Patent Number: 
Section: claims

1. A fuel rack for nuclear fuel assemblies, the fuel rack comprising:a top;a plurality of vertically-extending corners;a base plate; andan array of cells for holding fuel assemblies, the array of cells comprising:a plurality of horizontal first slotted plates slidably interlocked with one another to form a top portion of the array of cells, the plurality of first slotted plates being formed of a first material;a plurality of horizontal second slotted plates slidably interlocked with one another to form a middle portion of the array of cells, outermost ones of the second slotted plates forming an exposed external surface of the middle portion of the array of cells, each of the plurality of second slotted plates being formed of a second material, wherein the second material is a neutron absorbing material and the first and second materials are metallurgically incompatible with one another; anda plurality of horizontal third slotted plates slidably interlocked with one another to form a bottom portion of the array of cells, the plurality of third slotted plates formed of the first material and connected to a top surface of the base plate;wherein outermost ones of the slotted first, second, and third plates in the top, bottom, and middle portions are arranged perimetrically around the fuel rack, the outermost ones each comprising an outward facing major surface which collectively form planar sidewalls of the fuel rack which extend from corner to corner and from the top to the base plate of the fuel rack. 2. The fuel rack according to claim 1, further comprising a plurality of tie members extending along the exposed external surface of the middle portion of the array of cells and, an exposed external surface of the top and bottom portions of the array of cells, wherein the tie members are affixed to one or more of the plurality of first slotted plates and one or more of the plurality of third slotted plates. 3. The fuel rack according to claim 2, wherein the tie members are welded to the one or more of the plurality of first slotted plates and the one or more of the plurality of third slotted plates, and wherein the tie members are not directly affixed to any of the plurality of second slotted plates. 4. The fuel rack according to claim 3, wherein the plurality of second slotted plates comprise a plurality of first middle slotted plates and a plurality of second middle slotted plates oriented perpendicular to the plurality of first middle slotted plates, wherein each of the plurality of first middle slotted plates extends uninterrupted from a first side of the exposed external surface of the array of cells to a second side of the exposed external surface of the array of cells that is opposite the first side, and wherein each of the plurality of second middle slotted plates extends uninterrupted from a third side of the exposed external surface of the array of cells to a fourth side of the exposed external surface of the array of cells that is opposite the third side. 5. The fuel rack according to claim 1, wherein the plurality of third slotted plates are welded to the top surface of the base plate. 6. The fuel rack according to claim 1, wherein the second material is a metal matrix composite material. 7. The fuel rack according to claim 1, wherein the plurality of second slotted plates are welded together. 8. The fuel rack according to claim 1, wherein the first material is stainless steel and second material is a boron impregnated aluminum. 9. The fuel rack according to claim 1, wherein the plurality of first slotted plates are welded together and the plurality of third slotted plates are welded together. 10. The fuel rack according to claim 1, wherein the plurality of second slotted plates are stacked vertically atop one another to form the middle portion of the array of cells. 11. A nuclear fuel storage apparatus comprising:a fuel assembly having a top section, a middle section, and a bottom section, nuclear fuel being stored within the middle section; anda fuel rack comprising:a top;a plurality of vertically-extending corners;a base plate; andan array of cells, the fuel assembly located in a first cell of the array of cells, the array of cells comprising:a plurality of horizontal first slotted plates slidably interlocked with one another to form a top portion of the array of cells, the plurality of first slotted plates being formed of a first material, outermost perimetrically arranged ones of the plurality of first slotted plates forming exposed external surfaces of the middle portion of the array of cells;a plurality of horizontal second slotted plates slidably interlocked with one another to form a middle portion of the array of cells, outermost perimetrically arranged ones of the plurality of second slotted plates forming exposed external surfaces of the middle portion of the array of cells, each of the plurality of second slotted plates being formed of a second material and welded together, wherein the second material is a neutron absorbing material and the first and second materials are metallurgically incompatible, the middle section of the fuel assembly being located entirely within the middle portion of the first cell of the array of cells; anda plurality of horizontal third slotted plates slidably interlocked with one another to form a bottom portion of the array of cells, the plurality of third slotted plates formed of the first material and connected to a top surface of the base plate, outermost ones of the plurality of second slotted plates being perimetrically arranged forming exposed external surfaces of the middle portion of the array of cells;wherein the exposed external surfaces of the top, middle, and bottom portions collectively form planar sidewalls of the fuel rack which extend from corner to corner and from the top to the base plate of the fuel rack. 12. The apparatus according to claim 11, further comprising a plurality of tie members extending along the exposed external surface of the middle portion of the array of cells and the exposed external surface of the top and bottom portions of the array of cells, wherein the tie members are affixed to each of the top and bottom portions of the array of cells. 