An upper supporting structure for the internal parts of nuclear reactor vessels

A standard nuclear reactor includes a core composed of a number of fuel assemblies housed in a pressure vessel. A coolant, such as water or liquid metal, is made to flow through the core where it absorbs the calorific energy subsequently used to vaporise a fluid and drive a turbo-generator. An upper core plate is placed over these assemblies to prevent them from moving upwards. An upper supporting structure is mounted in the vessel so as to be at a given distance above the upper core plate. This upper supporting structure supports the internal upper parts of the reactor. It takes the shape of a top hat resting on its crown with an edge forming a supporting collar which is borne by the vessel, and a horizontal transversal part placed under the collar and carrying the supporting columns. By this arrangement, the length of the bearing columns and guide tubes is reduced