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Journal Articles

Preheat effect on titanium plate fabricated by sputter-free selective laser melting in vacuum

Sato, Yuji*; Tsukamoto, Masahiro*; Shobu, Takahisa; Yamashita, Yoshihiro*; Yamagata, Shuto*; Nishi, Takaya*; Higashino, Ritsuko*; Okubo, Tomomasa*; Nakano, Hitoshi*; Abe, Nobuyuki*

Applied Physics A, 124(4), p.288_1 - 288_6, 2018/04

 Times Cited Count:10 Percentile:59.67(Materials Science, Multidisciplinary)

The dynamics of titanium (Ti) melted by laser irradiation was investigated in a synchrotron radiation experiment. As an indicator of wettability, the contact angle between a selective laser melting (SLM) baseplate and the molten Ti was measured by synchrotron X-rays at 30 keV during laser irradiation. As the baseplate temperature increased, the contact angle decreased, down to 28 degrees at a baseplate temperature of 500$$^{circ}$$C. Based on this result, the influence of wettability of a Ti plate fabricated by SLM in a vacuum was investigated. It was revealed that the improvement of wettability by preheating suppressed sputtering generation, and a surface having a small surface roughness was fabricated by SLM in a vacuum.

JAEA Reports

Summary of instructor training program in FY2014 aiming at Asian countries introducing nuclear technologies for peaceful use (Contract program)

Hidaka, Akihide; Nakano, Yoshihiro; Watanabe, Yoko; Arai, Nobuyoshi; Sawada, Makoto; Kanaizuka, Seiichi*; Katogi, Aki; Shimada, Mayuka*; Ishikawa, Tomomi*; Ebine, Masako*; et al.

JAEA-Review 2016-011, 208 Pages, 2016/07

JAEA-Review-2016-011-01.pdf:33.85MB
JAEA-Review-2016-011-02.pdf:27.68MB

JAEA has been conducting the Instructor Training Program (ITP) since 1996 under the auspices of MEXT to contribute to human resource development in currently 11 Asian countries in the field of radiation utilization for seeking peaceful use of nuclear energy. ITP consists of Instructor Training Course (ITC), Follow-up Training Course (FTC) and Nuclear Technology Seminars. In the ITP, trainings or seminars relating to technology for nuclear utilization are held in Japan by inviting nuclear related people from Asian countries to Japan and after that, the past trainees are supported during FTC by dispatching Japanese specialists to Asian countries. News Letter is also prepared to provide the broad range of information obtained through the trainings for local people near NPPs in Japan. The present report describes the activities of FY2014 ITP and future challenges for improving ITP more effectively.

Journal Articles

Void denuded zone formation for Fe-15Cr-15Ni steel and PNC316 stainless steel under neutron and electron irradiations

Sekio, Yoshihiro; Yamashita, Shinichiro; Sakaguchi, Norihito*; Takahashi, Heishichiro*

Journal of Nuclear Materials, 458, p.355 - 360, 2015/03

 Times Cited Count:13 Percentile:81.43(Materials Science, Multidisciplinary)

Irradiation-induced void denuded zone (VDZ) formation near grain boundaries was studied to clarify the effects of minor alloying elements on vacancy diffusivity during irradiation in PNC316 steel. The test materials were Fe-15Cr-15Ni steel without additives and PNC316 stainless steel, which contains minor alloying elements. These steels were neutron-irradiated in the experimental fast reactor JOYO and electron-irradiation was also carried out using 1 MeV high voltage electron microscopy. VDZ formation was analyzed from the TEM microstructural observations after irradiation. VDZs were formed near random grain boundaries in both Fe-15Cr-15Ni and PNC316 steels. The VDZ widths in the PNC316 steel were narrower than those for the Fe-15Cr-15Ni steel for all neutron and electron irradiations. The VDZ width analysis implied that the vacancy diffusivity was reduced in PNC316 steel as a result of interaction of vacancies with minor alloying elements.

