Abstract: Device for locking a guide ring on a plate having an orifice comprising a tubular intermediate piece (22) fastened rigidly to a plate (20) so that its central orifice (36) is coaxial with the orifice (32) in the plate (20), receptacles (28) machined radially in the intermediate piece (22) and separated by passages open towards one end of the intermediate piece, and attachment parts (39) which match the receptacles (28) of the intermediate piece (22) and which are associated with the guide ring (21). The invention is used particularly for locking the guide ring of an extension piece on a guide tube of a light-water nuclear reactor.

Abstract: Apparatus for partitioning off the core of a nuclear reactor constituted by a set of boxes (8, 9, 10, 11) each comprising at least two plates (12-13, 14-15, 27-29, 28-30) rigidly assembled at right angles and disposed in the longitudinal direction of the assemblies, and a plurality of transverse plates (32) perpendicular to the longitudinal plates. The boxes are removably disposed side by side inside the core casing (1), and bearing thereon. The faces of the longitudinal plates directed towards the reactor core serve as bearing faces for the assemblies. Each of the boxes is fixed to at least one of the upper or lower plates of the core by a flexible coupling allowing longitudinal displacement.