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Uesawa, Shinichiro; Maeshima, Takahiro*; Okada, Makoto*; Tomita, Hirobumi*; Tate, Naofumi*; Aoki, Kunitomo*; Hiramatsu, Natsuki*; Ono, Koji*; Yoshida, Hiroyuki
Konsoryu Shimpojiumu 2026 Koen Rombunshu (Internet), 2 Pages, 2026/08
To use detailed two-phase flow simulations as an alternative or complement to large-scale mockup experiments, quantitative validation of instantaneous and local gas-liquid interfacial information is required in addition to flow-regime reproducibility. However, conventional wire-mesh sensors (WMSs) cannot measure void fraction distributions at a spatial resolution finer than the wire-crossing interval. To overcome this limitation, we are developing a technique to estimate high accurate, high-resolution void fraction distributions from WMS signals by combining WMS measurements, detailed two-phase flow simulations, electrostatic field analysis, and generative AI. This presentation reports on the development status of a Pix2Pix-based model and its application to experimentally obtain WMS signals in a 3
3 rod-bundle channel.
-iron at high pressures determined using 
neutron diffractionAoki, Katsutoshi*; Takano, Masahiro*; Fukuyama, Ko*; Kagi, Hiroyuki*; Machida, Akihiko*; Saito, Hiroyuki*; Hattori, Takanori; Sano, Asami; Funakoshi, Kenichi*
Physical Review B, 113(18), p.184440_1 - 184440_6, 2026/05
Times Cited Count：1 Percentile：78.36(Materials Science, Multidisciplinary)The temperature dependence of the magnetic moment of bcc -iron was investigated over the range 300-950 K at pressures of approximately 2 and 6 GPa by neutron powder diffraction. The 
Fe isotope, whose neutron scattering length is approximately half that of naturally abundant Fe, was employed to enhance the relative contribution of magnetic scattering. Curie temperatures (
) were determined to be 946(30) K, 838(50) K and 740(40) K at 2.1, 6.0 and 6.7 GPa, respectively, defining a magnetic phase boundary described by (K) = 1043 - 49(7)
+ 1.3(1.2)
. Upon heating at 6.7 GPa, the 
structural transition was observed to follow the magnetic transition. This transition sequence indicates that the magnetic phase boundary lies on the low-temperature side of the phase boundary. Accordingly, the transition corresponds to a structural transformation from paramagnetic bcc to paramagnetic fcc iron.
Takano, Masahiro*; Kagi, Hiroyuki*; Mori, Yuichiro*; Kobayashi, Hiroki*; Aoki, Katsutoshi*; Takahashi, Yoshio*; Ijichi, Yuta*; Kakizawa, Sho*; Tsujino, Noriyoshi*; Higo, Yuji*; et al.
ACS Earth and Space Chemistry (Internet), 10(4), p.1047 - 1061, 2026/04
Times Cited Count：2 Percentile：81.81(Chemistry, Multidisciplinary)Iron monosulfide (FeS) is an important sulfide phase in planetary materials and has been proposed as a potential host of hydrogen in planetary interiors. However, hydrogen solubility in FeS at high pressure and temperature remains debated. In this study, hydrogen incorporation in the NiAs-type FeS phase (FeS V) was reexamined using synchrotron X-ray absorption spectroscopy, in situ X-ray and neutron diffraction, and first-principles calculations. The experimental results indicate that the volume expansion observed under hydrogen-saturated conditions is explained by the reduction of Fe
to Fe
and a decrease in the 
value of Fe-deficient Fe
S, rather than hydrogen incorporation into the lattice. These results suggest that hydrogen incorporation in FeS is extremely limited, with an upper bound of approximately 200 ppm up to 30 GPa.
Marium, M.*; Aoki, Kentaro*; He, Y.*; Yamamoto, Katsuhiro*; Suwansoontorn, A.*; Ikuta, Seiya*; Hara, Mitsuo*; Nagano, Shusaku*; Nagao, Yuki*; Nishikawa, Kei*; et al.
