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Dong, F.*; Xiao, Y.*; Chen, S.*; 出町 和之*; 高屋 茂; 吉川 雅紀
Advanced Engineering Informatics, 69(Part D), p.104094_1 - 104094_23, 2026/01
被引用回数：0 パーセンタイル：0.00(Computer Science, Artificial Intelligence)Ensuring safe and stable industrial plant operations requires accurate and timely fault diagnosis from multivariate time-series (MTS) sensor data. Conventional methods struggle with the complexity, high dimensionality, and limited feature extraction. To address this, we propose a novel end-to-end fault diagnosis framework that enhances class separability by leveraging instance-wise global and timestamp-wise local views of MTS representations. The dataset is augmented from the dual-view, and a complementary contrastive loss function captures both global and local contextual information. Unlike previous representation learning approaches, the diagnosis model's backbone and classifier are jointly optimized in an end-to-end scheme, ensuring aligned representations with the classification objective. Experimental results on simulated nuclear power plant fault datasets demonstrate the framework's effectiveness and robustness.
Ji, Y.-Y.*; Joung, S.*; Ji, W.*; 越智 康太郎; 佐々木 美雪; 眞田 幸尚
Journal of Radiological Protection, 45(4), p.042501_1 - 042501_11, 2025/12
被引用回数：1 パーセンタイル：96.41(Environmental Sciences)本研究では、LaBr
(Ce)検出器を用いた韓国原子力研究院の無人航空機搭載型ガンマ線スペクトロメトリーシステムの開発と実地検証について報告する。FDNPP付近における日本原子力研究開発機構との共同調査では、高度に基づく減衰補正を適用後、信頼性の高い線量率推定が得られたが、傾斜地では差異が生じた。緊急対応用途における精度向上のため、地形データの組み込みが推奨される。
Catumba, G.*; 平口 敦基; Hou, G. W.-S.*; Jansen, K.*; Kao, Y.-J.*; David Lin, C.-J.*; Ramos, A.*; Sarkar, M.*
Proceedings of Science (Internet), 466, p.145_1 - 145_10, 2025/12
SU(2)ゲージ場を持つカストディアル2ヒッグス二重項模型を格子上で研究する。この模型は標準模型と同じ大域的対称性を持つが、ヒッグス場が追加されることでスカラースペクトルが拡大し、大域的対称性の自発的破れが発生する可能性が出てくる。カストディアル2ヒッグス二重項模型のスペクトルと走るゲージ結合定数を、カットオフが300から600GeVで標準模型での物理量が一定となる線上で研究した。結果として追加したBSMスカラー場の実現可能な質量の下限は、Wボソンの質量よりはるかに小さいことがわかった。そして、この研究で選択した4点相互作用の結合定数では、BSM状態の1つに対する推定された下限質量は約
0.2
で、カットオフに依存しないことがわかった。
高橋 嘉夫*; 三浦 輝*; 山田 真也*; 関澤 央輝*; 新田 清文*; 橋本 直*; 蓬田 匠; 山口 瑛子; 岡田 信二*; 板井 啓明*; et al.
Journal of Hazardous Materials, 495, p.139031_1 - 139031_19, 2025/09
被引用回数：1 パーセンタイル：40.80(Engineering, Environmental)本発表では、2011年の福島第一原子力発電所事故で放出された放射性セシウム含有微粒子(CsMP)中のセシウムの化学状態を、高分解能X線吸収分光法(XANES)とマイクロX線蛍光(
-XRF)を用いて解析した。その結果、主にガラス中に溶解したセシウムと、内部空隙表面に濃縮したセシウムの2種が確認された。後者はもともと気体として存在し、溶けたガラスが冷えて固まる際に濃縮したと考えられる。これらの知見は、事故時のCsMP形成過程や今後の廃炉作業、安全評価に重要である。
山口 義仁; Li, S.; 勝山 仁哉
Proceedings of the ASME 2025 Pressure Vessels & Piping Conference (PVP2025) (Internet), 8 Pages, 2025/07
Recently, in Japan and France, the intergranular stress corrosion cracking (SCC) has been detected in welded joints of stainless steel pipes in primary piping systems in Pressurized Water Reactors (PWRs). It was observed that hardness in the welded joints with SCC was higher than that of the base metal. It is shown that hardness is an important parameter in the SCC propagation in the PWR primary system water environment. In our previous studies, a numerical method was proposed for the prediction of hardness and weld residual stress in Type 316 stainless steel welded joints. The proposed numerical method was validated through the comparisons between predicted results and measurements for welded stainless steel specimens. And then, the effect of welding condition on hardness and residual stresses in stainless steel pipe welds was investigated by using above method. In this study, probabilistic fracture mechanics analysis code PASCAL-SP Ver.2 developed by Japan Atomic Energy Agency is improved to be able to evaluate the failure probability of stainless steel pipe with SCC in PWRs by considering the effect of hardness, and the verification is carried out for an improved function. Additionally, failure probabilities are calculated considering crack growth due to SCC and fatigue in PWR primary water environment. The effect of welding condition such as heat input at welding is quantitatively evaluated based on the failure probabilities.
