Patent Number: 
Section: claims

1. A nuclear fission fuel pin comprising:cladding defining an elongated enclosure, the enclosure having a fission region and a fertile blanket region;a solution of a first fissile nuclear fission fuel material dissolved in neutronically translucent liquid carrier material, the solution being distributed into the elongated enclosure including into the fission region and into the fertile blanket region; anda solid phase, undissolved fertile nuclear fission fuel material, in foam form, disposed in the fertile blanket region of the elongated enclosure and in direct physical contact with the solution in the elongated enclosure, the fertile nuclear fission fuel material being transmutable into a second fissile nuclear fission fuel material directly diffusible into the solution. 2. The nuclear fission fuel pin of claim 1, wherein the cladding defines an elongated enclosure having a first axial end, a second axial end, and a centralized axial region between the first and second axial ends. 3. The nuclear fission fuel pin of claim 2, wherein the centralized axial region of the elongated enclosure defines the fission region of the nuclear fission fuel pin. 4. The nuclear fission fuel pin of claim 2, wherein the fertile nuclear fission fuel material is disposed toward the first and second ends of the elongated enclosure. 5. The nuclear fission fuel pin of claim 4, wherein the first and second ends of the elongated enclosure define first and second fertile blanket zones, respectively, of the nuclear fission fuel pin. 6. The nuclear fission fuel pin of claim 1, wherein the solution and the fertile nuclear fission fuel material are distributed heterogeneously into the elongated enclosure. 7. The nuclear fission fuel pin of claim 1, wherein solubility of the second fissile nuclear fission fuel material in the neutronically translucent liquid carrier material is greater than solubility of the fertile nuclear fission fuel material in the neutronically translucent liquid carrier material. 8. The nuclear fission fuel pin of claim 1, wherein the fertile nuclear fission fuel material is substantially insoluble in the neutronically translucent liquid carrier material. 9. The nuclear fission fuel pin of claim 1, wherein the neutronically translucent liquid carrier material includes a material chosen from Mg, Ag, Ca, and Ni. 10. The nuclear fission fuel pin of claim 1, wherein the first fissile nuclear fission fuel material includes 239Pu. 11. The nuclear fission fuel pin of claim 1, wherein the fertile nuclear fission fuel material includes 238U. 12. The nuclear fission fuel pin of claim 1, wherein the fertile nuclear fission fuel material is disposed in contact with a wall of the elongated enclosure of cladding. 13. The nuclear fission fuel pin of claim 1, wherein a first concentration of the second fissile nuclear fission fuel material in the fertile nuclear fission fuel material is greater than a second concentration of the first fissile nuclear fission fuel material in the neutronically translucent liquid carrier material. 14. The nuclear fission fuel pin of claim 1, wherein the fertile nuclear fission fuel material is disposed in the fertile blanket region of the elongated enclosure and not disposed in the fission region of the elongated enclosure. 15. The nuclear fission fuel pin of claim 1, wherein the fertile region is in fluid communication with the fertile blanket region.