Patent Number: 042886996
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. 1 there is shown a plan view of a number of storage racks indicated with the Roman FIGS. I-XI, respectively, arranged in a water pool enclosed in a tank 1 of concrete. In anyone of the spaces traced by a square drawn in the racks a fuel element may be stored. FIG. 2 shows a portion of a plan view of the rack indicated in FIG. 1 by XI, in which the top plate of the rack has been removed. The rack has been constructed of long traversing sheet elements 3 and narrow sheet elements 2 arranged between the aforesaid sheet elements 3. Hence the walls between the several cases consist of two parallel sheets including an interstice, said interstice as well as the case per se being filled with water. These two parallel sheets including the water gap determine the minimum safety distance between the fuel elements. Preferably the sheet elements consist of stainless steel having a certain boron content. The sheets of borated stainless steel absorb neutrons whereas the water gap constitutes the moderator for the neutrons. As is apparent from FIG. 2 the sheets 3 traverse the entire length of the storage rack arrangement. Between these sheets 3 there are shown keyings generally indicated by the reference numeral 4 which keyings will be described below in further detail. At their extremities the traversing sheets 3 have been screwed on bars or fillets 5. These fillets 5 extend over the entire height of the rack and have been screwed at the extremities thereof to a bottom plate and a top plate not shown in FIG. 2. Outside the outer wall 6 of the rack the narrow sheet elements extending through this outer wall have been screwed by means of lugs 8 to corresponding bars or fillets 5 likewise extending over the entire height of the storage rack. For that purpose the lugs 8 run through slots in the outer wall 6. This connection is likewise described below in further detail. As shown in FIG. 2 the outer wall 7 consists of separate narrow sheet elements provided with lugs slidably fitting into slots close to the outer edges of the traversing sheet 3. However, this outer wall 7 may also consist of a single long traversing sheet element in which case the traversing sheet elements 3 have been provided with lugs 8 slidably fitting into slots in the sheet element 7. Referring to FIGS. 3 and 5 there as shown details of an example of a keying 4, by means of which the narrow sheet elements 2 may be fastened to the traversing sheet elements 3. At the same level along the longitudinal edge all narrow sheet elements have been provided with lugs 9 slidably fitting into slots 10 of which there has been shown only one in FIG. 3 at the left hand bottom part. With reference to the above description it will be clear that each intermediate wall consists of two parallel sheet elements 2 and 3. As shown in the plan view of FIG. 5 the lugs present at the same level on the narrow sheet elements 2 extend to the slots at the same level in the traversing sheet elements 3. As shown in FIG. 3 these lugs have been arranged on one line so that only one lug of each keying has been shown. Between each two lugs 9 of a wall there have been provided connecting strips which may be slid through the slots 12 in the lugs. These may then be secured by means of an edge weld or by deformation. It is evident that the separate small welds do not affect the shape of the rack arrangement in total. Keys 13 have been slid and secured between these connecting strips 11 and the adjoining wall of the traversing sheets 3. These may be likewise secured by means of welds or deformation. With reference to FIG. 3 it will be evident that the traversing sheets 3 at the lower edges rest into slots 16 in the bottom plate 14. The lower edges of the narrow sheet elements 2 do not engage the bottom plate 14. At the upper edges each two traversing sheet elements of a partition wall include part of a beam belonging to the top plate or the upper frame 15. FIG. 4 shows the manner in which the bottom plate 14 and the upper frame 15 are secured to the narrow sheet elements 2. If desired however, this arrangement may also be applied to the traversing sheet elements 3. In each of the narrow sheet elements 2 there has been provided a slot 25 in the lower part as well as in the upper part thereof. Lugs extending from the blocks 17 fit into this slot 25. The said blocks have been provided with a boring having an internal thread in which a screw 18 may be screwed. By means of these screws 18 the narrow sheet elements 2 may be drawn onto the bottom plate 14 and onto the upper frame 15. Consequently the traversing sheet elements 3 inclusive the lower edges thereof are firmly pressed into the slot 16, whereas the upper edges thereof are going to rest against the shoulders 19 of an upper frame beam 15. The force thus exerted on the narrow sheets 2 is transferred by means of the keyings 4 to the traversing sheets 3. FIGS. 5 and 6 also show the pulling bars or fillets 5 outside the lattice arrangement. Onto these fillets 5 there have been screwed eyes of narrow sheet elements 2 extending to slots through the side wall of the rack consisting of a single traversing sheet element 3. On the other hand edges of the traversing sheets 3 have been screwed through the beams 5. These beams 5 have been provided with short bores at both the lower part and the upper part thereof, by means of which these beams or fillets 5 may be screwed against the bottom plate 14 and the upper frame 15, vide FIG. 6. This moreover contributes to a very stable rack arrangement. In accordance with the embodiment of FIGS. 3 and 5 each side wall 7 of a single case consists of a single narrow sheet element. This side wall 7 may, however, also consist of a traversing sheet element through which lugs will extend formed on the upper edges of the traversing sheet elements 3. The lugs have been fastened to the fillet 5 by means of screws. In accordance with the storage rack arrangement of FIG. 7 the intermediate walls have different widths. This possibility is created by embodying the keyings of the lugs of the narrow sheet elements 2 onto the traversing sheet elements 3 in different ways. In accordance with this arrangement there