Journal Articles

Seawater immersion tests of irradiated Zircaloy-2 cladding tube

Sekio, Yoshihiro; Yamagata, Ichiro; Yamashita, Shinichiro; Inoue, Masaki; Maeda, Koji

Proceedings of 2014 Nuclear Plant Chemistry Conference (NPC 2014) (USB Flash Drive), 10 Pages, 2014/10

In the Fukushima Dai-ichi Nuclear Power Plant accident, seawater was temporarily injected into the spent fuel pools since water cooling and feeding functions were lost. For fuel assemblies which experienced seawater immersion, surface corrosion due to seawater constituents and the resultant degradation of mechanical property are of concern. Therefore, in order to assess the integrity of fuel assemblies (especially cladding tubes), the effects of seawater immersion on corrosion behavior and mechanical properties for as-recieved and irradiated Zircaloy-2 cladding tubes were investigated in the present study. As a result, no obvious surface corrosion and no significant degradation in the tensile strength property were observed after both artificial and natural seawater immersion tests for both steels. This suggests that the effects of seawater immersions on corrosion behavior and mechanical property (especially tensile property) for Zircaloy-2 cladding tubes are probably negligible.

Journal Articles

Effect of additional minor elements on accumulation behavior of point defects under electron irradiation in austenitic stainless steels

Sekio, Yoshihiro; Yamashita, Shinichiro; Sakaguchi, Norihito*; Takahashi, Heishichiro

Materials Transactions, 55(3), p.438 - 442, 2014/03

 Times Cited Count:8 Percentile:46.14(Materials Science, Multidisciplinary)

In order to perform the comparative evaluations for vacancy diffusivity and flux between a base alloy and modified alloys, the void denuded zones (VDZ) widths were measured from the TEM in-situ observation during electron irradiation in the SUS316L, SUS316L-V and SUS316L-Zr steels. As a result, VDZs with given widths were formed near GBs. Then, the VDZ widths were different depending on steels, and the width was narrower due to addition of minor alloying elements which strongly interact with vacancies. Furthermore, from the analyses of measured VDZ widths in the SUS316L and SUS316L-V steels, the changes of vacancy diffusivity, vacancy flux and excess vacancy concentration were estimated as 0.50, 0.71 and 1.41, respectively. The decreases of vacancy diffusivity and flux during electron irradiation would be due to the interaction of vacancies with added minor elements, while the enhancement of the excess vacancy concentration would be caused by trapping effects due to alloying elements.

JAEA Reports

Evaluation of irradiation behavior on oxide dispersion strengthened (ODS) steel claddings irradiated in Joyo/CMIR-6

Yano, Yasuhide; Otsuka, Satoshi; Yamashita, Shinichiro; Ogawa, Ryuichiro; Sekine, Manabu; Endo, Toshiaki; Yamagata, Ichiro; Sekio, Yoshihiro; Tanno, Takashi; Uwaba, Tomoyuki; et al.

JAEA-Research 2013-030, 57 Pages, 2013/11

JAEA-Research-2013-030.pdf:48.2MB

It is necessary to develop the fast reactor core materials, which can achieve high-burnup operation improving safety and economical performance. Ferritic steels are expected to be good candidate core materials to achieve this objective because of their excellent void swelling resistance. Therefore, oxide dispersion strengthened (ODS) ferritic steel and 11Cr-ferritic/martensitic steel (PNC-FMS) have been respectively developed for cladding and wrapper tube materials in Japan Atomic Energy Agency. In this study, the effects of fast neutron irradiation on mechanical properties and microstructure of 9Cr-and 12Cr-ODS steel claddings for fast reactor were investigated. Specimens were irradiated in the experimental fast reactor Joyo using the CMIR-6 at temperatures between 420 and 835$$^{circ}$$C to fast neutron doses ranging from 16 to 33 dpa. The post-irradiation ring tensile tests were carried out at irradiation temperatures.

