Patent Number: 059206020
Section: summary

The invention relates to an underground storage facility for the interim storage of waste transportable in a container, in particular radioactive waste such as spent fuel elements, with transport gallery diving access to a storage gallery for interim storage of the waste. The invention further relates to a method for interim storage of waste, in particular of spent fuel elements, in an underground storage facility with transport gallery giving access to a storage gallery, the waste being transported to the storage facility in an inner container of a transport container. Before radioactive waste such as spent fuel elements reach a final storage facility, they are frequently kept for many years in an interim storage facility. The latter is in particular an underground storage facility located inside a mountain. In the known storage facilities, storage galleries lead off from a transport gallery and the waste is deposited inside these in transport containers. Since these transport containers are very expensive, considerable financial resources are bound up in a storage facility. The dimensions of the transport containers mean that the storage galleries have to be designed fairly wide. This has the drawback that cooling air cannot flow through the storage galleries by connection at the required rate, and instead it is necessary to install special equipment in order to achieve the necessary control of the flow. Since the transport containers are arranged one behind the other inside a storage gallery, it is rather difficult to transfer the transport containers or to remove a transport container located at the front of a storage gallery, since in this case the containers at the front (when viewed from the transport gallery) have to be removed first of all. An underground storage facility for spent nuclear reactor fuel elements is known from DE 33 40 101 A1.The storage areas are inside a cavern area of elliptical cross-section. Inside this storage area the fuel elements are arranged in individual horizontal storage pipes. Cooling air lows vertically upwards through the storage area. The lower part of the cavern area of elliptical cross-section is used for air supply, and the upper part for air removal. Individual pipes branch off from the main air supply and removal pipes in order to supply the individual storage areas with cooling air. DE 39 4 65C1 describes a storage facility in which radioactive wastes are deposited in a borehole. Corresponding proposals to solve the problem can be found in WO 88/08608, EP 0 093 671B1 and DE 28 39 759A1. According to DE 24 33 168B2, caverns extend from a transverse gallery designated as the transport gallery and are used for the storage of radioactive wastes. To transport or transfer radioactive materials, loading machinery or shielding bells are known from DE 32 48 592C2 and DE 40 34 710A1. The problem underlying the present invention is to develop an underground storage facility and a method for interim storage of waste of the type mentioned at the outset such that inexpensive yet safe interim storage is possible, where a simple introduction or rapid transfer has to be possible. Cooling of the waste by convection should also be possible without any problem. The problem is solved in accordance with the invention by an underground storage facility characterized mainly in that the storage gallery runs underneath the transport gallery and is separated from the latter by a floor designed as a transport level having closable openings intended for introduction and removal of the waste. The openings are closed with locking covers having a shielding function and separating the storage gallery from the transport gallery in respect of the effects of radiation. The storage gallery has an approximately rectangular cross-section and the transport gallery an approximately semi-elliptical or semi-oval cross-section, with the width of the storage gallery being less than that of the transport gallery. Cooling of the containers containing radioactive materials and stored in the storage gallery, such as fuel element containers, is achieved by passing cooling air through the storage gallery of rectangular cross-section running underneath the floor of the transport gallery. Accordingly, cooling is achieved by a horizontally directed air flow around the stored containers. It is of course also possible for at least one storage gallery to lead off from the side of the transport gallery. Unlike in the prior art, the storage gallery and the transport gallery are arranged one above the other, allowing easy introduction or removal and hence transfer of waste via the floor openings in the transport gallery. The floor itself is preferably of concrete here, with the openings being closable with cylindrical closing covers also made of concrete. To keep rock thrusts well away from the storage gallery/galleries, a further development of the invention provides for the width of the storage gallery of preferably rectangular cross-section to be less than that of the transport gallery of approximately semi-elliptical or semi-oval cross-section. Since the storage gallery is shielded from the transport gallery, it is only necessary for the waste to be stored in an inner container, and no longer in the transport container itself once inside the storage gallery. This has the advantage that the transport container can be reused immediately after removal of the inner container. Furthermore, the width of the storage gallery compared with those in which transport containers are stored can be designed more narrow. This allows the possibility of designing the storage gallery itself as a section of the convection air duct without additional construction measures, with the storage gallery having at its end filtering devices in order to keep microorganisms or dust, for example, out of the storage area. Vertical ventilation ducts lead off from the storage gallery itself, so that a strong updraught results from the heated air. The air is heated here by the heat-generating waste such as spent fuel elements or other highly active waste. The fact that the inner containers are introduced into the storage gallery via the opening in the transport gallery means that the inner containers can be transferred inside the storage gallery in a simple manner, allowing new waste for storage to be positioned initially in the air flow that is not yet heated, hence ensuring optimum cooling possibilities and minimum waste temperatures. Cooling in accordance with the invention is achieved by the air flow passing horizontally through the storage gallery. Since the storage gallery is loaded from above, it can be designed fairly narrow, i.e. only slightly wider than the diameter of a container to be stored. This has in particular the advantage that favorable air flows result, leading to good cooling of the waste. If necessary, the storage gallery can have filtering equipment at the end. In a further noteworthy embodiment of the invention, it is provided that the waste present in an inner container is surrounded inside the transport gallery by a conveying container closing at the bottom, using which the inner container can be deposited into the storage gallery through one of the floor openings of the transport gallery. The conveying container here can have a lifting/lowering or holding device for the inner container only its inside. The covers closing the floor opening are themselves lifted/lowered by a transport carriage movable alone the floor and controllable independently of the conveying container. A method for interim storage of waste, in particular of spent fuel elements, in an underground storage facility faith transport gallery giving access to a storage gallery, where the waste is transported to the storage facility inside an inner container of a transport container, is characterized in that the inner container containing the waste is picked up in the facility or in its immediate vicinity by a movable conveying container on its floor side that moves inside the transport gallery along a floor closing the storage gallery at the top, in that after introduction of the inner container into the conveying container the latter is closed on the floor side and moved to an opening closed by a lid in the floor of the transport gallery, and in that the cover is removed, the conveying container then aligned with the opening and its floor opened, and the inner container is passed by conveying elements provided in the conveying container through the opening and into the storage gallery, then the opening is closed and the conveying container is moved to a transport container to pick up an inner container or to a further opening in the transport gallery floor to remove or transfer the inner container placed in the storage gallery. Independently of this, it is possible for the inner container to be provided with corrosion protection after removal from the storage facility so that it can then be transported to a final storage facility. Finally, it is possible once the afterheat has receded sufficiently to fill the storage gallery with bentonite, for example, so that the interim storage facility is converted into a final storage facility. Further details, advantages and features of the invention are shown not only in the claims and in the features they contain--singly and/or in combination--but also in the following description of a preferred design example shown in the drawing.