Study of mass and momentum transfer and their effect on the direct fluorination of uranium oxide

Technical Report · Thu Feb 24 23:00:00 EST 1983

OSTI ID:5808262

Cross, P E

The mechanism for the fluorination of solid U/sub 3/O/sub 8/ to gaseous UF/sub 6/ was found to be a two-step process with solid UO/sub 2/F/sub 2/ as an intermediate. The highest particle temperatures were found to be associated with the initial reaction step to UO/sub 2/F/sub 2/; it was recommended that these temperatures be maintained below 1700/sup 0/F. The chemical equilibrium constant for the fluorination of PuF/sub 4/ to PuF/sub 6/ was found to be unexpectedly low at typical flame tower temperatures. Although not confirmed, there is an indication in the literature that a similar equilibrium constant is associated with the fluorination of NpF/sub 4/ and other transuranic molecules. It was recommended that uranium oxides which are significantly contaminated with transuranics should not be processed through a direct fluorination reactor such as the UF/sub 6/ flame tower. Reaction rate equations were developed for the fluorination of U/sub 3/O/sub 8/, UF/sub 4/, PuF/sub 4/ and NpF/sub 4/. During the course of the development, a significant discrepancy was found in the literature for the activation energy of the fluorination of U/sub 3/O/sub 8/. Equations were developed for both a high and low limit rate constant for the fluorination of U/sub 3/O/sub 8/. A variey of momentum, heat and mass transfer equations were developed for both oxide particles and the gas phase within the flame tower. Equations were developed to estimate the physical and transport properties of each gaseous component and the gas mixture as a whole. These properties and the transport equations were used to estimate the reaction time and distance for oxide particles with both the low and high limit reaction rate constant. The procedures used to perform these calculations is limited to constant temperature and an oxide feed comprised of a single particle size. The results indicate that above 1000/sup 0/F the mass transfer of reactants and products becomes increasingly important to the overall rate of the reaction.

• Research Organization: Goodyear Atomic Corp., Piketon, OH (USA)
• DOE Contract Number: AC05-76OR00001
• OSTI ID: 5808262
• Report Number(s): GAT-E-279; ON: DE85012823
• Country of Publication: United States
• Language: English

Related Subjects

050501* -- Nuclear Fuels-- Uranium Enrichment-- Gaseous Diffusion-- (-1989)
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
ACTINIDE COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
FLUORIDES
FLUORINATION
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
HALOGENATION
MASS TRANSFER
MOMENTUM TRANSFER
OXIDES
OXYGEN COMPOUNDS
PRODUCTION
URANIUM COMPOUNDS
URANIUM FLUORIDES
URANIUM HEXAFLUORIDE
URANIUM OXIDES
URANIUM OXIDES U3O8