Abstract: Apparatus for the pyrotechnic cutting of a submerged tube.The apparatus, which is introduced into the tube, comprises in a conventional manner a chassis on which is mounted a support for a pyrotechnic charge, a shield in the upper part of the chassis and a compressed air intake for producing an air pocket below the shield. According to the invention, the apparatus also comprises a ballast for facilitating its lowering to a considerable depth and the charge is a detonating cord with a hollow charge extending continuously over the support, the clearance between the charge and the inner wall of the tube being of minimum size and the same throughout.

Abstract: A first assembly for low-speed translational displacement and dropping of a control rod comprises a leak-tight casing tube which communicates with the reactor vessel, a screw and nut system coupled to the control rod by means of the nut and a screw-retaining device which is capable of releasing the screw. In the event of accidental failure of the casing tube, upward displacement of the control rod and of the broken portion of the casing tube is limited by a second assembly comprising means for rotational locking of the screw drive rotor and calibrated elastic means for producing action on the rotor in opposition to the vertical thrust produced by failure of the casing tube.