Inconel 600, a Ni-based alloy was considered as a possible replacement for austenitic stainless steels for service at high temperatures in nitrogen containing atmosphere of the neutron detector. To obtain a fundamental understanding of the differences in the diffusivity of nitrogen in pure Fe and Ni lattices, molecular dynamics simulations were carried out. Based on the simulation of nitrogen trajectories in the temperature range of 1200–1400 K, pre-exponential factor, activation energy and jumping frequency were calculated and compared for fcc Ni and Fe. MD simulations confirmed that rate of diffusion of nitrogen is lower in Ni when compared to Fe, suggesting the replacement of austenitic steel with Inconel 600 for better performance of the detectors.