Validation of the Large Interface Method of NEPTUNE_CFD 1.0.8 for Pressurized Thermal Shock (PTS) applications

NEPTUNE_CFD is a code based on a 3D transient Eulerian two-fluid model. One of the main application targets is the two-phase Pressurized Thermal Shock (PTS), which is related to PWR Reactor Pressure Vessel (RPV) lifetime safety studies, when sub-cooled water from Emergency Core Cooling (ECC) system is injected into the possibly uncovered cold leg and penetrates into the RPV downcomer. Five experiments were selected for the validation, a selection reviewed by a panel of European experts. The dynamic models are validated with a co-current smooth and wavy air–water stratified flow in a rectangular channel with detailed measurements of turbulence and velocities. The condensation models are validated with a co-current smooth and wavy steam-water stratified flow in a rectangular channel with measurements of the steam flow rates. The dynamic models are validated in the situation of a jet impinging a pool free surface with two experiments dealing with a water jet impingement on a water pool free surface in air environment. Finally, all the models involved in the reactor conditions are validated with the COSI experiment. The calculations are done with the same set of Large Interface Method models and a RANS (k–ɛ) approach for turbulence. They substantiate the application of the tool to PTS studies.

► The two-phase Pressurized Thermal Shock (PTS) is a key thermohydraulics issue for PWR safety.
► The dynamic and condensation models are firstly validated separately.
► Then the global validation is done with the COSI experiment.
► All the calculations performed with the same set of models both in the Large Interface Method and in the k–ɛ approach for turbulence substantiate the application of the tool to PTS.