ACS Applied Energy Materials (Internet), 8(22), p.16589 - 16600, 2025/11
Times Cited Count：1 Percentile：20.13(Chemistry, Physical)
meson spectrum through kaons in proton-nucleus reactionsBalassa, G.*; Aoki, Kazuya*; Gubler, P.; Lee, S. H.*; Sako, Hiroyuki; Wolf, G.*
Progress of Theoretical and Experimental Physics (Internet), 2025(11), p.113C01_1 - 113C01_20, 2025/11
Times Cited Count：2 Percentile：34.76(Physics, Multidisciplinary)
BHidaka, Hiroyuki*; Yanagisawa, Tatsuya*; Tabata, Chihiro; Kon, Fusako*; Amitsuka, Hiroshi*; Shimizu, Yusei*; Aoki, Dai*
Physical Review B, 112(14), p.144418_1 - 144418_6, 2025/10
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)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：2 Percentile：65.74(Nuclear Science & Technology)Aiming 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.
Tamura, Yukiko*; Arakawa, Masato*; Takenaka, Mikihito*; Nakanishi, Yohei*; Fujinami, So*; Shibata, Motoki*; Yamamoto, Katsuhiro*; Miyata, Noboru*; Yamada, Masako*; Seto, Hideki*; et al.
Polymer, 333, p.128662_1 - 128662_8, 2025/08
Times Cited Count：2 Percentile：19.91(Polymer Science)Taguchi, Miki*; Miyata, Noboru*; Miyazaki, Tsukasa*; Aoki, Hiroyuki; Ozawa, Satoru*; Hasegawa, Ryuichi*; Morimitsu, Yuma*; Kawaguchi, Daisuke*; Yamamoto, Satoru*; Tanaka, Keiji*
Polymer Journal, 57(7), p.737 - 743, 2025/07
Times Cited Count：0 Percentile：0.00(Polymer Science)Liu, Y.*; Miyata, Noboru*; Miyazaki, Tsukasa*; Shundo, Atsuomi*; Kawaguchi, Daisuke*; Tanaka, Keiji*; Aoki, Hiroyuki
ACS Applied Materials & Interfaces, 17(25), p.37311 - 37318, 2025/06
Machida, Akihiko*; Saito, Hiroyuki*; Aoki, Katsutoshi*; Komatsu, Kazuki*; Hattori, Takanori; Sano, Asami; Funakoshi, Kenichi*; Machida, Shinichi*; Sato, Toyoto*; Orimo, Shinichi*
Physical Review B, 111(22), p.224413_1 - 224413_6, 2025/06
Times Cited Count：1 Percentile：24.47(Materials Science, Multidisciplinary)The crystal and magnetic structures of antiferromagnetic Mn deuterides formed by hydrogenating Mn metal at high temperature and high pressure, fcc 
-MnDx and hcp 
-MnDx, were investigated by in-situ neutron powder diffraction. Deuterium atoms partially occupied the octahedral interstitial positions of the fcc and hcp metal lattices. The site occupancies increased rapidly with decreasing temperature from 
700 to 450 K and remained down to 300 K. N
el temperature of 543(10) K was determined for -MnD
. For -MnD
, saturation magnetic moment and Nel temperature were determined to be 0.82(1) 
and 347(3) K, respectively. The Nel temperatures determined for -MnD and -MnD are consistent with those predicted by the respective Slater-Pauling curves proposed in previous studies. The updated Nel temperatures provide insights into the development of more accurate Slater-Pauling curves based on electronic band structure calculations.
