Patent Number: 051805456
Section: claims

1. A lower end nozzle of a nuclear fuel assembly, comprising an adaptor plate (2, 2', 2") having water passage holes and a bottom face, supporting feet (3, 12, 15) and a device for the retention of particles contained in the coolant flow of the reactor, in which the retention device (6, 11, 16, 30, 46) consists of a filter plate pierced with filtration holes having a smaller size than said water passage holes and being fastened against the bottom face of the adaptor plate over a substantial part of its surface. 2. The lower end nozzle as claimed in claim 1, in which the filter plate (6, 11, 16, 30, 46) is attached to the adaptor plate (2, 2', 2") by welding. 3. The lower end nozzle as claimed in claim 1, in which the filter plate (6, 11, 16, 30, 46) is attached to the adaptor plate (2, 2', 2") by brazing. 4. The lower end nozzle as claimed in claim 1, in which the filter plate (6, 11, 16, 30, 46) is attached to the adaptor plate (2, 2', 2") by riveting. 5. The lower end nozzle as claimed in claim 1, in which the filter plate (6, 11, 16, 30, 46) is attached to the adaptor plate (2, 2', 2") by means for attaching the guide tubes of the assembly to lower end nozzle. 6. The lower end nozzle as claimed in claim 1, in which the holes of the filter plate (6, 11, 16, 30, 46) are made by cutting out from the plate. 7. The lower end nozzle as claimed in any one of claims 1 to 5, in which the holes of the filter plate (6, 11, 16, 30, 46) are made by stamping. 8. The lower end nozzle as claimed in claim 1, in which the filter plate (6, 11, 16, 30, 46) has apertures (36) opposite zones of connection of guide tubes of the assembly to the adaptor plate (2, 2', 2") of the lower end nozzle (1). 9. The lower end nozzle as claimed in claim 1, in which the filter plate (30) has apertures of square form (40). 10. The end nozzle as claimed in claim 1, in which the lower filter plate (46) has apertures delimited by parallel lamellae (45). 11. The lower end nozzle as claimed in claim 1, in which the filter plate (6, 11, 16, 30, 46) has a recessed central part (35) coming in contact with a central part of the adaptor plate (2, 2', 2"), and in which the adaptor plate (2, 2', 2") has, in this zone, holes of a dimension smaller than the size of the particles to be retained, instead of water passages of larger dimension passing through the adaptor plate (2, 2', 2") in its other parts. 12. The lower end nozzle as claimed in claim 1, in which the filter plate (11) consists of a thin plate of elastic material capable of being introduced in a deformed state between the feet (12) of the lower end nozzle (10) and then placed flat against the bottom face of the adaptor plate. 13. The lower end nozzle as claimed in claim 1, in which the filter plate (16) comprises at least two parts (16a, 16b) which are introduced separately between the feet (15) of the lower end nozzle and which are placed in abutment with one another along a connecting edge (17). 14. The lower end nozzle as claimed in claim 1, in which the filter plate (6, 11, 16, 30, 46) is produced from a nickel alloy with structural hardening. 15. The lower end nozzle as claimed in claim 1, in which the filter plate (6, 11, 16, 30, 46) is produced from a martensitic steel. 16. A nuclear fuel assembly having a lower filtering end nozzle as claimed in any one of claims 1 to 6. 17. a nuclear fuel assembly having guide tubes (8) with lower ends attached to a lower end nozzle (1) having openings therethrough (41) for a coolant flow and a debris filter, said filter comprising a plate (6, 11, 16, 30, 46) attached to the bottom of the adaptor plate (2, 2', 2"), said adaptor plate comprising coolant flow apertures disposed in a square array. 18. A fuel assembly comprising a lower end nozzle (1), a first set of guide tubes (8) attached to the lower end nozzle (1) and ensuring structural rigidity of the fuel assembly, a plurality of spacer grids (9) and a second set of guide tubes (8') not attached to the lower end nozzle (1), said fuel assembly having a lower filtering end nozzle as claimed in any one of claims 1 to 6. 19. The fuel assembly according to claim 18, in which the adaptor plate (2") of the lower end nozzle (1) has passing through it an aperture (18-23) aligned with each of the guide tubes (8') of the second set, in which fuel assembly the filter plate (30) id attached to the adaptor plate (2") by means of rivets (32), each engaged in an aperture (18-33) of the adaptor plate (24) and in a corresponding aperture (37) of the filter plate.