Abstract: A simple nuclear reactor in which most of the reflector material is outside of the reactor vessel is described. The reactor vessel is a cylinder that contains all of the fuel salt and a displacement component, which may be a reflector, in the upper section of the reactor vessel. Other than the displacement component, the reflector elements including a radial reflector and a bottom reflector are located outside the vessel. The salt flows around the outside surface of the displacement component through a downcomer heat exchange duct defined by the exterior of the displacement component and the interior surface of the reactor vessel. This design reduces the overall size of the reactor vessel for a given volume of salt relative to designs with internal radial or bottom reflectors.

Abstract: Designs for a low power, fast spectrum molten fuel nuclear reactor that can be used to advance the understanding of molten salt reactors, their design and their operation are described. Furthermore, the designs described may be adapted to extra-terrestrial use as described herein for use as a low-gravity, moon-, Mars-, or space-based power generator. These low power reactors include a reactor core volume defined by a radial neutron reflector enclosed in a reactor vessel, in which heated fuel salt flows from the reactor core through a duct between the radial neutron reflector and the reactor vessel and back into the reactor core. Heat generated from the fission in the reactor core is transferred from the molten fuel through the reactor vessel to a coolant, in the case of an experimental design, or directly to an extra-terrestrial environment, in the case of an extra-terrestrial design.