Faculty Profiles - ENDO Tomohiro

MISC - ENDO Tomohiro

Division display 41 - 60 of about 197 ／ All the affair displays >>

Statistical Uncertainty Quantification of Probability Tables for Unresolved Resonance Cross Sections Reviewed International journal

Kenichi Tada, Tomohiro Endo

EPJ Web of Conferences Vol. 284 page： 14013 - 14013 2023.5

Language：English Publishing type：Research paper, summary (international conference) Publisher：EDP Sciences

The probability table method is an important method to treat the self-shielding effect in the unresolved resonance region. A probability table is generated by using many “ladders” that represent pseudo resonance structures. This study developed a quantification method of the statistical uncertainty of a probability table. The product of the probability table and average cross section in each probability bin was considered as the target of the statistical uncertainty of the probability table. The central limit theorem (CLT), bootstrap method, and jackknife method were adopted to calculate the statistical uncertainty. The statistical uncertainties calculated using these methods were compared with the reference results. The calculation results showed that the statistical uncertainties obtained by CLT were similar to those of the other methods. Because the CLT calculation time was faster than that of the other methods, CLT was deemed as the best method for calculating the statistical uncertainty of the probability table. The statistical uncertainty quantification of the probability table developed in this study was implemented in nuclear data processing code FRENDY version 2. FRENDY version 2 can generate a probability table using the tolerance of the statistical uncertainty of the probability table.

DOI： 10.1051/epjconf/202328414013

Applicability evaluation of Akaike’s Bayesian information criterion to covariance modeling in the cross-section adjustment method Reviewed International journal

Shuhei Maruyama, Tomohiro Endo, Akio Yamamoto

EPJ Web of Conferences Vol. 281 page： 00008 2023.3

Language：English Publishing type：Research paper, summary (international conference) Publisher：EDP Sciences

The applicability of Akaike’s Bayesian Information Criterion (ABIC) to the covariance modeling in the cross-section adjustment method has been investigated. In the conventional cross-section adjustment method, the covariance matrices are assumed to be true. However, this assumption is not always appropriate. To improve the reliability of the cross-section adjustment method, the estimation of the covariance model using the metric ABIC has been introduced, and the performance of ABIC has been investigated through simple numerical experiments. This paper derives the formula to efficiently evaluate ABIC which is represented by a lower rank matrix to enable numerical experiments with large samples in a realistic computation time. From the results of the numerical experiments, it has been confirmed that ABIC tends to select a covariance model with fewer hyperparameters and a smaller variance for the estimation error. However, it has also been found that this desirable property of ABIC will be lost when the structure of the covariance model is far from the true one.

DOI： 10.1051/epjconf/202328100008

Development of a robust nuclear data adjustment method to outliers Reviewed International journal

Yuhei Fukui, Tomohiro Endo, Akio Yamamoto, Shuhei Maruyama

EPJ Web of Conferences Vol. 281 page： 00006 2023.3

Language：English Publishing type：Research paper, summary (international conference) Publisher：EDP Sciences

We developed a new nuclear data adjustment method for experimental data containing outliers. This method mitigates the effect of outliers by applying M-estimation, a type of robust estimation, to the conventional nuclear data adjustment method using sensitivity coefficients. Based on the M-estimation, we derived a weighted nuclear data adjustment formula and developed a weight calculation method. The weighted nuclear data adjustment formula was derived by weighting the function to take the extremum of the conventional nuclear data adjustment. The weighting of each nuclear characteristic is calculated from the difference between the measured and calculated values of the nuclear characteristic. This weight calculation method can evaluate the validity of each nuclear characteristic by considering correlations between nuclear characteristics using singular value decomposition. The proposed method and the conventional method were compared and verified by twin experiments. In the twin experiments, the nuclear data were adjusted using experimental data that intentionally included outliers. As a result of twin experiments, it was confirmed that the nuclear data were adjusted robustly and appropriately even with the experimental data containing outliers.

DOI： 10.1051/epjconf/202328100006

A New Approach for Resonance Treatment of Doubly Heterogeneous Fuel Using the RSE Method Reviewed International journal

Akio Yamamoto, Tomohiro Endo, Satoshi Takeda, Hiroki Koike, Kazuya Yamaji, Koichi Ieyama, Koji Asano

Proceedings of International Conference on Physics of Reactors 2022 (PHYSOR 2022) page： 2042 - 2051 2022.5

Language：English Publishing type：Research paper, summary (international conference) Publisher：American Nuclear Society

A new resonance calculation method for the doubly-heterogeneous (DH) fuels such as high temperature gas-cooled reactor fuel is proposed based on the Resonance calculation based on Spectral Expansion (RSE) method. The concept of pointwise disadvantage factor for fuel grain is taken into account to treat the DH fuels. The verification calculation is carried out for simplified single fuel cell and fuel compact consisting of five fuel cells and graphite moderator. The calculation results indicate that the present method can appropriately handle the space dependent self-shielding effect for DH fuels.

