Faculty Profiles - YAMAMOTO, Akio

Papers - YAMAMOTO, Akio

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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

APPLICATION OF THE FOREST SHIELDING FACTOR TO THE MAXIMUM-LIKELIHOOD EXPECTATION MAXIMIZATION METHOD FOR AIRBORNE RADIATION MONITORING Reviewed

Sasaki M., Sanada Y., Yamamoto A.

RADIATION PROTECTION DOSIMETRY Vol. 184 ( 3-4 ) page： 400-404 2019.10

Transport consistent diffusion coefficient for CMFD acceleration and comparison of convergence properties

Yamamoto Akio, Endo Tomohiro, Giho Akinori

JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY Vol. 56 ( 8 ) page： 716 - 723 2019.8

A simple treatment of increased gap due to fuel assembly bowing through correction of cross sections

Yamamoto Akio, Endo Tomohiro, Nagano Hiroaki, Ohoka Yasunori, Yamamoto Kento

JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY Vol. 56 ( 6 ) page： 471 - 478 2019.6

Development of assembly bowing model for pin-by-pin core calculations

Yamamoto K., Ohoka Y., Nagano H., Yamamoto A., Endo T.

International Conference on Nuclear Engineering, Proceedings, ICONE Vol. 2019-May 2019.5

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：International Conference on Nuclear Engineering, Proceedings, ICONE

Calculation capability of the pin-power distribution considering the variation of the assembly gap size due to assembly bowing was implemented in the pin-by-pin core calculation code SCOPE2. The previous studies show that the perturbation of geometry can be treated by the perturbation of macroscopic cross-section or atomic number density of the region instead of explicit consideration of geometry deformation. This methodology was applied to the assembly gap region: the variation of the gap size was treated by the correction on the macroscopic cross-section of the gap water. The correction model for the cross-section of gap water was implemented in SCOPE2 since it treats pin-by-pin cross-sections in a transport calculation. The correction was made according to the variation in the gap size. This implemented model has an advantage that the modification of the cross-section tables used in the core calculation is not necessary to consider the variation of gap size. For single assembly and multi-assemblies geometries, the assembly bowing model implemented in SCOPE2 was verified by comparing with the reference results using the assembly calculation code AEGIS, where the gap size perturbation was explicitly considered by varying the geometry of the gap region. It was confirmed that the variation of pin-power distribution due to the assembly bowing can be appropriately treated by SCOPE2 with the assembly bowing model.

Scopus

Experimental validation of unique combination numbers for third- and fourth-order neutron correlation factors of zero-power reactor noise

Endo Tomohiro, Yamamoto Akio, Yamanaka Masao, Pyeon Cheol Ho

JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY Vol. 56 ( 4 ) page： 322 - 336 2019.4

Comparison of theoretical formulae and bootstrap method for statistical error estimation of Feynman-alpha method

Endo Tomohiro, Yamamoto Akio

ANNALS OF NUCLEAR ENERGY Vol. 124 page： 606 - 615 2019.2

Inverse estimation methods of unknown radioactive source for fuel debris search

Sugaya Shinji, Endo Tomohiro, Yamamoto Akio

ANNALS OF NUCLEAR ENERGY Vol. 124 page： 49 - 57 2019.2

A New Interpretation of Discontinuity Factor

Yamamoto Akio, Endo Tomohiro

NUCLEAR SCIENCE AND ENGINEERING Vol. 193 ( 9 ) page： 991 - 997 2019

Utilization of Regionwise Even-Parity Discontinuity Factor to Reduce Discretization Error of MOC

Yamamoto Akio, Giho Akinori, Endo Tomohiro

NUCLEAR SCIENCE AND ENGINEERING Vol. 193 ( 3 ) page： 253 - 268 2019

DEVELOPMENT OF ASSEMBLY BOWING MODEL FOR PIN-BY-PIN CORE CALCULATIONS

Yamamoto Kento, Ohoka Yasunori, Nagano Hiroaki, Yamamoto Akio, Endo Tomohiro

The Proceedings of the International Conference on Nuclear Engineering (ICONE) Vol. 2019.27 ( 0 ) page： 1022 2019

