A three-dimensional neutronics - Thermalhydraulics Unprotected Loss of Flow simulation in Sodium-cooled Fast Reactor with mitigation devices

摘要

Within the framework of the Generation IV Sodium-cooled Fast Reactors R&D program at CEA, a low sodium void worth core concept has been developed. In this context, the core behavior in case of severe accidents is being assessed. Such transients are simulated with the SIMMER mechanistic code which gives reference simulation of the accidental transient. In this context, this paper presents the reactor case calculation in a heterogeneous ASTRID like core realized with a preliminary version of SIMMER-V code. Recently, significant effort on SIMMER code development and validation was realized by CEA and JAEA. The progress realized on the SIMMER code allows us to test the code behavior to simulate the whole severe accident sequence in three-dimensional geometry. After the calculation of steady state, the accidental transient of type of Unprotected Loss of Flow is being explored with SIMMER-V Preliminary Version (PV). A principal point of this study was to investigate the reactivity effects with fuel relocation under three-dimensional core representation including the mitigation devices. The calculation has indicated that the fuel discharge from the core via mitigation devices connecting the core zone with the core catcher is possible and may eliminate further reactivity increase. The main insight of the 3D studies in term of corium discharge efficiency is highlighted in the paper.