材料の熱膨張差を利用した受動式クリープ疲労試験技術の確立に関する研究

若井 隆純; 安藤 勝訓; 岡島 智史; 豊田 晃大; 小沼 輝充*; 高橋 亮耶*; 浅山 泰

第29回動力・エネルギー技術シンポジウム予稿集(インターネット), 5 Pages, 2025/06

高速炉が設計で想定される期間を超えて供用される場合における構造健全性評価に利用可能な材料監視試験技術として、主として材料の熱膨張差を利用した受動式クリープ疲労試験技術を確立するための研究に取り組んでいる。これまでに、有限要素法による数値解析を援用して設計・製作した試験体を用いた実験を実施し、試験片を座屈させることなく長時間データを取得可能である見通しを得ている。本報では、これらの解析及び実験に加え、実炉への適用を見据えた試験体の改良について述べる。

東海再処理施設周辺の環境放射線モニタリング結果; 2023年度

國分 祐司; 細見 健二; 永岡 美佳; 瀬谷 夏美; 井上 和美; 小池 優子; 内山 怜; 佐々木 一樹; 前原 勇志; 松尾 一樹; et al.

JAEA-Review 2024-054, 168 Pages, 2025/03

JAEA-Review-2024-054.pdf:2.73MB

核燃料サイクル工学研究所では、「日本原子力研究開発機構核燃料サイクル工学研究所再処理施設保安規定、第IV編環境監視」に基づき、再処理施設周辺の環境放射線モニタリングを実施している。本報告書は、2023年4月から2024年3月までの間に実施した環境放射線モニタリングの結果、及び大気、海洋への放射性物質の放出に起因する周辺公衆の線量算出結果について、取りまとめたものである。なお、上記の環境放射線モニタリングの結果において、2011年3月に発生した東京電力株式会社(2016年4月1日付けで東京電力ホールディングス株式会社に変更)福島第一原子力発電所事故で放出された放射性物質の影響が一部の項目でみられた。また、環境監視計画の概要、測定方法の概要、測定結果及びその経時変化、気象統計結果、放射性廃棄物の放出状況、平常の変動幅の範囲を外れた値の評価について付録として収録した。

Symmetry-reduced topological interface for unleashing a multidirectional spin-orbit torque

杉本 聡志*; 荒木 康史; 高橋 有紀子*; 家田 淳一; 葛西 伸哉*

Communications Physics (Internet), 8, p.100_1 - 100_9, 2025/03

https://doi.org/10.1038/s42005-025-02024-1

Current-induced spin-orbit torque (SOT) at heavy metal/ferromagnet (HM/FM) interfaces plays a critical role in modern spintronics. The challenges in SOT research are to enhance the conversion efficiency and generate unconventional torque components. Here, we propose a simple protocol to meet such demands by engineering symmetrical structures, specifically by a wedge-shaped topological material interface in R-3m BiTe (001)/FM heterostructures. The symmetry of the topological interface is manipulated to lead to unconventional emergences of both out-of-plane and in-plane spin polarizations. Torque measurements show that these polarizations have conversion efficiencies up to 10 percent. This considerable improvement in the SOT efficiency is characterized both qualitatively and quantitatively based on the nonreciprocal ferromagnetic resonance (FMR) spectra and the SOT dependence on the magnetic field direction. The observed enhancement in the unconventional SOT is attributed to the wedge-oriented symmetry reduction of the spin-momentum locking structure of interfacial Dirac fermions. This advance opens new avenues for designing geometrically novel spintronics devices, demonstrating the potential of using multidirectional SOTs for forthcoming nanotechnological applications.

