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alteration phases under chemically complex conditionsMei, H.*; 青柳 登; 高木 聖也; 斉藤 拓巳*
Journal of Hazardous Materials, 514, p.142804_1 - 142804_11, 2026/08
被引用回数：0The study examines how uranium dioxide, a key component of spent nuclear fuel and Fukushima fuel debris, alters under oxidizing conditions relevant to storage and accident environments. Factors such as boric acid, hydrogen peroxide, seawater, and cement leachates were included to simulate realistic chemical conditions. After five months, the alteration products were analyzed using X ray diffraction and cryogenic time resolved laser fluorescence spectroscopy. X-ray diffraction detected only small amounts of metaschoepite in simple systems and failed to identify products in more complex environments. In contrast, cryogenic fluorescence spectroscopy successfully identified uranium six phases in all samples and revealed detailed chemical forms that X ray methods could not detect. Two distinct fluorescent components of uranium were identified, both linked to metaschoepite. The results highlight the importance of advanced spectroscopy methods for detecting subtle uranium phases that control early reactivity and release. These findings improve understanding of uranium behavior in nuclear waste systems and contribute to safer management strategies for Fukushima debris and long term storage of spent nuclear fuel.
O
precursors on solid-state formation reactions of (K
Na)NbO
庄司 琢磨*; Nam, H.*; Ye, J.*; Ito, Daiki*; 高木 優香*; 米田 安宏; 永田 肇*
Journal of the American Ceramic Society, 109(3), p.e70657_1 - e70657_9, 2026/03
被引用回数：1 パーセンタイル：0.00(Materials Science, Ceramics)(K,Na)NbO (KNN)系セラミックスは、優れた圧電特性を有するにもかかわらず、化学的均質性が低いことから、実用的な圧電デバイスへの応用には躊躇されてきた。本研究では、NbO前駆体の役割が製造手法によって異なり、KNNの化学的均質性と強く相関していることを軟X線吸収分光を用いて明らかにした。したがって、NbO前駆体の選択はKNN製造における支配的要因である。
Su, Y. H.; 篠原 武尚; Parker, J. D.*; 及川 健一; 甲斐 哲也; Gong, W.; 伊東 達矢; Harjo, S.; 相澤 一也; 鬼柳 善明*; et al.
Materials Science & Engineering A, 951, p.149607_1 - 149607_16, 2026/01
被引用回数：0 パーセンタイル：0.00(Nanoscience & Nanotechnology)Local variations in residual stress/strain and microstructure during fatigue crack growth in compact tension specimens of SUS304 austenitic stainless steel were investigated using complementary methods: pulsed neutron Bragg-edge imaging (NBEI), neutron diffraction (ND), digital image correlation (DIC) and electron backscatter diffraction (EBSD). Surface strain fields were evaluated using DIC and EBSD. NBEI provided two-dimensional averaged microstructure information, whereas ND yielded detailed three-dimensional distributions of residual lattice (elastic) strain and stress. This study particularly focused on how NBEI is helpful in understanding overall damage characteristics in the vicinity of a crack tip two-dimensionally. Distribution of microstructural parameters associated with crack growth, such as lattice constant, crystallite size, and texture, across the entire specimen was considered using Bragg-edge spectral analysis. The plastic zone in front of the crack tip, characterized by reduced crystallite size, was observed during crack propagation. After final fracture, two distinct zones with reduced crystallite size were identified: one caused by localized plastic deformation near the crack tip, and the other by bending at the back end of the specimen. This paper introduces the four experimental techniques and describes their respective features. Each method has its own advantages and limitations; However, by integrating their results, a more comprehensive understanding of the overall stress/strain field can be achieved.
N(
,
)
O reaction rates via the 
F(,
)
F reactionKim, S. H.*; Chae, K. Y.*; 浅井 雅人; 廣瀬 健太郎; 佐藤 哲也; 牧井 宏之; 西尾 勝久; Orlandi, R.; Smallcombe, J.; 洲嵜 ふみ; et al.
