DE8119296U1 - STORAGE DEVICE CONSISTING OF A CERMIC CONTAINER FOR THE FINAL STORAGE OF RADIOACTIVE SUBSTANCES AND A CERAMIC LID FOR THE CONTAINER - Google Patents

Description

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STEAG Kernenergie GmbH
Bismarckstrasse 54
4300 Essen 1

Keyword: mountain pressure cover
our file number: 558

/ Storage device consisting of a ceramic container / for the final storage of radioactive substances and a kerami-C see lid for the container

The invention relates to a storage device consisting of a ceramic container for the final storage of radioactive substances Substances and a ceramic lid for the container.

From KfK 3ooo, September 198o - "Comparison of the various disposal alternatives and their ability to be assessed Feasibility "- Study" Disposal alternatives ", Nuclear Research Center Karlsruhe, is one such process known. In this process, an alumina container is made extending perpendicular to the container axis free edge and a hemispherical lid made of aluminum oxide connected to one another. After hanging up the The contact area of the cover on the contact area of the container, the container and cover are made according to the so-called "HIP process" (Hot Isostatic Pressing) connected. This requires a printing press that has a special Furnace is equipped. In order to achieve a joint-free connection between the container and the lid, there is a temperature of around 135o ° C and a pressure of at least 7o MPa is required. The high temperatures and the large energies

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Quantities are not without problems for the properties of the radioactive substances packed in the container, especially if the inner container is temperature-sensitive are used. Furthermore, a low-stress can only be achieved by carefully controlling the temperature during cooling State can be achieved in the joining area leading to a monolithic structure of lid and container. This process is too complex for series packaging in hot cells and is therefore uneconomical.

It is the object of the present invention to provide a storage device of the type mentioned in the preamble of the preceding claim 1, with the one for the packed radioactive Substances and possibly containers harmless Joining temperatures and can be operated at atmospheric pressure.

This object is achieved in that container 1; 6; 19; and cover 2; 7; 20; 26 in their associated edition areas la, 2a; 6a, 7a; 19a, 20a; 25a, 26a are ground in to match each other and a shape on the container and / or non-positively supporting and acting on the cover Pretensioner 4; 8th; 22, 23, 24; 27, 28 for the purpose of prestressing the lid against the support area of the container is provided.

By grinding in and keeping the grinding under The container is kept gas-tight so that it biases

% after loading and closing from the hot cell without danger

the environment can be transported to the final repository. f- After the closed containers have been _{stored in the repository, (} f the lid is loaded after a certain time with the mountain pressure, which can be up to 300 bar, and accordingly

{■ pressed more firmly on the support area of the lid, whereby the sealing effect is increased.

When the container is closed, it is possible that the lid from the outside against the application of the biasing force Edition range of the container is printed, or that the Lid from inside against the support area of the container

is pulled.

Should the sealing effect only be achieved after a surface roughness has been reached in the support areas that are on is uneconomical to produce or the

,,; specified ceramic material for lid or container is not reachable, preferably after

; grind on at least one of the contact surfaces of A thin compensation layer made of a highly corrosion-resistant, deformable material is applied to the container and lid.

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The compensation layer can be designed as a prefabricated film or the layer can be applied directly to the Support surface are applied.

A highly corrosion-resistant, ductile Metal can be used. Titanium, platinum, gold, silver, chromium and nickel are preferred for this.

On the other hand, a deformable ceramic, preferably in the form of ceramic dusts, can be applied as the layer material will. Graphite is preferred because of its inherent sliding properties.

The following ceramic materials are preferably used as the ceramic material for the container and lid Question:

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Al ₂ O ₃ , AlpOo compounds such as cordierite (2 MgO
• 2 Al ₂ O ₃ · 5 SiO ₂ ) and mullite (3 Al ₃ O ₃ · 2 SiO ₂ ) or
Carbon or carbon compounds such as SiC.

For the storage device, it is useful if the
Support areas are rotational surfaces selected from mutually assigned straight circular ring surfaces, conical surfaces or partial spherical surfaces.

