ASSEMBLY FOR TRANSPORTING URANIUM HEXAFLUORIDE, COMPRISING SHOCK ABSORBER CAPS

Abstract

An assembly for transporting uranium hexafluoride, includes: a sealed inner container, defining a first containment shell intended to be loaded with uranium hexafluoride and having a general cylindrical shape of circular cross-section, the first containment shell being delimited by a lateral wall extending about a longitudinal central axis of the inner container, as well as by two opposite axial end walls crossed by the longitudinal central axis, at least one of the two opposite axial end walls of the sealed inner container being equipped with a uranium hexafluoride filling valve; a sealed outer container delimiting a second containment shell in which the inner container is housed in an extractable manner; and two shock absorber caps removably fastened on respectively two opposite axial ends of the outer container.

Claims

1. An assembly for transporting uranium hexafluoride, comprising: a sealed inner container, defining a first containment shell intended to be loaded with uranium hexafluoride, the sealed inner container having a general cylindrical shape of circular cross-section, the first containment shell being delimited by a lateral wall extending about a longitudinal central axis of the inner container, as well as by two opposite axial end walls crossed by the longitudinal central axis, at least one of the two opposite axial end walls of the sealed inner container being equipped with a uranium hexafluoride filling valve as well as with a protective annular axial extension of the uranium hexafluoride filling valve, the extension extending axially beyond the filling valve; a sealed outer container delimiting a second containment shell wherein the sealed inner container is housed in an extractable manner; and two shock absorber caps removably fastened on respectively two opposite axial ends of the sealed outer container.

2. The assembly according to claim 1, wherein the sealed outer container includes a case as well as a cover removably fastened onto the case, the latter delimiting an axial introduction opening of the sealed inner container in the second containment shell.

3. The assembly according to claim 2, wherein the inner container is arranged in the outer container such that the filling valve of the inner container faces the cover of the outer container.

4. The assembly according to claim 1, wherein a layer of neutron insulating material, preferably made of a material comprising boron and/or which is hydrogenated, is provided: on an outer lateral surface of the sealed outer container; and/or on an inner lateral surface of the sealed outer container; and/or when the sealed outer container has a lateral double wall, between the two walls of the lateral double wall.

5. The assembly according to claim 1, wherein the lateral wall of the sealed outer container is made of steel.

6. The assembly according to claim 1, wherein the lateral walls of the sealed outer container and the sealed inner container are made of steel and have a cumulative thickness greater than or equal to 13 mm.

7. The assembly according to claim 1, wherein one of the two shock absorber caps includes a shock absorber element axially facing the uranium hexafluoride filling valve provided on the sealed inner container.

8. The assembly according to claim 1, wherein each shock absorber cap includes a recess wherein the associated axial end of the sealed outer container is housed.

9. The assembly according to claim 1, wherein it has a length less than or equal to the length of a 20-foot ISO container along the direction of the longitudinal central axis of the sealed inner container, and preferably a length less than or equal to the length of a 15-foot ISO container.

10. The assembly according to claim 1, wherein the sealed inner container is designed to meet the standard ISO 7195 relating to the transport of uranium hexafluoride.

11. A system comprising a vehicle for transporting uranium hexafluoride, as well as at least one assembly according to claim 1, mounted on a loading platform of this vehicle, which is preferably a road, rail or sea transport vehicle.

12. The system according to claim 11, wherein each assembly is oriented so that the longitudinal central axis of its sealed inner container is arranged parallel to a direction of travel of the transport vehicle.

