Nickel is widely used as fcc model material to obtain insight into fundamental mechanisms of radiation damage. This work presents irradiation of high-purity nickel using self-ions at 450°C and fine analysis of dislocation loops in specimens prepared by Focus Ion Beam using Transmission Electron Microscopy. For the first time to our knowledge, a drastic change of both loop nature (vacancy-type in irradiated zones v.s. interstitial-type in unirradiated zones) and loop Burgers vector (1/3<111> and 1/2<110> loops v.s. only 1/2<110> loops) is identified along the implantation direction in irradiated nickel. This change may be attributed to the formation of interstitial <110> crowdions and their long-range 1D migration. A defect-free layer related to the annihilation of vacancy defects by injected atoms is detected. It provides an easy way to identify the injection peak in self-ion irradiated specimens and solid validation for damage calculations.