Patent Number: 
Section: claims

1. A 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; andwherein the system produces approximately 50 MWe to approximately 100 MWe. 2. The nuclear reactor system of claim 1, further comprising a heat source reactor driving a supercritical CO2 Brayton cycle energy converter. 3. The nuclear reactor system of claim 2, wherein the energy converter has a conversion efficiency of approximately 39% to approximately 41%. 4. The nuclear reactor system of claim 1, further comprising a heat source reactor driving a Rankine steam cycle. 5. The nuclear reactor system of claim 1, further comprising bottoming cycles for cogeneration. 6. The nuclear reactor system of claim 1, further comprising a balance of plant with no nuclear safety function. 7. The nuclear reactor system of claim 1, wherein the reactor tank comprises thin walled stainless steel. 8. The nuclear reactor system of claim 1, wherein the reactor tank is positioned in a guard vessel. 9. The nuclear reactor system of claim 8, wherein the reactor tank further comprises a deck, and wherein at least the deck is enclosed by a removable dome. 10. The nuclear reactor system of claim 9, wherein the guard vessel and the removable dome form a containment structure. 11. The nuclear reactor system of claim 10, wherein the containment structure is emplaced in a silo shield structure with seismic isolation. 12. The nuclear reactor system of claim 1, wherein the reactor core comprises enriched uranium/zirconium alloy for an initial core. 13. The nuclear reactor system of claim 1, wherein the reactor core comprises recycled uranium/transuranic zirconium for refueling cores. 14. The nuclear reactor system of claim 1, wherein the reactor core comprises one or more multi-assembly clusters. 15. The nuclear reactor system of claim 14, 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. 16. The nuclear reactor system of claim 1, wherein the system comprises a burnup swing of less than approximately 1% Δk/k. 17. The nuclear reactor system of claim 1, wherein the at least one passive safety system comprises a passive decay heat removal channel. 18. The nuclear reactor system of claim 17, wherein the passive decay heat removal channel operates at less than or approximately equal to 1% full power. 19. The nuclear reactor system of claim 1, wherein the at least one passive safety system relate to power characteristics, fuel characteristics, and coolant temperatures. 20. The nuclear reactor system of claim 1, wherein the at least one passive load follow system comprises sensing balance of plant demand communicated via flow rate and return temperature of a heat transport loop. 21. The nuclear reactor system of claim 1, wherein the system produces approximately 100 MWe. 22. A method for providing nuclear energy, the method comprising:providing a 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;at least one passive safety system comprising reactivity feedbacks; andat least one passive load follow system;initiating the nuclear reactor system;converting heat to electricity; andsupplying the electricity, andwherein the system produces approximately 50 MWe to approximately 100 MWe. 23. The method of claim 22, further comprising a balance of plant with no nuclear safety function. 24. The method of claim 22, wherein the at least one passive safety system comprises a passive decay heat removal channel. 25. The method of claim 22, wherein the at least one passive load follow system comprises sensing balance of plant demand communicated via flow rate and return temperature of a heat transport loop.