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C-stainless steel composites using the improved MPS methodAhmed, Z.*; Wu, S.*; Sharma, A.*; Kumar, R.*; Yamano, Hidemasa; Pellegrini, M.*; Yokoyama, Ryo*; Okamoto, Koji*
International Journal of Heat and Mass Transfer, 250, p.127343_1 - 127343_17, 2025/11
Times Cited Count：2 Percentile：69.40(Thermodynamics)Ishida, Tsuyoshi; Nakashima, Shinichi; Kondo, Shinji; Hayashibara, Kenichi; Yamada, Shigeki*; Okamoto, Ryo*; Nakamura, Hironobu
Dai-44-Kai Nihon Kaku Busshitsu Kanri Gakkai Nenji Taikai Kaigi Rombunshu (Internet), 4 Pages, 2023/11
no abstracts in English
Tamii, Atsushi*; Pellegri, L.*; S
derstrm, P.-A.*; Allard, D.*; Goriely, S.*; Inakura, Tsunenori*; Khan, E.*; Kido, Eiji*; Kimura, Masaaki*; Litvinova, E.*; et al.
European Physical Journal A, 59(9), p.208_1 - 208_21, 2023/09
Times Cited Count：10 Percentile：87.89(Physics, Nuclear)no abstracts in English
and CrUOAkiyama, Daisuke*; Kusaka, Ryoji; Kumagai, Yuta; Nakada, Masami; Watanabe, Masayuki; Okamoto, Yoshihiro; Nagai, Takayuki; Sato, Nobuaki*; Kirishima, Akira*
Journal of Nuclear Materials, 568, p.153847_1 - 153847_10, 2022/09
Times Cited Count：6 Percentile：62.93(Materials Science, Multidisciplinary)FeUO, CrUO, and Fe
Cr
UO are monouranates containing pentavalent U. Even though these compounds have similar crystal structures, their formation conditions and thermal stability are significantly different. To determine the factors causing the difference in thermal stability between FeUO and CrUO, their crystal structures were evaluated in detail. A Raman band was observed at 700 cm
in all the samples. This Raman band was derived from the stretching vibration of the O-U-O axis band, indicating that FeCrUO was composed of a uranyl-like structure in its lattice regardless of its "x"' value. Mssbauer measurements indicated that the Fe in FeUO and FeCrUO were trivalent. Furthermore, FeCrUO lost its symmetry around Fe
with increasing electron densities around Fe, as the abundance of Cr increased. These results suggested no significant structural differences between FeUO and CrUO. Thermogravimetric measurements for UO
, FeUO, and CrUO showed that the temperature at which FeUO decomposed under an oxidizing condition (approximately 800 
C) was significantly lower than the temperature at which the decomposition of CrUO started (approximately 1250 C). Based on these results, we concluded that the decomposition of FeUO was triggered by an "in-crystal" redox reaction, i.e., Fe 
U
Fe
U
, which would not occur in the CrUO lattice because Cr could never be reduced under the investigated condition. Finally, the existence of Cr in FexCrUO effectively suppressed the decomposition of the FeCrUO crystal, even at a very low Cr content.
Umeda, Takahide*; Okamoto, Mitsuo*; Arai, Ryo*; Sato, Yoshihiro*; Kosugi, Ryoji*; Harada, Shinsuke*; Okumura, Hajime*; Makino, Takahiro; Oshima, Takeshi
Materials Science Forum, 778-780, p.414 - 417, 2014/02
Times Cited Count：2 Percentile：69.44(Crystallography)Interface defects of Metal-Oxide-Semiconductors (MOSFETs) fabricated on Carbone (C) face 4H-SiC were investigated by Electrically Detected Magnet Resistance (EDMR). Gate oxide of the MOSFETs was formed by either wet-oxidation and H annealing or dry-oxidation. The values of channel mobility for MOSFETS with wet gate oxide and dry gate oxide are less than 1 and 90 cm
/Vs, respectively. By EDMR measurement under low temperature (less than 20 K), EDMR signals related to C were detected. The peak height of the signals increased with increasing 
-ray doses, and the channel mobility decreased. From this result, it is assumed that hydrogen atoms passivating C dangling bonds are released by -rays and the channel mobility decreases with increasing the C related defects.
