Device and method for shutting off an orifice of a bundle wrapper of a steam generator of a pressurized-water nuclear reactor

The invention relates to a device (20) for shutting off an inner orifice of a bundle wrapper of a steam generator comprising a movable shaft (21) comprising a pair of lower half-flanges (25, 26), a pair of upper half-flanges (27, 28) which can be rotated by the said shaft (21) substantially through 180° between a low position facing the lower half-flanges (25, 26), for introduction into the orifices of the casing and the wrapper of the steam generator, and a high position opposite the said lower half-flanges (25, 26), and means (22) for clamping the lower half-flanges (25, 26) and the upper half-flanges (27, 28) on the peripheries arranged on either side of the inner orifice, in order to shut off this inner orifice. The invention also relates to a shutting-off method and to a tooling for installing and removing the shut-off device.