Further subclaims relate to advantageous configurations of the storage device according to the invention.

The inventive method and the inventive
Storage device should be based on the accompanying figures
will be explained in more detail. It shows:

Figure 1 shows a first embodiment of an inventive Storage device with a spherical sealing cover and a preloading this from the outside Pressure cover,

FIG. 2 shows a conical sealing cover with a pretensioning it into the interior of the container Pretensioning device,

FIG. 3 shows a third embodiment with a sealing cover provided with a spherical support area and one the sealing cover over a ring

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pressure cover acting on the seal and

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4 and 5 a further embodiment with a spherical

Sealing cover, a pretensioning device and a special protective cover.

The lower part of the containers 1, 6, 19, 25 is not shown in any of the figures. The bottom of the container can be formed in one piece with the jacket or after separate manufacture in a suitable manner, e.g. after the HIP process, be connected to the container jacket. In Figure 1 is in the container 1 near its free opening a spherical sealing surface la ground in. A spherical sealing cover lies on the spherical sealing surface la 2 with a correspondingly ground spherical sealing surface 2a. The sealing surfaces la and 2a can for example to a surface roughness R. of 1 to 0.4 ^ m be ground or lapped. If the sealing engagement between the sealing surfaces la and 2a in the ground Surface roughness is not sufficient, or if it is too uneconomical to achieve such a surface roughness (i.e. one with a roughness depth of e.g. 16 to 2.5 m den Grinding process finished), the above-mentioned leveling layer can be introduced between the sealing surfaces be. Since the thickness of the layer is too small compared to the dimensions in FIG

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Layer in the figure 1 and in the subsequent figures not taken into account in the drawing.

The partially spherical sealing cover 2 has a substantially transverse to the direction of extent of the container 1 extending biasing surface 2b. In the embodiment shown, a thin one lies on the prestressing surface 2b Buffer disk 3 made of a ductile or elastic metal, which may also contain unevenness in the cover surfaces compensates. A pressure cover 4 with an external thread 4a is screwed against the buffer disk 3 and is screwed into a corresponding Internal thread Ib of the container engages. As can be seen from the detailed illustration, have external threads 4a and internal thread Ib the game S against each other.

Furthermore, the sealing cover 2 is provided with a blind hole 2c for its manipulation with a tool, into which a compression spring 5 can be inserted after the sealing cover 2 has been inserted into the container 1.

After filling the container in the hot cell, the sealing cover 2 is inserted. After using the compression spring 5 the pressure cover 4, to which the buffer disk 3 is preferably attached, is screwed in until the buffer disk pressed evenly and the sealing surface 2a with the desired pretensioning force against the sealing surface

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before la is pressed. At the same time, the compression spring 5 compressed.

After storing the closed container in the repository mine is then caused by the mountain pressure prevailing there, e.g. in a salt mine due to the salt convergence how a hydrostatic pressure acts, the pressure cover 4 is loaded in the axial direction. Under repeal of the game S, the lid can be pushed into the container, so that the previously by the bias given contact pressure of the sealing surface 2a on the sealing surface la is significantly increased and the sealing effect is improved will. Because of the spherical design of the sealing cover eccentric axial loads can also occur when the clearance S is eliminated due to possible rotating or settling movements of the sealing cover 2 can be added without the size of the sealing engagement between the two Sealing surfaces and thus the sealing effect is reduced.

Instead of the fixed buffer disk 3 can also be on the Biasing surface 2b a powdery buffer layer are applied when the container is closed.

In the embodiment according to FIG. 2, a container 6 is provided with a conical sealing surface 6a. On the Sealing surface 6a is a sealing cover 7 with a corresponding

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corresponding conical sealing surface 7a. For all roughness depths and the application of a leveling layer Embodiments already made comments in the description of the first embodiment.

