Modelling of water sump evaporation in a CFD code for nuclear containment studies

► We model sump evaporation in the reactor containment for CFD codes. ► The sump is modelled by an interface temperature and an evaporation mass flow-rate. ► These two variables are modelled using energy and mass balance. ► Results are compared with specific experiments in a 7 m3 vessel (Tonus Qualification ANalytique, TOSQAN). ► A good agreement is observed, for pressure, temperatures, mass flow-rates. During the course of a hypothetical severe accident in a pressurized water reactor (PWR), water can be collected in the sump containment through steam condensation on walls and spray systems activation. This water is generally under evaporation conditions. The objective of this paper is twofold: to present a sump model developed using external user-defined functions for the TONUS-CFD code and to perform a first detailed comparison of the model results with experimental data. The sump model proposed here is based on energy and mass balance and leads to a good agreement between the numerical and the experimental results. Such a model can be rather easily added to any CFD code for which boundary conditions, such as injection temperature and mass flow-rate, can be modified by external user-defined functions, depending on the atmosphere conditions.