Probing deformation behavior of a refractory high-entropy alloy using neutron diffraction

Zhou, Y.*; Song, W.*; Zhang, F.*; Wu, Y.*; Lei, Z.*; Jiao, M.*; Zhang, X.*; Dong, J.*; Zhang, Y.*; Yang, M.*; et al.

Journal of Alloys and Compounds, 971, p.172635_1 - 172635_7, 2024/01

https://doi.org/10.1016/j.jallcom.2023.172635

The grain orientation-dependent lattice strain evolution of a (TiZrHfNb) refractory high-entropy alloy (HEA) during tensile loading has been investigated using neutron diffraction. The equivalent strain-hardening rate of each of the primary -oriented grain families was found to be relatively low, manifesting the macroscopically weak work-hardening ability of such a body-centered cubic (BCC)-structured HEA. This finding is indicative of a dislocation planar slip mode that is confined in a few single-slip planes and leads to in-plane softening by high pile-up stresses.

meson properties in nuclear matter from dilepton spectra in a transport approach

Gubler, P.; Bratkovskaya, E.*; Song, T.*

EPJ Web of Conferences, 274, p.07015_1 - 07015_6, 2022/12

https://doi.org/10.1051/epjconf/202227407015

There is presently no consensus on how the meson mass and width will change once it is put in a dense environment such as nuclear matter. While many theoretical works exist, connecting them with experimental measurements remains non-trivial task, as the meson in nuclear matter is usually produced in relatively high-energy pA (p: proton, A: nucleus) reactions, which are generally non-equilibrium processes. In this presentation I will report on an ongoing project, attempting to simulate pA reactions in which the meson is produced in nuclei, making use of a transport approach. Results of simulations of 12 GeV/30 GeV p+C and p+Cu reactions will be presented and comparisons between obtained dilepton spectra and experimental data of the E325 experiment at KEK will be made. Furthermore, predictions for the ongoing J-PARC E16 experiment for both dilepton and spectra will be given and discussed.

Hydrogen absorption and desorption on Rh nanoparticles revealed by dispersive X-ray absorption fine structure spectroscopy

Song, C.*; Seo, O.*; 松村 大樹; 廣井 慧*; Cui, Y.-T.*; Kim, J.*; Chen, Y.*; Tayal, A.*; 草田 康平*; 小林 浩和*; et al.

RSC Advances (Internet), 10(34), p.19751 - 19758, 2020/05

https://doi.org/10.1039/D0RA03322G

To unveil the origin of the hydrogen-storage properties of rhodium nanoparticles (Rh NPs), we investigated the dynamical structural change of Rh NPs using dispersive X-ray absorption fine structure spectroscopy (XAFS). The variation of the Rh-Rh interatomic distance and Debye-Waller factor of Rh NPs with a size of 4.0 and 10.5 nm during hydrogen absorption and desorption suggested that they have a different mechanism for hydrogen absorption, which is that the hydrogen absorption on the inner site has a greater contribution than that on a surface for Rh 4.0 nm. In the case of Rh 10.5 nm, it is opposed to Rh 4.0 nm. This study demonstrates a powerful XAFS method for observing small local structural changes of metal nanoparticles and its importance for understanding of the hydrogen-absorption properties of Rh NPs with an interesting hydrogenation mechanism.

Current situation of OECD/NEA, Preparatory Study on Analysis of Fuel debris (PreADES) project

仲吉 彬; Journeau, C.*; Rempe, J.*; Barrachin, M.*; Bottomley, D.; Nauchi, Y.*; Song, J. H.*

Proceedings of 2019 International Workshop on Post-Fukushima Challenges on Severe Accident Mitigation and Research Collaboration (SAMRC 2019) (USB Flash Drive), 6 Pages, 2019/11

