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Toyama, Takeshi*; Tanno, Takashi; Yano, Yasuhide; Inoue, Koji*; Nagai, Yasuyoshi*; Otsuka, Satoshi; Miyazawa, Takeshi; Mitsuhara, Masatoshi*; Nakashima, Hideharu*; Onuma, Masato*; et al.
Journal of Nuclear Materials, 599, p.155252_1 - 155252_14, 2024/10
Times Cited Count：6 Percentile：71.07(Materials Science, Multidisciplinary)We investigated the stability of oxide nano particles in oxide dispersion-strengthened (ODS) steel, which is a promising candidate material for next-generation reactors, under neutron irradiation at high temperature to high doses. MA957, a 14Cr-ODS steel, was irradiated with Joyo in Japan Atomic Energy Agency under irradiation conditions of 130 dpa at 502
C, 154 dpa at 589C, and 158 dpa at 709C. Three-dimensional atom probe (3D-AP) and transmission electron microscope (TEM) observation were performed to characterize the oxide particles in the ODS steels. A high number density of Y-Ti-O particle was observed in the unirradiated and irradiated samples. Almost no change in the morphology of the oxide particles, i.e. average diameter, number density, and chemical composition, has been observed in the samples irradiated to 130 dpa at 502C and to 154 dpa at 589C. A slight decrease in number density was observed in the sample irradiated to 158 dpa at 709CC. The hardness of any of the irradiated samples was almost unchanged from that of the unirradiated sample. It was revealed that the oxide particles existed stable, and the strength of the material was sufficiently maintained even after being neutron irradiated to high dose of 
160 dpa at high temperature up to 700C. A part of this study includes the results of MEXT Innovative Nuclear Research and Development Program Grant Number JPMXD0219214482.
C to 1000CImagawa, Yuya; Hashidate, Ryuta; Miyazawa, Takeshi; Onizawa, Takashi; Otsuka, Satoshi; Yano, Yasuhide; Tanno, Takashi; Kaito, Takeji; Onuma, Masato*; Mitsuhara, Masatoshi*; et al.
Journal of Nuclear Science and Technology, 61(6), p.762 - 777, 2024/06
Times Cited Count：8 Percentile：76.12(Nuclear Science & Technology)The Japan Atomic Energy Agency has been developing 9Cr-oxide dispersion strengthened (ODS) steel as a fuel cladding material for sodium-cooled fast reactors (SFRs). Previous studies have formulated the creep rupture equation for 650C to 850C. However, little data have been obtained above 850C, and no equation has been formulated. This study conducted creep tests to evaluate creep strength at 700C to 1000C. Two creep test methods, the internal pressure and ring creep tests under development, were used, and the validation of the ring creep test method was conducted. The results showed that 9Cr-ODS steel undergoes almost no strength change due to the matrix's phase transformation, and a single equation can express a creep rupture strength from 700C to 1000C. In validating the ring creep test method, analysis clarified the effect of stress concentration on the specimen. Plastic deformation occurs at high initial stress and may lead to early rupture. The results will be essential for future creep testing and evaluation of neutron-irradiated 9Cr-ODS steel.
Miyazawa, Takeshi; Tanno, Takashi; Imagawa, Yuya; Hashidate, Ryuta; Yano, Yasuhide; Kaito, Takeji; Otsuka, Satoshi; Mitsuhara, Masatoshi*; Toyama, Takeshi*; Onuma, Masato*; et al.
Journal of Nuclear Materials, 593, p.155008_1 - 155008_16, 2024/05
Times Cited Count：6 Percentile：77.42(Materials Science, Multidisciplinary)Nagai, Yuya; Shuji, Yoshiyuki; Kawasaki, Takeshi; Aita, Takahiro; Kimura, Yasuhisa; Nemoto, Yasunori*; Onuma, Takeshi*; Tomiyama, Noboru*; Hirano, Koji*; Usui, Yasuhiro*; et al.
