Patent Number: 054209005
Section: summary

BACKGROUND OF THE INVENTION The present invention relates to upper internal equipments for a nuclear reactor, and it is particularly applicable to reactors that are cooled and moderated by pressurized water. More particularly, it relates to internal equipments located above the core of a nuclear reactor, the equipment comprising a bottom plate formed with openings allowing coolant to leave the core, a top plate, spacer columns interconnecting the plates, and cluster guides for control clusters that are vertically displaceable between a lower position in which they are inserted in the core and an upper position in which they are out of the core, at least some of said guides each having an upper length that projects above the top plate and a bottom length that extends between the plates and that is within a respective spacer column. More particularly, the invention relates to equipments of this kind in which the bottom length includes a support base for abutment on a frustoconical seat secured to the bottom plate and is subjected to the action of resilient means exerting a force that urges the base against the seat, as described in U.S. Pat. No. 5,183,628. SUMMARY OF THE INVENTION It is an object of the present invention to provide equipments enabling cluster guides placed in columns to be installed and replaced simply, and also enabling a structure to be preassembled in a factory and subsequently connected directly to the top plate. To this end, there are provided equipments of the kind defined above in which the two lengths of each guide constitute a one-piece cartridge suitable for insertion in a corresponding column, and in which the guide further includes a casing for receiving the upper length, which casing is fixed to the top plate constituting an abutment for the resilient means. Typically, the two lengths each comprise a plurality of longitudinal members (e.g., four) that are regularly spaced apart angularly and that interconnect a higher plate subjected to the action of the resilient means and cross guide plates for cluster rods that are insertable in the guide, together with split sleeves and tubs for continuous guidance of the rods in the lowest portion of the bottom length. The longitudinal members extend to the top of the cartridge. They may either be interrupted from the cross plate of the bottom length at which the split sleeves and tubes for continuous guidance begin, or they may extend up to a bottom cross plate (or even up to the base). The invention will be better understood from the following description of particular embodiments given as by way of example. The description refers to the accompanying drawings.