亚化学计量UO_(2-x)燃料芯块的制备机理

Fabrication Mechanisms of Hypostichiometric UO_(2-x) Fuel Pellets

亚化学计量UO2-x芯块是一种设计新颖的特殊核反应堆用核燃料,很难采用传统压水堆超化学计量UO2+x芯块工艺进行制造。本工作采用UO2+x+U混合粉末为原料制备了UO2-x芯块,研究了铀粉表面包覆处理方法、铀粉含量、成型压力、烧结气氛等工艺参数对芯块O/U比、烧结密度和微观结构的影响,探讨了UO2-x环形芯块的亚化学计量形成机理。研究表明,当铀粉加入量(质量分数)分别为0、3%、6%时,芯块O/U比分别为2.010、1.991、1.982,平均晶粒尺寸分别为10、15、20μm;当铀粉加入量为50%时,O/U比为1.943,样品发生熔化。亚化学计量UO2-x芯块必须在干燥惰性气氛中密封保存。

Hypostichiometric UO2-x pellets are a novel nuclear fuel used in the special reactors,which is very difficult to be fabricated by the similar processes of the traditional PWR UO2＋x pellets.In this paper,hypostichiometric UO2-x pellets were fabricated from the blends of UO2＋x and metal uranium.The effects of processes such as uranium particle coating process,uranium content,compacting press and sintering atmosphere on the O/U ratio,density and microstructure of the pellets were studied.The hypostichiometric mechanisms were also investigated.The sintered UO2-x pellets with a uranium additive of 0,3% and 6% respectively,have a O/U ratio of 2.010,1.991 and 1.982,with a average grain size of 10,15 and 20 μm;50%U additive into UO2＋x produces O/U ratio of 1.943.Hypostichiometric UO2-x pellets must be preserved in the sealed chamber full of inert gases.