[en] The melter feed system is the last leg in the DWPF process. Slurry from the melter feed tank (MFT) is fed continuously to the melter by two parallel feed systems, each system having a nomina feed rate of 0.45 gpm. Each feed system can provide flow rates between 0.2 and 0.9 gprn. The acceptance criteria for the melter feed controllers is a maximum deviation from the desires fee flow rate of +0.25 and -0.10 gpm. Some recent tests of the DWPF melter feed systems have failed this criterion. Steady-state hydraulic models of the melter feed systems have been developed to help understand the hydraulic behaviors of the two systems. Test results and model results indicate that entrained air in the feed systems is probably the cause of control problems with the systems. This cannot be stated categorically since the models are single-phase, and the dynamic behavior is not modelled, but a compelling case can be made that there is entrained air in the systems, and it affects system performance. There are the operating characteristics of the two melter feed systems. System No. 1 return flow at the bottom of the tank through a dip tube, and system No. 2 return flow at the top of the tank. The dip tube on system No. 1 is the major geometric difference between the two systems. Model results indicate that there is a pocket in the dip tube, and therefore the dip tube serves to carry entrained air in the melter feed loop down to the bottom of the MFT. This hypothesis is supported by a simple drift-flux analysis of the flow in the dip tube, and the logical conclusion is in the balance the impact of the dip tube on melter feed system performance is adverse