MLF低温水素システムの運転・保守及び技術開発(20182022年度)

麻生 智一; 有吉 玄; 武藤 秀生*; 田中 茂人*

JAEA-Technology 2025-005, 51 Pages, 2025/10

JAEA-Technology-2025-005.pdf:2.47MB

J-PARCセンターの低温水素システムは、国内外からの多くのユーザーが利用する物質・生命科学実験施設(MLF)の核破砕中性子源において、発生した高エネルギー中性子を中性子散乱実験に適した冷中性子に減速(冷却)するために必要な冷凍設備で、非常に重要な設備の一つである。2008年に初めて中性子利用のためのMLF施設を稼動して以来、低温水素システムも運転と保守を継続的に続けているとともに、関連する技術開発を行っている。本報告書は、近年5年間のこれらの活動をまとめたものである。

Trial measurement for para-to-orthohydrogen back conversion under the Fe(OH) catalyst condition at J-PARC cryogenic moderator system

有吉 玄; 達本 衡輝*; 勅使河原 誠; 長谷川 巧*; 城 裕喜*; 堀川 裕加*

IOP Conference Series; Materials Science and Engineering, 1327(1), p.012155_1 - 012155_6, 2025/05

https://doi.org/10.1088/1757-899X/1327/1/012155

1.4MWの高出力運転がされている米国オークリッジ国立研究所の核破砕中性子源(SNS)では、触媒が無い液体水素循環系において、核スピン異性体の一つであるパラ水素が高強度中性子場でオルソ水素へ変換される「バックコンバージョン生成」を、近年、世界で初めて実験的に計測した。このバックコンバージョンによるパラオルソ変換量は、0.374[m/MW/day]であった。パラ水素とオルソ水素を比較すると、中性子の全断面積が2桁以上異なるため、オルソ水素の増加は得られる中性子の性能に大きく影響を与える。そのためJ-PARC水素循環系では、パラ水素状態を維持するための触媒が導入されている。しかし、触媒性能の劣化をその場かつ直接診断できる手法は開発されていないのが現状である。そこで本研究では、J-PARC水素循環系において、簡便かつ意図的にオルソ水素量を変化させる新しい手法を考案し、バックコンバージョンに相当するオルソ水素の増加を意図的に循環系内へ導入することで、触媒の動特性等を評価することを試みた。本手法による試みは、その場診断型の触媒特性評価手法の確立や、オルソ・パラ比に依存する中性子性能の算定に資する可能性を秘めるものである。

Neutron spectroscopy study on crystalline electric field excitations in NdB

山内 宏樹; 目時 直人; 綿貫 竜太*; Hong, T.*; Fernandez-Baca, J. A.*; 萩原 雅人; 益田 隆嗣*; 吉沢 英樹*; 伊藤 晋一*

Journal of the Physical Society of Japan, 94(5), p.054705_1 - 054705_8, 2025/04

https://doi.org/10.7566/JPSJ.94.054705

The -electron states of NdB were determined by observing crystalline electric field (CEF) excitations with inelastic neutron scattering experiments. Our analysis yields CEF excitation energies of 2.8, 12.4, 17.2, and 25.4 meV. The -electron states are simply described by one of -multiplets with negligibly small mixing. The ground state is the pseudo-quartet consist of the ground doublet dominated by and the first excited doublet dominated by at 2.8 meV, which is consistent with magnetic specific heat and entropy reported in earlier study. The simple -electron states in NdB are the consequence of the strong uniaxial and in-plane isotropic CEF potential due to the local structure of Nd ions with point symmetry .

令和5年度核燃料サイクル工学研究所放出管理業務報告書(排水)

國分 祐司; 細見 健二; 瀬谷 夏美; 永岡 美佳; 井上 和美; 小池 優子; 長谷川 涼; 久保田 智大; 平尾 萌; 飯澤 将伍; et al.

