The direction to enhance the electrical, dielectrica and mechanical characteristics of insulating materials used in cables has become essential in order to plan new insulation systems used in the nuclear power plant. The current study is to investigate the improvement in these properties of Cross-linked polyethylene (XLPE) due to the addition of clay nanoparticles. The XLPE/Clay-Nanocomposites, with different weight fragments of nanoparticles up to 5 %, were fabricated using the mixing of XLPE with the aid of nanoparticles dispersion within the melted polymeric matrix. The irradiation experiment was performed on both the pure XLPE cable insulation and the filled one, by using 60 Co gamma-ray source with an irradiation dose rate of 1.87 KGy/h at 50 o C temperature of the chamber. The surface morphology of synthesized XLPE / Claynanocomposites was characterized by Scanning Electron Microscopy (SEM) and the dielectric and mechanical properties were measured. It is found that the breakdown strength of XLPE / Clay was increased with incorporating clay nanoparticles into their matrix compared to that case of unfilled XLPE. This reveals that XLPE / Clay-nanocomposites had better electrical properties, 1 % was found the optimal loading fraction of clay nanoparticle. This may be referring to the low surface energy of the clay nanoparticles that prevented the agglomeration of nanoparticles and repressed the free space charges resulting in a decrease in the capacitance and losses inside the nanocomposites. Furthermore, both electrical capacitance and dielectric constant are increased by about 20%, for the XLPE / Clay at 50 KGy compared to pure XLPE at 1% (the optimal loading fraction). Also, it is found that the optimal loading fraction of clay nanoparticle is 4% for improved mechanical properties in XLPE cable insulation.