Patent Number: 047131993
Section: description

The drawing shows a depository 2 for dry storage especially interim storage, of spontaneously-heating radioactive waste and spent fuel cells. In the actual storage area there are separate storage rooms or cells 3 containing storage blocks 4 of concrete, which are made up of individual concrete blocks 6, in which several channels 8 (in FIG. 1 four channels are shown) are formed. The concrete blocks are stackable so that the channels are aligned with one another and form vertical cooling and storage channels 10 for the accommodation of tubular storage containers 12 of metal for the storage of residual heat-producing radioactive material. Several stacked concrete blocks 6 form a block segment 14. Several block segments 14 form a storage block 4. Each storage block 4 stands on a concrete base plate 16 which has transverse running cooling air channels 18 which here are formed between ribs or low walls 20 formed on the base plate 16. The cooling air channels 18 are connected with the air supply channels 22 (FIG. 3). Between the storage containers 12 and the inner wall of the channels 10 there is an annular gap 26 which connects with the cooling air channels 18. At their tops, the cooling and storage channels 10 open into an intermediate space 44 which connects to an exhaust air channel 28 through which the cooling air warmed in the depository is led off. The cooling air is supplied via shafts 30 whose inlet opening 32 is provided with filters 34 to pick up dust, micro-organisms, etc. The warmed air is exhausted via shafts or chimneys 36, the outlet openings 38 likewise being equipped with filters 40. The individual block segments 14 can, as shown schematically in FIG. 3, be braced by mean of bracing elements 42 on the base plate 16 to enhance the seismic security. The outer surface of the tubular storage containers 12 can also be provided with longitudinal ribs 43 (FIGS. 4 and 5) as cooling ribs to improve the heat dissipation. These cooling ribs 43 are preferably so designed that they at the same time serve as spacers for establishing the annular gap 26. With this design, additional spaces can be dispensed with. Cooling takes place through the air current produced by natural convection. In the annular gap 26 the air is heated and rises as in a chimney. The colder outside air flows in through the shafts 30 as cooling air. The actual storage area of the depository 2 is closed at the top by a concrete ceiling 48. Between the upper side 46 of the storage blocks 4 and the lower side of the concrete ceiling 48, an intermediate space 44 is left which at the same time constitutes a first more or less horizontally-running section of the exhaust air channels 28. As shown in FIG. 4, the concrete ceiling 48 has openings 50 that are in line with the storage and cooling channels 10 of the storage blocks 4. Through these openings the tubular storage containers 12 can be inserted into and withdrawn from the channels. The space between the underside of the concrete blocks 4 and the baseplate, that is to say, the size of the cooling air channels 18, is such that this space or the cooling air channels constitute an air feed distribution space through which the incoming air is stabilized and uniformly distributed to the annular gaps. Likewise, the space between the top side of the storage blocks 4 and the underside of the concrete ceiling is of such a size that it serves as an exhaust air space for the more uniform carrying off of the heated cooling air. The tubular storage containers 12 are provided on their outer side with several supports 52 in the form of radial arms that are distributed around the circumference (see FIG. 4, which shows a storage container with four evenly distributed supports). With these supports the storage containers are supported on the tops 54 of the top concrete blocks 56. Preferably they rest on recesses in the top 54 that in the represented embodiment have the form of annular enlargements of the top end of the channel 8. The recesses can, of course, be made individually, for example, as steps distributed around the channel end, depending on the arrangement of the supports. The upper part 60 of the storage container is enlarged in the area of the concrete ceiling 48, so that an annular shoulder or an annular transition surface 64 is formed between tube enlargement 62 and the part of the storage container under it. Into the upper part 60 of the storage container 12 there is inserted a concrete plug 66 that extends down almost to the material being stored which, in FIG. 4 for example, consists of several stacked blass ingots 67. The cross-sectional shape of the plug 66 matches that of the top of the storage container, so that the plug rests on the annular shoulder 64. The upper end of the storage container 12, extending a little above the plug 66, extends into a cylindrical enlargement 68 of the opening 50 and is closed by means of a cover 70. The enlargement 68 of the opening 50 provided with a top cover 72 that is spaced above the cover 70. In the cylindrical enlargement 68 there is also a sealing sleeve or ring 74 for sealing off the opening or the annular gap 26,80 of channel 10 against the environment. The sealing sleeve 74 is, on the one hand, inserted between storage container cover 70 and storage container 12 and, on the other hand, between top cover 72 and the wall of the enlargement 68. The sealing sleeve permits vertical movement of the part of the storage container above the support 52 due to thermal expansion without any sealing problems. The storage cells 3 are lined on the inside with an insulation 76. The size of the spaces 78 under the sealing sleeves 74 change with the thermal expansion of the storage container and thus with the change in position of the sealing sleeve. The depository 2 has a double-shell external wall 84. The space 86 between the two walls, which are made of concrete, is monitored for the penetration of water, especially of ground water. Any water that gets in is removed by pumps actuated by the monitoring means.