Patent Number: 043483526
Section: description

In a tank 1 made of reinforced concrete, lined with stainless steel plate 2 and filled with water 3, there is a rack 4 which consists of several adjacent rows of rack units 5, of which only one row is visible in the drawing. Each rack unit consists of a solid bottom plate 10, with bores 11 in square division. Between the bores 11, on the underside of the bottom plate 10, mutually parallel ribs 12 are welded on, which are connected together in pairs by straps 13 (See FIG. 4). In the straps 13, threaded bores are provided, in which threaded bolts 14 with hexagonal head 15 are fitted. On the end face, the head 15 of these bolts 14 is machined slightly concave. Against this concave surface a disk 16 applies, whose upper face is convex. The bolts 14 take support through these disks 16 on the steel plate 2 of the tank bottom serving as a lining. To each of the four corners of the bottom plate is welded the end face of an angle section 20 extending upward. The four angle sections 20 are connected at their upper ends with a square frame 21 of flat iron standing upright, which is welded to the circumference of a square cover plate 25. This square cover plate has square openings 26, (See FIG. 2) aligned with the bores 11 of bottom plate 10, the sides of the openings extending parallel to the sides of the cover plate 25. In the center between adjacent rows of openings 26, on the underside of the cover plate 25, are crossing thick ribs 28, also welded to the cover plate 25. The corners between the angle sections 20 and bottom plate 10 on the one hand, and the angle sections and frame 21, on the other, are connected together by diagonally arranged traverses 30. In the corner points between four square openings 26, cross-shaped stop and guide pieces 31 for the loading device are screwed on the cover plate 25. At the edge of the cover plate 25 of a unit, similar cross-shaped stop pieces 32 are arranged, which span the adjacent cover plate and thus connect the individual units together. Under each of the square openings 26, on bottom plate 10, a vertical square receiving tube 40 is mounted, which, leaving little vertical clearance, extends up to the cover plate 25 (See FIG. 2). At the base, the receiving tubes 40 terminate in an inwardly directed flange 41 (See FIG. 3) which rests on the bottom plate 10 and defines an upwardly flaring conical bore 42 for centering the fuel element bundle and four passage holes for the bolts of screws 43. The screws 43 are fitted in matchingly arranged threaded bores of the bottom plate 10. In the four sidewalls of the square receiving tubes 40, at small distance from flange 41, rectangular cutouts 45 are provided, which serve as inlet openings for the naturally circulating water. The square openings 26 in cover plate 25 are wider than the inside contour of the receiving tubes 40 by the slight lateral clearance existing between the upper end of the receiving tubes 40 and the frame 21 or respectively the ribs 28. For capturing the neutron radiation, the square receiving tubes 40 have boron inserts not shown. When the installation is assembled, the receiving tubes 40 are screwed on the finished bottom plate 10 and only then the cover plate 25 with the frame 21 is welded onto the angle sections 20. Then the rack units 5 are introduced into the tank and adjusted there by turning the screws 14 and connected together by the stop pieces 32. After exact dimensional check, water is filled into the tank. Then charging of the receiving tubes 40 with fuel element bundles can take place, the charging device being braced against the guide pieces 31, 32 and centered. For this purpose the guide pieces 31, 32 may have guide bores or slots. In its simplest form (not shown) the rack consists merely of a bottom plate 10 with the receiving tubes 40 screwed thereon. The structure 20, 21, 30 and the cover plate 25 are eliminated. At the receiving tubes 40, the vertical straps remaining in the region of the cutouts 45 may be reinforced for example by angle sections welded on internally.