Development of time-series point cloud data changes and automatic structure recognition system using Unreal Engine

加藤 徹*; 高橋 弘毅*; 山下 圏*; 土井 章男*; 今渕 貴志

Artificial Life and Robotics, 30(1), p.126 - 135, 2025/02

https://doi.org/10.1007/s10015-024-00983-2

We have developed a point cloud processing system within the Unreal Engine to analyze changes in large time-series point cloud data collected by laser scanners and extract structured information. Currently, human interaction is required to create CAD data associating with the time-series point cloud data. The Unreal Engine, known for its 3D visualization capabilities, was chosen due to its suitability for data visualization and automation. Our system features a user interface that automates update procedures with a single button press, allowing for efficient evaluation of the interface's effectiveness. The system effectively visualizes structural changes by extracting differences between pre- and post-change data, recognizing shape variations, and meshing the data. Difference extraction involves isolating only the added or deleted point clouds between the two datasets using the K-D tree method. Subsequent shape recognition utilizes pre-prepared training data associated with pipes and tanks, improving accuracy through classification into nine types and leveraging PointNet++ for deep learning recognition. Meshing of the shape-recognized point clouds, particularly those to be added, employs the Ball Pivoting Algorithm (BPA), which was proven effective. Finally, the updated structural data is visualized by color-coding added and removed data in red and blue, respectively, within the Unreal Engine. Despite increased processing time with a higher number of point cloud data, down sampling prior to difference extraction signific reduces the automatic update time, enhancing overall efficiency.

Adsorption structures and bonding states of cesium and barium adsorbed on various sites of vermiculite

山口 瑛子; 奥村 雅彦; 河村 直己*; 高橋 嘉夫*

Science of the Total Environment, 964, p.178585_1 - 178585_13, 2025/02

https://doi.org/10.1016/j.scitotenv.2025.178585

粘土鉱物の吸着反応にはまだ未解明な点が多く残されており、その原因の一つは吸着サイトが複数存在することである。それぞれの吸着サイトの寄与量は吸着イオンの濃度に依存することが知られており、主に高濃度試料を分析する原子レベルでの研究結果と低濃度試料が多い環境試料の分析結果の包括的な理解に課題がある。そこで本研究では、放射光を用いた実験や第一原理計算を組み合わせることで、吸着濃度に応じて吸着サイト及び吸着イオンの局所構造が系統的に変化する様子を原子レベルで捉え、吸着イオンと粘土鉱物の相互作用がイオン結合的であることを示した。

Interpretation of vertical migration and enrichment processes of rare earth elements (REEs) in ion-adsorption-type mineralization in Japan based on REE speciation analyses

長澤 真*; 清水 祐輔*; 山口 瑛子; 徳永 紘平; 向井 広樹*; 青柳 登; Mei, H.; 高橋 嘉夫*

Chemical Geology, 670, p.122431_1 - 122431_25, 2024/12

https://doi.org/10.1016/j.chemgeo.2024.122431

Typical vertical profiles of ion-adsorption type rare earth element deposits (REE-IADs) discovered in the central Japan were studied by various speciation analyses including X-ray absorption fine structure (XAFS) and laser-induced fluorescence (LIF) spectroscopy combined with transmission electron microscope (TEM) and adsorption/desorption experiments. The results revealed that REE speciation, migration and enrichment in the weathered granite is largely controlled by soil pH which control the variable charges of kaolinite as the REE host phase. The distribution coefficient Kd, together with the soil pH, increases as the depth increase, resulting in (i) REE dissolution and migration in upper layers near the surface acidic environment where hydroxyls of kaolinite basal surfaces and edges are deprotonated to a lesser degree and (ii) REE accumulation in relatively high pH environment below the surface where hydroxyls of kaolinite basal surfaces and edges deprotonated to a larger degree to produce variable charges as adsorption sites for REEs. The increase of soil pH above 6 in deeper layers promotes inner-sphere complexation of REEs. The inner-sphere complexation inhibits the ion-exchange extraction of REEs, but the inner-sphere complexes can be still extracted by lowering the pH, which suggests the adsorption of inner- and outer-sphere complexes is reversible. This fact is important both from (i) understanding of vertical profile of REE with variation of pH and (ii) effective recovery of REE from weathered granite at all the depths in the enriched layer.

歯中炭酸ラジカルの電子スピン共鳴法測定におけるマイクロ波パワーの検討

岩見 聡音*; 山下 琢磨*; 光安 優典*; 小野 健太*; 岡 壽崇; 高橋 温*; 木野 康志*; 関根 勉*; 清水 良央*; 千葉 美麗*; et al.

