محمد محمدی

In this thesis, using nodal model we have considered the thermo-hydraulic and dynamic behaviors of the Bushehr nuclear reactor core in its second cycle of fuel loading for two power levels of 70% and 100%. The core has been divided into the 20 radial nodes. The neutronic and thermo-hydraulic ‎equations have been solved in SIMULINK/MATLAB. The time variations of relative neutron density, fuel and coolant temperatures have been computed by insertion of step reactivities /- 0.1 beta eff, /- 0.0001 beta eff into the core. The results show that the relative neutron density is strongly dependent on reactivity feedback. By insertion of a large reactivity, the relative neutron density increases by a factor of 2 within 70 seconds. For low reactivities, the transient behavior of the reactor is relatively smooth.