Patent Number: 053848144
Section: claims

1. In a boiling water reactor fuel bundle, a debris catching grid construction for placement within a flow volume defined by a lower hollow tie plate assembly having an inlet nozzle at a lower end thereof and an upper fuel rod supporting grid at an upper end thereof, said fuel rod supporting grid providing a mechanical support connection for supporting the weight of individual fuel rods of the fuel bundle, with said flow volume defined between said inlet nozzle and said upper end rod supporting grid, the debris catching grid comprising: a three dimensional, non-planar perforated plate construction having side-by-side holes;  said perforated plate forming a three dimensional construction having a total cross sectional area exceeding the planar cross sectional area of said flow volume of said lower tie plate assembly between said inlet nozzle and said rod supporting grid; and,  means mounting said three dimensional perforated plate construction within said flow volume of said lower tie plate, such that said side-by-side holes are spaced below said upper fuel rod supporting grid, and such that a substantial portion of coolant flowing through said flow volume is caused to change direction between the inlet nozzle and the upper fuel rod supporting grid.  said means mounting said three dimensional perforated plate construction interiorly of the flow volume of said lower tie plate includes fastening the base of said pyramid to the side walls of the flow volume of said lower tie plate assembly.  means for trapping debris to said lower tie plate assembly upon cessation of flow through said lower tie plate assembly.  providing a perforated plate having an array of side-by-side holes;  forming said perforated plate into a three dimensional, non-planar construction having a dimension sufficient to be contained within said flow volume of said lower tie plate assembly, said formed three dimensional plate construction having a total cross sectional area exceeding the planar cross sectional area of the flow volume of said lower tie plate between said inlet nozzle and said rod supporting grip; and  mounting said three dimensional perforated plate construction interiorly of the flow volume of said lower tie plate, such that said side-by-side holes are spaced below said upper fuel rod supporting grid, and such that a substantial portion of a coolant flowing through said flow volume is caused to change direction between the inlet nozzle and the upper fuel rod supporting grid.  a lower tie plate assembly including a fuel rod supporting grid, an inlet nozzle, and a peripheral sidewall extending between said nozzle to the edges of said grid to define therebetween an enclosed flow volume within said lower tie plate assembly;  a plurality of upstanding fuel rods, said fuel rods supported on said rod supporting grid and extending in upstanding vertical side-by-side relation;  an upper tie plate for supporting at least some of fuel rods and providing connection to said lower tie plate through at least some of said fuel rods; the improvement comprising:  a perforated plate having side-by-side holes formed therein and forming a non-planar three dimensional construction having a total cross sectional area exceeding the planar cross sectional area of the flow volume of said lower planar cross sectional area of the flow volume of said lower tie plate between said inlet nozzle and said rod supporting grid, said side-by-side holes having a total flow area at least substantially equal to said planar cross sectional area of said flow volume; and  means mounting said three dimensional perforated plate construction interiorly of said flow volume of said lower tie plate assembly, such that said holes are spaced below said upper fuel rod supporting grid, and such that a substantial portion of a coolant flowing through said flow volume is caused to change direction between the inlet nozzle and the upper fuel rod supporting grid.  a lower tie plate assembly including an upper rod supporting grid, a lower inlet nozzle and upwardly tapering walls, said nozzle and upwardly tapering walls defining a flow volume within said lower tie plate assembly between said inlet nozzle and said rod supporting grid;  a three dimensional, non-planar perforated plate construction having side-by-side holes, said perforated plate having a total cross sectional area exceeding the planar cross sectional area of the flow volume of said lower tie plate between said inlet nozzle and said rod supporting grid, said side-by-side holes having a total flow area at least substantially equal to said planar cross sectional area of the flow volume; and,  means mounting said three dimensional perforated plate construction interiorly of the flow volume of said lower tie plate assembly, such that said holes are spaced below said upper fuel rod supporting grid, and such that a substantial portion of a coolant flowing through said flow volume is caused to change direction between the inlet nozzle and the upper fuel rod supporting grid.  said lower tie plate assembly constitutes a single one piece assembly.  said lower tie plate assembly constitutes a first separate portion constituting said rod supporting grid;  a second separate portion including walls defining said inlet nozzle and said flow volume.  said first and second separate portions are joined by welding.  said first and second separate portions are connected by threaded members,  said threaded member is a tie rod.  said threaded member is a bolt.  said means mounting said three dimensional perforated plate construction interiorly of the flow volume of said lower tie plate includes placing a portion of said three dimensional perforated plate construction between said first and second portions of said tie plate.  