While the evolution of irradiation-induced dislocation loops is well correlated with irradiation-induced growth phenomena, the effect of alloying elements on this evolution remains elusive, especially at low fluences. To develop a more mechanistic understanding of the role of Fe on loop formation, state-of-the-art techniques have been used to study a proton-irradiated Zr-0.1Fe alloy and proton-and neutronirradiated Zircaloy-2. The two alloys have been irradiated with 2 MeV protons up to 7 dpa at 350 °C and Zircaloy-2 up to 14.7 x10 25 n m-2 , ~24 dpa, in a BWR at ~300 °C. Baseline TEM characterisation showed that the Zr 3 Fe secondary phase particles in the binary system are larger and fewer in number than the Zr(Fe, Cr) 2 and Zr 2 (Fe, Ni) particles in Zircaloy-2. Analysis of the irradiated binary alloy revealed only limited dissolution of Ze 3 Fe suggesting little dispersion of Fe into the matrix while at the same time a higher a-loop density is observed in comparison to that in Zircaloy-2 at equivalent proton dose levels. It was also found that the redistribution of Fe during irradiation leads to the formation of Fe nanoclusters. A delay in the onset of c-loop nucleation in proton-irradiated Zircaloy-2 compared to the binary alloy was observed. The effect of Fe redistributed from secondary phase particles, due to dissolution, on the density and morphology of a-and c-loops is described. The implication this may have on irradiation-induced growth of Zr fuel cladding is also discussed.