Modelling the interaction of primary irradiation damage and precipitates: implications for experimental irradiation of zirconium alloys

Damage to materials by different irradiating particles is typically calibrated using displacements per atom (dpa). However dpa calculations usually neglect additional damage produced from primary interactions of irradiating particles with a bulk material and how localised microstructural features may change these interactions. We investigate how the current standard measures of irradiation damage are affected when the presence and distribution of alloying elements in zirconium alloys is taken into account and show that the difference in primary interactions of neutrons and protons with alloying elements causes differing dpa rates relative to bulk zirconium. As such, using dpa in the matrix to correlate damage between proton and neutron-irradiated samples may imply different damage rates in localised microstructural features and therefore differences in the damage phenomena observed. We argue that when comparing the evolution of microstructural features under different irradiation types, the displacement rate per unit volume may be a more useful measure of damage.