an upper rod supporting grid assembly;  a lower inlet nozzle assembly, said assembly defining an inlet nozzle and upwardly tapering walls, said nozzle and upwardly tapering walls defining a flow volume within said lower tie plate assembly between said inlet nozzle and said rod supporting grid;  said upper rod supporting grid assembly and said lower inlet nozzle assembly defining an interface for mating engagement therebetween to enable said pieces to define a lower tie plate assembly upon confrontation at said mating interface;  a three dimensional, non-planar perforated plate construction having side-by-side holes, said perforated plate construction having a total cross sectional area exceeding the planar cross sectional area of the flow volume of said lower tie plate assembly between said inlet nozzle and said rod supporting grid; and  means for maintaining said upper rod supporting grid assembly and said lower inlet nozzle assembly in said mating engagement at said interface with said three dimensional perforated plate therebetween, such that said holes are spaced below said upper fuel rod supporting grid, and such that a substantial portion of a coolant flowing through said flow volume is caused to change direction between the inlet nozzle and the upper fuel rod supporting grid.  said means for maintain said upper rod supporting grid assembly and said lower inlet nozzle assembly in said mating engagement includes fuel rods having threaded ends.  said means for maintain said upper rod supporting grid assembly and said lower inlet nozzle assembly in said mating engagement includes bolts, said bolts recessed below said fuel rods. 2. In a boiling water reactor fuel bundle, a debris catching grid construction according to claim 1 and wherein said three dimensional grid construction includes a dome. 3. In a boiling water reactor fuel bundle, a debris catching grid construction according to claim 1 and wherein said three dimensional grid construction includes an inverted cone with said apex of said cone positioned towards an inlet nozzle. 4. In a boiling water reactor fuel bundle, a debris catching grid construction according to claim 1 and wherein said three dimensional grid construction includes an inverted cone with said apex of said cone positioned towards said inlet nozzle with said base of said cone mounted to a cylindrical grid construction. 5. In a boiling water reactor fuel bundle, a debris catching grid construction according to claim 1 and wherein said three dimensional grid construction includes an inverted pyramid with said apex of said pyramid positioned towards said inlet nozzle; and, 6. In a boiling water reactor fuel bundle, a debris catching grid construction according to claim 1 and wherein said sidewalls of said three dimensional grid construction are corrugated. 7. In a boiling water reactor fuel bundle, a debris catching grid construction according to claim 1 and including: 8. In a boiling water reactor fuel bundle, a debris catching grid construction according to claim 7 and wherein said means for trapping debris to said lower tie plate assembly upon cessation of flow through said lower tie plate assembly includes an annulus around said inlet nozzle of said lower tie plate assembly. 9. In a boiling water reactor fuel bundle, a debris catching grid construction according to claim 7 and wherein said means for trapping debris to said lower tie plate assembly upon cessation of flow through said lower tie plate assembly includes a wall defined interiorly of said flow volume of said lower tie plate assembly. 10. In a boiling water reactor fuel bundle, a process for making and inserting a debris catching grid construction within the flow volume defined by walls of a lower tie plate assembly between an inlet nozzle and bail at a lower end thereof, and upper fuel rod supporting grid at an upper end thereof, comprising the steps of: 11. In a boiling water reactor fuel bundle, a process for inserting a debris catching grid construction according to claim 10 and wherein said mounting said three dimensional perforated plate construction interiorly of the flow volume of said lower tie plate step includes assembling said lower tie plate by placing the bail over the inlet nozzle of said lower tie plate assembly to trap said three dimensional perforated plate within the flow volume of said lower tie plate. 12. In a boiling water reactor fuel bundle, a process for inserting a debris catching grid construction according to claim 10 and wherein said mounting said three dimensional perforated plate construction interiorly of the flow volume of said lower tie plate step includes placing the upper rod supporting grid over the flow volume of said lower tie plate assembly to trap said three dimensional perforated plate within the flow volume of said lower tie plate. 13. In a boiling water reactor fuel bundle, a process for inserting a debris catching grid construction according to claim 10 and wherein said mounting said three dimensional perforated plate construction interiorly of the flow volume of said lower tie plate step includes inserting the debris catching grid construction through the walls of the flow volume of said lower tie plate assembly. 14. In a boiling water reactor fuel bundle comprising in combination: 15. A debris catching grid construction and lower tie plate assembly for use in a boiling water nuclear reactor fuel bundle comprising: 16. A debris catching grid construction and lower tie plate according to claim 15 and wherein: 17. A debris catching grid construction and lower tie plate according to claim 15 and wherein: 18. A debris catching grid construction and lower tie plate according to claim 17 and wherein: 19. A debris catching grid construction and lower tie plate according to claim 17 and wherein: 20. A debris catching grid construction and lower tie plate according to claim 19 and wherein: 21. A debris catching grid construction and lower tie plate according to claim 19 and wherein: 22. A debris catching grid construction and lower tie plate according to claim 17 and wherein: 23. A debris catching lower tie plate assembly for use in a boiling water nuclear reactor fuel bundle comprising: 24. A debris catching lower tie plate according to claim 23 and wherein: 25. A debris catching lower tie plate according to claim 23 and wherein: