foad Basma, Yamamoto Akio, Endo Tomohiro

ANNALS OF NUCLEAR ENERGY Vol. 143 2020.8

Applicability of a reduced order model for a safety analysis code to statistical safety analysis Reviewed

Matsushita Masaki, Endo Tomohiro, Yamamoto Akio

JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY page： 1-12 2020.7

Efficient uncertainty quantification for PWR during LOCA using unscented transform with singular value decomposition International coauthorship

Foad Basma, Yamamoto Akio, Endo Tomohiro

ANNALS OF NUCLEAR ENERGY Vol. 141 2020.6

Impact of Various Parameters on Convergence Performance of CMFD Acceleration for MOC in Multigroup Heterogeneous Geometry

Oshima Yoshiki, Endo Tomohiro, Yamamoto Akio, Kodama Yasuhiro, Ohoka Yasunori, Nagano Hiroaki

NUCLEAR SCIENCE AND ENGINEERING Vol. 194 ( 6 ) page： 477 - 491 2020.6

Application of the multigrid amplitude function method for time-dependent MOC based on the linear source approximation Reviewed

Tsujita Kosuke, Endo Tomohiro, Yamamoto Akio

JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY 2020.1

Subcriticality measurement using time-domain decomposition-based integral method for simultaneous reactivity and source changes Reviewed

Endo Tomohiro, Nonaka Asahi, Imai Sho, Yamamoto Akio, Sakon Atsushi, Hashimoto Kengo

JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY 2020.1

A kinetic model for the direct response matrix method

Mitsuyasu Takeshi, Yamamoto Akio

JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY Vol. 57 ( 1 ) page： 90 - 99 2020.1

Fast reproduction of time-dependent MOC calculations using the reduced order model based on the proper orthogonal and singular value decompositions

Tsujita K., Endo T., Yamamoto A.

Transactions of the American Nuclear Society Vol. 123 ( 1 ) page： 1349 - 1353 2020

Subcriticality estimation using unscented Kalman filter for reactivity- And source-transients

Endo T., Yamamoto A., Yamanaka M., Pyeon C.H.

Transactions of the American Nuclear Society Vol. 123 ( 1 ) page： 841 - 844 2020

Recent Research Activities on Nuclear Reactor Physics Using the Computational Science

YAMAMOTO Akio

The Proceedings of Mechanical Engineering Congress, Japan Vol. 2020 ( 0 ) page： K08101 2020

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Mechanical Engineers

<p>Outline of the nuclear reactor core analysis and computational methods used in this analysis are described. Various techniques and approximations are used to perform core analysis with practical computational resources. Recent progress on computer hardware and numerical algorithms enabled us to use more precise and accurate analysis methods.</p>

DOI： 10.1299/jsmemecj.2020.k08101

CiNii Research

A resonance calculation method using energy expansion based on a reduced order model: Use of ultra-fine group spectrum calculation and application to heterogeneous geometry

Kondo R., Endo T., Yamamoto A., Takeda S., Koike H., Yamaji K., Ieyama K., Sato D.

International Conference on Physics of Reactors: Transition to a Scalable Nuclear Future, PHYSOR 2020 Vol. 2020-March page： 152 - 161 2020

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：International Conference on Physics of Reactors: Transition to a Scalable Nuclear Future, PHYSOR 2020

A Resonance calculation using energy Spectral Expansion (RSE) method has been recently proposed in order to efficiently treat complicated heterogeneous geometry and resonance interference effect. In the RSE method, ultra-fine group spectra are generated from ultra-fine group calculations in homogeneous geometry, and the spectra are expanded by the orthogonal basis on energy based on the singular value decomposition. Then the transport calculation for expansion coefficients is numerically performed, and the ultra-fine group spectra in the target heterogeneous regions are reconstructed by the expansion coefficients and the orthogonal basis. In this study, the RSE method is applied to multi-cell geometries including UO2, MOX and water cells, in which the resonance interference effect between UO2 and MOX fuel cells appears. The validity of the RSE method is confirmed through comparison with the reference effective multi-group cross sections obtained from the direct ultra-fine group calculation in the target heterogeneous geometry.

DOI： 10.1051/epjconf/202124702006

Scopus

Experiment of unique combination number due to the third-order neutron-correlation

Endo T., Imai S., Watanabe K., Yamamoto A., Sakon A., Hashimoto K., Yamanaka M., Pyeon C.H.

