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Journal Articles

Nuclear energy and waste management; Pyroprocess for system symbiosis

Ogawa, Toru; Minato, Kazuo; Okamoto, Yoshihiro; Nishihara, Kenji

Journal of Nuclear Materials, 360(1), p.12 - 15, 2007/01

 Times Cited Count:13 Percentile:28.09(Materials Science, Multidisciplinary)

The actinide management has become a key issue in nuclear energy due to increasing proliferation concern and long-term environmental perception. The better way of waste management will be made by system symbiosis: a combination of light-water reactor and fast reactor and/or accelerator-driven transmutation system should be sought. The new recycling technology should be able to achieve good economy with smaller plants, which can process fuels from different types of reactors on a common technical basis. Pyroprocess with the use of molten salts is regarded as the strong candidate for such recycling technology. In JAEA, the first laboratory for the high temperature chemistry of transuranium elements, mainly Am and Cm, has been established. The fundamental data on the molten-salt chemistry of transuranium oxides and nitrides will be combined with the computer code for predicting the molten-salts electrolytic processes.

Journal Articles

Electrochemical behavior of actinides and actinide nitrides in LiCl-KCl eutectic melts

Shirai, Osamu*; Yamana, Hajimu*; Arai, Yasuo

Journal of Alloys and Compounds, 408-412, p.1267 - 1273, 2006/02

 Times Cited Count:33 Percentile:14.07(Chemistry, Physical)

no abstracts in English

Journal Articles

Mixing behavior of molten PbCl$$_2$$ with alkali chlorides

Okamoto, Yoshihiro; Yaita, Tsuyoshi; Minato, Kazuo

Denki Kagaku Oyobi Kogyo Butsuri Kagaku, 73(8), p.745 - 747, 2005/08

The structural change of molten PbCl$$_2$$ by mixing with alkali chlorides was investigated by Pb L$$_3$$-edge XAFS measurements. By the mixing, the nearest neighbor Pb-Cl distance and its coordination number increased, while the Debye-Waller factor and the 3rd cumulant decreased. It is concluded that the coordination structure (PbCl$$_6$$)$$^{4-}$$ is enhanced by the mixing with alkali chlorides.

Journal Articles

Molecular to ionic transition of BiCl$$_3$$ in LiCl-KCl eutectic melt

Okamoto, Yoshihiro; Yaita, Tsuyoshi; Minato, Kazuo

Journal of Molecular Structure, 749(1-3), p.70 - 73, 2005/07

 Times Cited Count:3 Percentile:91.3(Chemistry, Physical)

The local structures of molten BiCl$$_3$$ and its mixtures in LiCl-KCl eutectic melt were investigated by X-ray absorption fine structure (XAFS) technique. The 1st Bi-Cl correlation in molten pure BiCl$$_3$$ shows covalent nature, since the distance was almost the same as sum of covalent radii of Bi and Cl and the coordination number was almost 3. The similar property was observed also in the mixture of 75% BiCl$$_3$$ with LiCl-KCl eutectic melt. Drastic change was detected in 25% BiCl$$_3$$ mixture melt. The 1st Bi-Cl distance was sum of ionic radii in molten 25% BiCl$$_3$$ melt. The results suggest that BiCl$$_3$$ changes from molecular liquid to ionic by mixing with alkali chlorides.

Journal Articles

X-ray structural analysis of molten PbCl$$_2$$

Okamoto, Yoshihiro; Iwadate, Yasuhiko*; Fukushima, Kazuko*; Matsuura, Haruaki*; Minato, Kazuo

Journal of Physics and Chemistry of Solids, 66(2-4), p.452 - 455, 2005/02

 Times Cited Count:6 Percentile:66.78(Chemistry, Multidisciplinary)

The structure of molten PbCl$$_2$$ was investigated by using X-ray diffrtaction(XRD) and X-ray absorption fine structure(XAFS) analysis techniques. From the fourier transformation analysis if the XRD data, the nearest Pb$$^{2+}$$-Cl$$^-$$ interaction consists of two kinds of interactions; rigid 4-fold tetrahedron and 2-3 loose coordination. The XAFS result shows a local structure is the 4-fold coordination in the melt.

