Influence of the reprocessing on molten salt reactor behaviour

International audienceThe Molten Salt Reactor is one of the systems studied as a Generation IV reactor. Its main characteristic is the strong coupling between neutronics and salt reprocessing. Such nuclear reactors use a liquid fuel which is also the coolant. Elements produced during the reactor's operation, like Fission Products (FP) or TransUranians, modify the neutronic balance of the reactor by capturing neutrons. As the fuel is liquid, samples can be extracted and reprocessed to remove the poisoning elements, without stopping reactor operation. This reprocessing includes two components: a bubbling system within the reactor which extracts the gaseous and metallic FPs quickly and a slower external unit that extracts the other FPs. A fluorination removes Uranium to reinject it immediately in the core. The rest of the salt is then treated in a decicated reprocessing unit. A salt volume equal to the core volume is cleaned in several months. We have studied the influence of different reprocessing rates on the reactor's behaviour. This mainly affects the breeding ratio, which represents the ratio of Thorium-232 converted into Uranium-233 over Uranium-233 burnt. By considering both the possibilities in chemistry and the neutronic impacts presented here, our aim is to work out an efficient, reliable and realistic reprocessing schem