A measurement of water flow on the Experimental Breeder Reactor II (EBR-II) evaporator down-comers, a measurement of sodium flow on the EBR-II secondary sodium system, and a calibration experiment at the University of Utah Water Research Laboratory are three experiments using the pulsed neutron activation (PNA) technique to determine flow rate. The EBR-II data permit calculation of flow rates and comparisons with instrumentation and the Water Research Laboratory data permit investigation of different weighting schemes for determining the flow rates. The PNA technique is an accurate and convenient procedure that yields flow rates without accompanying system disturbance. Pipe size is not a factor except that corrections may be needed for asymmetry of larger pipes. Accuracy is adequate for most applications and indicates the PNA technique is most useful as a calibration device.