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Journal Articles

Experimental visualization of water/ice phase distribution at cold start for practical-sized polymer electrolyte fuel cells

Higuchi, Yuki*; Yoshimune, Wataru*; Kato, Satoru*; Hibi, Shogo*; Setoyama, Daigo*; Isegawa, Kazuhisa*; Matsumoto, Yoshihiro*; Hayashida, Hirotoshi*; Nozaki, Hiroshi*; Harada, Masashi*; et al.

Communications Engineering (Internet), 3, p.33_1 - 33_7, 2024/02

Journal Articles

Reversible structure change in graphene/metal interface by intercalation and deintercalation

Fukaya, Yuki; Entani, Shiro*; Sakai, Seiji*

Physical Review B, 108(15), p.155422_1 - 155422_6, 2023/10

no abstracts in English

JAEA Reports

Structural investigation of borosilicate glasses by using XAFS measurement in soft X-ray region, 3 (Joint research)

Nagai, Takayuki; Okamoto, Yoshihiro; Yamagishi, Hirona*; Shibata, Daisuke*; Kojima, Kazuo*; Hasegawa, Takehiko*; Sato, Seiichi*; Fukaya, Akane*; Hatakeyama, Kiyoshi*

JAEA-Research 2023-004, 45 Pages, 2023/09

JAEA-Research-2023-004.pdf:6.07MB

The local structure of glass-forming elements and waste elements in borosilicate glasses varies with its chemical composition. In this study, simulated waste glass samples were prepared and the chemical state regarding boron (B), silicon (Si) and waste elements of iron (Fe), cesium (Cs) were estimated by using XAFS measurement in soft X-ray region. To understand the chemical stability of simulated waste glasses, XANES spectra of B K-edge, Fe L$$_{3}$$, L$$_{2}$$-edge, and Cs M$$_{5}$$, M$$_{4}$$-edge were measured on the glass surface exposed to the leachate. As a result, it was found that the glass surface exposed to the leachate was changed and it was difficult to obtain a clear XANES spectrum. From the B K-edge XANES spectra on glass surfaces exposed to the leachate, an increase in three-coordination of B-O (BO$$_{3}$$) and a decrease in four-coordination of B-O (BO$$_{4}$$) were observed compared to the glass surfaces before immersion. The XANES spectra of Fe L$$_{3}$$, L$$_{2}$$-edge, and Cs M$$_{5}$$, M$$_{4}$$-edge show that as the exposure time in the leachate increases, the Cs present on the glass surface dissolves into the leachate. The XANES spectra of Si K-edge were measured on simulated waste glass surfaces before immersion, and it was confirmed that the change in XANES spectra given by Na$$_{2}$$O concentration had a larger effect than the waste component concentration.

Journal Articles

Reactor physics experiment on a graphite-moderated core to construct integral experiment database for HTGR

Okita, Shoichiro; Fukaya, Yuji; Sakon, Atsushi*; Sano, Tadafumi*; Takahashi, Yoshiyuki*; Unesaki, Hironobu*

Nuclear Science and Engineering, 197(8), p.2251 - 2257, 2023/08

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

Journal Articles

Finding RHEED conditions sensitive to hydrogen position on Pd(100)

Kawamura, Takaaki*; Fukaya, Yuki; Fukutani, Katsuyuki

Surface Science, 722, p.122098_1 - 122098_8, 2022/08

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

no abstracts in English

Journal Articles

Reactor physics experiment in a graphite moderation system for HTGR, 3

Fukaya, Yuji; Okita, Shoichiro; Kanda, Shun*; Goto, Masaki*; Nakajima, Kunihiro*; Sakon, Atsushi*; Sano, Tadafumi*; Hashimoto, Kengo*; Takahashi, Yoshiyuki*; Unesaki, Hironobu*

KURNS Progress Report 2021, P. 101, 2022/07

The Japan Atomic Energy Agency (JAEA) started the Research and Development (R&D) to improve nuclear prediction techniques for High Temperature Gas-cooled Reactors (HTGRs) in 2018. The objectives are to intro-duce the generalized bias factor method to avoid full mock-up experiment for the first commercial HTGR and to improve neutron instrumentation system by virtue of the particular characteristics due to a graphite moderation system. For this end, we composed B7/4"G2/8"p8EU(3)+3/8"p38EU in the B-rack of Kyoto University Critical Assembly (KUCA) in 2021.

