Patent Number: 059149949
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the figures of the drawings in detail and first, particularly, to FIG. 1 thereof, there is seen a fragmentary, longitudinal-sectional view of a fuel element storage rack 13 which has a carrying structure 12 with a plate 12b supported on feet 12a. A multiplicity of elongate carrying wells 23 having a square cross-sectional area are set up on the plate 12b. The carrying wells 23 extend along a main axis 7 which is perpendicular to the plane of the plate 12b. Only one carrying well 23 is illustrated for the sake of clarity. A control rod 5 of a boiling water reactor is introduced into the carrying well 23. The control rod 5 has a foot part 11 with which it sits on a bottom plate 28 of the carrying well 23. The control rod 5, which has a cruciform cross section (seen in FIG. 5) and the dish-shaped foot part 11, has a storage basket 1 slipped over it. The storage basket 1 has four inserts 2 which extend along the main axis 7 and rest on a base plate 15 that comes to rest above the foot part 11 of the control rod 5. The base plate 15 of the inserts 2 is connected to a tubular supporting element 10. The supporting element 10 surrounds the foot part 11 of the control rod 5 and is releasable fixed to the bottom plate 28 of the carrying well 23, in particular through the use of four pins. A fuel element 3 is disposed in each insert 2, although again only one of these fuel elements is illustrated for the sake of clarity. Adjacent inserts 2 are fixedly welded to one another through a plurality of connecting elements 8 which are constructed as connecting sheets 9. A geodetically upper region of each insert 2 has a locking element constructed as a drop latch 19. The drop latch 19 is rotatable about a center of rotation 20 and rests largely against the carrying well 23, in a position assumed as a result of its own weight. The carrying well 23 has a holding-down device 26 (seen in FIG. 2) geodetically above the drop latch 19. When the storage basket 1 is being lifted, it is prevented from executing an unintended upward movement due to the fact that the drop latch 19 rests against the holding-down device 26. A centering device 27 which is provided geodetically below the drop latch 19 ensures that the storage basket 1 and the control rod 5 are centered in the carrying well 23. The placement of the inserts 2, each of which receives a fuel element 3, around the cruciform control rod 5, achieves a combined and compressed intermediate storage of fuel elements 3 and control rods 5 in the fuel element storage rack 13 in a fuel element storage basin. This configuration can be obtained for any desired control rod having a cruciform cross section. The actual structure of the foot part 11 of the control rod 5 is also not important for achieving a compressed intermediate storage of fuel elements 3 and control rods 5. A compact storage of control rods 5 of the common structure is thus possible. FIG. 2 shows an upper region of FIG. 1 on an enlarged scale, in which the rotatability of the drop latch 19 about the center of rotation 20 is clearly visible. This drop latch 19 can be rotated out of a locked position by an illustrated gripping appliance 25 which is led into the insert 2 from above. The insert 2 can thereby be lifted out of the carrying well 23 past the holding-down device 26 of the carrying well 23. The insert 2 is lifted with a cruciform reinforcing element 17 in the geodetically upper region or end 16 of the insert 2 for securing the insert 2 against rotation. This reinforcing element 17 is provided with a carrying bracket 18, on which a non-illustrated lifting appliance can engage. This ensures that the carrying well 23 can be loaded with a control rod 5 and the storage basket 1 as well as the fuel elements 3 and that it can be correspondingly unloaded in a simple way. For this purpose, the fuel elements 3 and the control rod 5 likewise have corresponding carrying brackets 18a, 18b (seen in FIG. 1). The carrying bracket 18a of the fuel element 3 projects out of the carrying well 23 further than the carrying bracket 18b of the control element 5. The carrying well 23 is loaded by first inserting the control element 5, then the storage basket 1 and finally the fuel elements 3. Unloading takes place in reverse order. The storage basket 1 may also be constructed as a transport container, so that a storage basket 1 that is already loaded with fuel elements 3 can be introduced into and taken out of the carrying well 23. FIG. 3 is a cross-sectional view of a region around a holding-down device 26. The holding-down device 26 is fastened to the carrying well 23, so that locking elements 19 of two adjacent storage baskets 1 are blocked against upward movement by the holding-down device 26. FIG. 4 shows a portion of the storage rack 13 according to FIG. 1 on an enlarged scale in a region between the carrying structure 12 and the base plate 15 of the inserts 2. The meaning of the reference symbols is the same as that in FIG. 1. FIG. 5 illustrates a cross section through the storage rack 13. For the sake of clarity, only one storage basket 1, which is introduced in a corresponding carrying well 23, is shown completely. Adjacent carrying wells 23 are fixedly connected to one another through cruciform spacer elements 21. The spacer elements 21 have wings which are not orthogonal to one another. The storage basket 1 has a quadratic cross-sectional area 6. A cruciform gap 4 is formed by four inserts 2 which are disposed within a square, are symmetrical to the main axis 7 and likewise have a quadratic cross-sectional area. A cruciform control rod 5 is introduced in the gap 4, likewise symmetrically to the main axis 7. Adjacent inserts 2 are connected to one another through respective connecting sheets 9 in such a manner as to close off the cruciform gap 4, so that the inserts form a unit. A fuel element 3 is disposed within each insert. In this case, the inserts 2 surround the control rod 5. Four fuel elements 3 and one control rod 5 can be introduced in each carrying well 23 by placing the inserts 2 in such a way as to surround the control rod 5. This makes it possible to achieve a particularly compact intermediate storage of fuel elements 3 and control rods 5 of a boiling water reactor. The quadratic carrying wells 23 are disposed in the manner of a checkered pattern, with intermediate positions 24 which are formed between the carrying wells 23 and can likewise be supplied with a storage basket 1 and a control rod 5. The invention is distinguished by a storage basket which can be slipped over a cruciform control rod of a boiling water reactor. For this purpose, the storage basket preferably has four inserts which are spaced from one another and are fixedly connected to one another in such a way as to form a cruciform gap between them in which the control rod can be positioned. One control rod and four fuel elements can be accommodated in a single carrying well of a fuel element storage rack by virtue of this configuration. This achieves a particularly compact and combined intermediate storage of fuel elements and control rods of a boiling water reactor in a fuel element storage basin.