Phase diagram of the polystyrene/near-critical water system

柴田 基樹*; 竹中 幹人*; 元川 竜平; 熊田 高之; 上田 祐生; 宮崎 司*; 中西 洋平*; 阿部 淳*; 岩瀬 裕希*; 柴山 充弘*; et al.

Polymer, 340, p.129203_1 - 129203_7, 2025/12

https://doi.org/10.1016/j.polymer.2025.129203

The development of effective plastic degradation methods is crucial to address environmental pollution. Hydrothermal liquefaction using near-critical water is a promising technology, but the fundamental dissolution and decomposition mechanisms remain poorly understood. This study investigates the thermodynamics of a polystyrene (PS)/water system under near-critical conditions to elucidate this mechanism. We performed in situ small-angle neutron scattering (SANS) to observe the swelling of PS particles in deuterated water (DO) at various temperatures under pressures of 10 MPa and 25 MPa. By applying the (FHS) theory to the swelling data, We quantitatively determined the Flory-Huggins interaction parameter as a function of temperature and pressure by applying the FHS theory to the swelling data. Based on these results, we constructed a phase diagram of the PS/DO system. The diagram reveals that miscibility increases with increasing pressure. This work provides a thermodynamical properties of water solutions of polymers under near-critical conditions for optimizing industrial hydrothermal recycling processes.

Status of J-PARC accelerator chain

山本 風海; 小栗 英知; 森下 卓俊; 山本 昌亘; 神谷 潤一郎; 篠崎 信一; 發知 英明*; 佐藤 洋一*; Fang, Z.*

Proceedings of 16th International Particle Accelerator Conference (IPAC25) (Internet), p.1128 - 1131, 2025/11

https://doi.org/10.18429/JACoW-IPAC2025-TUPB074

J-PARCは大強度陽子ビームを用いて中性子や中間子、ニュートリノ等様々な二次粒子を大量に生成し、物質・生命科学研究施設(MLF)、ハドロン実験施設、ニュートリノ標的に供給している。このような大強度陽子加速器では、わずか0.1%未満のビーム損失であっても深刻な放射化や加速器機器の故障など、様々な問題を引き起こす可能性がある。ビーム損失を十分に低減した状態で大出力運転を実現するため、機器の高度化およびビーム調整を継続している。これらの努力を通じて、MLF利用者向けに1MWのビーム出力運転、ニュートリノ利用者向けに830kWのビーム出力運転を確立した。しかし一方で、初段加速器であるリニアックが運転を開始してより20年近くが経過しており、経年劣化による機器故障等も発生している。それらについては、原因を究明し対策を行うことで、安定運転の維持に努めている。

Self-reconstruction of order parameter in spin-triplet superconductor UTe

常盤 欣文; Opletal, P.; 酒井 宏典; 久保 勝規; 神戸 振作; 山本 悦嗣; 木俣 基; 淡路 智*; 佐々木 孝彦*; 青木 大*; et al.

Physical Review Letters, 135(13), p.136502_1 - 136502_6, 2025/09

https://doi.org/10.1103/z8yx-yzdh

UTeにおける軸方向の容易軸メタ磁性クロスオーバーが超伝導に及ぼす影響を、交流磁化率、磁化、および磁気熱量効果の測定によって調べた。高品質な単結晶試料において、5.6Tで超伝導状態内におけるメタ磁性に駆動された磁場誘起相転移を確認した。この相転移により高磁場超伝導状態が形成され、上部臨界磁場は12Tまで大幅に増大する。転移点でのエントロピーの急激な増加は秩序変数の自己再構成を示唆しており、多成分超伝導状態が外部摂動に適応するメカニズムを示している。

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。

Observation of nonreciprocal diffraction of surface acoustic wave

新居 陽一*; 山本 慧; 菅野 将誠*; 前川 禎通*; 小野瀬 佳文*

Physical Review Letters, 134(2), p.027001_1 - 027001_5, 2025/01

https://doi.org/10.1103/PhysRevLett.134.027001

While the rectification phenomenon caused by the simultaneous breaking of time reversal and spatial inversion symmetries has been extended to a wide range of (quasi)particles and waves, the nonreciprocal diffraction, which is the imbalance of upward and downward deflections, was previously observed only for photons and remained to be extended to other (quasi)particles. Here, we present evidence of the nonreciprocal diffraction of surface acoustic wave (SAW) utilizing a magnetoelastic grating on a SAW device. Asymmetric diffraction intensities were observed when the ferromagnetic resonance was acoustically excited. Based on a theoretical model, we ascribe the microscopic origin of this phenomenon to the resonant scattering involving ferromagnetic resonance excitations. The novel property may pave an avenue to further development of SAW devices for various purposes including microwave communications and quantum engineering applications.

廃止措置・廃炉化学入門

佐藤 修彰*; 亀尾 裕; 佐藤 宗一; 熊谷 友多; 佐藤 智徳; 山本 正弘*; 渡邉 豊*; 永井 崇之; 新堀 雄一*; 渡邉 雅之; et al.

