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Omasa, Yoshinori*; Takagi, Shigeyuki*; Toshima, Kento*; Yokoyama, Kaito*; Endo, Wataru*; Orimo, Shinichi*; Saito, Hiroyuki*; Yamada, Takeshi*; Kawakita, Yukinobu; Ikeda, Kazutaka*; et al.
Physical Review Research (Internet), 4(3), p.033215_1 - 033215_9, 2022/09
Norimatsu, Wataru*; Matsuda, Keita*; Terasawa, Tomoo; Takata, Nao*; Masumori, Atsushi*; Ito, Keita*; Oda, Koji*; Ito, Takahiro*; Endo, Akira*; Funahashi, Ryoji*; et al.
Nanotechnology, 31(14), p.145711_1 - 145711_7, 2020/04
Times Cited Count:6 Percentile:38.95(Nanoscience & Nanotechnology)We show that boron-doped epitaxial graphene can be successfully grown by thermal decomposition of a boron carbide thin film, which can also be epitaxially grown on a silicon carbide substrate. The interfaces of BC on SiC and graphene on BC had a fixed orientation relation, having a local stable structure with no dangling bonds. The first carbon layer on BC acts as a buffer layer, and the overlaying carbon layers are graphene. Graphene on BC was highly boron doped, and the hole concentration could be controlled over a wide range of 210 to 210 cm. Highly boron-doped graphene exhibited a spin-glass behavior, which suggests the presence of local antiferromagnetic ordering in the spin-frustration system. Thermal decomposition of carbides holds the promise of being a technique to obtain a new class of wafer-scale functional epitaxial graphene for various applications.
Endo, Fumitaka*; Koura, Hiroyuki
Physical Review C, 99(3), p.034303_1 - 034303_8, 2019/03
Times Cited Count:3 Percentile:32.64(Physics, Nuclear)Saito, Shigeru; Obayashi, Hironari; Wan, T.; Okubo, Nariaki; Sugawara, Takanori; Endo, Shinya; Sasa, Toshinobu
Proceedings of 13th International Topical Meeting on Nuclear Applications of Accelerators (AccApp '17) (Internet), p.448 - 457, 2018/05
JAEA proposes transmutation of minor actinides by accelerator-driven systems (ADS). To obtain the data for ADS design, JAEA plans to construct the ADS Target Test Facility (TEF-T) within the framework of the J-PARC project. In TEF-T, a 250 kW proton-beam-driven LBE (Lead-Bismuth Eutectic) spallation target will be installed to prepare an irradiation database for candidate ADS structural materials. Design activities of the LBE target and target trolley have been progressed. Conceptual design of hot-cells for LBE target loop maintenance and PIE (Post Irradiation Examination) of irradiated samples have been finished. Two LBE loops were manufactured. One is a loop for TEF-T target mock-up and the other is that for collection of material corrosion characteristics in flowing LBE. Oxygen potential control systems for LBE flow have been also developed. Remote handling tests for the target exchange are underway. In this paper, current activities and studies to realize TEF-T will be presented.
Endo, Naruki*; Saito, Hiroyuki; Machida, Akihiko; Katayama, Yoshinori
Journal of Alloys and Compounds, 645(Suppl.1), p.S61 - S63, 2015/10
Times Cited Count:0 Percentile:0.01(Chemistry, Physical)Ito, Shinichi*; Yokoo, Tetsuya*; Masuda, Takatsugu*; Yoshizawa, Hideki*; Soda, Minoru*; Ikeda, Yoichi*; Ibuka, Soshi*; Kawana, Daichi*; Sato, Taku*; Nambu, Yusuke*; et al.
JPS Conference Proceedings (Internet), 8, p.034001_1 - 034001_6, 2015/09
Sato, Isamu; Tanaka, Kosuke; Koyama, Shinichi; Matsushima, Kenichi*; Matsunaga, Junji*; Hirai, Mutsumi*; Endo, Hiroshi*; Haga, Kazuo*
Energy Procedia, 82, p.86 - 91, 2015/07
Times Cited Count:2 Percentile:17.57(Nuclear Science & Technology)Experiments simulating overheating conditions of fast reactor severe accidents have been previously carried out with irradiated fuels. For the present study, the chemical forms of the fission products (FPs) included in the irradiated fuels were evaluated by thermochemical equilibrium calculations. At temperatures of 2773 K and 2973 K, the most stable forms of Cs, I, Te, Sb, Pd and Ag are gaseous compounds. Cs and Sb detected in the thermal gradient tube (TGT) in the experiments can take gaseous chemical forms of elemental Cs, CsI, CsMoO, CsO and elemental Sb, SbO, SbTe, respectively. By comparing experimental results and the estimations, it is seen CsI thermochemically behaves in a manner that traps it in the TGT, while elemental Cs trends to move as fine particles. The moving behavior of the gaseous FPs will obey not only thermochemical principles, but also those of particle dynamics.
