Packages comprising packaging for transporting and / or storing radioactive contents and equipped with a compact internal shock absorbing system

Abstract

The present invention relates to a package containing radioactive contents, as well as to a packaging material for transporting and / or storing said contents, the packaging material comprising an internal shock absorbing system (22) housed in a containment chamber between the radioactive contents and an axial blocking member of the chamber, the radioactive contents comprising a storage device and one or more radioactive elements. The internal shock absorbing system (22) comprises a first shock absorbing device (40) for absorption by plastic deformation and a second shock absorbing device (50a-50f) for absorption by plastic deformation associated with a radioactive mass formed of one or more radioactive elements, in order to provide shock absorption to the storage device (30), the first shock absorbing device and the second shock absorbing device operating independently of each other and designed to take into account the maximum deceleration that the storage device and the radioactive elements housed in said device can withstand.

Description

[Technical field]

[0001] The present invention relates to the field of packages for radioactive material, comprising a packaging material and a radioactive content contained within a containment chamber defined by the packaging material.

[0002] The packaging may be of the type with a removable cover, such as is used for transporting nuclear fuel assemblies, or it may consist of a case or container type packaging, the cover of which is permanently fixed to the packaging side, preferably by welding.

[0003] Within the containment chamber delimited by the packaging material, the radioactive contents include a storage device as well as one or more radioactive elements, which may be nuclear fuel assemblies, containers / cases for vitrified or technical waste, containers / cases for shells and nozzles, or cases for transporting powders (e.g. PuO2 powder).

[0004] More specifically, the invention relates to an internal shock absorbing system housed axially in the containment chamber between the radioactive contents and the axial blocking member of the package, i.e. its cover or its bottom. In this respect, it is noted that such a shock absorbing system is preferably associated with the cover of the packaging in order to protect the integrity of the containment chamber in case of an axial drop of the package. Nevertheless, such an internal shock absorbing system may also be provided simultaneously or alternatively in association with the bottom of the packaging. [Background technology]

[0005] A package for storing and / or transporting radioactive material generally comprises a packaging material having sides, a bottom and a cover as a sealed outer casing. These parts of the packaging material define a cavity for containing the radioactive contents, the so-called containment chamber, formed by a storage device that contains, for example, nuclear fuel assemblies. The storage device is usually a so-called storage basket. It comprises one or more axial compartments, each intended to contain a radioactive element, i.e. a nuclear fuel assembly in the above example. In another case where the radioactive element consists of a case and / or a container, several of them can be stacked axially in each compartment of the storage basket.

[0006] The demonstration of the safety of packaging loaded with radioactive contents is based in particular on regulatory drop tests. Thus, during an axial drop of 9 meters onto the head damper cover covering the packaging, the radioactive contents can move axially in the cavity of the packaging towards the cover due to the functional clearance between the radioactive contents and the cover. During the crushing of the head damper cover, the radioactive contents can impinge on this same cover during this drop, the so-called "axial drop". Thus, under the influence of the radioactive contents contained in the containment chamber, delayed and very large loads are created on the closing system of the removable cover of the packaging. In particular, the device for fixing the cover is substantially loaded, which can be made, for example, using a fastening screw or can be equipped with a bayonet ring.

[0007] In order to ensure the tightness of the packaging after an axial drop, it may prove necessary to limit the load transmitted by the radioactive contents on the cover by means of an internal shock absorbing system arranged in the containment chamber between the cover and the radioactive contents. The system is also a so-called internal shock absorbing system.

[0008] Typically, such a system comprises one or more damping devices by plastic deformation, such as metal foams. In order to obtain an optimal collapse of each damping device and therefore the best dissipation of the mechanical energy throughout the plastic deformation of each damping device, many solutions have already been proposed in the previous embodiments.

[0009] Among the design criteria for the internal shock absorbing system are the maximum deceleration that can be withstood by the storage basket, on the one hand, and the radioactive elements contained in this basket, on the other hand. Usually, it is the lowest maximum deceleration of the two that is retained for the design of the shock absorbing device, in addition to other criteria, such as the need to absorb all of the potential energy of the radioactive contents in case of an axial fall without the risk of a collision of the shock absorbing system, or the need to limit the load transmitted by the radioactive contents to the device for fixing the cover.