Journal Articles

Reactor noise power-spectral analysis for a graphite-moderated and -reflected core, 3

Sakon, Atsushi*; Hashimoto, Kengo*; Sano, Tadafumi*; Nakajima, Kunihiro*; Kanda, Shun*; Goto, Masaki*; Fukaya, Yuji; Okita, Shoichiro; Fujimoto, Nozomu*; Takahashi, Yoshiyuki*

KURNS Progress Report 2021, P. 100, 2022/07

The R&D of reactor noise analysis to obtain HTGR nuclear characteristics have been performed with Kyoto University Critical Assembly (KUCA). In the last study, a neutron detector located about 55 cm away of fuel assembly measured the auto power spectral density. However, the prompt neutron decay constants obtained by this detector was different from that of other detectors. The objective of this study is experimental study of reactor noise analysis by the power spectrum method using neutron detector placed outside reactor core.

Journal Articles

Re-evaluation of electricity generation cost of HTGR

Fukaya, Yuji; Ohashi, Hirofumi; Sato, Hiroyuki; Goto, Minoru; Kunitomi, Kazuhiko

Nihon Genshiryoku Gakkai Wabun Rombunshi (Internet), 21(2), p.116 - 126, 2022/06

An improvement electricity generation cost evaluation method for High Temperature Gas-cooled Reactors (HTGRs) has been performed. Japan Atomic Energy Agency (JAEA) had completed the commercial HTGR concept named Gas Turbine High Temperature Reactor (GTHTR300) and the electricity generation cost evaluation method approximately a decade ago. The cost evaluation was developed based on the method of Federation of Electric Power Companies (FEPC). The FEPC method was drastically revised after the Fukushima Daiichi nuclear disaster. Moreover, the escalation of material and labor cost for the decade should be consider to evaluate the latest cost. Therefore, we revised the cost evaluation method for GTHTR300 and the cost was compared with that of Light Water Reactor (LWR). As a result, it was found that the electricity generation cost of HTGR of 7.9 yen/kWh is cheaper than that of LWR of 11.7 yen/kWh by approximately 30% at the capacity factor of 70%.

Journal Articles

Preliminary experiment in a graphite-moderated core to avoid full mock-up experiment for the future first commercial HTGR

Okita, Shoichiro; Fukaya, Yuji; Sakon, Atsushi*; Sano, Tadafumi*; Takahashi, Yoshiyuki*; Unesaki, Hironobu*

Proceedings of International Conference on Physics of Reactors 2022 (PHYSOR 2022) (Internet), 9 Pages, 2022/05

Journal Articles

Environmental effects on layer-dependent dynamics of Dirac fermions in quasicrystalline bilayer graphene

Zhao, Y.*; Suzuki, T.*; Iimori, T.*; Kim, H.-W.*; Ahn, J. R.*; Horio, Masafumi*; Sato, Yusuke*; Fukaya, Yuki; Kanai, T.*; Okazaki, K.*; et al.

Physical Review B, 105(11), p.115304_1 - 115304_8, 2022/03

 Times Cited Count:1 Percentile:18.86(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Activity report of the Task Group on Parameters Used in Biospheric Dose Assessment Models for Radioactive Waste Disposal

Takahashi, Tomoyuki*; Fukaya, Yukiko*; Iimoto, Takeshi*; Uni, Yasuo*; Kato, Tomoko; Sun, S.*; Takeda, Seiji; Nakai, Kunihiro*; Nakabayashi, Ryo*; Uchida, Shigeo*; et al.

Hoken Butsuri (Internet), 56(4), p.288 - 305, 2021/12

We report the results of activities related to the Task Group of Parameters Used in Biospheric Dose Assessment Models for Radioactive Waste Disposal at the Japan Health Physics Society.

Journal Articles

Atomic arrangements of quasicrystal bilayer graphene; Interlayer distance expansion

Fukaya, Yuki; Zhao, Y.*; Kim, H.-W.*; Ahn, J.-R.*; Fukidome, Hirokazu*; Matsuda, Iwao*

Physical Review B, 104(18), p.L180202_1 - L180202_5, 2021/11

 Times Cited Count:5 Percentile:63.47(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Summary results of subsidy program for the "Project of Decommissioning and Contaminated Water Management (Development of Analysis and Estimation Technology for Characterization of Fuel Debris (Development of Technologies for Enhanced Analysis Accuracy and Thermal Behavior Estimation of Fuel Debris))"

Koyama, Shinichi; Nakagiri, Toshio; Osaka, Masahiko; Yoshida, Hiroyuki; Kurata, Masaki; Ikeuchi, Hirotomo; Maeda, Koji; Sasaki, Shinji; Onishi, Takashi; Takano, Masahide; et al.

Hairo, Osensui Taisaku jigyo jimukyoku Homu Peji (Internet), 144 Pages, 2021/08

JAEA performed the subsidy program for the "Project of Decommissioning and Contaminated Water Management (Development of Analysis and Estimation Technology for Characterization of Fuel Debris (Development of Technologies for Enhanced Analysis Accuracy and Thermal Behavior Estimation of Fuel Debris))" in 2020JFY. This presentation summarized briefly the results of the project, which will be available shortly on the website of Management Office for the Project of Decommissioning and Contaminated Water Management.

