SWAGING OF URANIUM DIOXIDE. Annual Report No. 2, July 1, 1961-June 30, 1962

Technical Report · Tue Jul 31 04:00:00 EDT 1962

OSTI ID:4717887

Frigerio, G

The reproducibility of data obtnined for the vibroswaging process for UO/ sub 2/ was studied. The fabrication process investigated was the following: pneumatical vibration (4 minutes duration) to reach a UO/sub 2/ density of approximately 84% of theoretical followed by a relatively small reduction of the fuel rod total area (approx. 18%) obtained by two passes through the swager without intermediate annealing. The Spencer fused UO/sub 2/ powder was used with the following ternary mixture: 67.5% (-6+ 20); 12.5% steel and Zircaloy-2 cladded rods of reactor length (125 to 190 cm) were fabricated. For both stainless steel and Zircaloy-2 rods the reproducibility of the UO/sub 2/ average density was (92.5 plus or minus 0.5)% T.D. Spread of density values along the rod lengih referred to the average density was was plus or minus 1.3 cm or better. The behavior of weldrawn stainless steel tubing was found to be as sntisfactory as the behavior of the more expensive seamless tubing. In one lot of fused UO/sub 2/ the fragmentation behavior was found to be such that it was not possible to obtain densities higher than 90% of theoretical. A preliminary investigation of the use of ceramic grade powder and of ceramic grade-fused UO/sub 2/ mixtures for swaging annealing experiments furnished UO/sub 2/ densities too low (less than 80% T.D.) to be of interest as an alternntive to vibro-swaging process of fused UO/sub 2/. A study of the influence of the diameter-to-thickness ratio on the cold swaging of Zircaloy cladding UO/sub 2/ rods confirmed that tubes with higher D/sub 0//T ratios rupture with fewer passes through the swager. No cracks in Zircaloy2 tubes were observed for reductions of total area lower than 20%. Collateral work was performed on the swaged UO/sub 2/ bar testing. Main items were: fragmentation behavior of fused UO/sub 2/ during vibration and swaging and thermal conductivity of swaged UO/sub 2/. Typical data on fragmentation behavior of fused UO/sub 2/ vibrationally compacted to 84% T.D. and swaged to 92.8% T.D. are given. A stationary'' technique was chosen for measuring the thermal conductivity of swaged UO/sub 2/. The method required a known heat source situated in an axial position along the certer of the swaged bar to insure a radial heat flux. Thermocouple measurements at various known distances from the center of the rod made it possible to calculate the thermal conductivity. Assuming as a comparison base the values reported by Deem and Lucks for UO/sub 2/ pellets, the thermal conductivity values for swaged UO/sub 2/ seemed to remnin lower by approximately (25+0 -10)% than the thermal conductivity values for peliets at the same density (90% T.D.) and at temperatures between 150 and 800 deg C. Additional studies were performed on the porosimetry of swaged UO/sub 2/, roughness of cladding internal surfaces, hardness of cladding, and thermal cycling of swaged UO/sub 2/ rod samples between room temperature and 800 deg C. A preliminary analysis of economic potentials of swaged UO/sub 2/ fuel was performed by comparing a typical power plant core made up of pelletized fuel with nine different swaged cores. The maximum net saving, among the cases considered, amounted to approximately 4% of the entire core cost. The effect of variation of linear specific power, burnup level and cladding-to-fuel weight ratio were analyzed in the cost comparison study. The estimation of breakeven points showed that the burnup level is a more important variable than the linear specific power. (auth)

• Research Organization: FIAT. Sezione Energia Nucleare, Turin
• NSA Number: NSA-17-011164
• OSTI ID: 4717887
• Report Number(s): EURAEC-412; FN-E-25
• Country of Publication: United States
• Language: English

Related Subjects

ANNEALING
BURNUP
CERAMICS
COATING
COLD WORKING
CONFIGURATION
CRACKS
DENSITY
ECONOMICS
FABRICATION
FAILURES
HARDNESS
HEATING
HIGH TEMPERATURE
MACHINING
MEASURED VALUES
METALS, CERAMICS, AND OTHER MATERIALS
PELLETS
PNEUMATICS
POROSITY
POWDERS
POWER
POWER PLANTS
REACTOR CORE
RODS
STAINLESS STEELS
SURFACES
TEMPERATURE
THERMAL CONDUCTIVITY
THERMAL STRESSES
THERMOCOUPLES
TUBES
URANIUM DIOXIDE
VARIATIONS
VIBRATIONS
ZIRCALOY