Patent Number: 043483534
Section: description

DETAILED DESCRIPTION OF THE INVENTION Reference will now be made in detail to the present preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. The inlet nozzle's upper end 11 is shown in FIGS. 1, 2 and 3. It consists of a top section 12 and bottom section 14. The top section 12 has the shape of generally equilateral polygon, and a hexagonal shape is preferred. Each side of the top section 12 has a recess 13. Preferably the recesses 13 taken together have the shape of a single generally transversely orthogonal, annular groove. The bottom section 14 has a generally cylindrical shape and contains an outside threaded portion 15. The top section 12 is coaxially secured to the bottom section 14, and they may be formed from a single piece of material. Coolant flows through the inlet nozzle's upper end 11 through at least one coolant channel 16. The duct tube's lower end 21 is shown in FIGS. 1, 2 and 4. The lower end 21 has the shape of a generally equilateral polygon which is geometrically similar to (with the same number of equilateral sides as) the polygon shape of the inlet nozzle upper end's top section 12. Preferably the duct tube has a hexagonal shape. Each of the sides of the duct tube's lower end 21 terminates in a locking tab 22 which preferably is as wide as its side. Each locking tab 22 is separated from each other, and ends with an inwardly-extending flange 23, which preferably is perpendicular to its locking tab 22. The locking tabs 22 are deflectable and can be slid over the inlet nozzle's top section 12 to the recesses 13. The flanges 23 are made to mate or engage the recesses 13. The duct tube's lower end 21 also contains an outwardly-extending protrusion 24 on each of its sides adjacent the locking tabs 22. Preferably the protrusions 24 together have the shape of a generally orthogonally transverse, annular band (support collar), each flange 23 has a width equal to that of its locking tab 22 and the locking tabs 22 are generally coaxially aligned with the duct tube during attachment. It is also preferred that the locking tabs 22 are outwardly disposed and resiliently deflectable so that they may be slid on and off the inlet nozzle upper end's top section 12 without locking tab deflection. For attachment, the locking tabs 22 would be deflected inward so that the flanges 23 engage the recesses 13. The retaining collar 30 is shown in FIGS. 1, 2 and 5. Its purpose is to restrain the flanges 23 in the recesses 13 to permit a secure attachment of the duct tube and inlet nozzle. The retaining collar 30 has a top segment 31 having the shape of a generally equilateral polygon with the same number of sides as the inlet nozzle upper end top section's 12 polygon. The top segment 31 is coaxially connected to the bottom segment 32, and they may be formed from a single piece of material. The top segment 31 surrounds and restrains the flanges 23 in the recesses 13 during attachment. The bottom segment 32 has a generally cylindrical shape and can slide over the inlet nozzle upper end's bottom section 14 to a point above at least part of the outside threaded portion 15 of the inlet nozzle upper end's bottom section 14. The sliding motion of the retaining collar 30 is stopped by the top segment 31 engaging the duct tube's protrusions 24. The locking nut 40 is shown in FIGS. 1, 2 and 6. The locking nut 40 contains an inside threaded portion 41. The locking nut 40 attaches to the inlet nozzle upper end's bottom section 14 to secure the retaining collar 30 against the duct tube's protrusions 24. The locking nut's inside threaded portion 41 engages the inlet nozzle upper end bottom section's outside threaded portion 15 to accomplish this. Means to prevent back off of the locking nut 40 are shown in FIGS. 7 and 8. In FIGS. 7a and 7b, the locking nut 40 preferably has a thin terminating annular portion 42 which can be shaped into a standard swage lock 43 to engage a locking groove 17 formed in the bottom section 14 of the inlet nozzle's upper end 11. This is the preferred technique. An alternate technique would be to form the thin annular terminating portion 42 into the shape of a standard cantilever finger lock 44 which would engage the same locking groove 19 on the bottom section 14 of the inlet nozzle's upper end 11 to prevent locking nut 40 back off. This is shown in FIGS. 8a and 8b. To attach the nuclear reactor fuel assembly duct tube to the nuclear reactor fuel assembly inlet nozzle, the locking tabs 22 are spread apart, or are made to be naturally so disposed, and the duct tube's lower end 21 is slid over the inlet nozzle upper end's top section 12 to the area of the recesses 13. Then the locking tabs 22 are pushed inward until the flanges 23 engage the recesses 13. The locking tabs 22 would be held down until the retaining collar 30 could be slid over the inlet nozzle upper end's top section 12 to restrain the flanges 23 in the recesses 13. Then the locking nut 40 would be slid over the inlet nozzle upper end's bottom section 14 and screwed on the outside threaded portion 15 until the locking nut 40 secured the retaining collar 30 against the duct tube's protrusion 24. For removal, the process would be reversed, and the locking tabs 22 would be deflected apart, if necessary, so that the flanges 23 could clear the recesses 13 to separate the duct tube from the inlet nozzle. The duct tube and inlet nozzle are designed for repeated use. When the preferred means to prevent locking nut 40 back off is used, the attached locking nut 40 would be formed into one or more swage locks 43 engaging their respective locking grooves 19. Removal would require easy breaking of the swage lock 43. Many locking grooves 19 could be employed so that new swage locks 43 could be formed each time the attachment system is used. In summary, by using locking tabs 22 on the duct tube, and recesses 13 on the inlet nozzle, a duct tube can be removably attached to an inlet nozzle in a reusable system by securing the locking tabs' flanges 23 in the recesses 13 with a retaining collar 30 and locking nut 40. This provides a reusable, economical, and rapid attachment and removal system for nuclear reactor fuel assembly duct tubes and inlet nozzles. The foregoing description of a preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention in the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiment was chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.