Patent Number: 
Section: claims

1. A fuel bundle for a liquid metal cooled reactor, comprising:a channel;a nose assembly secured to a lower end of the channel;a plurality of fuel rods disposed within the channel, at least one of the fuel rods having at least one guard ring surrounding the fuel rod and spacing the fuel rod from adjacent fuel rods,wherein the at least one guard ring is only rigidly affixed to the fuel rodthe plurality of fuel rods including a first set of fuel rods and a second set of fuel rods, each of the fuel rods in the first set of fuel rods having a first pattern of one or more guard rings longitudinally arranged thereon, each of the fuel rods in the second set of fuel rods having a second pattern of one or more guard rings longitudinally arranged thereon, the first pattern being different than the second pattern. 2. The fuel bundle of claim 1, wherein the fuel rod includes more than one guard ring disposed along a longitudinal length of the fuel rod. 3. The fuel bundle of claim 1, wherein at least a first fuel rod and a second fuel rod in the plurality of fuel rods each have at least one guard ring, the guard ring of the first fuel rod being at a different longitudinal position than the guard ring of the second fuel rod. 4. The fuel bundle of claim 1, wherein at least one fuel rod of the plurality of fuel rods does not have a guard ring. 5. The fuel bundle of claim 1, further comprising:tabs extending from walls of the channel to space fuel rods in the plurality of fuel rods away from the walls of the channel. 6. The fuel bundle of claim 1, wherein the first pattern of one or more guard rings includes a first repeating pattern of more than one guard ring longitudinally arranged along each of the fuel rods in the first set of fuel rods, and the second pattern of one or more guard rings includes a second repeating pattern of more than one guard ring longitudinally arranged along each of the fuel rods in the second set of fuel rods, the first repeating pattern and the second repeating pattern being different. 7. The fuel bundle of claim 6, wherein the first repeating pattern and the second repeating pattern are different because the more than one guard ring longitudinally arranged along each of the fuel rods in the first set of fuel rods is positioned at a different axial elevation within the fuel bundle as compared to the more than one guard ring longitudinally arranged along each of the fuel rods in the second set of fuel rods. 8. The fuel bundle of claim 6, wherein,the more than one guard ring longitudinally arranged along each of the fuel rods of the first set of fuel rods includes a first plurality of guard ring subsets, the first plurality of guard ring subsets including more than two groupings of guard rings where each grouping shares a common axial elevation within the fuel bundle,the more than one guard ring longitudinally arranged along each of the fuel rods of the second set of fuel rods includes a second plurality of guard ring subsets, the second plurality of guard ring subsets including more than two groupings of guard rings where each grouping shares a common axial elevation within the fuel bundle. 9. A fuel bundle for a liquid metal cooled reactor, comprising:a channel;a nose assembly secured to a lower end of the channel;a plurality of fuel rods disposed within the channel, at least one of the fuel rods having at least one guard ring surrounding the fuel rod and spacing the fuel rod from adjacent fuel rods,wherein the plurality of fuel rods include a first set of fuel rods and a second set of fuel rods, each of the fuel rods in the first set of fuel rods has a first pattern of the one or more guard rings longitudinally arranged thereon, each of the fuel rods in the second set of fuel rods has a second pattern of the one or more guard rings longitudinally arranged thereon, the first pattern being different than the second pattern. 10. The fuel bundle of claim 9, wherein the first pattern of the one or more guard rings includes a first repeating pattern of more than one guard ring longitudinally arranged along each of the fuel rods in the first set of fuel rods, and the second pattern of the one or more guard rings includes a second repeating pattern of more than one guard ring longitudinally arranged along each of the fuel rods in the second set of fuel rods, the first repeating pattern and the second repeating pattern being different. 11. The fuel bundle of claim 10, wherein the first repeating pattern and the second repeating pattern are different because the more than one guard ring longitudinally arranged along each of the fuel rods in the first set of fuel rods is positioned at a different axial elevation within the fuel bundle as compared to the more than one guard ring longitudinally arranged along each of the fuel rods in the second set of fuel rods. 12. The fuel bundle of claim 10, wherein,the more than one guard ring longitudinally arranged along each of the fuel rods of the first set of fuel rods includes a first plurality of guard ring subsets, the first plurality of guard ring subsets including more than two groupings of guard rings where each grouping shares a common axial elevation within the fuel bundle,the more than one guard ring longitudinally arranged along each of the fuel rods of the second set of fuel rods includes a second plurality of guard ring subsets, the second plurality of guard ring subsets including more than two groupings of guard rings where each grouping shares a common axial elevation within the fuel bundle. 13. The fuel bundle of claim 1, wherein the at least one guard ring is circular. 14. The fuel bundle of claim 9, wherein the at least one guard ring is circular.