Journal Articles

High temperature gas-cooled reactors

Takeda, Tetsuaki*; Inagaki, Yoshiyuki; Aihara, Jun; Aoki, Takeshi; Fujiwara, Yusuke; Fukaya, Yuji; Goto, Minoru; Ho, H. Q.; Iigaki, Kazuhiko; Imai, Yoshiyuki; et al.

High Temperature Gas-Cooled Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.5, 464 Pages, 2021/02

As a general overview of the research and development of a High Temperature Gas-cooled Reactor (HTGR) in JAEA, this book describes the achievements by the High Temperature Engineering Test Reactor (HTTR) on the designs, key component technologies such as fuel, reactor internals, high temperature components, etc., and operational experience such as rise-to-power tests, high temperature operation at 950$$^{circ}$$C, safety demonstration tests, etc. In addition, based on the knowledge of the HTTR, the development of designs and component technologies such as high performance fuel, helium gas turbine and hydrogen production by IS process for commercial HTGRs are described. These results are very useful for the future development of HTGRs. This book is published as one of a series of technical books on fossil fuel and nuclear energy systems by the Power Energy Systems Division of the Japan Society of Mechanical Engineers.

Journal Articles

Emergence of nearly flat bands through a kagome lattice embedded in an epitaxial two-dimensional Ge layer with a bitriangular structure

Fleurence, A.*; Lee, C.-C.*; Friedlein, R.*; Fukaya, Yuki; Yoshimoto, Shinya*; Mukai, Kozo*; Yamane, Hiroyuki*; Kosugi, Nobuhiro*; Yoshinobu, Jun*; Ozaki, Taisuke*; et al.

Physical Review B, 102(20), p.201102_1 - 201102_6, 2020/11

 Times Cited Count:2 Percentile:13.29(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Effect of water vapor on re-saturation process in EBS performance of re-saturation process by Thermo-Hydro-Mechanical coupled analysis

Sato, Shin*; Ono, Hirokazu; Tanai, Kenji; Yamamoto, Shuichi*; Fukaya, Masaaki*; Shimura, Tomoyuki*; Niunoya, Sumio*

Jiban Kogaku Janaru (Internet), 15(3), p.529 - 541, 2020/09

no abstracts in English

Journal Articles

Electronic structure of a (3$$times$$3)-ordered silicon layer on Al(111)

Sato, Yusuke*; Fukaya, Yuki; Cameau, M.*; Kundu, A. K.*; Shiga, Daisuke*; Yukawa, Ryu*; Horiba, Koji*; Chen, C.-H.*; Huang, A.*; Jeng, H.-T.*; et al.

Physical Review Materials (Internet), 4(6), p.064005_1 - 064005_6, 2020/06

 Times Cited Count:6 Percentile:31.82(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Structure of superconducting Ca-intercalated bilayer Graphene/SiC studied using total-reflection high-energy positron diffraction

Endo, Yukihiro*; Fukaya, Yuki; Mochizuki, Izumi*; Takayama, Akari*; Hyodo, Toshio*; Hasegawa, Shuji*

Carbon, 157, p.857 - 862, 2020/02

 Times Cited Count:19 Percentile:72.99(Chemistry, Physical)

no abstracts in English

Journal Articles

Study on plutonium burner high temperature gas-cooled reactor in Japan; Introduction scenario, reactor safety and fabrication tests of the 3S-TRISO fuel

Ueta, Shohei; Mizuta, Naoki; Fukaya, Yuji; Goto, Minoru; Tachibana, Yukio; Honda, Masaki*; Saiki, Yohei*; Takahashi, Masashi*; Ohira, Koichi*; Nakano, Masaaki*; et al.

Nuclear Engineering and Design, 357, p.110419_1 - 110419_10, 2020/02

 Times Cited Count:1 Percentile:12.47(Nuclear Science & Technology)

The concept of a plutonium (Pu) burner HTGR is proposed to incarnate highly-effective Pu utilization by its inherent safety features. The security and safety fuel (3S-TRISO fuel) employs the coated fuel particle with a fuel kernel made of plutonium dioxide (PuO$$_{2}$$) and yttria stabilized zirconia (YSZ) as an inert matrix. This paper presents feasibility study of Pu burner HTGR and R&D on the 3S-TRISO fuel.

Journal Articles

Total-reflection high-energy positron diffraction (TRHEPD)

Fukaya, Yuki

Yodenshi Kagaku, (13), p.3 - 10, 2019/09

no abstracts in English

421 (Records 1-20 displayed on this page)