二氧化铀芯块的低温烧结工艺与高温蠕变研究

Low Temperature Sintering Technology to UO_2 Fuel Pellets and Its Creep Properties in High Temperature

介绍二氧化铀芯块的低温烧结技术，研究使用低温烧结技术所制备芯块的高温蠕变性能。试验中芯块的烧结温度分为1073、1273、1473、1673K，烧结时间为1、2、3h。烧结温度为1673K，烧结时间为3h时，获得的的芯块烧结密度最大，密度为10．41g／cm^3。由低温烧结工艺获得的芯块晶粒尺寸为9．0μm，而采用传统工艺制得的芯块晶粒尺寸达到23．8μm。在应力20-50MPa，温度1673K和1773K，氮气氛保护的条件下进行蠕变试验，研究这2种芯块的高温蠕变性能。由试验结果可知，在堆芯环境下（10MPa应力）2种晶粒尺寸的芯块蠕变速率有一定差异，比值约为3。晶粒尺寸9．0μm的芯块其蠕变速率可以由Nabarro．Herring和Harnper-Dom~型计算，而晶粒尺寸23．8“m的芯块其蠕变速率可以由Hamper-Dom模型计算。

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 1 hour, 2 hours and 3 hours respectively. We obtained the highest sintering density of pellets at 1673K 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 9.0μm 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 Ixm and 23.8 Ixm under the load of 10MPa 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 μ; while Hamper-Dorn creep is the dominant mechanism for uranium dioxide with grain size of 23.8 μm.