Single and multi-tube PCCS condensation heat transfer

Passive containment cooling system (PCCS) is one of the engineered safety systems in economic simplified boiling water reactor (ESBWR). PCCS is made of vertical condenser tubes. Following a loss of coolant accident, the pressurized steam discharged from the reactor and the nitrogen mixture flow into the PCCS condenser tube. The PCCS condenser must be able to remove sufficient energy from the reactor containment to prevent containment from exceeding its design pressure. The efficient performance of the PCCS condenser is thus vital to the safety of the ESBWR. Three different operational modes are possible in the PCCS depending on the non-condensable gas concentration and the pressure difference between the drywell and suppression pool. These are bypass or through flow mode, complete condensation mode, and cyclic venting mode. Series of experiments were conducted in a half length scaled test facility with single tube condensers of nominal diameters 2.54 cm and 5.08 cm and a four tube condenser bundle with full height and 5.08 cm diameter tubes. Data were obtained on condensation heat transfer rate for all three modes of operation of the PCCS. A heat and mass analogy model was developed and was benchmarked with a boundary layer model. The model predictions were compared with experimental PCCS condensation heat transfer rates and the agreement was good.