JAEA-Review 2024-053, 116 Pages, 2025/03

JAEA-Review-2024-053.pdf:3.26MB

本報告書は、原子力規制関係法令を受けた「再処理施設保安規定」、「核燃料物質使用施設保安規定」、「放射線障害予防規程」、「放射線保安規則」及び茨城県等との「原子力施設周辺の安全確保及び環境保全に関する協定書」、「水質汚濁防止法」並びに「茨城県条例」に基づき、令和5年4月1日から令和6年3月31日までの期間に日本原子力研究開発機構核燃料サイクル工学研究所から環境へ放出した放射性排水の放出管理結果を取りまとめたものである。再処理施設、プルトニウム燃料開発施設をはじめとする各施設からの放射性液体廃棄物は、濃度及び放出量ともに保安規定及び協定書等に定められた基準値を十分に下回った。

Three-dimensional reconstruction of a small piece of Ce-doped lithium glass scintillator of an optical fiber-based neutron detector using microcomputed tomography technique

石川 諒尚; 瀬川 麻里子; 藤 暢輔; 渡辺 賢一*; 増田 明彦*; 松本 哲郎*; 山崎 淳*; 吉橋 幸子*; 瓜谷 章*; 原野 英樹*

Journal of Radiation Research (Internet), p.rraf048_1 - rraf048_7, 2025/00

https://doi.org/10.1093/jrr/rraf048

An optical fiber-based neutron detector is a real-time neutron monitor for an intense neutron field. A small piece of neutron scintillator, such as Ce-doped lithium glass (Li-glass), used in the detector has a random shape with a grain size of 200-400 m. This causes shape-dependent effects on the detector response. However, it is difficult to control or clarify the micro shape due to its small size. Here we propose a technique to obtain the fine structure of a small piece of the scintillator using a microcomputed tomography (CT) system. To verify accuracy, the mass estimated based on the volume extracted from the obtained CT image was compared to the mass measured in advance using an electronic balance. In the obtained CT images, the fine shape of the small piece of Li-glass was clearly visible, and no false signals from the surrounding components were observed. The estimated mass was in good agreement with the measured value, however, a slight underestimation was observed when the total number of projection images was 2000. This was mitigated by increasing the number of projection images, and the difference between the estimated and measured mass was 1.6% when the number of the projection images was 3141. This was equivalent to the uncertainty of the measured mass. The proposed technique will be useful when high accuracy is needed, such as for medical applications.

Large spontaneous Hall effect with flexible domain control in the antiferromagnetic material TaMnP

小手川 恒*; 中村 彰良*; Huyen, V. T. N.*; 新井 祐樹*; 藤 秀樹*; 菅原 仁*; 林 純一*; 武田 圭生*; 田端 千紘; 金子 耕士; et al.

Physical Review B, 110(21), p.214417_1 - 214417_8, 2024/12

https://doi.org/10.1103/PhysRevB.110.214417

In this study, we show that the orthorhombic system TaMnP exhibits a large anomalous Hall conductivity (AHC) in spite of the small net magnetization. Neutron scattering experiment and the observation of the AH effect comprehensively suggest a dominant AF structure in TaMnP is represented by . The AHC is one of the largest among those observed in AF materials at zero fields. First-principles calculations suggest that the spin-orbit interaction originating in nonmagnetic Ta-5 electrons significantly contributes to the enhancement of Berry curvatures in the momentum space. We found that the AF domain switching is triggered by the magnetic fields along all the crystal axes. This indicates that the AF domain determining the sign of the Hall response can be controlled even through the small net magnetization symmetrically different.

Adsorption isotherm and kinetics of diffusion of water accumulated between polypropylene thin film and Si substrate; Neutron reflectivity investigation

宮崎 司*; 宮田 登*; 有馬 寛*; 下北 啓輔*; 山本 勝宏*; 竹中 幹人*; 中西 洋平*; 柴田 基樹*; 青木 裕之; 山田 悟史*; et al.

Colloids and Surfaces A; Physicochemical and Engineering Aspects, 701, p.134928_1 - 134928_8, 2024/11

https://doi.org/10.1016/j.colsurfa.2024.134928

Isotactic polypropylene (PP) thin films deposited on Si substrates were subjected to neutron reflectivity (NR) measurements under various humidity conditions to evaluate the isothermal adsorption of water accumulated between the PP layer and Si substrate, with focus on the temperature-dependence of the adsorption isotherm. The adsorption of accumulated water followed a single type II isotherm according to the Brunauer-Emmett-Teller (BET) classification, regardless of temperature. This can be attributed to the weak interactions between the PP layer and Si substrate, and between the PP layer and water molecules. Hydrophobic PP does not significantly interact with water molecules and the hydrophilic Si surface. Therefore, the interfacial water molecules are simply adsorbed on the native oxide layer on Si via simple interaction between the water molecules and the silicon oxide surface without being affected by the PP layer. Consequently, the adsorption isotherm of the accumulated water follows the single type II adsorption isotherm regardless of temperature, similar to the adsorption isotherm of water simply adsorbed on exposed silica surfaces. These weak interactions of the PP layer with the Si surface and water molecules also lead to fast diffusion kinetics for the accumulated water along the interface.

