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Journal Articles

Magnetoelastic anisotropy in Heusler-type Mn$$_{2-delta}$$CoGa$$_{1+delta}$$ films

Kubota, Takahide*; Takano, Daichi*; Kota, Yohei*; Mohanty, S.*; Ito, Keita*; Matsuki, Mitsuhiro*; Hayashida, Masahiro*; Sun, M.*; Takeda, Yukiharu; Saito, Yuji; et al.

Physical Review Materials (Internet), 6(4), p.044405_1 - 044405_12, 2022/04

Journal Articles

Improving the safety of the high temperature gas-cooled reactor "HTTR" based on Japan's new regulatory requirements

Hamamoto, Shimpei; Shimizu, Atsushi; Inoi, Hiroyuki; Tochio, Daisuke; Homma, Fumitaka; Sawahata, Hiroaki; Sekita, Kenji; Watanabe, Shuji; Furusawa, Takayuki; Iigaki, Kazuhiko; et al.

Nuclear Engineering and Design, 388, p.111642_1 - 111642_11, 2022/03

Following the Fukushima Daiichi Nuclear Power Plant accident in 2011, the Japan Atomic Energy Agency adapted High-Temperature engineering Test Reactor (HTTR) to meet the new regulatory requirements that began in December 2013. The safety and seismic classifications of the existing structures, systems, and components were discussed to reflect insights regarding High Temperature Gas-cooled Reactors (HTGRs) that were acquired through various HTTR safety tests. Structures, systems, and components that are subject to protection have been defined, and countermeasures to manage internal and external hazards that affect safety functions have been strengthened. Additionally, measures are in place to control accidents that may cause large amounts of radioactive material to be released, as a beyond design based accident. The Nuclear Regulatory Commission rigorously and appropriately reviewed this approach for compliance with the new regulatory requirements. After nine amendments, the application to modify the HTTR's installation license that was submitted in November 2014 was approved in June 2020. This response shows that facilities can reasonably be designed to meet the enhanced regulatory requirements, if they reflect the characteristics of HTGRs. We believe that we have established a reference for future development of HTGR.

Journal Articles

Microstructures and interface magnetic moments in Mn$$_{2}$$VAl/Fe layered films showing exchange bias

Kubota, Takahide*; Shimada, Yusuke*; Tsuchiya, Tomoki*; Yoshikawa, Tomoki*; Ito, Keita*; Takeda, Yukiharu; Saito, Yuji; Konno, Toyohiko*; Kimura, Akio*; Takanashi, Koki*

Nanomaterials (Internet), 11(7), p.1723_1 - 1723_11, 2021/07

 Times Cited Count:0 Percentile:0(Chemistry, Multidisciplinary)

Journal Articles

Unveiling spin-dependent unoccupied electronic states of Co$$_{2}$$MnGe (Ga) film via Ge (Ga) $$L_{2,3}$$ absorption spectroscopy

Yoshikawa, Tomoki*; Antonov, V. N.*; Kono, Takashi*; Kakoki, Masaaki*; Sumida, Kazuki; Miyamoto, Koji*; Takeda, Yukiharu; Saito, Yuji; Goto, Kazuki*; Sakuraba, Yuya*; et al.

Physical Review B, 102(6), p.064428_1 - 064428_7, 2020/08

 Times Cited Count:0 Percentile:0(Materials Science, Multidisciplinary)

Journal Articles

Nature of the Dirac gap modulation and surface magnetic interaction in axion antiferromagnetic topological insulator MnBi$$_{2}$$Te$$_{4}$$

Shikin, A. M.*; Estyunin, D. A.*; Klimovskikh, I. I.*; Filnov, S. O.*; Kumar, S.*; Schwier, E. F.*; Miyamoto, Koji*; Okuda, Taiichi*; Kimura, Akio*; Kuroda, Kenta*; et al.

Scientific Reports (Internet), 10, p.13226_1 - 13226_13, 2020/08

 Times Cited Count:13 Percentile:91.8(Multidisciplinary Sciences)

Journal Articles

Manipulation of saturation magnetization and perpendicular magnetic anisotropy in epitaxial Co$$_{x}$$Mn$$_{4-x}$$N films with ferrimagnetic compensation

Ito, Keita*; Yasutomi, Yoko*; Zhu, S.*; Nurmamat, M.*; Tahara, Masaki*; Toko, Kaoru*; Akiyama, Ryota*; Takeda, Yukiharu; Saito, Yuji; Oguchi, Tamio*; et al.