Yamazaki, Dai; Maruyama, Ryuji; Aoki, Hiroyuki; Hanashima, Takayasu*; Akutsu-Suyama, Kazuhiro*; Miyata, Noboru*; Soyama, Kazuhiko
Quantum Beam Science (Internet), 9(2), p.20_1 - 20_12, 2025/06
Tanizaki, Shiho*; Kubo, Tomohiro*; Bito, Yosuke*; Mori, Shigeki*; Aoki, Hiroyuki; Sato, Kotaro*
RSC Sustainability (Internet), 3(4), p.1714 - 1720, 2025/04
Aoki, Katsutoshi*; Machida, Akihiko*; Saito, Hiroyuki*; Hattori, Takanori
Koatsuryoku No Kagaku To Gijutsu, 35(1), p.4 - 11, 2025/03
Iron reacts with hydrogen to form solid solutions with body-centered cubic, face-centered cubic, hexagonal close packed, and double hexagonal close packed structures at high temperatures and high pressures. Neutron diffraction is the most powerful tool for determining the occupation sites and occupancies of hydrogen atoms dissolved in a metal lattice. Structural parameters, including hydrogen occupation sites and occupancies, are refined via Rietveld analysis for neutron diffraction data. We present our expertise in Rietveld refinement of iron hydrides accumulated over 10 years.
Horiike, Yuki*; Aoki, Hiroyuki; Ouchi, Makoto*; Terashima, Takaya*
Journal of the American Chemical Society, 147(8), p.6727 - 6738, 2025/02
Times Cited Count：7 Percentile：68.30(Chemistry, Multidisciplinary)Yamamoto, Katsuhiro*; Imai, Tatsuya*; Kawai, Atsuki*; Ito, Eri*; Miyazaki, Tsukasa*; Miyata, Noboru*; Yamada, Norifumi*; Seto, Hideki*; Aoki, Hiroyuki
ACS Applied Materials & Interfaces, 16(48), p.66782 - 66791, 2024/11
Times Cited Count：4 Percentile：14.44(Nanoscience & Nanotechnology)Miyazaki, Tsukasa*; Miyata, Noboru*; Arima-Osonoi, Hiroshi*; Shimokita, Keisuke*; Yamamoto, Katsuhiro*; Takenaka, Mikihito*; Nakanishi, Yohei*; Shibata, Motoki*; Aoki, Hiroyuki; Yamada, Norifumi*; et al.
Colloids and Surfaces A; Physicochemical and Engineering Aspects, 701, p.134928_1 - 134928_8, 2024/11
Times Cited Count：1 Percentile：4.35(Chemistry, Physical), 
, 
and 
mesons through their angular-dependent two-body decay modesPark, I. W.*; Sako, Hiroyuki; Aoki, Kazuya*; Gubler, P.; Lee, S. H.*
Journal of Subatomic Particles and Cosmology (Internet), 1-2, p.100014_1 - 100014_11, 2024/11
Morita, Keisuke; Aoki, Takeshi; Shimizu, Atsushi; Sato, Hiroyuki
Proceedings of 31st International Conference on Nuclear Engineering (ICONE31) (Internet), 6 Pages, 2024/11
Machida, Akihiko*; Saito, Hiroyuki*; Sugimoto, Hidehiko*; Hattori, Takanori; Sano, Asami; Endo, Naruki*; Katayama, Yoshinori*; Iizuka, Riko*; Sato, Toyoto*; Matsuo, Motoaki*; et al.
Nature Communications (Internet), 15, p.8861_1 - 8861_2, 2024/10
Times Cited Count：3 Percentile：95.26(Multidisciplinary Sciences)In our previous article (Nature Commun. 5, 5063 (2014)), the site occupancies of D atoms dissolved in an fcc Fe metal lattice were investigated via Rietveld refinement of neutron powder diffraction patterns collected at 988 K and 6.3 GPa. The fcc metal lattice has two interstitial sites available for accommodating D atoms: octahedral and tetrahedral sites. The Rietveld refinement revealed that D atoms occupied mainly the octahedral sites with occupancy of 0.532 and slightly the tetrahedral sites with occupancy of 0.056. Subsequent density-functional-theory (DFT) calculations by Antonov (Phys. Rev. Mater. 2019)) showed that the occupation energy on the tetrahedral site was significantly higher than that on the octahedral site; the tetrahedral site occupation was unlikely to occur even at temperatures as high as 988 K. We reexamined the site occupancies of D-atom by Rietveld refinement including extinction correction. As a result, the octahedral occupancy was increased to 0.60 and the tetrahedral occupancy was reduced to zero. The occupation of only the octahedral site for D atom is consistent with the DFT calculation, although in contrast to the previous results.