Below the conical sealing surface 6a, the container is provided with a spherical-layer-shaped groove 6c, in which a pretensioning device 8 is anchored. In the groove 6c engages a clamping ring 9 with a Slot Io is provided. On the inner surface of the clamping ring 9, two ring grooves 9a and 9b are different rectangular cross-section. In the ring grooves

spring washers 11 and 12 engage, which are provided with corresponding annular grooves 12a and 12b on the outside Hold the sleeve part 13 in the clamping ring 9. An inwardly protruding collar 13a of the sleeve part 13 is through

the central opening 13b delimits.

Inside the sleeve part 13 is a nut 14 with · | Internal thread 14a by means of a wedge 15 rotatably, but axially displaceable. The mother is through one Retaining ring 15 'secured against falling out of the sleeve part. Between the inner face of the Nut 14 and the inner annular surface of the collar 13a, two disc springs 16 are arranged. Other spring designs are possible.

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The sealing cover 7 is shown in FIG
Connected with a threaded bolt 17. This can be formed in one piece with the sealing cover. The conical sealing surface 6a of the container 6 closes
an axially parallel straight cylindrical sealing surface 6b. Opposite this sealing surface 6b is an inwardly inclined conical sealing surface 7b of the sealing cover 7. The conical sealing surface 7b goes into a free
Side of the sealing cover 7 opening, circumferential edge step 7c over.

In the so between container 6 and sealing cover 7 free
The remaining space is a ring seal 18 with an external wedge section 18a extending in the direction of the container axis and a ring section 18b extending transversely to the container and engaging in the edge step 7c. The detailed display
Figure 2 shows that the height of the ring seal 18b
is smaller than the depth of the edge step 7c, so that when the ring seal is pretensioned, a gap RS remains under the seal. Furthermore, when the container is closed, the ring section 18b does not rest on the bottom of the edge step 7c, but with its inner annular surface extending coaxially to the container axis exerts a sealing effect on the corresponding surface of the edge step 7c. In this area, the ring section 18b is provided with recesses 18c, which on the one hand like a

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Labyrinth seals act and, on the other hand, impermissibly high radial forces on the container shell due to deformation

Prevent% of the labyrinth peaks.

After filling the container 6 with radioactive material, the slotted clamping ring 9 is inserted into the container. Then the sleeve part 13, in which the threaded nut 14 and the disc spring assembly 16 are preassembled, inserted and secured against axial displacement by means of the slotted spring washers 11 and 12. The sealing cover 7 is put on and screwed to the nut 14 by means of the threaded bolt 17. Here the moves Nut 14 in the direction of the sealing cover 7, the spring assembly 16 being tensioned so that between the sealing surfaces 6a and 7a applied the desired minimum contact pressure will. Then the ring seal 18 is inserted into the gap between the sealing cover 7 and the container 6 and by means of a suitable assembly tool (punch or the like.) Pressed in (the sealing surfaces 6b and 7b are preferred also ground in). The wedge is pressed in so far that between the underside of the ring portion 18b and the top of the bottom surface of the edge step 7c, the gap RS remains.

The mountain pressure that builds up exerts on the free surface of the ring portion 18b a pressure in the axial direction

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Direction from which the ring seal 18 is tighter between the sealing surfaces 6b and 7b drives in and thus the sealing effect elevated. The magnitude of the compressive force and thus the radial force caused by the wedge shape of the ring seal Force on the container in the area of the sealing surface 6b can be made at constant external pressure by preselecting the ring surface can be set on the outside of the ring seal 18. The recesses also provide an adjustment option 18c. For the ring seal 18, such a material is selected that initially with certainty forces in the wedge section 18a are introduced before the ring section 18b is deformed. There is also a sealing element here can be used, which has a highly corrosion-resistant core 18d

made of less deformable material (e.g.) and

a casing 18e, in particular in the contact area of the sealing surfaces 6b, 7b and 7c, made of highly corrosion-resistant and having ductile material (cf. dash-dotted line in FIG. 2).