Journal of the Korean Physical Society, 6 Pages, 2026/00
被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)コア崩壊超新星爆発(CCSNe)の元素合成シミュレーションにおいて、N(,)O反応速度の不確実性が課題となっていた。本研究では、この反応を制約するため、JAEAタンデム加速器でF(,)F遷移反応実験を実施した。得られたトリトンスペクトルと角度分布から、関連するF共鳴の崩壊特性(部分幅)を詳細に測定し、その結果を用いて反応速度パラメータを精密化した。これにより、CCSNe核合成モデルの信頼性向上が期待できる。
Yildirim, A. C.*; Mei, H.*; 戸田 賀奈子*; 青柳 登; 斉藤 拓巳*
Applied Clay Science, 274, p.107853_1 - 107853_9, 2025/09
被引用回数：1 パーセンタイル：0.00(Chemistry, Physical)Metakaolin-based geopolymers (MKGPs) are ceramic-like materials used for nuclear waste stabilization. Therefore, understanding the sorption of ions on MKGPs is crucial where the cation exchange is considered as the main mechanism, yet the studies based on pH are limited. Thus, this study evaluates the effect of pH on the sorption mechanism of Eu(III) onto Na- and K-MKGPs. Here, time-resolved laser fluorescence spectroscopy (TRLFS) combined with parallel factor analysis, TRLFS in mixed DO/HO matrices, and extended X-ray absorption fine structure analysis. Eu(III) predominantly forms surface complexes with both MKGPs in the pH range of 4 
11 at the open air environment, where three distinct surface species were identified at different pH values. The Eu(III) sorption mechanisms of both MKGPs are similar, involving ternary edge-sharing bidentate or monodentate inner-sphere surface complexation of Eu(III) with MKGP and silicate ions released from the MKGP up to pH 8, followed by the precipitation of europium tri-hydroxide within the pores of MKGP. The insights gained from this study will enhance the knowledge on MKGP for pollutant immobilization, thereby mitigating the spread of contaminants in the environment and expanding the potential application areas.
Mei, H.; 青柳 登; 斉藤 拓巳*; 田中 万也; 杉浦 佑樹; 舘 幸男
Applied Clay Science, 276, p.107944_1 - 107944_8, 2025/07
被引用回数：4 パーセンタイル：75.87(Chemistry, Physical)Dissolved inorganic carbon (DIC) existing in groundwaters near geological disposal site may affect the migration and fate of released radionuclides (e.g., uranium (U)). However, it is still unclear how DIC affects the sorption of U(VI) on mudstone, a potential choice for host rock formation barriers, and the characteristics of U(VI) adsorption species. In view of this, adsorption of U(VI) on mudstone as a function of pH or the DIC level was investigated through batch adsorption experiments, component additivity (CA) modeling, and parallel factor (PARAFAC) analysis of cryogenic time-resolved laser fluorescence spectroscopy (cryo-TRLFS). The inhibition effect of DIC on adsorption of U(VI) was implied from the batch experimental results. The CA model considering montmorillonite and illite as the main phases responsible for adsorption reflected the variation trend but underestimated the experimental data. Three components were decomposed from the PARAFAC analysis of the cryo-TRLFS data of mudstone and adsorption samples. Based on the spectral shapes, lifetimes, and variation trends, two components were assigned to the intrinsic U(VI) species in the mudstone matrix and the third component to a ternary uranyl-carbonate surface species. The obtained results imply a significant influence of the DIC level on retention and fate of U(VI), which needs to be considered in safety assessment of potential deep geological disposal schemes.
Co
)Sn studied by 
SRCai, Y.*; Yoon, S.*; Sheng, Q.*; Zhao, G.*; Seewald, E. F.*; Ghosh, S.*; Ingham, J.*; Pasupathy, A. N.*; Queiroz, R.*; Lei, H.*; et al.
