“…A novel collimated densitometry technique was proposed in Ref. (Senis et al, 2021) to investigate the variation of density in nuclear fuel samples post-irradiation, which typically decreases as a consequence of swelling (Schrire et al, 1998;Daniel et al, 1962;Van Brutzel et al, 2015). In the study, a resolution in the order of a hundred microns is aimed to resolve the density variation of the fuel matrix in the rim region where, due to the "high burnup structure" (Rondinella and Wiss, 2010;Spino et al, 1996), a drop in the density up to tens of percent could be expected (Spino et al, 2005).…”