DOI： 10.13182/PHYSOR22-37251

Proposal and Application of ROM-Lasso Method for Sensitivity Coefficient Evaluation Reviewed International journal

Ryota Katano, Akio Yamamoto, Tomohiro Endo

Proceedings of International Conference on Physics of Reactors 2022 (PHYSOR 2022) page： 2032 - 2041 2022.5

Authorship：Last author Language：English Publishing type：Research paper, summary (international conference) Publisher：American Nuclear Society

We propose a novel method for evaluating sensitivity coefficients of neutronics parameters to cross sections, so-called the ROM-Lasso. In this method, cross sections of interest are randomly sampled, and corresponding perturbed core analyses are performed. Then, the sensitivity coefficient vector of the higher-level model is expanded via the active subspace bases obtained with the lower-level model whose dimensional complexity is smaller than that of the higher-level model, and the expansion coefficients are estimated by the lasso regression. A unique feature of the ROM-Lasso method allows the use of different bases optimized for each neutronics parameter. We conducted a verification calculation for an accelerator-driven system and demonstrated that the ROM-Lasso method can reproduce the sensitivity coefficients with a much smaller number of forward calculations than the direct method. The proposed method can be used to practically evaluate the sensitivity coefficients.

DOI： 10.13182/PHYSOR22-37557

Neutron Diffusion Calculation in Heterogeneous Geometry Based on Local/Global Iteration Using Proper Orthogonal Decomposition Reviewed International journal

Masato Ito, Tomohiro Endo, Akio Yamamoto, Yoshitada Masaoka, Yasuhiro Kodama, Hiroaki Nagano

Proceedings of International Conference on Physics of Reactors 2022 (PHYSOR 2022) page： 503 - 512 2022.5

Language：English Publishing type：Research paper, summary (international conference) Publisher：American Nuclear Society

This study newly proposes a heterogeneous core calculation method based on local/global iteration using proper orthogonal decomposition (POD). By using the singular value decomposition (SVD) and the low-rank approximation, appropriate POD bases for expanding the neutron flux can be obtained from snapshot data of the neutron flux obtained by fine mesh calculations. By projection using the POD bases, the dimension of the target equation (e.g., discretized neutron diffusion equation) can be dramatically reduced. In the proposed method, POD is effectively applied to each single assembly calculation (local calculation). Furthermore, using the local/global iteration, the effective neutron multiplication factor and the neutron flux distribution in the whole core geometry can be obtained by combining the numerical results of the local calculation for each fuel assembly and the global calculation for the whole core. As a feasibility study, the proposed method is applied to a one-dimensional heterogeneous core analysis, and the accuracy is investigated by changing the total number of POD bases.

DOI： 10.13182/PHYSOR22-37693

Development of Nuclear Data Processing CodeFRENDY Version 2 Reviewed International journal

Kenichi Tada, Akio Yamamoto, Tomohiro Endo, Go Chiba, Michitaka Ono, Masayuki Tojo

Proceedings of International Conference on Physics of Reactors 2022 (PHYSOR 2022) page： 107 - 116 2022.5

Language：English Publishing type：Research paper, summary (international conference) Publisher：American Nuclear Society

Nuclear data processing is an important interface between an evaluated nuclear data library and neutronics calculation codes. JAEA has been developed the new nuclear data processing code FRENDY from 2013. FRENDY version 1 generates the ACE files used for the continuous-energy Monte Carlo codes including PHITS, Solomon, Serpent, and MCNP and it was released as the open-source software under the 2-clause BSD license in 2019.After we released FRENDY version 1, many functions, e.g., the multi-group neutron cross-section library generation, the statistical uncertainty quantification of the probability tables for unresolved resonance cross-section, the perturbation of the ACE file, and the modification of the ENDF-6 formatted nuclear data file, are developed. We released FRENDY version 2including these functions. The present paper explains the overview of FRENDY and features of new functions implemented in FRENDY version 2.

DOI： 10.13182/PHYSOR22-37299

Area Ratio Method Using Dynamic Mode Decomposition Reviewed International journal

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

Proceedings of International Conference on Physics of Reactors 2022 (PHYSOR 2022) page： 3366 - 3375 2022.5

Authorship：Lead author Language：English Publishing type：Research paper, summary (international conference) Publisher：American Nuclear Society

To reduce the higher mode effects on the subcriticality estimation using the pulsed neutron source without the aid of a high-fidelity neutron transport calculation, we propose a new area ratio method based on a data-driven approach using the dynamic mode decomposition (DMD) with the neutron count data measured by multiple neutron detectors. Thanks to eigenvalues and eigenvectors based on DMD, the fundamental mode of the prompt neutrons and the background component due to delayed neutrons are extracted from the measured neutron count data matrix. The effectiveness of the proposed method is demonstrated via experimental analysis for a pulsed neutron source measurement performed at Kyoto University Critical Assembly.

