MULTIPHYSICS MODELISATION OF AN UNPROTECTED LOSS OF FLOW TRANSIENT IN A SODIUM COOLED FAST REACTORS USING A NEUTRONIC-THERMAL-HYDRAULIC COUPLING SCHEME

Sodium cooled fast neutron reactors (SFR) are one of the selected reactor concepts in framework Generation IV International Forum. In this concept, unprotected loss cooling flow transients (ULOF), for which non-triggering backup systems is postulated, regarded as potential initiators core melting accidents. During an ULOF transient, spatial distributions fuel, structure and sodium temperatures affected by decrease, will modify energy distribution due to competition feedback effects. As no triggered, may reach its boiling temperature at some point, leading local density variations making transient fluctuate a two-phase physics where thermal-hydraulics neutronics interact with each other. The phenomenology involves several physic disciplines different time scales, such neutronics, coolant fuel thermo-mechanics. This paper presents results thermal-hydraulic/neutronic coupled simulations on SFR project ASTRID. These calculations based supervisor platform SALOME link code APOLLO3® system thermal-hydraulic CATHARE3. physical approach used coupling describe kinetic quasi-static adiabatic one, updating normalized power periodically performing static calculations, while point model associated calculates amplitude variations.