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Aoki, Takeshi; Shimizu, Atsushi; Ishii, Katsunori; Morita, Keisuke; Mizuta, Naoki; Kurahayashi, Kaoru; Yasuda, Takanori; Noguchi, Hiroki; Nomoto, Yasunobu; Iigaki, Kazuhiko; et al.
Annals of Nuclear Energy, 220, p.111503_1 - 111503_7, 2025/09
Times Cited Count：0Aiming to establish coupling technologies between a high temperature gas cooled reactor and a hydrogen production plant, JAEA has initiated the HTTR Heat Application Test Project and is conducting the safety design and the safety analysis for the licensing of the HTTR Heat Application Test Facility. The present study proposed a relative evaluation methodology for the demarcation of applicable laws and design standards for the nuclear hydrogen production system and applied it to the HTTR Heat Application Test Facility. The evaluation results showed that a candidate applying the High Pressure Gas Safety Act to the Heat Application Test Facility (hydrogen production plant) and design standards established under the High Pressure Gas Safety Act to the steam reformer did not show the lowest category in any of the metrics, and was proposed as the most superior demarcation option for the HTTR Heat Application Test Facility.
(Al, Zn)
Approximant crystal; Influence of chemical disorderShimizu, Kazuyuki*; Yamaguchi, Masatake; Akamaru, Satoshi*; Nishimura, Katsuhiko*; Abe, Rion*; Sasaki, Taisuke*; Wang, Y.*; Toda, Hiroyuki*
Scripta Materialia, 265, p.116730_1 - 116730_7, 2025/08
Times Cited Count：0Ebihara, Kenichi; Fujihara, Hiro*; Shimizu, Kazuyuki*; Yamaguchi, Masatake; Toda, Hiroyuki*
International Journal of Hydrogen Energy, 136, p.751 - 756, 2025/06
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.
Shimizu, Kazuyuki*; Toda, Hiroyuki*; Hirayama, Kyosuke*; Fujihara, Hiro*; Tsuru, Tomohito; Yamaguchi, Masatake; Sasaki, Taisuke*; Uesugi, Masayuki*; Takeuchi, Akihisa*
International Journal of Hydrogen Energy, 109, p.1421 - 1436, 2025/03
Times Cited Count：2 Percentile：88.09(Chemistry, Physical)Our preceding investigation revealed that multiple hydrogen traps at coherent interfaces of MgZn
precipitates initiated spontaneous interface decohesion, causing hydrogen-induced quasicleavage cracking in Al-Zn-Mg alloys. Herein, we performed a quantitative and systematic investigation to discern the mechanisms by which hydrogen trapped at coherent/semi-coherent interfaces of precipitates could influence macroscopic hydrogen embrittlement by modulating the coherent interface of MgZn through aging. To explore this hydrogen embrittlement phenomenon based on hydrogen trapping at the precipitate interface, we determined the hydrogen trapping energy of the semi-coherent MgZn interface via first-principles calculations (0.56 eV/atom). Hydrogen partitioning of all hydrogen trapping sites, including vacancies, grain boundaries, and coherent and semi-coherent MgZn interfaces, revealed that in overaged alloys, over 90% of the hydrogen was sequestered at semi-coherent interfaces. Owing to the inherent characteristics of the MgZn interface, the hydrogen sequestered at the semi-coherent interface decreased the interfacial cohesive energy, causing semispontaneous decohesion of the interface and quasicleavage fracture in the Al-Zn-Mg alloys. These results implied that intergranular fracture was not directly induced by hydrogen trapped at grain boundaries but rather by the decohesion of precipitate interfaces along grain boundaries.
rays in the 
La(
)
La reactionOkuizumi, Mao*; Auton, C. J.*; Endo, Shunsuke; Fujioka, Hiroyuki*; Hirota, Katsuya*; Ino, Takashi*; Ishizaki, Kohei*; Kimura, Atsushi; Kitaguchi, Masaaki*; Koga, Jun*; et al.
Physical Review C, 111(3), p.034611_1 - 034611_6, 2025/03
Times Cited Count：0 Percentile：0.00(Physics, Nuclear)Shimizu, Kazuyuki*; Nishimura, Katsuhiko*; Matsuda, Kenji*; Nunomura, Norio*; Namiki, Takahiro*; Tsuchiya, Taiki*; Akamaru, Satoshi*; Lee, S.*; Tsuru, Tomohito; Higemoto, Wataru; et al.
