On the numerical modelling of frozen walls in a molten salt fast reactor☆

Highlights: • Freezing of salt films on the vessel wall of a molten salt fast reactor was studied. • Separated plutonium and natural uranium were burnt in the molten salt fast reactor. • Coupled simulations of the neutron and thermal fluid dynamics were performed. • Temperature dependent porosity represented the frozen salt at the wall. • Thin layers obtained with isothermal walls and no layers for non-uniform heat fluxes. - Abstract: Coupled neutronic and thermal fluid dynamic simulations of a molten salt fast reactor have been performed. The reactor is an innovative concept intended to burn spent nuclear fuel. A key issue with the development of reactor concepts is the corrosive nature of the selected molten salts based on eutectics of lithium fluoride. This paper investigates the usage of a frozen salt film to protect the vessel wall. Six case studies examine each of the modelling techniques that are applied for the simulation of frozen salt films on the walls of a molten salt fast reactor. The preliminary findings are that a very thin layer of frozen salt can form at a wall with isothermal conditions, but it is unstable in regions where high temperatures are found. Simulations of conjugate heat transfer in two-dimensions showed that the thin frozen salt films are unable to resist the heat flux resulting from the nuclear reactions.