Abstract: The replacement is performed from a repair area located above the convex face (1a) of the head. The adaptor to be replaced is machined, after dismounting its drive mechanism (13) and a thermal sleeve (4), by inserting an appropriate tool (14) via the upper end of the adaptor (3') to be replaced. Machining of the lower portion of the adaptor and of a portion of the weld of this adaptor, the machining of a narrow bevel in the weld of the adaptor to be replaced, reboring of the remaining portion of the adaptor to be replaced (3') inside the head (1), extraction of the adaptor, the installation, by cold shrink-fitting, of a replacement adaptor and the welding of the replacement adaptor are performed in succession.

Abstract: The welding electrode rotates at variable speed about the axis of the cylindrical part so as to lay down successive superposed layers, each covering the entire width of the bevel. The electrode is moved translationally in the direction of the axis of the cylindrical part. The device includes arrangements for adjusting the speed of rotation of the electrode and for moving it in the direction of the axis. The method may be used for welding a replacement adaptor onto the vessel head of a nuclear reactor.

Abstract: A high-speed abrasive liquid jet is directed at the surface of the component (13) with an angle of incidence between 30.degree. and 90.degree.. The jet is moved so as to sweep over the internal surface of the component (13). At least two successive machining passes are made. The speed of sweeping increases from one machining pass to the next. The device (30), mounted so as to move in translation and in rotation inside the adaptor (13), consists of a tube assembly supplied with pressurized liquid onto which a nozzle (33) is fixed.

Abstract: A removable platform comprises a chute (14) having a handling and fastening assembly (18, 19, 14a) at one of its ends and a supporting part (14b) in the form of a portion of a cylinder open laterally and extending the tube (14a) substantially in its axial direction, a supporting shaft (16) mounted in articulated manner at the end of the chute, an assembly of supporting arms (15) mounted for pivoting movement about the axis (29) of the supporting shaft (16) and a plurality of plane elements (17) resting on the supporting arms (15) in the unfolded position, to form a work platform substantially over the entire cross-section of the casing (2). The removable platform is introduced into the casing (2) in the folded-up state; the arms (15) form an assembly (30) seated in the chute (14), and the axis (20') at the supporting shaft (16) is substantially perpendicular to the longitudinal direction of the chute (14).

Abstract: A method of continuous welding of a series of tubes to a tube sheet, in which the torch current is decreased to produce partial fading of the arc after completion of the first welding bead, and the torch is then moved to a starting position on a second contour to be welded. A stationary preheat is then effected, and a second weld bead is made by following the second contour to be welded. The process continues until the last bead has been made, whereupon the arc is switched off.

Abstract: A heat exchanger water box for steam generators bounded by a hemispherical base and a tube sheet on which the ends of the U-shaped tubes of the exchanger are fixed, on either side of a partition plate separating the water box into two chambers, respectively for supply and evacuation. The partition plate (3) fits with clearance over its whole periphery into a circular groove and a diametrical groove (11) respectively provided in the inner walls of the hemispherical base (2) and the tube sheet (1), and the hemispherical base (2) has at least one drain orifice (26) passing through it which opens at the lowest point of the circular groove for fitting the plate.

Abstract: A surfacing plate for a boring and milling machine comprising a hollow cylindrical body provided with a rear end fixed to the milling spindle and a head on which a radial guide is formed for a tool holder slide. The movement of the slide is controlled by the boring spindle through a control unit located inside the body and comprising a central part sliding longitudinally in the body under the action of the spindle and having two longitudinal racks. The slide bears two radial racks connected respectively to the two longitudinal racks through two independant transmission trains, and is provided with means for adjusting the relative radial position of the two radial racks for taking up the play in the transmission.