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Journal Articles

DFT study on the electronic structure and chemical state of americium in an (Am,U) mixed oxide

Suzuki, Chikashi; Nishi, Tsuyoshi; Nakada, Masami; Tsuru, Tomohito; Akabori, Mitsuo; Hirata, Masaru; Kaji, Yoshiyuki

Journal of Physics and Chemistry of Solids, 74(12), p.1769 - 1774, 2013/12

 Times Cited Count:12 Percentile:53.54(Chemistry, Multidisciplinary)

We investigated the electronic state of a CaF$$_{2}$$-type (Am,U) mixed oxide using the all-electron full potential linear augmented plane wave method and compared it with those of Am$$_{2}$$O$$_{3}$$, AmO$$_{2}$$, UO$$_{2}$$, and La$$_{0.5}$$U$$_{0.5}$$O$$_{2}$$. The valence of Am in the mixed oxide was close to that of Am$$_{2}$$O$$_{3}$$ and the valence of U in the mixed oxide was pentavalent. The electronic structure of AmO$$_{2}$$ was different from that of Am$$_{2}$$O$$_{3}$$, particularly just above the Fermi level. In addition, the electronic states of Am and U in the mixed oxide were similar to those of trivalent Am and pentavalent U oxides. These electronic states reflected the high oxygen potential of AmO$$_{2}$$ and the heightened oxygen potential resulting from the addition of Am to UO$$_{2}$$ and also suggested the occurrence of charge transfer from Am to U in the solid solution process.

JAEA Reports

Developing the soil moisture sensor using optical fiber technique (Joint research)

Komatsu, Mitsuru*; Nishigaki, Makoto*; Seno, Shoji*; Hirata, Yoichi*; Takenobu, Kazuyoshi*; Tagishi, Hirotaka*; Kunimaru, Takanori; Maekawa, Keisuke; Yamamoto, Yoichi; Toida, Masaru*; et al.

JAEA-Research 2012-001, 77 Pages, 2012/09

JAEA-Research-2012-001.pdf:4.85MB

This research focused on methods of estimating the amounts of groundwater recharge, which are normally required as upper boundary conditions in groundwater flow analyses, based on measurements of infiltrating water in the ground, to systematize the methods and establish systems which are stable and measurable on site over a long time. Regarding developing measurement systems, fiber-optic strain measurement methods that enable multiple-point and long-distance measurement were used for measuring three quantities: suction pressure, soil moisture and volumetric water content rate obtained by applying water absorption swelling material, and each measurement was discussed. The results showed that the fiber-optic soil aquameter has two types of practical application: one for measuring suction pressure (Type I), and the other for measuring volumetric water content rate obtained by applying water absorption swelling material (Type III). Furthermore, by using measurement instruments in actual fields, the validity of the two methods for estimating the rainfall infiltration capacities of shallow-layer soils, that is, estimating the capacities either directly by measurements of soil water or from unsaturated hydraulic conductivities, was confirmed.

Journal Articles

Thermodynamic properties of neptunium nitride; A First principles study

Shibata, Hiroki; Tsuru, Tomohito; Nishi, Tsuyoshi; Hirata, Masaru; Kaji, Yoshiyuki

Journal of Nuclear Science and Technology, 49(3), p.328 - 333, 2012/03

 Times Cited Count:4 Percentile:36.4(Nuclear Science & Technology)

The thermal and mechanical properties of neptunium nitride (NpN) were investigated by first principles calculations. From the Helmholtz free energy equilibrium lattice constants, thermal expansion coefficients, bulk moduli and specific heat capacities were calculated for temperatures up to 1500 K. The electronic specific heat capacity was also calculated from the electronic density of states (DOS) at the Fermi energy. The obtained specific heat capacity reproduced the experimental data well. It was thus clarified that the specific heat capacity of NpN consists of the lattice and electronic specific heat capacities and the contribution of the lattice dilatation to the specific heat capacity.

