In this investigation, attempts are made to fabricate high performance polymer such as polybenzimidazole (PBI) (service temperature ranges from -260 deg C to +500 deg C) by carbon nano fibre dispersed epoxy adhesive and to see its performance under space radiation. The polybenzimidazole sheets are fabricated by high performance nano adhesive i.e., by dispersing carbon nano fibre into the ultra high temperature resistant epoxy adhesive (DURALCO 4703, the service temperature of the adhesive is -260 deg C to +350 deg C) with 5% weight ratio with the matrix adhesive. Prior to fabrication of polybenzimidazole sheet, the surface of the polybenzimidazole is ultrasonically cleaned by acetone followed by its modification through atmospheric pressure plasma. It is observed that polar component of surface energy leading to total surface energy of the polymer increases considerably. Nano adhesive bonding of high performance polymer is exposed to three types of radiations (i) mixed field radiation for 6 hours at a dose rate of 37kGy/hr in the pool of a SLOWPOKE-2 (safe low power critical experiment) nuclear reactor, contributing to a combination of 1% neutron, 3 % proton, 9 % gamma, and 87 % electron radiation, (ii) Co-60 irradiation with 100 % gamma radiation at a dose rate of 4 kGy/hrfor 60 hours and (iii) 100% Neutron Radiation. Tensile lap shear strength reveals that when the polymer surface is modified by atmospheric pressure plasma adhesive bond strength increases considerably. There is further increase in adhesive bond strength when the polymer is fabricated by nano carbon fibre epoxy adhesive. When this nano carbon fibre epoxy adhesive joint is exposed to high energy radiation of mixed field, there is a further increase in adhesive bond strength. However, when the carbon nano fibre dispersed epoxy adhesive joint is exposed to 100 % gamma radiation and 100% neutron radiation, joint strength deteriorates. Therefore, this is possible that mixed field radiation; basically increase the crosslink density of the adhesive resulting in increase in adhesive bond strength and gamma radiation and neutron radiation are detrimental and which could essentially makes chain scission to the basic adhesive and resulting in deterioration of adhesive bond strength. Finally, to understand the behaviour of nano carbon fibre epoxy adhesive bonding of Polybenzimidazole, the fractured surfaces of the joints are examined by scanning electron microscope.