Radiation protection during transport and storage of irradiated fuel assemblies relies, besides the radiations emitted by the fuel, on the activation of the structural elements of the assembly. This work focuses on the calculational method to be used for the evaluation of the latter contribution. Among different tested hypotheses, the axial burn-up modelling compared to the use of one axial zone, and consequently one fuel composition, was observed to increase significantly the nozzles activation for the PWR assemblies, that is the main focus of this paper.