• Title/Summary/Keyword: Uranium Dioxide

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Surface Reaction of Uranium Dioxide with CF$_4$/O$_2$ Mixture Gas Plasma (CF$_4$/O$_2$ 혼합기체 플라즈마를 이용한 이산화 우라늄의 표면식각반응)

  • 민진영;김용수
    • Journal of the Korean institute of surface engineering
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    • v.32 no.2
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    • pp.165-171
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    • 1999

  • The etching reaction of $UO_2$ in $CF_4/O_2$ gas plasma is examined as functions of $CF_4/O_2$ ratio, plasma power, and substrate temperature at up to $370^{\circ}C$ under the total pressure of 0.30 Torr. It is found that the highest etching rate is obtained at 20% $O_2$ mole fraction, regardless of r. f. power and substrate temperature. The existence of the optimum $CF_4/O_2$ ratio is confirmed by SEM, XPS and XRD analysis. The highest etching reaction rate at $370^{\circ}C$ under 150W exceeds 1000 monolayers/min., which is equivalent to 0.4$\mu\textrm{m}$/min. The mass spectrometry analysis results reveal that the major reaction product is uranium hexa-fluoride $UF_6$. Based on the experimental findings, dominant overall reaction of uranium dioxide in $CF_4/O_2$ plasma is determined : $8UO_2+12CF_4+3O_2=8UF_6+12CO_{2-x}$ where $CO_{2-x}$ represents the undetermined mix of $CO_2$ and CO.

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Effect of Sintering Atmosphere on the Densification and Grain Growth of Uranium Dioxide at the Final-Stage Sintering (소결 분위기에 따른 이산화 우라늄의 치밀화 및 입자성장)

  • 이영우
    • Journal of Powder Materials
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    • v.4 no.3
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    • pp.214-221
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    • 1997

  • The densification and grain growth mechanisms of $UO_{2+x}$ in $H_2$ and in $CO_2$ have been investigated. Uranium dioxide powder compacts were sintered at 1$700^{\circ}C$ in $H_2$ or at 110$0^{\circ}C$ in $CO_2$ for various times from 0.5 h to 16 h. The grain size and density of the specimens were measured. From the measured data, the mechanisms of the densification and grain growth were determined by use of available kinetic equations which express the relations between densification and grain growth. In both atmospheres, it has been found that the densification was controlled by the lattice diffusion and the grain growth by the surface diffusion of atoms around pores. It appears that the surface diffusivity as well as the lattice diffusivity increase considerably with the increase in O/U ratio in the specimen.

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Electronic States of Uranium Dioxide

  • Younsuk Yun;Park, Kwangheon;Hunhwa Lim;Song, Kun-Woo
    • Nuclear Engineering and Technology
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    • v.34 no.3
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    • pp.202-210
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    • 2002

  • The details of the electronic structure of the perfect crystal provides a critically important foundation for understanding the various defect states in uranium dioxide. In order to understand the local defect and impurity mechanism, the calculation of electronic structure of UO$_2$ in the one-electron approximation was carried out, using a semi-empirical tight-binding formalism(LCAO) with and without f-orbitals. The energy band, local and total density of states for both spin states are calculated from the spectral representation of Green’s function. The bonding mechanism in Perfect lattice of UO$_2$ is discussed based upon the calculations of band structure, local and total density of states.

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Analysis of the Irradiated Nuclear Fuel Using the Heavy Atom and Neodynium Isotope Correlations with Burnup

  • Kim, Jung-Suk
    • Nuclear Engineering and Technology
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    • v.29 no.4
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    • pp.327-335
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    • 1997

  • The correlation of isotope composition of uranium, plutonium and neodymium with the burnup in M uranium dioxide fuel has been investigated experimentally. The total and fractional($^{235}$ U) burnup were determined by Nd-148 and, U and Pu mass spectrometric method respectively. The isotope compositions of these elements, after their separation from the fuel samples were measured by mass spectrometric. The content of the elements in the irradiated fuel ore determined by isotope dilution mass spectrometric method using $^{233}$ U, $^{242}$ Pu and $^{150}$ Nd as spikes. The content of plutonium in the irradiated fuel was expressed by the correlation with uranium isotopes. The correlations between isotope compositions themselves and the total and fractional burnup ore compared with those calculated from ORIGEN2 code.

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