Patent Number: 051475995
Section: description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, 1 designates the fuel assembly, which is composed of a large number of long fuel rods retained by spacer lattices 2. Between the fuel rods 1 there are arranged guide tubes 3, which are also kept in predetermined positions by the spacer lattices 2. The guide tubes 3, which are somewhat longer than the fuel rods 1 and extend somewhat above and below the ends of the fuel rods, are fixed to the top tie plate 4 and the bottom tie plate 5. The detail 6, which shows the upper part of the attachment of a guide tube 3 to the top tie plate 4, is shown enlarged in FIG. 2. In FIG. 2, the upper end of the guide tube 3 is joined to a top sleeve 7 by means of a number of beads. The upper end 8 of the top sleeve 7 is somewhat reinforced and inside of this part a peripheral slot 9 is arranged. This corresponds to the previously mentioned first locking element. Through the top tie plate 4 a hole 10 is provided. Through this hole there is inserted from above a guide sleeve 11 provided with a flange 12. This guide sleeve 11 is provided with a bead 13 surrounding the sleeve 11, this bead 13 constituting the mentioned second locking element. The bead 13 is to fit into the slot 9. The guide sleeve 11 is also provided with a slit 14 (see FIG. 4). A locking sleeve 15 is inserted into the guide sleeve 11. Further, a seat 16 for the top sleeve 7 is bored in the top tie plate 4. In FIG. 6 the bead 13 of the guide sleeve has been filled up. FIG. 3 shows the upper part 8 of the top sleeve 7 with the slot 9. FIG. 4 shows the guide sleeve with the slit 14 and FIG. 5 the locking sleeve 15. The mounting operation is carried out such that the top tie plate 4 is placed on the guide tubes 3 so that the upper ends 8 of the top sleeves 7 are guided into the seats 16. Then a guide sleeve 11 is pressed down through the hole 9, whereupon the guide sleeve, because of the slit 14, rebounds so that it enters the hole in spite of the bead 13. It is pressed in so far that the bead falls down into the slot 9, the guide sleeve 11 and the top sleeve 7 thus being locked to each other. The length of the guide sleeve 11 is then adapted such that, at the very moment when the bead 13 falls down into the slot 9, the flange 12 impinges against the upper part of the top tie plate 4. In this way a stable locking of the top tie plate 4 to the guide tubes 3 is achieved. To prevent the bead 13 from being pulled out of the slot 9, a locking sleeve 15 is then inserted into the guide sleeve 11. In this way the first locking element, the slot 9, is interlocked to the second locking element, the bead 13. To ensure that also the locking sleeve 15 is not detached, it can be secured by a swelling (not shown) over the bead 13 or below the sleeve 11 in those cases where the bead 13 according to FIG. 6 is not filled. It would, of course, be possible to have other forms of locking elements between the top sleeve and the guide sleeve, such as, for example, different forms of resilient hooks or the like. When the top tie plate is to be removed, first the locking sleeves 15 and then the guide sleeves 11 are removed. Thereafter, the top tie plate 4 rests completely freely on the top sleeves 7 of the guide tubes 3.