Assessment of the Rankine Vortex Model for Modeling the Gas Entrainment in a Representative Mock-up of a Sodium Fast Reactor

Since decades, the CEA has been involved in the development of 4th generation reactors cooled by sodium. The dedicated experimental platform PLATEAU was erected to study the different issues and built a results database for the code validation. As experiments with sodium are complex, the tests are led in mock-ups using water as a simulant fluid. The MICAS mock-up, model of the upper plenum, aims at studying the gas entrainment at the free surface. Gas is prohibited in the reactor core due to neutron effects, which may induce reactivity variations. Since vortices are difficult to handle by numerical codes in complex geometries such as reactor ones, criteria have been developed based on the Rankine vortex model to forecast the air entrainment. However, in some case, numerical results do not correlate the experimental ones and those discrepancies are may be due to the vortex model. This article aims at comparing the vortices characteristics calculated using the Rankine vortex model with experimental results in order to improve the gas entrainment criteria. The parameters of the Rankine model are determined using the velocity fields measured by the Particle Image Velocity (PIV) method and the vortices diameter is calculated using the raw PIV images.