Niu, X.*; Elakneswaran, Y.*; Li, A.*; Seralathan, S.*; 菊池 亮佑*; 平木 義久; 佐藤 淳也; 大杉 武史; Walkley, B.*
Cement and Concrete Research, 190, p.107814_1 - 107814_17, 2025/04
被引用回数：8 パーセンタイル：92.27(Construction & Building Technology)Metakaolin-based geopolymers have attracted significant interest in decontaminating radioactive debris from the Fukushima nuclear accident. This study explored the incorporation of boron (B) into geopolymers using boric acid as the source, with the goal of developing B-enriched geopolymers for enhanced radionuclide immobilisation and neutron capture potential.
Joung, S.*; Ji, Y.-Y.*; Choi, Y.*; Lee, E.*; Ji, W.*; 佐々木 美雪; 越智 康太郎; 眞田 幸尚
Journal of Instrumentation (Internet), 20(4), p.P04027_1 - P04027_10, 2025/04
被引用回数：1 パーセンタイル：47.48(Instruments & Instrumentation)An airborne survey system named the MARK-A1 was previously developed to be mounted on an unmanned aerial vehicle for the purpose of application in contaminated areas with high dose rate levels. The MARK-A1 system consists of a CZT detector, signal processing unit, and positioning and interface units linked to a PC on the ground. The weight of the system is below 1 kg for loading on a commercial drone. In the current work, for experimental verification, field testing was conducted in a high dose rate environment near the Fukushima Daiichi Nuclear Power Plant. With the cooperation of the Japan Atomic Energy Agency, the MARK-A1 was installed on an unmanned aerial vehicle to conduct airborne surveys using two flight methods, namely a flat flight and a step flight, at various speeds. The airborne survey data were converted to gamma dose rates at a height of 1 m above the ground using a flat source model to create contamination maps. For a comparative evaluation of the airborne survey results, an in situ survey was also conducted in the survey area, and it was confirmed that the step flight method better matched the surface survey results.
(Mg
Si)-phase in Al-Mg-Si-Ag alloyAhmed, A.*; Uttarasak, K.*; 土屋 大樹*; Lee, S.*; 西村 克彦*; 布村 紀男*; 池野 進*; Malik, A.*; 清水 一行*; 平山 恭介*; et al.
Materials Today Communications (Internet), 43, p.111835_1 - 111835_10, 2025/02
被引用回数：2 パーセンタイル：57.62(Materials Science, Multidisciplinary)This study investigates the interface characteristics of the hexagonal (MgSi)-phase in Al-Mg-Si-Ag alloys, providing novel insights into its orientation relationship, interfacial conditions, misfit, and Ag segregation with the Al matrix. Using optical microscopy (OM), focused ion beam (FIB), and scanning transmission electron microscopy (STEM), we clarified the role of three distinct facets {111}
//{111}
, {122}//{110}, and {112}//{111} in determining the stability and properties of the hexagonal (MgSi)-phase. Unlike the conventional (MgSi)-phase with a {100} habit plane, the hexagonal -phase was found on the {111} habit plane, exhibiting a new orientation relationship [{111}//{111}, 
110
//110]. Ag segregation was notably observed at the interfaces of these facets, with varying concentrations influencing interfacial coherency and strain. These findings not only advance our understanding of microstructural evolution in Al-Mg-Si alloys but also provide a foundation for tailoring material properties through interface engineering. The results offer critical insights for optimizing alloy compositions and heat treatments to enhance mechanical properties and performance in practical applications.