13. The system according to claim 11, wherein several assemblies are mounted on the loading platform of the vehicle, by being stacked on top of each other, and/or arranged one behind another according to the direction of travel of the transport vehicle, and/or arranged side by side.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] This description will be given with reference to the appended drawings, wherein;

[0035] FIG. 1 represents a perspective view of a system according to the invention, comprising a vehicle for transporting uranium hexafluoride, as well as two assemblies for transporting uranium hexafluoride mounted on the loading platform of the vehicle, one of the two assemblies being represented partially transparent for more clarity in this figure;

[0036] FIG. 2 is an exploded perspective view of one of the transport assemblies shown in FIG. 1, according to a preferred embodiment of the invention;

[0037] FIG. 3 is a cross-sectional view of the transport assembly, taken along the plane P1 of FIG. 2;

[0038] FIG. 4 is a side view of the sealed inner container housed inside the assembly shown in FIGS. 2 and 3;

[0039] FIG. 5 is a front view of the container shown in the previous figure, along the axial direction of the inner container, showing the axial end wall equipped with an uranium hexafluoride filling valve;

[0040] FIG. 6 is an enlarged partial view of that of FIG. 4, showing more specifically the filling valve of the inner container;

[0041] FIG. 7 is an axial cross-sectional view of the transport assembly, taken along the plane P2 of FIG. 2; and

[0042] FIG. 8 is an enlarged partial axial cross-sectional view of the transport assembly, presented according to an alternative of the preferred embodiment shown the preceding figures.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0043] Referring firstly to FIG. 1, a system 100 is represented comprising a vehicle for transporting uranium hexafluoride, this vehicle being herein a road transport vehicle only the trailer portion 202 of which has been represented. Alternatively, it may consist of a rail or sea transport vehicle, without departing from the scope of the invention. The system 100 is completed by one or more assembly(ies) 1 specific to the present invention, removably mounted on the platform 205 of the trailer 202. More specifically, each assembly 1 has a cylindrical lateral body rigidly connected to a cradle 3, itself removably mounted on a frame 5 fastened to the platform 205. This fastening of the frame 5 to the platform 205 is also preferably removable.

[0044] According to an alternative not shown, a flatbed container, also known as flatrack or sea container, may be used. In this case, the flatbed container has a flatbed whereon the frames 5 supporting the assemblies 1 are mounted, with this flatbed being itself removably mounted on the platform 205 of the trailer 202.

[0045] Each assembly 1 incorporates a single sealed inner container 2, one of which is only very partially visible in FIG. 1. This sealed inner container 2 is intended to be loaded with uranium hexafluoride, preferably enriched to a value greater than 5% by mass. In this instance, two transport assemblies 1 are arranged one behind another according to the direction of travel 206 of the vehicle, each being fastened and bearing on the platform 205. Alternatively or simultaneously, these transport assemblies 1 can be stacked on top of each other, or, also alternatively or simultaneously, arranged side by side on the same platform.

[0046] The number of transport assemblies 1 likely to be loaded on the platform depends in particular on the length of the latter, as well as on the length of the assemblies 1. Depending on the direction of travel 206 of the vehicle 200, the platform 205 has a length L1 equal or substantially equal to the length of a 40-foot ISO platform. This makes it possible to implement the invention with standard means, readily available on the market.

[0047] Moreover, each transport assembly 1 is oriented on the platform 205 so that its longest length L2 is in the sense of the direction of travel 206. Preferably, this length L2 is less than or equal to the internal length of a 20-foot ISO flatbed container (namely a length of about 5.7 metres), and even more preferably less than or equal to the internal length of a 15-foot ISO flatbed container (namely a length of about 4.6 metres). In this manner, the platform 205 can easily transport two assemblies 1 one behind another, or two stacks of assemblies 1 arranged one behind another.

[0048] The transport assemblies 1, which will be detailed hereinafter, are also arranged such that the longitudinal central axis 6 of the sealed inner container 2 is oriented parallel to the direction of travel 206.

[0049] Hereinafter, one of the assemblies 1 for transporting uranium hexafluoride enriched to a value greater than 5%, according to a preferred embodiment of the invention, will be described. In this respect, it is indicated that all of the assemblies 1 intended to be mounted on the platform 205 have a design identical or similar to that detailed hereinafter.

