Faculty Profiles - YAMAMOTO, Akio

Papers - YAMAMOTO, Akio

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Estimation of subcriticality in dollar units based on integral method for arbitrary state-change in subcritical system

Nonaka A., Endo T., Yamamoto A.

Transactions of the American Nuclear Society Vol. 119 page： 1112 - 1115 2018

Estimation of subcriticality in dollar units using integral method for subcritical system

Nonaka A., Endo T., Yamamoto A.

International Conference on Physics of Reactors, PHYSOR 2018: Reactor Physics Paving the Way Towards More Efficient Systems Vol. Part F168384-5 page： 3271 - 3282 2018

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：International Conference on Physics of Reactors, PHYSOR 2018: Reactor Physics Paving the Way Towards More Efficient Systems

A subcriticality measurement method using the integral method is developed for any stepwise transient. The integral method usually applied to a negative reactivity insertion using the rod-drop and the source-jerk methods. In this study, it is clarified that the integral method can be applied to measure positive reactivity insertion. During refueling of a reactor, not only reactivity but also neutron source intensity and neutron generation time simultaneously change. In order to accurately monitor the subcriticality under these conditions, variations of these parameters must be taken into consideration. Therefore, a subcriticality measurement method is developed, which is applicable to not only variation of reactivity but also simultaneous variations of neutron source intensity and neutron generation time. Furthermore, the present method utilizes only measurement value of neutron count rate, thus the proposed method is practical. Verification calculations are carried out for a step-wise change of reactivity, neutron source intensity, and neutron generation time. The results indicate that reactivity is accurately predicted for the change of the neutron source intensity, which is difficult to achieve by the neutron source multiplication method. On the other hand, although the change of the neutron generation time has considerable impacts on the estimated result of subcriticality, the predicted error is less than 10% for very large variation of neutron generation time.

Scopus

Estimation of subcriticality using particle filter method

Ikeda T., Kimura T., Endo T., Yamamoto A.

Transactions of the American Nuclear Society Vol. 118 page： 851 - 854 2018

Estimation of subcriticality using particle filter method

Ikeda T., Kimura T., Endo T., Yamamoto A.

AISTech - Iron and Steel Technology Conference Proceedings Vol. 2018-May page： 851 - 854 2018

Inverse estimation methods of unknown radioactive source for fuel debris search

Sugaya S., Endo T., Yamamoto A.

International Conference on Physics of Reactors, PHYSOR 2018: Reactor Physics Paving the Way Towards More Efficient Systems Vol. Part F168384-4 page： 2632 - 2643 2018

To identify distribution of fuel debris remaining in the reactor vessel and/or the containment vessel of Fukushima Daiichi NPS, we focused on the inverse estimation of radioactive source distribution using measured values of radiation counts. The Maximum Likelihood-Expectation Maximization (ML-EM) method and the Moore-Penrose Matrix Inverse (MPMI) method are examined. The ML-EM method has been used for image reconstruction of computed tomography, and the MPMI method is one of the solution methods for simultaneous linear equations. A simple calculation model simulating the containment vessel were constructed including detectors and radiation sources. In actual situation, sufficient number of radiation measurement positions would not be available owing to the complexity of structures inside the containment vessel. Thus, the number of radiation measurement points (number of constraints) are smaller than positions of radiation source. It means that an underdetermined inverse problem should be solved. The detection probability of radiation (neutron or photon) is calculated by the adjoint transport calculation since the detection probability is used as the coupling coefficient between a radiation count at a detector and a radioactive source. Result of estimation using the ML-EM or the MPMI method indicates that the accuracy of estimation depends on the distance between a radiation source and a detector, and radiation count measurement positions. The ML-EM and the MPMI methods show different prediction accuracy depending on the calculation condition. It is found that the detectors should be placed at vicinity of radiation sources of interest and that the applicability of the inverse estimation does not strongly depend on the radioactivity distribution.

Scopus

Quantification of modeling approximation error of pin-cell calculation using kriging and principal component analysis

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

Transactions of the American Nuclear Society Vol. 118 page： 875 - 878 2018

Quantification of modeling approximation error of pin-cell calculation using kriging and principal component analysis

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

AISTech - Iron and Steel Technology Conference Proceedings Vol. 2018-May page： 875 - 878 2018

Reduction of cross section table size for core analysis using dimensionality reduction technique

Yamamoto M., Endo T., Yamamoto A.

Transactions of the American Nuclear Society Vol. 119 page： 1226 - 1228 2018

Sensitivity coefficient analysis of omega-eigenvalue based on first-order perturbation theory

Endo T., Yamamoto A.