JAEA-Technology 2022-039, 117 Pages, 2023/06
JAEA-Technology-2022-039.pdf:11.96MB
Japan Atomic Energy Agency (JAEA) manages wide range of nuclear facilities. Many of these facilities are required to be performed adjustment with the aging and complement with the new regulatory standards and the earthquake resistant, since the Great East Japan Earthquake and the Fukushima Daiichi Nuclear Power Station accident. It is therefore desirable to promote decommissioning of facilities that have reached the end of their productive life in order to reduce risk and maintenance costs. However, the progress of facility decommissioning require large amount of money and radioactive waste storage space. In order to address these issues, JAEA has formulated a "The Medium/Long-Term Management Plan of JAEA Facilities" with three pillars: (1) consolidation and prioritization of facilities, (2) assurance of facility safety, and (3) back-end countermeasures. In this plan, Plutonium Fuel Fabrication Facility has been selected as primary decommissioned facility, and dismantling of equipment in the facilities have been underway. In this report, size reduction activities of the glove box W-9 and a part of tunnel F-1, which was connected to W-9, are presented, and the obtained findings are highlighted. The glovebox W-9 had oxidation & reduction furnace, and pellet crushing machine as equipment interior. The duration of activity took six years from February 2014 to February 2020, including suspended period of 4 years due to the enhanced authorization approval process.
Mitsuhara, Masatoshi*; Kurino, Koichi*; Yano, Yasuhide; Otsuka, Satoshi; Toyama, Takeshi*; Onuma, Masato*; Nakashima, Hideharu*
Tetsu To Hagane, 109(3), p.189 - 200, 2023/03
Times Cited Count：1 Percentile：5.37(Metallurgy & Metallurgical Engineering)Oxide Dispersion Strengthened (ODS) ferritic steel, a candidate material for fast reactor fuel cladding, has low thermal expansion, good thermal conductivity, and excellent resistance to irradiation damage and high temperature strength. The origin of the excellent high-temperature strength lies in the dispersion of fine oxides. In this study, creep tests at 700 or 750C, which are close to the operating temperatures of fast reactors, and high-temperature tensile tests at 900 to 1350 C, which simulate accident conditions, were conducted on 9Cr ODS ferritic steels, M11 and MP23, and 12Cr ODS ferritic steel, F14, to confirm the growth behavior of oxides. In the M11 and F14 creep test samples, there was little oxide growth or decrease in number density from the initial state, indicating that dispersion strengthening by oxides was effective during deformation. After creep deformation of F14, the development of dislocation substructures such as dislocation walls and subgrain boundaries was hardly observed, and mobile dislocations were homogeneously distributed in the grains. The dislocation density increased with increasing stress during the creep test. In the high-temperature ring tensile tests of MP23 and F14, the strength of both steels decreased at higher temperatures. In MP23, elongation decreased with increasing test temperature from 900 to 1100 C, but increased at 1200 C, decreased drastically at 1250 C, and increased again at 1300 C. In F14, elongation decreased with increasing temperature. It was inferred that the formation of the 
-ferrite phase was responsible for this complex change in mechanical properties of MP23 from 1200 to 1300 C.
Kinoshita, Motoyasu*; Geng, H. Y.*; Chen, Y.*; Kaneta, Yasunori*; Iwasawa, Misako*; Onuma, Toshiharu*; Sonoda, Takeshi*; Yasunaga, Kazufumi*; Matsumura, Sho*; Yasuda, Kazuhiro*; et al.
Proceedings of 2006 International Meeting on LWR Fuel Performance (TopFuel 2006) (CD-ROM), p.248 - 254, 2006/10
The New Crossover Project (NXO) is studying effect of fission irradiation on fuel material that research activity is crossing over universities, national and private laboratories. Simulation studies are being performed to find principal and triggering processes of the rim-structure formation in high burnup LWR fuel pellet, using accelerator irradiation and computational calculations. Accelerator irradiation, high energy electron irradiation, fission energy particle beam and ion implantation (ragegas atoms) and combined overlapping irradiations are being performed. For the target of irradiation, CeO
isused as simulation of nuclear fuel. The initial results were such as planar structure made by Oxygen defects created by high energy electrons, and surface modification similar to grain-sub-division created by high fluence high energy particle irradiations.
