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.

An energy production device may include a core and a heat exchanger positioned over the core. The core may include one or more fuel rods. The core may further include a heat transmission fluid configured to flow through natural convection upwards through the one or more fuel rods and collect heat therefrom. The core may also include a reaction control device including a neutron-absorbing material. The heat exchanger may be configured to receive the heat transmission fluid and transfer the heat to an energy harnessing device positioned on an opposite side of the heat exchanger from the core.

An energy production device may include a core and a heat exchanger positioned over the core. The core may include one or more fuel rods. The core may further include a heat transmission fluid configured to flow through natural convection upwards through the one or more fuel rods and collect heat therefrom. The core may also include a reaction control device including a neutron-absorbing material. The heat exchanger may be configured to receive the heat transmission fluid and transfer the heat to an energy harnessing device positioned on an opposite side of the heat exchanger from the core.

A power conversion system for converting thermal energy from a heat source to electricity is provided. The system includes a chamber including an inner shroud having an inlet and an outlet and defining an internal passageway between the inlet and the outlet through which a working fluid passes. The chamber also includes an outer shroud substantially surrounding the inner shroud. The chamber includes a source heat exchanger disposed in the internal passageway, the source heat exchanger being configured to receive a heat transmitting element associated with the heat source external to the chamber, and to transfer heat energy from the heat transmitting element to the working fluid. The system also includes a compressor disposed adjacent the inlet of the inner shroud and configured to transfer energy from the compressor to the working fluid, and an expander disposed adjacent the outlet of the inner shroud.

A flow control device configured to be positioned in a reactor core. The flow control device including a central shaft and at least one blade extending helically from the central shaft. A nuclear reactor and related systems and methods are also disclosed.

Ensuring a high output temperature while preventing leakage of radioactive substances, etc. A nuclear reactor includes a fuel unit; a shield unit that covers a circumference of the fuel unit for shielding from radioactive rays; and a heat conductive portion that penetrates the shield unit, is arranged such that the heat conductive portion extends to inside of the fuel unit and outside of the shield unit, and transfers heat of the fuel unit to the outside of the shield unit by solid heat conduction.

Passive reactivity control technologies that enable reactivity control of a nuclear thermal propulsion (NTP) system with little to no active mechanical movement of circumferential control drums. By minimizing or eliminating the need for mechanical movement of the circumferential control drums during an NTP burn, the reactivity control technologies simplify controlling an NTP reactor and increase the overall performance of the NTP system. The reactivity control technologies mitigate and counteract the effects of xenon, the dominant fission product contributing to reactivity transients. Examples of reactivity control technologies include, employing burnable neutron poisons, tuning hydrogen pressure, adjusting wait time between burn cycles or merging burn cycles, and enhancement of temperature feedback mechanisms. The reactivity control technologies are applicable to low-enriched uranium NTP systems, including graphite composite fueled and tungsten ceramic and metal matrix (CERMET), or any moderated NTP system, such as highly-enriched uranium graphite composite NTP systems.

Passive reactivity control technologies that enable reactivity control of a nuclear thermal propulsion (NTP) system with little to no active mechanical movement of circumferential control drums. By minimizing or eliminating the need for mechanical movement of the circumferential control drums during an NTP burn, the reactivity control technologies simplify controlling an NTP reactor and increase the overall performance of the NTP system. The reactivity control technologies mitigate and counteract the effects of xenon, the dominant fission product contributing to reactivity transients. Examples of reactivity control technologies include, employing burnable neutron poisons, tuning hydrogen pressure, adjusting wait time between burn cycles or merging burn cycles, and enhancement of temperature feedback mechanisms. The reactivity control technologies are applicable to low-enriched uranium NTP systems, including graphite composite fueled and tungsten ceramic and metal matrix (CERMET), or any moderated NTP system, such as highly-enriched uranium graphite composite NTP systems.

A composite moderator medium for nuclear reactor systems and a method of fabricating a composite moderator block formed of the composite moderator medium. The composite moderator medium includes two or more moderators, such as a low moderating material and a high moderating material. The high moderating material has a higher neutron slowing down power compared to the low moderating material. The low moderating material includes a moderating matrix of silicon carbide or magnesium oxide. The high moderating material is dispersed within the moderating matrix and includes beryllium, boron, or a compound thereof. The high moderating material is encapsulated within the low moderating material such that the high moderating material is not exposed outside of the low moderating material. The method can include selecting a sintering aid and a weight percent of the sintering aid in a composite moderator mixture based on the low moderating material and spark plasma sintering.

Systems and methods for providing and using molten salt reactors are described. While the systems can include any suitable component, in some cases, they include a graphite reactor core defining an internal space that houses one or more fuel wedges, where each wedge defines one or more fuel channels that extend from a first end to a second end of the wedge. In some cases, one or more of the fuel wedges comprise multiple wedge sections that are coupled together end to end and/or in any other suitable manner. In some cases, one or more alignment pins also extend between two sections of a fuel wedge to align the sections. In some cases, one or more seals are also disposed between two sections of a fuel wedge. Thus, in some cases, the reactor core can be relatively long (e.g., to be a pipeline reactor). Other implementations are also described.