Abstract: Control safety valve means for an enclosure containing a pressurized fluid. With the cylindrical chamber, the piston defines a pressure chamber for closing the main valve, the pressure chamber being linked with the enclosure by a passage. The piston has a face directed towards the closing pressure chamber A of the main valve, and the surface of the piston face directed towards the main valve closing chamber is greater than the surface of the main valve directed towards the enclosure. The main valve is located on the side of the outlet with respect to the seat of the valve means.

Abstract: It comprises a valve body constituted by a cylinder, defining a chamber and a seat, a valve placed in the cylinder and having a stem, a main flap and a plunger sliding in the chamber, means for elastically applying the main flap to the seat, a passage establishing a connection between the chamber and the pressurized enclosure. The passage is provided by a channel, which axially traverses the valve. A hole incorporating a metering hole links the chamber with the atmosphere.

Abstract: The device comprises at least one compartment grid formed by tube elements of small height placed in juxtaposed relation and each traversed axially by one pin of the bundle. The tube elements are rigidly fixed to each other at successive points in the grid and relatively displaced along the height of the pins so as to be distributed in at least one helix.

Abstract: The safety device comprises an absorber element connected by a separable coupling to the lower end of a vertical operating stem. When released, the absorber element drops under gravity from a top position to a bottom position within an open-topped casing placed among wrappers containing fuel pin bundles. In the top position of the absorber element, the disconnectable coupling is placed at the top and partly within the interior of the casing while the absorber element extends within said casing into the peripheral blanket zone located externally of the central fuel zone.

Abstract: A supporting member for an array of parallel rails each carrying one row of slidably mounted pins of a fuel cluster is placed coaxially at the lower end of a vertical fuel assembly wrapper. Each parallel rail is provided at each end with a downward extension and terminal lug which engages in a lateral groove formed in the periphery of the supporting member in order to lock and maintain the rails and the fuel pins in uniformly spaced relation within the fuel assembly wrapper.