Journal Articles

Structural study of molten lanthanum halides by X-ray diffraction and computer simulation techniques

Okamoto, Yoshihiro; Madden, P. A.*

Journal of Physics and Chemistry of Solids, 66(1), p.448 - 451, 2005/01

The local structure of molten LaCl$$_3$$ has been characterized by the octahedral coordination (LaCl$$_6$$)$$^{3-}$$. It is based on X-ray diffraction (XRD) and Raman spectroscopy results. On the other hand, a different structural image was proposed in the neutron diffraction (ND) and the molecular dynamics (MD) studies. These ND and MD works concluded that a coordination behavior changes with cation size in molten rare earth trichlorides. Thus, they reported the coordination number of Cl$$^-$$ ions around La$$^{3+}$$ ion is 8.2 in the ND work and 7.9 in the MD work. In the present work, XRD measurements of molten LaCl$$_3$$ were performed to investigate the local structure. The coordination number of the 1st La$$^{3+}$$-Cl$$^-$$ pair in molten LaCl$$_3$$ was 7.1 from analysis of the correlation function G(r). The structural change by increasing anion size was examined by the XRD measurement of molten LaBr$$_3$$. The XRD data were nicely reproduced by the MD simulations with polarizable ionic model.

Journal Articles

Electroplating of the superconductive boride MgB$$_{2}$$ from molten salts

Abe, Hideki*; Yoshii, Kenji; Nishida, Kenji*; Imai, Motoharu*; Kitazawa, Hideaki*

Journal of Physics and Chemistry of Solids, 66(1), p.406 - 409, 2005/01

no abstracts in English

Journal Articles

Local structure of molten CdCl$$_2$$ systems

Okamoto, Yoshihiro; Shiwaku, Hideaki; Yaita, Tsuyoshi; Suzuki, Shinichi; Minato, Kazuo; Tanida, Hajime*

Zeitschrift f$"u$r Naturforschung, A, 59a(11), p.819 - 824, 2004/11

The local structure of molten CdCl$$_2$$ and CdCl$$_2$$-KCl mixture was investigated by high-temperature XAFS technique. The nearest Cd-Cl distance decreases by melting. Similarly, the coordination number decreases from 6 to 4. It suggests that there is (CdCl$$_4$$)$$^{2-}$$ tetrahedral complex ion in the melt. It is concluded that the local structure is kept also in the mixture melt, since the same XAFS result as the pure melt was obtained.

Journal Articles

XAFS simulation of highly disordered materials

Okamoto, Yoshihiro

Nuclear Instruments and Methods in Physics Research A, 526(3), p.572 - 583, 2004/07

 Times Cited Count:25 Percentile:14.04(Instruments & Instrumentation)

The XAFS functions for highly-disordered materials such as molten salts were simulated by using output data of molecular dynamics calculation. The atomic configuration data obtained from the MD results was directly used as input data in the XAFS simulation code FEFF8. It was assumed that Debye-Waller factor and anharmonic vibration effect could be substituted by an accumulation of the FEFF8 calculations using many atomic configurations. The experimental XAFS functions for platinum, solid and molten salt systems were nicely reproduced by the FEFF8 calculations with 10000-50000 atomic configurations.

JAEA Reports

Proceedings of the 3rd Workshop on Molten Salts Technology and Computer Simulation

Okamoto, Yoshihiro; Minato, Kazuo

JAERI-Conf 2004-008, 228 Pages, 2004/04

JAERI-Conf-2004-008.pdf:17.05MB

Applications of molten salts technology to separation and synthesis of materials have a potential to give us a civilized life, for example aluminium refinement. Recently, much attention is given to the pyrochemical reprocessing of spent nuclear fuels in the molten salt research field. On the other hand, computer simulation technique is expected to play an important role for supporting experimental works and predicting unknown physical properties in the molten salts application studies. Research group for Actinides Science, Department of Materials Science, Japan Atomic Energy Research Institute(JAERI), together with Reprocessing and Recycle Technology Division, Atomic Energy Society of Japan, organized the 3rd Workshop on Molten Salts Technology and Computer Simulation at Tokai Research Establishment, JAERI on December 16, 2003. Many molten salts researchers in Japan participated in the workshop and many useful presentations and discussions were performed.

