Sodium is used as coolant in Indian fast breeder reactors (FBR’s) to remove the heat generated due to nuclear fission in the reactor core. A quantified sodium flow is envisaged through various flow zones in fuel, blanket and storage flow channels called subassemblies (SA). Reduction of flow in any reactor core SA can decrease the heat transfer and can cause various anomalies in reactor parameters as per their capacity. An independent in situ flow measurement system named as core flow monitoring mechanism (CFMM) is used in prototype fast breeder reactor (PFBR), to measure and ensure the required coolant flow rate through each SA. Eddy current flow meter (ECFM) is used as sensor in CFMM for sodium flow measurement. One CFMM is not capable to reach out all the core SA and hence monitoring the coolant flow rate in all the core SA is not possible. Therefore, two CFMM are used to cover the entire core. The sodium flow rate in fuel SAs (FSA) are measured using CFMM-1 and the coolant flow rates in blanket SA (BSA) and storage SA (SSA) are measured using CFMM-2. The hydraulic testing of CFMM-2 revealed that the sodium velocity at the sensor region ranges from 0.23 to 0.56 m/s. With such a low velocity measurement, it was anticipated that the measurement error using ECFM would be significant. In order to achieve a measurable output, the hydraulic design of CFMM-2 is altered to enhance the velocity at the sensor location. The hydraulic design of CFMM-2 has been optimized using CFD tools and sodium velocity at the sensor region is increased by 105%. The CFD predicted results that are also validated with the 1:1 scale experimental testing using water as simulant.