The invention relates to a device for the sealed docking (14) of mobile containers (42) equipped with plugs (44) of various diameters on a containment box (10). The device includes a center disk (22) and at least one docking flange (20a, 20b, 20c) that are concentric to each other, normally plugging the access opening (18) of the containment box. A locking/unlocking mechanism (24) makes it possible to only unlock the center disk (22) alone or the center disk and one or more of the docking flanges (20a, 20b, 20c), according to the diameter of the plug (44). This arrangement makes it possible, in particular, to clean the plug (44) of a mobile container (42) serving to transport contaminated nuclear equipment.