Dissolution rates of uranium dioxide sintered pellets in nitric acid systems

Journal Article · Tue Jan 01 04:00:00 EST 1963 · Journal of Applied Chemistry

DOI:https://doi.org/10.1002/jctb.5010130106· OSTI ID:4688140

Taylor, R. F.; Sharratt, E. W.; De Chazal, L. E. M.; Logsdail, D. H.

The dissolution process for sintered UO₂ into HNO₃ falls into two regimes of behavior that depend on the overall transfer rate. The critical dissolution rate is approximately 8 mg cm^-2 min^-1, its precise value depending upon the solvent composition. Below this critical value there is a large degree of chemical kinetic control, the dissolution rate being proportional to the cube of nitric acid concentration, the experimental activation energy being 15 kcal mole^-1. Above the critical value the process appears to be controlled by the diffusion of a nitric acid species as the transfer rate is directly proportional to acid concentration with an activation energy of about 4 kcal mole^-1. In addition, the reactor is autocatalyzed by the nitrite product so that forced convection can reduce rates by a factor of four times, and nitrite neutralizers can reduce them by a factor of one hundred times. To a first approximation the dissolution rate depends simply on the total nitrate concentration although polyvalent nitrates and, in particular, ferric nitrate, tend to accelerate the reaction. (Uranium Abstr., Vol. 2, No. 4, May 1962)

• Research Organization: Atomic Energy Research Establishment, Harwell, Berks, Eng.
• Sponsoring Organization: USDOE
• NSA Number: NSA-17-027338
• OSTI ID: 4688140
• Journal Information: Journal of Applied Chemistry, Journal Name: Journal of Applied Chemistry Journal Issue: 1 Vol. 13; ISSN 0021-8871
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
CATALYSIS
DIFFUSION
EXCITATION
IRON NITRATES
LATTICES
NITRATES
NITRIC ACID
NITRITES
PELLETS
REACTION KINETICS
REACTORS
SINTERED MATERIALS
SOLUTIONS
SOLVENTS
URANIUM DIOXIDE