To ensure the maximum profit, a nuclear power plant should operate at maximum possible power output. Therefore, the cycle thermal efficiency of the power plant becomes very important. The objective of this work is to optimize the operation of the steam cycle of a nuclear power plant to maximize its efficiency. For this purpose, a thermodynamic model of the complete regenerative-reheat secondary loop of the power plant has been developed along with the steam properties correlations using MATLAB. The model is validated against the available plant data. The optimization problem is formulated and solved to optimally decide the flow rates of extractions from high pressure and low pressure turbines. The efficiency of the power plant has been increased from 34.74 % to 35.35% (from 340 MWe to 346 MWe).