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Journal Articles

Flexible fuel cycle system for the effective management of plutonium

Fukasawa, Tetsuo*; Hoshino, Kuniyoshi*; Yamashita, Junichi*; Takano, Masahide

Journal of Nuclear Science and Technology, 57(11), p.1215 - 1222, 2020/11

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

The flexible fuel cycle initiative system (FFCI system) has been developed to reduce spent fuel (SF) amounts, to keep high availability factor for the reprocessing plant and to increase the proliferation resistance for the recovered Pu. The system separates most U from the SF at first, and the residual material called recycle material (RM) which contains Pu, minor actinides, fission products and remaining U will go to Pu(+U) recovery from the RM for Pu utilizing reactor in future. The Pu utilizing reactor is FBR or LWR with MOX fuel. The RM is the buffer material between SF reprocessing and Pu utilizing reactor with compact size and high proliferation resistance, which can suppress the amount of relatively pure Pu. The innovative technologies of FFCI are most U separation and temporary RM storage. They are investigated by the literature survey, fundamental experiments using simulated material and analyses using simulation code. This paper summarizes the feasibility confirmation results of FFCI.

Journal Articles

Role of residual transition-metal atoms in oxygen reduction reaction in cobalt phthalocyanine-based carbon cathode catalysts for polymer electrolyte fuel cell

Kobayashi, Masaki*; Niwa, Hideharu*; Harada, Yoshihisa*; Horiba, Koji*; Oshima, Masaharu*; Ofuchi, Hironori*; Terakura, Kiyoyuki*; Ikeda, Takashi; Koshigoe, Yuka*; Ozaki, Junichi*; et al.

Journal of Power Sources, 196(20), p.8346 - 8351, 2011/10

 Times Cited Count:32 Percentile:70.76(Chemistry, Physical)

The electronic structure of Co atoms in CoPc-based carbon catalysts, which were prepared by pyrolyzing a mixture of CoPc and phenol resin polymer up to 1000$$^circ$$C, has been investigated using XAFS analysis and HXPES. The Co K XAFS spectra show that most of the Co atoms are in the metallic state and small quantities of oxidized Co components are present in the samples even after acid washing to remove Co atoms. Based on the difference in probing depth between XAFS and HXPES, it was found that after acid washing, the surface region with the aggregated Co clusters is primarily composed of metallic Co. Since the electrochemical properties remain almost unchanged even after the acid washing process, the residual metallic and oxidized Co atoms themselves will hardly contribute to the ORR activity of the CoPc-based carbon cathode catalysts, implying that the active sites of the CoPc-based catalysts primarily consist of light elements such as C and N.

Journal Articles

X-ray photoemission spectroscopy analysis of N-containing carbon-based cathode catalysts for polymer electrolyte fuel cells

Niwa, Hideharu*; Kobayashi, Masaki*; Horiba, Koji*; Harada, Yoshihisa*; Oshima, Masaharu*; Terakura, Kiyoyuki*; Ikeda, Takashi; Koshigoe, Yuka*; Ozaki, Junichi*; Miyata, Seizo*; et al.

Journal of Power Sources, 196(3), p.1006 - 1011, 2011/02

 Times Cited Count:80 Percentile:92(Chemistry, Physical)

We report on the electronic structure of three different types of N-containing carbon-based cathode catalysts for polymer electrolyte fuel cells observed by hard X-ray photoemission spectroscopy. C 1s spectra show the importance of $$sp^{2}$$ carbon network formation for the oxygen reduction reaction (ORR) activity. Samples having high oxygen reduction reaction activity in terms of oxygen reduction potential contain high concentration of graphite-like nitrogen. Based on a quantitative analysis of our results, the oxygen reduction reaction activity of the carbon-based cathode catalysts will be improved by increasing concentration of graphite-like nitrogen in a developed $$sp^{2}$$ carbon network.

