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Nb is considered a promising candidate as a refractory element due to its high-temperature endurance, excellent thermal conductivity, and compatibility with liquid-metallic coolants in nuclear reactors. In the present study, radiation-based molecular dynamics numerical simulations were conducted in Σ 13, Σ 29, and Σ 85 symmetric tilt grain boundary models for pure Nb specimens. The stochastic high-energy collisions were modeled via large-scale atomic/molecular parallel simulator code to accurately investigate the radiation-induced defects generated in the order of picoseconds at the atomic level. The long-range embedded atom method potential and coulombic repulsive Ziegler–Biersack–Littmark potentials were smoothly overlaid for precise force-field interactions among Nb atoms. To investigate the ability to arrest the radiation-induced damage, the bi-crystal Nb specimens were irradiated at varying magnitudes of primary-knock-on atom (PKA) energies EPKA = 10 20, and 30 keV at temperature regimes 300, 600, and 900 K, respectively. The Frenkel pairs, complex linear defects, distribution of point defects as clusters, rate of defect annihilation, and temperature fluctuations within the displacement cascades of irradiated Nb specimens were comprehensively studied and reported. Here, the Nb-Σ 29 GB model survived with the lowest number of residual defects. Also, the recombination rate of the irradiated Nb specimens increases with the increase in temperature and PKA energy magnitude due to enhanced atomic mobility of the dislodged atoms. Hence, the bi-crystal Nb specimen can be favored for a radiation-tolerant material as structural components in next-generation reactors. [ABSTRACT FROM AUTHOR]