In recognition of the broad international interest in learning from post-accident examinations and other activities related to the Fukushima Daiichi Nuclear Power Station (1F), Japan recommended, to the Organization for Economic Co-operation and Development/Nuclear energy Agency/Committee on Safety of Nuclear Installations (OECD/NEA/CSNI) in 2013, that they identified and followed up on opportunities to address safety research gaps. The CSNI set up the Senior Expert Group (SEG) on Safety Research Opportunities Post-Fukushima (SAREF). In 2016-2017, Preparatory Study on Analysis of Fuel Debris (PreADES) project was recommended by the SEG on SAREF as a near-term project. The PreADES project will summarize the collected knowledge and expertise of debris characterization and identify the needs for debris analyses that will most contribute to the decommissioning of 1F. The project also aims to improve the understanding of severe accidents and reactor safety assessments as well as creating appropriate and optimal methodologies for future debris sampling, retrieval, and storage. Consequently, the project provides important input for a future international project of sample examination based on long-term considerations. The PreADES project launched discussions among interested organizations at the preliminary meeting in July 2017 about the objectives, scope, output, and direction of the project. The contents of the PreADES project were agreed as the three following tasks: Task 1: Joint study on fuel debris' expected properties and characterization, Task 2: Identifying needs and major issues for future fuel debris sampling, retrieval, and analyses, Task 3: Planning of future international R&D framework. Currently, 4th meeting took place on July in Tokyo Japan. Task 1 is almost completed and Task 2 will be summarized soon.

Dirac surface state-modulated spin dynamics in a ferrimagnetic insulator at room temperature

Tang, C.*; Song, Q.*; Chang, C.-Z.*; Xu, Y.*; 大沼 悠一; 松尾 衛*; Liu, Y.*; Yuan, W.*; Yao, Y.*; Moodera, J. S.*; et al.

Science Advances (Internet), 4(6), p.eaas8660_1 - eaas8660_6, 2018/06

AA2018-0166.pdf:0.7MB

https://doi.org/10.1126/sciadv.aas8660

This work demonstrates markedly modified spin dynamics of magnetic insulator (MI) by the spin momentum-locked Dirac surface states of the adjacent topological insulator (TI). As the Bi concentration is systematically tuned in 5-nm-thick (BiSb)Te TI films, the weight of the surface relative to bulk states peaks at = 0.32 when the chemical potential approaches the Dirac point. At this concentration, the Gilbert damping constant of the precessing magnetization in 10-nm-thick YFeO MI films in the MI/TI heterostructures is enhanced by an order of magnitude, the largest among all concentrations. In addition, the MI acquires additional strong magnetic anisotropy that favors the in-plane orientation with similar Bi concentration dependence. These extraordinary effects of the Dirac surface states distinguish TI from other materials such as heavy metals in modulating spin dynamics of the neighboring magnetic layer.

The Application of radiochronometry during the 4th collaborative materials exercise of the nuclear forensics international technical working group (ITWG)

Kristo, M. J.*; Williams, R.*; Gaffney, A. M.*; Kayzar-Boggs, T. M.*; Schorzman, K. C.*; Lagerkvist, P.*; Vesterlund, A.*; Ramebck, H.*; Nelwamondo, A. N.*; Kotze, D.*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 315(2), p.425 - 434, 2018/02

https://doi.org/10.1007/s10967-017-5680-5

最新の核鑑識国際共同試料分析演習では、低濃縮ウラン試料について、10か国の核鑑識ラボラトリーが精製年代測定を実施して良好な結果を得た。これらの測定のうち、3つの異なる核種ペアを用いた精製年代測定も実施された。10か国の核鑑識ラボラトリーが提出した精製年代測定の結果は、実際の精製日と概ね一致した。また、質量分析法による結果は、放射線計測法を用いたものに比べて、高精度な結果を示した。さらに、一部のラボラトリーによって示されたU-Pa法とU-Th法による精製年代測定の結果の一致は、結果の確証性を高めた。

Measurement of neutron production cross sections from heavy ion induced reaction

執行 信寛*; 魚住 祐介*; 今林 洋一*; 板敷 祐太朗*; 佐藤 大樹; 梶本 剛*; 佐波 俊哉*; 古場 裕介*; 高田 真志*; 松藤 成弘*; et al.

JAEA-Conf 2014-002, p.81 - 87, 2015/02

https://doi.org/10.11484/jaea-conf-2014-002

高エネルギー加速器施設の遮蔽設計には、原子力機構を中心に開発されているPHITSや欧州原子核研究機構を中心に開発されているFLUKAなどのモンテカルロ法に基づく放射線輸送コードが利用されている。これら放射線輸送コードの予測精度を検証するには、核反応の素過程に関する二重微分断面積の実験データとの比較が必要である。しかし、重イオン入射反応に関する実験データは乏しく、荷電粒子生成に関するものはほとんど存在しない。そこで、放射線医学総合研究所のHIMAC加速器を用い290MeV/uのAr入射反応に対する炭素原子核からの陽子,重陽子及び三重陽子生成二重微分断面積を測定した。生成した荷電粒子は、ビーム軸に対して15, 30, 45, 60, 75及び90度方向に配置した液体有機シンチレータで検出した。各荷電粒子は、飛行時間と検出器でのエネルギー損失の情報から識別できる。実験データをPHITS及びFLUKAと比較したところ、陽子生成については実験データの傾向を再現するものの、重陽子及び三重陽子生成については、両コードで全く再現できず、各コードによる計算値の間にも大きな差があることが分かった。これは、既存の核反応模型では重陽子や三重陽子の放出に必要な核子の同伴および癒着過程を適切に取り扱えていないためと考えられる。本研究で得られる知見は、放射線輸送コードにおける核反応模型の改良に貢献することが期待できる。