廃止措置・廃炉化学入門, 251 Pages, 2024/09

原子力施設の廃止措置と過酷事故炉の廃炉を対象とし、第1部では燃料化学、分析化学、放射線化学、腐食、除染化学から、廃棄物処理・処分にわたる基礎的な分野について紹介する。第2部では、種々の原子力関連施設の廃止措置に関わる化学を学びながら、東京電力福島第一原子力発電所の廃炉にはどのような化学的アプローチが必要かつ可能か、廃炉の在り方やそれに必要な研究開発・人材育成などについて触れる。

Study on vertical sloshing load acting on roof of cylindrical tanks under seismic wave excitation

池末 俊一*; 岩崎 晃久*; 佐郷 ひろみ*; 横井 忍*; 山本 智彦

Proceedings of the ASME 2024 Pressure Vessels & Piping Conference (PVP 2024) (Internet), 9 Pages, 2024/07

During an earthquake, sloshing occurs in a cylindrical tank when a frequency component close to the natural frequency of sloshing is included in the seismic wave. When high amplitude sloshing occurs, the free liquid surface level fluctuates greatly in the tank, and the liquid surface collides with the roof of the tank. In tank design, it is important to evaluate the sloshing load acting on the roof. In this study, we extended this method to deal with seismic wave excitation. In seismic wave excitation, the tank is excited by irregular wave, and the phenomenon of sloshing becomes more complicated than sinusoidal excitation. To simplify this complicated phenomenon, we proposed a concept of equivalent growth wave number. This number represents the magnitude of the increase in the peak of liquid surface level, during seismic wave excitation. We proposed a method to quantitatively evaluate this number from seismic response analysis. In addition, we proposed a method to evaluate the vertical load on the roof during seismic wave excitation, by introducing this number into the predictive evaluation method.

Current status of development in the 3D seismic isolation applied to SFRs

山本 智彦; 渡壁 智祥; 宮崎 真之; 岡村 茂樹; 宮川 高行; 横井 忍*; 深沢 剛司*; 藤田 聡*

Mechanical Engineering Journal (Internet), 11(2), p.23-00393_1 - 23-00393_21, 2024/04

https://doi.org/10.1299/mej.23-00393

A sodium-cooled fast reactor (SFR) considers adopting 3-dimensional seismic isolation devices for withstanding seismic loads not only horizontal but also vertical direction. A seismic isolation device consists of a laminated rubber bearing and horizontal oil dampers for horizontal direction, coned disc springs and vertical oil dampers for vertical direction, respectively. In order to investigate the performance of each component and the feasibility of integrated system for SFR, the experiments such as load-displacement tests, vibrating tests, etc., to each component of seismic isolation devices and seismic response analysis are carried out. As those experimental results, the mechanical characteristics of each component and the devices are grasped, then it is demonstrated that components and devices have expected performances to reduce the seismic loading within the design range. As the analytical results of seismic response, it is indicated that this 3-dimesional seismic isolation device and system can reduce the seismic response on horizontal and vertical simultaneously. Based on the analytical studies and experimental results, the feasibility of newly developed 3-dimensional seismic isolation system is obtained and the prospect of practical application of 3D seismic isolation system for fast reactor is implied in this paper.

Reinforcement of superconductivity by quantum critical fluctuations of metamagnetism in UTe

常盤 欣文; Opletal, P.; 酒井 宏典; 神戸 振作; 山本 悦嗣; 木俣 基*; 淡路 智*; 佐々木 孝彦*; 青木 大*; 芳賀 芳範; et al.

Physical Review B, 109(14), p.L140502_1 - L140502_6, 2024/04

https://doi.org/10.1103/PhysRevB.109.L140502

超伝導体UTeの常伝導状態を軸磁場に対するエントロピー解析によって調べた。メタ磁性揺らぎ(空間一様、)による磁場によるエントロピーの強い増加が観測された。この磁場依存性は遍歴メタ磁性の量子臨界性に関するHertz-Millis-Moriya理論によってよく記述される。特に、量子臨界領域の下界は超伝導転移温度の最小値の位置とよく一致する。この結果は、の揺らぎが超伝導を強めることを示唆している。

Structural changes of polystyrene particles in subcritical and supercritical water revealed by in situ small-angle neutron scattering

柴田 基樹*; 中西 洋平*; 阿部 淳*; 有馬 寛*; 岩瀬 裕希*; 柴山 充弘*; 元川 竜平; 熊田 高之; 高田 慎一; 山本 勝宏*; et al.

Polymer Journal, 55(11), p.1165 - 1170, 2023/11

https://doi.org/10.1038/s41428-023-00817-1

Marine ecosystem degradation due to micro plastics is a significant environmental problem, as acknowledged by Sustainable Development Goal 14. Decomposition of plastics using near critical or supercritical water is one of the promising methods to reduce micro plastics. To attain the optimization of the method for improving environmental friendliness, it is necessary to clarify the structural change of materials during the process. We, thus, investigated the decomposition processes of polystyrene particles dispersed in deuterated water (DO) during heating under near critical or supercritical conditions by using in situ small-angle neutron scattering. Under subcritical conditions, the PS particles were swollen by DO due to increased compatibility with temperature. Near the critical point in subcritical conditions, the cleavage of PS chains in the particles occurred, so that the swollen ratio was much enhanced though the PS particles kept their shapes. In a supercritical condition, the PS particles were degraded into oil including oligomers or monomers and the phase-separated structures with styrene-rich and DO-rich regions.