  U-10Zr-based metallic nuclear fuel is a promising fuel candidate for
next-generation sodium-cooled fast reactors.The research experience of the
Idaho National Laboratory for this type of fuel dates back to the 1960s. Idaho
National Laboratory researchers have accumulated a considerable amount of
experience and knowledge regarding fuel performance at the engineering scale.
The limitation of advanced characterization and lack of proper data analysis
tools prevented a mechanistic understanding of fuel microstructure evolution
and properties degradation during irradiation. This paper proposed a new
workflow, coupled with domain knowledge obtained by advanced post-irradiation
examination methods, to provide unprecedented and quantified insights into the
fission gas bubbles and pores, and lanthanide distribution in an annular fuel
irradiated in the Advanced Test Reactor. In the study, researchers identify and
confirm that the Zr-bearing secondary phases exist and generate the
quantitative ratios of seven microstructures along the thermal gradient.
Moreover, the distributions of fission gas bubbles on two samples of U-10Zr
advanced fuels were quantitatively compared. Conclusive findings were obtained
and allowed for evaluation of the lanthanide transportation through connected
bubbles based on approximately 67,000 fission gas bubbles of the two advanced
samples.
