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O
and AmO with XAFS spectroscopyNishi, Tsuyoshi; Nakada, Masami; Suzuki, Chikashi; Shibata, Hiroki; Ito, Akinori; Akabori, Mitsuo; Hirata, Masaru
Journal of Nuclear Materials, 401(1-3), p.138 - 142, 2010/06
Times Cited Count：29 Percentile：86.57(Materials Science, Multidisciplinary)XAFS studies were performed in a study of americium sesquioxide (AmO) with A-type rare earth oxide structure and americium dioxide (AmO) with fluorite structure. EXAFS results for Am-L absorption edge of AmO and AmO were good agreement with the crystallographic data from X-ray diffraction analysis. In order to characterize XANES in aspect of the electronic states, the theoretical assignments for the AmO and AmO were performed with the all-electron full potential linearized augmented plane wave (FP-LAPW) method. The theoretical XANES spectra of AmO and AmO well reproduced the experimental ones. In addition, it was found that the white line peak was created due to the interaction between Am-d and O-p components, and the broad peak and the tail peak were created due to the interaction between Am-d and O-d component.
Nishi, Tsuyoshi; Takano, Masahide; Ito, Akinori; Miyata, Seiichi; Akabori, Mitsuo; Arai, Yasuo; Minato, Kazuo
IOP Conference Series; Materials Science and Engineering, 9, p.012017_1 - 012017_8, 2010/05
Times Cited Count：2 Percentile：70.79(Chemistry, Inorganic & Nuclear)The thermal diffusivities and heat capacities of transuranium nitride solid solutions, (Np,Am)N and (Pu,Am)N, were measured by using a laser flash method and a drop calorimetry, respectively. The thermal conductivities of these samples were determined from the measured thermal diffusivities, heat capacities and bulk densities. The thermal conductivities of (Np,Am)N and (Pu,Am)N increased with temperature over the temperature range investigated. The increases in the thermal conductivities were probably due to the increase of electrical components. In addition, the thermal conductivities of (Np,Am)N and (Pu,Am)N decreased with increasing Am contents. It could be considered that the decreases in the thermal conductivities correspond to the lowering of electronic contribution.
Nishi, Tsuyoshi; Takano, Masahide; Ito, Akinori; Akabori, Mitsuo; Arai, Yasuo; Minato, Kazuo
Proceedings of 10th OECD/NEA Information Exchange Meeting on Actinide and Fission Product Partitioning and Transmutation (CD-ROM), 8 Pages, 2010/00
Neptunium nitride (NpN) and americium nitride (AmN) were prepared by carbothermic reduction of the respective dioxides. The thermal diffusivities of NpN and AmN were measured by using a laser flash method. The heat capacities of NpN and AmN were determined with the drop calorimetry. The thermal diffusivity of NpN tends to remain unchanged with increasing temperature in the temperature range from 473 to 1473 K, and that of AmN tends to slightly decrease with increasing temperature in the same temperature range. The heat capacity of NpN obtained was close to those of UN and PuN, while that of AmN was slightly smaller than those of UN, NpN and PuN. The thermal conductivities of NpN and AmN were determined from the measured thermal diffusivities, heat capacities and bulk densities. It was found that the thermal conductivities of NpN and AmN slightly increased with temperature in the temperature range investigated.
Abe, Hiroyoshi; Haga, Takahisa; Fukaya, Hiroyuki; Sonoda, Takashi; Sakazume, Yoshinori; Ito, Mitsuo; Shirahashi, Koichi
JAEA-Technology 2009-008, 24 Pages, 2009/03
JAEA-Technology-2009-008.pdf:5.62MB
Analysis of the uranyl nitrate solution fuel is carried out at the analytical laboratory of NUCEF (Nuclear Fuel Cycle Engineering Research Facility), which provides essential data for operation of STACY (Static Experiment Critical Facility), TRACY (Transient Experiment Critical Facility) and the fuel treatment system. Analyzed in FY 2007 were uranyl nitrate solution fuel samples taken before and after experiments of STACY and TRACY, samples for the preparation and pulification of uranyl nitrate solution fuel in the fuel treatment system and samples for nuclear material accountancy purpose. The total number of the samples analyzed in FY 2007 was 143. This report summarizes work related to the analysis and management of the analytical laboratory in the FY 2007.