[0010] By taking into account the lowest allowable maximum deceleration, this can lead to a significant oversizing of the internal shock absorbing systems and the entire packaging, especially in the axial direction.Therefore, there remains a need to improve these internal shock absorbing systems to provide a better trade-off in terms of size, cost and performance.

[0011] Finally, it should be noted that this problem also exists for internal shock absorbing systems associated with non-removable packaging covers, such as welded case covers, or generally with non-removable packaging bottoms. Even if in these two cases there are no retention problems of the fastening devices of the closure system, as with removable covers, in some circumstances the maximum deceleration in case of an axial fall of the non-removable cover / bottom side must also be taken into account. Summary of the Invention [Problem to be solved by the invention]

[0012] In order to address this need identified above, the object of the present invention is a package comprising a radioactive content and a packaging material for transporting and / or storing said content, the packaging material comprising sides extending around a longitudinal central axis of the packaging material and a bottom and a cover respectively arranged at the axial ends of the packaging material sides and forming two axial blocking members which together with the packaging material sides define a containment chamber in which the radioactive content is accommodated, the packaging material also comprising an internal shock absorbing system housed in the containment chamber and arranged axially between the radioactive content and one of the two axial blocking members, the so-called associated axial blocking member, the radioactive content comprising a storage device as well as one or more radioactive elements, the storage device defining one or more axial compartments axially opening in the direction of the associated axial blocking member, in each of which at least one radioactive element is arranged. [Means for solving the problem]

[0013] According to the invention, the internal shock absorbing system comprises a first damping device by plastic deformation for damping the storage device and a second damping device by plastic deformation associated with a radioactive mass formed by one or more radioactive elements, the first braking device and the second braking device are arranged to operate independently of each other in the event of an axial drop of the package; The first braking device is configured to determine a first parameter: σ1 corresponding to the crush stress of this first damping device, S1, which corresponds to the working surface of the first damping device intended to be impacted axially by the storage device in the event of an axial fall of the package; M1, corresponding to the mass of the storage device intended to be braked by the first brake device; - γ1 corresponding to a first value representing the deceleration of the storage device in the event of an axial fall of the package which leads to the storage device plastically crushing the first braking device, the first deceleration representing value γ1 being determined by the following formula: γ1 = (σ1 * S1) / M1; is associated with The second braking device is configured to determine a second parameter: σ2 corresponding to the crush stress of this second damping device; S2, which corresponds to the working surface of a second damping device intended to be impacted axially by its associated radioactive mass in the event of an axial fall of the package; M2, which corresponds to the mass of the radioactive mass intended to be braked by the second brake device; - γ2 corresponding to a second value representative of the deceleration of the radioactive aggregate associated with the case of an axial drop of the package which leads to the radioactive aggregate plastically crushing the second braking device, the second deceleration representative value γ2 being determined by the following formula: γ2 = (σ2 * S2) / M2; is associated with The first parameter and the second parameter are such that the second deceleration representative value γ2 is different from the first deceleration representative value γ1.

[0014] The present invention makes it possible to have an effective internal shock absorbing system with sufficient compactness, which is improved compared to the prior art embodiments, by taking into account the differentiated maximum permissible decelerations, on the one hand, for the storage device and, on the other hand, for one or more nuclear fuel assemblies, preferably a radioactive assembly formed of one or more radioactive elements, such as one single assembly.

[0015] Thus, to improve the overall compactness, each of the independent damping devices can be designed as small as possible. In other words, the invention is built on the observation that the radioactive elements can withstand higher decelerations than the storage devices that house them, and vice versa. The second associated damping device can therefore have a higher crushing stress, or a larger active area, and therefore can adopt a smaller axial height, which is synonymous with reduced size and higher compactness. These advantageous measures can be adopted while complying with the maximum allowable deceleration of the radioactive elements and being able to absorb all of these potential energies without the risk of collision of the second damping device.

[0016] Preferably, the invention provides for the implementation of one or more of the following optional features, considered separately or in any combination.

[0017] Preferably, the ratio |γ2−γ1| / min(γ2,γ1) is greater than 1.1.

[0018] Preferably, the internal shock absorbing system comprises one or more other secondary damping devices by plastic deformation, each associated with a separate radioactive mass formed of one or more other radioactive elements; The first and second parameters of the first and second braking devices are such that a second deceleration representative value γ2 associated with each of at least some of the second braking devices, preferably each of all of these second braking devices, is different from a first deceleration representative value γ1 associated with the first braking device.