Physical Review B, 111(21), p.214412_1 - 214412_17, 2025/06
被引用回数：2 パーセンタイル：49.43(Materials Science, Multidisciplinary)We study the magnetic properties of the metallic kagome system (FeCo)Sn by a combination of muon spin relaxation (SR), magnetic susceptibility, and scanning tunneling microscopy (STM) measurements in single crystal specimens with Co concentrations 
= 0, 0.11, 0.8. In the undoped antiferromagnetic compound FeSn, we find possible signatures for a previously unidentified phase that sets in at 
~K, well beneath the Neel temperature 
~K as indicated by a peak in the relaxation rate 1/
observed in zero field (ZF) and longitudinal field (LF) SR measurements, with a corresponding anomaly in the ac and dc susceptibility, and an increase in the static width 1/
in ZF-SR measurements. No signatures of spatial symmetry breaking are found in STM down to 7~K. Related to the location and motion of muons in FeSn, we confirmed a previous report that about 40% of the implanted muons reside at a field-cancelling high symmetry site at 
~K, while an onset of thermal hopping changes the site occupancy at higher temperatures. In Fe
Co
Sn, where disorder eliminated the field-cancellation effect, all the implanted muons exhibit precession and/or relaxation in the ordered state. In Fe
Co
Sn, we find canonical spin glass behavior with freezing temperature 
~K; the ZF and LF-SR time spectra exhibit results similar to those observed in dilute alloy spin glasses CuMn and AuFe, with a critical behavior of 
at 
and 
as 
. The absence of spin dynamics at low temperatures makes a clear contrast to the spin dynamics observed by SR in many geometrically frustrated spin systems on insulating kagome, pyrochlore, and triangular lattices. The spin glass behavior of CoSn doped with dilute Fe moments is shown to originate primarily from the randomness of doped Fe moments rather than due to geometrical frustration of the underlying lattice.
Chiu, I.-H.; 大澤 崇人; 二宮 和彦*; 武田 伸一郎*; 高橋 忠幸*; 桂川 美穂*; 渡辺 伸*; 久保 謙哉*; 齋藤 努*; 水本 和美*; et al.
npj Heritage Science (Internet), 13, p.154_1 - 154_9, 2025/05
被引用回数：1 パーセンタイル：79.56(Humanities, Multidisciplinary)Cultural heritage artifacts often display complex, multi-layered structures. Therefore, an in situ noninvasive method is required for determining the elemental distribution of such materials. We present a nondestructive 3D elemental analysis approach for an Edo-period ceramic crucible using muonic X-ray measurements. The system employs four CdTe semiconductor imaging detectors to acquire 2D elemental distributions at 12 measurement angles, and 3D images were reconstructed based on computed tomography. We adjusted muon energy to penetrate the metallic layer covering the crucible bottom and analyze the interior of the crucible. Silicon(Si) and oxygen(O) signals were successfully identified, and these signals, originating from highly abundant silica (SiO) within the crucible matrix, confirmed the ceramic composition. These findings demonstrated the capability of muonic X-ray imaging in achieving depth-resolved analysis by controlling the observation position of an object. The presented method is broadly valuable for the cultural heritage study.
浪江 将成; 斉藤 淳一; 岡 涼太郎*; Kim, J.-H.*
Vacuum, 234, p.114038_1 - 114038_9, 2025/04
被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)Wettability of titanium (Ti) and surface-modified (Oxidized or Fluorinated) Ti with liquid sodium (Na) were investigated via experiments and theoretical calculations. From the experimental results, a sliding angle of Na droplet on oxidized Ti was smaller than that on untreated Ti, indicating the worsening of wettability by oxidation. In contrast, the sliding angle of Na droplet on fluoridated Ti was larger than that on untreated Ti, indicating an improvement in wettability by fluorination. Additionally, the cluster models for the interface between Na droplets and treated or untreated Ti were constructed for theoretical calculations of electronic states at the interface, covalent and ionic bonds at the interface were evaluated from the calculation results. The sliding angles obtained in the wettability tests and the strength of covalent bonding at the interface showed no correlation, but good correlation was observed between the sliding angles and ionic bonding at the interface. Thus, the wettability of surface-modified Ti with liquid Na can be theoretically understood based on the atomic interactions at the interface.
and Eu
onto coherent and melange-type pre-neogene sedimentary rocksHou, L.*; 戸田 賀奈子*; Mei, H.; 青柳 登; 斉藤 拓巳*
Journal of Nuclear Science and Technology, 61(11), p.1488 - 1498, 2024/11
被引用回数：4 パーセンタイル：64.33(Nuclear Science & Technology)Widely present in Japan's deep subterranean formations, pre-Neogene sedimentary rocks offer an option for high-level radioactive waste (HLW) deep geological disposal due to their favorable properties. However, their barrier properties necessitate further investigation. This research examines the characteristics of pre-Neogene sedimentary rocks, focusing on two rock types: the melange type with a distinct block-in-matrix structure and the sandstone-dominant coherent type. Their ability and mechanism to sorb Cs and Eu are assessed, and the differences between the two types are compared. The influence of inorganic carbon in groundwater and the role of clay minerals, such as illite, in the sorption of these metal ions, are highlighted. This investigation lays the groundwork for future studies on migration behaviors of radionuclides, essential for ensuring the long-term safety of HLW geological disposal.