Journal Articles

Mass production of Nb$$_{3}$$Sn conductors for ITER toroidal field coils in Japan

Takahashi, Yoshikazu; Isono, Takaaki; Hamada, Kazuya; Nunoya, Yoshihiko; Nabara, Yoshihiro; Matsui, Kunihiro; Hemmi, Tsutomu; Kawano, Katsumi; Koizumi, Norikiyo; Oshikiri, Masayuki; et al.

IEEE Transactions on Applied Superconductivity, 22(3), p.4801904_1 - 4801904_4, 2012/06

 Times Cited Count:7 Percentile:44.38(Engineering, Electrical & Electronic)

Japan Atomic Energy Agency is the first to start the mass production of the TF conductors in Phase IV in March 2010 among the 6 parties who are procuring TF conductors in the ITER project. The conductor is cable-in-conduit conductor with a central spiral. A total of 900 Nb$$_{3}$$Sn strands and 522 copper strands are cabled around the central spiral and then wrapped with stainless steel tape whose thickness is 0.1 mm. Approximately 60 tons of Nb$$_{3}$$Sn strands were manufactured by the two suppliers in December 2010. This amount corresponds to approximately 55% of the total contribution from Japan. Approximately 30% of the total contribution from Japan was completed as of February 2011. JAEA is manufacturing one conductor per month under a contract with two Japanese companies for strands, one company for cabling and one company for jacketing. This paper summarizes the technical developments including a high-level quality assurance. This progress is a significant step in the construction of the ITER machine.

Journal Articles

Fuel performance evaluation of rock-like oxide fuels

Shirasu, Noriko; Kuramoto, Kenichi; Nakano, Yoshihiro; Yamashita, Toshiyuki; Kimura, Yasuhiko; Nihei, Yasuo; Ogawa, Toru

Journal of Nuclear Materials, 376(1), p.88 - 97, 2008/05

 Times Cited Count:13 Percentile:68.01(Materials Science, Multidisciplinary)

The concept of the rock-like oxide (ROX) fuel has been developed for the annihilation of excess plutonium in light water reactors. Irradiation tests and post-irradiation examinations were carried out on candidate ROX fuels. The ternary fuel of YSZ-spinel-corundum system, the single-phase fuels of YSZ, the particle dispersed fuels of YSZ in spinel or corundum matrix, and the blended fuels of YSZ and spinel or corundum matrix were fabricated and submitted to irradiation tests. The fuels containing spinel showed chemical instabilities with the vaporization of MgO component, which caused fuel restructuring. The swelling behavior was improved with the particle-dispersed fuels. However, the particle-dispersed fuels showed higher fractional gas release (FGR) than blended type fuels. The FGR of YSZ single-phase fuels were comparable to what would be expected for UO$$_{2}$$ fuels. The YSZ single-phase fuel showed the best irradiation performance among the ROX fuels investigated.

Journal Articles

Study of rock-like oxide fuels under irradiation

Shirasu, Noriko; Kuramoto, Kenichi; Nakano, Yoshihiro; Yamashita, Toshiyuki; Ogawa, Toru

Journal of Power and Energy Systems (Internet), 2(1), p.145 - 152, 2008/00

To evaluate the irradiation behavior of the rock-like oxide fuel, irradiation experiments were carried out. Three fuels were prepared; a single phase fuel of yttria-stabilized zirconia containing UO$$_{2}$$ (U-YSZ) and two types of particle-dispersed fuels of U-YSZ particles in spinel or corundum matrix. These fuels were irradiated in JRR-3 for about 280 days. The burnups were about 11% FIMA. The fission gas release rate (FGR) was determined by puncture test and gas analysis. Corundum-based fuel showed extremely high FGR (88%). The temperature of U-YSZ single-phase fuel pellets was highest among the fuels, because of its low thermal conductivity. Nevertheless the U-YSZ single-phase fuel showed very low FGR (5%). Microstructure analyses of irradiated fuel pellets were carried out by ceramography and EPMA. The restructuring of fuel pellet was not observed in the spinel-based fuel irradiated below 1400 K.

