Steam Generator Flow Instability Modeling During the Reflood Stage of a Loss-of-Coolant Accident

Steam generator pressure drop versus flow rate instability during a loss-of-coolant accident in a pressurized water reactor has been investigated. The steam generator is simulated by four tubes, each with a different height, on top of a two-dimensional quarter-circle inlet plenum. This work deals with only an adiabatic air-water system. The pressure drop was found to be practically constant in the range of 3 j_g 10 m/s. Within this range, the pressure drop depends only on the liquid flow rate. The plenum details do not matter. A model using an average flow for each tube does a good job in estimating the pressure drop. The flow distribution can be conservatively estimated by the proposed model based on a single, average tube pressure drop minimum.