are employed narrow sheet elements 2 having lugs in the interstice between two sheet elements 3 not confronting each other but offset with respect to each other as shown in FIG. 8. These lugs 8 have been provided with slots also parallel to the traversing sheet elements 3, whereas an edge of these slots extends to the interior between the two parallel sheet elements 3. Between this edge and the opposite wall of the sheet element 3 a wedge 13 is pinched. Upon securing these wedges 13 they may be fastened by means of an edge weld to the puncheon 9 or by deformation. The traversing sheets 3 again rest in a slot in the bottom plate at 16. Where in this case the distance between these plates 3 is much smaller there is employed a single broad traversing slot instead of two separate slots as shown for the embodiment of FIG. 2. The way of securing the bottom plate 14 and the top plate not shown in these figures may be carried out in the same manner as shown for the embodiment in accordance with FIGS. 2 through 6 inclusive. With reference to FIGS. 8 and 9 there have been shown metal blocks 17 between the narrow sheet elements 2 the extending lugs of the blocks running to the opposite slots 25 provided on the lower part and, if necessary, also on the upper part of the narrow sheet elements 2 together constituting the intermediate wall. These blocks 17 on their turn have been provided with threaded bores in which a screw 18 may be screwed by means of which the sheet elements 2 may be pulled against the bottom plate 14, and, if required, against the top frame 15. Then the protruding edges of the traversing sheet elements 3 will come to rest into the slots 16 of the bottom plate and if necessary, into the slots of the top plate or against the shoulders of a top frame constituted by traverse means. With reference to FIGS. 10 and 11 there have been shown outside views of a lower edge and of the narrow lower part, respectively, of a rack in accordance with the embodiment of FIG. 7. The bottom plate 14 rests on a metal base 20 or has been united therewith to a single structure. In view of the fact that in accordance with this embodiment the traversing sheet elements 3 are closer to each other than in accordance to the embodiment of FIG. 2 there are employed in this case narrow pull rods 5 instead of the broad traversing side beams of the embodiment of FIG. 2. These rods have been provided at their bottom and the top ends with an external screw thread. These extremities run through openings in the bottom plate and in the top plate, which extremities are fastened by means of nuts 21. The narrow pull bars are provided between the lugs 8 of the narrow and long side walls, respectively. The lugs present on the two extremities of a pull bar 5 belong to the two parallel sheet elements of an interior wall. In view of the fact that in accordance with this embodiment the narrow sheet elements 2 are much further apart than the traversing sheet elements 3 there have been provided as is evident from FIG. 11, strips 22 instead of pull bars 5 on the narrow side wall. The same applies to the pull bars 5 which may be welded to the extremities of the lugs 8. In that case the pull bars 5 at the broad side walls of the rack arrangement will then preferably also have a rectangular cross section excluding the extremities thereof provided with a screw thread. The strips 22 may then be pulled against the bottom plate 14 by means of a hook joint. This hook joint may also be employed for the entire rack arrangement. With reference to FIG. 12 there has been shown another detail of the rack arrangement in accordance with FIG. 7, that is a view partially in cross section of the lower left hand part of the rack arrangement including the carrier construction. In each storage case the bottom 14 has been provided with a circular opening 23. In the other parts of this bottom plate 14 there have been provided slots 16 wherein the lower edges of the traversing sheet elements 3 will rest in case they are pulled against the bottom plate 14 by means of the screws 18 and blocks 17 of FIGS. 8 and 9. It goes without saying that the present invention is not limited to the embodiments shown in FIGS. 2 through 12 inclusive and that modifications and alterations are possible without surpassing the scope of the invention. In this respect FIG. 13 schematically shows a plan view of another embodiment of the rack arrangement according to the invention. In accordance with this embodiment the intermediate walls between the several cases are solely provided by a single sheet. In this case these cases are constituted by the traversing sheet elements 3 and the narrow sheet elements 2 mounted transversely thereto. Between the several traversing sheet elements 3 the narrow sheet elements 2 have been shifted half a pitch with respect to each other, i.e. half the width of the rectangular case. By means of lugs 9 the narrow sheet elements 2 run through slots in the traversing sheet elements 3. As described with respect to the above embodiments the lugs 9 also possess slots into which keys may be slid and pinched. In accordance with this embodiment the above described interior wall consists of only one sheet, although the distance between the several fuel elements, one of which has schematically between indicated at 24, remains sufficiently large, that is on the one hand because this rod rests against the outer edge of the lugs 9 of the narrow sheet elements 2 running through the slots in the traversing sheet elements 3 into the interior of the case. On the other hand on the walls of the narrow sheet elements 2 there have been provided strips or pins thus securing that the fuel element will be supported on the four longitudinal sides. When employing this embodiment the bottom plate and the top plate may be provided with slots for all sheet elements. Also in this case a particularly firm rack arrangement is warranted serviceing the minimum safety requirements. Contrary to a welded rack the storage rack in accordance with the invention may be assembled of prefabricated cleaned parts at the site of the storage pool within the reactor building, thus eliminating the transport of the complete voluminous rack arrangement from factory to the pool.