杉浦 佑樹; 石寺 孝充; 青柳 登; Mei, H.; 斉藤 拓巳*; 舘 幸男
Applied Clay Science, 258, p.107476_1 - 107476_10, 2024/09
被引用回数：4 パーセンタイル：53.08(Chemistry, Physical)This study performed batch sorption experiments using Eu and Sm as chemical analogs of trivalent actinides to evaluate their sorption behavior onto illite in the presence of dissolved inorganic carbon (DIC). The results were analyzed using a thermodynamic sorption model (TSM), which predicted that Eu/Sm forms ternary-surface complexes with carbonate ions. Time-resolved laser fluorescence spectroscopy (TRLFS) measurements were performed to gather information on the chemical forms of sorbed Eu on illite. Parallel factor analysis (PARAFAC) of the TRLFS data indicated the presence of two Eu chemical species. The pH dependence of the chemical species was consistent with that of the surface species predicted by TSM. The dominant chemical species in the presence of carbonate was inferred to be coordinating carbonate ions based on the fluorescence lifetime, supporting the validity of the TSM.
Ding, H.*; 伊藤 啓太*; 遠藤 恭*; 高梨 弘毅; 関 剛斎*
Journal of Physics D; Applied Physics, 57(38), p.385002_1 - 385002_10, 2024/09
被引用回数：4 パーセンタイル：41.54(Physics, Applied)This paper reports the systematic study on the structure, magnetic properties and magnetoelastic properties for the Fe
Ga
(001) thin films epitaxially grown on the different substrates of GaAs(001) and MgO(001) using the sputtering technique. The alloy composition dependence of effective magnetoelastic coupling coefficient B
along the FeGa [110] direction indicated that the largest magnetoelastic coupling was obtained for the Fe-Ga layer with x = 30 grown on the MgO substrate. Considering the results of structural analysis and magnetization measurement, the different crystallite sizes depending on the kind of substrate may give rise to the different magnetoelastic coupling strengths between the Fe-Ga layers on the MgO and the GaAs. The magnetostriction along the FeGa [111] direction was also estimated with the assumption of plausible elastic property of Fe-Ga, and showed the values comparable to the reported value of bulk Fe-Ga. This means the large magnetostriction can be obtained even for the Fe-Ga thin films epitaxially grown not only on the GaAs(001) but also on the MgO(001). The findings in this work will give a guideline for designing spintronic applications with a Fe-Ga layer exhibiting a large magnetoelastic coupling.
浪江 将成; 斉藤 淳一; 池田 明日香; 岡 涼太郎*; Kim, J.-H.*
Surfaces (Internet), 7(3), p.550 - 559, 2024/09
The iron (Fe) specimens selected as the substrate metal for this study were surface-treated using fluorine gas, and their wettability with liquid sodium (Na) was evaluated using the sliding angle. Additionally, the surface morphology and binding state were analyzed, and the applicability of wettability control with liquid sodium by fluorination was discussed using the analysis results. Fluorination formed a fluoride layer comprising FeF and FeF
bonds on the iron surface. The composition of the fluoride layer varied, depending on the treatment conditions. The surface of the specimen that contains a lot of FeF bonds had a small sliding angle for the liquid sodium droplet and was harder to wet than the untreated specimen. In contrast, the surface of the specimen that contains a lot of FeF bonds had a large sliding angle for the liquid sodium droplet and was easier to wet than the untreated specimen. These results indicate that fluorination is an effective surface modification technique that can be applied to control the wettability of iron with liquid sodium.
