During a Loss of Coolant Accident (LOCA) in a Pressurized Water Reactor (PWR) important condensation phenomena take place in the neighborhood of the Emergency Core Cooling (ECC) injection ports. Direct contact condensation has been a central issue for thermalhydraulics codes such 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 injection has a strong local effect which requires a specific modelling. The condensation rate is controlled by the turbulent heat transfer in the liquid. A model directed toward a physical based approach is developed which incorporates the effects of such parameters as jet diameter, conduit size and flow distribution. The predicted and experimental condensation rates are compared for different test conditions.
An experimental test series was devoted to study the effects of non-condensable gases on the condensation rate. An analysis of the results and a comparison with the predicted values is presented.
The objective of the present study is to describe the physical mechanisms involved at the ECC injection, but also to point out some experimental and numerical limitations when modelling complex physical phenomena such as direct contact condensation.
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