燃料ピンバンドル変形解析コード"BAMBOO"への摩擦モデルの導入

上羽 智之; 伊藤 昌弘*; 石谷 行生*

JAEA-Technology 2023-006, 36 Pages, 2023/05

JAEA-Technology-2023-006.pdf:3.45MB

日本原子力研究開発機構で開発しているBAMBOOコードは、高速炉用のワイヤスペーサ型炉心燃料集合体における燃料ピンバンドルの変形を解析するコードである。本研究では、燃料ピンとダクトとの相互作用により生じた隣接する燃料ピン同士や最外周の燃料ピンとダクトとの接触部に対して摩擦を考慮するモデルを開発した。これは、BAMBOOの接触・分離解析の中で摩擦力を考慮するモデルであり、摩擦が生じた場合に解析が数値的に不安定になる状況を避けるため、収束計算によって摩擦力を徐々に変化させていき確定するようにした。モデルの解析機能確認の結果、現実的な摩擦係数を適用した場合、ピン-ダクト接触時期やピンバンドル内の変位の方向について摩擦の影響が僅かに認められた。

X線イメージングを用いた球充填層内のボイド率分布計測

山本 誠士郎*; 大平 直也*; 伊藤 大介*; 伊藤 啓*; 齊藤 泰司*; 今泉 悠也; 松場 賢一; 神山 健司

混相流, 37(1), p.79 - 85, 2023/03

In the safety study on a sodium-cooled fast reactor, it is assumed that the high temperature fuel debris are formed because of a core disruptive accident. During the cooling of the fuel debris, gas-liquid two-phase flow can be generated in the debris due to the coolant boiling. To improve the prediction accuracy of the flow characteristics, detailed measurement of the gas-liquid two-phase flow in the debris bed is required. In this study, gas-liquid two-phase flow in a quasi-two-dimensional sphere-packed bed, which simulates the debris bed, is visualized by using X-ray imaging. The experimental results show that the local void fraction increases near the splitting section in the packed bed and decreases near the coalescence section.

Unusually kinetically inert monocationic neptunyl complex with a fluorescein-modified 1,10-phenanthroline-2,9-dicarboxylate ligand; Specific separation and detection in gel electrophoresis

山縣 和仁*; 大内 和希; 丸茂 和樹*; 半田 友衣子*; 原賀 智子; 齋藤 伸吾*

Inorganic Chemistry, 62(2), p.730 - 738, 2023/01

https://doi.org/10.1021/acs.inorgchem.2c02908

ネプツニルイオン(NpO)に対し解離不活性な錯体を見出すため、蛍光プローブ化学ライブラリーの中からポリアクリルアミドゲル電気泳動(PAGE)を用いる速度論的手法により、安定なNpO錯体の選抜を試みた。フルオレセイン修飾フェナントロリン-2,9-ジカルボン酸錯体は、自己解離速度定数810 sと非常に解離不活性であることを見出した。この速度定数は、これまで報告されているNpO錯体の解離速度より100万倍遅い。この特異性を利用しPAGEによるNpO錯体の蛍光検出を試みたところ、検出限界68pmol dm(17fg)の極微量検出を達成した。模擬使用済み核燃料及び高レベル放射性廃棄物試料への適用にも成功した。

Spin and spin current; From fundamentals to recent progress

前川 禎通; 吉川 貴史*; 中堂 博之; 家田 淳一; 齊藤 英治

Journal of Applied Physics, 133(2), p.020902_1 - 020902_24, 2023/01

https://doi.org/10.1063/5.0133335

Along with the progress of spin science and spintronics research, the flow of electron spins, i.e., spin current, has attracted interest. New phenomena and electronic states were explained in succession using the concept of spin current. Moreover, as many of the conventionally known spintronics phenomena became well organized based on spin current, it has rapidly been recognized as an essential concept in a wide range of condensed matter physics. In this article, we focus on recent developments in the physics of spin, spin current, and their related phenomena, where the conversion between spin angular momentum and different forms of angular momentum plays an essential role. Starting with an introduction to spin current, we first discuss the recent progress in spintronic phenomena driven by spin-exchange coupling: spin pumping, topological Hall torque, and emergent inductor. We, then, extend our discussion to the interaction/interconversion of spins with heat, lattice vibrations, and charge current and address recent progress and perspectives on the spin Seebeck and Peltier effects. Next, we review the interaction between mechanical motion and electron/nuclear spins and argue the difference between the Barnett field and rotational Doppler effect. We show that the Barnett effect reveals the angular momentum compensation temperature, at which the net angular momentum is quenched in ferrimagnets.

