Low temperature sintering technology to UO₂ fuel pellets and its creep properties in high temperature

In this paper, the low temperature sintering technology to UO₂ pellets has been introduced, and we have studied the high temperature creep properties of the pellets which manufactured by low temperature sintering. The sintering temperatures are 1073 K, 1273 K, 1473 K and 1673 K, sintering time are l hour, 2 hours and 3 hours respectively. We obtained the highest sintering density of pellets at 1673 K with 3 hours, which is 10.41 g/cm³ (94.98% theoretical density). The grain size of pellets which prepared by low temperature sintering technology and traditional technology are 9.0 μm and 23.8 μm respectively. So the high temperature creep properties of the two kinds of pellet must be studied. They were performed at 20-50 MPa, 1673 K and 1773 K respectively, under a nitrogen atmosphere to shorten the experimental time. According to the results, the creep rates of sintered UO₂ with the grain sizes of 9.0 μm and 23.8 μm under the load of 10 MPa are almost the same. The creep process is controlled by both Nabarro-Herring creep and Hamper-Dorn creep for uranium dioxide with grain size of 9.0 μm; while Hamper-Dorn creep is the dominant mechanism for uranium dioxide with grain size of 23.8 μm. (authors)