Modelling zirconium growth under irradiation is a difficult task due to the different types of defects formed which all contribute to the macroscopic deformation. An Object Kinetic Monte Carlo model parameterized using state-of-the-art atomic-scale calculations and experimental data is presented. It is able to reproduce a good macroscopic deformation, the coexistence of all types of defects: 〈a〉 interstitial and vacancy loops, 〈c〉 vacancy loops and the alignments of 〈a〉 loops parallel to the basal plane. A large parametric study is performed in order to understand thoroughly in which conditions these microstructural features can be observed. The model is then applied to study flux effects and the microstructure evolution during annealing. It can be concluded that 〈a〉 loop alignments are phenomena which are very sensitive to the flux. During annealing, the defects can recover in a non-monotonous way and 〈a〉 loops inside the alignments disappear at last, which illustrates their strong stability.