Preparation and Characterization of Uranium Oxides in Support of the K Basin Sludge Treatment Project
Uraninite (UO2) and metaschoepite (UO3·2H2O) are the uranium phases most frequently observed in K Basin sludge. Uraninite arises from the oxidation of uranium metal by anoxic water and metaschoepite arises from oxidation of uraninite by atmospheric or radiolytic oxygen. Studies of the oxidation of uraninite by oxygen to form metaschoepite were performed at 21°C and 50°C. A uranium oxide oxidation state characterization method based on spectrophotometry of the solution formed by dissolving aqueous slurries in phosphoric acid was developed to follow the extent of reaction. This method may be applied to determine uranium oxide oxidation state distribution in K Basin sludge. The uraninite produced by anoxic corrosion of uranium metal has exceedingly fine particle size (6 nm diameter), forms agglomerates, and has the formula UO2.004±0.007; i.e., is practically stoichiometric UO2. The metaschoepite particles are flatter and wider when prepared at 21°C than the particles prepared at 50°C. These particles are much smaller than the metaschoepite observed in prolonged exposure of actual K Basin sludge to warm moist oxidizing conditions. The uraninite produced by anoxic uranium metal corrosion and the metaschoepite produced by reaction of uraninite aqueous slurries with oxygen may be used in engineering and process development testing. A rapid alternative method to determine uranium metal concentrations in sludge also was identified.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 940228
- Report Number(s):
- PNNL-17678; 830403000
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
Beer-Lambert
CORROSION
DISTRIBUTION
OXIDATION
OXYGEN
PARTICLE SIZE
PHOSPHORIC ACID
SLUDGES
SLURRIES
SPECTROPHOTOMETRY
Scherrer equation
TESTING
U3O8
UO2
UO3·2H2O
URANINITES
URANIUM
URANIUM OXIDES
VALENCE
WATER
dehydrated schoepite
metaschoepite
phosphoric acid
selective dissolution
shrinking core
spectrophotometry
uraninite
uranium metal
uranium octaoxide