محمد محمدی

The neutron flux spectrum and the flux distribution are of the most important physical parameters to consider the behavior of the nuclear reactor core. In this thesis, the VVER-1000 Bushehr reactor core (Russian model, V-446) and the PWR-1300 (Biblis B) have been simulated using the MCNPX 2.6 code. The thermal flux, the epithermal flux and the fast neutron flux have been studied using F4 mesh tally. For these reactors, the neutron flux spectrum has been calculated for different energy regions. The results have converged for up to 40 neutron groups. Furthermore, the radial flux and the axial neutron flux have also been computed. Our results show that the radial flux distribution in the Bushehr reactor core is relatively homogeneous. However, the axial neutron flux in the Biblis core is comparatively wide and has a cosine-type shape.