Synthesis and characterization of sinterable uranium carbide of oxide (UCO)

Synthesis and characterization of sinterable uranium carbide oxide (UCO) have been carried out. First of all, spherical form of uranium carbide gel which contained 1 M uranium, 8% PVA and 1.67 - 83 of C/U ratio was prepared using external gelation process in 8M NH₄OH medium. After that, the gel was calcinated at 350 °C for 4 hours to produce UCO kernel. The UCO kernel was sintered using fluidization method in argon medium with a flow rate of 33.3 ml/min using a fluidized bed. The sintering temperature was varied from 1000 -1150 °C with sintering time of 2 hours, and at 1100 °C temperature the sintering time was varied from 1 - 4 hours. The sintering product obtained was sinterable UCO kernel. The characteristics of the UCO kernel from calcination process and sinterable UCO kernel from sintering process were defined from their chemical and physical properties. The chemical properties included structure analysis of UCO molecule using FTIR spectroscopy method from infrared absorption band of O-U-O, U-O, U-C or C-U-C and carbide of C-C bond at wave number 400 - 4000 cm^-1. The physical properties included density analysis using pycnometer and CCl₄ solution as the solvent, specific surface area, mean pore radius using surface area meter NOVA-1000 and N₂ gas as absorbents, as well as grain diameter of UCO kernel using optical microscopy with a magnification of 50x. The experiment results showed that sinterable UCO kernel can be synthesized from UCO kernel produced from calcination above. The relatively good condition was at temperature of 1100 °C, sintering time of 2 hours and C/U ratio of 4.17. The analysis of the chemical properties showed changes of UCO molecular structure during sintering process followed by shifting of the absorption band of O-U-O bond from 740.6 cm^-1 to 650 cm^-1 and the absorption band of C-C bond that was conjugated with O-U-O bond forming C-C-U bond from 1319.12 - 1543.90 cm^-1 to 1359.82 cm^-1, and the disappearance of infrared absorption band of double bond and triple bond, hydrogen bond and hydroxyl bond in sinterable UCO kernel. The analysis of the physical properties showed changes in the crystal structure of sinterable UCO, accompanied with an increase of the density, changes of the specific surface area, the mean pore radius and grain diameter. The sintered UCO kernel produced at relatively good condition consisted of mixture of UO₂ and UC₂, spherical in form, with fine surface and solid grain diameter of 836 - 954 µm. (author)