Removable platform for working inside a casing of a pressurizer of a pressurized-water nuclear reactor

Removable platform for working inside a casing of a generally cylindrical pressurizer of a pressurized-water nuclear reactor, arranged with its axis vertical and closed at its upper end by a domed bottom through which passes at least one inspection port, said platform being adapted to being installed in said casing and dismounted and extracted by means of operations conducted from outside said casing, said platform comprising

• (a) a chute having a handling and fastening assembly at a first end of said chute, consisting of an element for catching on a lifting means, a cylindrical tube and a flange for engaging it into an inspection orifice of said casing and fastening it by screwing of said flange to an outer part of said casing, and a supporting part in a form of a portion of a cylinder open laterally and extending said tube substantially in an axial direction of said tube;
• (b) a supporting shaft mounted in an articulated manner at a second end of said chute opposite said first end, said second end being located in the vicinity of an axis of said casing when said chute is installed in said casing, an axis of articulation of said supporting shaft then being in a horizontal position, so that said supporting shaft can pivot between a folded-up position substantially perpendicular to a longitudinal direction of said chute and an operating position in which said support shaft is substantially coaxial relative to said casing;
• (c) an assembly of supporting arms mounted on said supporting shaft for pivoting movement between a folded-up position in which said supporting arms are substantially parallel to and laid against one another, said supporting arms then being capable of being placed and maintained in said chute in its axial direction, said supporting shaft being in its folded-up position, and an unfolded position in which said arms (15), by pivoting about said axis of said supporting shaft in vertical position, can be placed in angular arrangements distributed substantially uniformly about said axis (20) of said casing (2);
• and
• (d) a plurality of plane elements intended for resting on said supporting arms in unfolded position, to form a work platform over substantially an entire cross-section of said casing (2).