Journal Articles

Study of oxygen ion diffusion in (Ba$$_{0.5}$$Sr$$_{0.5}$$)(Co$$_{0.8}$$Fe$$_{0.2}$$)O$$_{2.33-delta}$$ through ${it in-situ}$ neutron diffractions at 300 and 720 K

Ito, Takanori*; Hirai, Takene*; Yamashita, Junichi*; Watanabe, Shoji*; Kawata, Etsuya*; Kitamura, Naoto*; Idemoto, Yasushi*; Igawa, Naoki

Physica B; Condensed Matter, 405(8), p.2091 - 2096, 2010/04

 Times Cited Count:13 Percentile:53.76(Physics, Condensed Matter)

We analyze the mechanism of oxygen ion diffusion in (Ba$$_{0.5}$$Sr$$_{0.5}$$)(Co$$_{0.8}$$Fe$$_{0.2}$$)O$$_{2.33-delta}$$ by using the Rietveld refinement, the maximum entropy method (MEM) analysis, and MEM-based pattern fitting (MPF) with ${it in-situ}$ neutron diffractions at 300 and 720 K. We speculate that when $$U$$$$_{rm aniso}$$ and neutron scattering density of O1(4${it c}$) site with a large number of vacancies metamorphose into that with anisotropy directed toward the O1(4${it c}$) and O2(8${it d}$) sites at 720 K, the oxygen ions diffuse along the paths between O1(4${it c}$) and O1(4${it c}$), and O1(4${it c}$) and O2(8${it d}$).

Journal Articles

Flexible fuel cycle R&D for the smooth FBR deployment

Fukasawa, Tetsuo*; Yamashita, Junichi*; Hoshino, Kuniyoshi*; Sasahira, Akira*; Inoue, Tadashi*; Minato, Kazuo; Sato, Seichi*

Proceedings of 16th Pacific Basin Nuclear Conference (PBNC-16) (CD-ROM), 6 Pages, 2008/10

Transition period from light water reactors (LWR) to fast breeder reactors (FBR) is quite important to achieve the future FBR cycle system. The transition scenarios were carefully studied and the Flexible Fuel Cycle Initiative (FFCI) was proposed in this study. FFCI carries out about 90% uranium (U) removal from LWR spent fuels (SF) at first and then recovers plutonium/uranium (Pu/U) from the remaining SF named "recycle material"(RM) (about 40% U, 15% Pu and 45% other nuclides) for FBR fresh fuel fabrication according to the FBR deployment status. The FFCI has some merits compared with ordinary system that carries out full reprocessing of LWR SF, that is volume reduction of LWR SF by its conversion to RM (proliferation resistant material), and storage and supply of high Pu density RM according to FBR deployment rate changes.

Journal Articles

Uranium recovery in LWR reprocessing and plutonium/residual uranium conditioning in FBR reprocessing for the transition from LWR to FBR

Fukasawa, Tetsuo*; Yamashita, Junichi*; Hoshino, Kuniyoshi*; Sasahira, Akira*; Inoue, Tadashi*; Minato, Kazuo; Sato, Seichi*

Proceedings of 3rd International ATALANTE Conference (ATALANTE 2008) (CD-ROM), 7 Pages, 2008/05

In order to flexibly manage the transition period from LWR to FBR, the authors investigated the transition scenario and proposed the Flexible Fuel Cycle Initiative (FFCI). In FFCI, LWR spent fuel reprocessing only carries out the removal of about 90% uranium that will be purified and utilized in LWR after re-enrichment. The residual material (40% U, 15% Pu and 45% other nuclides) is transferred to temporary storage and/or FBR spent fuel reprocessing to recover Pu/U followed by FBR fresh fuel fabrication depending on the FBR introduction status. The FFCI has some merits compared with ordinary system that consists of full reprocessing facilities for both LWR and FBR spent fuels, that is smaller LWR reprocessing facility, spent LWR fuel reduction, storage and supply of high proliferation resistant and high Pu density material that can flexibly respond to FBR introduction rate changes. The Pu balance was calculated under several cases, which revealed that the FFCI could supply enough Pu to FBR in any cases.

