Composition dependence of the anomalous Nernst effect in FeMnN and FeCoN films

Yin, W.*; 伊藤 啓太*; 坪和 優佑*; 辻川 雅人*; 白井 正文*; 梅津 理恵*; 高梨 弘毅

Journal of Magnetism and Magnetic Materials, 628, p.173157_1 - 173157_8, 2025/09

https://doi.org/10.1016/j.jmmm.2025.173157

FeN exhibits a large anomalous Nernst effect (ANE), which motivates a systematic study of enhancing the anomalous Nernst coefficient (SANE) by modulating its electronic and magnetic structures. In this study, Mn and Co substitution effects for Fe in FeN on S were investigated. FeMnN and FeCoN films in wide ranges of x and y were grown epitaxially on MgO(001) and (LaAlO)(SrTaAlO)(001) substrates, respectively, using molecular beam epitaxy. The S value of the FeN film is suppressed by substituting Fe with Mn or Co. By measuring the ANE, Seebeck effect, and anomalous Hall effect, the transverse thermoelectric conductivity (alpha) was evaluated. The composition dependence of S was dominated by the change of alpha for both FeMnN and FeCoN films. First-principles calculations were conducted for the transverse electric conductivity (sigma) and alpha of FeN and FeCoN, and large alpha leading to large S was predicted in FeCoN.

Temperature-dependent deformation behavior of dual-phase medium-entropy alloy; In-situ neutron diffraction study

Gu, G. H.*; Jeong, S. G.*; Heo, Y.-U.*; Harjo, S.; Gong, W.; Cho, J.*; Kim, H. S.*; 他4名*

Journal of Materials Science & Technology, 223, p.308 - 324, 2025/07

https://doi.org/10.1016/j.jmst.2024.11.057

Face-centered cubic (FCC) equi-atomic multi-principal element alloys (MPEAs) exhibit excellent mechanical properties from cryogenic to room temperatures. At room temperature, deformation is dominated by dislocation slip, while at cryogenic temperatures (CTs), reduced stacking fault energy enhances strain hardening with twinning. This study uses in-situ neutron diffraction to analyze the temperature-dependent deformation behavior of Al(CoNiV), a dual-phase (FCC/BCC) medium-entropy alloy (MEA). At liquid nitrogen temperature (LNT), deformation twinning in the FCC matrix leads to additional strain hardening through the dynamic Hall-Petch effect, giving the appearance of improved strengthening at LNT. In contrast, BCC precipitates show dislocation slip at both 77 K and 298 K, with temperature-dependent lattice friction stress playing a significant role in strengthening. The study enhances understanding of deformation behaviors and provides insights for future alloy design.

Hybrid data assimilation methods for nuclear-data-induced uncertainties

丸山 修平; 山本 章夫*; 遠藤 知弘*

Journal of Nuclear Science and Technology, 14 Pages, 2025/05

https://doi.org/10.1080/00223131.2025.2500579

This study proposes new hybrid data assimilation (DA) methods to effectively use experimental data represented in two different ways in the DA process for reducing nuclear-data-induced uncertainties. Conventional DA methods often assume a linear model, where data in a DA database are represented by their differential coefficients, i.e., nuclear data sensitivity coefficients. In contrast, more rigorous and versatile DA methods based on sampling techniques have been proposed recently. These sampling-based DA methods describe data for DA using results derived from direct transport calculations performed with perturbed nuclear data samples. The proposed hybrid DA methods simultaneously use both types of data described by sensitivity coefficients and sampling results and thus are called "hybrid." Two hybrid DA methods are proposed herein: the simple hybrid DA and efficient hybrid DA methods. Among these, the simple method is based on a straightforward concept that uses a random sampling technique. In contrast, the efficient method employs a more technical method that effectively combines a new deterministic sampling technique with sensitivity coefficients to reduce statistical uncertainties associated with the simple method. The efficient method is expected to be a candidate to achieve high precision and rigorous DA with a realistic sample size.

Role of solute hydrogen on mechanical property enhancement in Fe-24Cr-19Ni austenitic steel; An neutron diffraction study

伊東 達矢; 小川 祐平*; Gong, W.; Mao, W.*; 川崎 卓郎; 岡田 和歩*; 柴田 曉伸*; Harjo, S.

