Radioactive waste container.

Abstract

A radioactive waste container characterised in that it comprises: - a radionuclide containment barrier (1) including a first ferrule (11), a base (12) and a lid (14), the containment barrier defining a housing (16) for radioactive waste; - a gamma radiation shield (2) disposed externally relative to the containment barrier (1), the gamma radiation shield (2) including a second ferrule (21) having external fins (22) defining gaps (22) therebetween, an outer lid (24) and an outer bottom (26); - a neutron shielding material (shielding material is also referred to as a shield) (3) disposed in gaps defined between the fins (22) of the second ferrule.

Description

[Technical field]

[0001] The present invention relates to a container applicable for the storage of radioactive waste, in particular spent fuel from nuclear power plants. [Background technology]

[0002] In the state of the art related to the technical field of the present invention, various containers are known which can be generally classified into two types: concrete containers and metal containers. Such containers are used to protect or encase the waste canisters to be protected or the racks in which the elements involved in spent fuel storage are housed.

[0003] In metal containers, different layers of different materials are used, with a thicker layer of steel, usually forged, with a thickness of 200-300 mm, which has high mechanical capacity and its main and important function is protection against shock, seismic stress or other mechanical stress. In addition, this layer forms the containment barrier against leakage of radionuclides.

[0004] From the point of view of radiation shielding, the layer of forged steel, whose high density gives it a high shielding capacity against photonic radiation, must be supplemented with an outer shield (also called a shield) against neutron radiation, for which such steel does not provide sufficient effectiveness.

[0005] This outer shield is usually some type of neutron poison and is placed on the outer layer surrounding the steel layer and then externally protected with a metal structure to prevent damage during handling.

[0006] In vessels known from the state of the art, the steel layer used for protection against gamma radiation is usually a layer of forged steel, which is the thickest layer in proportion to the remaining layers constituting the vessel's protection system. Forged steel is more expensive than steel or cast iron and is more difficult to handle in order to produce specific shapes using dies. Summary of the Invention

[0007] The present invention relates to a container for radioactive waste, specifically intended to accommodate racks for holding radioactive waste that constitute a source of radioactive emissions. The object of the container of the present invention is to maintain a suitable ratio between the thicknesses of the different protective layers to achieve optimal protection without the need to provide thick forged steel layers.

[0008] The container of the present invention comprises: - a radionuclide containment barrier including a first ferrule, a base, and a lid, the containment barrier defining a housing for the radioactive waste; a gamma radiation shield (also called a gamma ray shield or a shield against gamma rays) including a second ferrule having external fins disposed externally relative to the containment barrier and defining gaps therebetween, an outer lid, and an outer bottom; - a neutron shielding material disposed in the gaps defined between the fins of the second ferrule.

[0009] Attachment of each ferrule, lid, and base is accomplished by conventional means.

[0010] In a preferred embodiment, the containment barrier has an upper flange and the lid has a sealing gasket secured to the upper flange by bolts.

[0011] In a preferred embodiment, the shield has a lower closure flange and an outer lid includes a sealing gasket and bolts for fastening to the upper flange of the containment barrier.

[0012] The metal portion of the containment barrier is made of forged steel.

[0013] The second ferrule, arranged around the first ferrule of the containment barrier, is a protective element against gamma radiation and is fixed to a component of the containment barrier by means of the lower closure flange.

[0014] The second ferrule is defined by a wall having external fins that define gaps that receive the neutron shielding material.

[0015] These gaps are configured in such a way that, without the presence of neutron radiation absorbing material, no direct radiation is emitted.

[0016] The lower closure flange is made of forged steel.

[0017] In accordance with the invention, the vessel is laterally provided with upper and lower forged steel trunnions fixed to the upper and lower flanges, which form a means for gripping and handling the vessel during operation.

[0018] The first and second ferrules of the containment barrier are cylindrical and concentric, allowing assembly of the second ferrule by pulling it together, one by one, through the lower region of the containment barrier, these parts being fixed together and achieving a unitary behavior by means of the lower closure flange.

[0019] According to the invention, the fins of the second ferrule are arranged longitudinally and distributed over the entire contour of the second ferrule, thus serving the purpose of acting as follows: -A thermal bridge to vent waste heat stored in the fuel elements. Structural protection of the fuel elements during an accident event, allowing higher deformations due to their cross-sectional orientation and thickness. - Protection against neutron radiation by constructing gaps in which neutron shielding material is housed.

