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 mitigation assembly for a nuclear reactor including a box with an upper portion forming the head of the assembly housing an upper neutron shielding device, including a head including removable lock and a slug installed free to move in translation relative over a given travel distance, the lock being configured such that locking/unlocking between the head and the box can be made by displacement of the slug with an extraction grab with its pawls attached in the slug. The lower part of the upper neutron shielding device includes a cone-shaped sealing block with the tip of the cone oriented downwards, cooperating with a cone-shaped internal surface of the box, a sealing device being formed between the two, the assembly created forming a removable sealing plug.

An electrochemically modulated molten salt reactor (EMMSR) that contains a vessel and a power source. The vessel houses a fuel salt, at least a portion of a neutron moderator, and at least a portion of an insulator. The fuel salt includes enough dissolved fissile isotopes to cause continued self-sustaining fission reactions during the operation of the EMMSR. The neutron moderator is configured to slow down fast neutrons produced by the dissolved fissile isotopes. The insulator is configured to electrically isolate the neutron moderator from the vessel. The power source has a positive potential and a negative potential. The positive potential is received by the neutron moderator and the negative potential is received by the vessel.

An electrochemically modulated molten salt reactor (EMMSR) that contains a vessel and a power source. The vessel houses a fuel salt, at least a portion of a neutron moderator, and at least a portion of an insulator. The fuel salt includes enough dissolved fissile isotopes to cause continued self-sustaining fission reactions during the operation of the EMMSR. The neutron moderator is configured to slow down fast neutrons produced by the dissolved fissile isotopes. The insulator is configured to electrically isolate the neutron moderator from the vessel. The power source has a positive potential and a negative potential. The positive potential is received by the neutron moderator and the negative potential is received by the vessel.

The invention provides a core of a fast reactor including a sodium plenum installed above a core fuel, which is capable of reliably reducing a void reactivity, and an operation method thereof. The core of a fast reactor including the sodium plenum installed above the core fuel is characterized in that a tip of a primary control rod is inserted into a core fuel region, and a tip of a backup control rod is arranged above an upper end of the core fuel region for operation.

The invention provides a core of a fast reactor including a sodium plenum installed above a core fuel, which is capable of reliably reducing a void reactivity, and an operation method thereof. The core of a fast reactor including the sodium plenum installed above the core fuel is characterized in that a tip of a primary control rod is inserted into a core fuel region, and a tip of a backup control rod is arranged above an upper end of the core fuel region for operation.

Designs for a low power, fast spectrum molten fuel nuclear reactor that can be used to advance the understanding of molten salt reactors, their design and their operation are described. Furthermore, the designs described may be adapted to extra-terrestrial use as described herein for use as a low-gravity, moon-, Mars-, or space-based power generator. These low power reactors include a reactor core volume defined by a radial neutron reflector enclosed in a reactor vessel, in which heated fuel salt flows from the reactor core through a duct between the radial neutron reflector and the reactor vessel and back into the reactor core. Heat generated from the fission in the reactor core is transferred from the molten fuel through the reactor vessel to a coolant, in the case of an experimental design, or directly to an extra-terrestrial environment, in the case of an extra-terrestrial design.

A closed-vessel molten salt reactor (cvMSR) is described herein. A cvMSR may comprise a suspended container, such as a metallic container, within a trench surrounded by a concrete enclosure and a concrete cover having a number of channels. The suspended container may be hollow and a solution of fissile materials and salt materials may be provided within the suspended container. The solution may be capable of undergoing a chain reaction nuclear fission process once a threshold temperature is reached. Heat generated by the solution may heat a fluid surrounding the suspended container. The heated fluid may be transported, through the number of channels of the concrete cover, to an external location where the heated fluid may be used in distributing heat and/or electricity generation.

This disclosure describes various configurations and components of a molten fuel fast or thermal nuclear reactor for managing the operating temperature in the reactor core. The disclosure includes various configurations of direct reactor auxiliary cooling system (DRACS) heat exchangers and primary heat exchangers as well as descriptions of improved flow paths for nuclear fuel, primary coolant and DRACS coolant through the reactor components.

A fast reactor core includes a sodium plenum installed above the fuel. The sodium plenum is capable of reducing a void reactivity. During operation, a tip of a primary control rod is inserted in a core fuel region, and a tip of a backup control rod is arranged near an upper end of the sodium plenum.