Metcalfe, R.*; Benbow, S. J.*; 川間 大介*; 舘 幸男
Science of the Total Environment, 958, p.177690_1 - 177690_17, 2025/01
花崗岩が隆起している条件を対象とした地層処分の安全評価においては、隆起による地質条件の変化とそれに伴う放射性核種の移行・遅延特性への影響を考慮する必要がある。このような地質環境の長期変遷を考慮した安全評価では、十分に現実的な数値モデルと適切なパラメータを適用する必要がある。しかしながら、隆起過程には、岩石特性や核種移行特性の変化などを含む複雑な連成現象が含まれるため、モデルの開発には困難を伴う。ここでは、いくつかの代表的な放射性核種を対象とした連成モデル解析を通じて、現実的で保守的なプロセスの概念化とモデルパラメータの設定を検討するための方法論を提示する。
前川 暁洋*; 佐久間 一幸; Fan, S.*; 福田 美保*; 那須 康輝*; 谷口 圭輔*
KEK Proceedings 2024-6, p.7 - 12, 2024/12
最新の気候変動予測シナリオである2023年版(IPCC第6次評価報告書準拠)を用いて気候変動に応じた将来の放射性セシウム流出量の評価を行った。計算モデルMERCURYを用いて阿武隈川の二本松地点における2031-2049年及び2081-2099年のセシウム-137流出量を推定した。気候変動シナリオ(SSP1-2.6、SSP2-4.5、SSP5-8.5)において2031-2049年(約2.6-3.1TBq)より2081-2099年(約0.83-0.95TBq)の流出量が小さく、気候変動シナリオの違いによる流出量の差は大きくなかった。
Catumba, G.*; 平口 敦基; Hou, W.-S.*; Jansen, K.*; Kao, Y.-J.*; David Lin, C.-J.*; Ramos, A.*; Sarkar, M.*
Physical Review Research (Internet), 6(4), p.043172_1 - 043172_12, 2024/11
様々な表現の物質場と結合するゲージ理論は、物理学の様々な分野で重要な役割を果たしている。最近、銅酸化物超伝導体の最適ドーピング近傍の興味深い擬ギャップ相のいくつかの側面が、発現したSU(2)ゲージ対称性によって説明できるかもしれないことが提案された。ホールドーピングによる転移付近では、4つの随伴スカラー場と結合した(2+1)次元SU(2)ゲージ理論を構築することができ、異なる破れた対称性を持つ様々な相が存在する豊かな相図を与える。我々は、ハイブリッドモンテカルロ法を用いて、ユークリッド格子上でこのモデルの相図を研究した。その結果、これまでの平均場の研究で予言されていたように、対称性が破れた複数の相が存在することがわかった。4点相互作用によって、摂動論の範囲ではこの理論のSU(2)ゲージ対称性はU(1)か
に分解される。さらに、我々はこの理論における閉じ込め-非閉じ込め転移を評価し、我々が研究した格子体積の範囲では、どちらの破れた相も非閉じ込め相であることを見いだした。しかしながら、ポリヤコフループの振る舞いには2つの相で顕著な違いがあることがわかった。
Dong, F.*; Chen, S.*; 出町 和之*; 吉川 雅紀; 関 暁之; 高屋 茂
Proceedings of 31st International Conference on Nuclear Engineering (ICONE31) (Internet), p.225 - 231, 2024/11
Timely and accurate anomaly detection is of utmost importance in ensuring nuclear safety to guarantee the normal operation of nuclear facilities and to prevent severe accidents. Due to the complexity of the dataset from the condition-based monitoring, advanced data-driven deep learning algorithms with their state-of-the art performance, are deployed for automatic anomaly detection in nuclear power plants (NPPs). Nevertheless, in the collected dataset, the knowledge about whether some certain periods are in an abnormal or normal state is available, while for a greater portion of the time, only data in unknown operating states can be acquired, rendering the general supervised learning (SL) and unsupervised learning (UL) suboptimal learning methods. Therefore, a combined learning approach is deployed in the proposed time series analysis framework, allowing the utilization of additional domain knowledge within the dataset to train the framework from UL to SL. Additionally, due to the intricate inherent relationships among different instruments and the low frequency of anomaly occurrences, the implicit influential weights of each dimension vary when identifying different kind of anomalies. To tackle this challenge, an attention mechanism is integrated into the anomaly detection model for highlighting the prominent abnormal features and hence enable it to address the subtle impact of each dimension to enhance the ability of anomaly detection task. Experimental evaluations on the real-world multivariate benchmark dataset Security Water Treatment (SWaT) and on the high temperature gas-cooled reactor (HTGR) anomaly cases dataset based on the analytical code 'ACCORD', demonstrate the feasibility and effectiveness of the proposed approach.