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

DOI： 10.1299/jsmeicone.2019.27.1022

CiNii Research

Subcriticality - from basics to applications (1)

Endo Tomohiro, Tsujimoto Kazufumi, Yamamoto Akio

Journal of the Atomic Energy Society of Japan Vol. 61 ( 10 ) page： 734 - 738 2019

Mission of Reactor Physics

Chiba Go, Yamamoto Akio

Journal of the Atomic Energy Society of Japan Vol. 61 ( 4 ) page： 254 - 256 2019

Uncertainty quantification/reduction of BWR core characteristics considering cross section and thermal-hydraulics uncertainties

Ito M., Yamamoto A., Endo T., Ama T.

Transactions of the American Nuclear Society Vol. 120 page： 851 - 854 2019

A resonance calculation method using energy expansion bases based on a reduced order model

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

International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering, M and C 2019 page： 1081 - 1092 2019

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering, M and C 2019

A Resonance calculation using energy Spectral Expansion bases (the RSE method) is newly proposed. In the present method, an ultra-fine group spectrum appeared in a resonance calculation is expanded by expansion bases on energy. The transport equation for the expansion coefficients is derived, which is the simultaneous first order differential equation for the expansion coefficients. The present method is applied to a one-dimensional slab geometry composed of 238U. Comparisons of the results obtained by the present and the ultra-fine group (reference) methods show the fundamental validity of this method.

Scopus

Application of various superhomogenization (SPH) methods for the method of characteristics

Sawada K., Endo T., Yamamoto A.

International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering, M and C 2019 page： 1534 - 1543 2019

To reduce the error due to the difference between the fine and the coarse calculation conditions in a transport calculation using method of characteristics (MOC), the superhomogenization (SPH) method has been widely used. However, the conventional SPH method has a problem with numerical stability in the iterative calculations for the estimation of SPH factors, especially when local strong absorbers exist in a calculation geometry. To address this problem, improvements of the SPH methods were tested to reduce the angular and spatial discretization error of the MOC. The performances of the various SPH methods were confirmed in pressurized water reactor (PWR) 2 × 2 fuel assembly geometries and in a PWR core geometry. The results of verification indicate that in a core geometry the improved SPH methods provide better accuracy than that of the conventional SPH.

Scopus

Calculation method of estimated criticality lower-limit multiplication factor using the bootstrap method

Hayashi T., Endo T., Yamamoto A.

International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering, M and C 2019 page： 1874 - 1885 2019

The present paper describes a calculation method of the estimated criticality lower-limit multiplication factor (ECLLMF) using the bootstrap method, which is an uncertainty evaluation method. In the conventional method, the normal distribution is assumed for a probability distribution with respect to calculation biases of effective multiplication factors (keff) to evaluate ECLLMF. To propose a methodology without the assumption of the normal distribution, an estimation method of ECLLMF is newly developed using the bootstrap method, where the assumption of the normal distribution is not necessary. From the verification results, it is confirmed that the estimation result using the non-parametric bootstrap method is more reasonable than that using the conventional method, when a probability distribution of keff does not obey the normal distribution.

Scopus

Data assimilation using subcritical measurement of prompt neutron decay constant

Endo T., Yamamoto A.

International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering, M and C 2019 page： 1864 - 1873 2019

The prompt neutron decay constant α can be directly measured by the reactor noise analysis method (e.g., the Feynman-α method) in a steady-state subcritical system. In this study, the applicability of the data assimilation techniques (i.e., the bias factor and cross section adjustment methods) using a subcritical measurement of α conducted at the Kyoto University Critical Assembly (KUCA) was investigated to reduce the nuclear data-induced uncertainty of keff.The sensitivity coefficients of keff and α with respect to the nuclear data were efficiently estimated using a deterministic SN transport code with the first-order perturbation theory. As a result, a priori relative uncertainty of keff due to the 56 group SCALE covariance data can be reduced. The experimental value of α contributes to improving nuclear data of fission spectrum X and total fission neutron number v via strong correlations between X and prompt Xp and between v and prompt vp.

Scopus

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Papers - YAMAMOTO, Akio