Transport container and / or storage container and method of drying transport container and / or storage container

Abstract

To provide a method of drying a transport container and / or a storage container which can remove the remaining water content from a container without difficulty, is simple, not complicated and excellent in the high drying efficiency and is used for radioactive wastes, especially used fuel elements.SOLUTION: A method of drying a transport container and / or a storage container comprises the steps of: performing drainage or machine-drainage of a container 1; and then introducing at least one kind of solid desiccant 4 into a container inner chamber 3 in order to remove the remaining water content from the container inner chamber 3, especially remove the physically and / or chemically-coupled water content. The solid desiccant 4 is the alkaline-earth salt, especially the alkaline-earth oxide.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for drying transport and / or storage containers for radioactive waste, in particular spent fuel elements, which first involves draining or mechanically draining the containers. The invention further relates to the corresponding transport and / or storage containers. In the following, instead of the terms transport and / or storage containers, the term containers will also be used for short. [Background technology]

[0002] Methods for drying transport and / or storage containers of the type mentioned at the outset are known in principle in various forms in practice and in the background art. Containers for spent fuel elements are usually loaded with the spent fuel elements in water, since water constitutes an effective shielding medium for the neutrons that are generated. For further handling, the container is generally first drained or mechanically drained. This is followed by removing the water still remaining in the container from the container by drying, in particular vacuum drying. It is usually difficult to remove the residual water content from the container. For this purpose, various drying means are known, which are usually laborious and thus also expensive. Furthermore, these drying means are notable for an insufficient drying efficiency. Summary of the Invention [Problem to be solved by the invention]

[0003] In contrast, the technical problem underlying the present application is to provide a method of the type mentioned at the outset which is distinguished by a simple, low-effort and high drying efficiency, while at the same time allowing residual moisture to be removed from the container without any problems. A further technical problem underlying the present invention is to provide a corresponding transport container and / or storage container. [Means for solving the problem]

[0004] To solve this technical problem, the present invention teaches a method for drying transport and / or storage containers used for radioactive waste, in particular spent fuel elements, which first involves draining or mechanically draining the container, followed by introducing at least one solid desiccant into the container interior in order to remove residual moisture from the container interior, in particular physically and / or chemically bound moisture, the solid desiccant being an alkaline earth salt, in particular an alkaline earth oxide.

[0005] It is within the scope of the present invention that the solid desiccant is calcium oxide or that at least 80% by weight, preferably at least 85% by weight, in particular at least 90% by weight, particularly preferably at least 95% by weight, of the solid desiccant consists of calcium oxide. Preferably, the desiccant consists entirely or essentially entirely of calcium oxide. Expediently, powdered calcium oxide is used as the desiccant. Calcium oxide has a viscosity of 800 kg / m at 20° C. 3 ~1200kg / m 3 It is within the scope of the present invention to have a bulk density of

[0006] The method according to the invention is preferably used for drying transport and / or storage containers containing spent fuel elements. The method is particularly more suitable for containers with a higher or high thermal power. Expediently, the thermal power of the container is between 12.5 kW and 42 kW, in particular between 15 kW and 40 kW, advantageously between 20 kW and 40 kW, for example between 25 kW and 40 kW. According to one embodiment, the container has a thermal power of up to 39 kW. In this connection, the method according to the invention has proven to be exceptional.

[0007] It is within the scope of the invention that the loading of the container takes place underwater, in particular the loading of the spent fuel elements underwater, and that within the scope of the method according to the invention, the container is first drained or mechanically drained. Preferably, after the drainage or mechanical drainage of the container interior, the container interior is first vacuum-dried and only then is the remaining water removed from the container interior using the desiccant according to the invention. According to a preferred embodiment of the invention, the container interior is filled with helium gas after the vacuum drying. As has been demonstrated, the container interior is filled with helium gas up to an internal pressure of 400 hPa to 1000 hPa, preferably 600 hPa to 1000 hPa, in particular 750 hPa to 950 hPa.

[0008] It is within the scope of the present invention that the desiccant or calcium oxide is introduced into the container interior after the vacuum drying. A very advantageous embodiment, which is particularly important within the scope of the present invention, is characterized in that the desiccant or calcium oxide is introduced into the container interior using at least one filter cartridge, and drying is carried out with the filter cartridge in the closed state of the container. In this case, the filter cartridge preferably extends in the longitudinal direction of the container interior of the container. According to one embodiment, the filter cartridge can extend over the entire height or length of the container interior. According to another advantageous variant, the filter cartridge extends over only a part of the length or height of the container interior.

[0009] A preferred embodiment of the method according to the invention is characterized in that the desiccant or calcium oxide, and preferably the filter cartridge containing the desiccant or calcium oxide, is arranged in the upper third of the container interior, in particular in the upper quarter of the container interior. According to a particularly advantageous variant of the method according to the invention, the arrangement takes place in the upper fifth of the container interior. In this case, the term "upper" refers to the upright position of the container with the upper or primary lid.

