Carbon steel feeders of the primary coolant system of PHWRs under goes significant wall thinning due to flow accelerated corrosion(FAC). This is a cause of concern as the rate of flow accelerated corrosion in certain locations and certain operating parameters exceeds the corrosion allowance assumed during design. It calls for frequent wall thinning measurement and mid course enmasse replacement, of feeders. Hence, the phenomenon of wall thinning occurring in the carbon steel feeder pipes is being investigated in detail. FAC occurring in the primary coolant system is different from that happens in the secondary coolant system as the coolant chemistry, temperature, steam content and pressure conditions are different. It has been reported that extrados of first bends/elbows of carbon steel outlet feeders undergo maximum wall thinning. However, several contradicting observations on the clock position in which maximum thinning takes place led many to carry out modeling of the coolant flow in the various geometries to which feeder pipes had been erected and to carry out experiments under simulated PHWR primary coolant system conditions to validate the results of computer modeling.        Velocity profile prevailing within a bend and the wall shear stress variation along the bend were mapped using computer modeling which had shown that maximum velocity and wall shear stress prevails in the intrados of the bend. Thus, it is expected that the intrados of the bend corrodes at a faster rate as compared to the extrados of the bend. Hence, in order to resolve various issues on the FAC of feeders of PHWRs, experimental measurement of FAC rates of materials was carried out. A FAC specimen module was designed, fabricated and installed in a high temperature high pressure system that is operated under PHWR PHT system conditions. The FAC specimen module containing a bend specimen in the form of rings and rectangular specimen to simulate the straight section of pipe is being modified to extract information relating to the exact position of attack. Thin layer activated metal sections are inserted in the ring specimen so as to find the exact location of attack. Activation of carbon steel section was carried out by proton bombardment using an accelerator and the 57Co formed is used for insitu wall thinning measurement.        Full primary coolant system of PHWRs are decontaminated using Dilute Chemical Decontamination (DCD) process operated under regenerative mode. In order to fully account for the total wall thinning observed in PHWR primary coolant feeders, the contribution of wall thinning occurring during full system chemical decontamination has to be ascertained. Experimental measurement of flow accelerated corrosion occurring under chemical decontamination conditions is being carried out. A special specimen holder assembly has been fabricated and installed in a decontamination process simulating system and measurement of FAC rates of carbon steel is being carried out.        The experimentally measured FAC rates at different geometrical positions of a bend under simulated operating conditions was compared with the bend specimens collected from a PHWR primary coolant system. The results of comparison are discussed in detail in this paper.