[0020] All of the fins have a slope towards the same side relative to the radial direction of the second ferrule, so that the neutron radiation absorbing material contained between the fins significantly reduces the risk of direct emission of radiation to the outside without passing through the neutron radiation absorbing material.

[0021] Advantageously, said second ferrule is made of steel or cast iron making it possible to produce the required shape by moulding in order to define the gaps in which the neutron shielding material is introduced. [Brief description of the drawings]

[0022] To complement the description of what is carried out, and for the purpose of facilitating an understanding of the characteristics of the invention, the present description is accompanied by a set of drawings in which, by way of illustrative and non-limiting examples, the following are depicted:

[0023] [Figure 1] FIG. 1 shows a perspective view of an example of one embodiment of a radioactive waste container according to the present invention.

[0024] [Diagram 2] FIG. 2 shows an elevational view of the vessel of FIG. 1 cut along a vertical plane.

[0025] [Diagram 3] FIG. 3 shows a top view of the container of FIG. 1 cut along a horizontal plane.

[0026] [Figure 4] FIG. 4 shows a perspective view of the second ferrule of the gamma ray shield (shield against gamma rays).

[0027] [Diagram 5] FIG. 5 shows a perspective view of an alternative embodiment of a gamma radiation shield including a third ferrule disposed externally relative to the fins of the second ferrule.

[0028] [Figure 6] FIG. 6 shows a perspective view of an alternative embodiment of a gamma radiation shield in which second and third ferrules are connected by fins of the second ferrule.

[0029] [Figure 7] FIG. 7 shows an elevational view of a modified embodiment of the second ferrule, cut along a vertical plane and formed with upper and lower portions superimposed and embedded above and below by means of sockets. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] In an exemplary embodiment shown in the accompanying drawings, a radioactive waste container, which is the subject of the present invention, comprises: - a radionuclide containment barrier (1) including a first ferrule (11), a bottom (12), a top flange (13) and a lid (14) having a sealing gasket attached to the top flange (13) by bolts (15), the containment barrier defining a housing (16) for radioactive waste; - a shield against gamma radiation (also referred to as gamma ray shield) (2) arranged externally with respect to said containment barrier (1), comprising a second ferrule (21) externally including fins (22) defining gaps (22) therebetween, a lower closure flange (23), an outer lid (24) including a sealing gasket and bolts (25) for fixing the sealing gasket to the upper flange (13) of the containment barrier (1), and an outer bottom (26); - neutron shielding material (3) disposed in gaps defined between the fins (22) of the second ferrule.

[0031] The above-mentioned container for radioactive waste includes upper and lower trunnions (4) on the sides for gripping and transporting the container.

[0032] The containment barrier (1) is constructed by attaching a bottom (12) to a first ferrule (11) which is attached to the top flange (13).

[0033] The inner housing (16) of the vessel is closed by a lid (14) secured to an upper flange (13) by bolts (15).

[0034] Preferably, the second ferrule (21) arranged around the containment barrier (1) is made of cast iron or steel, which facilitates the definition of the fins (22) in the second ferrule (21) and allows it to serve the purpose of acting as follows: - A thermal bridge to evacuate the waste heat stored in the radioactive waste. - structural protection of radioactive waste in the event of an accident, by allowing higher deformations due to the orientation and thickness of the cross section of the radioactive waste. - Defining gaps (multiple) for accommodating neutron shielding material (3). - Gamma protection (protection against gamma radiation) by being made of cast iron or steel.

[0035] In the embodiment shown in Figures 1-4, the fins (22) of the second ferrule (21) have stops (27) at their ends for retaining the neutron shielding material (3) within the gaps defined between the fins (22).

[0036] In a variation of the embodiment shown in FIG. 5, the gamma radiation shield includes a third ferrule (28) around the second ferrule (21) for holding the neutron shielding material (3) within gaps defined between the fins (22) of the second ferrule (21), making it unnecessary for the fins (22) to have stops (27) or specific configurations at their ends for holding the neutron shielding material (3) therebetween.

[0037] In a variation of the embodiment shown in FIG. 6, the second ferrule (21) and the third ferrule (28) of the shield (2) are attached (glued) by fins (22) which together with the ferrules (21, 28) define gaps (multiple) for accommodating the neutron shielding material (3).

