Zirconium alloys with niobium have an extensive application in the nuclear industry, especially in fuel cladding. In this study, we consider the lattice structure of Zr-1%Nb alloy and study the damage depth (DD) due to irradiation on the structure of this alloy which results from the collision cascade (CC) phenomenon. It has been shown that the DD in the structure is directly related to Primary Knockedon Atom (PKA) energy. Because the structure of Zr-1%Nb is not homogeneous, DD is highly affected by the incident direction of irradiation. Both Zr and Nb atoms were considered as PKA’s and the results show that the average of DD is larger for Nb than Zr. Next, the CC phenomenon has been considered for this alloy and the microstructure evolution has been studied at low temperature and low PKA energy. The results show the formation of some self-interstitials (SI’s) during the CC phenomenon and no SI
clusters have been observed.