Patent Number: 
Section: claims

1. A nuclear fuel comprising:a pellet comprised of compressed and densified grains of a fissile material selected from the group consisting of UN and U3Si2, the grains having grain boundaries; andan oxidation resistant additive coating at least a portion of the grain boundaries of the fissile material;wherein the additive has a melting point greater than the sintering temperature of the fissile material, the additive is melted into at least a portion of the grain boundaries, and the additive has a median particle size less than that of UN or U3Si2. 2. The nuclear fuel recited in claim 1 wherein the fissile material is UN, and the additive is selected from the group consisting of tungsten and alloys containing at least 50 atomic % thereof, and UO2. 3. The nuclear fuel recited in claim 1 wherein the additive is present in amounts less than 20 weight percent of the fissile material. 4. The nuclear fuel recited in claim 1 wherein the median particle size of the additive is less than 10% of the median particle size of the UN or U3Si2. 5. The nuclear fuel recited in claim 1 wherein the median particle size of the additive is less than 1% of the median particle size of the UN or U3Si2. 6. The nuclear fuel recited in claim 1 wherein the powdered fissile material is U3Si2, and the additive is selected from the group consisting of molybdenum, titanium, chromium, thorium, tungsten, niobium, and zirconium, alloys containing at least 50 atomic % thereof, BeO, and UO2. 7. A nuclear fuel comprising:a pellet comprised of compressed and densified grains of a fissile material UN, the grains having grain boundaries; andan oxidation resistant additive coating at least a portion of the grain boundaries of the fissile material;wherein the additive has a melting point lower than the sintering temperature of the fissile material, the additive is melted into at least a portion of the grain boundaries, and the additive is a borosilicate glass. 8. The nuclear fuel recited in claim 7 wherein the additive is present in amounts less than 20 weight percent of the fissile material. 9. A nuclear fuel comprising:a pellet comprised of compressed and densified grains of a fissile material U3Si2, the grains having grain boundaries; andan oxidation resistant additive coating at least a portion of the grain boundaries of the fissile material;wherein the additive has a melting point lower than the sintering temperature of the fissile material, the additive is melted into at least a portion of the grain boundaries, and the additive is a borosilicate glass. 10. The nuclear fuel recited in claim 9 wherein the additive is present in amounts less than 20 weight percent of the fissile material.