The sensitivity study of the RBMKn1500 spent nuclear fuel (SNF) nuclide composition modelling was performed by investigating the essential physical reactor performance parameters (inuence of coolant density, fuel and graphite temperatures, the fuel irradiation history, axial fuel assembly power prole) and specic model parameters depending on the computational code (model geometry description, neutron ux convergence criteria, evaluated nuclear data libraries and energy intervals used, resonance self-shielding parameters, etc.). SNF nuclide composition modelling was performed by using TnDEPL sequence from the SCALE 5 code package. The study showed that some of analysed parameters can inuence the calculated SNF nuclide composition signicantly , especially for minor actinides and ssion products with high neutron capture cross-sections. It has been found that the coolant density and axial power prole have the largest inuence on irradiated fuel inventory and in order to obtain the more precise RBMKn1500 SNF nuclide composition these parameters should be modelled as close to real conditions as possible. The lattice cell pitch used for resonance self-shielding can have a signicant effect on calculated actinide activities. The correct parameter could be obtained from the experimental data that are presently unavailable.