Patent Number: 
Section: claims

1. A nuclear reactor comprising:a vessel;a core provided in the vessel;at least one plate heat exchanger provided in the vessel;at least one secondary fluid supply duct for supplying a secondary fluid to the heat exchanger and a discharge secondary fluid duct for discharging the secondary fluid from the heat exchanger, the discharge secondary fluid duct extending through the vessel; andan attachment for attaching the heat exchanger to an area of the vessel through which the discharge secondary fluid duct extends,wherein the secondary fluid supply duct supplying the heat exchanger with secondary fluid includes an upstream crossing extending through the vessel, and a plurality of flexible ducts connecting the upstream crossing to the heat exchanger,wherein the heat exchanger includes at least one upstream secondary collector supplying the heat exchanger with secondary fluid, the upstream secondary collector and the upstream crossing being connected to each other by the flexible ducts. 2. The nuclear reactor as recited in claim 1 wherein the attachment bears at least 70% of the weight of the exchanger. 3. The nuclear reactor as recited in claim 1 wherein the heat exchanger has a secondary fluid outlet orifice, the secondary fluid discharge duct comprising a downstream crossing extending through the vessel and having an inner passage for the secondary fluid placed to coincide with the outlet orifice, the attachment comprising a plurality of attachers distributed around the inner passage and the outlet orifice. 4. The nuclear reactor as recited in claim 1 wherein the vessel has a substantially vertical central axis, the attachment attaching an upper end of the heat exchanger to the vessel. 5. The nuclear reactor as recited in claim 4 further comprising a guide device suitable for limiting the travel of a lower part of the heat exchanger in a horizontal plane, and allowing a movement of the lower part in the vertical direction relative to the vessel. 6. The nuclear reactor as recited in claim 1 wherein the attachment attaches the heat exchanger to the vessel such that the attachment is disassembleable. 7. The nuclear reactor as recited in claim 6 wherein the attachment includes a plurality of attachers attaching the heat exchanger to the vessel, the attachers disassembleable from outside the vessel. 8. The nuclear reactor as recited in claim 1 wherein the heat exchanger includes a plurality of plates stacked parallel to one another, the secondary fluid discharge duct passing through the vessel in a substantially radial direction relative to a central axis of the vessel, the plates being substantially perpendicular to the radial direction. 9. The nuclear reactor as recited in claim 1 wherein the heat exchanger includes a downstream secondary collector collecting the secondary fluid leaving the heat exchanger, the secondary fluid discharge duct and the downstream secondary collector being aligned with each other. 10. The nuclear reactor as recited in claim 9 wherein the heat exchanger includes a plurality of plates stacked parallel to one another and the downstream secondary collector extends through the plates. 11. The nuclear reactor as recited in claim 1 wherein the heat exchanger includes a plurality of plates stacked parallel to one another and the upstream secondary collector extends through the plates. 12. The nuclear reactor as recited in claim 1 wherein the heat exchanger includes a plurality of plates stacked parallel to one another and heat exchanger includes a plurality of primary channels delimited between the plates and traveled by the primary fluid, each primary channel having a main inlet and a main outlet, the heat exchanger having at least one hood delimiting a water tank in which the main inlets or the main outlets emerge. 13. The nuclear reactor as recited in claim 1 wherein the vessel includes a shroud and a cover attached on the shroud so as to be disassembleable, the heat exchanger being attached to the cover. 14. The nuclear reactor as recited in claim 1 further comprising absorbers for controlling the reactivity of the core, which are vertically movable relative to the core, the absorbers being situated above the core and the heat exchanger being situated above the absorbers. 15. The nuclear reactor as recited in claim 14 further comprising a maneuverer provided to maneuver the absorbers selectively, the maneuverer including actuators placed vertically above the heat exchangers and rods connecting the actuators to the absorbers, the nuclear reactor having several heat exchangers distributed around the rods. 16. The nuclear reactor as recited in claim 1 wherein the secondary fluid discharge duct includes a downstream crossing engaged in an orifice of the vessel, the attachment including a plurality of attachers attaching the heat exchanger to the vessel, the attachers and the downstream crossing being removable from the vessel from outside the vessel. 17. The nuclear reactor as recited in claim 16 further comprising a ring configured for keeping the heat exchanger suspended from the vessel after the downstream crossing is removed from the vessel. 18. The nuclear reactor as recited in claim 1 wherein the secondary fluid discharge duct includes a downstream crossing engaged in an orifice of the vessel, the attachment attaching the heat exchanger directly to the downstream crossing. 19. A nuclear reactor comprising:a vessel;a core provided in the vessel;at least one plate heat exchanger provided in the vessel;at least one secondary fluid supply duct for supplying a secondary fluid to the heat exchanger and a discharge secondary fluid duct for discharging the secondary fluid from the heat exchanger, the discharge secondary fluid duct extending through the vessel; andan attachment for attaching the heat exchanger to an area of the vessel through which the discharge secondary fluid duct extends,wherein the heat exchanger has a secondary fluid outlet orifice, the secondary fluid discharge duct comprising a downstream crossing extending through the vessel and having an inner passage for the secondary fluid placed to coincide with the outlet orifice, the attachment comprising a plurality of attachers distributed around the inner passage and the outlet orifice. 20. A nuclear reactor comprising:a vessel;a core provided in the vessel;at least one plate heat exchanger provided in the vessel;at least one secondary fluid supply duct for supplying a secondary fluid to the heat exchanger and a discharge secondary fluid duct for discharging the secondary fluid from the heat exchanger, the discharge secondary fluid duct extending through the vessel; andan attachment for attaching the heat exchanger to an area of the vessel through which the discharge secondary fluid duct extends,wherein the heat exchanger includes a downstream secondary collector collecting the secondary fluid leaving the heat exchanger, the secondary fluid discharge duct and the downstream secondary collector being aligned with each other,wherein the heat exchanger includes a plurality of plates stacked parallel to one another and the downstream secondary collector extends through the plates.