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217 results on '"Kobayashi, Taishi"'

7. Dissolution of zirconium–cerium oxide solid solution in an aqueous system.

Author

Kobayashi, Taishi, Sato, Yutaro, Tonna, Ryutaro, Matsumura, Daiju, Sasaki, Takayuki, and Ikeda-Ohno, Atsushi

Subjects
*PRECIPITATION (Chemistry), *SOLID solutions, *WATER immersion, *X-ray powder diffraction, *RIETVELD refinement, *CERIUM oxides
Abstract

The solid-solution aqueous-solution (SSAS) system often involves dissolution/precipitation and redox reactions simultaneously. Comprehensive understanding of the SSAS system requires mechanistic insights into the dissolution mechanism of the solid solution based on reliable characterisation of the solid phases. Given this background, this study investigates the dissolution behaviour of zirconium–cerium oxide solid solution ((Zr,Ce)O2/(Ce,Zr)O2), which contains the redox-active metal Ce (Ce(III / IV)) and is of particular importance in the nuclear industry. The solid phases of the solid solution were comprehensively characterised by powder X-ray diffraction (PXRD) with Rietveld analysis and X-ray absorption spectroscopy (XAS) with factor analysis, indicating that the solid solution was primarily composed of tetragonal-(Zr,Ce)O2 and cubic-(Ce,Zr)O2. Water immersion of the solid solution leads to the dissolution of the solid phase at the solid–liquid interface. The addition of a reductant to the system reduces Ce(IV) in the solid solution to -(III) at the surface, promoting the dissolution of Ce from the solid-solution phase. The release of Ce from the solid solution also enriches the Zr content in the remaining solid-solution phase at the surface, which makes it more insoluble. This results in the formation of a protective layer at the solid surface, retarding further dissolution of the solid-solution phase. [ABSTRACT FROM AUTHOR]

Published
2024
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24. Phase analysis of simulated nuclear fuel debris synthesized using UO2, Zr, and stainless steel and leaching behavior of the fission products and matrix elements

Author

Tonna, Ryutaro, primary, Sasaki, Takayuki, additional, Kodama, Yuji, additional, Kobayashi, Taishi, additional, Akiyama, Daisuke, additional, Kirishima, Akira, additional, Sato, Nobuaki, additional, Kumagai, Yuta, additional, Kusaka, Ryoji, additional, and Watanabe, Masayuki, additional

Published
2022
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27. Solubility of PuO₂(am,hyd) and the Formation of Pu(IV) Carbonate Complexes in Carbonate Solutions Containing 0.1–5.0mol·dm⁻³ NaNO₃

Author

Kobayashi, Taishi, Fellhauer, David, and Sasaki, Takayuki

Subjects
Solubility, Carbonate, Ionic strength, Complex formation, PuO₂(am, hyd)
Abstract

The solubility of plutonium hydrous oxide (PuO₂(am, hyd)) was investigated in the presence of carbonate in neutral to alkaline, dilute to concentrated sodium nitrate (NaNO₃) solutions. The observed dependence of the Pu(IV) solubility in low to medium concentration NaNO₃ agreed with previously reported data and was well reproduced by the thermodynamic model curves, containing the species Pu(CO₃)₄⁴⁻, Pu(CO₃)₅⁶⁻, and Pu(OH)₂CO₃)₂²⁻. Significant deviations between experimental and modeled Pu(IV) solubility were, however, observed for 2 mol.dm⁻³ NaNO₃ solutions. A more comprehensive chemical model including the complex Pu(OH)₂(CO₃)₄⁴⁻ was established, that reproduces the experimental results reasonably well. The conditional complex formation constants for Pu(OH)₂(CO₃)₂⁴⁻ were extrapolated to I = 0 using the specific ion interaction theory (SIT) and Pitzer approaches, and the corresponding ion interaction parameters were evaluated.

Published
2021

34. Solubility of Mixed Lanthanide Hydroxide and Oxide Solid Solutions

Author

80630269, 60314291, Moniruzzaman, Mohammad, Kobayashi, Taishi, Sasaki, Takayuki, 80630269, 60314291, Moniruzzaman, Mohammad, Kobayashi, Taishi, and Sasaki, Takayuki

Abstract

The solubilities of different multicomponent lanthanide oxide (Ln₂O₃) solid solutions including binary (Ln₁ and Ln₂ = La, Nd, Eu, or Tm), ternary (Ln₁, Ln₂, and Ln₃ = La, Nd, Eu, or Tm), and higher systems (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) were studied after aging for four weeks at 60°C. Our recent study revealed that the phase transformations in binary ((La, Nd) and (La, Eu)) and ternary (La, Nd, Eu) systems are responsible for the formation of (La, Nd)(OH)₃, (La, Eu)(OH)₃, and (La, Nd, Eu)(OH)₃ solid solutions, respectively. The variations in the mole fractions of La³⁺, Nd³⁺, and Eu³⁺ in the sample solutions of these hydroxide solid solutions indicated that a thermodynamic equilibrium might account for the apparent La, Nd, and Eu solubilities. Conversely, the binary and ternary systems containing Tm₂O₃ as the heavy lanthanide oxide retained the oxide-based solid solutions, and their solubility behaviors were dominated by their congruent dissolutions. In the higher multicomponent system, the X-ray diffraction patterns of the solid phases, before and after contact with the aqueous phase indicated the formation of a stable oxide solid solution and their solubility behavior was explained by its congruent dissolution.

