The present invention relates to a device for mating with an irradiated fuel container under a pit of a nuclear facility and containing irradiated fuel. According to the invention, the mating device is characterized in that it comprises a mating flange (15) secured to the lower end of the metallic bellows (6) and actuators (10) are interposed between the structure (7) of the penetration (3) and the mating flange (15) in order to transmit the translational movement of the actuators (10) to the bottom end of the metallic bellows (6) and to the gasket-bearing flange (11), and the mating flange (15) comprises at least two controlled latches (24) able to lock the mating flange (15) to the container (2) when the bottom end of the bellows(6) is in the lowered position so as to keep the gasket-bearing flange (11) pressed hermetically against the top surface of the container (2).