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Kimata, Tetsuya*; Kato, Sho*; Yamaki, Tetsuya; Yamamoto, Shunya; Kobayashi, Tomohiro*; Terai, Takayuki*
Surface & Coatings Technology, 306(Part A), p.123 - 126, 2016/11
Times Cited Count：13 Percentile：52.49(Materials Science, Coatings & Films)Platinum (Pt) nanoparticle catalysts with oxygen reduction reaction (ORR) activity are required for practical applications of polymer electrolyte fuel cells. We prepared Pt nanoparticles on an Ar
-irradiated glassy carbon (GC) surface by a radio-frequency magnetron sputtering method to investigate the influence of the ion-induced lattice defects in GC on the ORR activity of the deposited Pt nanoparticles. Interestingly, the Pt nanoparticles on the irradiated surface exhibited ca. 2.5 times higher specific activity than those on the non-irradiated one. X-ray photoelectron spectroscopy suggested the interfacial Pt-C interaction occurring between the irradiated GC and Pt nanoparticles, which should be a reason for improvement of the ORR activity.
Kato, Sho; Yamaki, Tetsuya; Yamamoto, Shunya; Hakoda, Teruyuki; Kawaguchi, Kazuhiro; Kobayashi, Tomohiro*; Suzuki, Akihiro*; Terai, Takayuki*
Nuclear Instruments and Methods in Physics Research B, 314, p.149 - 152, 2013/11
Times Cited Count：2 Percentile：19.73(Instruments & Instrumentation)We implanted 100 keV W in unpolished GC substrates at nominal fluences up to 
ions/cm
. The implanted samples were electrochemically anodized in a NaOH aqueous solution to etch the surface layer. The analyses were performed by X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectrometry (RBS), and transmission electron microscopy (TEM). XPS W 4f spectra indicated the formation of carbides as reported previously. The electrochemical etching clearly increased the W concentration on the surface. According to the RBS results, half of the implanted W atoms were retained in the substrate, while the rest should escape to the etching solution. The cross-sectional TEM image revealed a uniform distribution of WC particles with a diameter of less than 10 nm just near the surface region.
Kato, Sho; Yamaki, Tetsuya; Yamamoto, Shunya; Hakoda, Teruyuki; Kawaguchi, Kazuhiro; Kobayashi, Tomohiro*; Suzuki, Akihiro*; Terai, Takayuki*
Transactions of the Materials Research Society of Japan, 38(1), p.81 - 84, 2013/03
Nanoparticles were formed by 100 keV tungsten-ion implantation in unpolished glassy carbon substrates at nominal fluences of 
- 
ions/cm. The implanted samples were analyzed by Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy, hydrodynamic voltammetry using a rotating disk electrode, and field emission scanning electron microscopy. A significant sputtering effect changed the depth profile during the course of irradiation and limited the amount of tungsten retainable in the substrate in agreement with our calculated distributions. The nanoparticles were composed of tungsten carbide and dispersed uniformly with diameters of around 10 nm.
Nakamura, Kinya*; Kato, Tetsuya*; Ogata, Takanari*; Nakajima, Kunihisa; Iwai, Takashi; Arai, Yasuo
Proceedings of International Conference on Fast Reactors and Related Fuel Cycles (FR 2009) (CD-ROM), 12 Pages, 2012/00
The first irradiation campaign of U-Pu-Zr metal fuel in Japan is planned in the experimental fast reactor JOYO. In the fabrication of U-Pu-Zr fuel, two methods were adopted for preparing U-Pu alloy from the oxide; one is the electrochemical reduction and the other is the electrorefining followed by reductive extraction. Injection casting for U-Pu-Zr slug was carried out after adding U and Zr metals to meet the target specifications of the irradiated fuel. Several conditions of Na-bonding process were determined from the results of tests using simulated metal fuel pins. Based on these results, six U-Pu-Zr fuel pins for the irradiation tests are now being fabricated.
Nakamura, Kinya*; Ogata, Takanari*; Kikuchi, Hironobu; Iwai, Takashi; Nakajima, Kunihisa; Kato, Tetsuya*; Arai, Yasuo; Uozumi, Koichi*; Hijikata, Takatoshi*; Koyama, Tadafumi*; et al.
Nihon Genshiryoku Gakkai Wabun Rombunshi, 10(4), p.245 - 256, 2011/12
Sodium-bonded metallic fuel elements were fabricated for the first time in Japan for the irradiation test in the experimental fast test reactor JOYO. U-20Pu-10Zr fuel slugs of 200 mm in length and approximately 5 mm in diameter were fabricated in a small-scale injection casting furnace. Each fuel slug was loaded into the ferritic martenstic stainless steel (PNC-FMS) cladding tube with the sodium thermal bond, thermal insulator and reflector in a helium gas atmosphere glove box. After top-end plug welding to the cladding tube and heat treatment of the welding area, each fuel element was subjected to the sodium bonding process. After the inspection such as element length, gas plenum length and helium-leak tightness, six metallic fuel elements are transported to the JOYO site for the coming irradiation test.
