CONDENSATION MODELING FOR ECC INJECTION

During a Loss of Coolant Accident (LOCA) in a Pressurized Water Reacto r (PWR) important condensation phenomena take place in the neighborhoo d of the Emergency Core Cooling (ECC) injection ports. Direct contact condensation has been a central issue for thermal hydraulics codes suc h as CATHARE (Code for Analysis of ThermalHydraulic during an Accident and for Reactor safety Evaluation). The COSI experimental program was developed to simulate and study ECC injection behaviour. ECC injectio n has a strong local effect which requires a specific-modelling. The c ondensation rate is controlled by the turbulent heat transfer in the l iquid. A model directed toward a physical based approach is developed which incorporates the effects of such parameters as jet diameter, con duit size and flow distribution. The predicted and experimental conden sation rates are compared for different test conditions. An experiment al test series was devoted to study the effects of non-condensable gas es on the condensation rate. An analysis of the results and a comparis on with the predicted values is presented. The objective of the presen t study is to describe the physical mechanisms involved at the ECC inj ection, but also to point out some experimental and numerical limitati ons when modelling complex physical phenomena such as direct contact c ondensation.