Wakui, Takashi; Kogawa, Hiroyuki; Haga, Katsuhiro; Futakawa, Masatoshi; Hayashi, Ryoichi*; Uchiyama, Naoyoshi*; Okamoto, Yoshinao*; Nakamura, Koji*
JAEA-Technology 2009-040, 96 Pages, 2010/03
JAEA-Technology-2009-040.pdf:35.52MB
The construction of materials and life science experimental facility in J-PARC project had been completed. The mercury target vessel consists of triple-walled structure in order to prevent the leak of mercury to outside at the failure of the mercury vessel and to remove the heat of the safety hull, which covers the mercury vessel, due to the injection of the pulsed proton beams. The high fabrication accuracy is required for the mercury target vessel assembled by the welding. In this report, the required specification and basic structure of parts in the mercury target vessel are described and the fabrication procedure of the mercury target vessel by the vender is reported. In the fabrication of the mercury target vessel, there were many troubles such as large deformation due to the welding and then the vender repaired and brought the mercury target vessel to completion. Furthermore, improvements for the design and fabrication of the mercury target are reported.
Tamada, Taro; Honjo, Eijiro; Maeda, Yoshitake*; Okamoto, Tomoyuki*; Ishibashi, Matsujiro*; Tokunaga, Masao*; Kuroki, Ryota
Proceedings of the National Academy of Sciences of the United States of America, 103(9), p.3135 - 3140, 2006/02
Times Cited Count：100 Percentile：84.86(Multidisciplinary Sciences)A crystal structure of the signaling complex between human granulocyte colony-stimulating factor (GCSF), and a ligand binding region of GCSF receptor (GCSF-R), has been determined to 2.8
resolution. The GCSF:GCSF-R complex formed a 2:2 stoichiometry via a cross-over interaction between the Ig-like domains of GCSF-R and GCSF. The conformation of the complex is quite different to that between human GCSF and the CRH domain of mouse GCSF-R, but similar to that of the interleukin-6 (IL-6)/gp130 signaling complex. The Ig-like domain cross-over structure necessary for GCSF-R activation is consistent with previously reported thermodynamic and mutational analyses.
Honjo, Eijiro; Tamada, Taro; Maeda, Yoshitake*; Koshiba, Takumi*; Matsukura, Yasuko*; Okamoto, Tomoyuki*; Ishibashi, Matsujiro*; Tokunaga, Masao*; Kuroki, Ryota
Acta Crystallographica Section F, 61(8), p.788 - 790, 2005/08
Times Cited Count：7 Percentile：54.49(Biochemical Research Methods)Granulocyte colony-stimulating factor (GCSF) receptor receives signals for regulating the proliferation and differentiation of the precursor cells of granulocytes. The complex composed of two GCSFs and two GCSF receptors was crystallized. The crystal of the complex was grown in 1.0 M sodium formate and 0.1 M sodium acetate (pH4.6). It belongs to the space group 
4
22 (or its enantiomorph 4
22) with unit cell dimensions of 
= 
= 110.1 , 
= 331.8 . However, the diffraction data from the crystal beyond 5 resolution could not be collected. Since the heterogeneity of GCSF receptor seems to interrupt growth of good quality crystals, the GCSF receptor was fractionated by achromatography. Crystals of GCSF/fractionated GCSF receptor complex were grown as a new crystal form in 0.2 M ammonium phosphate. The new crystal diffracts beyond 3.0 resolution and belongs to space group 321 (or its enantiomorph 321) with unit-cell parameters = = 134.8, = 105.7 .
Okamoto, Kaoru; Miyakawa, Shunichi; Mitsugi, Takeshi; Kitamura, Ryoichi
JNC TN9410 99-010, 350 Pages, 1999/06
In the needs of the fuel irradiation test in "Joyo" MK-III core, there have been required that the irradiation of high performance fuel at high liner heat rate to high burn-up range, or the irradiation of advanced fuel such as MA fuel and Vipac fuel. In order to carry out these irradiation tests, newly designed irradiation subassembly is required with special features of; (1)Capability of the re-assembling after post-irradiation examination, even if the number of fuel in the identical irradiation condition decreases because of intermediate inspection. (2)Enhanced flexibility of the irradiation temperature setting ( in the present, UNIS-B's has 6 cases on the maximum). (3)Sufficient flexibility for the coolant flow distribution in the subassembly by extending variety of the flow rate setting. UNIS-D is a fuel irradiation subassembly which has been developed from above viewpoints. It is a compartment loading type irradiation subassembly that is able to load maximum of 18 compartments. Two types of compartments -type and 
-typc arc prepared for UNIS-D. Thc sufficient consideration has also been made on the rc-assembling. A -type is the same compartment as the existing UNIS-B's and a -type is the newly designed one for UNIS-D. Three to five fuel pins are loaded into a -type compartment and only one pin is loadcd into a -type compartment. It is possible to carry out the irradiation test in a maximum of 18 test temperature conditions within a subassembly, since it has the sufficient flexibility for the coolant flow distribution. As for the development of UNIS-D, we have finished the detailed structure design and the design verification by the water flow examination, which confirmed that the UNIS-D exceeded its required performances in use and that its structure design was satisfactory.