Journal Articles

Synchrotron radiation study on structure of atmospheric corrosion products formed on steel surfaces

Konishi, Hiroyuki; Yamashita, Masato*; Mizuki, Junichiro; Uchida, Hitoshi*

Characterization of Corrosion Products on Steel Surfaces, p.199 - 222, 2006/00

no abstracts in English

Journal Articles

X-ray absorption fine structure spectra of rust layers on Fe-based binary alloys exposed to Cl-rich environment

Konishi, Hiroyuki; Yamashita, Masato*; Uchida, Hitoshi*; Mizuki, Junichiro

Proceedings of 16th International Corrosion Congress (CD-ROM), 6 Pages, 2005/09

XANES measurements of rust layers formed on Fe, Fe-Cr alloys and Fe-Ni alloys exposed to a Cl-rich atmosphere have been performed using synchrotron radiation in order to clarify the relation between the structural properties of the rust layer on weathering steel and anticorrosive alloying elements and/or chloride ions. The XANES spectra around Cl K-edge revealed that the rust layer on the Fe-based binary alloys contains unidentified chloride in addition to akagan$'e$iteite. The Fe K-edge XANES results indicated that the rust layers are composed mainly of well-known iron oxides, goethite, akagan$'e$ite, lepidocrocite and magnetite. In particular, the mole ratio of akagan$'e$ite in the rust layers on the Fe-Ni alloys is relatively higher than that of the Fe-Cr alloys. The Cr K-edge XANES spectra of the rust layers on the Fe-Cr alloys depends on the Cr alloy content. Therefore, the local structure of Cr in the rust layer is variable with the Cr density. In contrast, the Ni K-edge XANES results show that the local structure of Ni in the rust layer are unique in a certain Ni content range.

Journal Articles

Characterization of rust layer formed on Fe, Fe-Ni and Fe-Cr alloys exposed to Cl-rich environment by Cl and Fe K-edge XANES measurements

Konishi, Hiroyuki; Yamashita, Masato*; Uchida, Hitoshi*; Mizuki, Junichiro

Materials Transactions, 46(2), p.329 - 336, 2005/02

 Times Cited Count:26 Percentile:81.12(Materials Science, Multidisciplinary)

Chloride in atmosphere considerably reduces the corrosion resistance of conventional weathering steel containing a small amount of Cr. Ni is an effective anticorrosive element for improving the corrosion resistance of steel in a Cl-rich environment. In order to clarify the structure of the protective rust layer of weathering steel, Cl and Fe K-edge X-ray absorption near edge structure (XANES) spectra of atmospheric corrosion products (rust) formed on Fe, Fe-Ni and Fe-Cr alloys exposed to Cl-rich atmosphere were measured. The Fe K-XANES measurements enable the characterization of a mixture of iron oxides such as rust. The chemical composition of the rust was determined by performing pattern fitting of the measured spectra. All the rust is composed mainly of goethite, akagan$'e$ite, lepidocrocite and magnetite. Among these iron oxides, akagan$'e$ite in particular is the major component in the rust. Additionally, the amount of akagan$'e$ite in the rust of Fe-Ni alloy is much greater than that in rust of Fe-Cr alloy. Akagan$'e$ite is generally considered to facilitate the corrosion of steel, but our results indicate that akagan$'e$ite in the rust of Fe-Ni alloy is quantitatively different from that in rust of Fe-Cr alloy and does not facilitate the corrosion of steel. The shoulder peak observed in Cl K-XANES spectra reveals that the rust contains a chloride other than akagan$'e$ite. The energy of the shoulder peak does not correspond to that of any well-known chlorides. In the measured spectra, there is no proof that Cl, by combining with the alloying element, inhibits the alloying element from acting in corrosion resistance. The shoulder peak appears only when the content of the alloying element is lower than a certain value. This suggests that the generation of the unidentified chloride is related to the corrosion rate of steel.

