Patent Number: 
Section: claims

1. A fast neutron spectrum nuclear reactor system comprising:a reactor comprising:a reactor tank;a reactor core within the reactor tank, the reactor core comprising a fuel column of metal or cermet fuel using liquid sodium as a heat transfer medium; anda pump for circulating the liquid sodium through a heat exchanger; andat least one passive safety system comprising reactivity feedbacks;at least one passive load follow system;a balance of plant with no nuclear safety function; anda heat source reactor driving a supercritical CO2 Brayton cycle energy converter with approximately 40% or more conversion efficiency;wherein the reactor is modular, andwherein the system produces between approximately 50 MWe to approximately 100 MWe. 2. The reactor system of claim 1, further comprising a small-volume containment structure comprising a guard vessel and a dome over a reactor deck, and wherein the small-volume containment structure is emplaced in a silo shield structure with seismic isolation. 3. The reactor system of claim 1, wherein no refueling equipment or fuel storage is located onsite. 4. The reactor system of claim 1, wherein a first loading is enriched uranium at less than approximately 20% enrichment, and all subsequent loadings are recycled uranium, transuranics and zirconium. 5. The reactor system of claim 1, wherein a refueling interval is approximately 20 years, and the whole reactor core is replaced during refueling. 6. The reactor system of claim 1, further comprising one or more multi-assembly clusters. 7. The reactor system of claim 6, wherein the one or more multi-assembly clusters have derated specific power, kwt/kg fuel, for enabling long refueling intervals and enabling refueling operations to begin approximately two weeks after reactor shutdown. 8. The reactor system of claim 1, further comprising a removable and adjustable wedge in the reactor core at above core load pads elevation for core clamping and fine tuning adjustments of the reactivity feedbacks. 9. The reactor system of claim 1, wherein thermal efficiency of the system is between approximately 39% and approximately 41%. 10. The reactor system of claim 1, wherein an internal breeding ratio is approximately unity. 11. A method for providing nuclear energy, the method comprising:providing fast neutron spectrum nuclear reactor system, the system comprising:a reactor comprising:a reactor tank;a reactor core within the reactor tank, the reactor core comprising a fuel column of metal or cermet fuel using liquid sodium as a heat transfer medium; anda pump for circulating the liquid sodium through a heat exchanger; andat least one passive safety system comprising reactivity feedbacks;at least one passive load follow system;a balance of plant with no nuclear safety function; anda heat source reactor driving a supercritical CO2 Brayton cycle energy converter with approximately 40% or more conversion efficiency;initiating the system;converting heat to electricity; andsupplying the electricity,wherein the reactor is modular, andwherein the system produces approximately 50 MWe to approximately 100 MWe. 12. The method of claim 11, wherein the reactor further comprises a small-volume containment structure comprising a guard vessel and a dome over a reactor deck, and wherein the small-volume containment structure is emplaced in a silo shield structure with seismic isolation. 13. The method of claim 11, wherein no refueling equipment or fuel storage is located onsite. 14. The method of claim 11, wherein a first loading is enriched uranium at less than approximately 20% enrichment, and a subsequent loading is recycled uranium, self-generated transuranics and zirconium. 15. The method of claim 11, wherein a refueling interval is approximately 20 years, and the whole reactor core is replaced during refueling. 16. The method of claim 11, wherein the reactor further comprises one or more multi-assembly clusters. 17. The method of claim 16, wherein the one or more multi-assembly clusters have derated specific power, kwt/kg fuel, for enabling long refueling intervals and enabling refueling operations to begin approximately two weeks after reactor shutdown. 18. The method of claim 11, wherein the reactor further comprises a removable and adjustable wedge in the reactor core at above core load pads elevation for core clamping and fine tuning adjustments of the reactivity feedbacks. 19. The method of claim 11, wherein thermal efficiency of the system is between approximately 39% and approximately 41%. 20. The method of claim 11, wherein an internal breeding ratio is approximately unity. 21. A system for core clamping, the system comprising:a reactor core comprising one or more ducted fuel assemblies and a core central assembly location;one or more top load pads coupled to each of the one or more ducted fuel assemblies near top ends of the one or more ducted fuel assemblies;one or more above core load pads coupled to each of the one or more ducted fuel assemblies below the one or more top load pads;a core forming ring surrounding the reactor core at approximately a top load pad level, wherein the core forming ring is contacted by one or more top load pads during operation of the reactor core;a removable and adjustable wedge for insertion into the core central assembly location; anda wedge driveline coupled to the wedge for inserting, removing and adjusting a position of the wedge. 22. The system of claim 21, wherein the wedge is inserted to approximately an above core load pads elevation for core clamping and fine tuning adjustments of reactivity feedbacks. 23. The system of claim 21, wherein the wedge driveline is thermally expandable for fine tuning adjustments of reactivity feedbacks. 24. The system of claim 21, wherein the wedge is loosened and removed for refueling operations.