A nuclear reactor is configured with an intermediate coolant loop for transferring thermal energy from the reactor core for a useful purpose. The intermediate coolant loop includes a bypass flowpath with an air heat exchanger for dumping reactor heat during startup and/or shutdown. A fluidic diode along the bypass flowpath asymmetrically restricts flow across the bypass flowpath, inhibiting flow in a first flow direction during a full power operating condition and allowing a relatively uninhibited flow in a second direction during a startup and/or shut down low power operating condition.

A nuclear reactor is configured with a primary coolant loop for transferring heat away from the nuclear reactor core. In a shutdown event, the primary coolant pump may stop pumping primary coolant through the reactor core, resulting in decay heat buildup within the reactor core. An inertial energy coast down system can store kinetic energy while the nuclear reactor is operating and then release the stored kinetic energy to cause the primary coolant to continue to flow through the nuclear reactor core to remove decay heat. The inertial energy coast down system may include an impeller and a flywheel having a mass. During normal reactor operation, the flowing primary coolant spins up the impeller and flywheel, and upon a shutdown event where the primary coolant pump stops pumping, the flywheel and impeller can cause the primary coolant to continue to flow during a coast down of the flywheel and impeller.

The invention concerns a nuclear reactor comprising a vessel closed at the top by a radially external fixed closing structure and by a radially internal mobile closing structure. The vessel contains a core immersed in a primary cooling fluid and comprising fuel elements, control rods, shutdown rods, and a hydraulic separation structure delimiting a hot manifold and a cold manifold in which the primary fluid circulates. The control rods and the shutdown rods are inserted in respective penetrations of the fixed closing structure and are therefore located radially external to the mobile closing structure and external to an upper portion of the separation structure containing respective heads of the fuel elements.

The invention concerns a nuclear reactor comprising a vessel closed at the top by a radially external fixed closing structure and by a radially internal mobile closing structure. The vessel contains a core immersed in a primary cooling fluid and comprising fuel elements, control rods, shutdown rods, and a hydraulic separation structure delimiting a hot manifold and a cold manifold in which the primary fluid circulates. The control rods and the shutdown rods are inserted in respective penetrations of the fixed closing structure and are therefore located radially external to the mobile closing structure and external to an upper portion of the separation structure containing respective heads of the fuel elements.

A molten fuel reactor includes a reactor core having substantially a right-circular cylinder shape with a longitudinal axis. At least one inlet is configured to channel fuel salt into the reactor core. At least one outlet is configured to channel fuel salt out of the reactor core, and the inlet and outlet at least partially define a flow loop of fuel salt with respect to the reactor core. An orifice ring plate is disposed within the reactor core and proximate the at least one inlet. The orifice ring plate is configured to condition a flow of fuel salt entering the reactor core from the at least one inlet. The orifice ring plate extends circumferentially about the longitudinal axis and has a height defined in a direction along the longitudinal axis. The orifice ring plate includes a plurality of apertures configured to allow the flow of fuel salt therethrough.

The invention concerns a nuclear reactor, comprising a vessel closed at the top by a radially external fixed closing structure and by a radially internal mobile closing structure and containing a core, immersed in a primary cooling fluid and comprising fuel elements and control and shutdown rods, and a hydraulic separation structure delimiting a hot manifold and a cold manifold in which the primary fluid circulates; the control rods and shutdown rods are inserted in respective penetrations of the fixed closing structure and are therefore located radially external to the mobile closing structure and external to an upper portion of the separation structure containing respective heads of the fuel elements.

The invention concerns a nuclear reactor, comprising a vessel closed at the top by a radially external fixed closing structure and by a radially internal mobile closing structure and containing a core, immersed in a primary cooling fluid and comprising fuel elements and control and shutdown rods, and a hydraulic separation structure delimiting a hot manifold and a cold manifold in which the primary fluid circulates; the control rods and shutdown rods are inserted in respective penetrations of the fixed closing structure and are therefore located radially external to the mobile closing structure and external to an upper portion of the separation structure containing respective heads of the fuel elements.

Configurations of molten fuel salt reactors are described that allow for active cooling of the containment vessel of the reactor by the primary coolant. Furthermore, naturally circulating reactor configurations are described in which the reactor cores are substantially frustum-shaped so that the thermal center of the reactor core is below the outlet of the primary heat exchangers. Heat exchanger configurations are described in which welded components are distanced from the reactor core to reduce the damage caused by neutron flux from the reactor. Radial loop reactor configurations are also described.

Configurations of molten fuel salt reactors are described that include an auxiliary cooling system which shared part of the primary coolant loop but allows for passive cooling of decay heat from the reactor. Furthermore, different pump configurations for circulating molten fuel through the reactor core and one or more in vessel heat exchangers are described.

A nuclear reactor is designed to couple the load path of control elements with the reactor core, thus reducing opportunity for differential movement between the control elements and the reactor core. A core barrel can be fabricated in a manufacturing facility to include the reactor core, control element supports, and control element drive system. The core barrel can be mounted to a reactor vessel head. Movement, such as through seismic forces, transmits an equal direction and magnitude to the control elements and the reactor core, thus inhibiting the opportunity for differential movement.