The CATHARE code condensation modelling confronted to the TOPFLOW-PTS steady-state experiments

Abstract : During a Loss Of Coolant Accident (LOCA) in a Pressurized Water Reactor (PWR), direct contact condensation (DCC) on a stratified flow may take place in the cold leg when the Emergency Core Cooling (ECC) system injects cold water. The condensation modeling of the system thermal-hydraulic code CATHARE-2 is compared to the experimental results from the new TOPFLOW-PTS tests, tests dedicated to condensation and mixing phenomena in cold leg. This is an opportunity to test and improve the scaling capabilities of the current model of the code. The reference CATHARE condensation model was based on COSI data analysis and was then validated against various experimental data including LSTF and UPTF. This wide validation matrix covers a volume scaling factor from 1/100 to 1, includes both Large Break and Intermediate Break LOCA conditions and is now extended to TOPFLOW-PTS. The present work revisits the physical mechanisms involved at the ECC injection and presents an improved condensation model with better scaling capabilities.