A molten salt reactor includes a containment vessel, a reactor core, a neutron reflector spaced from the containment vessel, and liquid fuel enclosed within the core. The liquid fuel is comprised of a nuclear fission material dissolved in a molten salt. A heat exchanger is positioned external to the containment vessel. A plurality of heat transfer pipes are provided for transferring heat from the core to the heat exchanger. Each pipe has a first and a second end. The first end of each pipe is positioned within the reactor core for absorbing heat from the fuel. The heat exchanger receives the second end of each heat transfer pipe. At least two or more reactor shut down systems are provided. At least one shut down system may be a passive system and at least one or both shut down systems may be an active or a manually operated system.

A high temperature gas cooled reactor steam generation system (1) includes a nuclear reactor (2) that has helium gas as a primary coolant and heats the primary coolant by heat generated by a nuclear reaction that decelerates neutrons by a graphite block, a steam generator (3) that has water as a secondary coolant and heats the secondary coolant by the primary coolant via the nuclear reactor (2) to generate steam, a steam turbine (4) that is operated by the steam from the steam generator (3), and a generator (5) that generates electricity according to an operation of the steam turbine (4). Moreover, the system (1) includes pressure adjustment means for setting a pressure of the secondary coolant in the steam generator (3) to be lower than a pressure of the primary coolant in the nuclear reactor (2).

A high temperature gas cooled reactor steam generation system (1) includes a nuclear reactor (2) that has helium gas as a primary coolant and heats the primary coolant by heat generated by a nuclear reaction that decelerates neutrons by a graphite block, a steam generator (3) that has water as a secondary coolant and heats the secondary coolant by the primary coolant via the nuclear reactor (2) to generate steam, a steam turbine (4) that is operated by the steam from the steam generator (3), and a generator (5) that generates electricity according to an operation of the steam turbine (4). Moreover, the system (1) includes pressure adjustment means for setting a pressure of the secondary coolant in the steam generator (3) to be lower than a pressure of the primary coolant in the nuclear reactor (2).

A modular nuclear reactor system includes a lift-out, replaceable nuclear reactor core configured for replacement as a singular unit during a single lift-out event, such as rather than lifting and replacing individual fuel assemblies and/or fuel elements. The system includes a reactor vessel and a power generation system configured to convert thermal energy in a high temperature working fluid received from the reactor vessel into electrical energy. The reactor vessel includes: a vessel inlet and an adjacent vessel outlet arranged near a bottom on the vessel; a vessel receptacle configured to receive a unified core assembly; locating datums in the base of the vessel receptacle and configured to constrain a core assembly in multiple degrees of freedom; and an interstitial zone surrounding the vessel receptacle and housing a set of control or moderating drums.

A molten salt reactor is described that includes a containment vessel, a reactor core housed within the containment vessel, a neutron reflector spaced from the containment vessel and positioned between the core and the containment vessel, a liquid fuel comprised of a nuclear fission material dissolved in a molten salt enclosed within the core, a plurality of heat transfer pipes, each pipe having a first and a second end, wherein the first end is positioned within the reactor core for absorbing heat from the fuel, a heat exchanger external to the containment vessel for receiving the second end of each heat transfer pipe for transferring heat from the core to the heat exchanger, and at least one and preferably two or more reactor shut down systems, where at least one may be a passive system and at least one or both may be an active or a manually operated system. The liquid fuel in the core is kept within the core and heat pipes are used to carry only the heat from the liquid core to the heat exchanger.

An enhanced architecture for a nuclear reactor core includes: (1) nuclear fuel tiles (S-Block); and (2) a thermal insulator and tube liners with a solid-phase moderator (U-Mod) to improve safety, reliability, heat transfer, efficiency, and compactness. In S-Block, nuclear fuel tiles include a fuel shape designed with an interlocking geometry pattern to optimize heat transfer between nuclear fuel tiles and into a fuel coolant and bring the fuel coolant in direct contact with the nuclear fuel tiles. Nuclear fuel tiles can be shaped with discontinuous nuclear fuel lateral facets and have fuel coolant passages formed therein to provide direct contact between the fuel coolant and the nuclear fuel tiles. In U-Mod, tube liners with hydrogen diffusivity retain hydrogen in the solid-phase moderator even at elevated temperatures and the thermal insulator insulates the solid-phase moderator from the nuclear fuel tiles.

A modular nuclear reactor system includes a lift-out, replaceable nuclear reactor core configured for replacement as a singular unit during a single lift-out event, such as rather than lifting and replacing individual fuel assemblies and/or fuel elements. The system includes a reactor vessel and a power generation system configured to convert thermal energy in a high temperature working fluid received from the reactor vessel into electrical energy. The reactor vessel includes: a vessel inlet and an adjacent vessel outlet arranged near a bottom on the vessel; a vessel receptacle configured to receive a unified core assembly; locating datums in the base of the vessel receptacle and configured to constrain a core assembly in multiple degrees of freedom; and an interstitial zone surrounding the vessel receptacle and housing a set of control or moderating drums.