Preliminary study for multi-objective core design optimization using Bayesian optimization

Kuwagaki, Kazuki; Hamase, Erina; Yokoyama, Kenji; Doda, Norihiro; Tanaka, Masaaki

Proceedings of International Conference on the Physics of Reactors (PHYSOR 2026) (Internet), 8 Pages, 2026/04

https://doi.org/10.5281/zenodo.20803415

Preliminary study of diffusion and SP3 calculations in unstructured mesh geometry for core deformation reactivity evaluation on SFR

Kato, Shinya; Doda, Norihiro; Yokoyama, Kenji; Tanaka, Masaaki; Endo, Tomohiro*

Proceedings of 2025 International Congress on Advances in Nuclear Power Plants (ICAPP 2025) (Internet), 11 Pages, 2025/09

During a reactor power increase in ULOF and UTOP events in sodium-cooled fast reactors, core deformation due to thermal expansion of core elements is expected to cause a negative feed-back effect to suppress this power increase. An analytical evaluation method of core deformation reactivity for design is being developed in JAEA. However, the neutronics calculation module uses several approximations. This study aims to develop the detailed evaluation method as a reference neutron transport calculation code for confirmation of the validity of the calculated core deformation reactivity. Here, the two-dimensional finite volume method (FVM) code based on simplified P3 (SP3) approximation with unstructured mesh have been developed as the first step of the development. This paper describes the calculation theory of the FVM code, the procedure of introducing SP3 approximation into the code and the verification results of the functions developed.

Origin of ferroelectric polarization in bismuth sodium titanate

Noguchi, Yuji*; Aso, Seiyu*; Oyama, Kenji*; Ishigaki, Toru*; Yoneda, Yasuhiro; Matsuo, Hiroki*

Physical Review B, 111(21), p.214113_1 - 214113_13, 2025/06

https://doi.org/10.1103/f1l8-6g3f

We explore the electronic structure of high-quality bismuth sodium titanate (BiNaTiO) powders through a comprehensive approach combining the maximum entropy method (MEM)/Rietveld analysis of synchrotron radiation X-ray diffraction data collected at 200 K with density functional theory (DFT) calculations. We conclude that the covalent Bi-O bond and the resultant ferroelectricity stem primarily from the Bi-6p-O3-2p orbital interaction mediated through Ti-3d.

Development of core design optimization process; Feasibility study of multivariable optimization via integrated sequential analyses of neutronics, thermal-hydraulics, and fuel integrity evaluation

Kuwagaki, Kazuki; Hamase, Erina; Yokoyama, Kenji; Doda, Norihiro; Tanaka, Masaaki

Annals of Nuclear Energy, 225, p.111754_1 - 111754_10, 2025/01

https://doi.org/10.1016/j.anucene.2025.111754

Application of energy-resolving neutron imaging to major-component analyses of materials using four-channel superconducting detector

Vu, TheDang*; Shishido, Hiroaki*; Aizawa, Kazuya; Oku, Takayuki; Oikawa, Kenichi; Harada, Masahide; Kojima, Kenji M*; Miyajima, Shigeyuki*; Soyama, Kazuhiko; Koyama, Tomio*; et al.

IEEJ Transactions on Electrical and Electronic Engineering, 19(11), p.1888 - 1894, 2024/11

https://doi.org/10.1002/tee.24144

Study on heat transfer behavior of a rectangular particle bed with volumetric heating

Wen, J.*; Kamada, Yuto*; Yokoyama, Kosei*; Matsumoto, Tatsuya*; Liu, W.*; Morita, Koji*; Imaizumi, Yuya; Tagami, Hirotaka; Matsuba, Kenichi; Kamiyama, Kenji

