Numerical verification for the effect of suppressing hydrogen embrittlement by Sn doping in the Al-Zn-Mg alloy

Ebihara, Kenichi; Fujihara, Hiro*; Shimizu, Kazuyuki*; Yamaguchi, Masatake; Toda, Hiroyuki*

International Journal of Hydrogen Energy, 136, p.751 - 756, 2025/06

https://doi.org/10.1016/j.ijhydene.2024.05.146

It has been experimentally reported that adding tin (Sn) to high-strength aluminum-zinc-magnesium (Al-Zn-Mg) alloys effectively suppresses hydrogen (H) embrittlement, which may be attributed to H absorption by the second-phase particles of Sn. To verify this fact, a simulation of H entry into the Sn phase in Al was performed using a model based on the reaction-diffusion equation that incorporates the solid solution energy of H evaluated by first-principles calculations. The results showed that the H solid solution site concentration of the second-phase particles must be at least five times higher than that of the Al phase for H absorption by the Sn second-phase particles to suppress H embrittlement. Therefore, the actual H embrittlement suppression effect of Sn second-phase particles is limited, and other factors may influence the suppression of H embrittlement in the experiment.

Gradient residual stress and fatigue life prediction of induction hardened carbon steel S38C axles; Experiment and simulation

Qin, T. Y.*; Hu, F. F.*; Xu, P. G.; Zhang, H.*; Zhou, L.*; Ao, N.*; Su, Y. H.; Shobu, Takahisa; Wu, S. C.*

International Journal of Fatigue, 185, p.108336_1 - 108336_13, 2024/08

https://doi.org/10.1016/j.ijfatigue.2024.108336

Development of element functions and design optimization procedures for knowledge- and AI-aided advanced reactor lifecycle optimization method, ARKADIA

Tanaka, Masaaki; Enuma, Yasuhiro; Okano, Yasushi; Uchibori, Akihiro; Yokoyama, Kenji; Seki, Akiyuki; Wakai, Takashi; Asayama, Tai

Mechanical Engineering Journal (Internet), 11(2), p.23-00424_1 - 23-00424_13, 2024/04

https://doi.org/10.1299/mej.23-00424

The outline and development status of element functions and design optimization process in ARKADIA to transform advanced nuclear reactor design to meet expectations of a safe, economic, and sustainable carbon-free energy source are introduced. It is also briefly explained that ARKADIA will realize Artificial Intelligence (AI)-aided integrated numerical analysis to offer the best possible solutions for the design and operation of a nuclear plant including optimization of safety equipment, and merge state-of-the-art numerical simulation technologies and a knowledge base that stores data and insights from past nuclear reactor development projects and R&Ds with AI technologies.

Numerical interpretation of thermal desorption spectra of hydrogen from high-carbon ferrite-austenite dual-phase steel

Ebihara, Kenichi; Sekine, Daiki*; Sakiyama, Yuji*; Takahashi, Jun*; Takai, Kenichi*; Omura, Tomohiko*

International Journal of Hydrogen Energy, 48(79), p.30949 - 30962, 2023/09

https://doi.org/10.1016/j.ijhydene.2023.04.205

To understand hydrogen embrittlement (HE), which is one of the stress corrosion cracking of steel materials, it is necessary to know the H distribution in steel, which can be effectively interpreted by numerical simulation of thermal desorption spectra. In weld metals and TRIP steels, residual austenite significantly influences the spectra, but a clear H distribution is not well known. In this study, an originally coded two-dimensional model was used to numerically simulate the previously reported spectra of high-carbon ferritic-austenitic duplex stainless steels, and it was found that H is mainly trapped at the carbide surface when the amount of H in the steel is low and at the duplex interface when the amount of H is high. It was also found that the thickness dependence of the H desorption peak for the interface trap site is caused by a different reason than the conventional one.

Experiment and numerical simulation of pulsation flow in single channel for Li-7 enrichment technology development by MCCCE method

Horiguchi, Naoki; Yoshida, Hiroyuki; Kitatsuji, Yoshihiro; Hasegawa, Makoto*; Kishimoto, Tadafumi*

Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 7 Pages, 2023/05

From the viewpoint of energy security in Japan and reduction of the environmental load, continuous operation of light water reactors is essential. Since a pH adjuster with enriched Li-7 ions is required for water quality control on PWR, the development of Li-7 enrichment technology is one of the key issues. The multi-channel counter-current electrophoresis (MCCCE) method has been developed as the technology with a low environmental load. To put this method into practical use, it is necessary to understand Li-7 ion behavior in the channel flow and optimize the experimental condition to separate Li-7 and its isotope. In this paper, to understand Li-7 ion behavior in a single channel of the experimental apparatus, a numerical simulation method based on a computational fluid dynamics (CFD) code with a particle tracking method, TPFIT-LPT, was developed. In the method, the motion of multiple ions under the electric field was simulated as a particle with an added velocity by the electric field. The difference in the isotopes was represented by changing of the magnitude of the added velocity. We also considered that although it is impossible to measure the behavior of each ion, it is important to measure the flow velocity of the bulk fluid for the validation of the numerical simulation. We developed a lab-scale experimental apparatus in which the single channel of the actual apparatus was simplified to measure the flow velocity by Particle Image Velocimetry (PIV). We set a pulsation flow condition on the lab-scale experiment, which is one of difficult conditions for the numerical simulation, and measured the velocity. As the result, we confirmed that the pulsation flow was reproduced. We set the measured data as the inlet boundary condition of the numerical simulation and conducted it. As the numerical result, we confirmed the ions affected by the electric field moved upstream with pulsation. We also confirmed the effect of the electric field on the motion of the isotope.

