INVESTIGATION OF THE LIQUID FLOWRATE EFFECT ON THE REWETTING RATE

Following a Loss-of-Coolant Accident (LOCA) in a water cooled nuclear reactor, process of fundamental importance is the rewetting of the overheated fuel elements by an Emergency Core Cooling System (ECCS). It is well accepted that the rate of advance of the wet front depends upon several parameters, the most important being the initial temperature of the overheated fuel elements cladding, the system pressure, the heat transfer coefficient at the wet front, and the properties of the cladding. The effect of secondary parameters, such as the quenching liquid subcooling and flowrate, and the precursory cooling ahead of the wet front due to the droplet-vapor mixture, are still under investigation. The present work is a detailed statistical analysis of available experimental data. It uses the method of confidence interval ellipses, to investigate the liquid flowrate effect on the rewetting rate. The results of this analysis show that the rewetting rate increases with the liquid flowrate only when the wet front advances in an open air environment at atmospheric pressure, while it remains unaffected in a vapor environment at relatively high pressures.