Journal Articles

Core-hole effect on XANES and electronic structure of minor actinide dioxides with fluorite structure

Suzuki, Chikashi; Nishi, Tsuyoshi; Nakada, Masami; Akabori, Mitsuo; Hirata, Masaru; Kaji, Yoshiyuki

Journal of Physics and Chemistry of Solids, 73(2), p.209 - 216, 2012/02

 Times Cited Count:21 Percentile:67.53(Chemistry, Multidisciplinary)

The authors investigated theoretically core-hole effects on X-ray absorption near-edge structures (XANES) of Np and Am L$$_{III}$$ in neptunium dioxide (NpO$$_{2}$$) and americium dioxide (AmO$$_{2}$$) with CaF$$_{2}$$-type crystal lattices using the all-electron full-potential linearized augmented plane-wave (FP-LAPW) method. The peak creation mechanism of XANES was shown by examining the electronic structures of these oxides, which indicated that core-hole screening was more marked for AmO$$_{2}$$ than for NpO$$_{2}$$ because of the difference in the charge transfer between these oxides. Furthermore, the results of charge density analysis suggested that the white line was assigned to the quasi-bound state composed of the localized Np d or Am d components and O components, and that the tail structure was created as a result of delocalized standing waves between the Np or Am atoms.

Journal Articles

Valence state of Am in (U$$_{0.95}$$Am$$_{0.05}$$)O$$_{2.0}$$

Nishi, Tsuyoshi; Nakada, Masami; Suzuki, Chikashi; Shibata, Hiroki; Okamoto, Yoshihiro; Akabori, Mitsuo; Hirata, Masaru

Journal of Nuclear Materials, 418(1-3), p.311 - 312, 2011/11

 Times Cited Count:19 Percentile:83.81(Materials Science, Multidisciplinary)

The XAFS measurements at U-L$$_{3}$$ and Am-L$$_{3}$$ absorption edge of (U$$_{0.95}$$Am$$_{0.05}$$)O$$_{2.0}$$ were performed in transmission mode. Moreover, to clarify the valence state of Am in (U,Am)O$$_{2-x}$$, the XANES spectrum of Am-L$$_{3}$$ absorption edge of (U$$_{0.95}$$Am$$_{0.05}$$)O$$_{2.0}$$ was verified using those of Am-L$$_{3}$$ absorption edge of AmO$$_{2}$$ and Am$$_{2}$$O$$_{3}$$. It was found that the XANES spectrum of the Am-L$$_{3}$$ edge of (U$$_{0.95}$$Am$$_{0.05}$$)O$$_{2.0}$$ is in good accordance with that of Am$$_{2}$$O$$_{3}$$. Thus, Am in (U$$_{0.95}$$Am$$_{0.05}$$)O$$_{2.0}$$ is almost trivalent state.

Journal Articles

Production and properties of transuranium elements

Nagame, Yuichiro; Hirata, Masaru

Radiochimica Acta, 99(7-8), p.377 - 393, 2011/08

 Times Cited Count:10 Percentile:65.84(Chemistry, Inorganic & Nuclear)

Journal Articles

Production and chemistry of transuranium elements

Nagame, Yuichiro; Hirata, Masaru; Nakahara, Hiromichi*

Handbook of Nuclear Chemistry, p.817 - 875, 2011/02

Journal Articles

Relativistic density-functional study of solid solubitilty of tansiton metal/$$gamma$$-uranium alloys; The Roll of d-d orbital interactions

Kurihara, Masayoshi*; Onoe, Jun*; Hirata, Masaru; Suzuki, Chikashi

Journal of Alloys and Compounds, 509(4), p.1152 - 1156, 2011/01

 Times Cited Count:3 Percentile:27.19(Chemistry, Physical)

The alloying behavior of transition metals (TMs) in solid $$gamma$$-phase uranium ($$gamma$$-U), which is expected to be used as fuel for next-generation nuclear reactors, is investigated using the discrete-variational Dirac-Fock-Slater molecular orbital method. Using a model cluster, U$$_{8}$$/TM, as the minimum unit of $$gamma$$-U/TM alloys, we evaluate the d-orbital energy of the TM (Md), the bond order between the TM and U atoms, and the orbital overlap population (OOP) between the atomic orbitals of the TM and U atoms. We subsequently examine the effect of these quantities on the maximum solid solubility (MSS) of the $$gamma$$-U/TM alloys. Md and the OOP (U 6d-TM d) exhibit good correlations with the MSS for $$gamma$$-U/TM alloys, so that the interaction between the U-6d and TM-d atomic orbitals is found to play a key role in determining the MSS of the $$gamma$$-U/TM alloys. The magnitude of the MSS can be explained in terms of the stabilization energy caused by U 6d-TM d orbital interactions for $$gamma$$ -U/TM alloys, which is affected by the Md and the OOP. The exponential dependence of the MSS on Md and the OOP is explained in terms of the equilibrium constant obtained using a substitution cluster model for $$gamma$$-U/TM alloys. We also map the MSS of $$gamma$$-U/TM alloys using the Md and the OOP as the alloying parameters. These results will assist the quantum design of nuclear fuel materials for other alloy systems besides the present alloy system.

