Patent Number: 
Section: claims

1. A fission process reactor unit, comprising:a radioactive element;a cobalt 59 (Co-59) layer;a Nuclear Thermionic Avalanche Cell (NTAC); anda thermoelectric generator,wherein:a fission process of the radioactive element releases neutrons to the Co-59 layer to breed cobalt 60 (Co-60);the NTAC receives gamma rays from the fission process, a by-product of the fission process, and the bred Co-60 to generate direct current (DC) power; andthe thermoelectric generator receives thermal energy from the radioactive element and the NTAC to generate DC power. 2. The fission process reactor unit of claim 1, wherein the radioactive element comprises uranium 235 (U-235) and the by-product of the fission process is cesium 137 (Cs-137). 3. The fission process reactor unit of claim 2, wherein the U-235 is a fuel rod and the fission process is controlled by a primary neutron source rod controllably inserted or removed from the fuel rod. 4. The fission process reactor unit of claim 3, wherein the Co-59 layer at least partially encircles the U-235 fuel rod. 5. The fission process reactor unit of claim 4, wherein the Co-59 layer is disposed between the U-235 fuel rod and the NTAC. 6. The fission process reactor unit of claim 5, wherein the NTAC is disposed between the Co-59 layer and the thermoelectric generator. 7. The fission process reactor unit of claim 6, wherein the NTAC and the thermoelectric generator are connected in tandem to a same DC bus or load. 8. The fission process reactor unit of claim 6, wherein the NTAC comprises a photoionic electron emitter separated from an electron getter electrode by a thermionic vacuum gap. 9. A reactor system, comprising:a containment vessel; andone or more fission process reactor units supported within the containment vessel, each of the one or more fission process reactor units comprising:a radioactive element;a cobalt 59 (Co-59) layer;a Nuclear Thermionic Avalanche Cell (NTAC); anda thermoelectric generator,wherein:a fission process of the radioactive element releases neutrons to the Co-59 layer to breed cobalt 60 (Co-60);the NTAC receives gamma rays from the fission process, a by-product of the fission process, and the bred Co-60 to generate direct current (DC) power; andthe thermoelectric generator receives thermal energy from the radioactive element and the NTAC to generate DC power. 10. The reactor system of claim 9, wherein the one or more fission process reactor units are twenty five or more fission process reactor units. 11. The reactor system of claim 9, wherein the radioactive element comprises uranium 235 (U-235) and the by-product of the fission process is cesium 137 (Cs-137). 12. The reactor system of claim 11, wherein the Co-59 layer at least partially encircles the U-235 fuel rod. 13. The reactor system of claim 12, wherein the Co-59 layer is disposed between the U-235 fuel rod and the NTAC and the NTAC is disposed between the Co-59 layer and the thermoelectric generator. 14. The reactor system of claim 13, wherein each of the one or more fission process reactor units are connected to a same DC bus. 15. The reactor system of claim 14, wherein the NTAC comprises a photoionic electron emitter separated from an electron getter electrode by a thermionic vacuum gap. 16. The reactor system of claim 9, further comprising a fluid circulated within the containment vessel. 17. The reactor system of claim 16, wherein the fluid is argon gas.