[0019] Preferably, the radioactive mass associated with the or each secondary braking device is formed of one single radioactive element.

[0020] Preferably, each radioactive element is a nuclear fuel assembly, preferably a new fuel assembly, even more preferably of the MOX type, or a vitrified waste or technical waste container / case, or a shell and nozzle container / case, or a case for transporting powder.

[0021] Preferably, the or each second damping device is formed of one single damping material block, preferably made of metal foam, wood, honeycomb or using a metal tubular structure. Alternatively, each second damping device may comprise several blocks spaced apart from one another and acting independently in case of an axial drop of the package. In any case, all of the blocks preferably have the same crushing stress for damping the radioactive element.

[0022] Preferably, the first damping device is formed of several blocks of damping material spaced apart from one another, preferably made of foam, wood, honeycomb or using a metal tubular structure. Preferably, all of these damping blocks associated with the storage device have the same crushing stress. Alternatively, the first damping device can be formed of one single damping material block.

[0023] Preferably, said blocks are cylindrical or have a pyramidal shape.

[0024] Preferably, the crushing stress σ2 of the or each second braking device is different from the crushing stress σ1 of the first braking device. Alternatively, the same crushing stress may be maintained for the first and second braking devices without departing from the scope of the invention. In this case, the differentiated deceleration of the entity is controlled by the extent of the working surfaces of the first and second braking devices or by the mass of the storage device and each radioactive aggregate.

[0025] Preferably, the first damping device and the or each second damping device all have the same or substantially the same axial thickness, for example a thickness variation in the range of at most 10% can be tolerated between a maximum and a minimum value.

[0026] Preferably, the first damping device and the or each second damping device are arranged in the same transverse plane of the package.

[0027] Preferably, the first braking device and the or each second braking device are arranged within the same casing.

[0028] Preferably, the storage device includes an apertured head plate and the internal shock absorbing system is preferably fixed to said apertured head plate, alternatively, the internal shock absorbing system may be fixed to an associated axial blocking member, for example the cover of the packaging material, or may simply be freely located between the storage basket and the associated axial blocking member.

[0029] Preferably, the associated axial blocking member is the cover of the packaging, preferably removably attached to a side of the packaging. Alternatively, the associated axial blocking member is the bottom of the packaging. Indeed, even if there is no problem of retaining the screws of the closure system on the bottom side, the control of the deceleration in case of an axial drop on the bottom side can also be taken into account in some circumstances.

[0030] Other advantages and features of the present invention will appear in the following non-limiting detailed description.

[0031] This description is made with reference to the accompanying drawings. [Brief description of the drawings]

[0032] [Figure 1] 1 is a schematic axial cross-sectional view of a package according to a preferred embodiment of the present invention; [Diagram 2]FIG. 2 is a perspective view of the radioactive contents shown in the previous figure, in accordance with a preferred embodiment of the present invention. [Diagram 3] FIG. 2 is a perspective view of an internal shock absorbing system installed in the package shown in FIG. 1. [Figure 4] FIG. 2 is an exploded perspective view of the internal shock absorbing system shown in the previous figure. [Diagram 5] FIG. 4 is a perspective view of an internal shock absorbing system similar to that of FIG. 3, with one of the two half casings removed for clarity. [Figure 6] 6 is a cross-sectional view of the internal shock absorbing system according to plane P of FIG. 5, passing through the end of the damping block. [Figure 7] FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Referring initially to FIG. 1, there is shown a package 100 for storing and / or transporting radioactive contents 12 in the form of a preferred embodiment of the present invention.

[0034] Firstly, the package 100 comprises a wrapping 1 with a side 2, a bottom 4 and a removable cover 6 sealing the opening of the wrapping opposite the bottom 4. The wrapping has a central longitudinal axis 8 around which the side 2 extends, said axis 8 passing through the cover 6 and the bottom 4 arranged at the front and rear ends of the wrapping side 2, respectively. As shown diagrammatically in FIG. 1, the bottom 4 may be made integral with the wrapping side 2. The cover 6 is then placed at the front end of the side 2, which corresponds to the top end of the wrapping in the vertical position shown in FIG. 1. Preferably, the fastening of the cover 6 is performed using screw elements 14 arranged around the periphery of the cover.