Amano, Hikaru; Matsunaga, Takeshi; Nagao, Seiya; ; Watanabe, Miki*; Ueno, Takashi; Onuma, Yoshikazu*
Organic Geochemistry, 30, p.437 - 442, 1999/00
Times Cited Count：29 Percentile：51.91(Geochemistry & Geophysics)no abstracts in English
Amano, Hikaru; Hanzawa, Yukiko; Watanabe, Miki*; Matsunaga, Takeshi; Ueno, Takashi; Nagao, Seiya; Yanase, Nobuyuki; Onuma, Yoshikazu*
Proceedings of OECD/NEA Workshop on Evaluation of Speciation Technology, p.211 - 218, 1999/00
no abstracts in English
Matsunaga, Takeshi; Ueno, Takashi; Amano, Hikaru; Y.Tkatchenko*; A.Kovalyov*; Watanabe, Miki*; Onuma, Yoshikazu*
Journal of Contaminant Hydrology, 35, p.101 - 113, 1998/00
Times Cited Count：46 Percentile：74.33(Environmental Sciences)no abstracts in English
Amano, Hikaru; Matsunaga, Takeshi; Ueno, Takashi; Nagao, Seiya; Watanabe, Miki*; ; Onuma, Yoshikazu*
KURRI-KR-18, p.201 - 212, 1997/00
no abstracts in English
Amano, Hikaru; Watanabe, Miki*; Onuma, Yoshikazu*; Ueno, Takashi; Matsunaga, Takeshi; N.D.Kuchma*
The Role of Humic Substances in the Ecosystems and in Environmental Protection, 0, p.709 - 716, 1997/00
no abstracts in English
Watanabe, Miki*; Amano, Hikaru; Onuma, Yoshikazu*; Ueno, Takashi; Matsunaga, Takeshi; Yanase, Nobuyuki
Proc. of 4th Int. Conf. on Nucl. and Radiochemistry, 2, 4 Pages, 1996/00
no abstracts in English
Amano, Hikaru; Matsunaga, Takeshi; Ueno, Takashi; Onuma, Yoshikazu*; Watanabe, Miki*; Yanase, Nobuyuki; Nagao, Seiya; Sukhoruchkin, A. K.*
Proceedings of 5th International Scientific and Technical Conference on the Problems of Liquidation of Chernobyl Accident Consequences, P. 74, 1996/00
no abstracts in English
Tanno, Takashi; Fujita, Koji; Yano, Yasuhide; Otsuka, Satoshi; Nakashima, Hideharu*; Mitsuhara, Masatoshi*; Onuma, Masato*; Toyama, Takeshi*; Kaito, Takeji
no journal, ,
By applying oxide dispersion-strengthened (ODS) steel, which has excellent high-temperature strength, to the fuel cladding tube, it is expected that the risk of fuel pin rupture up to the ultra-high temperature range including accidents will be reduced and the safety of the plant will be improved. Oxide dispersoids as a reinforced phase in ODS steels are considered to be more stable than carbonitrides and intermetallic compounds used as reinforced phases in other heat-resistant alloys. It is important to actually ensure that the metallographical structure and strength are maintained up to the ultra-high temperature. In this study, in order to evaluate the performance limit of ODS steel against ultra-high temperature, extreme heat treatments simulating accident situations were carried out, and then the macrostructure and strength were evaluated. Regarding the macrostructure, it was generally stable up to 1250 C and the crystal grains were fine, but it was coarsened at 1300 C or higher. On the other hand, it was found that the hardness decreased at 1250 C or higher. This theme was supported by JPMXD0219214482, a nuclear power system research and development project of the Ministry of Education, Culture, Sports, Science and Technology.