Koga, Yuki*; Matsuura, Hideaki*; Okamoto, Ryo*; Ida, Yuma*; Katayama, Kazunari*; Otsuka, Teppei*; Goto, Minoru; Nakagawa, Shigeaki; Ishitsuka, Etsuo; Nagasumi, Satoru; et al.
no journal, ,
Large quantity of tritium is demanded for starting up of fusion reactor and engineering test using tritium for fusion blanket system. Tritium production, by 
Li(n, 
)T reaction using the high temperature gas-cooled reactor (HTGR), has been proposed and the method to produce tritium by loading the lithium rods as burnable poison in the reactor core has been studied. In this presentation, the design of lithium rods to be loaded to High Temperature engineering Test Reactor (HTTR) and its irradiation test plan to demonstrate tritium production are presented.
Okamoto, Ryo*; Matsuura, Hideaki*; Ida, Yuma*; Koga, Yuki*; Katayama, Kazunari*; Otsuka, Teppei*; Goto, Minoru; Nakagawa, Shigeaki; Ishitsuka, Etsuo; Nagasumi, Satoru
no journal, ,
A study on tritium production using a high-temperature gas-cooled reactor has been carried out and it was proposed that zirconium is loaded into the lithium irradiation capsule to confine tritium within the irradiation capsule under high temperature condition. In this study, zirconium loading method was examined by numerical calculations to improve the tritium confinement. As a result, it was found that improvement in the tritium confinement can be expected by loading spherical zirconium into the irradiation capsule.
Suganuma, Takuro*; Matsuura, Hideaki*; Okamoto, Ryo*; Koga, Yuki*; Katayama, Kazunari*; Otsuka, Teppei*; Goto, Minoru; Nakagawa, Shigeaki; Tobita, Kenji*
no journal, ,
A study on the confinement of tritium, which is a fuel for fusion reactors and is produced by a HTGR, has been conducted for high temperature condition. The tritium is confined in the irradiation capsule with a zirconium layer. The relation between a H/Zr ratio and an apparent diffusion coefficient of tritium in the zirconium layer is needed to evaluate the tritium confinement performance of the irradiation capsule. This relation was examined with a experiment using deuteron. As a result, the apparent diffusion coefficient deceases with an increase of the H/Zr ratio. This phenomena should be caused by a generation of hydrogen. After that, the analysis for an amount of the release of the tritium from the irradiation capsule will be calculated using obtained data to evaluate the containment performance of the irradiation capsule.
Koga, Yuki*; Matsuura, Hideaki*; Okamoto, Ryo*; Suganuma, Takuro*; Katayama, Kazunari*; Otsuka, Teppei*; Goto, Minoru; Nakagawa, Shigeaki; Ishitsuka, Etsuo; Tobita, Kenji*
no journal, ,
Production of tritium using a high temperature gas-cooled reactor (HTGR) has been studied for a prior engineering test with tritium handling and for the startup operation of a demonstration fusion reactor. For this purpose, Li-loading rods are installed at the moderator region of the HTGR. The tritium retention capability of Li-loading rod would decline due to high temperature condition from 1100K to 1200K during HTGR rated power operation. Therefore, the zirconium is employed as tritium absorber which is granular and is coated with nickel to prevent from declining the tritium absorption capability due to zirconium oxidation and so on. In this presentation, the design concept of Li-loading rods with granular zirconium coated with nickel and the method of irradiation test by using the HTTR which is a test reactor of HTGR are presented.
Okamoto, Ryo; Tachibana, Yukio
no journal, ,
Japan aims to achieve carbon neutrality by 2050, with hydrogen utilization as a key measure. The requirements for hydrogen supply in a hydrogen society include domestic hydrogen production, large-scale and stable production, and being carbon-free. High-temperature gas reactors have been selected as one of five reactor types to be developed under the government's Green Transformation policy, with basic design starting in 2023 and operation targeted for the late 2030s. While there are challenges related to policy, society, and technology in the practical use of high-temperature gas reactors, we aim to resolve these through domestic demonstration projects and thermal utilization tests using HTTR. HTTR is the world's only block-type high-temperature gas reactor in operation, achieving a reactor outlet temperature of 950 degree, the highest globally, and has a record of safety validation tests. In these tests, we simulated the failure of control rod insertion and tripping helium gas circulation system, demonstrating that the reactor stabilizes due to physical phenomena even in accidents, proving the inherent safety of high-temperature gas reactors. We plan to connect a hydrogen production plant to HTTR, producing hydrogen using secondary system heat. The schedule includes submitting application for licensing within the 2024 fiscal year and starting hydrogen production tests in 2028. There are several candidates for hydrogen production methods, including methane steam reforming, high-temperature steam electrolysis, methane pyrolysis, and the IS process, and we will select the appropriate method for carbon-free hydrogen production using high-temperature gas reactors.