[0010] In order to solve the technical problem, the present invention further teaches a transport and / or storage container for radioactive waste, in particular spent fuel elements, in which at least one drying device containing at least one desiccant is provided in order to remove residual moisture contents after mechanical drainage of the container interior and after vacuum drying, the desiccant being an alkaline earth salt, in particular an alkaline earth oxide, particularly preferably calcium oxide. Expediently, the calcium oxide is present in the container interior or drying device in powder form.

[0011] A particularly advantageous embodiment of the container according to the invention is characterized in that the desiccant or calcium oxide is accommodated in at least one, in particular one, filter cartridge. Preferably, the filter cartridge is fixed, for example suspended, in the upper third, in particular in the upper quarter, particularly advantageously in the upper fifth, of the container interior. As already mentioned above, the upper third, upper quarter and upper fifth refer to the upright state of the container with the upper or primary lid. It is within the scope of the invention for the length of the filter cartridge to extend over the upper fifth or approximately the upper fifth of the fuel basket in the container interior. Such a fuel basket is used to accommodate spent fuel elements as usual. Preferably, the filter cartridge including at least one mounting element has a length of 800 mm to 1200 mm, in particular 900 mm to 1100 mm.

[0012] It is within the scope of the invention that the filter cartridge has a chamber for the desiccant, in particular calcium oxide, bounded by a water vapor permeable wall. Expediently, the water vapor permeable wall of the filter cartridge consists or essentially consists of sintered metal. This is, for example, austenitic stainless steel as sintered metal. Preferably, the water vapor permeable wall or the wall made of sintered metal of the filter cartridge has a pore size of 1 μm to 15 μm, in particular 2 μm to 12 μm, advantageously 4 μm to 12 μm. Expediently, the wall thickness of the water vapor permeable wall or the wall made of sintered metal of the filter cartridge is 0.5 mm to 6 mm, in particular 1 mm to 5 mm, advantageously 1.5 mm to 3 mm. The outer diameter of the filter cartridge (which has been found to be expedient when measured horizontally with the filter cartridge fixed) is preferably 25 mm to 60 mm, in particular 30 mm to 50 mm, for example 35 mm to 45 mm. According to one expedient embodiment of the invention, the filling volume of the filter cartridge is between 600 ml and 1200 ml, in particular between 700 ml and 1100 ml, advantageously between 800 ml and 1000 ml.

[0013] It is within the scope of the invention that the container is closed by a primary lid, Expediently, a filter cartridge is fastened to the underside of the primary lid.

[0014] The free volume of the container interior of the transport container and / or storage container according to the present invention is preferably less than 2 m 3 ~8m 3 , especially 3m 3 ~6m 3In this case, the free volume of the container means in particular the volume of the interior of the container without the fuel basket and the fuel element. In order to remove residual moisture from the container or in particular from a container having the aforementioned free volume, it has been demonstrated to use 700 g to 1200 g of desiccant, in particular 700 g to 900 g of desiccant or calcium oxide. The filter cartridge introduced into the container expediently contains 700 g to 1200 g, in particular 700 g to 900 g of desiccant or calcium oxide. It is within the scope of the invention for the filter cartridge or such a filter cartridge to have a water vapor absorption capacity of 200 g to 400 g, in particular 210 g to 300 g of water vapor. In order to be able to ascertain a sufficient degree of drying in the container interior, a measurement of the pressure rise is expediently carried out with the container closed.

[0015] The invention is based on the recognition that the method according to the invention and the transport container and / or storage container according to the invention allow for a simple, low-effort, reliable and efficient drying of the container interior. The residual moisture content in the container interior can be almost completely removed without any problems and in a reliable manner. The moisture physically and chemically bound in the container is almost completely absorbed by the desiccant or calcium oxide. The invention is based on the recognition that the water binding rate of calcium oxide is sufficient to absorb the amount of moisture that is released in the container. It should be emphasized that the implementation of the method according to the invention is relatively inexpensive. In particular, the equipment costs for drying the container interior are reduced. Furthermore, the method according to the invention is characterized by a low incidence of malfunctions. The method is particularly suitable for containers with higher or high heat output. In this respect, the method according to the invention and the container according to the invention have significant advantages compared to the measures known in practice.

[0016] The invention will now be explained in more detail with reference to the drawings, which show only one embodiment. [Brief description of the drawings]

[0017] [Figure 1]1 shows a schematic cross-sectional side view of a transport and / or storage container according to the present invention; [Diagram 2] 1 shows a schematic cross-sectional side view of a filter cartridge for use in a method according to the invention or in a container according to the invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] 1 shows a transport and / or storage container 1 according to the invention, which contains a fuel basket (not shown) containing spent fuel elements. The container is submerged and first the container 1 is drained or mechanically drained. Expediently, in the exemplary embodiment, the container 1 is fitted with a primary lid 2, which closes the container 1. Advantageously, in the exemplary embodiment, the container interior 3 of the container 1 is first vacuum dried.

[0019] According to the invention, a solid desiccant 4 is used to remove residual moisture from the container interior 3. According to an advantageous embodiment, the desiccant 4 is powdered calcium oxide. In this case, preferably in the example, the desiccant 4 or powdered calcium oxide is accommodated in a accommodating chamber 5 of a filter cartridge 6. The filter cartridge 6 is shown in more detail in FIG.