Physical Review B, 101(10), p.104401_1 - 104401_8, 2020/03

 Times Cited Count:3 Percentile:44.66(Materials Science, Multidisciplinary)

Journal Articles

Improving fatigue performance of laser-welded 2024-T3 aluminum alloy using dry laser peening

Sano, Tomokazu*; Eimura, Takayuki*; Hirose, Akio*; Kawahito, Yosuke*; Katayama, Seiji*; Arakawa, Kazuto*; Masaki, Kiyotaka*; Shiro, Ayumi*; Shobu, Takahisa; Sano, Yuji*

Metals, 9(11), p.1192_1 - 1192_13, 2019/11

 Times Cited Count:6 Percentile:60.45(Materials Science, Multidisciplinary)

The purpose of the present study was to verify the effectiveness of dry laser peening (DryLP), which is the peening technique without a sacrificial overlay under atmospheric conditions using femtosecond laser pulses on the mechanical properties such as hardness, residual stress, and fatigue performance. After DryLP treatment of the laser-welded 2024 aluminum alloy, the softened weld metal recovered to the original hardness of base metal, while residual tensile stress in the weld metal and heat-affected zone changed to compressive stresses. The fatigue life almost doubled at a stress amplitude of 180 MPa and increased by a factor of more than 50 at 120 MPa. As a result, DryLP was found to be more effective for improving the fatigue performance of laser-welded aluminum specimens with welding defects at lower stress amplitudes.

Journal Articles

Element-specific density of states of Co$$_{2}$$MnGe revealed by resonant photoelectron spectroscopy

Kono, Takashi*; Kakoki, Masaaki*; Yoshikawa, Tomoki*; Wang, X.*; Sumida, Kazuki*; Miyamoto, Koji*; Muro, Takayuki*; Takeda, Yukiharu; Saito, Yuji; Goto, Kazuki*; et al.

Physical Review B, 100(16), p.165120_1 - 165120_6, 2019/10

 Times Cited Count:2 Percentile:22.92(Materials Science, Multidisciplinary)

Journal Articles

Magnetic-impurity-induced modifications to ultrafast carrier dynamics in the ferromagnetic topological insulators Sb$$_{2-x}$$V$$_{x}$$Te$$_{3}$$

Sumida, Kazuki*; Kakoki, Masaaki*; Reimann, J.*; Nurmamat, M.*; Goto, Shinichi*; Takeda, Yukiharu; Saito, Yuji; Kokh, K. A.*; Tereshchenko, O. E.*; G$"u$dde, J.*; et al.

New Journal of Physics (Internet), 21(9), p.093006_1 - 093006_8, 2019/09

 Times Cited Count:6 Percentile:67.47(Physics, Multidisciplinary)

Journal Articles

Negative Te spin polarization responsible for ferromagnetic order in the doped topological insulator V$$_{0.04}$$(Sb$$_{1-x}$$Bi$$_{x}$$)$$_{1.96}$$Te$$_{3}$$

Ye, M.*; Xu, T.*; Li, G.*; Qiao, S.*; Takeda, Yukiharu; Saito, Yuji; Zhu, S.-Y.*; Nurmamat, M.*; Sumida, Kazuki*; Ishida, Yukiaki*; et al.

Physical Review B, 99(14), p.144413_1 - 144413_7, 2019/04

AA2018-0697.pdf:1.89MB

 Times Cited Count:8 Percentile:67.98(Materials Science, Multidisciplinary)

Journal Articles

Dirac gap opening and Dirac-fermion-mediated magnetic coupling in antiferromagnetic Gd-doped topological insulators and their manipulation by synchrotron radiation

Shikin, A. M.*; Estyunin, D. A.*; Surnin, Yu. I.*; Koroleva, A. V.*; Shevchenko, E. V.*; Kokh, K. A.*; Tereshchenko, O. E.*; Kumar, S.*; Schwier, E. F.*; Shimada, Kenya*; et al.