International Conference on Physics of Reactors: Transition to a Scalable Nuclear Future, PHYSOR 2020 Vol. 2020-March page： 1736 - 1744 2020

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：International Conference on Physics of Reactors: Transition to a Scalable Nuclear Future, PHYSOR 2020

From zero-power reactor noise measurement, the second- and third-order neutron correlation factors Y and y3 can be evaluated by analyzing mean, variance, the third-order central moment of neutron count data. Theoretically, it is expected that the neutron-correlation ratio Y3/Y2 converges to the unique combination number “3” at a near-critical state in an arbitrary system without depending on the fissile material and the neutron-energy spectrum of core, as the neutron counting gate width T increases sufficiently. Thus, the information about the difference between y3/Y2 and “3” has the potential to judge whether a target unknown system is critical or not and to roughly guess the absolute value of subcriticality. In this study, the detector dead-time effect on y3/Y2 is theoretically investigated based on the heuristic method using the single-, pair-, and trio-detection probabilities with the fundamental mode approximation. As a result, it is clarified that the saturation value of y3/Y2 converges to “3” independent of the dead time, when a target system is a critical state. For validation, actual experimental results are presented for a non-multiplication system driven by 252Cf spontaneous source, and shallow and deep subcritical systems at Japanese experimental facilities (UTR-KINKI and KUCA) under the shutdown state. Consequently, it is demonstrated that y3/Y2 shows a significant difference from “3” in the non-multiplication system. In the case of subcritical systems driven by inherent neutron sources, it is confirmed that the ratios y3/Y2 are close to the unique combination number “3,” and the slight difference from “3” is measurable by the long-time reactor noise measurement for the deep subcritical system.

DOI： 10.1051/epjconf/202124709004

Scopus

Estimated criticality lower-limit multiplication factor of low-enriched uranium dioxide-concrete system using the bootstrap method

Hayashi T., Nishioka F., Endo T., Yamamoto A.

International Conference on Physics of Reactors: Transition to a Scalable Nuclear Future, PHYSOR 2020 Vol. 2020-March page： 2690 - 2697 2020

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：International Conference on Physics of Reactors: Transition to a Scalable Nuclear Future, PHYSOR 2020

The present paper aims to evaluate the estimated criticality lower-limit multiplication factor of fuel debris in a form of uranium dioxide-concrete mixture for a study of criticality control on the fuel debris generated through the molten core concrete interaction in a severe accident of a light water reactor. The estimated criticality lower-limit multiplication factor is evaluated using the bootstrap method where the assumption of the normal distribution is not necessary. In addition, it is calculated taking into account correlation coefficients that represent the degrees of neutronic similarity between the target system and benchmark critical experiment systems, experimental uncertainties of benchmark data, and statistical uncertainties of calculated effective multiplication factor by a continuous energy Monte Carlo code. This paper shows that the estimated criticality lower-limit multiplication factor using the bootstrap method can be comparable with a baseline upper-subcritical-limit which is evaluated by Whisper-1.1 without margins of subcriticality for uncertainties from nuclear covariance data and undetected errors in software.

DOI： 10.1051/epjconf/202124717001

Scopus

Development of FRENDY nuclear data processing code: Generation capability of multi-group cross sections from ace file

Yamamoto A., Endo T., Tada K.

Transactions of the American Nuclear Society Vol. 122 page： 714 - 717 2020

Application of bootstrap method to estimated criticality lower-limit multiplication factor considering nuclear data-induced uncertainty

Hayashi T., Endo T., Yamamoto A.

Transactions of the American Nuclear Society Vol. 122 page： 458 - 461 2020

Loading pattern optimization for a PWR using Multi-Swarm Moth Flame Optimization Method with Predator Reviewed

Ishiguro Satomi, Endo Tomohiro, Yamamoto Akio

JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY 2019.12

Development of a reduced order model for severe accident analysis codes by singular value decomposition aiming probabilistic safety margin analysis Reviewed

Matsushita Masaki, Endo Tomohiro, Yamamoto Akio

JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY 2019.12

Track 1: Severe Accident Phenomena, Fukushima Accident Analysis

Journal of the Society of Mechanical Engineers Vol. 122 ( 1211 ) page： 10 - 12 2019.10

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Papers - YAMAMOTO, Akio