Endo, Naruki*; Saita, Itoko*; Nakamura, Yumiko*; Saito, Hiroyuki; Machida, Akihiko
International Journal of Hydrogen Energy, 40(8), p.3283 - 3287, 2015/03
Times Cited Count:16 Percentile:39.98(Chemistry, Physical)Kajimoto, Tsuyoshi*; Hashiguchi, Taro*; Shigyo, Nobuhiro*; Satoh, Daiki; Uozumi, Yusuke*; Song, T. Y.*; Lee, C. W.*; Kim, J. W.*; Yang, S. C.*; Koba, Yusuke*; et al.
JAEA-Conf 2014-002, p.127 - 132, 2015/02
Particle transport Monte Carlo codes such as PHITS, FLUKA and so on are used for radiation safety design of high energy accelerators. The validity of code is confirmed by comparison with many experimental data. In this study, we report proton, deuteron, and triton production double differential cross sections (DDXs) from a graphite target by 290 MeV/nucleon Ar ions. The measured spectra are compared with those calculated by PHITS and FLUKA codes.
Takeuchi, Tomoaki; Otsuka, Noriaki; Shibata, Hiroshi; Nagata, Hiroshi; Endo, Yasuichi; Matsui, Yoshinori; Tsuchiya, Kunihiko
KAERI/GP-418/2015, p.110 - 112, 2015/00
irradiation experiments with a Co source were carried out for developing Self-Powered Gamma Detectors (SPGDs) with lead (Pb) emitter and Self-Powered Neutron Detectors (SPNDs) with Pt-40%Rh emitter prior to in-core irradiation experiments. The results showed the output currents of the SPGDs were proportional to the dose rate in the range from about 200-6000 Gy/h with about 10% accuracy. In the case of SPNDs, the output currents flowed in inverse direction and were an order of magnitude lower compared with that of the SPGDs. These different behaviors of the output currents are considered to be caused by the difference in the emitter sizes and the current component originated at the MI cables.
Machida, Akihiko; Saito, Hiroyuki; Sugimoto, Hidehiko*; Hattori, Takanori; Sano, Asami; Endo, Naruki*; Katayama, Yoshinori; Iizuka, Riko*; Sato, Toyoto*; Matsuo, Motoaki*; et al.
Nature Communications (Internet), 5, p.5063_1 - 5063_6, 2014/09
Times Cited Count:55 Percentile:86.02(Multidisciplinary Sciences)Iron hydride FeH, is thermodynamically stable only at high hydrogen pressure of several GPa. To investigate the hydrogenation process and hydrogen state in iron hydride, it is necessary to carry out the in-situ measurement under high pressure and high temperature. In this study, we performed the in-situ neutron diffraction measurement of Fe-D system using the high pressure neutron diffractometer PLANET in the MLF, J-PARC, and determined the deuterium occupying sites and occupancies in fcc-FeD. We found the minor occupation of tetrahedral sites under high pressure and high temperature. We considered the mechanism of the minor occupation based on the Quantum-mechanical calculation.
Saito, Hiroyuki; Takagi, Shigeyuki*; Matsuo, Motoaki*; Iijima, Yuki*; Endo, Naruki*; Aoki, Katsutoshi*; Orimo, Shinichi*
APL Materials (Internet), 2(7), p.076103_1 - 076103_7, 2014/07
Times Cited Count:25 Percentile:70.44(Nanoscience & Nanotechnology)Toyooka, Junichi; Endo, Hiroshi*; Tobita, Yoshiharu; Takahashi, Minoru*
Nihon Genshiryoku Gakkai Wabun Rombunshi, 13(2), p.35 - 50, 2014/05
In the design of future sodium-cooled fast reactor, a design measure to prevent severe re-criticality events even in case of core disruptive accidents is considered. This design adopts inner duct within the fuel sub-assembly that should allow molten fuel ejection out of the core region. The effectiveness of this design is dependent on failure time of the duct and it depends significantly on heat transfer from the melting core materials to the duct. In the previous study by the authors, heat transfer from molten fuel/steel mixture to the inner duct was evaluated with a computer model simulation for an in-pile experiment performed in IGR (Impulse Graphite Reactor) focusing on demonstration of the design effectiveness. In the present study, possible uncertainties in the assumption and model parameters in the previous study were evaluated so that validity of the main conclusion of the previous study could be confirmed and re-enforced. This confirmation consisted of evaluation of necessary fuel-to-steel heat transfer area, effect of hydrodynamic fragmentation of steel droplets, steel-vapor condensation heat transfer onto the duct surface and fuel crust formation. Furthermore, possible effect of variation in fuel designs and transient scenarios to the heat transfer was evaluated changing steel volume fraction as the initial boundary conditions. It was concluded that the previous study was appropriate in representing the realistic situation and the conclusions in the previous study were enforced. An additional set of analysis showed that possible under-estimation of heat transfer from fuel/steel mixture to the duct could be enhanced with a condition where steel volume fraction is less. Future model improvement is preferable for this characteristic.
