Re-sintering behavior in oxidatively sintered UO2 and UO2-5wt.% CeO2 pellet

The cause of solarization was analyzed when sintered pellet as UO2 and UO2-5wt.%CeO2 was re-sintered after oxidation sintering and reduction sintering. Two types of powder, AUC-UO2 and IDR-UO2 were used for the analysis. Having variation of pelletizing density and O/U ratio and performing sintering with a method of H2-CO2-H2 in addition to CO2(sintering)-H2(reduction), which was a normal oxidation condition to prevent for CO2 gas to be trapped in sintered pellet, it was observed that how sintered pellet sample with or without CO2 trap affected re-sintering behavior. Variation of pelletizing density did not noticeably influence solarization changes, and IDR-UO2 having smaller powder particle size had relatively larger solarization changes than AUC-UO2 powder. When O/U ratio was greater than 2.0 the solarization change was higher. And sintered pellet without captured CO2 gas showed the higher density by re-sintering process. Under the reducing environment sintered UO2 pellet also had higher density after re-sintering process. (Hong, J. S.)