[0035] The sides 2, cover 6, and bottom 4 define a containment chamber 10 that is used to contain radioactive contents 12. The cover 6 and bottom 4 thus form two opposing axial blocking members of the containment chamber 10.

[0036] The radioactive contents 12, also centered on the axis 8, comprise a storage device and one or more radioactive elements, here nuclear fuel assemblies, preferably fresh fuel such as MOX fuel. Instead of nuclear fuel assemblies, the radioactive elements in the context of the present invention can alternatively consist of vitrification waste containers / cases, shell and nozzle containers / cases, or cases for transporting powders. In these alternatives, the containers / cases housed in the storage device are also sealed.

[0037] As shown by the dotted lines in FIG. 1, at the ends of the package considered according to the direction of the axis 8, the wrapping material may be equipped with a damper cowl 20 protecting the removable cover 6 and the bottom 4 of the wrapping material, respectively.

[0038] The packaging 1 is also equipped with an internal shock absorbing system 22 specific to the invention, which is only diagrammatically shown in Fig. 1. This internal shock absorbing system 22 is accommodated in the containment chamber 10 axially between an internal surface 24 of the cover 6 and an axial end surface 26 of the radioactive contents 12. Preferably, the internal shock absorbing system 22 is fixed to the axial end surface 26 of the radioactive contents 12, for example using threaded elements or by welding. It can alternatively be fixed to the internal surface 24 of the cover 6 or be freely positioned between the radioactive contents 12 and the cover 6.

[0039] Thus, the internal shock absorbing system 22 may be disposed in several ways between the radioactive contents 12 and its associated axial blocking member formed by the removable cover 6 .

[0040] 2, there is shown a storage device / basket 30 and a radioactive content 12 comprising nuclear fuel assemblies 32a-32f. Each of these assemblies 32a-32f is disposed within a compartment 34 defined by the basket 30. The compartment 34 is axially open at an open head plate 36 of the basket, where an internal shock absorbing system is intended to be fixed. Due to its open nature, the head plate 36 thus forms the axial end of the compartment 34. The axial end face 26 of the radioactive content 12 is thus formed by the flat outer surface of the head plate 36 and the axial end faces of the assemblies 32a-32f that lie adjacent to or in the same plane as the flat outer surface of the head plate 36.

[0041] One of the features of the invention is the separation and independence of the means used to brake the basket 30 on the one hand and each of the assemblies 32a-32f on the other hand in case of an axial fall of the package on the cover side. This feature is explained with reference to figures 3 to 7 which show the internal shock absorbing system 22 which generally comprises a first braking device by plastic deformation for braking the basket 30 and a second braking device by plastic deformation associated with each of the assemblies 32a-32f. In this preferred embodiment, each nuclear fuel assembly 32a-32f therefore forms, in the context of the claimed invention, a radioactive assembly (assembly as such) consisting of a single radioactive element.

[0042] The first damping device 40 is here formed by several cylindrical blocks 40a-40e arranged around the substantially cylindrical shock absorbing system 22 and centered on the axis 8. Each of the blocks 40a-40e is thus cylindrical with an axis perpendicular or substantially perpendicular to the flat outer surface 26 of the head plate 36 in the direction in which they are oriented. They are spaced apart from one another and are preferably made of foam, wood, honeycomb or using a metal tubular structure, preferably with the same crushing stress σ1 (in MPa).

[0043] The acting surface S1 of the first braking device 40 (unit: m2 ) corresponds to the surfaces of the blocks 40a-40e intended to be impacted axially by the flat outer surface 26 of the head plate 36 in the event of an axial drop of the package. More specifically, this action surface S1 corresponds to the action surfaces S1 of all the blocks 40a-40e forming the first braking device 40. 1a ~S 1e These surfaces S 1a ~S 1e corresponds to the axial lower ends of the blocks 40a to 40e, all of which are very preferentially planar or substantially planar, perpendicular or substantially perpendicular to the axis 8 and coplanar. If these axial lower ends of the blocks 40a to 40e are not flat, then each working surface S 1a ~S 1e corresponds to the projection plane of the axial lower end of the block considered, in a plane perpendicular to the axis 8, and according to the orientation of this same axis.