Journal Articles

Structure analysis of cation selective Cr-goethite as protective rust of weathering steel

Konishi, Hiroyuki; Yamashita, Masato*; Uchida, Hitoshi*; Mizuki, Junichiro

Materials Transactions, 46(2), p.337 - 341, 2005/02

 Times Cited Count:8 Percentile:56.93(Materials Science, Multidisciplinary)

We have performed extended X-ray absorption fine structure (EXAFS) analysis for artificial Cr-goethite to elucidate the local structure around Cr in Cr-goethite. The spectra were obtained using synchrotron radiation X-rays at the Photon Factory in Tsukuba. The first shell contributions were isolated by Fourier filtering the EXAFS data, and the inverse Fourier transformed single-shell data were analyzed using curve fitting method. The results show that Cr is coordinated with (7$$pm$$1) O$$^{2-}$$ ions. The protective character of Cr-goethite protective rust layer on weathering steel can be interpreted in terms of the O$$^{2-}$$ coordination around Cr$$^{3+}$$ resulting in creation of negative fixed-charge in the Cr-goethite particles.

Journal Articles

Difference between Cr and Ni K-edge XANES spectra of rust layers formed on Fe-based binary alloys exposed to Cl-rich environment

Konishi, Hiroyuki; Yamashita, Masato*; Uchida, Hitoshi*; Mizuki, Junichiro

Materials Transactions, 46(1), p.136 - 139, 2005/01

 Times Cited Count:2 Percentile:27.24(Materials Science, Multidisciplinary)

The rust layer formed on weathering steel possesses a strong protective ability against corrosives in an atmosphere. This ability is related to the structure of the rust layer. The difference in the protective ability of a rust layer in a Cl-rich environment between conventional weathering steel containing Cr and advanced weathering steel containing Ni is believed to be caused by the differences in local structural and chemical properties between alloying elements, Cr and Ni, in the rust layer. In order to examine the effect of these alloying elements on the structure of the rust layer formed on steel in a Cl-rich environment, we have performed Cr and Ni K-edge X-ray absorption near-edge structure (XANES) measurements for the rust layer of Fe-Cr and Fe-Ni binary alloys exposed to a Cl-rich atmosphere using synchrotron radiation. The results of the Cr K-edge XANES measurements for the rust layer of Fe-Cr binary alloys show that the atomic geometry around Cr depends on the concentration of Cr. Therefore, it is expected that the local structure around Cr in the rust layer is unstable. On the other hand, from the results of the Ni K-edge XANES measurements for the rust layer of Fe-Ni binary alloys, Ni is considered to be positioned at a specific site in the crystal structure of a constituent of the rust layer, such as akagan$'e$ite or magnetite. As a consequence, Ni negligibly interacts with Cl$$^{-}$$ ions in the rust layer.

Journal Articles

Cl K-edge XANES spectra of atmospheric rust on Fe, Fe-Cr and Fe-Ni alloys exposed to saline environment

Konishi, Hiroyuki; Yamashita, Masato*; Uchida, Hitoshi*; Mizuki, Junichiro

Materials Transactions, 45(12), p.3356 - 3359, 2004/12

 Times Cited Count:9 Percentile:52.63(Materials Science, Multidisciplinary)

Cl K-edge XANES measurements of atmospheric corrosion products (rust) formed on Fe, Fe-Ni and Fe-Cr alloys in chloride pollution have been performed using synchrotron radiation in order to clarify roles of anticorrosive alloying elements and of Cl in the corrosion resistance of weathering steel. The spectra of binary alloys show a shoulder structure near the absorption edge. The intensity of the shoulder peak depends on the kind and amount of the alloying element, whereas the energy position is invariant. This indicates that Cl is not combined directly with alloying elements in the rust.