Tanida, Hajime; Endo, Ryo*; Akiyama, Daisuke*; Okamoto, Yoshihiro; Kirishima, Akira*
no journal, ,
no abstracts in English
Tanida, Hajime; Endo, Ryo*; Akiyama, Daisuke*; Okamoto, Yoshihiro; Kirishima, Akira*
no journal, ,
no abstracts in English
Tamada, Taro; Honjo, Eijiro; Maeda, Yoshitake*; Okamoto, Tomoyuki*; Ishibashi, Matsujiro*; Tokunaga, Masao*; Kuroki, Ryota
no journal, ,
We have succeeded in crystallization of 2:2 complex between human granulocyte colony-stimulating factor (hGCSF) and the Ig-like and CRH domains of human GCSF-R (hGCSF-R) and determined its tertiary structure by X-ray crystallography at 2.8 resolution. The signaling 2:2 complex is formed via cross-over interactions between the Ig-like domain of hGCSF-R and the neighboring hGCSF, forming a two-fold axis of crystallographic symmetry. This conformation is quite different from that of the heterogeneous mGCSF-R complex, and more closely resembles the 2:2:2 active assembly of human interleukin-6 (IL-6), human IL-6 -receptor and human gp130 (which is a shared signal transducing receptor for several cytokines), and the 2:2 assembly of viral IL-6 and human gp130. The Ig-like domain cross-over structure necessary for GCSF-R activation is consistent with previously reported thermodynamic and mutational analyses.
Ida, Yuma*; Matsuura, Hideaki*; Nagasumi, Satoru; Okamoto, Ryo*; Koga, Yuki*; Katayama, Kazunari*; Otsuka, Teppei*; Goto, Minoru; Nakagawa, Shigeaki; Ishitsuka, Etsuo; et al.
no journal, ,
Large quantity of tritium is demanded for starting up of fusion reactor and engineering test using tritium for fusion blanket system. However, tritium is very rare and kg order of tritium must be produced artificially. Tritium production, by Li(n,)T reaction using the high temperature gas-cooled reactor (HTGR), has been proposed. In this method, loading of Li rods into burnable poison (BP) holes in HTGR is considered. In this paper, the Li rod suited to the demand for the utilization in High Temperature engineering Test Reactor (HTTR) is designed, and tritium production and leakage from Li-rod capsule are evaluated by adjusting the thickness of LiAlO, alumina, and Zr layers. A scenario of irradiation test supposed to be conducted at HTTR for demonstration of the tritium production and containment performance of the Li rod is presented.
Saijo, Tomoaki; Okamoto, Ryo
no journal, ,
Japan declares "Basic Policy for GX Realization" and "Green Growth Strategy" to achieve goals of decarbonization, a stable energy supply, and economic growth. HTTR is expected to contribute to decarbonization by excellent safety and utilizing very high temperature such as hydrogen production. Japan atomic energy agency is being conducted R&D on HTGR technology by using HTTR (High Temperature engineering Test Reactor). HTGR technologies has been accumulated through several tests such as long-term high temperature operation and safety demonstration tests. In March 2024, we carried out loss of forced cooling (LOFC) test at 100% reactor power, demonstrating that reactor power was decreased and kept stable by physical phenomena alone. For R&D of heat application technology, JAEA is being conducted preparation for test of hydrogen production by HTTR as heat source. This presentation describes present status of R&D on HTGR by Japan Atomic Energy Agency.
Endo, Ryo*; Akiyama, Daisuke*; Yokota, Yuki*; Okamoto, Yoshihiro; Kumagai, Yuta; Yomogida, Takumi; Tanida, Hajime; Kirishima, Akira*
no journal, ,
In the Fukushima Daiichi Nuclear Power Plant accident, fuel debris were formed by reaction of molten fuel and reactor structural materials. The fuel debris is composed of many elements and crystalline phases. Therefore, it is inevitable to study various solid phases for debris analysis. In the study, (U,Zr)O solid solution, which is presumed to be generated in the reactor by the reaction between molten nuclear fuel (UO) and oxides of cladding components (ZrO), was prepared as simulated debris. First, powder X-ray diffraction (PXRD) was performed to understand the crystal structure in the bulk region, and the relationship between composition ratio and crystal structure in the micro region was analyzed by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) and micro Raman spectroscopy (MRS) coincidence point analysis. Next, Imaging-XAFS (I-XAFS) and simultaneous analysis of 
-XRD, -XRF, and -XAFS were performed to evaluate the identification of the crystalline phase and U valence in the simulated fuel debris. The objective of this study is to establish a solid phases analysis flow for actual debris that can determine chemical properties from multiple angles by combining multi-scale spectroscopic analyses.
