FIG. 7 shows example fast neutrons 710 emanating from a fuel region 702. Fast neutrons are indicated by lines terminating in double arrows. Example fast neutrons 710 may originate in fuel region 702 and be reflected by a neutron reflector material 704 and travel back into fuel region 702. Example fast neutrons 710 reflected back into fuel region 702 may increase the fissile material in fuel region 702 upon contact with fertile materials. Similarly, FIG. 7 shows example thermal neutrons 714. Example thermal neutrons 714 are indicated by lines terminating in single arrows. Example thermal neutrons 714 may be reflected by neutron reflector material 704 and travel back into fuel region 702. Example thermal neutrons reflected into fuel region 702 may increase the reactivity in fuel region 702 upon contact with fissile material located therein.
