A new experimental R&D program associated with the corium jet impingement on the ASTRID core catcher sacrificial material

International audienceThe strategy used in ASTRID Sodium Fast Reactor Demonstrator to mitigate the consequences of a postulated severe accident relies on the presence of dedicated corium discharge tubes between the active core region and the lower plenum and an in-vessel core catcher in the lower plenum to collect and cool the molten fuel. In this situation, the corium progression from the core towards the core catcher could lead to jet impingement on the core catcher surface and a subsequent degradation of the core-catcher material(s). After a review of the existing experimental database, it appeared necessary to define a dedicated experimental R&D program related to the long-lasting jet impingement on thick material plates. A particular behaviour will be studied when a molten pool is created (named “pool effect”) at the impingement point that reduces the heat transfer at the jet-material interface. In this scope, experimental tests with simulants and prototypic materials will be carried out by using the most possible representative conditions (e.g. Reynolds and Prandtl numbers) for ESFR (European Sodium Fast Reactor) severe accident conditions. Three R&D program have been proposed:(i) Ice-water jet impingement, the few results in the literature show a good agreement between ice-water jet system and metal wall/metal jet system which justifies the use of such simulant materials for investigating the impingement behaviour. The JOLO facility will be designed at LEMTA Nancy University.(ii) Molten steel jet impingement on the thick wall. The MOCKA facility in the Karlsruhe Institute of Technology will be used.(iii) Dedicated test section PLINIUS-2 IMPACT will be designed in future PLINIUS 2 large-mass prototypic-corium experimental platform at CEA Cadarache.First experiments have been carried out in the JOLO facility and provided dynamic ablation data before and during the formation of the pool. Additional JOLO tests and the MOCKA tests will be carried out in the frame of the ESFR-SMART European project starting by the end of 2017.The MOCKA tests will be performed with steel at higher temperature than in JOLO, before running core catcher qualification tests with prototypical corium (depleted UO2 and steel) and the ASTRID core catcher selected materials in PLINIUS-2 platform.New correlations and models will be developed from the experimental results in order to estimate the heat transfer data between the jet and the impacted material taking into account the “pool effect” phenomeno