Development of evaluation method for thermal behavior in and around fuel debris based on two-fluid model

Yoshida, Hiroyuki; Horiguchi, Naoki

Nihon Kikai Gakkai Kanto Shibu Dai-29-Ki Sokai, Koenkai Koen Rombunshu (Internet), 5 Pages, 2023/03

https://doi.org/10.1299/jsmekanto.2023.29.17H23

To reduce contaminated water at the Fukushima Daiichi Nuclear Power Plant and consider the fuel debris retrieval method, a numerical simulation method is required to evaluate the effects of water injection. Then, we are developing a multiphase CFD simulation method based on the three-dimensional two-fluid model to evaluate thermal-hydraulic behavior in the primary containment vessel. The numerical simulation method was developed by introducing the required functions into the ACE-3D. This paper presents an overview of the porous model introduced to the ACE-3D to evaluate thermal-hydraulic behavior in fuel debris. In addition, we performed the numerical simulation for the Fukushima Daiichi Nuclear Power Plant unit 2 under the condition in which water injection stopped. And we compared the analysis results by the modified ACE-3D with more detailed three-dimensional CFD results by JUPITER.

Validation of ATDMs at early after the lF accident using air dose rate estimated by airborne concentration and surface deposition density

Moriguchi, Yuichi*; Sato, Yosuke*; Morino, Yu*; Goto, Daisuke*; Sekiyama, Tsuyoshi*; Terada, Hiroaki; Takigawa, Masayuki*; Tsuruta, Haruo*; Yamazawa, Hiromi*

KEK Proceedings 2021-2, p.21 - 27, 2021/12

no abstracts in English

Evaluation of the characteristics of metal nitrate aqueous solutions by microwave heating and the morphologies of synthesized metal oxide powders

Segawa, Tomoomi; Kawaguchi, Koichi; Ishii, Katsunori; Suzuki, Masahiro; Fukasawa, Tomonori*; Fukui, Kunihiro*

Funtai Kogakkai-Shi, 57(9), p.485 - 494, 2020/09

In the spent fuel reprocessing process, a mixed solution of uranyl nitrate and plutonium nitrate is converted into mixed oxide powder by the microwave heating. To evaluate the applicability to the industrial-scale and acquire the characteristics data of the microwave heating denitration of various metal nitrate aqueous solutions based on the knowledge studied in the development of laboratory-scale basic experiments, the microwave heating characteristics and metal oxide powder properties were investigated using cerium nitrate, cobalt nitrate and copper nitrate aqueous solutions. The progress rate of the denitration reaction was depended on the position, and the denitration reaction proceeded faster at the periphery than at the center. The morphologies of the synthesized products were porous and hard dry solid with cerium nitrate aqueous solution, foamed dry solid with cobalt nitrate aqueous solution, and powdery particles with copper nitrate aqueous solution. The denitration ratio and average particle size of the synthesized products increased in the order of the cerium nitrate aqueous solution, the cobalt nitrate aqueous solution, and the copper nitrate aqueous solution. The numerical simulations revealed that the periphery of the bottom surface of the metal nitrate aqueous solution was heated by microwaves. This results consistent with the experimental results in which the denitration reaction started from the periphery of the metal nitrate aqueous solution.

Preparation of Computational Science Simulation Code SPLICE for Laser Manufacturing Process; Research activities on FY2019

Muramatsu, Toshiharu

JAEA-Research 2019-008, 111 Pages, 2019/11

JAEA-Research-2019-008.pdf:8.64MB

A general-purpose three-dimensional thermohydraulics numerical simulation code SPLICE (residual Stress control using Phenomenological modeling for Laser welding repair process In Computational Environment) was designed to deal with gas-liquid-solid consolidated incompressible viscous flows with a phase change process in various laser applications. Main features of the SPLICE code are as follows: (1) A multi-scale model is used to simulate complicated phenomena, such as welding to solidification of metal materials, thermal and mechanical interactions among gas, liquid and solid phases, etc., (2) SPLICE code is applicable for the evaluation of welding, cutting, piercing, coating, additive manufacturing, etc. and (3) A graphic user interface (GUI) is prepared for users to easy utilization of the SPLICE code. This report describes the details of the mathematics, physics, numerics, sample applications of the SPLICE code.

Interpretation of thermal desorption spectra of hydrogen from aluminum using numerical simulation

Ebihara, Kenichi; Yamaguchi, Masatake; Tsuru, Tomohito; Itakura, Mitsuhiro

Keikinzoku, 68(11), p.596 - 602, 2018/11

Hydrogen embrittlement (HE) is considered as one cause of stress corrosion cracking. HE is a serious problem in the development of high strength aluminum alloy as with steels. For understanding HE, it is inevitable to know hydrogen trapping states in the alloys and it can be identified using thermal desorption spectrometry of H. In this study, we numerically simulated thermal desorption spectra of hydrogen in aluminum for a cylindrical and a plate specimens and interpreted the desorption peaks included in them on the basis of the trap site concentration and the trap energy. As a result, we found that the peak at the lowest-temperature side can result from grain boundaries and confirmed that the reported interpretation for other peaks is reasonable. We also obtained the result showing the possibility that the trap site concentration of defects changes during heating the specimens. This result may give a suggestion for the interpretation of temperature desorption spectra of steels.