Resonance ionization spectroscopy of neodymium for determining a highly efficient two-step ionization scheme

宮部 昌文; 岩田 圭弘; 富田 英生*; 森田 真人*; 坂本 哲夫*

Spectrochimica Acta, Part B, 221, p.107036_1 - 107036_12, 2024/11

https://doi.org/10.1016/j.sab.2024.107036

ネオジム原子の2色2段階共鳴イオン化分光を行い、120個以上の偶数パリティ自動イオン化準位とそのJ値の候補を同定した。観測された自動イオン化リドベルグ系列を解析した結果、Ndのより正確なイオン化ポテンシャルとして44560.11 (43)(2) cmの値を得た。飽和法を用いて、いくつかの強いイオン化遷移の遷移断面積を測定した。その断面積から、2段階イオン化スキームのイオン化効率をスキーム断面積の公式を用いて評価し、電離効率が高く同位体マイクロイメージング装置に適用可能なイオン化スキームを決定した。

Neutron reflectivity study on the adsorption layer of polyethylene grown on Si substrate

下北 啓輔*; 山本 勝宏*; 宮田 登*; 柴田 基樹*; 中西 洋平*; 荒川 勝利*; 竹中 幹人*; 木田 拓充*; 徳満 勝久*; 田中 亮*; et al.

Langmuir, 40(30), p.15758 - 15766, 2024/07

https://doi.org/10.1021/acs.langmuir.4c01584

To investigate the structure of the interface between polyethylene films and substrates, the neutron reflectivity (NR) of deuterated polyethylene (dPE) thin films deposited on Si substrates was measured, demonstrating water accumulation at the interface, even under ambient conditions. After leaching the thermally annealed dPE films in hot p-xylene, NR measurements were conducted on the layers remaining on the substrate, clearly revealing that the adsorption layer of dPE grew during annealing and consisted of two layers, an inner adsorption layer and an outer adsorption layer, as previously proposed for amorphous polymers. The inner adsorption layer was approximately 3.7 nm thick with a density comparable to that of the bulk. The outer adsorption layer was several nanometers thick and appeared to grow insufficiently on top of the inner adsorption layer under the annealing conditions examined in this study. This study clarifying the growth of the adsorption layer of polyethylene at the interface with an inorganic substrate is useful for improving the performance of polymer/inorganic filler nanocomposites due to the wide utility of crystalline polyolefins as polymer matrix materials in nanocomposites.

Water fraction dependence of the aggregation behavior of hydrophobic fluorescent solutes in water-tetrahydrofuran

辻 勇人*; 中畑 雅樹*; 菱田 真史*; 瀬戸 秀紀*; 元川 竜平; 井上 大傑*; 江川 泰暢*

Journal of Physical Chemistry Letters (Internet), 14(49), p.11235 - 11241, 2023/12

https://doi.org/10.1021/acs.jpclett.3c02882

This work investigates the water-fraction dependence of the aggregation behavior of hydrophobic solutes in water-tetrahydrofuran (THF) and the elucidation of the role of THF using fluorescence microscopy, dynamic light scattering, neutron and X-ray scattering, as well as photoluminescence measurements. Based on the obtained results, the following model is proposed: hydrophobic molecules are molecularly dispersed in the low-water-content region (10-20 vol %), while they form mesoscopic particles upon increasing the water fraction to 30 vol percent. This abrupt change is due to the composition fluctuation of the water-THF binary system to form hydrophobic areas in THF, followed by THF-rich droplets where hydrophobic solutes are incorporated and form loose aggregates. Further increasing the water content prompts the desolvation of THF, which decreases the particle size and generates tight aggregates of solute molecules. This model is consistent with the luminescence behavior of the solutes and will be helpful to control the aggregation state of hydrophobic solutes in various applications.