Patent Number: 
Section: claims

1. A nuclear fuel rod for a boiling water nuclear reactor, comprising:a cladding tube, defining a closed inner space and which is manufactured from at least one of the materials in the group zirconium and a zirconium-based alloy, the material of the cladding tube comprising a plurality of sites in which hydrogen is capable of being adsorbed;a plurality of nuclear fuel pellets, arranged in the inner space in the cladding tube so that the nuclear fuel pellets fill pan of the inner space;an initial fill gas arranged in the closed inner space in order to fill the rest of the inner space;wherein the initial fill gas contains a proportion of inert gas and a proportion of carbon monoxide, the carbon monoxide being located in the sites in which hydrogen is capable of being adsorbed, thereby blocking the sites; and whereinthe internal pressure (Pfill) of the initial gas in the nuclear fuel rod amounts to at least about 7 bar (abs) at room temperature (TR) and the proportion of carbon monoxide is at least 4.7 volume percent of the initial fill gas; andwherein the cladding tube has an inner surface that faces the inner space and the material in the cladding tube nearest the inner surface is pre-oxidized to provide a surface layer that comprises zirconium oxide. 2. A nuclear fuel rod according to claim 1, wherein the proportion of carbon monoxide constitutes at least 5 volume percent of the initial fill gas. 3. A nuclear fuel rod according to claim 2, wherein the proportion of carbon monoxide constitutes at least 6 volume percent of the initial fill gas. 4. A nuclear fuel rod according to claim 1, wherein the inert gas consists substantially of helium. 5. A nuclear fuel assembly for a boiling water nuclear reactor, said nuclear fuel assembly comprising a plurality of nuclear fuel rods, each fuel rod including:a cladding tube, defining a closed inner space and which is manufactured from at least one of the materials in the group zirconium and a zirconium-based alloy, the material of the cladding tube comprising a plurality of sites in which hydrogen is capable of being adsorbed;a plurality of nuclear fuel pellets, arranged in the inner space in the cladding tube so that the nuclear fuel pellets fill pan of the inner space;an initial fill gas arranged in the closed inner space in order to fill the rest of the inner space;wherein the initial fill gas contains a proportion of inert gas and a proportion of carbon monoxide, the carbon monoxide being located in the sites in which hydrogen is capable of being adsorbed, thereby blocking the sites; and whereinthe internal pressure (Pfill) of the fill gas in the nuclear fuel rod amounts to at least about 7 bar (abs) at room temperature (TR) and the proportion of carbon monoxide is at least 4.7 volume percent of the initial fill gas; andwherein the cladding tube has an inner surface that faces the inner space and the material in the cladding tube nearest the inner surface is pre-oxidized to provide a surface layer that comprises zirconium oxide. 6. A nuclear fuel rod for a boiling water nuclear reactor, comprising:a cladding tube, defining a closed inner space and which is manufactured from at least one of the materials in the group zirconium and a zirconium-based alloy, the material of the cladding tube comprising a plurality of sites in which hydrogen is capable of being adsorbed;a plurality of nuclear fuel pellets, arranged in the inner space in the cladding tube so that the nuclear fuel pellets fill pan of the inner space;an initial fill gas arranged in the closed inner space in order to fill the rest of the inner space;wherein the initial fill gas contains a proportion of inert gas and a proportion of carbon monoxide, the carbon monoxide being located in the sites in which hydrogen is capable of being adsorbed, thereby blocking the sites; and whereinthe internal pressure (Pfill) of the initial gas in the nuclear fuel rod amounts to at least about 6 bar (abs) at room temperature (TR) and the proportion of carbon monoxide is at least 5.7 volume percent of the initial fill gas; andwherein the cladding tube has an inner surface that faces the inner space and the material in the cladding tube nearest the inner surface is pre-oxidized to provide a surface layer that comprises zirconium oxide. 7. A nuclear fuel assembly for a boiling water nuclear reactor, said nuclear fuel assembly comprising a plurality of nuclear fuel rods, each fuel rod including:a cladding tube, defining a closed inner space and which is manufactured from at least one of the materials in the group zirconium and a zirconium-based alloy, the material of the cladding tube comprising a plurality of sites in which hydrogen is capable of being adsorbed;a plurality of nuclear fuel pellets, arranged in the inner space in the cladding tube so that the nuclear fuel pellets fill pan of the inner space;an initial fill gas arranged in the closed inner space in order to fill the rest of the inner space;wherein the initial fill gas contains a proportion of inert gas and a proportion of carbon monoxide, the carbon monoxide being located in the sites in which hydrogen is capable of being adsorbed, thereby blocking the sites; and whereinthe internal pressure (Pfill) of the initial gas in the nuclear fuel rod amounts to at least about 6 bar (abs) at room temperature (TR) and the proportion of carbon monoxide is at least 5.7 volume percent of the initial fill gas; andwherein the cladding tube has an inner surface that faces the inner space and the material in the cladding tube nearest the inner surface is pre-oxidized to provide a surface layer that comprises zirconium oxide.