Published
2021

35. Solubility of PuO₂(am,hyd) and the Formation of Pu(IV) Carbonate Complexes in Carbonate Solutions Containing 0.1–5.0 mol·dm⁻³ NaNO₃

Author

80630269, 60314291, Kobayashi, Taishi, Fellhauer, David, Sasaki, Takayuki, 80630269, 60314291, Kobayashi, Taishi, Fellhauer, David, and Sasaki, Takayuki

Abstract

The solubility of plutonium hydrous oxide (PuO₂(am, hyd)) was investigated in the presence of carbonate in neutral to alkaline, dilute to concentrated sodium nitrate (NaNO₃) solutions. The observed dependence of the Pu(IV) solubility in low to medium concentration NaNO₃ agreed with previously reported data and was well reproduced by the thermodynamic model curves, containing the species Pu(CO₃)₄⁴⁻, Pu(CO₃)₅⁶⁻, and Pu(OH)₂CO₃)₂²⁻. Significant deviations between experimental and modeled Pu(IV) solubility were, however, observed for 2 mol.dm⁻³ NaNO₃ solutions. A more comprehensive chemical model including the complex Pu(OH)₂(CO₃)₄⁴⁻ was established, that reproduces the experimental results reasonably well. The conditional complex formation constants for Pu(OH)₂(CO₃)₂⁴⁻ were extrapolated to I = 0 using the specific ion interaction theory (SIT) and Pitzer approaches, and the corresponding ion interaction parameters were evaluated.

Published
2021

36. ドイツゴ ノ メイシカ ニオケル コウ ジツゲン ノ トウゴロンテキ・イミロンテキ ゲンリ : メイシコウ ト シジ ドウテイ ノ カンケイ ニ チュウモク シテ

Author

Kobayashi, Taishi

Subjects
ドイツ語 -- 動詞, ドイツ語 -- 構文論
Abstract

PDF/A形式により利用可能, アクセス:WWWによる, 東京外国語大学大学院総合国際学研究科博士 (学術) 論文 (2020年9月), 博甲第300号, その他のタイトルは英文要旨による, 参考文献: p323-331

Published
2020

37. ドイツ語の名詞化における項実現の統語論的・意味論的原理 : 名詞項と指示同定の関係に注目して

Author

小林, 大志, コバヤシ, タイシ, Kobayashi, Taishi, 小林, 大志, コバヤシ, タイシ, and Kobayashi, Taishi

Abstract

PDF/A形式により利用可能, アクセス:WWWによる, 東京外国語大学大学院総合国際学研究科博士 (学術) 論文 (2020年9月), 博甲第300号, その他のタイトルは英文要旨による, 参考文献: p323-331, 東京外国語大学 (Tokyo University of Foreign Studies), 博士 (学術）

Published
2020

42. PCでのFaSTAR並列計算による航空機クリーン形態シミュレーション

Author

Kobayashi, Taishi, Ito, Yoshiaki, and Matsushima, Kisa

Abstract

Second Aerodynamics Prediction Challenge (APC-II) ワークショップ (2016年7月6日. 金沢歌劇座), 金沢市, 石川, 注記: 第48回流体力学講演会/第34回航空宇宙数値シミュレーション技術シンポジウム内で実施, 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA1630028007, レポート番号: JAXA-SP-16-004

Published
2016

43. Parametric numerical simulation of wing planforms for aerodynamic characteristics in supersonic flows

Author

Matsushima, Kisa, Kobayashi, Taishi, Kanazaki, Masahiro, and Kusunose, Kazuhiro

Abstract

第47回流体力学講演会/第33回航空宇宙数値シミュレーション技術シンポジウム (2015年7月2日-3日. 東京大学生産技術研究所), 目黒区, 東京, 47th Fluid Dynamics Conference /the 33rd Aerospace Numerical Simulation Symposium (July 2-3, 2015. Institute of Industrial Science , the University of Tokyo), Meguro-ku, Tokyo, Japan, To systematically investigate the aerodynamic characteristics of swept-back and forwarded wings with 0, 30, 45 and 60 degree of leading edge angles and different taper ratio, Navier-Stokes simulations for flows about a wing have been conducted. The Mach numbers of the flows are from 0.8 to 2.8. The planforms of wings are in various shapes whose aspect ratio is 2. The simulation and investigation has revealed new knowledge on the relation between swept or forwarded angles and aerodynamic characteristics of a wing in a supersonic flow. Not only a leading edge angle but also a trailing edge angle take important role on aerodynamics of a wing. In addition, transition from detached shockwaves to attached ones at the both edge largely affects the C(sub D)., 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA1630005019, レポート番号: JAXA-SP-15-013

Published
2016

48. Vertical distribution of 90Sr and 137Cs in soils near the Fukushima Daiichi nuclear power station.

Author

Sasaki, Takayuki, Matoba, Daisuke, Dohi, Terumi, Fujiwara, Kenso, Kobayashi, Taishi, and Iijima, Kazuki

Subjects
NUCLEAR power plants, DEPTH profiling, SOILS, SOIL sampling, RADIOACTIVITY
Abstract

The radioactivity concentrations for 90Sr and 137Cs in soil samples collected near Fukushima Daiichi nuclear power station were investigated. The depth profile of 137Cs from the surface soil to 20 cm showed a typical decreasing tendency, that is, high radioactivity from the surface down to 5 cm due to the strong sorption of specific minerals. After deposition of 90Sr, 90Sr has migrated to deeper soil layers in the past 5 years compared to 137Cs. This tendency was supported by the results of sequential extraction to identify the predominant sorption species, and by the sorption coefficients determined by batch-wise sorption experiments. [ABSTRACT FROM AUTHOR]

Published
2020
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