Patent Number: 
Section: claims

1. A nuclear fission reactor structure comprising a plurality of layers, wherein each layer of the plurality of layers includes:an inner segment body including an inner opening extending axially from a first side of the inner segment body to a second side of the inner segment body;an intermediate segment body radially outward of the inner segment body;an outer segment body radially outward of the intermediate segment body;a first interior interface separating the inner segment body and the intermediate segment body; anda second interior interface separating the intermediate segment body and the outer segment body,wherein, in a cross-sectional plan view in a plane perpendicular to the axially extending inner opening:the inner segment body includes a plurality of inner cladding arms having a first involute curve shape that spirally radiates outward from a first radially inner end adjacent to the inner opening to a first radially outer end at the first interior interface,the intermediate segment body includes a plurality of intermediate cladding arms having a second involute curve shape that spirally radiates outward from a second radially inner end adjacent to the first interior interface to a second radially outer end at the second interior interface, andthe outer segment body includes a plurality of outer cladding arms having a third involute curve shape that spirally radiates outward from a third radially inner end adjacent to the second interior interface to a third radially outer end at a radially outer surface of the outer segment body,wherein the inner cladding arms have opposing side surfaces extending from the first side of the inner segment body to the second side of the inner segment body, and wherein at least one protrusion projects outwardly from at least one opposing side surface, andwherein the protrusion has a top surface distal from the at least one opposing side surface for which the protrusion projects, and wherein, when assembled in the inner segment body with a first inner cladding arm immediately adjacent a second inner cladding arm, the top surface of a protrusion on the first inner cladding arm contacts an opposing side surface on the second inner cladding arm and forms a channel between the first inner cladding arm and the second inner cladding arm. 2. The nuclear fission reactor structure according to claim 1, wherein each of the first involute curve shape, the second involute curve shape, and the third involute curve shape have a different curvature. 3. The nuclear fission reactor structure according to claim 1, wherein each of the first involute curve shape, the second involute curve shape, and the third involute curve shape correspond to different portions of a continuous involute curve shape extending from the inner opening to the radially outer surface of the outer segment body. 4. The nuclear fission reactor structure according to claim 1, wherein, collectively, the first involute curve shape, the second involute curve shape, and the third involute curve shape form a continuous involute curve shape extending from the inner opening to the radially outer surface of the outer segment body. 5. The nuclear fission reactor structure according to claim 4, wherein a projection of a surface of the continuous involute curve shape extends across the first interior interface and the second interior interface and is coincident with each of a surface of one of the plurality of inner cladding arms, a surface of one of the plurality of intermediate cladding arms, and a surface of one of the plurality of outer cladding arms. 6. The nuclear fission reactor structure according to claim 1, wherein each of the first involute curve shape, the second involute curve shape, and the third involute curve shape correspond to different portions of a continuous involute curve shape extending from the inner opening to the radially outer surface of the outer segment body. 7. The nuclear fission reactor structure according to claim 6, wherein a projection of a surface of the continuous involute curve shape extends across the first interior interface and the second interior interface and is coincident with each of a surface of one of the plurality of inner cladding arms, a surface of one of the plurality of intermediate cladding arms, and a surface of one of the plurality of outer cladding arms. 8. The nuclear fission reactor structure according to claim 1, wherein each of the plurality of inner cladding arms, the plurality of intermediate cladding arms, and the plurality of outer cladding arms include a plurality of chambers. 9. The nuclear fission reactor structure according to claim 8, wherein the chambers in each cladding arm are separated from each other by a web. 10. The nuclear fission reactor structure according to claim 8, wherein each inner cladding arm has more chambers than each outer cladding arm. 11. The nuclear fission reactor structure according to claim 8, wherein the plurality of chambers is ten or less. 12. The nuclear fission reactor structure according to claim 8, wherein each intermediate cladding arm has the same number of chambers as each outer cladding arm. 13. The nuclear fission reactor structure according to claim 8, wherein the chambers include one of a fissionable fuel composition and a moderator material. 14. The nuclear fission reactor structure according to claim 13, wherein chambers at different locations along the cladding arm contain different fissionable fuel compositions. 15. The nuclear fission reactor structure according to claim 14, wherein chambers at different locations along the cladding arm contain different moderator material. 16. The nuclear fission reactor structure according to claim 13, wherein, when a fissionable fuel composition is located in a chamber, there is a space between at least a portion of one interior surface wall of the chamber and at least a portion of one exterior surface of a body formed of the fissionable fuel composition. 17. The nuclear fission reactor structure according to claim 1, wherein each protrusion extends along the at least one opposing side surface continuously from a first end oriented toward the first side of the inner segment body to a second end oriented toward the second side of the inner segment body. 18. The nuclear fission reactor structure according to claim 1, wherein each protrusion extends along the at least one opposing side surface discontinuously from a first end oriented toward the first side of the inner segment body to a second end oriented toward the second side of the inner segment body. 19. The nuclear fission reactor structure according to claim 1, wherein the inner segment body, the intermediate segment body, the outer segment body, the first interior interface, and second interior interface define a layer. 20. A nuclear fission reactor, comprising:a plurality of layers according to claim 19, wherein the plurality of layers are assembled into a nuclear fission reactor structure with a first end surface, a second end surface, and an outer side surface connecting the first end surface to the second end surface;a radial reflector positioned about the outer side surface of the nuclear fission reactor structure;a pressure vessel; anda coolant system in fluid communication with the nuclear fission reactor structure through openings in the pressure vessel. 21. The nuclear fission reactor according to claim 20, wherein the nuclear fission reactor structure has a cylindrical structure. 22. The nuclear fission reactor according to claim 20, wherein the coolant system is fluid-based or gas-based. 23. The nuclear fission reactor according to claim 20, wherein the first interior interface and the second interior interface in each of the plurality of layers include a plurality of secondary coolant channels that traverse the nuclear fission reactor structure from the first end to the second end. 24. A method of fabricating the nuclear fission reactor structure according to claim 1, the method comprising:manufacturing the inner segment body, segments of the intermediate segment body, and segments of the outer segment body, wherein each of the plurality of inner cladding arms, the plurality of intermediate cladding arms, and the plurality of outer cladding arms include a plurality of chambers;assembling the inner segment body, the segments of the intermediate segment body, and the segments of the outer segment body into a layer, wherein the segment bodies are assembled by one of welding and bonding;positioning one of a fissionable fuel composition and a moderator material in the plurality of chambers to form a fuel-loaded layer; andassembling a plurality of fuel-loaded layers into the nuclear fission reactor structure. 25. The method according to claim 24, wherein the inner segment body, segments of the intermediate segment body, and segments of the outer segment body are manufactured using an additive manufacturing process. 26. The method according to claim 24, including positioning the nuclear fission reactor structure within a radial reflector, wherein the nuclear fission reactor structure has a cylindrical shape. 27. A method of fabricating the nuclear fission reactor structure according to claim 1, the method comprising:manufacturing a layer including the inner segment body, the intermediate segment body, and the outer segment body as a unitary structure, wherein each of the plurality of inner cladding arms, the plurality of intermediate cladding arms, and the plurality of outer cladding arms include a plurality of chambers;positioning one of a fissionable fuel composition and a moderator material in the plurality of chambers to form a fuel-loaded layer; andassembling a plurality of fuel-loaded layers into the nuclear fission reactor structure. 28. The method according to claim 27, wherein the unitary structure of the inner segment body, the intermediate segment body, and the outer segment body are manufactured using an additive manufacturing process. 29. The method according to claim 27, including positioning the nuclear fission reactor structure within a radial reflector, wherein the nuclear fission reactor structure has a cylindrical shape.