Safety device for a nuclear reactor and especially a fast reactor

In a fast nuclear reactor having a reactor core, a safety device comprising an articulated absorber element, a supporting head for said element, a disconnectable coupling joining said head to the lower extremity of an axially movable vertical operating stem, said absorber element after separation of the disconnectable coupling dropping under gravity from a top position to a bottom position within a passage through the reactor core, a casing for said passage open at the upper extremity thereof and located within the core among wrappers containing nuclear fuel and having the same length as said wrappers, the upper part of said casing being located at the same level as said wrappers, the reactor core being cooled by an upward circulation of liquid metal, a central fuel zone in said core, a peripheral blanket zone in said core which completely surround the central zone, said disconnectable coupling being an electromagnet armature on said stem and in the top position of said absorber element being located about the same level as the upper part of said casing, said head being engaged within said casing, said absorber element extending in said casing through said peripheral blanket zone externally of said central zone, said head of said absorber element in the bottom position engaging an external annular projection on said head with an internal abutment shoulder in said casing to stop the fall of said absorber element at the vertical level of said central core zone and means formed by said head and said casing for damping the fall of said element by acting on said head of said absorbent element.