Reactivity of various UO sub(3) modifications in the fluorination to UF sub(4) by Freon-12

Six uranium trioxide modifications, alpha , beta , gamma , amorphous, zeta , and delta -UO sub(3), were fluorinated directly to UF sub(4) by reaction with CCl sub(2)F sub(2) at 753 K. The first four oxides needed various periods of time to attain stoichiometric conversion to UF sub(4) (99%); these a...

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Bibliographic Details
Published in:Journal of nuclear materials 1992-01, Vol.195 (1-2), p.126-133
Main Authors: Girgis, B S, Rofail, N H
Format: Article
Language:English
Subjects:
Chemical modification
Fluorine compounds
Fluorocarbons
Nuclear fuels
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Summary:Six uranium trioxide modifications, alpha , beta , gamma , amorphous, zeta , and delta -UO sub(3), were fluorinated directly to UF sub(4) by reaction with CCl sub(2)F sub(2) at 753 K. The first four oxides needed various periods of time to attain stoichiometric conversion to UF sub(4) (99%); these are 4, 4, 2 and 3 h, respectively. The apparent differences are attributed to the degree of disorder in the oxide structure and to their specific surface areas. The latter two oxides ( gamma and delta -UO sub(3)) reacted passively towards fluorination, which was discussed in the light of their surface structure. These two oxides showed neither uranyl bonding character nor residual surface water (molecular or OH-groups). The former effect leads to the presence of an odd oxygen and enhances a covalent character and to a weakening effect on the U-O uranyl bond. The latter effect (surface water) furnishes acid-base centers that catalyze the fluorination process.
ISSN:0022-3115