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Abe, Yosuke; Kubo, Atsushi; Ukai, Shigeharu; Tsuru, Tomohito
Journal of Nuclear Materials, 618, p.156221_1 - 156221_11, 2026/01
Understanding the stability of Cr-rich precipitates (CrRPs) is key to developing radiation-resistant ODS Fe-Cr-Al alloys. This study uses first-principles-based equilibrium Monte Carlo simulations to assess how Al content and irradiation-induced vacancies affect CrRP formation and atomic-scale structure. CrRP formation peaks at around 12 at.% Al, showing a non-monotonic trend. Higher Al levels cause segregation at CrRP-matrix interfaces and internal Al incorporation, leading to structural disorder and reduced stability. Vacancies alone have limited impact but co-segregate with Al near interfaces, potentially affecting diffusion and interfacial integrity under irradiation. These findings provide atomic-level insights for designing advanced Fe-Cr-Al alloys and guiding mesoscale modeling.
Hirota, Noriaki; Takeda, Ryoma; Ide, Hiroshi; Tsuchiya, Kunihiko; Kobayashi, Yoshinao*
Nuclear Materials and Energy (Internet), 45, p.102009_1 - 402009_10, 2025/12
Using SUS304L stainless steel, which is employed in reactor structural components, the effects of grain refinement on stress corrosion cracking occurring under nuclear reactor operating conditions were investigated. As a result, after conducting slow strain rate testing (SSRT) in air and nuclear reactor operating environments, a comparison of the tensile properties of SUS304L with the same grain size revealed that elongation significantly decreased with increasing grain size under nuclear reactor operating conditions. In SSRT conducted in air, the 
-value obtained from the Hall-Petch relationship was lower than the conventional values. Observations showed the absence of cracks on SUS304L with 0.59 and 1.52 
m grains; however, SUS304L with larger grains exhibited rougher fracture surfaces and side cracks. Thin oxide films were formed on SUS304L with 0.59 m and 1.52 m grains, while SUS304L with coarse grains of 28.4 m or larger enabled the formation of oxide films with over 2 m thickness. Cr
O
films were formed on SUS304L with 0.59 m, 1.52 m, and 28.4 m, while CrO and Fe based oxides were formed on SUS304L with 39.5 m and 68.6 m. Crystal orientation analysis revealed linear surface layers without cracks in the 
-phase for SUS304L with 0.59 m and 1.52 m. In materials with Larger grain sizes, surface irregularities and cracks were observed in the -phase. In fine-grained SUS304L, lattice diffusion caused uniform O diffusion in the -phase, resulting in the formation of a thin CrO layer that suppressed cracks. In coarse-grained SUS304L, grain boundary diffusion caused Fe oxide formation at the grain boundaries, weakening them, and supersaturated O led to the formation of thick films comprising CrO and Fe-based oxides, resulting in peeling and cracking.
Odaira, Naoya*; Kodama, Katsuaki; Ito, Daisuke*; Saito, Yasushi*; Parker, J. D.*; Shinohara, Takenao
Nuclear Materials and Energy (Internet), 45, p.102005_1 - 102005_7, 2025/12
Yuhara, Junji*; Maeda, Shota*; Katsube, Daiki*; Suzuki, Seiya; Terasawa, Tomoo; Takakura, Shoichi*; Nakatake, Masashi*; Le Lay, G.*
2D Materials (Internet), 12(4), p.045023_1 - 045023_10, 2025/10
Suzuki, Kazuya; Kubota, Takahide*; Takanashi, Koki
APL Materials (Internet), 13(10), p.101108_1 - 101108_6, 2025/10
The structural, magnetic, and magneto-transport properties of ferromagnetic FeCoNiCuPd high-entropy alloy (HEA) thin films were investigated to assess the role of the heavy element Pd in magneto-transport. The FeCoNiCuPd films with varying composition ratios of Cu and Pd were fabricated by a co-sputtering process at ambient temperature, and the resulting films exhibited a face-centered cubic structure with a homogenous single phase. All the films exhibited ferromagnetic hysteresis curves with soft magnetic behavior at room temperature. The dependence of the anisotropic magnetoresistance effect and anomalous Hall effect on Pd suggests that heavy metals with large spin-orbit interactions play an important role in the magneto-transport of magnetic HEAs. This finding will facilitate the understanding of the magneto-transport phenomenon in magnetic HEAs for future spintronic materials.
