Patent Number: 
Section: claims

1. A nuclear fission reactor, comprising:a heat-generating nuclear fission fuel assembly configured to have at least a portion of a traveling burn wave; anda flow control assembly coupled to said nuclear fission fuel assembly and capable of modulating flow of a fluid stream in response to the traveling burn wave, the flow control assembly including:an outer sleeve defining therein a plurality of outer sleeve holes and having an outer sleeve engagement surface;an inner sleeve slidably insertable into the outer sleeve, the inner sleeve defining therein a plurality of inner sleeve holes that are progressively axially alignable with the plurality of outer sleeve holes;a carriage subassembly having a carriage subassembly engagement surface arranged to rotatably engage the outer sleeve engagement surface; andan anti-rotation mechanism that engages the outer sleeve and the inner sleeve, the anti-rotation mechanism restricting relative rotation of the outer sleeve with respect to the inner sleeve and permitting axial translation of the outer sleeve with respect to the inner sleeve. 2. The nuclear fission reactor of claim 1, wherein the flow control assembly is responsive to an operating parameter associated with said nuclear fission fuel assembly. 3. The nuclear fission reactor of claim 2, wherein the operating parameter associated with said nuclear fission fuel assembly is current temperature in said nuclear fission fuel assembly. 4. The nuclear fission reactor of claim 2, wherein the operating parameter associated with said nuclear fission fuel assembly is neutron fluence in said nuclear fission fuel assembly. 5. The nuclear fission reactor of claim 2, wherein the operating parameter associated with said nuclear fission fuel assembly is a characteristic isotope in said nuclear fission fuel assembly. 6. The nuclear fission reactor of claim 2, wherein the operating parameter associated with said nuclear fission fuel assembly is pressure in said nuclear fission fuel assembly. 7. The nuclear fission reactor of claim 2, wherein the operating parameter associated with said nuclear fission fuel assembly is fluid flow rate in said nuclear fission fuel assembly. 8. The nuclear fission reactor of claim 1, wherein the flow control assembly is reconfigurable according to a predetermined input to the flow control assembly. 9. The nuclear fission reactor of claim 8, wherein the predetermined input to the flow control assembly is a signal responsive to a temperature sensor. 10. The nuclear fission reactor of claim 8, wherein the predetermined input to the flow control assembly is a signal responsive to a reactor control system. 11. The nuclear fission reactor of claim 8, wherein the predetermined input to the flow control assembly is a signal responsive to a fluid flow meter. 12. The nuclear fission reactor of claim 8, wherein the predetermined input to the flow control assembly is a signal produced by a neutron flux detector. 13. The nuclear fission reactor of claim 1, wherein said flow control assembly is configured to control flow of the fluid stream according to when the burn wave arrives at a selected location. 14. The nuclear fission reactor of claim 1, wherein said flow control assembly is configured to control flow of the fluid according to when the burn wave departs from a selected location. 15. The nuclear fission reactor of claim 1, wherein said flow control assembly is configured to control flow of the fluid according to when the burn wave is proximate to a selected location. 16. The nuclear fission reactor of claim 1, wherein said flow control assembly is configured to control flow of the fluid stream according to a width of the burn wave. 17. The nuclear fission reactor of claim 1, wherein said flow control assembly is configured to control flow of the fluid stream according to a heat generation rate in said fuel assembly. 18. The nuclear fission reactor of claim 1, wherein said flow control assembly is configured to control flow of the fluid stream according to temperature in said fuel assembly. 19. The nuclear fission reactor of claim 1, wherein said flow control assembly is configured to control flow of the fluid stream according to neutron flux in said fuel assembly.