DOI： 10.13182/PHYSOR22-37184

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

Yuhei Fukui, Tomohiro Endo, Akio Yamamoto

Transactions of the American Nuclear Society Vol. 125 ( 1 ) page： 900 - 903 2021.11

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

Yoshiki Oshima, Tomohiro Endo, Akio Yamamoto, Naoto Aizawa

Transactions of the American Nuclear Society Vol. 125 ( 1 ) page： 904 - 907 2021.11

Sensitivity Analysis in Dynamic Multi-unit PRA Evaluation Using Correlated Sampling Method Reviewed International journal

Yuki Morishita, Akio Yamamoto, Tomohiro Endo

Proc. Asian Symposium on Risk Assessment and Management (ASRAM2021) page： ASRAM2021-034 2021.10

Language：English Publishing type：Research paper, summary (international conference)

The correlated sampling method is applied to the continuous Markov-chain Monte-Carlo (CMMC) method to efficiently perform sensitivity analysis of input parameters such as failure rate of safety components. In the correlated sampling method, original and perturbed samples are assumed to trace the identical accident sequence, but the weight of the perturbed sample is adjusted to incorporate the variation of input data. The correlated sampling method is applied to the sensitivity analysis of a simple system to prove the principle. The result indicates that the sensitivity analysis for the CMMC coupling method is possible by the correlated sampling method.

Development of estimation method for prompt neutron decay constant using dynamic mode decomposition Reviewed International journal

Fuga Nishioka, Yuhei Fukui, Tomohiro Endo, Akio Yamamoto, Masao Yamanaka, Cheol Ho Pyeon

Proc. M&C 2021 page： 1719 - 1728 2021.10

Language：English Publishing type：Research paper, summary (international conference) Publisher：American Nuclear Society

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

Theoretical derivation of unique combination-number for higher order neutron correlation factors based on Pál-Bell equation Invited Reviewed International journal

Tomohiro Endo, Akio Yamamoto

Proc. M&C 2021 page： 1568 - 1576 2021.10

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper, summary (international conference) Publisher：American Nuclear Society

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

S2 Consistent Analytic CMFD Acceleration for Method of Characteristics Reviewed International journal

Yoshiki Oshima, Akio Yamamoto, Tomohiro Endo

Proc. M&C 2021 page： 1840 - 1849 2021.10

Language：English Publishing type：Research paper, summary (international conference) Publisher：American Nuclear Society

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

Fuel assembly analyses with resonance calculation using energy spectrum expansion method Reviewed International journal

Ryoichi Kondo, Tomohiro Endo, Akio Yamamoto, Satoshi Takeda, Hiroki Koike, Kazuya Yamaji, Daisuke Sato

Proc. M&C 2021 page： 2219 - 2230 2021.10

Language：English Publishing type：Research paper, summary (international conference) Publisher：American Nuclear Society

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

FRENDY/MG: a multi-group cross section generation module using ace pointwise cross sections Reviewed International journal

Akio Yamamoto, Tomohiro Endo, Basma Foad, Go Chiba, Kenichi Tada

Proc. M&C 2021 page： 710 - 720 2021.10

Language：English Publishing type：Research paper, summary (international conference) Publisher：American Nuclear Society

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

Multi-Group Cross Section Library Generation by FRENDY for Fast Reactor Neutronics Calculations Reviewed International journal

Go Chiba, Akio Yamamoto, Kenichi Tada, Tomohiro Endo

Transactions of the American Nuclear Society Vol. 124 page： 556 - 558 2021.6

Verification of the Multi-Group Generation Capability of FRENDY Nuclear Data Processing Code for Recent Nuclear Data through Comparison of One-group Reaction Rates Reviewed International journal

Akio Yamamoto, Kenichi Tada, Go Chiba, Tomohiro Endo

Transactions of the American Nuclear Society Vol. 124 page： 544 - 547 2021.6

Perturbation-Theory-Based Sensitivity Analysis of Prompt Neutron Decay Constant for Water-Only System Reviewed International journal

Tomohiro Endo, Akihiro Noguchi, Akio Yamamoto, Kenichi Tada

Transactions of the American Nuclear Society Vol. 124 page： 184 - 187 2021.6

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 Reviewed International journal

Ryoichi Kondo, Tomohiro Endo, Akio Yamamoto, Satoshi Takeda, Hiroki Koike, Kazuya Yamaji, Koichi Ieyama, Daisuke Sato

EPJ Web of Conferences Vol. 247 page： 02006 - 02006 2021.2

Language：English Publishing type：Research paper, summary (international conference) Publisher：EDP Sciences

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

　 PREV - NEXT 　

<ENDO Tomohiro>

MISC - ENDO Tomohiro