NUCLEAR FUEL RESEARCH FUEL CYCLE DEVELOPMENT PROGRAM. Quarterly Progress Report, July 1 to September 30, 1960

Technical Report · Fri Nov 11 00:00:00 EST 1960

OSTI ID:4068871

Work was continued on the development of a UO/sub 2/ pellet fabrication process based on low-tempereture sintering in an inert atmosphere. A study of the chemical and physical characteristics of several ADU oxides was carried out to determine the cause of poor sinterability. The properties investigated included (1) particle-size distribution, (2) surface area, (3) microscopic appearance, (4) hydrogen sinterability, and (5) chendcal analysis. No clear distinguishinng difference among the various oxides lots was found, which accounts for the observed variation in sinterability. A program aimed at improving sinterability by activation techniques was initiated. Oxidation- reduction cycling was the most effective. After one cycle, consisting of oxidation to U/sub 3/O/sub 8/ at 500 deg C and reduction to UO/sub 2/ at 525 deg C, all production lot oxides could be densified to st least 95% of theoretical at temperatures not exceeding 1300 deg C. The enhancement of sinterability is so pronounced that such densities were achieved after sintening at as low as 11OO deg C for only 1 hr in nitrogen. High-temperature hydrogen sinterability was similarly improved. Chemical analyses of uranium carbide prepared by the methane reaction indicated that improvements are necessary in the control of heating rate and time at temperature for the carbunizing step to achieve adequate carbon compositional control. The analyses indicated the uranium carbide product was not affected by increasing the carburizing gas flow rats in the retort. Using methane, it appears that the average of nitrogen, oxygen, and free carbon contents are 0.43, 0.77, and 0.25%, respectively. A preliminary study was made of the use of propane for carburizing uranium. The results indicated that the free carbon was slightly higher than that obtained with methane, but thst the nitrogen and oxygen contents were significantly lower, viz., O.O6% nitrogen and 0.22% oxygen. Work on the cold pressing and 1800 deg C vacuum sintening of uranium carbide produced by the methane reaction indicated thst the best densities thst could be achieved by this method with essentially stoichiometric uranium monocarbide were 11.2 to 12.2 g/cm/sup 3/. Nitrogen and oxygen appear to form an isomorphous solid solution in the uranium monocarbide structure and do not appear to enhance the sinterability. It was found that the presence of free uranium is essential and thst approximately 51 at.% or more of uranium must be present in the composition to achieve a high sintered density. Densities approaching the theoretical were obtained when an adequate quantity of free uranium was present, either because of the composition of the product as produced from the methane-uranium reac tion or when adjusted in composition by the addition of uramum in the form of uranium hydride to the powder mixture prior to cold pressing and sintering. Improvements were made in the skull arc-melting and casting technique by utilizing a ten-turn water-cooled coil inserted beneath the crucible in the skull furnace. This provided sufficient magnetic field at 400 amp to prevent arc deflection during melting uranium carbide at 2500-amp melting current. Pelletized uranium oxide-graphite charge materials were reacted and melted in the arc furnace which yielded a uranium monocarbide product contnining 4.71% carbon. 0.084% oxygen, and 0.06% nitrogen. Work was carnied out on the use of pre-reacted uranium oxide graphite mixtures to form a consumable electrode. An electrode, pre-reacted by vacuum-induction heating at 2000 deg C, was consumably arc-melted successfully. (auth)

• Research Organization: Olin Mathieson Chemical Corp., Baltimore
• DOE Contract Number: AT(30-1)-2374
• NSA Number: NSA-15-013431
• OSTI ID: 4068871
• Report Number(s): NYO-2690
• Resource Relation: Other Information: Orig. Receipt Date: 31-DEC-61
• Country of Publication: United States
• Language: English

Related Subjects

METALS, CERAMICS, AND OTHER MATERIALS
AMMONIUM COMPOUNDS
CARBON
CARBURIZATION
CHEMICAL REACTIONS
COILS
COLD WORKING
COMPACTING
CONTROL
COOLING
CRUCIBLES
CURRENTS
DENSITY
DISTRIBUTION
EFFICIENCY
ELECTRIC ARCS
ELECTRODES
FABRICATION
FUELS
FURNACES
GAS FLOW
GRAIN SIZE
GRAPHITE
HEATING
HIGH TEMPERATURE
HYDROGEN
INDUCTION
INERT GASES
LATTICES
LOW TEMPERATURE
MAGNETIC FIELDS
MELTING
METHANE
MIXING
NITROGEN
OSCILLATIONS
OXIDATION
OXYGEN
PELLETS
POWDERS
PROPANE
QUALITATIVE ANALYSIS
QUANTITY RATIO
REDUCTION
SINTERING
SOLID SOLUTIONS
SURFACES
U3O8
URANATES
URANIUM
URANIUM CARBIDES
URANIUM DIOXIDE
URANIUM HYDRIDES
URANIUM OXIDES
VACUUM
W