Scientific Reports (Internet), 9(1), p.4813_1 - 4813_17, 2019/03

 Times Cited Count:10 Percentile:67.98(Multidisciplinary Sciences)

Journal Articles

Preferred site occupation of 3$$d$$ atoms in Ni$$_{x}$$Fe$$_{4-x}$$N (${it x}$ = 1 and 3) films revealed by X-ray absorption spectroscopy and magnetic circular dichroism

Takata, Fumiya*; Ito, Keita*; Takeda, Yukiharu; Saito, Yuji; Takanashi, Koki*; Kimura, Akio*; Suemasu, Takashi*

Physical Review Materials (Internet), 2(2), p.024407_1 - 024407_5, 2018/02

 Times Cited Count:10 Percentile:51.54(Materials Science, Multidisciplinary)

Journal Articles

2016 Professional Engineer (PE) test preparation course "Nuclear and Radiation Technical Disciplines"

Takahashi, Naoki; Yoshinaka, Kazuyuki; Harada, Akio; Yamanaka, Atsushi; Ueno, Takashi; Kurihara, Ryoichi; Suzuki, Soju; Takamatsu, Misao; Maeda, Shigetaka; Iseki, Atsushi; et al.

Nihon Genshiryoku Gakkai Homu Peji (Internet), 64 Pages, 2016/00

no abstracts in English

Journal Articles

Carrier-mediated ferromagnetism in the magnetic topological insulator Cr-doped (Sb,Bi)$$_{2}$$Te$$_{3}$$

Ye, M.*; Li, W.*; Zhu, S.-Y.*; Takeda, Yukiharu; Saito, Yuji; Wang, J.*; Pan, H.*; Nurmamat, M.*; Sumida, Kazuki*; Ji, F.*; et al.

Nature Communications (Internet), 6, p.8913_1 - 8913_7, 2015/11

AA2015-0647.pdf:0.64MB

 Times Cited Count:43 Percentile:90.62(Multidisciplinary Sciences)

Magnetically doped topological insulators are predicted to exhibit exotic phenomena including the quantized anomalous Hall effect and a dissipationless transport, which facilitate the development of low-power-consumption devices using electron spins. The realization of the quantized anomalous Hall effect is so far restricted to the Cr-doped (Sb,Bi)$$_{2}$$Te$$_{3}$$ system at extremely low temperature; however, the microscopic origin of its ferromagnetism is poorly understood. Here we present an element-resolved study for Cr-doped (Sb,Bi)$$_{2}$$Te$$_{3}$$ using X-ray magnetic circular dichroism to unambiguously show that the long-range magnetic order is mediated by the p-hole carriers of the host lattice, and the interaction between the Sb(Te) p and Cr d states is crucial.

Journal Articles

Local electronic states of Fe$$_{4}$$N films revealed by X-ray absorption spectroscopy and X-ray magnetic circular dichroism

Ito, Keita*; Toko, Kaoru*; Takeda, Yukiharu; Saito, Yuji; Oguchi, Tamio*; Suemasu, Takashi*; Kimura, Akio*

Journal of Applied Physics, 117(19), p.193906_1 - 193906_6, 2015/05

 Times Cited Count:11 Percentile:51.82(Physics, Applied)

Journal Articles

Spectroscopic evidence of band Jahn-Teller distortion upon martensitic phase transition in Heusler-type Ni-Fe(Co)-Ga ferromagnetic shape-memory alloy films

Sumida, Kazuki*; Shirai, Kaito*; Zhu, S.-Y.*; Taniguchi, Masaki*; Ye, M.*; Ueda, Shigenori*; Takeda, Yukiharu; Saito, Yuji; Aseguinolaza, I. R.*; Barandiar$'a$n, J. M.*; et al.

Physical Review B, 91(13), p.134417_1 - 134417_6, 2015/04

 Times Cited Count:5 Percentile:28.49(Materials Science, Multidisciplinary)

JAEA Reports

Annual report of Nuclear Emergency Assistance and Training Center (April 1, 2013 - March 31, 2014)

Sato, Takeshi; Muto, Shigeo; Akiyama, Kiyomitsu; Aoki, Kazufumi; Okamoto, Akiko; Kawakami, Takeshi; Kume, Nobuhide; Nakanishi, Chika; Koie, Masahiro; Kawamata, Hiroyuki; et al.

