The Once-Through Mode of Steam Generator Reflux Condensation in Loss-of-Coolant Accident Scenarios

The once-through mode of steam generator reflux condensation in the presence of noncondensable gases and/or aerosols in loss-of-coolant accident scenarios is introduced. The plausible severe accident scenarios associated with once-through reflux condensation are analyzed with MELCOR to demonstrate the background and safety significance of this phenomenon. An analytical model for once-through reflux condensation with noncondensables inside one single U-tube is developed using the heat and mass transfer analogy approach. The conditions for partial condensation inside the single U-tube can be determined with this model. The progress of modification to the ARTIST test facility to experimentally study the tube-to-tube nonuniform behavior of once-through reflux condensation inside a U-tube bundle is reported.