International Journal of Hydrogen Energy, 95, p.292 - 299, 2024/12
Times Cited Count：1 Percentile：31.33(Chemistry, Physical)Zero-field muon spin relaxation experiments were conducted on Al-0.06%Mn, Al-0.06%Cr, Al-0.02%Fe, and Al-0.02%Ni alloys (at.%) across the temperature ranging from 5 to 300 K. The temperature-dependent variations of the dipole field widths (
) elucidated four distinct peaks for the prepared alloys. Atomic configurations of the muon trapping sites corresponding to the observed peaks below 200 K were meticulously characterized utilizing first-principles calculations for the trapping energies of hydrogen in proximity to a solute and solute-vacancy pair. This comprehensive analysis facilitated the establishment of a linear correlation between the muon peak temperature and the hydrogen trapping energy. However, significant deviations from this linear relationship were observed for the fourth peaks above 200 K in Al-Mn, Al-Cr, Al-Fe, and Al-Ni alloys. This discrepancy can be interpreted by considering the disparate distribution functions of muon and hydrogen within the tetrahedral site, wherein two of the four Al atoms are substituted by the solute element and vacancy (solute-vacancy pair).
Morita, Keisuke; Aoki, Takeshi; Shimizu, Atsushi; Sato, Hiroyuki
Proceedings of 31st International Conference on Nuclear Engineering (ICONE31) (Internet), 6 Pages, 2024/11
Aoki, Takeshi; Hasegawa, Takeshi; Kurahayashi, Kaoru; Nomoto, Yasunobu; Shimizu, Atsushi; Sato, Hiroyuki; Sakaba, Nariaki
Proceedings of 11th International Topical Meeting on High Temperature Reactor Technology (HTR 2024), 6 Pages, 2024/10
Japan Atomic Energy Agency (JAEA) is planning to perform a test named HTTR heat application test coupling HTTR (High temperature engineering test reactor) and a hydrogen production plant. The present study reports results of the safety design and safety analysis for HTTR heat application test facility. As a safety design, safety classification of structures, systems, and components was defined in the test facility based on their safety functions. As a preliminary safety analysis, a thermal-hydraulic analysis was performed with RELAP5 code. The safety analysis revealed that newly identified events for HTTR heat application test facility except for the rupture of heat transfer tube of steam generator was enveloped by the licensing basis events in conventional HTTR. The preliminary analysis proved that the safety criteria is satisfied in the candidate of licensing basis event.
Ito, Shinji*; Shimizu, Hiroyuki*; Ono, Shintaro*; Takayama, Yusuke
Doboku Gakkai Rombunshu (Internet), 80(8), p.24-00030_1 - 24-00030_18, 2024/08
In the design consideration of a geological disposal facility for radioactive waste, it is essential to perform a mechanical evaluation that takes into account phenomena that may occur from construction and operation to post-closure. With this background, we have developed the long-term mechanical analysis system MACBECE. In this research, we have built an analysis system that can consistently evaluate the mechanical behavior considering the thermal and hydraulic evolution after the closure of the repository by incorporating the constitutive model for unsaturated soils and coupling with the thermal-hydraulic analysis. As a validation, a mechanical analysis was conducted for the in-situ experiment for full-scale engineered barrier system performance experiment at Horonobe URL. Despite some discrepancies due to constraints in two-dimensional analysis, the extended functionality of the analysis code was confirmed to effectively repro-duce the measured data.
Endo, Shunsuke; Abe, Ryota*; Fujioka, Hiroyuki*; Ino, Takashi*; Iwamoto, Osamu; Iwamoto, Nobuyuki; Kawamura, Shiori*; Kimura, Atsushi; Kitaguchi, Masaaki*; Kobayashi, Ryuju*; et al.
European Physical Journal A, 60(8), p.166_1 - 166_10, 2024/08
Times Cited Count：2 Percentile：78.45(Physics, Nuclear)Nagatsuka, Kentaro; Noguchi, Hiroki; Nagasumi, Satoru; Nomoto, Yasunobu; Shimizu, Atsushi; Sato, Hiroyuki; Nishihara, Tetsuo; Sakaba, Nariaki
Nuclear Engineering and Design, 425, p.113338_1 - 113338_11, 2024/08
Times Cited Count：4 Percentile：93.24(Nuclear Science & Technology)HTGR has a potential to contribute to decarbonization of hard-to-abate industries by supplying a large amount of hydrogen and high temperature heat or steam without carbon dioxide emission. JAEA has been conducting R&Ds for HTGR technologies with High Temperature Engineering Test Reactor (HTTR). This paper shows that HTTR's tests including the loss of core cooing test as a joint the OECD/NEA international research project and a HTTR heat application test plan which demonstrate hydrogen production by coupling the HTTR with a hydrogen production test facility. Additionally, aiming for operation start from the latter half of 2030s, the basic design of the HTGR demonstration reactor has been shown. The Japan's HTGR technology capabilities established by the HTTR project will be fully utilized for the construction of HTGR demonstration reactor.