Nakamura, Kinya*; Ogata, Takanari*; Kikuchi, Hironobu; Iwai, Takashi; Nakajima, Kunihisa; Kato, Tetsuya*; Arai, Yasuo; Koyama, Tadafumi*; Itagaki, Wataru; Soga, Tomonori; et al.
Proceedings of International Conference on Toward and Over the Fukushima Daiichi Accident (GLOBAL 2011) (CD-ROM), 8 Pages, 2011/12
CRIEPI and JAEA have fabricated sodium-bonded metallic fuel elements for the first time in Japan as a collaborative research, for use in the irradiation test at the experimental fast test reactor Joyo. The irradiation test aims to assess the irradiation behavior of the fuel and the internal wastage of the stainless-steel cladding by rare-earth fission products at a maximum cladding temperature above 873 K. U-20 wt% Pu-10 wt% Zr alloy fuel slugs of 200 mm length were fabricated in an injection-casting furnace using U metal, U-Pu alloy and Zr metal. Two types of fuel slug were fabricated, i.e., 5.05 mm and 4.95 mm in diameter, and loaded into a ferritic-martensitic stainless-steel cladding tubes, respectively. After top-end-plug welding to the cladding tube, each fuel element was subjected to sodium bonding to fill the annular gap between the fuel slug and the cladding with melted sodium. The fabrication results indicated that the characteristics of the fuel elements were within the required specifications.
Nakamura, Kinya*; Ogata, Takanari*; Kato, Tetsuya*; Nakajima, Kunihisa; Arai, Yasuo
Proceedings of International Conference on Advanced Nuclear Fuel Cycle; Sustainable Options & Industrial Perspectives (Global 2009) (CD-ROM), p.1487 - 1495, 2009/09
The U-Pu-Zr fuel slugs for the irradiation test in JOYO were manufactured in a small-scale injection casting furnace. The U-Pu alloy ingots as starting materials were prepared by means of electrochemical reduction of the dioxides. The U-Pu-Zr fuel slugs manufactured met all the specifications determined based on not only the results of preliminary tests but also the specification of EBR-II driver fuels. The americium to plutonium ratio in the fuel slugs slightly decreased after the injection casting process.
O meltKato, Tetsuya*; Sakamura, Yoshiharu*; Iwai, Takashi; Arai, Yasuo
Radiochimica Acta, 97(4-5), p.183 - 186, 2009/05
Times Cited Count：4 Percentile：30.49(Chemistry, Inorganic & Nuclear)The solubility of Pu and rare-earths were measured in LiCl-LiO melt where the sesquioxides were precipitated. As shown in the solubility measurement of Pu(III), Nd(III) and Gd(III) at 923 K, the solubility increased proportionally with LiO concentration in the melt. It was also found that the element of larger ionic radius has higher solubility as far as the trivalent rare-earths and Pu.
Kato, Tetsuya*; Inoue, Tadashi*; Iwai, Takashi; Arai, Yasuo
Journal of Nuclear Materials, 357(1-3), p.105 - 114, 2006/10
Times Cited Count：104 Percentile：98.82(Materials Science, Multidisciplinary)Electrorefining in the molten LiCl-KCl eutectic salt containing actinides(An) and rare-earths(RE) was conducted to recover up to 10 wt% An into liquid Cd cathode, which is much higher than the solubility of An in liquid Cd at the experimental temperature. In the saturated Cd cathode, An and RE were recovered to form a compound of the PuCd
lattice, MCd. The separation factors of RE against Pu were defined as (RE/Pu in the Cd cathode)/(RE/Pu in the salt) and calculated for the saturated Cd alloy including MCd. The separation factors for the Cd cathodes were a little larger than the equilibrium values.
Kato, Tetsuya*; Nakamura, Kinya*; Nakajima, Kunihisa; Iwai, Takashi; Arai, Yasuo
Denryoku Chuo Kenkyusho Hokoku (L05010), 13 Pages, 2006/07
no abstracts in English
Nakamura, Kinya*; Kato, Tetsuya*; Iwai, Takashi; Arai, Yasuo
Denryoku Chuo Kenkyusho Hokoku (L05011), 14 Pages, 2006/07
no abstracts in English
Osawa, Akira*; Kakurai, Kazuhisa; Nishiwaki, Yoichi*; Kato, Tetsuya*
Journal of the Physical Society of Japan, 75(7), p.074719_1 - 074719_4, 2006/07
Times Cited Count：6 Percentile：41.83(Physics, Multidisciplinary)Polarized neutron inelastic scattering experiments have been carried out in the quasi-1D Ising-like antiferromagnet TlCoCl. We observed the longitudinal magnetic fluctuation S
(Q,
) for the spin-wave excitation continuum for the first time, together with the transverse magnetic fluctuation S
(Q,). We compared both obtained intensities of S(Q,) and S(Q,) with the predictions of the perturbation theory from the pure Ising limit by Ishimura and Shiba.
