掺杂Cr2O3对UO2芯块烧结行为的影响

提高燃料燃耗的一个有效手段是通过增大UO₂晶粒尺寸来减少元件内部气体压力，在大晶粒UO₂芯块中，裂变气体到达晶界表面的距离增加，因而裂变气体的释放速率降低，元件内部气体压力的增高缓慢。本文研究了添加Cr₂O₃对UO₂晶粒尺寸的影响。对纯UO₂、添加0.5% Cr₂O₃及5% Cr₂O₃ 3种配方的芯块进行了试验，在5%H₂Ar保护下，以10 ℃/min和5 ℃/min的升温速率升温至1 700 ℃，然后烧结2 h或4 h，对比纯UO₂芯块与添加Cr₂O₃的芯块发现，添加Cr₂O₃可有效增大晶粒尺寸；较长的烧结时间可促进晶粒长大；较低的升温速率也使晶粒长大。烧结过程产生液相烧结，液相浸润晶粒边界，促进晶粒长大。

Effect of Doped Cr2O3 on Sintering Behavior of UO2 Pellet

A way to increase burnup is to diminish the elements internal pressure by an adequate large grain UO₂ pellet structure. In the large grain size UO₂ pellets, fission gas release rate decreases and the element internal pressure increases slowly. The effects of Cr₂O₃ on grain size of UO₂ pellets were investigated in this work. Pure UO₂, doped 0.5% Cr₂O₃ and doped 5% Cr₂O₃ pellets were studied, in the atmosphere of 5%H₂Ar, it was going up to 1 700 ℃ at the heating rate of 10 ℃/min and 5 ℃/min, then sintered for 2 hours or 4 hours. Results show that the grain size of pellets doped Cr₂O₃ increases compared with pure UO₂ pellets. Lower heating rate and longer sintering time can also promote grain growth. The sintering process produces liquid phase sintering, which infiltrates grain boundaries and promotes grain growth.