[0044] Also, due to the cylindrical nature of the block, each working surface S 1a ~S 1e also corresponds in terms of dimensions and shape to any cross section of its corresponding block 40a-40e. Alternatively, the block may have a pyramidal shape, in which case the working surface varies according to the thickness of the block and thus produces a lower deceleration at the beginning of the impact. In this case, the general principle of the invention, in which the first and second parameters are such that the second deceleration representative value γ2 differs from the first deceleration representative value γ1, is always observed during the axial drop of the package, which leads to the radioactive assemblies plastically crushing the first and second damping devices.

[0045] These working surfaces are shown diagrammatically in a cross section in FIG. 6 taken at or substantially near the plane of these surfaces, perpendicular to axis 8, and are also partially visible in FIG.

[0046] A mass M1 (in kg) corresponding to the mass of the basket 30 intended to be braked by the first braking device 40.

[0047] Thus, using the above-mentioned parameters for this first damping device 40, a value of γ1 is determined corresponding to a first value representative of the deceleration of the basket 30 in the event of an axial drop of the package which leads to this basket plastically crushing the first damping device 40. This first deceleration representative value γ1 is determined by the following formula: γ1=(σ1*S1) / M1.

[0048] As mentioned above, the internal shock absorbing system 22 also includes several second damping devices 50a-50f, each associated with one of the assemblies 32a-32g, for damping the assembly in case of an axial drop of the package. The second damping devices 50a-50f are therefore independent of each other and also of the blocks of the first damping device 40. This results in that in case of an axial drop of the package, each of these elements is free to plastically deform, without being hindered by the deformation of other elements located at a distance. This independence of the blocks during crushing is obtained in particular due to the absence of plates for distributing the loads found in some solutions of the prior art, usually placed between the shock absorbing system and the radioactive contents.

[0049] In this preferred embodiment of the invention, all of the second braking devices 50 are identical, so only one of them will be described in detail below.

[0050] Each second damping device is here formed by a single cylindrical block 50a-50f, the blocks being distributed around and in the center of the shock absorbing system 22 according to the same distribution as the assemblies 32a-32f. The blocks 50a-50f are therefore cylindrical with axes perpendicular or substantially perpendicular to the flat outer surface 26 of the head plate 36 and to the axial end faces of the nuclear fuel assemblies in the direction in which these blocks 50a-50f are oriented. The blocks 50a-50f are spaced apart from each other and from the blocks of the first damping device 40. They are preferably made of foam, wood or honeycomb, preferably having the same crushing stress σ2 (in MPa) and which itself is preferably different from the above-mentioned crushing stress σ1.

[0051] The acting surface S2 (unit: m 2 ) corresponds to the surface of the block intended to be placed axially in abutment against the axial end face of the associated assembly 32a-32f in case of an axial drop of the package. This surface S2 is therefore formed by the axial lower ends of the braking blocks 50a-50f, which are very preferentially planar or substantially planar and perpendicular or substantially perpendicular to the axis 8. Preferably, all of the working surfaces S2 are also coplanar. If this axial lower end of the braking block is not flat, the working surface S2 corresponds to the projection of the axial lower end of this block in a plane perpendicular to the axis 8, according to the direction of this same axis.

[0052] Due to the cylindrical nature of the blocks, the working surface S2 also corresponds in size and shape to any cross section of its corresponding block 50a-50f. In the axial view, this working surface S2 also preferably corresponds in size and shape to the size and shape of the axial end face of the associated aggregate 32a-32f, with a practical perfect or almost perfect correspondence between these two faces in the direction of the axis 8. Nevertheless, the working surface S2 can have smaller or larger dimensions without departing from the scope of the invention.

[0053] The working surfaces S2 are shown diagrammatically in a section in FIG. 6 taken in or substantially near the plane of these surfaces, perpendicular to the axis 8, one of which is also visible in FIG.

[0054] The mass M2 (in kg) then corresponds to the mass of each nuclear fuel assembly 32a-32f intended to be braked by the second braking device 50a-50f located on the axially opposite side.

[0055] Thus, using the above-mentioned parameters for each of these second braking devices 40, a value of γ2 is determined which corresponds to a second value representing the deceleration of each assembly 32a-32f, and in the event of an axial drop of the package which leads to this assembly plastically crushing its associated second braking device, the second deceleration representing value γ2 is determined by the following formula: γ2=(σ2*S2) / M2.

