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

Device for shutting off an inner orifice (10) of a bundle wrapper (3) of a steam generator (1) of a pressurized-water nuclear reactor, the said bundle wrapper (3) being arranged concentrically within a pressure casing (2) provided with an outer orifice (9) coinciding with the axis of the inner orifice (10), and the said inner orifice (10) having a diameter substantially equal to the outer orifice (9), characterized in that it comprises 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 said orifices (9, 10) and a high position opposite the said lower half-flanges (25, 26), and
• means (22) for clamping the lower half-flanges (25, 26), on the one hand, and the upper half-flanges (27, 28), on the other hand, on the peripheries arranged on either side of the inner orifice (10), in order to shut off this inner orifice (10).