Most of the safety criteria for Sodium cooled Fast Reactors (SFR) are local core parameters. Thus, application of 3-D neutron kinetic and thermal-hydraulic coupled codes including detailed modelling of core expansion effects is mandatory for best estimate evaluations of safety margins. A recently published benchmark related to Superphénix offers the opportunity to validate codes and methods for SFR safety assessment. This requires the generation of few-group cross-sections. Since whole core Serpent Monte Carlo models for production of such cross-section libraries would be computationally costly (and the standard 2-D approach may introduce unnecessary large approximations), 3-D models of each sub-assembly type in infinite radial lattice configurations have been created with Serpent. To simplify the handling of temperature dependent geometric changes, a pre-processor for generation of temperature driven expansion of geometry and material densities has been developed and implemented in the GRS core simulator KMACS. These cross-sections are then used to evaluate effective multiplication factors and 3-D distributions of power density using PARCS for different core configurations. The results are compared with the reference calculation and with experimental data provided with the benchmark. In the next step, a simple ATHLET parallel channel open core model has been developed for coupled PARCS/ATHLET first transient test calculations. This paper describes in detail the models and techniques used for the generation of the few-group parameterized cross section libraries, the PARCS model and the ATHLET open core model and first transient test calculations.