Scaling considerations of experimental post-LOCA steam relief

Experiments have been conducted to determine the nature of the hydraulic interaction between emergency core coolant (ECC) water injected into a cold leg of a pressurized water reactor (PWR) and steam passing through that cold leg during core reflood following a loss-of-coolant accident. Measurements of flow rates, fluid temperatures, and static and differential pressures were made in 1/5 and 1/3 linear scale models of the PWR piping from the steam generator of an intact loop to the break including the pump inlet piping (loop seal), pump, cold leg, reactor vessel annulus, and broken cold leg. The principal conclusion is that the injection section performs as a jet condenser with 45-, 60-, and 75-deg injection; and condensation, but no jet pumping, occurs with 90-deg injection. The results also indicate that total condensation occurred in the cold leg in all tests wherein the water injection rate was sufficient to condense the steam assuming thermodynamic equilibrium. The data suggest that the differential pressure measured in the cold leg across the ECC injection nozzle, the water axial momentum flux, and the steam momentum flux can be combined into appropriate nondimensional groups in order to extrapolate the results to full scale. In addition, the data suggest that the influence of jet condenser stability upon the injection section pressure differential may decrease with increasing system size.