Sekikawa, Takuya; Kai, Takeshi; Onuma, Sota*; Haga, Yoshinori; Yokoya, Akinari*
no journal, ,
Uracil is a base of ribonucleic acid (RNA), which is responsible for copying genetic information from deoxyribonucleic acid (DNA) and transporting it to ribosomes, where protein synthesis takes place. The radiation sensitizing effect of uracil bromide, in which bromine is substituted for a part of uracil, has been expected to be effective. In this study, we used the first-principles calculation software OpenMX to investigate the effect of partial substitution of halogen for uracil. The results of calculations targeting molecules with uracil partially substituted with fluorine and bromine showed that the electrons in uracil halide are easily ionized in the order of fluorine and bromine. The results of this study are expected to contribute to the development of radiosensitizers for radiotherapy.
Kinoshita, Motoyasu; Yasunaga, Kazufumi*; Sonoda, Takeshi*; Iwase, Akihiro*; Ishikawa, Norito; Sataka, Masao; Yasuda, Kazuhiro*; Matsumura, Sho*; Geng, H. Y.*; Ichinomiya, Takashi*; et al.
no journal, ,
We show the outline of achievements of New Cross Over (NXO) project. Concerning the grain subdivision of ceramics fuel at high burnup, we are trying to clarify the mechanisms and to develop the simulation methods. The main high lights are as follow as: (1) We have reproduced the grain subdivision of CeO, by means of ion implanter and TUNDEM accelerator. (2) We performed computational science study concerning the relocation of oxygen. In case of oxygen exess conditions, first principal calculation reproduced the orderring structure. TAD calculation shows that the exess oxygen compose clusters and diffuses rapidly even if low temperature.
Chen, Y.*; Kaneta, Yasunori*; Geng, H. Y.*; Shang, J. C.*; Iwasawa, Misako*; Onuma, Toshiharu*; Sonoda, Takeshi*; Ichinomiya, Takashi*; Suzudo, Tomoaki; Itakura, Mitsuhiro; et al.
no journal, ,
The outcome of the New Crossover Project Study is outlined. The computational results includes the ab-initio study, molecular dynamics, statistical dynamics/thermal dynamics and meso-scopic modeling, and the experimental results given by an accelerator is also mentioned. Finally, we mention the future plans and the problems.
Yamaguchi, Daisuke; Noda, Yohei; Koizumi, Satoshi; Hasegawa, Yoshio*; Hishinuma, Yukio*; Suzuki, Masashi*; Kodama, Hiroto*; Onuma, Masato*; Oba, Yojiro*; Yuasa, Takeshi*; et al.
no journal, ,
Nowadays industrial materials tend to include a variety of additives and to be a composite of them to satisfy a high request for intelligent function and durability. Elucidation of such a multi-component and hierarchical structure is really a tough work but indispensable to learn the fundamentals of relation between the structure and property and to attain a reasonable improvement of those materials. Combined use of small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS) often gives a good clue to decompose the total scattering of the organic/inorganic composite into the partial scattering from a particular component. Two examples will be demonstrated here for extracting the structural information from the composite specimen via this method; one is the distribution of the dopant nitrogen atoms in the porous photocatalyst and the other is the dispersion state of fillers in the rubber matrix.
Yano, Yasuhide; Tanno, Takashi; Kaito, Takeji; Otsuka, Satoshi; Onuma, Masato*; Nakashima, Hideharu*; Toyama, Takeshi*
no journal, ,
no abstracts in English
Yano, Yasuhide; Toyama, Takeshi*; Tanno, Takashi; Otsuka, Satoshi; Mitsuhara, Masatoshi*; Nakashima, Hideharu*; Onuma, Masato*; Kaito, Takeji
no journal, ,
no abstracts in English