Nishiwaki, Yoichi*; Kato, Tetsuya*; Ohara, Yasuaki*; Osawa, Akira*; Todoroki, Norikazu*; Igawa, Naoki; Ishii, Yoshinobu; Iio, Katsunori*
Journal of the Physical Society of Japan, 75(3), p.034707_1 - 034707_8, 2006/03
Times Cited Count：12 Percentile：58.26(Physics, Multidisciplinary)no abstracts in English
Osawa, Akira*; Nishiwaki, Yoichi*; Kato, Tetsuya*; Kakurai, Kazuhisa
Journal of the Physical Society of Japan, 75(1), p.015002_1 - 015002_2, 2006/01
Times Cited Count：8 Percentile：48.9(Physics, Multidisciplinary)no abstracts in English
Kato, Tetsuya*; Iizuka, Masatoshi*; Inoue, Tadashi*; Iwai, Takashi; Arai, Yasuo
Journal of Nuclear Materials, 340(2-3), p.259 - 265, 2005/04
Times Cited Count：23 Percentile：81.17(Materials Science, Multidisciplinary)no abstracts in English
Shirai, Osamu; Kato, Tetsuya*; Iwai, Takashi; Arai, Yasuo; Yamashita, Toshiyuki
Journal of Physics and Chemistry of Solids, 66(2-4), p.456 - 460, 2005/02
Times Cited Count：8 Percentile：37.11(Chemistry, Multidisciplinary)Electrochemical behaviors of PuN and (U, Pu)N in the LiCl-KCl eutectic melt containing UCl and PuCl at 773 K were investigated by cyclic voltammetry. The electrochemical dissolution of PuN and (U, Pu)N began nearly at -1.0 V vs. the Ag/AgCl reference electrode. The rest potentials of PuN and (U, Pu)N were observed at about 0.15 V more negative potential than that of UN since the equilibrium potential of UN is about 0.15 V more positive than that of PuN. In the cyclic voltammogram measured by using (U, Pu)N as the working electrode, a steep rise of the positive current was observed at more positive potential than -0.4 V in analogy with the cyclic voltammogram measured by using UN as the working electrode. In addition, there were two anodic current waves in the voltammogram with (U, Pu)N, though the wave form was not clear. This indicates that UN and PuN would be dissolved independently irrespective of formation of the solid solution, (U, Pu)N.
Uozumi, Koichi*; Iizuka, Masatoshi*; Kato, Tetsuya*; Inoue, Tadashi*; Shirai, Osamu*; Iwai, Takashi; Arai, Yasuo
Journal of Nuclear Materials, 325(1), p.34 - 43, 2004/02
Times Cited Count：109 Percentile：98.55(Materials Science, Multidisciplinary)Experiments were conducted on simultaneous recovering of uranium and plutonium electrochemically into laboratory scale liquid cadomium cathodes(LCCs) at different U/Pu ratios in the salt phase. The influence of the salt composition on the recovered amount of uranium and plutonium, the morphology of uranium and plutonium in the LCCs, and the behavior of americium were examined. It was shouwn that there is a threshold in the U/Pu ratio in the salt phase for the successful simultaneous recovery of uranium and plutonium up to 10wt% in high current efficiencies.
Kato, Tetsuya*; Uozumi, Koichi*; Inoue, Tadashi*; Shirai, Osamu*; Iwai, Takashi; Arai, Yasuo
Proceedings of GLOBAL2003 Atoms for Prosperity; Updating Eisenhower's Global Vision for Nuclear Energy (CD-ROM), p.1591 - 1595, 2003/11
Electrolysis experiments were carried to recover plutonium and uranium into liquid cadmium cathodes from molten salt at high cathode current densities. In the electrolysis at 101mA/cm
, 10.4wt.% of heavy metals in the cathode was recovered at almost 100% of current efficiency. In the electrolysis at 156mA/cm, the cathode potential ascended after approximately 8wt.% of heavy metals was recovered and some deposit was observed outside of the crucible.
Osawa, Akira*; Kato, Tetsuya*; Tanaka, Hidekazu*; Kakurai, Kazuhisa; M
ller, M.*; Mikeska, H.-J.*
Physical Review B, 65(9), p.094426_1 - 094426_7, 2002/03
Times Cited Count：90 Percentile：93.54(Materials Science, Multidisciplinary)no abstracts in English
Yamashita, Toshiyuki; *; Tsuji, Toshihide*; Kato, Tetsuya*; *; Iwashita, Mitsushige*
Journal of Alloys and Compounds, 271-273, p.400 - 403, 1998/00
Times Cited Count：4 Percentile：39.22(Chemistry, Physical)no abstracts in English
