Analysis of Coupled Dynamics of Molten Salt Reactors

This paper presents a preliminary analysis of the coupled thermo-hydrodynamics and neutronics of circulating nuclear fuel systems like the thermal Molten Salt Reactor (MSR), one of the "Generation IV International Forum" concepts. This kind of nuclear reactor adopts a molten salt mixture, which flows up through channels in a graphite moderated core and plays the role of both heat generator and coolant. A strongly coupled modelling is needed since the velocity pattern is affected by the neutron dynamics via the heat source from fission reactions, whereas the neutronic behaviour is affected by the thermo-hydrodynamics via the motion of precursors. In this complex environment, featured by a highly non linear regime and a wide disparity of time scales, COMSOL Multiphysics® has been successfully employed to investigate the system behaviour both in steady state and transient conditions with reference to a simple 2-D geometry, which represents a typical channel of a sub-critical MSR and comprises both the flowing fluid and the graphite matrix.