Patent Number: 
Section: claims

1. A process for fabricating a porous nuclear fuel element, comprising:a) providing a skeletal structure comprising interconnected pores; andb) performing chemical vapor infiltration (CVI) of the skeletal structure with a nuclear fuel material; wherein the process of chemical vapor infiltration comprises:i) heating the skeletal structure;ii) forcing a precursor gas through the heated skeletal structure;iii) decomposing the precursor gas inside of the heated skeletal structure; andiv) condensing the decomposed gases from the vapor state as a solid deposited on internal and external surfaces of the skeletal structure to form a skeletal structure comprising solid fuel ligaments;wherein the skeletal structure comprises a reticulated vitreous or glassy carbon foam. 2. The process of claim 1, further comprising:machining the skeletal structure to near-final dimensions prior to performing chemical vapor infiltration. 3. The process of claim 1, further comprising:coating the solid fuel ligaments with a barrier coating comprising one or more materials selected from the group consisting of: SiC, NbC, ZrC, BeO, BeC2, ZrC2, SiC, pyrolytic carbon, diamond, and diamond-like carbon. 4. The process of claim 1, wherein the step of providing a skeletal structure comprising a reticulated vitreous or glassy carbon foam comprises:a) providing polyurethane foam;b) impregnating the polyurethane foam with a carbon-bearing resin; and thenc) pyrolizing the resin-impregnated polyurethane foam to produce a reticulated vitreous carbon foam skeletal structure comprising vitreous or glassy carbon. 5. The process of claim 1, wherein precursor gas comprises a mixture of niobium pentachloride, zirconium pentachloride, uranium pentachloride, methane and hydrogen;wherein the precursor gas decomposes during chemical vapor infiltration to deposit solid uranium tricarbide (U,Zr,Nb)C on the internal and external surfaces of the skeletal structure. 6. The process of claim 1, wherein the stoichiometry of the solid uranium tricarbide deposit comprises (U0.1Zr0.77Nb0.13) C0.95. 7. The process of claim 1, wherein the solid fuel ligaments comprises a uranium tricarbide solid-solution alloy having a density of the alloy greater than or equal to 99% of theoretical density. 8. The process of claim 1, wherein the skeletal structure is formed of ligaments comprising one or more materials selected from the group consisting of: carbon, graphite, Zr, Nb, Mo, Hf, Ta, W, Re, TiC, TaC, ZrC, SiC, HfC, BeC2, B4C, NbC, GdC, HfB2, ZrB2, Si3N4, TiO2, BeO, SiO2, ZrO2, HfO2, Y2O3, Al2O3, Sc2O3, and Ta2O5. 9. The process of claim 1, wherein the solid fuel ligaments comprise (U,Zr)C or (U,Nb)C. 10. The process of claim 1, wherein the solid fuel ligaments comprise a uranium tricarbide alloy selected from the group consisting of (U,Zr,Nb)C; (U,Zr,Ta)C; (U,Zr,Hf)C; and (U,Zr,W)C. 11. The process of claim 1, wherein the solid fuel ligaments comprise (U,Zr)CN or (U,Ta)CN. 12. The process of claim 1, wherein the solid fuel ligaments comprise (UWZrXNbY)CZ; where 0.04<W<0.12, 0.45<X<0.9, 0<Y<0.45, and 0.92<Z<1.0.).