Abstract: The ultrasonic transducer (5) is moved along the axial direction of elements of elongate shape (1), and is electrically excited for the emission of ultrasonic waves. Electrical measurement currents originating from the transducer (5) are collected and analyzed. The transducer (5) comprises a support having a concave active surface having curved generatrices and a plurality of piezoelectric elements fixed to the active surface of the support in adjacent dispositions.

Abstract: The tank contains a liquid in which a radioactive element emitting gamma radiation is distributed substantially uniformly. A photon detector (15) is disposed in the vicinity of the external surface of a measurement, zone of the wall (12), a count is made of the photons emitted by the radioactive element distributed in the liquid (7), through the measurement zone of the wall (12), a number of photons determined by counting is compared with a reference number emitted by the radioactive element through a reference zone of the wall (12) and it is deduced therefrom whether or not a defect (8) is present in the measurement zone of the wall (12). The measurement device comprises a photon detector (15) disposed at one end of a collimator (16) made of heavy metal traversed by channels or windows (17).

Abstract: A transverse cut (18, 19) is made on a heat exchanger tube (4) to be replaced in the vicinity of its connectors (14, 15), at each end. A cut (19') is made in the frustoconical zone (16') of connection of the tube (4) to the second connector (15). The cutting operations are effected from inside the tube (4) and through one of the tube plates (2, 3). The tube (4) to be replaced is extracted from the heat exchanger through the interior of the second connector (15) and the corresponding opening (13) in the second tube plate (3). A replacement tube is introduced into the heat exchanger through the opening (13) in the second tube plate (3) until a first end of the tube engaged in the heat exchanger reaches the level of the cut zone (18) of the first connector (14). The first end of the tube is welded on the first connector (14).