[0038] In a variant embodiment shown in Figure 7, the second ferrule (21) is formed by an upper part (21a) and a lower part (21b) which are fitted one above the other by means of a socket (21c). Each part (21a, 21b) has a corresponding fin (22a, 22b).

[0039] A lower closure flange (23) is secured to the bottom (12) of the containment barrier (1) and allows the containment barrier (1) element and the second ferrule (21) to work together.

[0040] The radioactive waste container is further protected and shielded by an outer bottom (26) secured to a lower closure flange (23) and an outer lid (24) secured to an upper flange (13) of the containment barrier (1) by bolts (25).

[0041] Having fully described the nature of the invention and exemplary preferred embodiments thereof, it is noted that changes in the materials, shape, size, and arrangement of the described elements are subject to change for all appropriate purposes, provided that such changes do not result in alteration of the essential characteristics of the invention as hereinafter claimed. [Explanation of symbols]

[0042] 1: Containment Barrier 1: Radionuclide Containment Barrier 11: First ferrule 12: Bottom 13: Upper flange 14: Lid 15: Bolt 16: Housing for radioactive waste 16: Inner housing of the container 2: Shielding against gamma rays (gamma ray shielding) 21: Second ferrule 21a: Upper part 21b: Lower part 21c:Socket 22: Finn (multiple) 22a, 22b: Fin 23: Bottom closure flange 24:Outer lid 25: Bolt 25: Sealing gasket and bolts 26:Outer bottom 27: Stop part 28: 3rd ferrule 3: Neutron shielding materials 4: Upper and lower trunnions

Claims

1. A radioactive waste container comprising: - a radionuclide containment barrier (1) including a first ferrule (11), a base (12) and a lid (14), the containment barrier defining a housing (16) for radioactive waste; - a gamma radiation shield (2) (also called a shield against gamma radiation) arranged externally to the containment barrier (1), the gamma radiation shield (2) including a second ferrule (21) having external fins (22) defining gaps (22) therebetween, an outer lid (24) and an outer bottom (26); a neutron shielding material (also referred to as a shield) (3) disposed in gaps defined between the fins (22) of the second ferrule.

2. 2. The vessel according to claim 1, characterized in that the containment barrier (1) includes an upper flange (13) and the lid (14) has a sealing gasket secured to the upper flange (13) by bolts (15).

3. 3. The vessel according to claim 1 or 2, characterized in that the bottom (12) and the top flange (13) of the containment vessel barrier (1) are fixed to the first ferrule (11).

4. 2. The vessel according to claim 1, characterized in that the shield (2) comprises a lower closure flange (23) and the outer lid (24) comprises a sealing gasket and bolts (25) for fixing it to the upper flange (13) of the containment barrier (1).

5. 5. The vessel according to claim 4, characterized in that the lower closure flange (23) is fixed to the bottom (12) of the containment barrier (1).

6. Container according to claim 4, characterized in that the outer bottom (26) is fixed to the lower closure flange (23).

7. 2. The container according to claim 1, characterized in that the fins (22) have an inclination towards the same side relative to a radial direction of the second ferrule.

8. Container according to claim 1, characterized in that it comprises upper and lower trunnions (4) on its sides for gripping and transporting the container.

9. 2. The container according to claim 1, characterized in that the first ferrule (11) is made of forged steel and the second ferrule (21) having fins (22) is made of iron or cast steel.

10. 2. The container according to claim 1, characterized in that the fins (22) of the second ferrule (21) have stoppers (27) at their ends for holding the neutron shielding material (3) in the gaps defined between the fins (22).

11. 2. The container according to claim 1, characterized in that the gamma radiation shield comprises a third ferrule (28) around the second ferrule (21) for holding the neutron shielding material (3) in the gaps (plurality) defined between the fins (plurality) (22) of the second ferrule (21).

12. 12. The container according to claim 11, characterized in that the second ferrule (21) and the third ferrule (28) of the shield (2) are connected by the fins (22) which, together with the ferrules (21, 28), define the gaps (10) for accommodating the neutron shielding material (9).

13. Container according to any one of claims 10 and 11, characterized in that the second ferrule (21) comprises an upper part (21a) and a lower part (21b) fitted one above the other by means of a socket (21c); and each part (21a, 21b) of the second ferrule has corresponding fins (22a, 22b).

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