Vauchy, R.; Horii, Yuta; Hirooka, Shun; Akashi, Masatoshi; Sunaoshi, Takeo*; Nakamichi, Shinya; Saito, Kosuke
Journal of Nuclear Materials, 616, p.156115_1 - 156115_16, 2025/10
Jeong, S. G.*; Kwon, J.*; Kim, E. S.*; Prasad, K.*; Harjo, S.; Gong, W.; Kawasaki, Takuro; Estrin, Y.*; Bouaziz, O.*; Hong, S. I.*; et al.
Materials Science & Engineering A, 942, p.148712_1 - 148712_11, 2025/10
Okumura, Masahiko
Journal of Electronic Materials, 54(9), p.7015 - 7026, 2025/09
The machine learning molecular dynamics (MLMD) method enables simulations with high prediction accuracy at low computational cost by learning the results of first-principles calculations (quantum mechanical calculations) using artificial neural networks. This presentation will show how machine-learning molecular dynamics can simulate materials with complex structures. Our MLMD simulations succeeded in reproducing the experimental results of the phonon spectrum of the hydroxy groups of a clay mineral (kaolinite), the superionic transition of thorium dioxide, and the medium-range ordered structure of silica glass, which are difficult to accurately evaluate using other simulation methods, such as classical molecular dynamics.
Takahashi, Yoshio*; Miura, Hikaru*; Yamada, Shinya*; Sekizawa, Oki*; Nitta, Kiyofumi*; Hashimoto, Tadashi*; Yomogida, Takumi; Yamaguchi, Akiko; Okada, Shinji*; Itai, Takaaki*; et al.
Journal of Hazardous Materials, 495, p.139031_1 - 139031_19, 2025/09
In this presentation, we analyzed the chemical state of cesium in radiocesium-bearing microparticles (CsMPs) released during the 2011 Fukushima Daiichi Nuclear Power Plant accident using high-resolution X-ray absorption spectroscopy (XANES) and micro X-ray fluorescence (-XRF). The results identified two forms of cesium: one dissolved in glass and the other enriched on the surfaces of internal voids. The latter is considered to have originally existed as a gas and became concentrated during the cooling and solidification of the molten glass. These findings are crucial for understanding the formation process of CsMPs during the accident, as well as for future decommissioning and safety assessments.
Mn
N and Fe
Co
N filmsYin, W.*; Ito, Keita*; Tsubowa, Yusuke*; Tsujikawa, Masahito*; Shirai, Masafumi*; Umetsu, Rie*; Takanashi, Koki
Journal of Magnetism and Magnetic Materials, 628, p.173157_1 - 173157_8, 2025/09
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)
neutron diffraction studyYamashita, Takayuki*; Koga, Norimitsu*; Mao, W.*; Gong, W.; Kawasaki, Takuro; Harjo, S.; Fujii, Hidetoshi*; Umezawa, Osamu*
Materials Science and Engineering A, 941, p.148602_1 - 148602_11, 2025/09
Times Cited Count：0 Percentile：0.00(Nanoscience & Nanotechnology)Cao, T.*; Wei, D.*; Gong, W.; Kawasaki, Takuro; Harjo, S.; 10 of others*
Materials Science and Engineering A, 940, p.148534_1 - 148534_16, 2025/09
Times Cited Count：0Karimi, V.*; Qvistgaard, C. H.*; Schmidt, S.*; Wolfertz, A.*; Parker, J. D.*; Kai, Tetsuya; Hayashida, Hirotoshi*; Shinohara, Takenao; Angelis, S. D.*; Tengattini, A.*; et al.
