The kinetics of dissolution of UO sub 2 under reducing conditions and the influence of an oxidized surface layer (UO sub 2+x ): Application of a continuous flow-through reactor

Journal Article · Fri Mar 01 04:00:00 EST 1991 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(91)90330-8· OSTI ID:6084855

Bruno, J; Casas, I; Puigdomenech, I ^[1]

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1. Royal Inst. of Tech., Stockholm (Sweden)

The authors have studied the kinetics of dissolution of uranium dioxide, UO{sub 2}(s), under strongly reducing conditions (H{sub 2}(g)/Pd). They have investigated the dependence of the rate of dissolution as a function of critical geochemical parameters: pH, pCO{sub 2}, and carbonate concentration. By using a stirred batch reactor, the kinetics of dissolution of an UO{sub 2+x} surface layer and the subsequent precipitation of UO{sub 2} have also been studied. Although the initial UO{sub 2} is pretreated before starting the experiments, it seems to be very difficult to avoid the formation of the oxidized surface layer. For this reason they have developed a thin layer continuous flow-through reactor in order to study the kinetics of dissolution of pure UO{sub 2}(s). The aims of this work are to present a general study of the kinetics of dissolution of UO{sub 2} as a function of (1) the redox state of the surface; (2) the proton concentration (pH) of the solution in contact; (3) the pCO{sub 2} and the bicarbonate concentration; and to discuss the results of the investigation in terms of the dependence of the degree of surface protonation as a function of the pH. Consequently, to establish the mechanism of dissolution of pure UO{sub 2} and an oxidized, UO{sub 2+x}, surface layer under anoxic natural waters conditions is intended.

• OSTI ID: 6084855
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 55:3; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

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ACID CARBONATES
ACTINIDE COMPOUNDS
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMICAL REACTORS
CHEMISTRY
DISSOLUTION
ENVIRONMENTAL TRANSPORT
GEOCHEMISTRY
GROUND WATER
HYDROGEN COMPOUNDS
KINETICS
MANAGEMENT
MASS TRANSFER
MATERIALS
MINERALS
NUCLEAR FACILITIES
ORES
OXIDATION
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PARTIAL PRESSURE
PH VALUE
RADIOACTIVE MATERIALS
RADIOACTIVE MINERALS
RADIOACTIVE WASTE DISPOSAL
RADIOACTIVE WASTE FACILITIES
RADIOACTIVE WASTE MANAGEMENT
RADIOACTIVE WASTES
RADIONUCLIDE MIGRATION
REACTION KINETICS
REDOX REACTIONS
SOLUBILITY
SURFACE PROPERTIES
UNDERGROUND DISPOSAL
URANINITES
URANIUM COMPOUNDS
URANIUM MINERALS
URANIUM ORES
URANIUM OXIDES
VALENCE
WASTE DISPOSAL
WASTE MANAGEMENT
WASTES
WATER