KINETICS AND MECHANISM OF THE OXIDATION OF URANIUM DIOXIDE AND URANIUM DIOXIDE PLUS FISSIA SINTERED PELLETS

Technical Report · Tue Nov 01 04:00:00 EST 1960

OSTI ID:4117332

Smith, T

Oxidation of uranium dioxide sintered pellets with oxygen at 3 to 800 mm Hg, 0 to 450 gas-cooled C and with a 0 to 5% concentration of fission product oxides (fissia) was studied in an effort to elucidate the kinetics and mechanism of the reactions involved. A mechanism is postalated for processes that control the oxidation from UC/sub 2/ to U/sub 3/O/sub 8/ in terms of the following reactions: chemisorption of oxygen on the UO/sub 2/ surface, followed by adsorption of oxygen on the chemisorbed layer STAR/sub 1/ = 5.5 x 10/sup -7/ P exp (-l2,800 2,800/RT) moles O/cm/sup 2/-sec, where P is oxygen pressure in mm Hg!; diffusion through a thin layer (224 74 A) of U/sub 3/O/sub 7/ or U/ sub 4/O/sub 9/ (depending on the temperature) with a diffusion coefficient D = 5.5 x 10/sup -5/ exp (-21,900 1400/RT) cm/sup 2//sec for pure UO/sub 2/ and D = 12.2 x 10/sup -5/ exp (-28,100 1100/RT) cm/sup 2//sec for pellets with fissia; formation of U/sub 3/O/sub 8/ in the grain boundaries, which causes the surface layer to spall off, and thereby pulverize the pellet. (auth)

• Research Organization: Atomics International. Div. of North American Aviation, Inc., Canoga Park, Calif.
• DOE Contract Number: AT(11-1)-GEN-8
• NSA Number: NSA-15-003997
• OSTI ID: 4117332
• Report Number(s): NAA-SR-4677
• Country of Publication: United States
• Language: English

Related Subjects

ADSORPTION
CHEMISTRY
CONTROL
DIFFUSION
FISSION PRODUCTS
FISSIONABLE MATERIALS
OXIDATION
OXIDES
OXYGEN
PELLETS
PRESSURE
REACTION KINETICS
SINTERING
SURFACES
TEMPERATURE
URANIUM DIOXIDE