Journal Articles

Local and electronic structure of Am$$_{2}$$O$$_{3}$$ and AmO$$_{2}$$ with XAFS spectroscopy

Nishi, 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:25 Percentile:87.19(Materials Science, Multidisciplinary)

XAFS studies were performed in a study of americium sesquioxide (Am$$_{2}$$O$$_{3}$$) with A-type rare earth oxide structure and americium dioxide (AmO$$_{2}$$) with fluorite structure. EXAFS results for Am-L$$_{3}$$ absorption edge of Am$$_{2}$$O$$_{3}$$ and AmO$$_{2}$$ 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 Am$$_{2}$$O$$_{3}$$ and AmO$$_{2}$$ were performed with the all-electron full potential linearized augmented plane wave (FP-LAPW) method. The theoretical XANES spectra of Am$$_{2}$$O$$_{3}$$ and AmO$$_{2}$$ 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.

Journal Articles

First principles study on elastic properties and phase transition of NpN

Shibata, Hiroki; Tsuru, Tomohito; Hirata, Masaru; Kaji, Yoshiyuki

Journal of Nuclear Materials, 401(1-3), p.113 - 117, 2010/06

 Times Cited Count:14 Percentile:72.34(Materials Science, Multidisciplinary)

The mechanical properties of neptunium nitride (NpN) were investigated using first principles calculations based on density functional theory that take the Spin-Orbit Coupling (SOC) effect into consideration. With NaCl, CsCl and ZnS structures in nonmagnetic (NM), ferromagnetic (FM) and antiferromagnetic (AFM) states, the structure of NaCl in all magnetic states and that of ZnS, excluding the NM state without SOC, were found to be mechanically stable. The bulk moduli, elastic constants, Young's moduli, Poisson's ratios and anisotropic factors of NpN in stable states were also estimated. The enthalpies of NpN for NaCl and ZnS structures revealed that the phase transition of NpN from ZnS structure to NaCl structure took place at a pressure of -7.32 GPa, and hence the phase transition of NpN in a cubic system does not occur at positive pressure.

Journal Articles

FISA2009 conference report

Hirata, Masaru

Nihon Genshiryoku Gakkai-Shi ATOMO$$Sigma$$, 51(10), P. 53, 2009/10

The FISA2009 meeting was held in Prague from June 22 to June 25. The 450 conference participants, discussed the next generation nuclear energy systems, such as SFR, GFR etc. nuclear energy sources in Europe. In the review, I presented an outline of the important topics discussed at the conference.

Journal Articles

Chloride complexation of Zr and Hf in HCl investigated by extended X-ray absorption fine structure spectroscopy; Toward characterization of chloride complexation of element 104, rutherfordium (Rf)

Haba, Hiromitsu*; Akiyama, Kazuhiko*; Tsukada, Kazuaki; Asai, Masato; Toyoshima, Atsushi; Yaita, Tsuyoshi; Hirata, Masaru; Sueki, Keisuke*; Nagame, Yuichiro

Bulletin of the Chemical Society of Japan, 82(6), p.698 - 703, 2009/06

 Times Cited Count:10 Percentile:41.76(Chemistry, Multidisciplinary)

Chloride complexation of the group-4 elements Zr and Hf in 8.0-11.9 M HCl is investigated by Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy to characterize chloro complexes of the transactinide element, rutherfordium (Rf). The complexes of Zr and Hf successively vary with the concentration of HCl from a hydrated complex [M(H$$_{2}$$O) $$_{8}$$]$$^{4+}$$ at 8.0 M to a hexachloro complex [MCl$$_{6}$$]$$^{2-}$$ at 11.9 M (M = Zr and Hf). The present structural changes of the Zr and Hf complexes well reflect the previously studied anion-exchange behavior of Zr and Hf in HCl. From both the EXAFS and anion-exchange results, we suggest that Rf forms the same complexes as those of Zr and Hf in HCl, and that the complexation strength of the hexachloro complexes of the group-4 elements, [MCl$$_{6}$$] $$^{2-}$$ (M = Zr, Hf, and Rf), is in the sequence of Rf $$>$$ Zr $$>$$ Hf.