Journal Articles

Study of rock-like oxide fuels under irradiation

Shirasu, Noriko; Kuramoto, Kenichi; Nakano, Yoshihiro; Yamashita, Toshiyuki; Ogawa, Toru

Proceedings of 15th International Conference on Nuclear Engineering (ICONE-15) (CD-ROM), 7 Pages, 2007/04

To evaluate the irradiation behavior of the rock-like oxide fuel, irradiation experiments were carried out. Three fuels were prepared; a single phase fuel of yttria-stabilized zirconia containing UO$$_{2}$$ (U-YSZ) and two particle-dispersed fuels of U-YSZ particles in spinel or corundum matrix. These fuels were irradiated in JRR-3 for about 280 days. The burnups were about 11% FIMA. The fission gas release rate (FGR) was determined by puncture test and gas analysis. Corundum-based fuel showed extremely high FGR (88%). On the other hand, the U-YSZ single-phase fuel showed very low FGR (5%). Microstructure analyses for irradiated fuel pellets were carried out by ceramography and EPMA. The restructuring of fuel pellet was not observed in the spinel-based fuel irradiated below 1400 K. Significant appearance changes were not also observed for corundum-based fuel.

Journal Articles

Irradiation behavior of rock-like oxide fuels

Yamashita, Toshiyuki; Kuramoto, Kenichi; Shirasu, Noriko; Nakano, Yoshihiro; Akie, Hiroshi; Nagashima, Hisao; Kimura, Yasuhiko; Omichi, Toshihiko*

Journal of Nuclear Materials, 320(1-2), p.126 - 132, 2003/07

 Times Cited Count:10 Percentile:58.26(Materials Science, Multidisciplinary)

Two irradiation tests on the rock-like oxide (ROX) fuels, small disk-shape fuel targets and pellet-type fuels, were performed in order to clarify in-pile irradiation stabilities. Swelling, fractional fission gas release (FGR) and phase change were examined by puncture test, profilometry and ceramography. YSZ single-phase fuel showed an excellent irradiation behavior, ie. low fission gas release (less than 3%), negligible swelling and no appreciable restructuring. The particle dispersed fuels showed lower swelling and higher fission gas release than those of mechanically blended fuels. Spinel decomposition and subsequence restructuring in the spinel matrix fuels was observed for the first time in the present investigation. It would be possible to reduce the FGR of the spinel matrix fuels, if the maximum fuels temperature is limited below 1700 K where neither spinel decomposition nor restructuring was observed. Damaged area of spinel matrix due to fission fragment irradiation seemed to be confined to thin layers around the surface of YSZ particles.

JAEA Reports

Gological Structure Modeling Around Mill Tailing Yard

Takano, Hitoshi*; Sugimoto, Yoshihiro*; Yamashita, Tadashi*; Yamada, Naoyuki*

JNC TJ6420 2003-011, 122 Pages, 2003/02

JNC-TJ6420-2003-011.pdf:4.12MB

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Journal Articles

Rock-like oxide fuels and their burning in LWRs

Yamashita, Toshiyuki; Kuramoto, Kenichi; Akie, Hiroshi; Nakano, Yoshihiro; Shirasu, Noriko; Nakamura, Takehiko; Kusagaya, Kazuyuki*; Omichi, Toshihiko*

Journal of Nuclear Science and Technology, 39(8), p.865 - 871, 2002/08

 Times Cited Count:25 Percentile:83.26(Nuclear Science & Technology)