-phase in Al-Mg-Si alloys during aging treatmentAhmed, A.*; Uttarasak, K.*; Tsuchiya, Taiki*; Lee, S.*; Nishimura, Katsuhiko*; Nunomura, Norio*; Shimizu, Kazuyuki*; Hirayama, Kyosuke*; Toda, Hiroyuki*; Yamaguchi, Masatake; et al.
Journal of Alloys and Compounds, 988, p.174234_1 - 174234_9, 2024/06
Times Cited Count：10 Percentile：96.31(Chemistry, Physical)This study aims to clarify the growth process of the-phase in Al-Mg-Si alloys from the point of view of morphology evolution. For this research, the -phase orientation relationship, shape, growth process, misfit value, and interfacial condition between the -phase and Al matrix were investigated using high-resolution transmission electron microscopy (HR-TEM), focus ion beam (FIB), and optical microscope (OM). Results include the identification of {111} facets at the edges of the -phase, as well as the proposal of two new three-dimensional shapes for the -phase. We purposed the morphology evolution during the growth process of Mg
Si crystal and calculated the misfit to understand the unstable (111) facet has a higher misfit value as compared to the (001) and (011) facets. Our observations provide how they influence the behavior of MgSi crystals.
MnShimizu, Kazuyuki*; Nishimura, Katsuhiko*; Matsuda, Kenji*; Akamaru, Satoshi*; Nunomura, Norio*; Namiki, Takahiro*; Tsuchiya, Taiki*; Lee, S.*; Higemoto, Wataru; Tsuru, Tomohito; et al.
Scripta Materialia, 245, p.116051_1 - 116051_6, 2024/05
Times Cited Count：2 Percentile：63.37(Nanoscience & Nanotechnology)Hydrogen at the mass ppm level causes hydrogen embrittlement in metallic materials, but it is extremely difficult to experimentally elucidate the hydrogen trapping sites. We have taken advantage of the fact that positive muons can act as light isotopes of hydrogen to study the trapping state of hydrogen in matter. Zero-field muon spin relaxation experiments and the density functional theory (DFT) calculations for hydrogen trapping energy are carried out for AlMn. The DFT calculations for hydrogen in AlMn have found four possible trapping sites in which the hydrogen trapping energies are 0.168 (site 1), 0.312 (site 2), 0.364 (site 3), and 0.495 (site 4) in the unit of eV/atom. Temperature variations of the deduced dipole field width () indicated step-like changes at temperatures, 94, 193, and 236 K. Considering their site densities, the observed change temperatures are interpreted by trapping muons at sites 1, 3, and 4.
-odd/
-odd interactions on the 0.75 eV 
-wave resonance in 
+
forward transmission determined using a pulsed neutron beamNakabe, Rintaro*; Auton, C. J.*; Endo, Shunsuke; Fujioka, Hiroyuki*; Gudkov, V.*; Hirota, Katsuya*; Ide, Ikuo*; Ino, Takashi*; Ishikado, Motoyuki*; Kambara, Wataru*; et al.
Physical Review C, 109(4), p.L041602_1 - L041602_4, 2024/04
Times Cited Count：1 Percentile：23.17(Physics, Nuclear)-wave resonance of 
+
Okudaira, Takuya*; Nakabe, Rintaro*; Auton, C. J.*; Endo, Shunsuke; Fujioka, Hiroyuki*; Gudkov, V.*; Ide, Ikuo*; Ino, Takashi*; Ishikado, Motoyuki*; Kambara, Wataru*; et al.
