In FIG. 5, the neutron reflector material flows upward through a refractory clad channel 502 toward the viewer. In an implementation, neutron reflector material may circulate in channels 502 (e.g., cells, sleeves, conduits, etc.) with input and output ports above the nuclear fuel region 504 such that no fixtures or ports are needed beneath the reactor. In other implementations, the neutron reflector material may flow in only one direction, either in an upward or downward direction, through the channels 502 with one port above the nuclear fuel region 504 and another port below fuel region 504. In yet other implementations, the neutron reflector material may comprise a semi-stagnant or creeping flow through the channels 502. In yet other implementations, the neutron reflector material may flow through radial input and output ports.
