Faculty Profiles - YAMAMOTO, Akio

Papers - YAMAMOTO, Akio

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Application of Regionwise Even-Parity Discontinuity Factor to the Multigroup Analog Monte-Carlo Method

Oshima Y., Endo T., Yamamoto A., Aizawa N.

Transactions of the American Nuclear Society Vol. 125 ( 1 ) page： 904 - 907 2021

Verification of Medium-Wise Multi-Group Cross Section Calculation Capability of FRENDY/MG

Chiba G., Yamamoto A.

Transactions of the American Nuclear Society Vol. 125 ( 1 ) page： 934 - 937 2021

Dimension-reduced Nuclear Data Adjustment Method based on the Bayesian Monte-Carlo Method

Fukui Y., Endo T., Yamamoto A.

Transactions of the American Nuclear Society Vol. 125 ( 1 ) page： 900 - 903 2021

THEORETICAL DERIVATION OF UNIQUE COMBINATION-NUMBER FOR HIGHER ORDER NEUTRON CORRELATION FACTORS BASED ON PÁL-BELL EQUATION

Endo T., Yamamoto A.

Proceedings of the International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering, M and C 2021 page： 1568 - 1576 2021

Language：English Publishing type：Research paper (scientific journal) Publisher：Proceedings of the International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering, M and C 2021

The Pál-Bell equation is a master equation to describe the probability generating function (PGF) of neutron counts in the neutron multiplication system. Thanks to the Pál-Bell equation with the two-forked and the fundamental mode approximations, an analytical solution of PGF of neutron counts in a source-driven subcritical system can be theoretically derived. Thereby, the unique combination numbers for the higher-order neutron-correlation factors for a near-critical state can be theoretically clarified. This knowledge is useful to judge whether a target system is a near-critical state or not using only a histogram (or factorial moments) of neutron counts.

DOI： 10.13182/M&C21-33627

Scopus

DEVELOPMENT OF ESTIMATION METHOD FOR PROMPT NEUTRON DECAY CONSTANT USING DYNAMIC MODE DECOMPOSITION

Nishioka F., Fukui Y., Endo T., Yamamoto A., Yamanaka M., Pyeon C.H.

Proceedings of the International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering, M and C 2021 page： 1719 - 1728 2021

To estimate the prompt neutron decay constant α corresponding to the fundamental mode in a subcritical system, we try applying the Dynamic Mode Decomposition (DMD) to time-series data of neutron counts obtained by the pulsed-neutron source (PNS) method. In this study, we newly develop an estimation method of α with the statistical uncertainty by the DMD and the random sampling method. The applicability of the proposed method is demonstrated by analyzing a PNS experiment carried out at the Kyoto University Critical Assembly (KUCA).

DOI： 10.13182/M&C21-33631

Scopus

FRENDY/MG: A MULTI-GROUP CROSS SECTION GENERATION MODULE USING ACE POINTWISE CROSS SECTIONS

Yamamoto A., Endo T., Foad B., Chiba G., Tada K.

Proceedings of the International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering, M and C 2021 page： 710 - 720 2021

A generation capability of neutron multi-group cross sections is being implemented to the FRENDY nuclear data processing code, as FRENDY/MG. FRENDY/MG generates neutron multi-group cross sections for deterministic core analysis codes considering an arbitrary energy group structure. Distinguished features of FRENDY/MG are 1) use of ACE pointwise cross sections as the source of nuclear data (no evaluated nuclear data file is directly used), 2) treatment of a compound material consisting of multiple nuclides to explicitly consider the resonance interference effect. Various verifications are being carried out through the comparison with the multi-group cross sections generated by NJOY.

DOI： 10.13182/M&C21-33679

Scopus

FUEL ASSEMBLY ANALYSES WITH RESONANCE CALCULATION USING ENERGY SPECTRUM EXPANSION METHOD

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

Proceedings of the International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering, M and C 2021 page： 2219 - 2230 2021

Efficient numerical algorithms for a Resonance calculation using energy Spectrum Expansion (RSE) method were proposed for a large and complicated geometry such as a fuel assembly. The RSE method can treat complicated heterogeneous geometry considering resonance interference effect among different regions. Calculation procedure of the RSE method is composed of (1)generation of ultra-fine group spectra from ultra-fine group calculations in homogeneous geometry, (2)expansion of the spectra by orthogonal basis on energy based on singular value decomposition, (3)transport calculation for expansion coefficients and (4)reconstruction of ultra-fine group spectra in target heterogeneous regions by the expansion coefficients and the orthogonal basis. In this study, the efficient numerical algorithms for the RSE method were developed and applied. The algorithms are composed of (i)scattering source calculation by the combination of conventional slowing down and moment-to-moment transfer calculations, and (ii)matrix exponential generation in transport calculation of the RSE method with method of characteristics by diagonalization using eigenvalue decomposition. Through numerical verification, it was confirmed that effective multi-group cross sections by the RSE method with the new algorithms are well agreed with those by direct ultra-fine group calculation in the fuel assembly geometry. The RSE method with the new algorithms is applicable to the fuel assembly analysis.

DOI： 10.13182/M&C21-33621

Scopus

IMPLEMENTATION OF A RESONANCE CALCULATION USING ENERGY SPECTRUM EXPANSION METHOD INTO HETEROGENEOUS TRANSPORT CALCULATION CODE GALAXY-Z

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

Proceedings of the International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering, M and C 2021 page： 1982 - 1991 2021

A resonance calculation using the energy spectrum expansion (RSE) method has been developed in order to efficiently treat complicated heterogeneous geometry and resonance interference effect among both nuclides and regions. The three-dimensional (3D) heterogeneous transport calculation code GALAXY-Z developed by Mitsubishi Heavy Industries Ltd. uses the RSE method as resonance calculation method. In this study, resonane calculations of the GALAXY-Z code using the RSE method were performed and showed good agreements of nuclear characteristics with the ultra-fine-group method in wide range of moderator density for actual PWR fuel specifications. The GALAXY-Z code using the RSE method is applicable with high accuracy to generation of nuclear constants in normal operations and accident conditions including low moderator density conditions and can siginificantly reduce computational memory in comparison with the ultra-fine-group method.

DOI： 10.13182/M&C21-33788

Scopus

S2 Consistent Analytic CMFD Acceleration for Method of Characteristics

Oshima Y., Yamamoto A., Endo T.

Proceedings of the International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering, M and C 2021 page： 1840 - 1849 2021

A coarse mesh finite-difference (CMFD) acceleration consistent with the S2 discrete ordinate method using the step-characteristics is proposed. The analytically derived finite-difference formulation for diffusion theory (ACMFD), which is theoretically consistent with the discrete ordinate method in one-dimensional slab geometry with the S2 Gauss-Legendre quadrature, is used for the acceleration of a transport calculation. Our numerical calculations in simple geometry revealed that the consistent treatment of scattering source distribution in the ACMFD acceleration has a significant impact on the convergence property. Further, the linearized Fourier analysis of ACMFD acceleration shows the same convergence property as numerical calculations. These numerical and theoretical analyses show that the S2- consistent ACMFD acceleration is unconditionally stable without any correction to the diffusion coefficient.

DOI： 10.13182/M&C21-33737

Scopus

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

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Papers - YAMAMOTO, Akio