亚化学计量UO2-x燃料芯块的制备机理

亚化学计量UO_2-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UO_2+x+U芯块工艺进行制造。本工作采用UO_2+x+U混合粉末为原料制备了UO_2-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UO_2-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UO_2-x芯块必须在干燥惰性气氛中密封保存。

Fabrication Mechanisms of Hypostichiometric UO2-x Fuel Pellets

Hypostichiometric UO_2-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 UO_2+x pellets. In this paper, hypostichiometric UO_2-x pellets were fabricated from the blends of UO_2+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 UO_2-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 UO_2+x produces O/U ratio of 1.943. Hypostichiometric UO_2-x pellets must be preserved in the sealed chamber full of inert gases.