JAEA-Review 2014-048, 69 Pages, 2015/02

JAEA-Review-2014-048.pdf:13.91MB

JAEA was assigned as a designated public institution under the Disaster Countermeasures Basic Act and under the Armed Attack Situations Response Act. Based on these Acts, the JAEA has the responsibility of providing technical support to the national government and/or local governments in case of disaster responses or response in the event of a military attack, etc. In order to fulfill the tasks, the JAEA has established the Emergency Action Plan and the Civil Protection Action Plan. In case of a nuclear emergency, NEAT dispatches specialists of JAEA, supplies the national government and local governments with emergency equipment and materials, and gives technical advice and information. In normal time, NEAT provides various exercises and training courses concerning nuclear disaster prevention to those personnel taking an active part in emergency response institutions of the national and local governments, police, fire fighters, self-defense forces, etc. in addition to the JAEA itself. The NEAT also researches nuclear disaster preparedness and response, and cooperates with international organizations. In the FY2013, the NEAT accomplished the following tasks: (1) Technical support activities as a designated public institution in cooperation with the national and local governments, etc. (2) Human resource development, exercise and training of nuclear emergency response personnel for the national and local governments, etc. (3) Researches on nuclear disaster preparedness and response, and sending useful information (4) International contributions to Asian countries on nuclear disaster preparedness and response in collaboration with the international organizations

Journal Articles

Development of a fiber-coupled laser-induced breakdown spectroscopy instrument for analysis of underwater debris in a nuclear reactor core

Saeki, Morihisa; Iwanade, Akio; Ito, Chikara; Wakaida, Ikuo; Thornton, B.*; Sakka, Tetsuo*; Oba, Hironori

Journal of Nuclear Science and Technology, 51(7-8), p.930 - 938, 2014/07

 Times Cited Count:49 Percentile:98.47(Nuclear Science & Technology)

To inspect post-accident nuclear core reactor of the TEPCO Fukushima Daiichi Nuclear Power Plant, a transportable fiber-coupled LIBS instrument was developed. The developed LIBS instrument was designed to analyze the underwater sample in high-radiation field by single-pulse breakdown with gas flow or double-pulse breakdown. To check the feasibility of the assembled fiber-coupled LIBS instrument to the inspection inside Fukushima Daiichi Nuclear Power Plant, we investigated (1) influence of radiation dose on optical transmittance of the laser delivery fiber, (2) survey of the LIBS techniques to analyze the underwater sample and (3) candidates of emission lines for analysis of the debris. By employing the selected emission lines, we demonstrated that the developed LIBS instrument can analyze the simulated debris underwater by the single-pulse breakdown with the gas flow with high signal to noise ratio.

Journal Articles

X-ray magnetic circular dichroism for Co$$_{x}$$Fe$$_{4-x}$$N (x = 0, 3, 4) films grown by molecular beam epitaxy

Ito, Keita*; Sanai, Tatsunori*; Yasutomi, Yoko*; Zhu, S.-Y.*; Toko, Kaoru*; Takeda, Yukiharu; Saito, Yuji; Kimura, Akio*; Suemasu, Takashi*

Journal of Applied Physics, 115(17), p.17C712_1 - 17C712_3, 2014/05

 Times Cited Count:15 Percentile:60.88(Physics, Applied)

Journal Articles

Development of operation and maintenance technology for HTGRs by using HTTR (High Temperature engineering Test Reactor)

Shimizu, Atsushi; Kawamoto, Taiki; Tochio, Daisuke; Saito, Kenji; Sawahata, Hiroaki; Homma, Fumitaka; Furusawa, Takayuki; Saikusa, Akio; Takada, Shoji; Shinozaki, Masayuki

Nuclear Engineering and Design, 271, p.499 - 504, 2014/05

 Times Cited Count:4 Percentile:36.81(Nuclear Science & Technology)

The long term high temperature operation using HTTR was carried out to establish the technical basis of HTGR in the high temperature test operation mode during 50-day since January till March, 2010. It is necessary to demonstrate the stability of plant during long-term operation in order to attain the stable supply of the high temperature heat to the planned heat utilization system of HTTR. Test data obtained in the operation were evaluated for the technical issues which were extracted before the operation. As the results, Stability and reliability of the components and facility was demonstrated by evaluating the heat transfer performance of high temperature components, the performance of pressure control to compensate helium gas leak, the reliability of the dynamic components such as helium gas circulators, the performance of heat-up protection of radiation shielding. Through the operation, the technical basis for the operation and maintenance technology of HTGRs was established.

94 (Records 1-20 displayed on this page)