STUDY OF CAVITATION IN LIQUID SODIUM AND SIMULATION OF DYNAMIC CORE DEFORMATIONS.

Due to the high confinement of the closed fuel assemblies in Sodium-cooled Fast Reactors (SFR), the liquid sodium filling the space between these assemblies may vaporize in case of an important mechanical excitation (cavitation process). That phenomenon would therefore induce a specific force feedback to the assemblies leading to a specific neutronic response of the core. Neutronic of SFR is indeed sensible to mechanical deformation. Hence the necessity to have a good prediction of the displacement of these mechanical structures in the framework of Fluid-Structure Interaction (FSI). To study this kind of transient at a reactor scale, we propose in this paper a coupling procedure between the fluid and the structures. The fluid behaviour is investigated by Merkle's three-equations model and simulated within a coarse mesh. The structures are modelled by a mass-spring system subjected to the fluid forces. In order to stabilize the numerical code coupling, a relaxation process is added and some results of this computational work are presented. [ABSTRACT FROM AUTHOR]