[0056] By virtue of the proposed design, the aforementioned first and second parameters are advantageously selected such that the second deceleration representative value γ2 is different from the first deceleration representative value γ1. In this respect, the ratio |γ2-γ1| / min(γ2,γ1) is preferably greater than 1.1.

[0057] This leads to a reduction in the overall size of the internal shock absorbing system 22, since the maximum allowable deceleration of the basket 30, and that of each of the assemblies 32a-32f, which is often higher than the deceleration of the basket, is taken into particular consideration. Thus, to improve overall compactness, each of the independent damping devices 40, 50a-50f can be designed as small as possible.

[0058] The design is also maintained by adapting the extent of the working surfaces S1, S2 such that all of the blocks 40a-40e, 50a-50f are located in the same cross-section of the package and have the same or substantially the same axial thickness. Nevertheless, the blocks 50a-50f may alternatively include an axial thickness greater than that of the blocks 40a-40e by extending axially into the basket compartment while passing through the openings in the apertured head plate 36.

[0059] In the case of the first assumption, this in particular makes it possible to facilitate the encapsulation of these blocks 40a-40e, 50a-50f in the same substantially cylindrical casing 54, which is shown in Fig. 3 and corresponds to the external casing of the internal shock absorbing system 22. This casing 54 may be made using two half casings 54a, 54b welded to the axial central part of the system 22 and closed at its two axial ends by two disk-shaped plates 58a, 58b, which are also visible in Fig. 4 and Fig. 5. It should be noted that on this casing 54, the closing plate 58b, placed opposite / in contact with the radioactive contents, remains thin so as to maintain the independence of the actions of the different damping blocks 40a-40e, 50a-50f by plastic deformation. In other words, this plate 58b does not ensure the function of a load distribution plate in case of an axial fall of the package. Within the casing, the working surfaces S1, S2 of blocks 40a-40e, 50a-50f are intended to contact the inner surface of plate 58b, although for clarity, an axial clearance is maintained in the illustration of FIG. 7.

[0060] Naturally, the skilled person can make various modifications to the invention described merely as a non-limiting example and whose scope is defined by the appended claims. For example, the packaging 1 can include a non-removable cover, for example welded to the packaging side, so as to form a sealed case enclosing the basket and the radioactive element, this case also being a so-called "canister". Furthermore, an internal shock absorbing system according to the invention can be associated with the bottom part 4 of the packaging without departing from the scope of the invention. [Explanation of symbols]

[0061] 1 Packaging material 2 Packaging side 4 Bottom 6 Cover 8 Longitudinal central axis 10 Confinement chamber 12 Radioactive contents 14 Screw elements 20 Dampa Cowl 22 Internal shock absorption system 24 Inside of cover 6 26 Axial end face of radioactive content 12, flat outer surface 30 Storage Units / Baskets 32a~32f Nuclear fuel assembly 34 Plots 36 Head plate with opening 40 First Brake Device 40a~40e Cylindrical block 50a to 50f Second braking device, braking block, cylindrical block 54 Cylindrical casing 54a, 54b Half casing 58a Disc Plate 58b Disc-shaped plate, closing plate 100 packages

