A nuclear reactor is provided that comprises a vessel that houses a core, comprising a bundle of fuel elements, and immersed in a primary cooling fluid of the core; the fuel elements extend along respective longitudinal and parallel axes and are mechanically supported by respective heads joined to each other and joined to an anchoring structure by support devices acting between adjacent fuel elements, or acting between fuel elements situated on the periphery of the core and the anchoring structure, and which constitute an integral part of the heads of the fuel elements.

A nuclear reactor is provided that comprises a vessel that houses a core, comprising a bundle of fuel elements, and immersed in a primary cooling fluid of the core; the fuel elements extend along respective longitudinal and parallel axes and are mechanically supported by respective heads joined to each other and joined to an anchoring structure by support devices acting between adjacent fuel elements, or acting between fuel elements situated on the periphery of the core and the anchoring structure, and which constitute an integral part of the heads of the fuel elements.

Systems and methods for providing a molten salt reactor can include a graphite reactor core that defines an internal space, with multiple fuel wedges being received in the internal space, and with the wedges each defining a fuel channel extending from a first end to a second end of each of the wedges. The reactor can further include a fuel pin rod that defines an internal fuel conduit and that is disposed between at least two of the wedges. The reactor core can also define a fuel ingress port and a fuel egress port. The reactor core can further be rotatably received within a reactor housing such that the ports are configured to become at least one of more occluded and less occluded as the reactor core rotates.

Methods of controlling the reactivity of a molten salt fission reactor. The molten salt fission reactor comprises a core and a coolant tank (101), the core comprising fuel tubes (103) containing a molten salt fissile fuel, and the coolant tank containing a molten salt coolant (102), wherein the fuel tubes are immersed in the coolant tank. The methods comprise dissolving a neutron absorbing compound in the molten salt coolant, the neutron absorbing compound comprising a halogen and a neutron absorbing element. The first method further comprises reducing the neutron absorbing compound to a salt of the halogen and an insoluble substance comprising the neutron absorbing element, the halogen being fluorine or chlorine, wherein the insoluble substance is not volatile at a temperature of the coolant during operation of the reactor. In the second method the one or more neutron absorbing compounds are chosen such that reduction of the neutron absorbing capacity of the one or more neutron absorbing compounds due to absorption of neutrons compensates for a fall in reactivity of the core in order to control fission rates in the core. Apparatus for implementing the methods are also provided.

Methods of controlling the reactivity of a molten salt fission reactor. The molten salt fission reactor comprises a core and a coolant tank (101), the core comprising fuel tubes (103) containing a molten salt fissile fuel, and the coolant tank containing a molten salt coolant (102), wherein the fuel tubes are immersed in the coolant tank. The methods comprise dissolving a neutron absorbing compound in the molten salt coolant, the neutron absorbing compound comprising a halogen and a neutron absorbing element. The first method further comprises reducing the neutron absorbing compound to a salt of the halogen and an insoluble substance comprising the neutron absorbing element, the halogen being fluorine or chlorine, wherein the insoluble substance is not volatile at a temperature of the coolant during operation of the reactor. In the second method the one or more neutron absorbing compounds are chosen such that reduction of the neutron absorbing capacity of the one or more neutron absorbing compounds due to absorption of neutrons compensates for a fall in reactivity of the core in order to control fission rates in the core. Apparatus for implementing the methods are also provided.

A low pressure water reactor (LPWR) and a method for controlling a LPWR; the LPWR comprises a reactor vessel with an internal cavity comprising a primary coolant, a riser tube, and a core located below ground level with 6-15 bars atmosphere pressure; a steam drum connected to the riser tube at ground level at a pressure of 1-10 bars absolute; a water storage tank to store borated water; a passive injection system injecting the borated water from the water storage tank into the vessel; and low pressure steam turbines generating power at 1-10 bars atmosphere. The vessel heats water up to temperature and the riser tube converts the heated water to steam, delivered to the turbine(s). The conversion creates a difference in a primary coolant density that initiates a density-driven natural circulation of the primary coolant in the riser tube, downcomer, steam drum and core.

A low pressure water reactor (LPWR) and a method for controlling a LPWR; the LPWR comprises a reactor vessel with an internal cavity comprising a primary coolant, a riser tube, and a core located below ground level with 6-15 bars atmosphere pressure; a steam drum connected to the riser tube at ground level at a pressure of 1-10 bars absolute; a water storage tank to store borated water; a passive injection system injecting the borated water from the water storage tank into the vessel; and low pressure steam turbines generating power at 1-10 bars atmosphere. The vessel heats water up to temperature and the riser tube converts the heated water to steam, delivered to the turbine(s). The conversion creates a difference in a primary coolant density that initiates a density-driven natural circulation of the primary coolant in the riser tube, downcomer, steam drum and core.

A nuclear reactor is designed to couple the load path of the control elements with the reactor core, thus reducing the opportunity for differential movement between the control elements and the reactor core. A cartridge core barrel can be fabricated in a manufacturing facility to include the reactor core, control element supports, and control element drive system. The cartridge core barrel can be mounted to a reactor vessel head, and any 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.

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.

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.