The Indian Pressurized Heavy Water Reactor (PHWR) comprises of a number of horizontal channels containing nuclear fuel bundles. The parallel channels are connected to headers at the inlet and outlet through feeder pipes. The carbon steel outlet feeders carry high temperature water to the headers and from headers, high temperature water goes to steam generator where steam is produced. Due to high velocity and high pressure and temperature, feeders are liable to undergo flow accelerated corrosion (FAC). Recent inspections of outlet feeder pipe showed measurable wall thinning due to flow accelerated corrosion at locations close to the end fitting. The FAC problem is also prevalent in the secondary side of nuclear power plants as well as in the conventional power plants. FAC is a process in which the normally protective oxide layer on carbon or low-alloy steel dissolves into a stream of flowing water or a wet steam mixture. In this process, the oxide layer becomes thinner and the corrosion rate increases until the oxide formation rate and its dissolution rate are equal. This result in the removal of oxide layer at the rate it is getting formed thereby losing the underlying metal. The rate is dependent on the velocity of the flow. In some cases, the oxide layer becomes very thin as to expose an apparently bare metal surface. There are three popular codes e.g. WATHEC/DASY, CHECWORKS/CHECUP and BRT-Cicero available to predict the FAC rates. Out of these WATHEC/DASY is based on the KWU-KR model.

           This paper presents the results obtained for few reported FAC cases using this model. It is seen that this model does not always predict the corrosion rates accurately. The phenomenon of FAC is complex and is a function of metallurgical, environmental and hydrodynamic factors. Hydrodynamic factors are often ignored in the analysis of corrosion kinetics, or hydrodynamic regime used does not effectively simulate the environment of interest. The hydrodynamic parameters studied are the wall shear stress and flow velocities under single phase flow for different geometric configurations. The paper also presents the study for estimation of corrosion rates based on wall shear rates. Wall shear stress has been evaluated for steam inlet elbow and for an experimental facility. Location of maximum wall shear stress is depends upon the inlet and out let flow condition. Standard k ε turbulence model with wall function has been used. Non-uniform mesh which is fine near the walls and coarse in the centre was generated. Mesh independence test were done for all the cases. The velocity profile prevailing along the length of the bend and wall shear stresses have been obtained using CFD code. The wall shear stress was found to be maximum at the inner radius of the bend for the developed flow condition. The wall shear stress data may be used to predict the corrosion rate by using empirical correlations for which a detail experimental data should be available.