Yoshida, Zenko; Watanabe, Kazuo; Ito, Mitsuo; Ueno, Takashi; Takeshita, Hidefumi
JAEA-Review 2008-062, 34 Pages, 2009/01
JAEA-Review-2008-062.pdf:4.07MB
Analytical methods for the spent nuclear fuel (SF) have been greatly innovated recently. This methodological innovation is mainly caused by rapid and remarkable progress of induced coupled plasma-mass spectrometry (ICP-MS) which is utilized for the isotopic analysis of actinoid elements (U, Np, Pu, Am, Cm) and fission product elements in the SF samples. The quantity of the objective element as well as the volume of the sample solution needed for the ICP-MS measurement are, in principle, much less than those required for the measurement by other analytical methods. ICP-MS makes it possible to reduce the radiation dose of the operator and to minimize the amount of the radioactive wastes generated from the analytical work. For the precise and accurate isotopic analysis of the objective element in the SF sample by mass spectrometry, the interfering element having isobars needs to be separated prior to the measurement. This review highlights the development of the separation methods and isotopic analysis methods for the analysis of the SF based on more than 50 recent publications and the future problems to be solved and prospects are discussed.
Nishi, Tsuyoshi; Ito, Akinori; Takano, Masahide; Numata, Masami; Akabori, Mitsuo; Arai, Yasuo; Minato, Kazuo
Journal of Nuclear Materials, 377(3), p.467 - 469, 2008/07
Times Cited Count：13 Percentile：61.64(Materials Science, Multidisciplinary)The specific heat capacities of NpN and AmN were determined by the drop calorimetry method. The NpN and AmN samples were prepared by the carbothermic reduction of the respective dioxides. The specific heat capacity of NpN obtained was in good agreement with the reported values in the temperature range from 334 to 1067 K, which was close to those of UN and PuN. The specific heat capacity of AmN was obtained experimentally for the first time, which was slightly smaller than those of UN, NpN and PuN in the temperature range from 354 to 1071 K.
Nishi, Tsuyoshi; Ito, Akinori; Takano, Masahide; Numata, Masami; Akabori, Mitsuo; Arai, Yasuo; Minato, Kazuo
Journal of Nuclear Materials, 376(1), p.78 - 82, 2008/05
Times Cited Count：33 Percentile：88.03(Materials Science, Multidisciplinary)The thermal diffusivity of neptunium dioxide was measured in the temperature range from 473 to 1473 K by a laser flash method. The thermal diffusivity slightly decreased with increasing temperature in the temperature range investigated. The specific heat capacity of NpO was measured in the temperature range from 334 to 1071 K by a drop calorimetry method. The specific heat capacity of NpO determined in this study was slightly larger than that of UO and about 7 % smaller than that of PuO. The thermal conductivity of NpO was determined from the thermal diffusivity, the specific heat capacity and the bulk density. It was found that the thermal conductivity of NpO from 873 to 1473 K existed between those of UO and PuO.
Nishi, Tsuyoshi; Ito, Akinori; Takano, Masahide; Akabori, Mitsuo; Arai, Yasuo; Minato, Kazuo
Proceedings of 3rd International ATALANTE Conference (ATALANTE 2008) (CD-ROM), 6 Pages, 2008/05
The thermal diffusivities of americium oxide and neptunium dioxide were determined by a laser flash method. It was found that the thermal diffusivities of AmO
and NpO decreased with increasing temperature. It was also found that the decrease in O/Am ratio during the thermal diffusivity measurements under vacuum resulted in a slight decrease in thermal diffusivity of AmO. The thermal conductivities of AmO and NpO were evaluated from the measured thermal diffusivities, heat capacities and bulk densities. The thermal conductivity of AmO was smaller than those of the literature values of UO and PuO. On the other hand, the thermal conductivity of NpO from 873 to 1473 K lay between those of UO and PuO. The thermal conductivities of AmO and NpO decreased with increasing temperature in the temperature range investigated.
Nishi, Tsuyoshi; Nakada, Masami; Ito, Akinori; Suzuki, Chikashi; Hirata, Masaru; Akabori, Mitsuo
Journal of Nuclear Materials, 374(3), p.339 - 343, 2008/03
Times Cited Count：20 Percentile：77.63(Materials Science, Multidisciplinary)EXAFS and XANES analysis were applied in a study of americium dioxide (AmO) with fluorite structure. EXAFS result for Am-L absorption edge of AmO was good agreement with the long-ranged structural data from X-ray diffraction analysis. In order to characterize XANES in aspect of the electronic structure, the theoretical assignment for the AmO was performed with the relativistic DV-X
molecular orbital method. The calculated XANES spectrum well reproduced the experimental spectrum. The theoretical assignment of the XANES spectra is very useful for the development of MA-MOX fuel for the future nuclear fuel cycle.
