Thermalhydraulic aspects of decay heat removal by natural circulation in fast reactor systems. Final report

Abstract

Natural convection in enclosures have been studied numerically to provide insigh,_into the scaling laws existing for removal of decay heat in Liquid Metal Fast Reactors (LMFR). Speci.ficaUy, 3-D simulations have been carried out for natural circulation in a cylinder with small aspect ratio (of the order of 0.5). These results have been compared to the results of an experiment conducted by UCSB, in collaboration with GE, to provide benchmark data for code validation. Parametric studies have been conducted to establish the validity of a 3-D Finite difference code that uses body-fitted grids for simulations of complex geometries. Ft,rther, numerical simulations have been carried out to demonstrate the importance of 3-D computer codes as tools in the design and scale-up of prototypic LMFRs. It has ben shown that the geometry of the passive safety systems is key to safe operation of LMFRs under shutdown conditions. The key phenomena that occur in such situations have been studied and the available experimental o studies have been identified. The future direction for modeling of natural convection recirculating flows in confined enclosures has been proposed.