Benchmark of Eulerian-Lagrangian Methods for Solid Fission Product Tracking inside Molten Salt Reactor

The analysis of advanced reactor concepts such as the Molten Salt Reactor (MSR) requires the development of new modelling and simulation tools to deal with the characteristic features brought about by the innovative design. One of the peculiar aspects of liquid-fuel reactors, such as the MSR, is the mobility of fission products (FPs) in the reactor circuit. Some FPs species appear in the form of solid precipitates carried by the fuel flow and can deposit on reactor boundaries (e.g., heat exchangers, fuel containment walls), potentially representing design issues related to the degradation of heat exchange performance or radioactive hotspots. The solid FPs tracking is therefore relevant for the prediction of these phenomena. For this problem, both the Eulerian-Eulerian (E-E) and Eulerian-Lagrangian (E-L) approaches can be used, however, while the former can only track a scalar field representing the average concentration of FPs, the latter allows to individually track the behaviour of solid particles inside the reactor domain. Treating the particles as physical bodies instead of scalar fields allows a proper introduction of the phenomena influencing their behaviour, especially for deposition. For this reason, an E-L based solver is verified against an analytical case. This case was previously developed for the verification of an E-E multiphysics solver developed at Politecnico di Milano. The benchmark case was adapted for an E-L approach in OpenFOAM with the modification of a pre-existing solver. The verification was done by comparing the solid FPs concentration profiles obtained by the CFD simulation with the analytical case. The results showed good compatibility between E-L simulation and the analytical case.