A nuclear steam supply system having a start-up sub-system for heating a primary coolant. The nuclear steam supply system comprises a reactor vessel with core comprising nuclear fuel, and steam generating vessel fluidly coupled to the reactor vessel. A primary coolant loop formed within the reactor vessel and the steam generating vessel circulates primary coolant through the loop. A steam supply start-up sub-system is fluidly coupled to the primary coolant loop. The start-up sub-system is configured and operable to: (1) extract and receive a portion of the primary coolant from the primary coolant loop; (2) heat the portion of the primary coolant to form a heated portion of the primary coolant; and (3) inject the heated portion of the primary coolant back into the primary coolant loop.

An installation includes: a plurality of pilings securable to a bed under a surface of a body of water; a base structure disposed atop the plurality of pilings; and a module disposable on the base structure, wherein the module is positioned and securable on the base structure after being floated on the surface of the body of water over the base structure.

An installation includes: a plurality of pilings securable to a bed under a surface of a body of water; a base structure disposed atop the plurality of pilings; and a module disposable on the base structure, wherein the module is positioned and securable on the base structure after being floated on the surface of the body of water over the base structure.

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.

A nuclear reactor system that, in one embodiment, utilizes natural circulation to circulate a primary coolant in a single-phase through a reactor core and a heat exchange sub-system. The heat exchange sub-system is located outside of the nuclear reactor pressure vessels and, in some embodiments, is designed so as to not cause any substantial pressure drop in the flow of the primary coolant within the heat exchange sub-system that is used to vaporize a secondary coolant. In another embodiment, a nuclear reactor system is disclosed in which the reactor core is located below ground and all penetrations into the reactor pressure vessel are located above ground.

A nuclear reactor seismic isolation assembly includes an enclosure that defines a volume; a plastically-deformable member mounted, at least in part, within the volume; and a stretching member moveable within the enclosure to plastically-deform the plastically-deformable member in response to a dynamic force exerted on the enclosure.

A nuclear reactor seismic isolation assembly includes an enclosure that defines a volume; a plastically-deformable member mounted, at least in part, within the volume; and a stretching member moveable within the enclosure to plastically-deform the plastically-deformable member in response to a dynamic force exerted on the enclosure.

In conjunction with a pressurized water reactor (PWR) and a pressurizer configured to control pressure in the reactor pressure vessel, a decay heat removal system comprises a pressurized passive condenser, a turbine-driven pump connected to suction water from at least one water source into the reactor pressure vessel; and steam piping configured to deliver steam from the pressurizer to the turbine to operate the pump and to discharge the delivered steam into the pressurized passive condenser. The pump and turbine may be mounted on a common shaft via which the turbine drives the pump. The at least one water source may include a refueling water storage tank (RWST) and/or the pressurized passive condenser. A pressurizer power operated relief valve may control discharge of a portion of the delivered steam bypassing the turbine into the pressurized passive condenser to control pressure in the pressurizer.

The systems and methods generally include a nuclear power plant unit assembled in a shipyard from a plurality of structural modules, each of the structural modules having manufactured components for use in power production when moored or fixed to a floor at least one of in and proximal to at least one of an offshore marine environment, a river environment and a coastal marine environment. The nuclear power plant unit is subdivided into at least one arrangement of structural modules that includes an electrical interface for one of transmitting electrical power generated by the nuclear unit and powering a system of the unit, a communications interface for communications internal or external to the unit, a user interface that is configured to permit a user to access a system of the unit, and a network interface for data communications to or from the unit.

The systems and methods generally include a nuclear power plant unit assembled in a shipyard from a plurality of structural modules, each of the structural modules having manufactured components for use in power production when moored or fixed to a floor at least one of in and proximal to at least one of an offshore marine environment, a river environment and a coastal marine environment. The nuclear power plant unit is subdivided into at least one arrangement of structural modules that includes an electrical interface for one of transmitting electrical power generated by the nuclear unit and powering a system of the unit, a communications interface for communications internal or external to the unit, a user interface that is configured to permit a user to access a system of the unit, and a network interface for data communications to or from the unit.