Laser-driven neutron generation realizing single-shot resonance spectroscopy

余語 覚文*; Lan, Z.*; 有川 安信*; 安部 勇輝*; Mirfayzi, S. R.*; Wei, T.*; 森 隆人*; Golovin, D.*; 早川 岳人*; 岩田 夏弥*; et al.

Physical Review X, 13(1), p.011011_1 - 011011_12, 2023/01

https://doi.org/10.1103/PhysRevX.13.011011

Neutrons are powerful tools for investigating the structure and properties of materials used in science and technology. Recently, laser-driven neutron sources (LDNS) have attracted the attention of different communities, from science to industry, in a variety of applications, including radiography, spectroscopy, security, and medicine. However, the laser-driven ion acceleration mechanism for neutron generation and for establishing the scaling law on the neutron yield is essential to improve the feasibility of LDNS. In this paper, we report the mechanism that accelerates ions with spectra suitable for neutron generation. We show that the neutron yield increases with the fourth power of the laser intensity, resulting in the neutron generation of in at a maximum, with Wcm, 900 J, 1.5 ps lasers. By installing a "hand-size" moderator, which is specially designed for the LDNS, it is demonstrated that the efficient generation of epithermal (0.1-100 eV) neutrons enables the single-shot analysis of composite materials by neutron resonance transmission analysis (NRTA). We achieve the energy resolution of 2.3% for 5.19-eV neutrons 1.8 m downstream of the LDNS. This leads to the analysis of elements and isotopes within sub-s times and allows for high-speed nondestructive inspection.

Spontaneous topological Hall effect induced by non-coplanar antiferromagnetic order in intercalated van der Waals materials

高木 寛貴*; 高木 里奈*; 見波 将*; 野本 拓也*; 大石 一城*; 鈴木 通人*; 柳 有起*; 平山 元昭*; Khanh, N.*; 軽部 皓介*; et al.

Nature Physics, p.1 - 8, 2023/00

https://doi.org/10.1038/s41567-023-02017-3

In ferromagnets, electric current generally induces a transverse Hall voltage in proportion to the internal magnetization. This effect is frequently used for electrical readout of the spin up and down states. While these properties are usually not expected in antiferromagnets, recent theoretical studies predicted that non-coplanar antiferromagnetic order with finite scalar spin chirality - meaning a solid angle spanned by neighboring spins - can induce a large spontaneous Hall effect even without net magnetization or external magnetic field. This phenomenon, the spontaneous topological Hall effect, can potentially be used for the efficient electrical readout of the antiferromagnetic states, but it has not been experimentally verified due to a lack of appropriate materials hosting such magnetism. Here, we report the discovery of all-in-all-out type non-coplanar antiferromagnetic order in triangular lattice compounds CoTaS and CoNbS. These compounds are reported to host unconventionally large spontaneous Hall effect despite their vanishingly small net magnetization, and our analysis reveals that it can be explained in terms of the topological Hall effect that originates from the fictitious magnetic field associated with scalar spin chirality. These results indicate that the scalar spin chirality mechanism offers a promising route to the realisation of giant spontaneous Hall response even in compensated antiferromagnets, and highlight intercalated van der Waals magnets as a promising quasi-two-dimensional material platform to enable various nontrivial ways of electrical reading and possible writing of non-coplanar antiferromagnetic domains.

New isomers in Cf

Orlandi, R.; 牧井 宏之; 西尾 勝久; 廣瀬 健太郎; 浅井 雅人; 塚田 和明; 佐藤 哲也; 伊藤 由太; 洲嵜 ふみ; 永目 諭一郎*; et al.

