Patent Number: 
Section: claims

1. A ceramic nuclear fuel pellet for a nuclear reactor, wherein the nuclear fuel pellet comprises a first fissile material of UB2, wherein the boron of the UB2 is enriched to have a concentration of the isotope 11B that is higher than for natural B, wherein the concentration of the isotope 11B is at least 85% by weight,wherein the nuclear fuel pellet further comprises at least one second fissile material, the at least one second fissile material comprises UN. 2. The ceramic nuclear fuel pellet according to claim 1, wherein the concentration of the isotope 11B is at least 90% by weight. 3. The ceramic nuclear fuel pellet according to claim 1, wherein the concentration of the isotope 11B is at least 95% by weight. 4. The ceramic nuclear fuel pellet according to claim 1, wherein the concentration of the isotope 11B is at approximately 100% by weight. 5. The ceramic nuclear fuel pellet according to claim 1, wherein the nuclear fuel pellet consists of UB2. 6. The ceramic nuclear fuel pellet according to claim 1, wherein the at least one second fissile material comprises one of an actinide nitride, an actinide silicide and an actinide oxide. 7. The ceramic nuclear fuel pellet according to claim 1, wherein the first fissile material and the at least one second fissile material are mixed in the nuclear fuel pellet. 8. The ceramic nuclear fuel pellet according to claim 1, wherein the nuclear fuel pellet is a sintered nuclear fuel pellet. 9. A fuel rod comprising a cladding tube and a plurality of nuclear fuel pellets according to claim 1. 10. The fuel rod according to claim 9, wherein the fuel rod comprises a plurality of absorbing pellets comprising UB2, in which the boron of the UB2 has a concentration of the isotope 10B that is higher than in the UB2 of the first fissile material of the nuclear fuel pellets. 11. The fuel rod according to claim 10, wherein the concentration of the isotope 10B in the UB2 of the absorbing pellets is at least 25, 30, 40, 50, 60, 70, 80, 90 or 100% by weight. 12. A fuel assembly comprising a plurality of fuel rods according to claim 9.