Research on the plutonium rock-like oxide (ROX) fuels and their once-through burning in light water reactors has been performed to establish an option for utilizing and disposing effectively the excess plutonium. The ROX fuel is a sort of the inert matrix fuels and consists of mineral-like compounds such as yttria stabilized zirconia, spinel and corundum. A particle-dispersed fuel was devised to reduce damage by heavy fission fragments. Some preliminary results on swelling, fractional gas release and microstructure change for five ROX fuels were obtained from the irradiation test and successive post-irradiation examinations. Inherent disadvantages of the Pu-ROX fuel cores could be improved by adding 238U or 232Th as resonant materials, and all improved cores showed a nearly the same characteristics as the conventional UO2 core during transient conditions. The threshold enthalpy of the ROX fuel rod failure was found to be comparable to the fresh UO2 rod by pulse-irradiation tests simulating reactivity initiated accident conditions.

Journal Articles

Neutron scattering study of linear-chain Haldane compounds NDMAZ and NDMAP

Metoki, Naoto; Koike, Yoshihiro; Matsuoka, Yuki; Kobayashi, Tatsuo*; Yamashita, Masahiro*

Journal of Magnetism and Magnetic Materials, 226-230(Part.1), p.414 - 416, 2001/05

no abstracts in English

Journal Articles

Current status of researches on the plutonium rock-like oxide fuel and its burning in light water reactors

Yamashita, Toshiyuki; Akie, Hiroshi; Nakano, Yoshihiro; Kuramoto, Kenichi; Nitani, Noriko; Nakamura, Takehiko

Progress in Nuclear Energy, 38(3-4), p.327 - 330, 2001/02

 Times Cited Count:12 Percentile:66.3(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Rock-like oxide fuels for burning excess plutonium in LWRs

Yamashita, Toshiyuki; Kuramoto, Kenichi; Akie, Hiroshi; Nakano, Yoshihiro; Nitani, Noriko; Nakamura, Takehiko; Kusagaya, Kazuyuki*; Omichi, Toshihiko*

Proceedings of Workshop on Advanced Reactors with Innovative Fuels (ARWIF 2001) (CD-ROM), 10 Pages, 2001/00

no abstracts in English

Journal Articles

Neutron scattering studies in the linear-chain Halden materials, NDMAZ and NDMAP

Koike, Yoshihiro; Metoki, Naoto; Morii, Yukio; Kobayashi, Tatsuo*; Ishii, Tomohiko*; Yamashita, Masahiro*

Journal of the Physical Society of Japan, 69(12), p.4034 - 4042, 2000/12

 Times Cited Count:6 Percentile:47.5(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Development of rock-like fuels for plutonium annihilation of plutonium in LWRs

Yamashita, Toshiyuki; Akie, Hiroshi; Nitani, Noriko; Nakano, Yoshihiro; Nakamura, Takehiko; Shiratori, Tetsuo; Suzuki, Yasufumi

Proceedings of International Conference on Future Nuclear Systems (GLOBAL '99) (CD-ROM), p.8 - 0, 1999/00

no abstracts in English

JAEA Reports

ITER neutral beam injection system; Japanese design proposal

Ohara, Yoshihiro; Tanaka, Shigeru; Akiba, Masato; Araki, Masanori; Fujisawa, Noboru; Hanada, Masaya; Inoue, Takashi; *; Mizuno, Makoto; Okumura, Yoshikazu; et al.

JAERI-M 91-052, 176 Pages, 1991/03

JAERI-M-91-052.pdf:4.07MB

no abstracts in English

Journal Articles

Neutronics of neutral beam injector for ITER; Japanese proposal

Inoue, Takashi; Akiba, Masato; Araki, Masanori; Hanada, Masaya; *; Mizuno, Makoto; Okumura, Yoshikazu; Ohara, Yoshihiro; Seki, Masahiro; Tanaka, Shigeru; et al.

Fusion Engineering and Design, 18, p.369 - 376, 1991/00

 Times Cited Count:2 Percentile:32.61(Nuclear Science & Technology)

no abstracts in English

40 (Records 1-20 displayed on this page)