Physical Review C, 106(6), p.064301_1 - 064301_11, 2022/12

https://doi.org/10.1103/PhysRevC.106.064301

The nuclear structure of Cf produced by the O+Cf multinucleon transfer reaction was investigated using -ray spectroscopy. Analysis of the -ray spectrum of Cf revealed the presence of multiple long-lived (isomeric) excited states at low excitation energies. The energies and half-lives of the isomers contain information on the proton and neutron orbits in the heavy-element region and the deformation of atomic nuclei, and are important data to predict the properties of nuclei in the "island of stability".

Measurements of pressure drop and void fraction of air-water two-phase flow in a sphere-packed bed

山本 誠士郎*; 大平 直也*; 伊藤 大介*; 伊藤 啓*; 齊藤 泰司*; 今泉 悠也; 松場 賢一; 神山 健司

Proceedings of 12th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS12) (Internet), 4 Pages, 2022/10

To develop a microscopic pressure drop prediction model based on detailed measurement data of gas liquid two-phase flow, the pressure drop was measured in the vertical upward gas-liquid two-phase flow formed in quasi-2D test section. The measurement results showed that the pressure drop in the quasi-2D test section was much smaller than that in the ordinal packed bed system, which suggests that the pressure drop mechanism in the quasi-2D test section could be different from that in the ordinal packed bed system due to differences in two-phase flow characteristics in the two systems. The void fraction distribution was also measured in the quasi-2D test section by the X-ray imaging technique, which revealed that there was a local distribution of the void fraction in the channel unit structure of the closest packed bed.

Rotation of complex ions with ninefold hydrogen coordination studied by quasielastic neutron scattering and first-principles molecular dynamics calculations

大政 義典*; 高木 茂幸*; 戸嶋 健人*; 横山 凱乙*; 遠藤 亘*; 折茂 慎一*; 齋藤 寛之*; 山田 武*; 川北 至信; 池田 一貴*; et al.

Physical Review Research (Internet), 4(3), p.033215_1 - 033215_9, 2022/09

https://doi.org/10.1103/PhysRevResearch.4.033215

Quasielastic neutron scattering (QENS) and neutron powder diffraction of the complex transition metalhydrides LiMoH and LiNbH were measured in a temperature range of 10-300 K to study their structures and dynamics, especially the dynamics of the hydrogen atoms. These hydrides contain unusual ninefold H coordinated complex ions (MoH or NbH) and hydride ions (H). A QENS signal appeared 150 K due to the relaxation of H atoms. The intermediate scattering functions derived from the QENS spectra are well fitted by a stretched exponential function called the Kohlrausch-Williams-Watts functions with a small stretching exponent 0.3-0.4, suggesting a wide relaxation time distribution. The dependence of the elastic incoherent structure factor is reproduced by the rotational diffusion of MH (M = Mo or Nb) anions. The results are well supported by a van Hove analysis for the motion of H atoms obtained using first-principles molecular dynamics calculations. We conclude that the wide relaxation time distribution of the MH rotation is due to the positional disorder of the surrounding Li ions and a unique rotation with MH anion deformation (pseudorotation).

Influence of pulse duration on mechanical properties and dislocation density of dry laser peened aluminum alloy using ultrashort pulsed laser-driven shock wave

吉田 雅幸*; 西端 樹*; 松田 朋己*; 伊藤 佑介*; 杉田 直彦*; 城 鮎美*; 菖蒲 敬久; 荒河 一渡*; 廣瀬 明夫*; 佐野 智一*

Journal of Applied Physics, 132(7), p.075101_1 - 075101_9, 2022/08

https://doi.org/10.1063/5.0083511

This study aims to investigate the influence of the pulse duration on the mechanical properties and dislocation density of a aluminum alloy treated using dry laser peening. The results of the micro-Vickers hardness test, residual stress measurement, and dislocation density measurement demonstrate that over a pulse duration range of 180 fs to 10 ps, the maximum peening effects are achieved with a pulse duration of 1 ps. Moreover, the most significant dry laser peening effects are obtained by choosing a pulse duration that achieves a laser intensity that simultaneously generates the strongest shock pressure, suppresses optical nonlinear effects, and realizes the least thermal effects, which weaken the shock effects.