齋藤 隼輝*; Yu, H.*; Gao, Z.*; 井上 耕治*; 近藤 創介*; 笠田 竜太*; 永井 康介*; 大場 洋次郎*; 廣井 孝介
Journal of Alloys and Compounds, 983, p.173852_1 - 173852_12, 2024/05
被引用回数：11 パーセンタイル：72.77(Chemistry, Physical)Cu alloys with high durability and high thermal and electric conductivities are the key to achieving a more energetically efficient and eco-friendly future. Noble Zr-added oxide-dispersion-strengthened Cu alloys (ODS - Cu) with high strengths are promising materials for meeting all future service requirements. In this study, three-dimensional atom probe (3D - AP) and transmission electron microscopy (TEM) revealed that the majority of nano - oxide particles in the Zr-added ODS - Cu were novel yttria-stabilized zirconia (YSZ) particles with a diameter of less than 4 nm, which were completely different from YZrO
and Y
ZrO
observed in other Zr - added ODS alloys. Multiscale observations including small - angle X - ray scattering (SAXS), 3D - AP, and TEM were performed to clarify the morphology of the oxide particles in the Zr - added ODS - Cu. Further strength enhancement through microstructural homogenization and specific incremental strength values were proposed.
大沢 直樹*; Kim, S.-Y.*; 久保田 真彦*; Wu, H.*; 渡部 創; 伊藤 辰也; 永石 隆二
Nuclear Engineering and Technology, 56(3), p.812 - 818, 2024/03
被引用回数：5 パーセンタイル：64.33(Nuclear Science & Technology)An impregnated silica-based adsorbent was prepared by combining HONTA extractant, Crea extractant, and macroporous silica polymer composite particles (SiO-P). The performance of platinum-group metals adsorption and separation on prepared (HONTA + Crea)/SiO-P adsorbent was assessed by batch-adsorption and chromatographic separation studies. (HONTA + Crea)/SiO-P adsorbent showed high adsorption performance of Pd(II) owing to an affinity between Pd(II) and Crea extractant based on the Hard and Soft Acids and Bases theory. The chromatographic experiment showed that Pd(II) was recovered entirely from the feed solution using 0.2 M thiourea in 0.1 M HNO. Possibility of recovery of Zr(IV), Mo(VI), and Re(VII) was also observed using the (HONTA + Crea)/SiO-P adsorbent.
水野 るり恵*; 新倉 潤*; 齋藤 岳志*; 松崎 禎市郎*; 櫻井 博儀*; Amato, A.*; 浅利 駿介*; Biswas, S.*; Chiu, I.-H.; Gianluca, J.*; et al.
Nuclear Instruments and Methods in Physics Research A, 1060, p.169029_1 - 169029_14, 2024/03
被引用回数：3 パーセンタイル：40.84(Instruments & Instrumentation)We have developed a photon detection system for muonic X-ray spectroscopy. The detector system consists of high-purity germanium detectors with BGO Compton suppressors. The signals from the detectors are readout with a digital acquisition system. The absolute energy accuracy, energy and timing resolutions, photo-peak efficiency, the performance of the Compton suppressor, and high count rate durability are studied with standard 
-ray sources and in-beam experiment using 
Al(
)
Si resonance reaction. The detection system was demonstrated at Paul Scherrer Institute. A calibration method for a photon detector at a muon facility using muonic X-rays of 
Au and 
Bi is proposed.
Mei, H.; 青柳 登; 斉藤 拓巳*; 田中 万也; 杉浦 佑樹; 舘 幸男
Applied Geochemistry, 162, p.105926_1 - 105926_8, 2024/02
被引用回数：8 パーセンタイル：70.20(Geochemistry & Geophysics)The sorption of U(VI) on illite at different pH and dissolved inorganic carbon (DIC) levels was investigated by using batch experiments, surface complexation modeling, and cryogenic time-resolved laser fluorescence spectroscopy (cryo-TRLFS) combined with parallel factor analysis (PARAFAC). The inhibiting effect of DIC on U(VI) sorption was revealed by the macroscopic batch experimental results. An updated 2-site protolysis non-electrostatic surface complexation and cation exchange model considering the formation of two uranyl-carbonate sorption complexes was able to reproduce the experimental results well. Based on the PARAFAC analysis on the cryo-TRLFS spectra, there was clear correspondence in the variation trend of the derived components with the sorption species from the modeling results, validating the formation of ternary uranyl-carbonate sorption species.