Sakazume, Yoshinori; Aoki, Hiromichi; Haga, Takahisa; Fukaya, Hiroyuki; Sonoda, Takashi; Shimizu, Kaori; Niitsuma, Yasushi*; Ito, Mitsuo; Inoue, Takeshi
JAEA-Technology 2007-069, 44 Pages, 2008/02
JAEA-Technology-2007-069.pdf:4.55MB
Analysis of the uranyl nitrate solution fuel is carried out at the analytical laboratory of NUCEF (Nuclear Fuel Cycle Engineering Research Facility), which provides essential data for operation of STACY (Static Experiment Critical Facility), TRACY (Transient Experiment Critical Facility) and the fuel treatment system. Analyzed in FY 2006 were uranyl nitrate solution fuel samples taken before and after experiments of STACY and TRACY, samples for the preparation of uranyl nitrate solution fuel, and samples for nuclear material accountancy purpose. The total number of the samples analyzed in FY 2006 was 254. This report summarizes work related to the analysis and management of the analytical laboratory in the FY 2006.
Nishi, Tsuyoshi; Takano, Masahide; Ito, Akinori; Akabori, Mitsuo; Arai, Yasuo; Minato, Kazuo; Numata, Masami
Journal of Nuclear Materials, 373(1-3), p.295 - 298, 2008/02
Times Cited Count：16 Percentile：70.66(Materials Science, Multidisciplinary)The thermal diffusivity of americium oxide was determined in the temperature range from 299 to 1473 K by a laser flash method. The thermal diffusivity of AmO decreased with increasing temperature. The thermal conductivity of AmO was estimated from the measured thermal diffusivity, the specific heat capacity and the bulk density. It was found that the thermal conductivity of AmO decreased with increasing temperature over the temperature range investigated. It was also found that the decrease in O/Am ratio during the thermal diffusivity measurements under vacuum resulted in a slight decrease in thermal conductivity of AmO.
Re by proton bombardment of enriched 
WIimura, Hideki; Horiguchi, Takayoshi*; Ishida, Yoshihisa*; Ito, Mitsuo; Koizumi, Mitsuo; Miyabe, Masabumi; Oba, Masaki
Journal of the Physical Society of Japan, 77(2), p.025004_1 - 025004_2, 2008/02
Times Cited Count：1 Percentile：11.65(Physics, Multidisciplinary)The nucleus Re is of interest from the astrophysical point of view, since production of this nucleus in stars could change an accuracy of nucleo-cosmochronometer. In order to calculate the neutron capture cross section theoretically, it is necessary to know the spin of nucleus. However, the spin of Re has not been established so far. In order to clarify the nuclear structure of this nucleus, we plan laser spectroscopy of Re, and first, we measured the production yield of the (
) reaction. The experiment was carried out by irradiating a W target with a proton beam from the JAEA tandem accelerator. Rhenium was chemically separated from the irradiated sample, and then 
-ray measurements were performed. As a result, we determined the production yield of the W()Re reaction for the first time and suggested the same spin for Re as the known spin of 
=8 for 
Re.
Nishi, Tsuyoshi; Takano, Masahide; Ito, Akinori; Akabori, Mitsuo; Minato, Kazuo; Kizaki, Minoru
Journal of Nuclear Materials, 355(1-3), p.114 - 118, 2006/09
Times Cited Count：20 Percentile：78.77(Materials Science, Multidisciplinary)The thermal diffusivity of AmN was measured from 373 to 1473 K by a laser flash method. The AmN sample was prepared from AmO by the carbothermic reduction. The obtained AmN product was grinded and pressed at about 400 MPa to form a disk. The disk was sintered at 1823 K for 10 hours in flowing N+4%H gas. The thermal diffusivity slightly decreased from 3.4
10
to 2.810 m
/s with increasing temperature. As the specific heat capacity of AmN was not available in literature, the thermal conductivity of AmN was tentatively estimated from the measured thermal diffusivity, bulk density and the specific heat capacity of PuN. It was found that the thermal conductivity of AmN slightly increased with temperature. The thermal conductivity of AmN corrected to 100%TD was found to be smaller than those of UN, NpN and PuN, whereas that of AmN was larger than those of UO and (U
Pu
)O.
Minato, Kazuo; Takano, Masahide; Nishi, Tsuyoshi; Ito, Akinori; Akabori, Mitsuo
Recent Advances in Actinide Science, p.317 - 322, 2006/06
To reduce the radiotoxicity of the high-level waste and to use the repository efficiently, recycling of minor actinides (MA: Np, Am, Cm) as well as plutonium is an option for the future nuclear fuel cycle. For MA-bearing fuel development, new facilities with inert atmosphere were installed and the thermal properties of minor actinide compounds, especially nitrides and oxides, were measured. Minor actinide nitrides were prepared by carbothermic reduction of the oxides. Lattice parameter and its thermal expansion were measured by high-temperature X-ray diffraction, and thermal diffusivity by laser flash method.