13. The apparatus according to claim 12, wherein the tie members are welded to the top and bottom portions of the array of cells, and wherein the tie members are not directly affixed to the middle portion of the array of cells. 14. The apparatus according to claim 12, wherein the plurality of second slotted plates are stacked vertically atop one another to form the middle portion of the array of cells. 15. The apparatus according to claim 11, wherein the plurality of third slotted plates are welded to the top surface of the base plate. 16. The apparatus according to claim 11, wherein the plurality of second slotted plates are constructed of a metal matrix composite material. 17. The apparatus according to claim 11, wherein the array of cells comprises a plurality of inner storage cells and a plurality of perimeter storage cells, each of the plurality of inner storage cells and each of the plurality of perimeter storage cells defined by a plurality of walls, and wherein each of the plurality of walls of each of the inner storage cells and each of the perimeter storage cells is formed of the second material within the middle portion of the array of cells. 18. The apparatus according to claim 11, wherein the plurality of first and third slotted plates are constructed of stainless steel and wherein the plurality of second slotted plates are constructed of a boron impregnated aluminum. 19. The apparatus according to claim 11, wherein the plurality of first slotted plates are welded together and the plurality of third slotted plates are welded together. 20. The apparatus according to claim 11, wherein the plurality of second slotted plates are interlocked with one another to form flux traps between adjacent cells in the array of cells. 21. A fuel rack for nuclear fuel assemblies, the fuel rack comprising:a top;a plurality of vertically-extending corners;a base plate;an array of cells for holding fuel assemblies, the array of cells comprising:a plurality of horizontal first slotted plates slidably interlocked with one another to form a top portion of the array of cells, the plurality of first slotted plates being welded together and formed of a first material;a plurality of horizontal second slotted plates slidably interlocked with one another to form a middle portion of the array of cells, the plurality of second slotted plates being formed of a second material, wherein the second material is a neutron absorbing material and the first and second materials are metallurgically incompatible; anda plurality of horizontal third slotted plates slidably interlocked with one another to form a bottom portion of the array of cells, the plurality of third slotted plates formed of the first material and welded to a top surface of the base plate;wherein outermost ones of the plurality of first, second, and third slotted plates extend perimetrically around the fuel rack, the outermost ones each comprise outward facing plates having first major surfaces that collectively form exposed external planar sidewalls of the array of cells, each sidewall extending from corner to corner and from the top to the base plate of the fuel rack; anda plurality of tie members, each tie member welded to the exposed external surface of the array of cells along each of the top and bottom portions of the array of cells. 22. The fuel rack according to claim 21, wherein the tie members are not directly affixed to any of the plurality of second slotted plates, one each of the tie members being located at one of the corners. 23. The fuel rack according to claim 21, wherein the plurality of second slotted plates are constructed of a boron impregnated aluminum and the plurality of first and third slotted plates are constructed of stainless steel. 24. The fuel rack according to claim 21, wherein the plurality of second slotted plates are welded together. 25. The fuel rack according to claim 21, wherein the array of cells comprises a plurality of storage cells including a plurality of perimeter storage cells and a plurality of inner storage cells each defined by a plurality of walls, and wherein the outward facing plates form at least one of the plurality of walls of each of the plurality of perimeter storage cells, the outward facing plates comprising second major surfaces opposite the first major surfaces, the second major surfaces facing the perimeter storage cells. 26. The fuel rack according to claim 21, wherein the exposed external surface of the array of cells comprises a first side, a second side opposite the first side, a third side extending between the first and second sides, and a fourth side extending between the first and second sides and being opposite the third side, and wherein each of the tie members is a monolithic structure located along a corner of the array of cells and extending along a portion of two adjacent sides of the exposed external surface of the array of cells. 27. The fuel rack according to claim 21, wherein a plurality of horizontally extending joints are formed between stacked tiers of the outermost ones of the slotted first, second, and third plates. 28. The fuel rack according to claim 27, wherein the horizontal extending joints extend continuously form corner to corner.