Heat transfer mechanism during rod bundle reflooding

Data from the 161-rod unblocked bundle tests of the FLECHT-SEASET program were analyzed to provide mass and energy balances in the rod bundle during a reflooding period to examine the heat transfer mechanisms above the quench front. Actual qualities in the bundle were calculated based on steam superheat temperature measurements. The equilibrium qualities at these elevations were also calculated based on saturation vapor temperature. Significant differences were observed between the actual and equilibrium qualities due to high superheating of vapor above quench fronts. A method to calculate the quality at just above quench front was developed by coupling mass and energy balances below and above a quench front. The qualities calculated using this method at the steam probe elevations were in good agreements with these calculations using the available vapor temperatures