Impact of Stoichiometry on the Mechanism and Kinetics of Oxidative Dissolution of UO 2 Induced by H 2 O 2 and γ-Irradiation

Radiation-induced oxidative dissolution of uranium dioxide (UO 2 ) is one of the most important chemical processes of U driven by redox reactions. We have examined the effect of UO 2 stoichiometry on the oxidative dissolution of UO 2 in aqueous sodium bicarbonate solution induced by hydrogen peroxid...

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Bibliographic Details
Published in:Journal of physical chemistry. C 2019-04, Vol.123 (15), p.9919-9925
Main Authors: Kumagai, Yuta, Barreiro Fidalgo, Alexandre, Jonsson, Mats
Format: Article
Language:English
Subjects:
Bicarbonate solution
Catalytic decomposition
Dissolution
Dissolution behavior
Dissolution kinetics
Gamma rays
Gamma-ray irradiation
Irradiation
Kinetics
Low concentrations
Mechanism and kinetics
Oxidative dissolution
Reaction kinetics
Redox reactions
Sodium bicarbonate
Stoichiometry
Uranium dioxide
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Summary:Radiation-induced oxidative dissolution of uranium dioxide (UO 2 ) is one of the most important chemical processes of U driven by redox reactions. We have examined the effect of UO 2 stoichiometry on the oxidative dissolution of UO 2 in aqueous sodium bicarbonate solution induced by hydrogen peroxide (H 2 O 2 ) and γ-ray irradiation. By comparing the reaction kinetics of H 2 O 2 between stoichiometric UO 2.0 and hyper-stoichiometric UO 2.3 , we observed a significant difference in reaction speed and U dissolution kinetics. The stoichiometric UO 2.0 reacted with H 2 O 2 much faster than the hyper-stoichiometric UO 2.3 . The U dissolution from UO 2.0 was initially much lower than that from UO 2.3 but gradually increased as the oxidation by H 2 O 2 proceeded. Increase in the initial H 2 O 2 concentration caused decrease in the U dissolution yield with respect to the H 2 O 2 consumption both for UO 2.0 and UO 2.3 . This decrease in the U dissolution yield is attributed to the catalytic decomposition of H 2 O 2 on the surface of UO 2 . The γ-ray irradiation induced the U dissolution that is analogous to the kinetics by the exposure to a low concentration (2 × 10 -4 mol dm -3 ) of H 2 O 2 . The exposure to higher H 2 O 2 concentrations caused lower U dissolution and resulted in deviation from the U dissolution behavior by γ-ray irradiation.
ISSN:1932-7447
1932-7455
1932-7455
DOI:10.1021/acs.jpcc.9b00862