Acta Materialia, 287, p.120767_1 - 120767_16, 2025/04

https://doi.org/10.1016/j.actamat.2025.120767

Incorporating solute hydrogen into Fe-Cr-Ni-based austenitic stainless steels enhances both strength and ductility, providing a promising solution to hydrogen embrittlement by causing solid-solution strengthening and assisting deformation twinning. However, its impacts on the relevant lattice defects evolution (, dislocations, stacking faults, and twins) during deformation remains unclear. This study compared the tensile deformation behavior in an Fe-24Cr-19Ni (mass%) austenitic steel with 7600 atom ppm hydrogen-charged (H-charged) and without hydrogen-charged (non-charged) using neutron diffraction. Hydrogen effects on the lattice expansion, solid-solution strengthening, stacking fault probability, stacking fault energy, dislocation density, and strain/stress for twin evolution were quantitatively evaluated to link them with the macroscale mechanical properties. The H-charged sample showed improvements in yield stress, flow stress, and uniform elongation, consistent with earlier findings. However, solute hydrogen exhibited minimal influences on the evolution of dislocation and stacking fault. This fact contradicts the previous reports on hydrogen-enhanced dislocation and stacking fault evolutions, the latter of which can be responsible for the enhancement of twinning. The strain for twin evolution was smaller in the H-charged sample compared to the non-charged one. Nevertheless, when evaluated as the onset stress for twin evolution, there was minimal change between the two samples. These findings suggest that the increase in flow stress due to the solid-solution strengthening by hydrogen is a root cause of accelerated deformation twinning at a smaller strain, leading to an enhanced work-hardening rate and improved uniform elongation.

クリープ破断時間および高温引張強度予測モデルの連合学習

櫻井 惇也*; 鳥形 啓輔*; 松永 学*; 高梨 直人*; 日比野 真也*; 木津 健一*; 森田 聡*; 井元 雅弘*; 下畠 伸朗*; 豊田 晃大; et al.

鉄と鋼, 111(5), p.246 - 262, 2025/04

https://doi.org/10.2355/tetsutohagane.TETSU-2024-124

Creep testing is time-consuming and costly, leading institutions to limit the number of tests conducted to the minimum necessary for their specific objectives. By pooling data from each institution, it is anticipated that predictive models can be developed for a wide range of materials, including welded joints and degraded materials exposed to service conditions. However, the data obtained by each institution is often highly confidential, making it challenging to share with others. Federated learning, a type of privacy-preserving computation technology, allows for learning while keeping data confidential. Utilizing this approach, it is possible to develop creep life prediction models by leveraging data from various institutions. In this paper, we constructed global deep neural network models for predicting creep rupture life of heat-resistant ferritic steels in collaboration with eight institutions using the federated learning system we developed for this purpose. Each institution built a local model using only its own data for comparison. While these local models demonstrated good predictive accuracy for their respective datasets, their predictive performance declined when applied to data from other institutions. In contrast, the global model constructed using federated learning showed reasonably good predictive performance across all institutions. The distance between each institution's data was defined in the space of explanatory variables, with the NIMS data, which had the largest dataset, serving as the reference point. The global model maintained high predictive accuracy regardless of the distance from the NIMS data, whereas the predictive accuracy of the NIMS local model significantly decreased as the distance increased.

令和5年度東京電力福島第一原子力発電所周辺における航空機モニタリング及び無人飛行機による放射線モニタリングに係る技術開発(受託研究)

普天間 章; 眞田 幸尚; 中間 茂雄; 佐々木 美雪; 越智 康太郎; 長久保 梓; 澤幡 義郎*; 川崎 義晴*; 岩井 毅行*; 平賀 祥吾*; et al.