ACS Applied Materials & Interfaces, 17(36), p.50742 - 50752, 2025/08
Times Cited Count：0 Percentile：0.00Kubota, Takahide*; Suzuki, Kazuya; Hirayama, Yoshiyuki*; Takahashi, Shigeki*; Takanashi, Koki
Physical Review Materials (Internet), 9(8), p.084408_1 - 084408_7, 2025/08
Mochizuki, Akihito; Matsui, Hiroya; Nakayama, Masashi; Sakamoto, Ryo*; Shibata, Masahito*; Motoshima, Takayuki*; Jo, Mayumi*
Case Studies in Construction Materials, 22, p.e04648_1 - e04648_20, 2025/07
Times Cited Count：0 Percentile：0.00(Construction & Building Technology)The properties of low-pH cement used in the geological disposal of radioactive waste may change through atmospheric carbonation and degradation caused by groundwater during the long-term operation of a repository. In this study, we investigated the effects of atmospheric carbonation and groundwater contact on the chemical, microstructural, and transport properties of shotcrete made from low-pH, high-fly-ash silica-fume cement (HFSC) over a period of 16 years in an underground research laboratory. In both carbonated and degraded zones of the HFSC shotcrete, capillary porosity increased for pores of 
300 nm in diameter, and the total porosity was higher than in undegraded zones. These changes in porosity may be associated with the decalcification of calcium-silicate-hydrate and decomposition of ettringite. Such changes were minor in altered zones of OPC shotcrete, indicating that HFSC shotcrete is less resistant to atmospheric carbonation and groundwater leaching under the studied conditions. However, the hydraulic conductivity in HFSC was low enough to fulfill the specific functional requirements of low-pH cements for geological disposal.
Gu, G. H.*; Jeong, S. G.*; Heo, Y.-U.*; Harjo, S.; Gong, W.; Cho, J.*; Kim, H. S.*; 4 of others*
Journal of Materials Science & Technology, 223, p.308 - 324, 2025/07
Times Cited Count：1 Percentile：67.80(Materials Science, Multidisciplinary)Kawai, Yusaku*; Park, J.*; Motokawa, Ryuhei; Ikura, Ryohei*; Murayama, Shunsuke*; Yamaoka, Kenji*; Fujii, Yoshihisa*; Ikemoto, Yuka*; Tanaka, Masaru*; Matsuba, Go*; et al.
ACS Applied Polymer Materials (Internet), 7(12), p.7767 - 7776, 2025/06
Tonna, Ryutaro*; Sasaki, Takayuki*; Okamoto, Yoshihiro; Kobayashi, Taishi*
Journal of Nuclear Materials, 612, p.155820_1 - 155820_11, 2025/06
The dissolution behavior of (U,Zr)O, the primary uranium solid phase in the fuel debris from the Fukushima Daiichi nuclear power plant accidents, was investigated thermodynamically and kinetically under atmospheric conditions. Cubic (U,Zr)O samples with a uniform solid solution of Zr were prepared using wet chemistry methods, and static batch immersion tests were conducted. In strongly acidic conditions, where the solubility of U and Zr exceeded their concentrations, congruent dissolution of both elements was observed with (U,Zr)O dissolving at the same rate as UO. In moderately acidic conditions, where the U solubility was higher than its concentration with Zr reaching a steady state at lower solubility, the U dissolution rate from (U,Zr)O decreased compared to UO. In the presence of oxalic acid, with increased Zr solubility due to the formation of complexes, the U dissolution rate from (U,Zr)O did not decrease. This indicates that Zr in (U,Zr)O formed a secondary solid phase on the solid surface under conditions of lower Zr solubility, which in turn suppressed the oxidative dissolution of U.
Karube, Kosuke*; Onuki, Yoshichika*; Nakajima, Taro*; Chen, H.-Y.*; Ishizuka, Hiroaki*; Kimata, Motoi*; Ohara, Takashi; Munakata, Koji*; Nomoto, Takuya*; Arita, Ryotaro*; et al.
npj Quantum Materials (Internet), 10, p.55_1 - 55_9, 2025/06
Auh, Y. H.*; Neal, N. N.*; Arole, K.*; Regis, N. A.*; Nguyen, T.*; Ogawa, Shuichi*; Tsuda, Yasutaka; Yoshigoe, Akitaka; Radovic, M.*; Green, M. J.*; et al.
ACS Applied Materials & Interfaces, 17(21), p.31392 - 31402, 2025/05
Times Cited Count：0 Percentile：0.00(Nanoscience & Nanotechnology)