In the embodiment according to Figure 3, the container is in the vicinity of its filling opening with a partially spherical Provided sealing surface 19a. A sealing cover 2o rests with its correspondingly shaped sealing surface 2oa the sealing surface 19a. A straight cylindrical surface 19b adjoins the sealing surface 19a. As with the The embodiment according to FIG. 2 is the sealing cover 2o with an inwardly opposite one of the surface 19b

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retracted conical sealing surface 2ob and an adjoining edge step 2oc provided. In the free space between the conical sealing surface 2ob and the edge step 2oc is an annular seal 21 with a wedge section 21a and an annular section 21b introduced. This is dimensioned relative to the wedge clearance and edge step clearance so that when the ring seal is under tension, it projects beyond the free face 2od and to both surfaces the edge step 2oc has a predetermined distance.

On the free upper side of the ring section 21 is a pressure cover 22 which is dimensioned so that it can move in the axial direction along the wall 19b like a piston. (In the preceding and up to further on, only the left half of Figure 3 is considered.) With the free top of the pressure cover a spring element 23 is in engagement, which in turn is held by a clamping ring 24. The tension ring engages into an annular groove 19o provided in the annular surface 19b in the vicinity of the free opening of the container 19.

After the final storage container 19 has been filled with radioactive substances, the cover 2o is inserted. After that, the Ring seal 21 inserted and pressed in with a punch until it seals evenly on the surfaces 19a and 2oa is applied. The ring seal 21 is so dimensio-

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niert that here a gap S1 below the ring section 21b, a gap S2 between the inner surface of the ring portion 21b and the vertical surface of the edge step 2oc remains and the ring section 21c an over-

^m stood S3 over the free end face 2oc of the sealing cover

2o has. Thereafter, the pressure cover 22 is inserted until it rests on the top of the ring section 21b of the sealing element comes and the gap S3 corresponding to the projection is formed. Then the

Spring element 23 placed and by introducing the slotted Clamping ring 24 tensioned so that the desired axial prestressing force is applied. The left half FIG. 3 shows the container in the pretensioned state after loading.

If, after the final storage container has been placed in a salt mine, the salt convergence results in a uniform external pressure load on the container, as shown by the arrows on the right-hand side of FIG. which is transferred to the top of the ring portion 21b of the ring seal 21. In contrast to the embodiment according to FIG. 2, in the embodiment according to FIG

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be made of a ductile material. Because of this property, the ring seal begins at a certain point axial force applied by the cover 22, i.e. also from a defined contact pressure between the sealing surfaces 19a and 2oa to deform and flows into the annular gaps Sl and S2 between the ring seal 21 and sealing cover 2o. Here, the annular gaps in question are dimensioned so that after the pressure cover 22 has been placed on the Sealing cover 2o (after removal of the protrusion S3) the gaps S1 and S2 with the material of the ring seal 21 are filled out. After the pressure cover 22 rests on the sealing cover 2, the deformation process of the ductile Sealing material terminated and the axial forces are introduced into the sealing surfaces 19a / 2oa, so that on these Sealing surfaces an increase in the sealing effect occurs. Here, however, the sealing element continues to exercise one, its own Deformation corresponding force and thus a sealing effect on the sealing surfaces of the sealing cover and container wall the end.

In the embodiment according to FIGS. 4 and 5, the container 25 has a curved sealing surface 25a provided, to which a corresponding sealing surface 26a of a sealing cover 26 is assigned. At the bottom is the sealing cover 26 is provided with a cylindrical extension 26b, which is located at an eccentric axial BeIa-

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stung of the sealing cover 26 on the to the sealing surface 25a is supported by the subsequent straight-cylindrical container wall 25b and thus tilting of the sealing cover 26 can prevent. As in the embodiments according to FIGS. 1 and 3, a manipulation opening 26c is provided. In the upper free end face 26d several blind holes 26e are provided in an even distribution, in which compression springs 27 are arranged.

Above the sealing cover 26 is a clamping element 28. This has four external circular sector-like clamping plates 29, 3o, 31 and 32, which are described in more detail with reference to the clamping plate 29. The clamping plate 29 is with its straight-cylindrical outer wall 29a on one adjoining the sealing surface 25a towards the outside Surface 25c. The inner surface of the clamping plate 29b has two oppositely inclined conical clamping surfaces 29b and 29c on.

