Patent Number: 
Section: claims

1. A supporting device (3) for supporting a radioactive material transporting/storing package (1) in a horizontal position, the supporting device comprising a structural base (10) as well as supporting means (12) for supporting the package which are carried by said structural base from which they upwardly project,characterised in that it further comprises, being located at least partly above the structural base (10), a cooling air guide shroud (30) of the package by natural convection, said shroud (30) defining an upwardly open cavity (32) in which a part of the package is intended to be housed when this package (1) is supported in a horizontal position on the device, said shroud (30) comprising, in a bottom part thereof, at least one aperture (34) for taking in cooling air in said cavity (32). 2. The supporting device according to claim 1, characterised in that said supporting means (12) comprise first supporting means intended to receive package head part (2a), as well as second supporting means intended to receive a package bottom part (2b), said first and second supporting means being axially spaced apart by an axial spacing distance (Dea), and in that the air guide shroud (30) has preferably an axial length (The) substantially identical to the axial spacing distance (Dea). 3. The supporting device according to claim 2, characterised in that said shroud (30) includes a first axial end (36a) attached to said first supporting means, as well as a second axial end (36b) attached to said second supporting means. 4. The supporting device according to claim 2, characterised in that said shroud (30) is attached to said structural base (10). 5. The supporting device according to claim 2, characterised in that the axial spacing distance (Dea) is between 1.5 and 4 m. 6. The supporting device according to claim 1, characterised in that said shroud (30) is generally of a semi-cylindrical shape, pierced by said at least one cooling air intake aperture (34). 7. The supporting device according to claim 6, characterised in that a transverse cross-section of said shroud (30) is generally of a semi-circular shape. 8. The supporting device according to claim 6, characterised in that a transverse cross-section of said shroud (30) is generally of a semi-octagonal shape, the side (54) closest to the structural base (10) of which is arranged in parallel with the horizontal direction. 9. The supporting device according to claim 8, characterised in that said side (54) closest to the structural base (10) is pierced by said at least one cooling air intake aperture (34). 10. The supporting device according to claim 1, characterised in that said at least one cooling air intake aperture (34) is arranged at a bottom point of the shroud (30). 11. The supporting device according to claim 1, characterised in that said at least one cooling air intake aperture (34) extends on the entire axial length (La) of the shroud. 12. The supporting device according to claim 1, characterised in that said at least one cooling air intake aperture (34) has a transverse width (Ltr) between 100 and 500 mm, and is preferentially in the order of 300 mm. 13. The supporting device according to claim 12 combined, characterised in that said under-shroud height (Hsc) is higher than or equal to half the transverse width (Ltr) of the cooling air intake aperture (34). 14. The supporting device according to claim 1, characterised in that a free space (38) is provided under said shroud (30), said free space having, at a bottom point of the shroud (30), an under-shroud height (Hsc) between 50 and 400 mm, and preferentially in the order of 200 mm. 15. The supporting device according to claim 1, characterised in that it forms a package transporting/storing chassis (3), possibly intended to be manipulated with the package (1) when the latter is supported by the device. 16. The supporting device according to claim 1, characterised in that the structural base (10) forms all or part of a platform of a railroad car belonging to a railway transport system (82), or forms all or part of a platform of a trailer belonging to a road transport system. 17. An assembly (100) comprising a radioactive material transporting/storing package, as well as a supporting device (3) according to claim 1, said package (1) being supported in a horizontal position on said device (3), with a part of a side body (2) of the package which is housed in said cavity (38) defined by the cooling air guide shroud (30). 18. The assembly according to claim 17, characterised in that said package (1) includes manipulation trunnions (22), and in that said supporting means (12) include housings (20) each receiving one of said trunnions (22). 19. The assembly according to claim 17, characterised in that said supporting means (12) include at least two cradles (18a′, 18b′) on which the side body (2) of the package (1) rests. 20. The assembly according to claim 17, characterised in that the side body (2) of the package includes an external diameter between 1 and 2.5 m. 21. The assembly according to claim 17, characterised in that said cooling air guide shroud (30) have two opposite transverse ends (42a, 42b), each located on or in the proximity of a median axial horizontal plane (44) of the package. 22. The assembly according to claim 17, characterised in that the internal surface of the shroud (30) and the external surface of the side body (2) of the package define therebetween a cooling air circulation channel (50), with an average thickness between 50 and 200 mm. 23. The assembly according to claim 17, characterised in that the internal surface of the shroud (30) and the external surface of the side body (2) of the package (1) define therebetween a cooling air circulation channel (50) with a substantially constant thickness. 24. A road or railway radioactive material transport system (74, 82), comprising a supporting device (3) according to claim 1, said structural base (10) of the supporting device (3) being fastened to a platform (70) of the transport system, or forming all or part of this platform.