[0020] Advantageously, in the embodiment, the filter cartridge 6 is arranged in the upper fifth of the container interior 3 of the container 1. As will be demonstrated, in the embodiment, the filter cartridge 6 is suspended via a mounting device 7 on the underside of the primary lid 2. It is within the scope of the present invention that the wall defining the receiving chamber 5 of the filter cartridge 6 is water vapor permeable. Expediently, in the embodiment, this water vapor permeable wall consists of sintered metal. In this case, according to one variant of the present invention, the sintered metal can be an austenitic stainless steel. The water vapor permeable wall 8 of the filter cartridge 6 has, according to an advantageous embodiment, a wall thickness of 1 mm to 5 mm and preferably a pore size of 2 μm to 12 μm. As will be demonstrated, in the embodiment, the filter cartridge 6 including the mounting device 7 has a length of about 800 mm to 1200 mm, in particular 900 mm to 1100 mm.

[0021] The free volume of the container interior 3 of the container 1 according to the present invention is expediently 2 m 3 ~8m 3 , especially 3~m 3 ~6m 3 In this case, the free volume of the container 1 means in particular the interior volume of the container 1 without the fuel basket and the fuel element. The diameter or outside diameter of the filter cartridge 6 corresponds to only a part of the inside diameter of the container interior 3. In this case, the diameter is expediently measured in the horizontal direction with the container 1 standing upright. According to a preferred variant of the invention, the outside diameter of the filter cartridge 6 is less than one sixth, advantageously less than one eighth, of the inside diameter of the container interior 3. [Explanation of symbols]

[0022] 1 container 2 Primary lid 3 Inside the container 4. Desiccant 5. Containment Room 6 Filter Cartridge 7 Mounting device 8. Wall

Claims

1. A method for drying transport and / or storage containers (1) for radioactive waste, in particular spent fuel elements, comprising the steps of: First, the vessel (1) is drained or mechanically drained, This is followed by the introduction of at least one solid desiccant (4) into the container interior (3) in order to remove any remaining moisture from the container interior (3), in particular physically and / or chemically bound moisture, the solid desiccant (4) being an alkaline earth salt, in particular an alkaline earth oxide.

2. 2. The method according to claim 1, wherein the solid desiccant (4) is calcium oxide or at least 80% by weight, in particular at least 90% by weight, of the solid desiccant (4) consists of calcium oxide.

3. 3. The method according to claim 1 or 2, characterized in that after draining or mechanically draining the container interior (3), the container interior (3) is first vacuum-dried and then the remaining water is removed from the container interior (3) using a solid desiccant (4).

4. 4. The method according to claim 1, wherein the container interior (3) is filled with helium gas after vacuum drying.

5. 5. The method according to claim 4, wherein the container interior (3) is filled with helium gas until an internal pressure of 400 hPa to 1000 hPa, in particular 750 hPa to 950 hPa is reached.

6. 6. The method according to claim 3, wherein a desiccant (4) or calcium oxide is introduced into the vessel interior (3) after vacuum drying.

7. 7. The method according to any one of claims 1 to 6, wherein the desiccant (4) or calcium oxide is introduced into the container interior (3) by means of at least one filter cartridge (6).

8. 8. The method according to any one of claims 1 to 7, wherein a filter cartridge (6) containing a desiccant (4) or calcium oxide, and preferably a filter cartridge (6) containing a desiccant (4) or calcium oxide, is arranged in the upper third of the container (1), in particular in the upper quarter of the container (1).

9. A transport and / or storage container (1) for radioactive waste, in particular spent fuel elements, in which at least one drying device containing at least one desiccant (4) is provided in the container (1) for removing residual moisture content after mechanical drainage of the container interior (3) and subsequent vacuum drying, the desiccant (4) being an alkaline earth salt, in particular an alkaline earth oxide.

10. 10. The transport and / or storage container (1) according to claim 9, wherein the desiccant (4) is calcium oxide.

11. 11. The transport and / or storage container (1) according to claim 9 or 10, wherein the desiccant (4), in particular calcium oxide, is present in powder form.

12. 12. The transport and / or storage container (1) according to any one of claims 9 to 11, wherein the desiccant (4) is accommodated in at least one, in particular one, filter cartridge (6), which is fixed, in particular suspended, preferably in the upper third, in particular in the upper quarter and advantageously in the upper fifth of the container interior (3).

13. 13. The transport and / or storage container (1) according to claim 12, wherein the filter cartridge (6) has a receiving chamber (5) for a desiccant (4), in particular calcium oxide, which is bounded by a water vapour permeable wall (8), the water vapour permeable wall (8) of the filter cartridge (6) preferably consisting of or essentially consisting of sintered metal.

14. The transport and / or storage container (1) according to claim 13, wherein the water vapour permeable wall (8) of the filter cartridge (6) has a wall thickness of 0.5 mm to 6 mm, in particular 1 mm to 5 mm, and preferably has a pore size of 1 μm to 15 μm, in particular 2 μm to 12 μm, preferably 4 μm to 12 μm.

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