Commissioning results of the KSTAR neutral beam system

Bae, Y. S.*; Park, Y. M.*; Kim, J. S.*; Han, W. S.*; Kwak, S. W.*; Chang, Y. B.*; Park, H. T.*; Song, N. H.*; Chang, D. H.*; Jeong, S. H.*; et al.

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 9 Pages, 2011/03

http://www-naweb.iaea.org/napc/physics/FEC/FEC2010/html/node443.htm#86774

中性粒子入射(NBI)システムは、韓国超伝導トカマク先進研究装置(KSTAR)における高性能運転と長パルス運転のためのイオン加熱と電流駆動を行うように設計された。KSTAR用NBIは2つのビームラインで構成されている。各々のビームラインはイオン源1台あたり最大ビームエネルギー120keVで重水素中性粒子ビームパワー2.5MW以上を入射できるよう設計されたイオン源を3台内蔵している。したがって、KSTAR用NBIシステムの最終目標は2つのビームラインで重水素中性粒子ビームパワー14MW以上の入射を目指している。NBIシステムの計画に則り、各々のコンポーネントとサブシステムの試運転を含めた2010年活動においては、最初のNBIシステムにより、KSTARトカマク・プラズマへ1台のイオン源からビーム入射を行うことである。この論文では、1台のイオン源を用いた最初のNBIシステムの建設と調整運転について紹介する。

核融合原型炉SlimCSの概念設計

飛田 健次; 西尾 敏*; 榎枝 幹男; 中村 博文; 林 巧; 朝倉 伸幸; 宇藤 裕康; 谷川 博康; 西谷 健夫; 礒野 高明; et al.

JAEA-Research 2010-019, 194 Pages, 2010/08

JAEA-Research-2010-019-01.pdf:48.47MB
JAEA-Research-2010-019-02.pdf:19.4MB

発電実証だけでなく、最終的には経済性までを一段階で見通しうる核融合原型炉SlimCSの概念設計の成果を報告する。核融合の開発では、これまで、1990年に提案されたSSTR(Steady State Tokamak Reactor)が標準的な原型炉概念とされてきたが、本研究はSSTRより軽量化を図るため小規模な中心ソレノイドを採用して炉全体の小型化と低アスペクト比化を図り、高ベータ及び高楕円度(グリーンワルド密度限界を高めうる)を持つ炉心プラズマにより高出力密度を目指した。主要パラメータは、プラズマ主半径5.5m,アスペクト比2.6,楕円度2.0,規格化ベータ値4.3,核融合出力2.95GW,平均中性子壁負荷3MW/mとした。この炉概念の技術的成立性を、プラズマ物理,炉構造,ブランケット,超伝導コイル,保守及び建屋の観点から検討した。

Systematic changes of the electronic structure of the diluted ferromagnetic oxide Li-doped NiFeO with hole doping

小林 正起*; Hwang, J. I.*; Song, G.*; 大木 康弘*; 滝沢 優*; 藤森 淳; 竹田 幸治; 藤森 伸一; 寺井 恒太*; 岡根 哲夫; et al.

Physical Review B, 78(15), p.155322_1 - 155322_4, 2008/10

https://doi.org/10.1103/PhysRevB.78.155322

The electronic structure of Li-doped NiFeO has been investigated using photoemission spectroscopy (PES) and X-ray absorption spectroscopy (XAS). The Ni core-level PES and XAS spectra were not changed by Li doping. In contrast, the Fe intensity increased with Li doping relative to the Fe intensity. However, the increase of Fe is only of the doped Li content, suggesting that most of the doped holes enter the O and/or the charge-transferred configuration Ni . The Fe partial density of states and the host valence-band emission near valence-band maximum increased with Li content, consistent with the increase of electrical conductivity. Based on these findings, percolation of bound magnetic polarons is proposed as an origin of the ferromagnetic behavior.