Claims

1. A package (100) comprising a radioactive content (12) and a packaging material (1) for transporting and / or storing said content (12), said packaging material comprising sides (2) extending around a longitudinal central axis (8) of said packaging material, and a bottom (4) and a cover (6) respectively arranged at the axial ends of said packaging side parts (2) and forming two axial blocking members which together with said packaging side parts (2) define a containment chamber (10) in which said radioactive content (12) is contained, said packaging material also comprising a sealing material (10) for sealing said containment chamber (10), the radioactive content (12) is housed in a storage device (30) and includes an internal shock absorbing system (22) arranged axially between the radioactive content (12) and one of the two axial blocking members, the so-called associated axial blocking member, the radioactive content (12) including a storage device (30) as well as one or more radioactive elements (32a-32f), the storage device defining one or more axial compartments (34) axially opening in the direction of the associated axial blocking member, in each of which at least one of the radioactive elements (32a-32f) is arranged, said internal shock absorbing system (22) comprising a first damping device (40) by plastic deformation for damping said storage device (30) and a second damping device (50a-50f) by plastic deformation associated with a radioactive mass formed by one or more radioactive elements (32a-32f); said first and second braking devices (40, 50a-50f) are arranged to operate independently of each other in the event of an axial drop of said package; The first braking device (40) is configured to have a first parameter: σ corresponding to the crushing stress of this first damping device 1 and, S corresponding to the working surface of the first braking device intended to be impacted axially by the storage device (30) in the event of an axial fall of the package. 1 and, M corresponding to the mass of the storage device (30) intended to be braked by the first brake device (40). 1 and, γ corresponds to a first value expressing the deceleration of the storage device (30) in the event of an axial drop of the package which leads to plastically crushing the first braking device (40). 1 wherein the first deceleration representation value γ 1 is expressed by the following formula: γ 1 = (σ 1 *S 1 ) / M 1 γ 1 and is associated with The second braking device (50a-50f) is adapted to determine a second parameter: σ corresponding to the crushing stress of this second damping device 2 and, S corresponding to the working surface of the second damping device intended to be impacted axially by its associated radioactive assembly (32a-32f) in the event of an axial fall of the package. 2 and, M corresponding to the mass of the radioactive assemblies (32a to 32f) intended to be braked by the second brake devices (50a to 50f). 2 and, γ corresponds to a second value expressing the deceleration of the associated radioactive aggregate in the event of an axial drop of the package which leads to the radioactive aggregate (32a-32f) plastically crushing the second braking device (50a-50f); 2 The second deceleration representation value γ 2 is expressed by the following formula: γ 2 = (σ 2 *S 2 ) / M 2 γ 2 and is associated with The first parameter and the second parameter are the second deceleration representation value γ 2 is the first deceleration representation value γ 1 The package (100) is characterized in that it is different from the above.

2. ratio | γ 2 -γ 1 | / min(γ 2 , γ 1 2. The package of claim 1, wherein the ratio of the number of electrodes to the number of electrodes is greater than 1.

1.

3. the internal shock absorbing system (22) comprises one or more other secondary damping devices (50a-50f) by plastic deformation, each associated with a separate radioactive assembly formed by one or more other radioactive elements (32a-32f); The first and second parameters of the first and second braking devices (40, 50a-50f) are determined by a second deceleration representative value γ associated with each of at least some of the second braking devices (50a-50f), preferably with each of all of these second braking devices. 2 the first deceleration representative value γ associated with the first braking device (40); 1 3. The package according to claim 1 or 2, characterized in that it is different from the above.

4. 4. A package according to any one of claims 1 to 3, characterized in that the radioactive mass associated with the or with each secondary braking device (50a to 50f) is formed by one single radioactive element (32a to 32f).

5. The package according to any one of claims 1 to 4, characterized in that each radioactive element (32a-32f) is a nuclear fuel assembly, preferably a fresh fuel assembly, even more preferably of the MOX type, or a vitrification waste container / case, or a shell and nozzle container / case, or a case for transporting powder.

6. A package according to any one of claims 1 to 5, characterised in that the or each second braking device (50a-50f) is formed of one single block of braking material, preferably made of metal foam, wood, honeycomb or using a metal tubular structure.

7. A package according to any one of claims 1 to 6, characterized in that the first braking device (40) is formed of several blocks of braking material (40a-40e) spaced apart from one another, preferably made of foam, wood, honeycomb or using a metal tubular structure.

8. The crushing stress σ of the or each second braking device (50a-50f) 2 is the crushing stress σ of the first braking device (40) 1 8. The package according to claim 1 , characterized in that it is different from

9. 9. The package according to any one of claims 1 to 8, characterized in that the first braking device (40) and the or each second braking device (50a-50f) all have the same or substantially the same axial thickness.

10. 10. The package according to any one of claims 1 to 9, characterized in that the first braking device (40) and the or each second braking device (50a-50f) are arranged in the same transverse plane of the package.

11. A package according to any one of the preceding claims, characterised in that the first braking device (40) and the or each second braking device (50a-50f) are arranged in the same casing (54).

12. 12. The package according to any one of claims 1 to 11, characterized in that the storage device (30) comprises an apertured head plate (36) and the internal shock absorbing system (22) is preferably fixed to the apertured head plate.

13. 13. A package according to any one of the preceding claims, characterised in that the associated axial blocking member is the cover (6) of the packaging, preferably removably attached to a side part of the packaging.

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