The electrical production of a Nuclear Power Plant depends on the performance of the Circulating Water System, which works removes the residual heat of the plant according to regulations. Owing to the old age of Ascó's NPP Cooling Towers, which are a part of the Circulating Water System, the performance of this system has been reduced. Consequently, the electrical production of the facility has been decreased and the number of events, which triggers the turbine to trip, have been augmented. The aim of this project is to study the viability of a set of modi cation and improvement proposals of the Cooling Towers. A survey of the current performance of the towers has been carried out. The results of this previous study shows that: On the one hand, the cooling capability of the Natural Draft Tower has decreased around 4 oC from their construction. This deterioration has been intensi ed at a rate of 1 oC/year during the last three years. On the other hand, the performance of the Mechanical Draft Towers has dropped around 2 oC. Thermodynamic models capable to simulate the performance of the Circulating Water System, and the current and proposed Cooling Tower have been developed from the existing and provided data. Because of the e ciency of these systems depends on the Ebro's river and local atmospheric conditions, an annual statistics of these parameters is developed. These quantities have been introduced in the developed model, so an annual estimation of the energetic uprate has been done. Finally, the economical feasibility from the di erent proposals has been studied. From the obtained results, two solutions have been found: One of them is repairing both types of towers, and the second one consists of modifying the Natural Draft Tower and repairing the Mechanical Draft Towers.