International Conference on Physics of Reactors, PHYSOR 2018: Reactor Physics Paving the Way Towards More Efficient Systems Vol. Part F168384-2 page： 1240 - 1253 2018

Experimental results of prompt neutron decay constant α is useful information to validate numerical results of ω -eigenvalue for spatial and energetic fundamental mode. In order to accomplish the data assimilation technique using α, it is desirable to establish an efficient numerical calculation method for sensitivity coefficient analysis of ω -eigenvalue. For this purpose, the numerical calculation method using the standard first-order perturbation theory is investigated. A specific theoretical formula is derived to evaluate the sensitivity coefficient of ω to nuclear data. The derived formula utilizes forward and adjoint eigenfunctions which consist of neutron flux and delayed neutron precursor densities. Through a feasibility study based on the multi-group diffusion calculation, the derived formula is verified by comparing with the reference results using the direct method. In addition, it is confirmed that the prompt approximation is applicable to the evaluation of sensitivity coefficient of α for a subcritical state where α is sufficiently larger than decay constants of delayed neutron precursors.

Scopus

Estimation of Modeling Approximation Error of Core Analysis Using the Surrogate Model with Kriging Reviewed

Tomomi Hanai, Tomohiro Endo, Yasuhiro Kodama, Yasunori Ohoka, Akio Yamamoto

rans. Am. Nucl. Soc. Vol. 117 page： 1269-1272 2017.11

Application of the GENESIS Code to the Kobayashi 3D Benchmark Problem Reviewed

Akio Yamamoto, Akinori Giho, Tomohiro Endo

Trans. Am. Nucl. Soc. Vol. 117 page： 1403-1406 2017.11

Recent developments in the GENESIS code based on the Legendre polynomial expansion of angular flux method Open Access

Yamamoto Akio, Giho Akinori, Endo Tomohiro

NUCLEAR ENGINEERING AND TECHNOLOGY Vol. 49 ( 6 ) page： 1143 - 1156 2017.9

Uncertainty Quantification of Activation Due to Cross Section Data in Neutron Shielding Calculation Reviewed

Kimihiro Yokoi,Tomohiro Endo,Akio Yamamoto,Ryoji Mizuno,Yoshio Kimura

Proc. 2017 International. Cogress on Advances in Nuclear Power Plants 2017.4

Application of Bias Factor Method using Random Sampling Technique for Critical Eigenvalue Prediction of BWR Reviewed

Motohiro Ito,Tomohiro Endo,Akio Yamamoto,Yusuke Kuroda,Takashi Yoshii

Proc. 2017 International Cogress on Advances in Nuclear Power Plants 2017.4

Development of Dynamic Probabilistic Risk Assessment Model for PWR using Simplified Plant Simulation Method Reviewed

Shohei Otsuki,Tomohiro Endo,Akio Yamamoto

Proc. 2017 International Cogress on Advances in Nuclear Power Plants 2017.4

Development of GENESIS, a Three-dimensional Heterogeneous Transport Code based on the LEAF Method Reviewed

Akio Yamamoto,Akinori Giho,Tomohiro Endo

Proc. Int. Conf. on Math. and Comp. Methods Applied to Nucl. Sci. & Eng. (M&C2017) 2017.4

Theoretical Discussion of Statistical Error of Variance-to-Mean Ratio Reviewed

Tomohiro Endo,Akio Yamamoto

Proc. Int. Conf. on Math. and Comp. Methods Applied to Nucl. Sci. & Eng. (M&C2017) 2017.4

Inverse Estimation of Unknown Radioactive Source using Detection Probability by Adjoint Calculation

Shinji Sugaya,Tomohiro Endo,Akio Yamamoto

Proc. Int. Conf. on Math. and Comp. Methods Applied to Nucl. Sci. & Eng. (M&C2017) 2017.4

Uncertainty Quantification of Bell Factor for Sjöstrand Method due to Cross-section Data for MA core Reviewed

Toshiki Kimura,Tomohiro Endo,Akio Yamamoto

Proc. Int. Conf. on Math. and Comp. Methods Applied to Nucl. Sci. & Eng. (M&C2017) 2017.4

A coupling model for the two-stage core calculation method with subchannel analysis for boiling water reactors

Mitsuyasu Takeshi, Aoyama Motoo, Yamamoto Akio

ANNALS OF NUCLEAR ENERGY Vol. 102 page： 77 - 84 2017.4

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Papers - YAMAMOTO, Akio