gauge fieldsCatumba, G.*; 平口 敦基; W.-S. Hou, G.*; Jansen, K.*; Kao, Y.-J.*; David Lin, C.-J.*; Ramos, A.*; Sarkar, M.*
Proceedings of Science (Internet), 453, p.87_1 - 87_9, 2024/11
本研究では、ゲージ場と相互作用する一般的な2ヒッグスダブレット模型を格子ゲージ理論で議論する。秩序変数の代わりとしてゲージ不変の大域的観測量を計算することにより、この模型の相図を調べた。それぞれの相において、裸の結合定数の組み合わせや対称性の破れのパターンを変えて理論のスカラー粒子およびベクトルボソン粒子の質量の評価を行なった。またスケール設定と走るゲージ結合定数の決定は、ウィルソンフロウの計算によって行なった。
Catumba, G.*; 平口 敦基; W.-S. Hou, G.*; Jansen, K.*; Kao, Y.-J.*; David Lin, C.-J.*; Ramos, A.*; Sarkar, M.*
Proceedings of Science (Internet), 453, p.362_1 - 362_7, 2024/11
本研究では、最近Sachdevらによって最適ドーピング付近の銅酸化物超伝導体の物理を説明するために提案された、随伴表現の4つのヒッグス場を持つ3次元SU(2)ゲージ理論を議論する。この理論の閉じ込め相は通常のフェルミ液体相に対応し、ヒッグス相は銅酸化物の擬ギャップ相に対応しており、我々はハイブリッドモンテカルロ法を用いて理論の相図を調査した。我々は、先行研究の平均場での計算に定性的に従う様々な相の存在を発見し、銅酸化物におけるそれらの役割について議論する。さらに、閉じ込め非閉じ込め相転移を調べるためにポリヤコフループの振る舞いを調べ、ヒッグス相が安定な非閉じ込め相を持つことを見いだした。
RhSi社本 真一; 山内 宏樹; 飯田 一樹*; 池内 和彦*; 金子 耕士; Chen, Y.-S.*; 矢野 真一郎*; Hsu, P.-T.*; Lee, M. K.*; Hall, A. E.*; et al.
Physical Review Research (Internet), 6(3), p.033303_1 - 033303_7, 2024/09
MnRhSiの磁気励起は少なくとも0.3から140meVに広がる。200Kでの非弾性散乱強度を積分することで、Mnサイト当たり約5
の磁気モーメントは、約5であることがわかった。一方で、長距離磁気秩序の磁気モーメントは4Kでわずか2.61であり、多くの部分が低温まで揺らいでいることがわかった。
Sn wires with and without Cu-Nb reinforcement中本 美緒*; 菅野 未知央*; 荻津 透*; 杉本 昌弘*; 谷口 諒*; 廣瀬 清慈*; 川崎 卓郎; Gong, W.; Harjo, S.; 淡路 智*; et al.
IEEE Transactions on Applied Superconductivity, 34(5), p.8400806_1 - 8400806_6, 2024/08
被引用回数：0 パーセンタイル：0.00(Engineering, Electrical & Electronic)For an accelerator magnet, a certain mechanical strength is required to sustain against a transverse compression stress due to Lorentz force. A bronze-route NbSn wire with Cu-Nb reinforcement was developed by Tohoku University and Furukawa Electric to enhance the strength against axial tension. The Cu-Nb reinforcement wire also exhibited some indication of strength improvement against transverse compression; however, the details of a reinforcement mechanism for the transverse compression stress have not been clarified. In this study, the internal strains of NbSn bronze-route wires with and without the Cu-Nb reinforcement under transverse compression stress were evaluated by neutron diffraction at BL19 (TAKUMI) in J-PARC. The samples were attached to jig with solder only at the ends and compression was applied at the center of the samples with 30-mm anvil with 5-mm wide and 8- to 15-mm high beam. Since a critical current, Ic of a superconducting wire depends on the three-dimensional strain, internal strain of NbSn along the axial and two orthogonal radial directions were evaluated at room temperature (RT). In the different setup, Ic measurements of the wires under transverse compression stresses were also performed at 4.2 K and 14.5 T. Using 3-mm wide anvil, the transverse compression was applied at 4.2 K or RT. The neutron diffraction results indicated no significant differences in the internal strains of NbSn under transverse compression between the samples with and without Cu-Nb reinforcement, while the Ic measurements showed potential increase in the irreversible stress (
) for Cu-Nb reinforced wires. The reason for this discrepancy was discussed based on the difference in the experimental setups for each measurement.
Zeng, Z.*; Zhou, C.*; Zhou, H.*; Han, L.*; Chi, R.*; Li, K.*; 古府 麻衣子; 中島 健次; Wei, Y.*; Zhang, W.*; et al.