Journal Articles

Calculation of the electronic structure of AmO$$_{2}$$ and Pr$$_{6}$$O$$_{11}$$ for XANES analysis with redox property

Suzuki, Chikashi; Nishi, Tsuyoshi; Nakada, Masami; Akabori, Mitsuo; Hirata, Masaru; Kaji, Yoshiyuki

International Journal of Quantum Chemistry, 109(12), p.2744 - 2752, 2009/05

 Times Cited Count:5 Percentile:35.3(Chemistry, Physical)

no abstracts in English

Journal Articles

Extraction of actinides by multidentate diamides and their evaluation with computational molecular modeling

Sasaki, Yuji; Kitatsuji, Yoshihiro; Hirata, Masaru; Kimura, Takaumi; Yoshizuka, Kazuharu*

Proceedings of International Solvent Extraction Conference "Solvent Extraction-Fundamentals to Industrial Applications" (ISEC 2008), p.745 - 750, 2008/09

The multidentate diamides are synthesized and examined for the actinide (An) extractions, bi- and tridentate extractants are focused in this work. The extraction of actinide was performed from 0.1-6M HNO$$_{3}$$ to organic solvents. It was obvious that tetraalkyl-diglycolamide (DGA) derivatives, (methylimino)bis(N,N-dioctylacetamide) (MIDOA) and dimethyl-dioctyl-2-(3-oxapentadecane)-malonamide (DMDOOPDMA) have relatively high D values (D(Pu): more than 70). The following notable results using DGA extractants are obtained, (1) DGA with short alkyl chain give higher D values than those with long alkyl chain, (2) DGA with long alkyl chain have high solubility in n-dodecane. The molecular modeling with computational chemistry was also used to elucidate the effects of structural and electronic properties of the reagents on their different extractabilities.

Journal Articles

EXAFS and XANES studies of americium dioxide with fluorite structure

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:19 Percentile:79.01(Materials Science, Multidisciplinary)

EXAFS and XANES analysis were applied in a study of americium dioxide (AmO$$_{2}$$) with fluorite structure. EXAFS result for Am-L$$_{3}$$ absorption edge of AmO$$_{2}$$ 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$$_{2}$$ was performed with the relativistic DV-X$$alpha$$ 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.

Journal Articles

Application of the relativistic DV-X$$alpha$$ molecular orbital method to $$gamma$$-uranium alloys with transition metals

Kurihara, Masayoshi*; Hirata, Masaru; Onoe, Jun*; Nakamatsu, Hirohide*

Progress in Nuclear Energy, 50(2-6), p.549 - 555, 2008/03

 Times Cited Count:1 Percentile:10.92(Nuclear Science & Technology)

The alloying behavior of 4d and 5d transition metals (TMs) in $$gamma$$-phase solid uranium (U) has been investigated using the discrete-variational Dirac-Fock-Slater (DV-DFS) method. We examined the d-orbital energy (Md value) of these TMs, the orbital overlap population (OOP) between the d-orbital of these TMs and the 5f or 6d orbital of $$gamma$$-U, and the effective charge on each atom of the $$gamma$$-U/TM alloy, and the effect of these parameters on alloying. It was found that the maximum solid solubility of TMs into $$gamma$$-U was exponentially proportional to both the Md and the OOP (U5f-TMd and U6d-TMd). We found a good correlation between the MSS and Md, the effective charge, or OOP.

Journal Articles

"Crystal lattice engineering", an approach to engineer protein crystal contacts by creating intermolecular symmetry; Crystallization and structure determination of a mutant human RNase 1 with a hydrophobic interface of leucines

Yamada, Hidenori*; Tamada, Taro; Kosaka, Megumi*; Miyata, Kohei*; Fujiki, Shinya*; Tano, Masaru*; Moriya, Masayuki*; Yamanishi, Mamoru*; Honjo, Eijiro; Tada, Horiko*; et al.

