Patent Number: 
Section: claims

1. A base portion for use in a bottom nozzle of a fuel assembly in a nuclear reactor, the base portion comprising:a top surface;a bottom surface;a plurality of vertical walls extending between the bottom surface and the top surface, wherein the plurality of vertical walls define a plurality of non-circular passages passing between the bottom surface and the top surface through the base portion; anda plurality of debris filters extending from the top surface and spanning across a respective one of the plurality of non-circular passages, wherein each debris filter comprises a lattice structure, and wherein the plurality of debris filters are configured to extend alongside a substantial portion of a bottom of a plurality of fuel rods of the fuel assembly and in between the plurality of fuel rods of the fuel assembly. 2. The base portion of claim 1, further comprising:a plurality of thickened areas, wherein each thickened area is defined by intersecting portions of the vertical walls, wherein a thickness of the intersecting portions is greater than a thickness of the vertical walls; anda plurality of flow holes, each disposed in a respective thickened area. 3. The base portion of claim 2, wherein each flow hole comprises a tapered inlet at the bottom surface of the base portion and a tapered outlet at the top surface of the base portion. 4. The base portion of claim 3, further comprising a plurality of spring members, each spring member extending upward from a top edge of a respective vertical wall a height, wherein each spring member is structured to be engaged by two fuel rods of the fuel assembly. 5. The base portion of claim 4, wherein each spring member includes a first biasing portion which is structured to engage one of the two fuel rods and a second biasing portion which is disposed opposite the first biasing portion and which is structured to engage a second one of the two fuel rods. 6. The base portion of claim 5, wherein each of the first biasing portion and the second biasing portion are an arcuate shape. 7. The base portion of claim 1, wherein each debris filter comprises a hollow pyramid or hollow cone structure. 8. The base portion of claim 1, wherein when viewed from directly above the base portion or directly below the base portion the lattice structure of each debris filter is arranged so as to form a pattern. 9. The base portion of claim 1, further comprising a plurality of spring members, each spring member extending upward from a top edge of a respective vertical wall a height, wherein each spring member is structured to be engaged by two fuel rods of the fuel assembly. 10. The base portion of claim 9, wherein each spring member includes a first biasing portion which is structured to engage one of the two fuel rods and a second biasing portion which is disposed opposite the first biasing portion and which is structured to engage a second one of the two fuel rods. 11. The base portion of claim 10, wherein each of the first biasing portion and the second biasing portion are an arcuate shape. 12. The base portion of claim 4, wherein the plurality of spring members are integrally connected with a respective top edge of the respective vertical wall. 13. The base portion of claim 1, wherein the plurality of debris filters are integrally connected with the top surface. 14. The base portion of claim 9, wherein the plurality of debris filters are integrally connected with the top surface and the plurality of spring members are integrally connected with a respective top edge of the respective vertical wall. 15. A bottom nozzle assembly for use in a fuel assembly in a nuclear reactor, the bottom nozzle assembly comprising:a rectangular skirt portion; anda base portion as recited in claim 1 coupled to the rectangular skirt portion. 16. A fuel assembly for use in a nuclear reactor, the fuel assembly comprising:the bottom nozzle assembly of claim 15;a top nozzle;a number of guide tubes which extend longitudinally between, and are coupled to, the bottom nozzle assembly and the top nozzle; andan array of elongated fuel rods extending between the top nozzle and the bottom nozzle assembly.