Sintering studies on UO2–PuO2 pellets with varying PuO2 content using dilatometry

The sintering behaviour of UO2, PuO2, UO2–20%PuO2, UO2–50%PuO2 and UO2–76%PuO2 pellets have been studied using a dilatometer in inert, reducing and oxidizing atmospheres. The onset of shrinkage occurs by about 400°C lower in oxidizing atmosphere such as CO2 and commercial N2 than that occurs in reducing atmosphere. PuO2 and UO2–76%PuO2 showed an expansion on heating in Ar at ∼1000°C. UO2–20%PuO2 pellet sinters slightly better in Ar than in Ar–8%H2. From the shrinkage rate curves, it was found that the maximum shrinkage rate occurs in commercial nitrogen atmosphere for UO2–50%PuO2. For the other compositions, the maximum shrinkage rate was observed for Ar atmosphere. The sintering behaviour of above mentioned pellets was discussed with the help of point defect model and the possible mechanisms were suggested.