JAEA-Technology 2024-021, 232 Pages, 2025/03

JAEA-Technology-2024-021.pdf:25.79MB

2011年3月11日に発生した東北地方太平洋沖地震による津波に起因する東京電力福島第一原子力発電所事故では、大量の放射性物質が周辺環境に飛散した。事故直後から、放射線の分布を迅速かつ広範囲に測定する手段として、航空機を用いた空からの測定方法が採用されている。日本原子力研究開発機構は、原子力規制庁からの受託事業として、有人ヘリコプター及び無人ヘリコプターを使用して、東京電力福島第一原子力発電所周辺の航空機モニタリングを継続的に実施してきた。本報告書では、令和5年度に実施したモニタリング結果について取りまとめ、過去のモニタリング結果との比較から空間線量率等の変化量を評価し、その変化要因について考察した。また、航空機モニタリングによる計数率から空間線量率への換算精度向上のために、地形の起伏を考慮に入れた解析を行った。地形の起伏を考慮する前後の解析結果を比較し、本手法による換算精度向上の効果を評価した。さらに、有人ヘリコプターについては、空気中のラドン子孫核種の弁別手法を測定結果に適用し、ラドン子孫核種が航空機モニタリングに与える影響を評価した。加えて、より効率的に広範囲な航空機モニタリングを展開するため、無人航空機によるモニタリングの技術開発を進めた。

令和5年度研究開発・評価報告書 評価課題「原子力施設の廃止措置及び関連する放射性廃棄物の処理に関する技術開発」(事前評価)

BE資源・処分システム開発部

JAEA-Evaluation 2024-002, 86 Pages, 2025/03

JAEA-Evaluation-2024-002.pdf:8.29MB

国立研究開発法人日本原子力研究開発機構は、「国の研究開発評価に関する大綱的指針(平成28年12月21日内閣総理大臣決定)」に基づき、令和6年3月21日に「原子力施設の廃止措置及び関連する放射性廃棄物の処理に関する技術開発」に関する第4期中長期目標期間の研究開発計画のうち、令和3年度以降に開始した研究テーマに対する事前評価を廃止措置研究開発・評価委員会に諮問した。これを受けて、廃止措置研究開発・評価委員会は定められた評価の観点に従い評価を行った。

Modeling of coupled processes in full-scale engineered barrier system performance experiment at Horonobe Underground Research Laboratory, Japan

大野 宏和; 高山 裕介*

Geomechanics for Energy and the Environment, 41, p.100636_1 - 100636_14, 2025/03

https://doi.org/10.1016/j.gete.2025.100636

In the geological disposal of high-level radioactive waste, the overpack lifetime and initial conditions of radionuclide migration are essential considerations along with the assessments of the environmental conditions, including study of the evolution of near-field thermal, hydrological, mechanical, and chemical processes following the emplacement of an engineered barrier system. In this study, experimental data from an in situ full-scale engineered barrier experiment at Horonobe Underground Research Laboratory were used to assess the applicability of a simulation model to evaluate near-field coupled processes.

Measurements of neutron capture cross-section for nuclides of interest in decommissioning (II); Fe(n,)Fe

中村 詔司; 芝原 雄司*; 遠藤 駿典; Rovira Leveroni, G.; 木村 敦

Journal of Nuclear Science and Technology, 62(3), p.300 - 307, 2025/03

https://doi.org/10.1080/00223131.2024.2427244

As nuclear facilities are dismantled in decommissioning, large amount of various waste is generated. Even more inconveniently, waste is radioactive due to neutron activation. Thus, the neutron capture cross-sections of nuclides targeted in decommissioning are required to evaluate the radioactivity produced. In this work, Fe nuclide was selected among objective nuclides for decommissioning, and its thermal-neutron capture cross-section was measured by a neutron activation method at the graphite thermal column of Kyoto University Research Reactor in 5-MW operation. The thermal-neutron capture cross-section was derived using s convention. The present work obtained 1.360.03 barns for the Fe(n,)Fe reaction. The present result supports the JENDL-5 evaluation within 2. If updated with currently recommended nuclear data, some of the reported past data would support the present result.

隠匿された核物質の現場検知システムの開発; 核セキュリティ強化に向けた取組

田辺 鴻典*; 米田 政夫; 藤 暢輔; 北村 康則*; 三澤 毅*

日本原子力学会誌ATOMO, 67(3), p.198 - 202, 2025/03

https://doi.org/10.3327/jaesjb.67.3_198

鉛等で隠匿されたUに対する非破壊測定技術の開発は、長年、核セキュリティ上の最重要課題と言われてきたが、依然として現場レベルでの検知は困難な状況にある。我々はCf回転照射法と呼ばれる新たな核物質非破壊測定手法を提案し、回転照射装置と水チェレンコフ中性子検出器で構成される運搬性の高い現場検知システムを開発、本システムによる核物質検知を実証した。本報では、開発したシステムを概説するとともに今後の展望について解説する。