Patent Number: 060884207
Section: claims

1. A reactor core comprising: a plurality of fuel assemblies; and  a plurality of control elements disposed between said fuel assemblies and having blades defining gaps between said fuel assemblies, wherein:  a support pad at an upper portion of said channel box arranged to mutually support fuel assemblies adjacent to each other in a transverse direction.  a grid-shaped spacer arranged to hold said fuel rods in said bundle in a triangular shape.  a grid; and  a spring mechanism attached to the grid and arranged to prevent vibration of the fuel rods.  each of said fuel assemblies comprises a fuel spacer in said channel box arranged to hold said fuel rods,  said fuel rods have a fuel cladding tube filled with a fuel material, and  at least one of said channel box and said fuel cladding tube comprises a stainless steel. 2. A reactor core according to claim 1, wherein said fuel assemblies have an arrangement pitch of about 300 mm or more. 3. A reactor core according to claim 1, wherein each of said fuel assemblies further comprises: 4. A reactor core according to claim 1, wherein each of said fuel assemblies further comprises: 5. A reactor core according to claim 4, wherein said grid-shaped spacer comprises: 6. A reactor core according to claim 5, wherein said spring mechanism and said grid are integral with each other. 7. A reactor core according to claim 4, wherein said grid-shaped spacer comprises a stainless steel or inconell. 8. A reactor core according to claim 1, wherein: 9. A reactor core according to claim 8, wherein said fuel material comprises plutonium and recovery uranium. 10. A reactor core according to claim 1, wherein said fuel assemblies comprise at least a first fuel assembly with a first exothermic portion length and a second fuel assembly with a second exothermic portion length, wherein said second exothermic portion length is shorter than said first exothermic portion length. 11. A reactor core according to claim 10, wherein said first exothermic portion length is 2 m or less and said second exothermic portion length is 1 m or less. 12. A reactor core according to claim 1, wherein said fuel rods form a triangular shape. 13. A reactor core according to claim 1, wherein said channel box has a rectangular cross-section with four sides and an outer protrusion on each of said four sides. 14. A reactor core according to claim 1, wherein said channel box has a rectangular cross-section with four sides and an outer protrusion at the center of each of said four sides.