Fission Gas Bubbles in Uranium-Aluminide Fuels

Formation of fission gas bubbles heretofore has not been observed in uranium-aluminide fuels. Recent irradiations to record high burnups offered a possibility to determine the onset of fission gas bubble formation in this type of fuel. Present experimental evidence suggests that UAl₂, UAl₃, and UAl₄ do not form fission gas bubbles at fission densities of 7 × 10²¹/cm³ of fuel (60% depletion of 93% enriched ²³⁵U), and that pure uranium aluminide is likely to remain free of fission gas bubbles to very high ²³⁵U burnup at any enrichment. However, fission gas bubbles were found in these experimental fuels for the first time, but they were without exception associated with uranium-oxide inclusions that were evidently formed during fuel fabrication.