Patent Number: 
Section: claims

1. A storage device for temporarily storing and/or transporting PWR type nuclear fuel assemblies, said device being intended to be housed in a cavity of a package and including a plurality of adjacent housings each intended to receive a nuclear fuel assembly, the housings being delimited by separating partitions at least one of which delimits on either side of the same first and second housings,wherein said at least one separating partition includes:two first walls each partly delimiting, respectively with its external surface, said first and second housings, both first walls being made of a first material of aluminium alloy free of neutron absorbing elements, both first walls delimiting a first inter-wall space therebetween;two second walls arranged in the first inter-wall space and made of a second material comprising neutron absorbing elements and distinct from the first material, each second wall having an external surface facing one of both first walls, as well as an internal surface arranged such that both internal surfaces of both second walls are facing each other and delimit a second inter-wall space therebetween, the distance between the internal and external surfaces of each second wall defining a thickness (e2), whereas a distance (E) is defined between the external surface of each second wall and a median partition plane parallel to the first and second walls,said device being also characterised in that the thickness (e2) and the distance (E) meet the following condition:1≤e2/E≤0.43. 2. The storage device according to claim 1, wherein the thickness (e2) and the distance (E) meet the following condition:0.15≤e2/E≤0.32. 3. The storage device according to claim 1, wherein the distance (E) is between 20 and 30 mm. 4. The storage device according to claim 1, wherein the second material comprises neutron absorbing elements chosen from boron and cadmium. 5. The storage device according to claim 1, wherein each second wall is pressed against the first associated wall, taking the form of a coating deposited onto the internal surface of the first wall. 6. The storage device according to claim 1, wherein a clearance (J) is present between each second wall and the first associated wall, the clearance (J) being between 1 and 5 mm. 7. The storage device according to claim 1, wherein it has a number of housings between four and twenty-four housings, each housing being intended to receive a nuclear fuel assembly. 8. The storage device according to claim 1, wherein at least one of the housings has a quadrilateral shaped cross-section. 9. The storage device according to claim 1, wherein at least some of said partitions are made using notched structural assemblies, the structural assemblies being interlaced and stacked along a stacking direction parallel to the axes of the housings. 10. The storage device according to claim 1, wherein at least some of said partitions are partly made using tubular elements each internally defining one of said housings, the walls of these tubular elements making up said first walls of the partitions. 11. The storage device according to claim 10, wherein the second walls are externally secured to the tubular elements. 12. A package for temporarily storing and/or transporting PWR type nuclear fuel assemblies, the package comprising a cavity in which a storage device according to claim 1 is housed. 13. A pack comprising a package according to claim 12 as well as fuel assemblies arranged in the housings of the storage device of this package.