A clamping ring 33 cooperates with the clamping surface 29b and a clamping ring 34 cooperates with the clamping surface 29c. Both Clamping rings have on their circumference inclined conicals in opposite directions to the associated clamping surfaces of the clamping plates Clamping surfaces 33a and 33b. The inboard surfaces of the clamping rings 33 and 34 are considered to be axial extending hexagonal surfaces 33b or 34b formed,

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which are in engagement with corresponding surfaces 35a and 35b of a sleeve-like abutment 35, the central Opening is provided with an internal thread 35c. A circumferential protrudes between the hexagonal surfaces 35a and 35b Nose 35d in front of which the upper clamping ring 33 rests.

The clamping rings 33 and 34 are provided with evenly spaced bores, the bores of the bottom Clamping ring 34 are provided with an internal thread. Reach through the hole in the clamping ring 33 on top Bolt 30 into the threaded holes of the clamping ring below.

The end face 25d of the container 25, which adjoins the surface 25c, is inclined from the inside outwards. on this surface rests with a sealing surface 37a of a corresponding inclination, a protective cover 37, which with a The threaded pin 37b engages in the bore 35c of the abutment 35. The lid engages with a shoulder 37c the opening of the container 25 and has recesses 37d into which the heads of the threaded bolts 36 are located can extend into the closed protective cover. The surfaces 25d and 37a, which together are in sealing engagement, are also ground in.

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After filling the final storage container 25, the cover 26 is guided by its cylindrical extension 26b inserted into the container. Compression springs 27 are then or have already been inserted into the blind holes 26e, which in their relaxed state protrude beyond the free surface 26d of the cover 26 by predetermined amounts. Thereafter becomes the clamping element 28 without end loading of the clamping rings advanced in the direction of the sealing cover 26 until the compression springs 27 are compressed in the desired manner are and the clamping ring 34 and the clamping plates 29-32 are seated on the end face 26d. By tightening the clamping bolts 36, the clamping rings 33 and 34 are acted upon each other, which in particular by the play between the Nose 37d and the lower clamping ring 34 is possible, so that the clamping plates 29-32 urged radially outward will. The clamping element 28 is thus fixed in its position and axial forces can act on the container wall 25c transferred by frictional engagement. It should be noted that the pretensioner does not must necessarily be lowered to the contact of the clamping ring 34 on the top, if already through beforehand Compression of the spring 27 the ultimately desired biasing force is achieved. Instead of the one described so far Clamping element 28 can also use the friction sleeves according to the pending patent application P 3o4838o come.

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By the biasing device, the sealing cover 26 with an adjustable and of the spring constant of the the pressure springs used are pressed into its seat depending on the force and a minimum contact pressure is exerted, which ensures a sealing effect. Of course, other spring elements than spiral compression springs can also be used come.

Then the protective cover 37 is screwed in by means of the threaded pin 37 until its sealing surface 37a the sealing surface 25d rests.

The sealing effect between the surfaces 25d and 37a is increased by the mountain pressure. The surfaces 35d and 37a must not necessarily be inclined in the sense shown in Figure 4, for example it is also possible that the surfaces extend radially.

Should the protective cover be destroyed by long-term corrosion or should it have lost its sealing effect, the salt, which is viscous under mountain pressure, can penetrate into the upper area of the container and act directly on the sealing cover 26 and thus increase its sealing effect.

If the handling tools make it necessary, pressure cover 4, sealing cover 7, pressure cover 22 and

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Protective cover 37 still with special attack surfaces and / or openings.

If necessary, a pulling cover can also be used and simultaneously engaging a pushing pretensioner if deemed necessary, i.e. the pushing pretensioning devices according to Figures 1 and 3 can for example be combined with the pulling pretensioning device can be combined according to FIG.

In the embodiment according to FIG. 4, the compression springs 27 and the tensioning element 28 form the pretensioning device.

