Open literature data were used to create computer models of the Superphénix sodium-cooled fast reactor (SFR) core and in-vessel structures with two codes: TRACE/FRED (PSI) and SIM-SFR (KIT). In both models 2D heat structures, 1D thermal-hydraulic channels and 0/1D reactor kinetics were used to account for dynamic reactivity feedbacks due to fuel temperature evolution as well as differential thermal expansions of fuel, cladding, sodium, diagrid, strongback, vessel and control rod drivelines. Six Superphénix start-up transient tests were analyzed using dynamic boundary conditions based on the test data for core inlet temperatures, flow rates and control rod position. Good agreement between calculations and measurements for reactor power and outlet temperature were obtained for all six cases using a single reactivity coefficient input data set. This analysis contributes to better understanding of SFR core/primary system dynamic behavior and to validation of the tools currently used for transient analysis of the Generation-IV SFR.