Patent Number: 054209005
Section: claims

1. A nuclear reactor having a core, upper internal equipment and a plurality of clusters of control rods vertically movable between a lower position in which they are in the core and an upper position in which they are out of the core, said upper internal equipment comprising: a bottom plate formed with openings allowing coolant to leave the core upwardly;  a top plate above said bottom plate;  a plurality of vertical spacer columns interconnecting the plates; and  a plurality of cluster guides, each for receiving one of said control clusters, at least some of said cluster guides each having:  a one-piece cartridge suitable for insertion in a respective one of said spacer columns, comprising a top length that projects above the top plate and a bottom length that extends between the bottom plate and the top plate, that is located within the respective spacer column, and that includes a support base bearing against a frustoconical seat of said bottom plate, said bottom length and top length constituting a framework which comprises, in addition to said support base, vertical longitudinal members and cross-plates connected to the vertical members and providing discontinuous guidance of the control rods of one of said clusters in the bottom length and top length;  an external casing slidable over and receiving the top length, secured to the top plate at a lower end thereof and having a reception plate at an upper end thereof; and  resilient means located between said top length and said reception plate for exerting a force that urges the support base down against the seat. 2. Internal equipment according to claim 1, wherein said cartridge further includes split sleeves and tubes for providing continuous guidance of the control rods in a lowest portion of the bottom length. 3. Internal equipment according to claim 1, wherein said reception plate slidably receives centering means projecting into a central bore of a highest plate of said cartridge and having an abutting connection with said highest plate, and wherein said resilient means comprise a spring retained in said reception plate and exerting said force on said centering means. 4. Internal equipment according to claim 3, wherein said centering means is a bush having a flange bearing against a spring constituting said resilient means and held captive by a nut screwed into said reception plate. 5. Internal equipment according to claim 4, wherein said centering means bears on the highest plate via a nut which is adjustably screwed on said centering means. 6. Internal equipment according to claim 1, wherein said top length has a highest end plate and said resilient means comprises a plurality of identical spring sets uniformly distributed around an axis of the cluster guide accommodated in the highest plate. 7. Internal equipment according to claim 6, wherein each said spring set comprises a spring contained in a chamber formed in the highest plate and compressed between an end wall of the chamber and a plunger for transmitting thrust from said reception plate. 8. Internal equipment according to claim 6, wherein said spring is constituted by a stack of Belleville washers. 9. Internal equipment according to claim 6, wherein each said spring is constituted by a helical spring.