Patent Number: 046844953
Section: claims

1. In a fuel assembly for a nuclear reactor including a plurality of nuclear fuel rods, at least one grid supporting said fuel rods in an organized array, and at least one guide thimble supporting said grid, an improved bottom nozzle disposed adjacent and below said grid, supporting said guide thimble and adapted to allow flow of liquid coolant into said fuel assembly, said improved bottom nozzle comprising: (a) means spaced below said grid and a lower end of said fuel rods and supporting said guide thimble and allowing flow of coolant into said fuel assembly;  (b) means mounted about said supporting means and extending toward but spaced from said grid and lower end of said fuel rods so as to define an open region between said supporting means and said grid and lower end of said fuel rods; and  (c) a trap disposed within said open region and on said supporting means, said trap being adapted for passage of said guide thimble therethrough to said supporting means and flow of said coolant therethrough for capturing and retaining debris carried by said flowing coolant within said trap to substantially prevent entry of debris into said fuel assembly, said trap including  a network of interconnected elongated structural members defining open spaces for flow of coolant therethrough; and  means on said members for attaching and anchoring said guide thimble thereto.  (a) a housing formed by a plurality of interconnected, upstanding side walls having upper and lower peripheral edges and adapted to rest at said lower peripheral edge thereof upon said lower core plate and spaced at said upper peripheral edge from said lowermost grid;  (b) a network of interconnected structural members disposed within said housing and extending across said housing between said side walls thereof, said members being connected to said side walls a short distance be1ow said upper peripheral edge of said housing so as to define an open region within said upper portion of said housing above said network of members and below said lowermost grid, said members together defining open space for flow of coolant therethrough to said fuel assembly;  (c) means supported on said network of members for attaching and anchoring said guide thimbles to said members; and  (d) a trap disposed within said open region and adapted for passage of said guide thimble therethrough to said network of members and the flow of said coolant therethrough for capturing and retaining debris carried by said flowing coolant within said trap to substantially prevent entry of debris into said fuel assembly, said trap including 2. The improved end nozzle as recited in claim 1, wherein said supporting means includes: 3. The improved end nozzle as recited in claim 1, wherein said finger has at least one hole defined therethrough. 4. The improved end nozzle as recited in claim 1, wherein said structure has cross-sectional dimensions sized to fit said structure within said open region and said trap further includes means on said structure for releasably locking it within said means mounted about said supporting means and defining said open region. 5. The improved end nozzle as recited in claim 4, wherein said locking means is in the form of a plurality of leaf springs disposed on the periphery of said structure and engagable with said means defining said open region. 6. In a liquid cooled nuclear reactor having a plurality of fuel assemblies supported on a lower core plate, each of said fuel assemblies and said lower core plate being constructed to allow coolant flow therethrough, said fuel assembly including a plurality of nuclear fuel rods, a plurality of grids axially disposed along and supporting said fuel rods in an organized array, and a plurality of guide thimbles supporting said grids, an improved bottom nozzle disposed adjacent a lowermost one of said grids, supporting said guide thimbles spaced above said lower core plate and adapted to allow flow of liquid coolant into said fuel assembly from said lower core plate, said improved bottom nozzle comprising: 7. The improved bottom nozzle as recited in claim 6, further comprising an elongated sleeve centrally located with respect to said network of members and connected thereto, said sleeve extending downwardly therefrom and into contact with said lower core plate for supporting said network of members thereon. 8. The improved bottom nozzle as recited in claim 6, wherein said network of members takes the form of a network of interconnected crisscross-and diagonally-extending ligaments which extend across said housing and are connected at their outer ends to said housing side walls. 9. The improved bottom nozzle as recited in claim 8, wherein said attaching and anchoring means takes the form of a plurality of bosses being supported on said network of ligaments. 10. The improved bottom nozzle as recited in claim 6, wherein said each finger has at least one hole defined therethrough. 11. The improved bottom nozzle as recited in claim 6, wherein said each wall portion has an opening formed therein at the region where said finger was punched out, said openings in said wall portions facilitating cross flow of coolant between individual ones of said cells. 12. The improved bottom nozzle as recited in claim 6, further comprising means on said structure for releasably locking it within said open region of said upper portion of said housing. 13. The improved bottom nozzle as recited in claim 12 wherein said locking means is in the form of a plurality of leaf springs disposed on the periphery of said structure and engagable within a plurality of recessed shoulders formed in said upper portion of said housing.