This study presents core calculations of the Molten Salt Fast Reactor using different codes. The KENO (one of the SCALE package) code was used at the beginning to calculate the multiplication factor Keff for the benchmark design. After that, the TRITON (one of the SCALE package) was used to find the nuclear constants for the different regions of this design. These nuclear constants were used in the multi-physics code COMSOL to model the reactor and calculate the neutron flux Eigen values of the neutron diffusion equation and then calculate the multiplication factor Keff and get the neutron flux distribution. This distribution was used to make a coupling between the neutronic and the thermal hydraulic of the reactor. The nuclear codes MCNP5 and WIMS were also used in modelling this reactor to calculate Keff. The study showed the differences between the multiplication factor values from each code and compared them by the values from old reference studies and reflected the effect of the selection of the data libraries and the code on the results. It showed also the thermal hydraulic results for the benchmark as modelled by COMSOL.