Study of Agglomerated Defects in Irradiated Pure Nickel by Electron Microscopy

Pure nickel foils are neutron and electron irradiated. In both cases black dots are observed by electron microscopy. After neutron irradiation at 77 °K and subsequent annealing at room temperature the larger dots are found to be interstitial Frank dislocation loops. The smaller ones (<15 Å) are vacancy agglomerates in the form of tetrahedral voids. Investigation of dose dependence and further annealing is also presented. After electron irradiation at 10 °C only interstitial Frank dislocation loops are visible for doses larger than 4 × 10 19 electrons/cm 2 at 2 MeV. Discussion of nucleation and agglomeration of free interstitials is presented, showing that the elastic interaction between loops plays an important role.