[0050] With reference to FIGS. 1 to 7, the assembly 1 includes a sealed outer container 8, forming the outer enclosure of the assembly, and delimiting a cavity 15. The assembly 1 also includes a single sealed inner container 2, internally delimiting a space 14 for loading uranium hexafluoride, this space 14 forming a first containment shell. Furthermore, the cavity 15 internally delimited by the outer container 8 forms a second containment shell 15, wherein the single sealed inner container 2 is housed in an extractable manner.

[0051] Also, two shock absorber caps 19 are removably mounted, respectively on the two opposite axial ends of the sealed outer container 8.

[0052] The sealed inner container 2 has a general cylindrical shape with a circular cross-section, centred on the longitudinal central axis 6 of the considered inner container 2. The inner container 2 is disposed in such a way that its axis 6 is parallel with the platform to which the assembly 1 is intended to be mounted for its transport. More specifically with reference to FIGS. 4 to 6, the sealed inner container 2, intended for loading enriched uranium hexafluoride, preferably corresponds to a standardised container known as 30B cylinder. Alternatively, it could be any one of the 5B, 8A, 12B, 30C cylinders, meeting the same standard ISO 7195.

[0053] It includes the loading space 14 forming the first containment shell, delimited by a cylindrical lateral wall 16 of circular cross-section, extending about the axis 6. This lateral wall 16 is completed by two opposite axial end walls 18, each with an outwardly cambered shape and crossed at its centre by the longitudinal central axis 6. One amongst the two axial end walls 18 is equipped with an uranium hexafluoride filling valve 20, best visible in FIG. 6. This valve 20 projects axially from the axial end wall 18, outside the containment shell 14. It is protected by a protective annular axial extension 22, extending axially beyond the filling valve 20. This extension 22 has a cylindrical shape with a section identical or similar to that of the lateral wall 16 proximate to its junction with the latter, then terminates in an end 24 slightly curved inwards, in the direction of the axis 6. An identical or similar extension 22 may be provided on the other axial end wall 18, for example to protect a drain plug 26.

[0054] The sealed outer container 8 takes here the form of a canister, i.e. a cylindrical case 56 closed by a cover 58 fastened reversibly to an axial end of this case. At this axial end of the case 56, i.e. that opposite the bottom of said case, the latter delimits an axial introduction opening 60 of the sealed inner container 2, in the second containment shell 15 delimited by the case centred on the axis 6, and the cover 58 crossed orthogonally by said axis.

[0055] Here, a sealing device (not shown) is arranged at the interface between the case 56 and the cover 58, so as to obtain the second containment shell 15. This sealing device can be conventional, for example of the same type as that usually encountered on a cover of a standard container for transporting and/or storing radioactive materials. For example, at least one seal is provided, for example a concentric O-ring, disposed on the cover, between this cover and the end of the lateral body of the case 56. Screws for fastening the cover onto the lateral body of the case compress the seal between the cover and the lateral body.

[0056] The opening 60 is inscribed in an orthogonal or substantially orthogonal plane to the axis 6 of the single inner container 2 received in the case 56. With such an axial opening 60, the inner container 2 is intended to be introduced into the case 56 while being moved in a direction of movement parallel with its axis 6.

[0057] The interior of the second containment shell 15 and the outer surface of the inner container 2 have a complementarity of shape, with for example a small radial gap provided between the two, with respect to the axis 6.

[0058] The lateral wall and the bottom of the case 56, as well as the cover 58, are preferably made of steel, like the lateral wall 16 and the axial end walls 18 of the inner container 2.

[0059] Furthermore, the cumulative thickness of the two lateral steel walls of the two containers 2, 8 is preferably greater than or equal to 13 mm. This makes it possible not only to give the assembly 1 a satisfactory mechanical strength, but this steel thickness also makes it possible, surprisingly, to meet the subcriticality criterion for the sought application, namely transporting enriched UF6.