池田 一貴*; 佐次田 頌*; 大友 季哉*; 大下 英敏*; 本田 孝志*; 羽合 孝文*; 齋藤 開*; 伊藤 晋一*; 横尾 哲也*; 榊 浩司*; et al.
International Journal of Hydrogen Energy, 51(Part A), p.79 - 87, 2024/01
被引用回数：10 パーセンタイル：44.82(Chemistry, Physical)Low-vanadium-concentration alloys have low durability, and their hydrogen absorption and desorption amounts decrease by 20% after 100 cycles. In this study, we conducted reverse Monte Carlo modeling on X-ray diffraction patterns and neutron pair distribution functions of the hydrogen-absorbed and desorbed samples of a V
Ti
Cr
alloy to analyze the variations in the local structure. The local structure surrounding the hydrogen atom in the hydrogen-absorbed phase exhibited minimal changes. In contrast, hydrogen occupied both tetrahedral and octahedral sites of the hydrogen-desorbed phase almost equally during the early cycles; however, the amount of hydrogen occupying the tetrahedral sites increased with the number of cycles.
二宮 和彦*; 久保 謙哉*; 稲垣 誠*; 吉田 剛*; Chiu, I.-H.; 工藤 拓人*; 浅利 駿介*; 千徳 佐和子*; 竹下 聡史*; 下村 浩一郎*; et al.
Scientific Reports (Internet), 14, p.1797_1 - 1797_8, 2024/01
被引用回数：1 パーセンタイル：17.03(Multidisciplinary Sciences)鋼の特性を決める上で重要な鋼中のC量は、鋼の生産技術に大きく左右される。このため、ミュオンを使って鋼のC含有量を非破壊で測定する新しい方法を提案する。この方法は、生産中の鋼の品質管理だけでなく、貴重な鋼製考古学的遺物の分析にも使えるかもしれない。負の電荷を持つミュオンは原子系を形成し、最終的には核に吸収されるか電子に崩壊する。ミュオンの寿命は、Fe原子かC原子に捕らわれるかによってかなり違い、ミュオン停止位置での元素含有量をミュオン寿命測定で特定できる。C/Feのミュオン捕獲確率とCの元素含有量の関係は直線的で、ミュオン寿命測定で鋼のC含有量を定量的に決められる。さらに、ミュオンの入射エネルギーを調整して、0.5mm厚の3種類の鋼板からなる積層サンプルの各層でミュオンを停止させ、0.20-1.03wt%の範囲でC含有量を深さ選択的に、サンプルを壊さずに決定することに成功した。
Soler, J. M.*; Kek
linen, P.*; Pulkkanen, V.-M.*; Moreno, L.*; Iraola, A.*; Trinchero, P.*; Hokr, M.*; 
ha, J.*; Havlov
, V.*; Trpko
ov, D.*; et al.
Nuclear Technology, 209(11), p.1765 - 1784, 2023/11
被引用回数：6 パーセンタイル：66.64(Nuclear Science & Technology)The REPRO-TDE test was performed at a depth of about 400 m in the ONKALO underground research facility in Finland. Synthetic groundwater containing radionuclide tracers (HTO, Cl-36, Na-22, Ba-133, Cs-134) was circulated for about four years in a packed-off interval of the injection borehole. Tracer activities were additionally monitored in two observation boreholes. The test was the subject of a modelling exercise by the SKB GWFTS Task Force. Eleven teams participated in the exercise, using different model concepts and approaches. Predictive model calculations were based on laboratory-based information concerning porosities, diffusion coefficients and sorption partition coefficients. After the experimental results were made available, the teams were able to revise their models to reproduce the observations. General conclusions from these back-analysis calculations include the need for reduced effective diffusion coefficients for Cl-36 compared to those applicable to HTO (anion exclusion), the need to implement weaker sorption for Na-22, compared to results from laboratory batch-sorption experiments, and the observation of large differences between the theoretical initial concentrations for the strongly-sorbing Ba-133 and Cs-134 and the first measured values a few hours after tracer injection. Different teams applied different concepts, concerning mainly the implementation of isotropic vs. anisotropic diffusion, or the possible existence of Borehole Disturbed Zones around the different boreholes. The role of microstructure was also addressed in two of the models.