The sealing lids are preferably made from the same ceramic material as the container. It is also It is possible that other ceramic materials than those used for the containers are used for the lids.

In the claims and the above description, a "ceramic material" is understood to mean an inorganic, non-metallic material that is difficult to dissolve in water and is at least 30% crystalline. As a rule, the ceramic workpieces are formed from a raw material at room temperature and receive their typical material properties through a temperature treatment> 800 ° C (cf. Elektrotechnische Zeitschrift, Edition A, Vol. 91 -197o-, p. 489, 2nd paragraph). .

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summary

Method for closing a ceramic container for the final storage of radioactive substances with a ceramic Lid and storage device for carrying out the method

When storing radioactive substances in ceramic containers, these must be carried out before the containers are brought in be closed gas-tight with a lid in a repository. About the heat load that has been common up to now to avoid radioactive substances on the one hand and from the container and lid on the other hand, it is proposed that that the container (1) and the sealing lid (2) in their associated support areas (la) and (2a) must be ground in appropriately and when the Container (1) the lid (2) is held under pretension on the support area of the container. In preferred Way is after grinding on at least one of the contact surfaces of the container and lid thin leveling layer made of a highly corrosion-resistant, deformable material applied to after the technically possible and / or economically achievable extent grinding in a compensation that improves the seal to achieve the remaining roughness.

(See Figure 1)

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Claims (1)

STEAG Kernenergie GmbH "" «· '■'"'%·' .. '. Bismarckstrasse 54
Food 1 Keyword: mountain pressure cover
our file number: 558 Storage device consisting of a ceramic container for the final storage of radioactive substances and a ceramic one Lid for the container Expectations 1. Storage device consisting of a ceramic container for the final storage of radioactive substances and a ceramic lid for the container, characterized in that the container (1; 6; 19; 25) and lid (2; 7; 20; 26) in their mutually associated support areas (la, 2a; 6a, 7a; 19a, 20a; 25a, 26a) are ground in to match each other and one is on the container form-fitting and / or force-fitting supporting pretensioning device (4; 8; 22, 23, 24; 27, 28) is provided for the purpose of prestressing the lid against the support area of the container. 2. Storage device according to claim 1, characterized in that the support areas are surfaces of revolution selected from associated straight lines ::. X *. ^: ty • '· Ii · ι ·> 2 - Annular surfaces, conical surfaces or partial spherical surfaces Are. 3. Device according to claim 1 or 2, characterized in that the pretensioning device is a pressure device which acts on the cover from the outside (4; -22, 23, 24; 27, 28) that can transmit the mountain pressure to the lid. 4. Apparatus according to claim 1 or 2, characterized in that the pretensioning device is a pulling device which engages the cover from the inside (8) ■ is. 5. Storage device according to one of claims 1 to 4, characterized in that the pretensioning device ■ at least one connected between the lid and the container, having resilient element (5; 16; 23; 27) 6. Storage device according to one of claims \ _ to 5, characterized in that between the mutually engaging support areas of the container and cover a compensation layer is provided. CCI cc lic fl « ι ■ t t «· II« 7. Storage device according to one of claims 1 to 6, characterized in that in a gap between the inner wall of the container and the facing outer wall of the lid a ring seal Cl8 which can be acted upon from the outside; 21) is arranged. 8. Storage device according to claim 7, characterized in that the ring seal (21) between a pressure cover (22) and the sealing cover (20) which transmit the preload in the direction of the sealing cover is arranged such that the ring seal transmits the bias to the sealing cover and upon action • is plastically deformable from mountain pressure to the contact of the pressure cover on the sealing cover. ? · Storage device according to one of claims 1 to 8, characterized in that the ring seal (18; 21) is located on the outside and extends in the direction of the container axis extending wedge section (18a; 21a) and a ring section extending transversely to the container (18b; 21b). 10. Storage device according to one of claims 1 to 7, characterized in that between the prestressing device (4) and cover (2) a buffer layer (3) is arranged