Physical Review C, 109(4), p.044606_1 - 044606_9, 2024/04
Times Cited Count：2 Percentile：78.45(Physics, Nuclear)Fujihara, Hiro*; Toda, Hiroyuki*; Ebihara, Kenichi; Kobayashi, Masakazu*; Mayama, Tsuyoshi*; Hirayama, Kyosuke*; Shimizu, Kazuyuki*; Takeuchi, Akihisa*; Uesugi, Masayuki*
International Journal of Plasticity, 174, p.103897_1 - 103897_22, 2024/03
Times Cited Count：8 Percentile：94.71(Engineering, Mechanical)Hydrogen(H) embrittlement in high-strength aluminum(Al) alloys is a crucial problem. H accumulation at the interface of precipitates in Al alloy is considered to cause embrittlement. However, there is no quantitative knowledge regarding the interaction between H distribution and stress field near cracks. In this study, using a multi-modal three-dimensional image-based simulation combining the crystal plasticity finite element method and H diffusion analysis, we tried to capture the stress distribution near the crack, its influence on the H distribution, and the probability of crack initiation in the experimental condition. As a result, it was found that grain boundary cracks transition to quasi-cleavage cracks in the region where the cohesive energy of the semi-coherent interface of MgZn precipitates decreases due to H accumulation near the tip. We believe the present simulation method successfully bridges nanoscale delamination and macroscale brittle fracture.
Tang, J.*; Wang, Y.*; Fujihara, Hiro*; Shimizu, Kazuyuki*; Hirayama, Kyosuke*; Ebihara, Kenichi; Takeuchi, Akihisa*; Uesugi, Masayuki*; Toda, Hiroyuki*
Scripta Materialia, 239, p.115804_1 - 115804_5, 2024/01
Times Cited Count：11 Percentile：82.25(Nanoscience & Nanotechnology)Stress corrosion cracking (SCC) behaviors induced by the combination of external and internal hydrogen (H) in an Al-Zn-Mg-Cu alloy were systematically investigated via in situ 3D characterization techniques. SCC of the Al-Zn-Mg-Cu alloy could initiate and propagate in the potential crack region where the H concentration exceeded a critical value, in which the nanoscopic H-induced decohesion of 
-MgZn precipitates resulted in macroscopic cracking. External H that penetrated the alloy from the environment played a crucial role during the SCC of the Al-Zn-Mg-Cu alloy by generating gradient-distributed H-affected zones near the crack tips, which made Al alloys in water environment more sensitive to SCC. Additionally, the pre-existing internal H was driven toward the crack tips during plastic deformation. It was involved in the SCC and made contributions to both the cracks initiation and propagation.
Ga K-edge XANES study of Ga-exchanged zeolites at high temperatures under different atmospheres including vacuum, CO, and pressurized HHuang, M.*; Kinjo, Tetsuya*; Yasumura, Shunsaku*; Toyao, Takashi*; Matsumura, Daiju; Saito, Hiroyuki*; Shimizu, Kenichi*; Namiki, Norikazu*; Maeno, Zen*
Catalysis Science & Technology, 13(23), p.6832 - 6838, 2023/12
Times Cited Count：0 Percentile：0.00(Chemistry, Physical)Ishii, Katsunori; Morita, Keisuke; Noguchi, Hiroki; Aoki, Takeshi; Mizuta, Naoki; Hasegawa, Takeshi; Nagatsuka, Kentaro; Nomoto, Yasunobu; Shimizu, Atsushi; Iigaki, Kazuhiko; et al.
Dai-27-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu (Internet), 4 Pages, 2023/09
Shimizu, Kazuyuki*; Toda, Hiroyuki*; Fujihara, Hiro*; Yamaguchi, Masatake; Uesugi, Masayuki*; Takeuchi, Akihisa*; Nishijima, Masahiko*; Kamada, Yasuhiro*
Corrosion, 79(8), p.818 - 830, 2023/08
Times Cited Count：5 Percentile：46.68(Materials Science, Multidisciplinary)7xxx aluminum alloys are representative high-strength aluminum alloys; however, mechanical property degradation due to hydrogen hinders further strengthening. We propose the dispersion of Mn-based second-phase particles as a novel technique for preventing 7xxx aluminum alloy hydrogen embrittlement. In this study, the deformation and fracture behaviors of high hydrogen 7xxx alloys containing 0.0% Mn and 0.6% Mn are observed in situ using synchrotron radiation X-ray tomography. The obtained macroscopic hydrogen embrittlement is quantitatively analyzed based on hydrogen partitioning in alloys. Adding 0.6% Mn, generating second-phase particles with high hydrogen trapping abilities, significantly suppresses hydrogen-induced quasicleavage fracture.