Protein Science, 16(7), p.1389 - 1397, 2007/07

 Times Cited Count:35 Percentile:58.98(Biochemistry & Molecular Biology)

In an attempt to control protein incorporation in a crystal lattice, a leucine zipper-like hydrophobic interface (comprising four leucine residues) was introduced into a helical region (helix 2) of the human pancreatic ribonuclease 1 (RNase 1) that was predicted to form a suitable crystallization interface. Although crystallization of wild type RNase 1 has not yet been reported, the RNase 1 mutant having four leucines (4L-RNase 1) was successfully crystallized under several different conditions. The crystal structures were subsequently determined by X-ray crystallography by molecular replacement using the structure of bovine RNase A. The overall structure of 4L-RNase 1 is quite similar to that of the bovine RNase A, and the introduced leucine residues formed the designed crystal interface. To further characterize the role of the introduced leucine residues in crystallization of RNase 1, the number of leucines was reduced to three or two (3L- and 2L-RNase 1, respectively). Both mutants crystallized and a similar hydrophobic interface as in 4L-RNase 1 was observed. A related approach to engineer crystal contacts at helix 3 of RNase 1 (N4L-RNase 1) was also evaluated. N4L-RNase 1 also successfully crystallized, and formed the expected hydrophobic packing interface. These results suggest that appropriate introduction of a leucine zipper-like hydrophobic interface can promote intra molecular symmetry for more efficient protein crystallization in crystal lattice engineering efforts.

Journal Articles

An Additional insight into the correlation between the distribution ratios and the aqueous acidity of the TODGA system

Sasaki, Yuji; Rapold, P.*; Arisaka, Makoto; Hirata, Masaru; Kimura, Takaumi; Hill, C.*; Cote, G.*

Solvent Extraction and Ion Exchange, 25(2), p.187 - 204, 2007/03

 Times Cited Count:115 Percentile:91.88(Chemistry, Multidisciplinary)

Extraction of Eu(III) and Am(III) from HNO$$_{3}$$ into the organic solvents using N,N,N',N'-tetraoctyl-diglycolamide (TODGA) was investigated in order to study the detailed extraction reaction. The chemical species: 1:2 for metal:TODGA complex is present in polar diluents. On the other hand, the metal complexes need three or more number of TODGA molecules to remain stable in non-polar diluents. The HNO$$_{3}$$ concentration dependence on the distribution ratio suggests that HNO$$_{3}$$ participates in the metal extraction. Infrared spectra indicate that the carbonyl oxygen coordinates with Eu(III), and luminescence lifetimes suggest that there is no water molecule in the inner coordination sphere of Eu-complex extracted.

Journal Articles

First principles molecular dynamics simulation of solution

Boero, M.*; Ikeda, Takashi; Hirata, Masaru

Annual Report of the Earth Simulator Center April 2005 - March 2006, p.267 - 270, 2007/01

no abstracts in English

Journal Articles

Hydrolysis of Al$$^{3+}$$ from constrained molecular dynamics

Ikeda, Takashi; Hirata, Masaru; Kimura, Takaumi

Journal of Chemical Physics, 124(7), p.074503_1 - 074503_7, 2006/02

 Times Cited Count:33 Percentile:75.33(Chemistry, Physical)

We investigated the hydrolysis reactions of Al$$^{3+}$$ in AlCl$$_{3}$$ aqueous solution using the constrained molecular dynamics based on Car-Parrinello molecular dynamics method. By employing the proton-aluminum coordination number as a reaction coordinate in the constrained molecular dynamics the deprotonation as well as dehydration processes are successfully realized. From our free-energy difference of $$Delta G^{0}simeq8.0$$kcal$$cdot$$mol$$^{-1}$$ the hydrolysis constant $$pK_{a1}$$ is roughly estimated as 5.8 comparable to the literature value of 5.07. We show that the free-energy difference for hydrolysis of Al$$^{3+}$$ in acidic conditions is at least 4kcal$$cdot$$mol$$^{-1}$$ higher than that in neutral condition, indicating that the hydrolysis reaction is inhibited by the presence of excess protons located around the hydrated ion in agreement with the change of the predominant species by $$p$$H.

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