Abstract: An assembly is provided that includes at least one first conduit and at least one second conduit connected together through a connecting device. The connecting device includes an exteriorly threaded tube; a connecting part attached to one end of the tube and including an orifice; a holding nut screwed onto the tube and axially maintaining the connecting part relative to a tube; and a retaining member attached on the holding nut and engaging with the first conduit so as to axially retain the first conduit fitted into the orifice, the retaining member cooperating with the first conduit so as to oppose the unscrewing of the holding nut.

Abstract: The invention relates to a device for connecting the upper (21) and lower (23) guide ducts for guiding a thermocouple for the upper internals of a nuclear reactor. The device comprises a plug (41) fastened to the lower duct (23), comprising, on the one hand, a bore (43) for accommodating an end-piece (24) on the end of the upper duct (21) and, on the other hand, locking means (45) for locking it in a housing of a sleeve (32) of a tap (30), retaining means (48, 49) for keeping the plug (41) in the locked position in the sleeve (32), and means for blocking the plug (41) and for aligning the lower duct (23) and the upper duct (21) in said sleeve (32) of the tap (30).