The accelerated development of nuclear technologies to meet rising energy demands requires advanced materials capable of withstanding extreme conditions, such as high temperatures, corrosive environments, and intense radiation. The present study illustrates a novel experimental approach that contributes to understanding the irradiation creep phenomenon by modeling atomic-scale processes. To better predict the irradiation-induced defect formation, in-situ irradiation creep tests were combined with diffusion measurements, ex-situ transmission electron microscopy characterization and internal friction studies. High-purity nickel single crystal samples were exposed to 7.2 MeV proton irradiation at 300, 400 and 500 °C in a unique in-beam creep device. The total dose was 0.22 dpa and the tests were carried out with and without applied uniaxial load. Volume self-diffusion was studied using Ni-64 as tracer isotope. To evaluate the irradiation-enhanced self-diffusion, concentration-depth profiles were obtained using secondary ion mass spectrometry (SIMS). The irradiation-induced defect microstructure was characterized by ex-situ transmission electron microscopy (TEM). Dislocation dynamics were investigated by mechanical spectroscopy (MS) using a forced oscillation pendulum. The focus of the study was on correlating the activation energies for irradiation creep, self-diffusion, and internal friction to gain a deeper understanding of defect transport processes governing irradiation creep. The results indicated that irradiation creep is sensitive to both the external irradiation conditions and the loading direction if studied in terms of creep strain rate. On the contrary, if studied in terms of irradiation creep compliance (B_0), irradiation creep exhibited almost no influence on the loading direction. Nickel self-diffusion mobility parameters were found to be: D_0=5.6x10^(-19) m^2 /s and Q=0.3 eV. Radiation-enhanced diffusion was appreciable, with measured diffusion coefficients at least two orders of magnitude larger than in non-irradiated conditions. Between 300 °C and 500 °C, D_IRR exhibited a low temperature sensitivity, for a displacement rate of 4x10^(-6) dpa/s, which could be attributed to time-dependent sink-concentration effects. Following irradiation at 300 °C, with 50 MPa uniaxial stress, irradiation induced defects in Ni resulted in a high defect density that gave rise to spontaneous recombination and defect agglomeration, leading to the formation of a complex structure of network dislocations, loops, and voids. The internal friction spectrum reveals three mechanical loss peaks, for all the three orientations, namely P0 (transient peak), P1 and P2. P1 and P2, both relaxation peaks, are related to dislocation movement. The activation energies for P1 (1.5 eV) and P2 (1.8 eV), were attributed to the sliding of dislocations controlled by the climbing of jogs along edge and screw dislocations, respectively, driven by pipe diffusion. The identification of the mechanisms underlying irradiation creep provided a detailed understanding of the microstructure-property correlations in nickel single crystals. These findings lay the foundation for future experiments on more complex materials such as stainless steels, high-entropy alloys, or Ni-based superalloys.