Proceedings of 31st International Conference on Nuclear Engineering (ICONE31) (Internet), 8 Pages, 2024/11

https://doi.org/10.1115/ICONE31-134313

Development of the versatile reactor analysis code system, MARBLE3

Yokoyama, Kenji; Hazama, Taira; Taninaka, Hiroshi; Oki, Shigeo

JAEA-Data/Code 2024-007, 41 Pages, 2024/10

JAEA-Data-Code-2024-007.pdf:1.1MB

The third version of the versatile reactor analysis code system, MARBLE3, has been developed. In the development of the former version of MARBLE, object-oriented scripting language Python (Python2) had been used and then the latest version of Python (Python3) was released. However, due to its backward incompatibility, MARBLE no longer worked with Python3. For this reason, MARBLE3 has been fully modified and maintained to work with Python3. In MARBLE3, newly developed analysis codes and newly proposed calculation methods were incorporated, and the user interface was extended and solvers were reimplemented for maintainability, extensibility, and flexibility. In MARBLE3, the three-dimensional hexagonal/triangular transport code MINISTRI Ver.7 (MINISTRI7) and the three-dimensional hexagonal/triangular diffusion code D-MINISTRI are available as the new analysis codes. These codes can be used in the neutronics analysis system SCHEME and the fast reactor burnup analysis system OPRHEUS, which are the subsystems of MARBLE. In addition, the user interface of CBG, a core analysis system embedded in MARBLE, was extended so that the diffusion and transport calculation solvers for the 2-dimensional RZ system of CBG can be used on SCHEME. On the other hand, MARBLE3 has extended the functionality of the burnup calculation solver so that it can use the numerical methods proposed in the papers on the improvement of the Chebyshev rational function approximation method and the minimax polynomial approximation method. From the viewpoint of maintainability, the point reactor kinetics solver POINTKINETICS, which was introduced in MARBLE2, has been newly reworked as the KINETICS solver in MARBLE3.

Continuous structural phase transition and antiferromagnetic order in ilmenite-type NiVO

Yamamoto, Hajime*; Ikeda, Osamu*; Honda, Takashi*; Kimura, Kenta*; Aoyama, Takuya*; Ogushi, Kenya*; Suzuki, Akio*; Ishii, Kenji*; Matsumura, Daiju; Tsuji, Takuya; et al.

Physical Review Materials (Internet), 8(9), p.094402_1 - 094402_6, 2024/09

https://doi.org/10.1103/PhysRevMaterials.8.094402

Differential pressure rise event for filters of HTTR primary helium gas circulators, 2; Investigation of filter deposits and recurrence prevention measures

Nemoto, Takahiro; Fujiwara, Yusuke; Arakawa, Ryoki; Choyama, Yuya; Nagasumi, Satoru; Hasegawa, Toshinari; Yokoyama, Keisuke; Watanabe, Masashi; Onishi, Takashi; Kawamoto, Taiki; et al.

JAEA-Technology 2024-003, 17 Pages, 2024/06

JAEA-Technology-2024-003.pdf:1.91MB

In order to investigate the cause of the increase in differential pressure in the primary helium circulator filter that occurred during the RS-14 cycle, a clogged filter was investigated. As a result of the investigation, deposits caused by silicone oil were confirmed on the surface of the filter element. These results revealed that the cause of filter clogging was silicone oil mixed into the primary system due to performance deterioration of the charcoal filter in the gas circulator of primary helium purification system. As a measure to prevent the recurrence of this event, in addition to the conventional management based on operating hours for replacing of charcoal filter in the gas circulator of primary helium purification system, we have established a new replacement plan for every three years.

Development of a design optimization framework for sodium-cooled fast reactors, 3; Development of a prototype with user interface

Doda, Norihiro; Nakamine, Yoshiaki*; Yoshimura, Kazuo; Kuwagaki, Kazuki; Hamase, Erina; Yokoyama, Kenji; Kikuchi, Norihiro; Mori, Takero; Hashidate, Ryuta; Tanaka, Masaaki

Keisan Kogaku Koenkai Rombunshu (CD-ROM), 29, 6 Pages, 2024/06

As a part of the development of the "Advanced Reactor Knowledge- and AI-aided Design Integration Approach through the whole plant lifecycle (ARKADIA)" to utilize the knowledge obtained through the sodium-cooled fast reactors (SFRs) and combine the latest numerical simulation technologies, ARKADIA-Design is being developed to support the optimization of SFRs in the conceptual design stage. ARKADIA-Design consists of three systems of Virtual Plant Life System (VLS), Enhanced and AI-aided optimization System (EAS), and Knowledge Management System (KMS). A design optimization framework controls the linkage among the three systems through the interfaces in each system. In this study, we have developed a prototype of the framework for core design optimization using the coupled analysis functions in VLS and optimization control function in the linkage of EAS and VLS to investigate the applicability of the framework to the SFR design optimization process.