Patent Number: 052271269
Section: claims

1. Internal structure of a fast neutron nuclear reactor comprising a main vessel, a core of said reactor and said internal structure being contained in said main vessel and immersed in a liquid metal for cooling said core, said internal structure comprising an internal vessel defining a zone of said main vessel for receiving hot liquid metal leaving said core and a zone for receiving cooled liquid metal, said internal vessel comprising a step shaped area having a substantially toroidal shape in the lower part thereof, a support element, termed a bed, for assemblies of said core and for the supply and distribution of said cooling liquid metal in said core, and a support element, termed plating, for supporting said bed and resting on a bottom of said main vessel, said step shaped area of said internal vessel having a lower portion directly fixed by welding to an upper part of said bed, means connected to said bed for supplying cooling liquid metal in a zone located at the periphery of said bed and outside said internal vessel and outside said plating, slidable bearing means interposed between said bed and said plating, said bed resting on said plating through the medium of said slidable bearing means, one of said slidable bearing means being located at the periphery of said bed and ensuring a sealing of said cooling liquid metal between said bed and said plating. 2. Internal structure according to claim 1, wherein said step shaped area of said internal vessel is constituted by a single wall. 3. Internal structure according to claim 1, comprising absorbent assemblies constituting a lateral neutronic protection of said reactor and fixed directly on said bed at the periphery of said core. 4. Internal structure according to claim 1, wherein said slidable bearing means comprise an annular bearing flange connected to a peripheral portion of said bed and a plurality of spherical bearing devices interposed between said bed and said plating. 5. Internal structure according to claim 1, further comprising a flange connected to said plating, and a central pivot connected to said bed and engaged in said flange for ensuring a transverse maintenance of said bed relative to said plating. 6. Internal structure according to claim 5, comprising a locking key engaged in an upper sole plate of said plating for locking said bed against rotation relative to said plating. 7. Internal structure according to claim 1, wherein said bed is constructed in the form of a cylindrical box structure which comprises an outer shell, a circular lower sole and a circular upper sole which are fixed by the periphery therof to said outer shell. 8. Internal structure according to claim 7, wherein said outer shell of said bed comprises an upper annular portion which projects from said upper sole, and said step shaped area of said inner vessel has an end which is welded onto said upper annular portion. 9. Internal structure according to claim 7, wherein said outer shell of said bed comprises an annular lower portion which projects below said lower sole, constitutes said peripheral slidable bearing means and rests on said plating through the medium of an adjusting packing piece. 10. Internal structure according to claim 9, comprising a hard covering provided on a lower bearing surface of said lower annular portion of said outer shell and on a respective bearing surface of said packing piece. 11. Internal structure according to claim 7, wherein said means for supplying cooling liquid metal to said bed comprise at least one piping connected to a respective nozzle welded to said outer shell around a throughway opening in said outer shell.