Simulation of a Containment Spray System Test With the European Lumped-Parameter Codes ASTEC and COCOSYS

The presented post-test calculations of the test PACOS Px2.2 performed at Ruhr-Universität Bochum (RUB) regard the predictability of the containment spray system’s effect using the lumped parameter codes ASTEC and COCOSYS. The focus of the calculations is set on the decrease of temperature and pressure in case of severe accident scenarios in light water reactor containments. The comparison of the simulation results to experimental data shows, that pressure and temperature during spraying can be simulated satisfactorily with ASTEC and COCOSYS. While calculating the results of the pressure with high agreement to the experiment, both codes underestimate the temperature more and more with increasing distance along the spray path, as the increasing temperature caused by a moving steam cushion is underestimated. The steam cushion is caused by spray induced convection pushing the warmer atmosphere of the upper test facility compartments into the cooler lower compartments. The temperature increase in the lower zones resulting from the establishing flows cannot be simulated properly, as both codes are not fully capable of calculating the occurring forces between dynamic atmosphere and droplet surface.