Nuclear reactor, with control and shutdown rods external to the core and core supporting structures

A nuclear reactor, comprising:

• a vessel closed at a top thereof by a radially external fixed closing structure and by a radially internal mobile closing structure, wherein:
• the vessel contains a core that is immersed in a primary cooling fluid of the vessel;
• and
• the core includes a plurality of fuel elements, control rods, shutdown rods, and a hydraulic separation structure delimiting a hot manifold and a cold manifold;
• the primary cooling fluid of the core circulates in the hot manifold and the cold manifold and, during normal operation of the nuclear reactor, a first free surface level of the primary fluid in the hot manifold differs from a second free surface level of the primary fluid in the cold manifold;
• circulation pumps for circulating the primary fluid;
• and
• heat exchangers;
• wherein the control rods and the shutdown rods are inserted in respective penetrations of the fixed closing structure and located radially external to the radially internal mobile closing structure and external to an upper portion of the hydraulic separation structure containing respective heads of the plurality of fuel elements;
• wherein the control rods and the shutdown rods are inserted in a radially wider lower part of the hydraulic separation structure via respective ducts that extend from a wall of the hydraulic separation structure above the second free surface of the primary fluid in the cold manifold.