1. A method for analysing at least one fuel rod comprising a stack of nuclear fuel, a rod comprising packed zones completely filled with fuel and intermediate zones partially full of fuel, the method comprising the following steps: acquiring a count profile associated with a non-migrating isotope, a profile being made up of spectrometry measurements taken along the rod for this isotope; determining a set of at least one indicator K_i that makes it possible to quantify the reduction in material at an intermediate zone of index i, the said indicator being deduced from the count profile; detecting the change in geometry by comparing the set of at least one indicator K_i against a set of at least one reference value RK indicative of the initial geometry of the nuclear fuel stack.