Patent Number: 
Section: claims

1. A package (1) for the transport and/or storage of radioactive materials, the package comprising a package side body (10) extending about a central longitudinal axis (2) and partly delimiting a housing (12) for the radioactive materials, the package also comprising, being arranged around the package side body, an external radiation protection shell (14) made of a plurality of unitary annular structures (16), stacked on each other along the central longitudinal axis (2) and arranged around the package side body (10),each unitary annular structure (16) comprises:an outer annular wall (24);an inner annular wall (26);a radial heat conduction wall (22) having an external end integral with the outer annular wall (24), as well as an internal end in contact with the package side body (10) and integral with the inner annular wall (26) itself in contact with the package side body (10);and in that two unitary annular structures (16) directly consecutive in the stack at least partly delimit an annular cavity (30) housing at least one radiation protection element (32), said cavity being radially closed outwards by the outer annular wall (24) of one or both of the two directly consecutive unitary annular structures, radially closed inwards by the inner annular wall (26) of one or both of the two directly consecutive unitary annular structures, and axially closed on either side by the radial heat conduction wall (22) of one and the other of said two directly consecutive unitary annular structures (16) respectively. 2. The package according to claim 1, wherein each unitary annular structure (16) is as a single piece. 3. The package according to claim 1, characterised in wherein said radiation protection element (32) is a neutron protection element, and in that each unitary annular structure (16) meets the following formula:0.02<n.E1/H<0.3with:n″ corresponding to the total number of stacked unitary annular structures (16);E1″ corresponding to the thickness of the radial heat conduction wall (22); andH″ corresponding to the height of the external shell (14). 4. The package according to claim 3, characterised in that it meets the following formula:n/H>2with “H” expressed in metres. 5. The package according to claim 3, wherein each unitary annular structure (16) meets the following formula:L/E1<10with “L” corresponding to the radial spacing between the inner and outer annular walls (26, 24). 6. The package according to claim 1, wherein each unitary annular structure (16) has a generally U-shaped half transverse cross-section, with the U-base formed by the radial heat conduction wall (22), and the two U-branches formed by the external (24) and internal (26) annular walls respectively, and in that U-interior forms the annular cavity (30) housing said at least one radiation protection element (32). 7. The package according to claim 6, wherein for each unitary annular structure (16), the two free ends of the two annular outer (24) and inner (26) walls lie in the same transverse plane of the package. 8. The package according to claim 1, wherein the radial heat conduction wall (22) of each unitary annular structure (16) has, in a half transverse cross-section, a straight segment shape, preferably oriented orthogonally to the central longitudinal axis (2). 9. The package according to claim 1, wherein the radial heat conduction wall (22) of each unitary annular structure has, in half transverse cross-section, at least one axial level change (22c) between a wall radially outer portion (22a) and a wall radially inner portion (22b). 10. The package according to any of the preceding claim 1, wherein in each annular cavity (30) the radiation protection element(s) (32) forms a protective ring (34) extending over 360°. 11. The package according to claim 1, wherein in each annular cavity (30) each radiation protection element (32) is an element cast in the cavity, or a prefabricated element arranged in that cavity. 12. The package according to claim 1, that wherein at least several of said unitary annular structures (16) are identical. 13. The package according to claim 1, wherein each unitary annular structure (16) has a half transverse cross-section with a constant shape. 14. The package according to claim 1, wherein the number of unitary annular structures (16) is between 10 and 50, and in that the height (H) of the external radiation protection shell (14) formed by the stack of these structures (16) is between 1 and 4 m. 15. A method for manufacturing a package (1) for the transport and/or storage of radioactive materials according to claim 1, the method comprising repeating the following successive steps of:installing one of the unitary annular structures (16) in the stack around the side body (10);installing each radiation protection element (32) in the annular cavity (30) partly defined by the unitary annular structure (22) installed in the preceding step. 16. A method for manufacturing a package (1) for the transport and/or storage of radioactive materials according to claim 1, the method comprising repeating the following successive steps of:installing each radiation protection element (32) in the annular cavity (30) partly defined by one of the unitary annular structures (16);installing, in the stack around the side body (10), the unitary annular structure (16) mentioned in the preceding step, equipped with each radiation protection element (32).