FIG. 19 is a top-down schematic view of a molten nuclear fuel salt fast reactor core with a fuel region 1902 surrounded by a neutron reflector assembly 1900. The neutron reflector assembly includes an inner annular channel 1908 and outer annular channel 1910 surrounding fuel region 1902. The inner and outer annular channels 1908, 1910 may contain a neutron reflector material 1904. In an implementation, neutron reflector material 1904 may circulate in channels 1908, 1910 with input and output ports above fuel region 1902 such that no fixtures or ports are needed beneath the reactor. In other implementations, neutron reflector material 1904 may flow in only one direction, either in an upward or downward direction, through channels 1908, 1910 with one port above fuel region 1902 and another port below fuel region 1902. In yet other implementations, neutron reflector material 1904 may comprise a semi-stagnant or creeping flow through channels 1908, 1910. In yet other implementations, neutron reflector material 1904 may flow through radial input and output ports.
In one implementation, neutron reflector material 1904 may flow through channels 1908, 1910 at time periods near the beginning of the life of the reactor with fuel region 1902. As the reactor breeds fertile fuel over time, the effectiveness of the neutron reflector assembly 1900 may decrease because the inventory of bred nuclear fuel may exceed the amount needed to fuel the reactor. It may be desirable to therefore replace a portion of the neutron reflector material in part of the neutron reflector assembly as shown in FIG. 20 to alter the shape of the neutron reflector assembly 1900 over time.
