Patent Number: 
Section: claims

1. A nuclear fission deflagration wave reactor core comprising:first nuclear fission fuel material configured to propagate a nuclear fission deflagration wave therein; andat least one removably replaceable nuclear fission igniter removably received in the first nuclear fission fuel material, the at least one removably replaceable nuclear fission igniter including a portion of second nuclear fission fuel material, wherein the at least one removably replaceable nuclear fission igniter is arranged to establish a keffective of at least 1. 2. The nuclear fission deflagration wave nuclear fission reactor core of claim 1, further comprising a plurality of coolant channels. 3. The nuclear fission deflagration wave nuclear fission reactor core of claim 2, wherein the at least one nuclear fission igniter defines a plurality of channels on an outer surface that mate with the plurality of coolant channels. 4. The nuclear fission deflagration wave nuclear fission reactor core of claim 1, wherein the first nuclear fuel material includes fertile material. 5. The nuclear fission deflagration wave nuclear fission reactor core of claim 4, wherein the fertile material includes fertile material chosen from 238U and 232Th. 6. The nuclear fission deflagration wave nuclear fission reactor core of claim 4, wherein the first nuclear fuel material further includes fissile material. 7. The nuclear fission deflagration wave nuclear fission reactor core of claim 6, wherein the fissile material includes fissile material chosen from 233U, 235U, and 239Pu. 8. The nuclear fission deflagration wave nuclear fission reactor core of claim 1, wherein the second nuclear fuel material includes fissile material. 9. The nuclear fission deflagration wave nuclear fission reactor core of claim 8, wherein the fissile material includes fissile material chosen from 233U, 235U, and 239Pu. 10. The nuclear fission deflagration wave nuclear fission reactor core of claim 8, wherein the second nuclear fuel material further includes fertile material. 11. The nuclear fission deflagration wave nuclear fission reactor core of claim 10, wherein the fertile material includes fertile material chosen from 238U and 232Th. 12. The nuclear fission deflagration wave nuclear fission reactor core of claim 1, wherein:the first nuclear fission fuel material has a first concentration of fissile material; andthe second nuclear fission fuel material has a second concentration of fissile material that is greater than the first concentration of fissile material. 13. The nuclear fission deflagration wave nuclear fission reactor core of claim 1, wherein concentration of the first nuclear fission fuel material varies spatially. 14. The nuclear fission deflagration wave nuclear fission reactor core of claim 1, wherein concentration of the second nuclear fission fuel material varies spatially. 15. The nuclear fission deflagration wave nuclear fission reactor core of claim 1, wherein the at least one nuclear fission igniter has at least one dimension of not substantially less than one mean free path for fission-inducing neutrons. 16. The nuclear fission deflagration wave nuclear fission reactor core of claim 1, wherein the at least one nuclear fission igniter has at least one dimension of less than one mean free path for fission-inducing neutrons. 17. The nuclear fission deflagration wave nuclear fission reactor core of claim 1, wherein the at least one nuclear fission igniter is configured for removal of neutron absorbing material therefrom. 18. The nuclear fission deflagration wave nuclear fission reactor core of claim 17, wherein the neutron absorbing material includes a neutron absorber chosen from 10B and 6Li. 19. The nuclear fission deflagration wave nuclear fission reactor core of claim 17, wherein the neutron absorbing material is removable from within the portion of second nuclear fission fuel material. 20. The nuclear fission deflagration wave nuclear fission reactor core of claim 17, wherein the neutron absorbing material is removable from an exterior of the portion of second nuclear fission fuel material. 21. The nuclear fission deflagration wave nuclear fission reactor core of claim 1, further comprising neutron moderating material. 22. The nuclear fission deflagration wave nuclear fission reactor core of claim 21, wherein the neutron moderating material includes a neutron moderator chosen from heavy water, carbon, and 7Li. 23. The nuclear fission deflagration wave nuclear fission reactor core of claim 1, further comprising neutron reflecting material. 24. The nuclear fission deflagration wave nuclear fission reactor core of claim 23, wherein the neutron reflecting material includes a neutron reflector chosen from graphite and beryllium. 25. The nuclear fission deflagration wave nuclear fission reactor core of claim 1, further comprising neutron multiplicative material. 26. The nuclear fission deflagration wave nuclear fission reactor core of claim 25, wherein the neutron multiplicative material includes a neutron multiplier chosen from 9Be and beryllides.