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Kinetics of corrosion and dissolution of uranium dioxide as a function of pH
Author(s) -
Torrero M. E.,
Baraj E.,
de Pablo J.,
Giménez J.,
Casas I.
Publication year - 1997
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/(sici)1097-4601(1997)29:4<261::aid-kin4>3.0.co;2-s
Subject(s) - dissolution , chemistry , uranium dioxide , uranium , oxidizing agent , stoichiometry , x ray photoelectron spectroscopy , leaching (pedology) , kinetics , corrosion , partial pressure , inorganic chemistry , oxygen , nuclear chemistry , chemical engineering , metallurgy , organic chemistry , materials science , environmental science , physics , quantum mechanics , soil science , engineering , soil water
A continuous flow‐through reactor with a thin layer of solid particles (size ranging from 100 to 300 μm) was used to obtain a deeper knowledge on the mechanism of dissolution of UO 2 under oxidizing conditions. Using this methodology the dissolution rate of uranium dioxide was determined at three different oxygen partial pressures (5, 21, and 100% in nitrogen) and as a function of pH (between 3 and 12) in a noncomplexing medium. From the results of these experiments the following rate equation was derived: $$(3 < pH < 6.7)\,r\,(mol\cdot s^{-1}\cdot m^{-2})\,=\,(3.5 \pm 0.8) \cdot 10^{-8} \cdot [H^{+}]^{0.37\pm 0.01}\cdot[O_2]^{0.31\pm 0.02}$$ In addition, XPS characterizations were performed to determine the U(IV)/U(VI) ratio on the solid surface at different experimental times and conditions. These results showed that at acidic conditions (pH below 6.7) the final solid surface presents a stoichiometry close to UO 2 , while at alkaline conditions the final solid surface average composition is close to UO 2.25 . This information was integrated with the results of the leaching experiments to present a model for the mechanism of dissolution of uranium dioxide under the experimental conditions. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 261–267, 1997.