Numerical sensitivity study of irradiated nuclear fuel evolution in the RBMK reactor

The sensitivity study of the RBMK-1500 spent nuclear fuel (SNF) nuclide composition modelling was performed by investigating the essential physical reactor performance parameters (influence of coolant density, fuel and graphite temperatures, the fuel irradiation history, axial fuel assembly power profile) and specific model parameters depending on the computational code (model geometry description, neutron flux convergence criteria, evaluated nuclear data libraries and energy intervals used, resonance self-shielding parameters, etc.).SNF nuclide composition modelling was performed by using T-DEPL sequence from the SCALE 5 code package.The study showed that some of analysed parameters can influence the calculated SNF nuclide composition significantly, especially for minor actinides and fission products with high neutron capture cross-sections.It has been found that the coolant density and axial power profile have the largest influence on irradiated fuel inventory and in order to obtain the more precise RBMK-1500 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 significant effect on calculated actinide activities.The correct parameter could be obtained from the experimental data that are presently unavailable.