[0060] The subcriticality criterion is also met thanks to the preferential presence of one or more layers of neutron insulating material, made for example from a material comprising boron and/or which is hydrogenated. By way of indication, it is noted that this neutron insulating material can be a highly hydrogenated and boron-free material, such as silicone. Alternatively, this material can include boron and not hydrogen, such as an AL-B4C type aluminium-boron alloy. It can also include hydrogen and boron, such as borated high-density polyethylene (HDPE).

[0061] Such a layer can for example be provided on an outer lateral surface of the sealed outer container 8, and/or on an inner lateral surface thereof.

[0062] In the alternative embodiment shown in FIG. 8, the case 56 of the sealed outer container 8 has a lateral double wall, formed by two, preferably concentric, lateral walls 8, 8, defining between them an annular space at least partially filled by such a layer of neutron insulating material 40. In this alternative, the lateral steel wall 16 of the inner container 2 has a thickness E1, the lateral wall 8 of the outer container 8 has a thickness E2, whereas its lateral wall 8 has a thickness E2. In this context, the cumulative thicknesses E1, E2, E2 result in a value greater than or equal to 13 cm, so as to impart satisfactory properties for the assembly 1, in terms of mechanical strength and subcriticality.

[0063] Regardless of the embodiment envisaged, each of the layers of neutron insulating material cited above can be provided alone on the assembly 1, or in combination with one or more others of these layers.

[0064] With reference more specifically to FIG. 7, it is noted that the inner container 2 is arranged in the containment shell 15 of the outer container 8, such that the filling valve 20 is axially facing the cover 58 of the outer container 8. Furthermore, this cover 58 is protected by the presence of the shock absorber cap 19 mounted on the corresponding axial end of the outer container 8. For this purpose, the cap 19 has a recess 21 wherein the cover 58, and the axial end of the case 56 bearing this cover, are housed.

[0065] The axial recess 21, improving the mechanical strength of the cap 19 on the outer container 8, is defined by a metal outer wall 23 of the cap, preferably made of steel. This outer wall 23 contains one or more shock absorber elements 25, of which one or more are arranged axially facing the uranium hexafluoride filling valve 20 provided on the sealed inner container 2. This shock absorber element 25 thus makes it possible to properly protect the valve 20, corresponding to a particularly sensitive zone of the sealed inner container 2 in the event of a fall.

[0066] An identical or similar arrangement is provided at the opposite axial end of the outer container 8, with the other cap 19 to protect the drain plug 26 of the inner container 2. With this assembly 1 in the form of two nested enclosures supplemented by the shock absorber caps 19, and of which the two inner enclosures 2, 8 define a double containment shell, the invention makes it possible to meet the subcriticality criterion even for transporting highly enriched uranium hexafluoride, i.e. having an enrichment greater than 5% by mass. Furthermore, this design makes it possible to use existing 30B cylinder type or equivalent abovementioned conventional/standardised inner containers 2, thus retaining their uranium hexafluoride loading capacities. Also, this design advantageously offers facilities for heating the sealed inner container 2. In operation, and more specifically for the purposes of uranium hexafluoride filling operations, the inner container 2 can be readily extracted from the outer container 8, in order to be able to be subsequently heated more readily, for example in a furnace provided for this purpose, without being subject to thermal inertia problems. The heating time and/or the heating power can advantageously be reduced.

[0067] It is noted that the extractible feature of the inner container 2 with respect to the sealed outer container 8, is understood as the ability to open the second containment shell 15 non-destructively, i.e. reversibly so as to be able subsequently to reclose it, then reopen it, etc. This functionality is preferably obtained using reversible fastening means between different parts of the outer container 8, such as the bolts cited above.

[0068] Of course, various modifications can be made by a person skilled in the art to the invention that has just been described, only as non-limiting examples, and within the limit of the scope defined by the appended claims.