The role of UC inclusions in the development of fission gas bubble superlattice neutron-irradiated monolithic U-10Mo fuels

Uranium Carbide (UC) inclusions are the most prevalent impurities in Uranium-Molybdenum (U-Mo) fuel and are considered undesirable because they could potentially affect fuel performance. This work revealed that, like grain boundaries, UC inclusions could help facilitate the formation of the fission gas bubble superlattice (GBS). The GBS is a highly organized complex defect structure that can effectively store fission gases, thereby inhibiting fuel swelling. Transmission electron microscopy (TEM) showed that GBS self-organization can initiate at the UC/U-Mo interfaces in U-10Mo fuel irradiated to low fission density. This study also revealed that the UC/U-Mo phase boundary in U-10Mo irradiated to low fission density is wavy and periodic in morphology and that GBS formation is semi-coherent with the UC boundary. Because the initiation of GBS preferentially occurs at grain boundaries and UC/U-Mo phase boundaries, it is expected that following GBS collapse at higher fission densities, high burnup structure development may initiate first at grain boundaries and UC/U-Mo interfaces.

碳化铀（UC）夹杂物是铀 - 钼（U - Mo）燃料中最常见的杂质，并且被认为是不利的，因为它们可能潜在地影响燃料性能。这项工作表明，与晶界一样，UC夹杂物有助于促进裂变气体泡超晶格（GBS）的形成。GBS是一种高度有序的复杂缺陷结构，能够有效储存裂变气体，从而抑制燃料肿胀。透射电子显微镜（TEM）显示，在辐照到低裂变密度的U - 10Mo燃料中，GBS的自组织可以在UC/U - Mo界面处开始。这项研究还表明，在辐照到低裂变密度的U - 10Mo中，UC/U - Mo相界在形态上是波浪状且周期性的，并且GBS的形成与UC边界是半相干的。由于GBS的起始优先发生在晶界和UC/U - Mo相界处，因此预计在更高裂变密度下GBS坍塌之后，高燃耗结构的发展可能首先在晶界和UC/U - Mo界面处开始。