Nishi, Tsuyoshi; Takano, Masahide; Ito, Akinori; Akabori, Mitsuo; Minato, Kazuo; Kizaki, Minoru
JAERI-Tech 2005-051, 13 Pages, 2005/09
JAERI-Tech-2005-051.pdf:1.38MB
An apparatus has been developed to measure the thermal diffusivities of minor actinide (MA) compounds. By installing the laser flash apparatus in a glove box with highly purified inert gas atmosphere, the thermal diffusivities measurement of MA compounds of -decay nuclides was enabled. A new sample holder has been also developed to measure the thermal diffusivities of very small samples. The performance of this new apparatus was confirmed by measuring the thermal diffusivities of small samples of tantalum, nickel and cerium oxides. The thermal diffusivity values obtained in this work agreed well with the literature values and the values measured by a conventional thermal diffusivities measurement apparatus. Accordingly, this apparatus was found to be useful for thermal diffusivities measurement of MA compounds.
Saegusa, Jun; Kawasaki, Katsuya; Mihara, Akira; Ito, Mitsuo; Yoshida, Makoto
Applied Radiation and Isotopes, 61(6), p.1383 - 1390, 2004/12
Times Cited Count：29 Percentile：84.44(Chemistry, Inorganic & Nuclear)no abstracts in English
Ito, Mitsuo; Obara, Kazuhiro; Toida, Yukio*; Suzuki, Daisuke; Gunji, Katsubumi*; Watanabe, Kazuo
JAERI-Review 2004-007, 65 Pages, 2004/03
JAERI-Review-2004-007.pdf:5.53MB
no abstracts in English
Minato, Kazuo; Akabori, Mitsuo; Takano, Masahide; Arai, Yasuo; Nakajima, Kunihisa; Ito, Akinori; Ogawa, Toru
Journal of Nuclear Materials, 320(1-2), p.18 - 24, 2003/09
Times Cited Count：53 Percentile：94.55(Materials Science, Multidisciplinary)In the Japan Atomic Energy Research Institute, the concept of the transmutation of minor actinides (MA: Np, Am and Cm) with accelerator-driven systems is being studied. The MA nitride fuel has been chosen as a candidate because of the possible mutual solubility among the actinide mononitrides and excellent thermal properties besides supporting hard neutron spectrum. MA nitrides of AmN, (Am,Y)N, (Am,Zr)N and (Cm0.4Pu0.6)N were prepared from the oxides by the carbothermic reduction method. The prepared MA nitrides were examined by X-ray diffraction and the contents of impurities of oxygen and carbon were measured. The fabrication conditions for MA nitrides were improved so as to reduce the impurity contents. For an irradiation test of U-free nitride fuels, pellets of (Pu,Zr)N and PuN+TiN were prepared and a He-bonded fuel pin was fabricated. The irradiation test started in May 2002 and will go on for two years in the Japan Materials Testing Reactor.
Takano, Masahide; Ito, Akinori; Akabori, Mitsuo; Minato, Kazuo; Numata, Masami
Proceedings of GLOBAL2003 Atoms for Prosperity; Updating Eisenhower's Global Vision for Nuclear Energy (CD-ROM), p.2285 - 2291, 2003/00
Stability of AmN and (Am,Zr)N was studied comparatively from the viewpoints of the hydrolytic and evaporative behavior. AmN powder reacted with moisture to form hydroxide Am(OH), while the solid solution (Am
Zr
)N remained stable as long as 1000 hours. Stabilization effect of ZrN was found to depend significantly on its mole fraction from the experiments on (Dy,Zr)N. In the oxidation experiments on (Dy,Zr)N by TG-DTA technique, rapid weight gain by the oxidation occurred above 700 K. Effect of ZrN on the stability against oxygen was slight. Nitrogen release by the evaporation of AmN and (AmZr)N in He gas flow was measured by gas chromatography. Evaporation rate constants of AmN were obtained at 1623-1733 K. Although the evaporation rate constant of AmN in the solid solution were lower than those of the pure AmN, the selective evaporation of AmN from the solid slution were recognized, which resulted in a decrease in the Am mole fraction.
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
with LiCl-KCl eutectic probed by the U L-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
-Cl
distance and the coordination number of Cl around U ion were obtained by a curve fitting of the 1st shell XAFS function k
(k). The pair potential in the U-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.
