Cavitation occurs when local static pressure of the fluid decreases below the vapor pressure of the fluid at that temperature. Cavitation damage is likely to occur in Fast Breeder Reactors (FBR) at multiple locations viz., pumps, orifices provided in the subassembly feet, slots provided in the grid plate sleeves for storage subassembly etc and necessary design precautions are adopted to avoid/limit cavitation/cavitation damage. Liquid sodium is pumped by large diameter centrifugal pumps and when the coolant passes through the pump, coolant velocity increases and local pressure decreases in local zones of impeller, leading to cavitation. The bubble generated by cavitation implode in regions of pressure recovery, leading to damage to the impellers. In this paper, the prediction of unsteady cavitation characteristics of primary sodium pump (PSP) is carried out using sliding mesh approach. Sliding mesh approach is selected in order to capture the effect of rotor-stator interaction on the cavitation characteristics. The fall in head because of cavitation is predicted for the design speed and flow by running multiple simulations with changing input NPSH values.