Journal Articles

First test results for the ITER central solenoid model coil

Kato, Takashi; Tsuji, Hiroshi; Ando, Toshinari; Takahashi, Yoshikazu; Nakajima, Hideo; Sugimoto, Makoto; Isono, Takaaki; Koizumi, Norikiyo; Kawano, Katsumi; Oshikiri, Masayuki*; et al.

Fusion Engineering and Design, 56-57, p.59 - 70, 2001/10

 Times Cited Count:17 Percentile:76.5(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Structural analysis of corrosion product of Fe-Cr alloy film using synchrotron radiation

Yamashita, Masato*; Konishi, Hiroyuki; Takahashi, Masamitsu; Mizuki, Junichiro; Uchida, Hitoshi*

Materials Science Research International, Special Technical Publication, 1, p.398 - 401, 2001/05

A rust layer on a weathering low-alloy steel has strong protective ability for atmospheric corrosion of the steel. In order to control the rust layer on steels, it is so important to know the detailed structure of rust and relate it to the protective ability of the rust layer. Especially, the position of atoms of the alloying elements in the rust layer directly control the structure and properties of the rust layer. We tried to find the atomic arrangement of the rust layer of Fe-Cr alloy film covered with thin film of electrolyte using synchrotron radiation. Grazing incidence X-ray diffraction and M$"o$ssbauer spectra showed that the rust layer was composed of $$gamma$$-FeOOH and ultra-fine $$alpha$$-FeOOH. By examining EXAFS spectra, Cr coming from Fe-Cr alloy film would be present in the $$alpha$$-FeOOH. Some of Cr would be present between Fe-0-OH octahedron as interstitial atoms, as well as substituting Fe lattice site in the octahedron.

Journal Articles

Progress of the ITER central solenoid model coil programme

Tsuji, Hiroshi; Okuno, Kiyoshi*; Thome, R.*; Salpietro, E.*; Egorov, S. A.*; Martovetsky, N.*; Ricci, M.*; Zanino, R.*; Zahn, G.*; Martinez, A.*; et al.

Nuclear Fusion, 41(5), p.645 - 651, 2001/05

 Times Cited Count:55 Percentile:84.47(Physics, Fluids & Plasmas)

no abstracts in English

Oral presentation

Development of flexible fuel cycle initiative, 1; General concept

Yamashita, Junichi*; Fukasawa, Tetsuo*; Kawamura, Fumio*; Hoshino, Kuniyoshi*; Sasahira, Akira*; Sato, Seichi*; Minato, Kazuo

no journal, , 

no abstracts in English

Oral presentation

Development of flexible fuel cycle initiative, 3; Uranium removal

Yamashita, Junichi*; Fukasawa, Tetsuo*; Kawamura, Fumio*; Hoshino, Kuniyoshi*; Sasahira, Akira*; Minato, Kazuo; Akabori, Mitsuo; Arai, Yasuo

no journal, , 

no abstracts in English

Oral presentation

Post irradiation examination on particle dispersed Uranium Rock-like Oxide (U-ROX) fuel, 3; Ceramographic examination

Shirasu, Noriko; Kuramoto, Kenichi*; Yamashita, Toshiyuki; Honda, Junichi; Hatakeyama, Yuichi; Ichise, Kenichi

no journal, , 

no abstracts in English

Oral presentation

In situ observation of corrosion process on steels using XAFS technique

Komori, Daisuke*; Yamashita, Masato*; Konishi, Hiroyuki; Hanaki, Satoshi*; Uchida, Hitoshi*; Mizuki, Junichiro

no journal, , 

no abstracts in English

Oral presentation

Flexible fuel cycle initiative

Yamashita, Junichi*; Fukasawa, Tetsuo*; Kawamura, Fumio*; Hoshino, Kuniyoshi*; Sasahira, Akira*; Sato, Seichi*; Minato, Kazuo

no journal, , 

no abstracts in English

23 (Records 1-20 displayed on this page)