Journal Articles

High-temperature XAFS study of solid and molten SrCl$$_2$$

Okamoto, Yoshihiro; Yaita, Tsuyoshi; Minato, Kazuo

Journal of Non-Crystalline Solids, 333(2), p.182 - 186, 2004/02

 Times Cited Count:6 Percentile:41.06(Materials Science, Ceramics)

The local structure of solid and molten SrCl$$_2$$ was investigated by X-ray absorption fine structure(XAFS) technique. A superionic conduction state was observed below the melting point. The XAFS data at molten state was obtained at 1000$$^{circ}$$C. According to the curve fitting analysis, the nearest Sr$$^{2+}$$-Cl$$^-$$ distance and the coordination number are 2.99${AA }$ and 6.6 in molten state. XAFS functions calculated from molecular dynamics simulation results were copmpared with the experimental XAFS data.

Journal Articles

Recovery of alkali salt by supercritical fluid leaching method using carbon dioxide

Watanabe, Takeshi*; Tsushima, Satoru*; Yamamoto, Ichiro*; Tomioka, Osamu; Meguro, Yoshihiro; Nakashima, Mikio; Wada, Ryutaro*; Nagase, Yoshiyuki*; Fukuzato, Ryuichi*

Proceedings of 2nd International Symposium on Supercritical Fluid Technology for Energy and Environment Applications (Super Green 2003), p.363 - 366, 2004/00

Recovery of salts by supercritical fluid leaching (SFL) method using carbon dioxide was experimentally studied. It was confirmed that LiCl was recovered with a mixed fluid of carbon dioxide and methanol, and KCl and SrCl$$_2$$ were recovered with a mixed fluid of carbon dioxide, methanol and crown ether. The influence of crown ether for KCl and SrCl$$_2$$ extraction were found to increase in the order of 15-crown-5 (15C5) $$<$$ 18-crown-6 (18C6) $$<$$ dicychlohexyl-18-crown-6 (DC18C6). It is expected that other salts can be recovered selectively with a mixed fluid of carbon dioxide, methanol and suitable crown ether.

Journal Articles

Compatibility test between molten salts for high temperature heat storage and alloys

Shiina, Yasuaki; Kuriki, Yoshiro*

Nippon Genshiryoku Gakkai Wabun Rombunshi, 2(3), p.375 - 378, 2003/09

no abstracts in English

JAEA Reports

Compatibility tests between molten salts and metal materials, 2

Shiina, Yasuaki; Kuriki, Yoshiro*

JAERI-Tech 2003-070, 47 Pages, 2003/08

JAERI-Tech-2003-070.pdf:14.83MB

no abstracts in English

JAEA Reports

Proceedings of the 2nd Workshop on Molten Salts Technology and Computer Simulation

Okamoto, Yoshihiro; Minato, Kazuo

JAERI-Conf 2003-005, 186 Pages, 2003/06

JAERI-Conf-2003-005.pdf:10.42MB

Applications of molten salts technology to separation and synthesis of materials have been widely studied. Especially, much attention is given to the pyrochemical reprocessing of spent nuclear fuels. Computer simulation technique is expected to play an important role for supporting experimental works and predicting unknown physical properties in the molten salts application studies. Research group for Actinides Science, Department of Materials Science, Japan Atomic Energy Research Institute (JAERI), together with Reprocessing and Recycle Technology Division, Atomic Energy Society of Japan, organized the 2nd Workshop on Molten Salts Technology and Computer Simulation at Tokai Research Establishment, JAERI on December 3, 2002. Many molten salts researchers in Japan participated in the workshop and many useful presentations and discussions were performed.

Journal Articles

Density of molten terbium chloride

Sato, Tadashi; Okamoto, Yoshihiro

Zeitschrift f$"u$r Naturforschung, A, 58a(2-3), p.183 - 185, 2003/02

Density of molten terbium chloride is first measured by gamma-ray attenuation method as a function of temnperature ranging from 993 to 1213K. Empirical equation for the density of the melt is found to be $$d=3.937{pm}0.028-(4.76{pm}0.25) {times} 10^{-4} (g/cm^3)$$.

