FIG. 5 is a top-down schematic view of a dynamic neutron reflector assembly 500 with a plurality of refractory clad sleeves 502 to conduct a flowing neutron reflector material therethrough. In an implementation, flowing neutron reflector assembly 500 substantially surrounds a nuclear fuel region 504 from which fast spectrum neutrons 506 emanate. In FIG. 5, example paths of fast spectrum neutrons 506 are indicated by lines terminating in double arrows, such as lines 508. The example fast spectrum neutrons 506 are inelastically scattered (or reflected) from the flowing reflector material and back into the nuclear fuel region 504. The reflector configuration of FIG. 5 may be used to incrementally shift neutron spectrum in nuclear fuel region 504 by selectively filling each of the channels 502 with a volume of neutron reflector material.