Nature Physics, 20(7), p.1097 - 1102, 2024/07
被引用回数：24 パーセンタイル：95.52(Physics, Multidisciplinary)Emergent quasiparticles with a Dirac dispersion in condensed matter systems can be described by the Dirac equation for relativistic electrons, in analogy with Dirac particles in high-energy physics. For example, electrons with a Dirac dispersion have been intensively studied in electronic systems such as graphene and topological insulators. However, charge is not a prerequisite for Dirac fermions, and the emergence of Dirac fermions without a charge degree of freedom has been theoretically predicted to be realized in Dirac quantum spin liquids. These quasiparticles carry a spin of 1/2 but are charge-neutral and so are called spinons. Here we show that the spin excitations of a kagome antiferromagnet, YCu
(OD)
Br[Br
(OD)
], are conical with a spin continuum inside, which is consistent with the convolution of two Dirac spinons. The predictions of a Dirac spin liquid model with a spinon velocity obtained from spectral measurements are in agreement with the low-temperature specific heat of the sample. Our results, thus, provide spectral evidence for a Dirac quantum spin liquid state emerging in this kagome lattice antiferromagnet. However, the locations of the conical spin excitations differ from those calculated by the nearest-neighbor Heisenberg model, suggesting the Dirac spinons have an unexpected origin.
Li, S.; 山口 義仁; 勝山 仁哉; Li, Y.
Proceedings of the ASME 2024 Pressure Vessels & Piping Conference (PVP 2024) (Internet), 8 Pages, 2024/07
Flaws due to stress corrosion cracking (SCC) were recently detected in welded joints of austenitic stainless steel piping lines in pressurized water reactors. Welding-induced high hardness and tensile residual stress are known as one of the main factors affecting SCC. In this work, thermal-elastic-plastic coupled three-dimensional finite element analyses were performed to investigate the distributions of welding residual stress and hardness in butt-welded joints of Type 316 stainless steel. Different heat inputs were applied to the pipe welds, including normal heat input, high heat input and very high heat input. Two different constraint conditions were considered for the welded joints, i.e., both ends free or clamped, the latter indicating that the welded joint is constrained by the surrounding piping system. Simulation results were compared with experimental data such as welding thermal cycle, axial shrinkage and residual stress for validation. The effects of heat input and constraint condition on the welding residual stress and hardness at different sections of the welded joints including the weld start/end location were discussed in detail.
-phase in Al-Mg-Si alloys during aging treatmentAhmed, A.*; Uttarasak, K.*; 土屋 大樹*; Lee, S.*; 西村 克彦*; 布村 紀男*; 清水 一行*; 平山 恭介*; 戸田 裕之*; 山口 正剛; et al.
Journal of Alloys and Compounds, 988, p.174234_1 - 174234_9, 2024/06
被引用回数：15 パーセンタイル：88.75(Chemistry, Physical)本研究は、Al-Mg-Si合金における相の成長過程を形態進化の観点から明らかにすることを目的とする。本研究では、高分解能透過電子顕微鏡(HR-TEM)、集束イオンビーム(FIB)及び光学顕微鏡(OM)を用いて、相の配向関係、形状、成長過程、ミスフィット値、及び相とAlマトリックスとの界面状態を調べた。その結果、相の端にファセットが確認され、相の新しい3次元形状が2つ提案された。我々は、MgSi結晶の成長過程における形態変化を説明するためにミスフィットを計算し、不安定な{111}ファセットが(001)ファセットや(011)ファセットと比較して高いミスフィット値を持つことを解明した。これは、Al-Mg-Si合金の微細構造変化を予測し、所望の特性を持つ材料を設計するために重要な知見である。
久保田 真彦*; Kim, S.-Y.*; Wu, H.*; 渡部 創; 佐野 雄一; 竹内 正行; 新井 剛*
Journal of Radioanalytical and Nuclear Chemistry, 333(5), p.2413 - 2420, 2024/05
被引用回数：2 パーセンタイル：44.79(Chemistry, Analytical)To minimize the use of organic solvents and achieve a selective adsorption separation of minor actinides (MA(III)) and Ln(III), adsorbents consisting of SiO
-P particles impregnated with hexaoctylnitrilotriacetamide (HONTA) were prepared. Batch experiments were performed to evaluate the adsorption properties of the HONTA/SiO-P adsorbent for MA(III) and simulated fission products in HNOsolution. The uniform distribution of Eu(III) on the adsorbent was confirmed via particle induced X-ray emission analysis, and X-ray photoelectron spectroscopy revealed that EuNO was the adsorbed species. This study provides a simplified process for the separation of MA(III) using a HONTA/SiO-P packed column.