Endo, Naruki; Saito, Hiroyuki; Machida, Akihiko; Katayama, Yoshinori
Materia, 53(3), p.94 - 99, 2014/03
no abstracts in English
Saito, Hiroyuki; Takagi, Shigeyuki*; Endo, Naruki; Machida, Akihiko; Aoki, Katsutoshi; Orimo, Shinichi*; Katayama, Yoshinori
APL Materials (Internet), 1(3), p.032113_1 - 032113_7, 2013/09
Times Cited Count:15 Percentile:54.06(Nanoscience & Nanotechnology)Endo, Naruki; Saito, Hiroyuki; Machida, Akihiko; Katayama, Yoshinori
International Journal of Hydrogen Energy, 38(16), p.6726 - 6729, 2013/05
Times Cited Count:22 Percentile:50.45(Chemistry, Physical)Yoshii, Kenji; Mizumaki, Masaichiro*; Matsumoto, Keisuke*; Mori, Shigeo*; Endo, Naruki; Saito, Hiroyuki; Matsumura, Daiju; Kambe, Takashi*; Ikeda, Naoshi*
Journal of Physics; Conference Series, 428, p.012032_1 - 012032_5, 2013/04
Times Cited Count:14 Percentile:96.93(Chemistry, Applied)We have investigated a single crystal of multiferroic YbFeO. Its magnetic transition temperature was 250 K. The magnetization along the c-axis was much larger than that within the ab plane, indicating the Ising character of this system. The field-cooled magnetization became negative below 10 K. This was explained in terms of an antiparallel coupling between Yb and Fe moments. Magnetocaloric effects were also observed. The change of entropy was found to show a broad peak with a width of 100 K, which is favorable to application.
Sato, Ryutaro*; Saito, Hiroyuki; Endo, Naruki; Takagi, Shigeyuki*; Matsuo, Motoaki*; Aoki, Katsutoshi; Orimo, Shinichi*
Applied Physics Letters, 102(9), p.091901_1 - 091901_4, 2013/03
Times Cited Count:29 Percentile:73.44(Physics, Applied)Toyooka, Junichi; Endo, Hiroshi*; Tobita, Yoshiharu; Ninokata, Hisashi*
Nihon Genshiryoku Gakkai Wabun Rombunshi, 12(1), p.50 - 66, 2013/03
In the design of JSFR (Japan Sodium-cooled Fast Reactor), a design measure (FAIDUS: Fuel sub-Assembly with an Inner DUct Structure) is considered to prevent severe re-criticality events even in case of core disruptive accidents by molten fuel ejection out of the core region through the duct equipped within the fuel subassembly. Confirming principle effectiveness of such design measure is important. In this study, systematic heat transfer behavior of the ID1 test, which was conducted in IGR (Impulse Graphite Reactor) in Republic of Kazakhstan, was evaluated applying a heat conduction code TAC2D and a reactor safety analysis code SIMMER-III focusing on the clarification of heat transfer from high-temperature mixture of molten fuel and steel to the duct. As a result, the duct failure by high heat flux from the mixture was identified as one of an important mechanism of early duct failure in FAIDUS. It was also suggested from this study that the high heat flux from the mixture is caused by the direct contact of molten steel without the presence of fuel crust on the duct wall. Based on these findings, it is judged that the mechanism of early duct failure with high heat flux obtained in the ID1 test satisfies the required condition to FAIDUS, i.e., the inner duct of FAIDUS should fail at an early phase of core disruptive accident in advance to wrapper tube failure so that produced molten fuel can escape from the core region, and it supports feasibility of the FAIDUS concept.
Takagi, Shigeyuki*; Saito, Hiroyuki; Endo, Naruki; Sato, Ryutaro*; Ikeshoji, Tamio*; Matsuo, Motoaki*; Miwa, Kazutoshi*; Aoki, Katsutoshi; Orimo, Shinichi*
Physical Review B, 87(12), p.125134_1 - 125134_6, 2013/03
Times Cited Count:14 Percentile:53.53(Materials Science, Multidisciplinary)