KEK Proceedings 2024-6, p.91 - 95, 2024/12

ESR線量計測法の検出限界線量の改善を目指している。本研究では、ESR測定時にマイクロ波出力を変化させ、各ラジカルの飽和挙動を調べた。炭酸ラジカルと有機ラジカルのスピン緩和時間の違いから、マイクロ波出力を4.0mWにすると、S/N比が改善し検出限界線量を引き下げることができるという見込みを得た。

レーザー駆動中性子源を用いた非破壊分析技術の開発

小泉 光生; 伊藤 史哲*; Lee, J.; 弘中 浩太; 高橋 時音; 鈴木 敏*; 有川 安信*; 安部 勇輝*; Wei, T.*; 余語 覚文*; et al.

第45回日本核物質管理学会年次大会会議論文集(インターネット), 4 Pages, 2024/11

Neutron resonance transmission analysis (NRTA) is a non-destructive method applicable for measuring nuclear material using a time-of-flight (TOF) technique with a pulsed neutron source. To realize a high resolution compact NRTA system, use of a short-pulsed neutron source is essential. Laser-driven neutron sources (LDNSs) are well-suit for generating such neutron beams due to their short pulse width. The advances in laser technology will further reduce the system's size and improve practicality. In this study, we demonstrate the measurement of a neutron transmission TOF spectrum of a sample containing indium and silver using the LDNS of the Osaka University. The obtained spectrum was analyzed using the least-square nuclear-resonance fitting program, REFIT, showcasing for the first time the potential of an LDNS for nondestructive areal-density material characterization.

Demonstration of shape analysis of neutron resonance transmission spectrum measured with a laser-driven neutron source

小泉 光生; 伊藤 史哲*; Lee, J.; 弘中 浩太; 高橋 時音; 鈴木 敏*; 有川 安信*; 安部 勇輝*; Lan, Z.*; Wei, T.*; et al.

Scientific Reports (Internet), 14, p.21916_1 - 21916_9, 2024/09

https://doi.org/10.1038/s41598-024-72836-8

Laser-driven neutron sources (LDNSs) can generate strong short-pulse neutron beams, which are valuable for scientific studies and engineering applications. Neutron resonance transmission analysis (NRTA) is a nondestructive technique used for determining the areal density of each nuclide in a material sample using pulsed thermal and epithermal neutrons. Herein, we report the first successful NRTA performed using an LDNS driven by the Laser for Fast Ignition Experiment at the Institute of Laser Engineering, Osaka University. The key challenge was achieving a well-resolved resonance transmission spectrum for material analysis using an LDNS with a limited number of laser shots in the presence of strong background noise. We addressed this by employing a time-gated Li-glass scintillation neutron detector to measure the transmission spectra, reducing the impact of electromagnetic noise and neutron and gamma-ray flashes. Output waveforms were recorded for each laser shot and analyzed offline using a counting method. This approach yielded a spectrum with distinct resonances, which were attributed to In and Ag, as confirmed through neutron transmission simulation. The spectrum was analyzed using the least-square nuclear-resonance fitting program, REFIT, demonstrating the possibility of using an LDNS for nondestructive areal-density material characterization.

Quantification of radicals in aqueous solution by positronium lifetime; An Experiment using a clinical PET scanner

田久 創大*; 松本 謙一郎*; 平出 哲也; 錦戸 文彦*; 赤松 剛*; 田島 英朗*; 高橋 美和子*; 山谷 泰賀*

Japanese Journal of Applied Physics, 63(8), p.086003_1 - 086003_8, 2024/08

https://doi.org/10.35848/1347-4065/ad679a

陽電子と電子は、生体内で結合状態をとることがあり、ポジトロニウム(Ps)と呼ぶ。三重項Ps(ortho-Ps)が消滅するのにかかる時間はortho-Psピックオフ消滅寿命と言い、周囲の電子密度に応じて変化する。この寿命値はPETスキャン情報に新しい生物学的情報を追加できる可能性がある。ortho-Ps寿命による生体内の(フリー)ラジカルの定量化の実現可能性を議論するために、我々は臨床PETシステムを使用してラジカルを含む水溶液中のPs寿命を測定した。結果は、陽電子消滅イベントの計数統計が10イベント以上であれば、数mMオーダーの水溶液中のラジカル濃度の差はoetho-Ps寿命によって定量化できることを示唆した。しかし、この濃度は、生体の生理機能で生成されるラジカル濃度よりも高かった。