Journal Articles

Structural analysis of 1-ethyl-3-methylimidazolium bifluoride melt

Matsumoto, Kazuhiko*; Hagiwara, Rika*; Ito, Yasuhiko*; Kohara, Shinji*; Suzuya, Kentaro

Nuclear Instruments and Methods in Physics Research B, 199, p.29 - 33, 2003/01

 Times Cited Count:32 Percentile:9.46

The structure of 1-ethyl-3-methylimidazolium bifluoride (EMImF$$cdot$$HF) melt has been analyzed at 333 K by a high-energy synchrotron X-ray diffraction method. The total correlation function of the EMImF$$cdot$$HF melt was similar to that of the solid state, indicating that not only the short-range but also the intermediate-range ordering in the solid are partially preserved in the liquid state. The intra-molecular F-F correlation in the anions clearly appears in the total correlation function of the EMImF$$cdot$$HF melt, whereas prominent peaks are not observed in the case of a room temperature molten salt, 1-ethyl-3-methylimidazolium fluorohydrogenate (EMImF$$cdot$$2.3HF).

Journal Articles

Pyrochemical reprocessing of nitride fuels

Shirai, Osamu*; Yamana, Hajimu*; Iwai, Takashi; Arai, Yasuo

Proceedings of Nuclear Fuel Cycle Technologies Closing the Fuel Cycle (CD-ROM), 7 Pages, 2003/00

no abstracts in English

Journal Articles

X-ray absorption study of molten uranium chloride system

Okamoto, Yoshihiro; Akabori, Mitsuo; Ito, Akinori; Ogawa, Toru

Journal of Nuclear Science and Technology, 39(Suppl.3), p.638 - 641, 2002/11

We report local structural features of molten UCl$$_3$$ with LiCl-KCl eutectic probed by the U L$$_3$$-edge XAFS(X-ray absorption fine structure). The XAFS measurements were performed in a transmission mode at the BL27B station of the Photon Factory(High Energy Accelerator Organization, Tsukuba, JAPAN). Sample prepared by chlorination of uranium hydride and then reduction with zinc powder was sealed in a quartz cell under reduced pressure. The nearest U$$^{3+}$$-Cl$$^-$$ distance and the coordination number of Cl$$^-$$ around U$$^{3+}$$ ion were obtained by a curve fitting of the 1st shell XAFS function k$$^3$$$$chi$$(k). The pair potential in the U$$^{3+}$$-Cl$$^-$$ correlation was evaluated from XAFS simulation by combinational use of the MD and the FEFF8. In addition, valence state of uranium in the melt was evaluated by XANES(X-ray absorption near edge structure) spectra.

Journal Articles

XAFS study of molten zinc dibromide

Okamoto, Yoshihiro; Fukushima, Kazuko*; Iwadate, Yasuhiko*

Journal of Non-Crystalline Solids, 312(314), p.450 - 453, 2002/10

Local structure of molten ZnBr$$_2$$ was investigated by both of the Zn and the Br XAFS(X-ray absorption fine structure) measurements above their K-absorption edge at 723K. The nearest Zn$$^{2+}$$-Br$$^-$$ distance was determined to be 2.46$AA  for the Zn XAFS and 2.45AA for the Br XAFS.  The coordination number of Br$^-$$ ion around Zn$$^{2+}$$ was about 4. On the other hand, that of Zn$$^{2+}$$ ion around Br$$^-$$ was about 2. The 1st Br$$^-$$-Br$$^-$$ distance was estimated to be 3.9$AA.  They shows that a tetrahedral coordinate (ZnBr$_4$$)$$^{2-}$$ exists and most of the coordinate connects with the next ones through Br$$^-$$ ion. The two XAFS functions in the molten ZnBr$$_2$$ were reproduced by the combination of the molecular dynamics(MD) simulation and the FEFF7 computations.

86 (Records 1-20 displayed on this page)