An apparatus having a nuclear reactor comprising a pressure vessel containing primary coolant water and further containing a nuclear reactor core comprising fissile material, a mounting/electrical distribution plate secured entirely within the pressure vessel and configured to be submerged in the primary coolant, a set of control rod drive mechanism (CRDM) units mounted directly on the mounting/electrical distribution plate, and a plurality of cable modules mounted in receptacles of the mounting/electrical distribution plate wherein each cable module includes mineral insulated (MI) cables connected with one or more of the CRDM units, the cable module including its MI cables being removable as a unit from the receptacle of the mounting/electrical distribution plate.

The present disclosure is directed to systems and methods useful for the construction and operation of a Modular Integrated Gas High-Temperature Reactor (MIGHTR). The MIGHTR includes a reactor core assembly disposed at least partially within a core baffle within a first high-pressure shell portion, a thermal transfer assembly disposed at least partially within a flow separation barrel within a second high-pressure shell portion. The longitudinal axes of the first high-pressure shell portion and the second high-pressure shell portion may be collinear. The reactor core assembly may be accessed horizontally for service, maintenance, and refueling. The core baffle may be flexibly displaceably coupled to the flow separation barrel. Coolant gas flows through the reactor core assembly and into the thermal transfer assembly where the temperature of the coolant gas is reduced. A plurality of coolant gas circulators circulate the cooled coolant gas from the thermal transfer assembly to the reactor core assembly.

The present disclosure is directed to systems and methods useful for the construction and operation of a Modular Integrated Gas High-Temperature Reactor (MIGHTR). The MIGHTR includes a reactor core assembly disposed at least partially within a core baffle within a first high-pressure shell portion, a thermal transfer assembly disposed at least partially within a flow separation barrel within a second high-pressure shell portion. The longitudinal axes of the first high-pressure shell portion and the second high-pressure shell portion may be collinear. The reactor core assembly may be accessed horizontally for service, maintenance, and refueling. The core baffle may be flexibly displaceably coupled to the flow separation barrel. Coolant gas flows through the reactor core assembly and into the thermal transfer assembly where the temperature of the coolant gas is reduced. A plurality of coolant gas circulators circulate the cooled coolant gas from the thermal transfer assembly to the reactor core assembly.

A method of cooling a nuclear reactor core is disclosed. The method includes contacting the nuclear reactor core with an aqueous solution comprising at least one of polyhedral boron hydride anions or carborane anions. Nuclear reactors are also disclosed. The nuclear reactor has a neutron moderator that is an aqueous solution comprising at least one of polyhedral boron hydride anions or carborane anions, or the nuclear reactor has an emergency core cooling system including a vessel containing a volume of an aqueous solution comprising at least one of polyhedral boron hydride anions or carborane anions. The nuclear reactor can also have both an aqueous solution comprising at least one of polyhedral boron hydride anions or carborane anions as a neutron moderator and an emergency core cooling system that includes an aqueous solution comprising at least one of polyhedral boron hydride anions or carborane anions.

A method of cooling a nuclear reactor core is disclosed. The method includes contacting the nuclear reactor core with an aqueous solution comprising at least one of polyhedral boron hydride anions or carborane anions. Nuclear reactors are also disclosed. The nuclear reactor has a neutron moderator that is an aqueous solution comprising at least one of polyhedral boron hydride anions or carborane anions, or the nuclear reactor has an emergency core cooling system including a vessel containing a volume of an aqueous solution comprising at least one of polyhedral boron hydride anions or carborane anions. The nuclear reactor can also have both an aqueous solution comprising at least one of polyhedral boron hydride anions or carborane anions as a neutron moderator and an emergency core cooling system that includes an aqueous solution comprising at least one of polyhedral boron hydride anions or carborane anions.

A power distribution plate (PDP) sits on top of a support plate. Control rod drive mechanism (CRDM) units are mounted on top of the PDP, but the PDP is incapable of supporting the weight of the CRDM units and instead transfers the load to a support plate. The PDP has receptacles which receive cable modules each including mineral insulated (MI) cables, the MI cables being connected with the CRDM units. The PDP may further include a set of hydraulic lines underlying the cable modules and connected with the CRDM units. The cable modules in their receptacles define conduits or raceways for their MI cables and for any underlying hydraulic lines.

A power distribution plate (PDP) sits on top of a support plate. Control rod drive mechanism (CRDM) units are mounted on top of the PDP, but the PDP is incapable of supporting the weight of the CRDM units and instead transfers the load to a support plate. The PDP has receptacles which receive cable modules each including mineral insulated (MI) cables, the MI cables being connected with the CRDM units. The PDP may further include a set of hydraulic lines underlying the cable modules and connected with the CRDM units. The cable modules in their receptacles define conduits or raceways for their MI cables and for any underlying hydraulic lines.

A housing assembly configured to house a reactor is disclosed. The housing assembly includes a plurality of modular walls configured to surround the reactor and a passive temperature control system. The plurality of modular walls includes a first modular wall. The passive temperature control system is coupled to the first modular wall. The passive temperature control system is configured to transfer heat between the reactor and an area around the housing assembly.

A reactor pressure vessel includes a reactor pressure vessel body, a nozzle structure connected to the reactor pressure vessel body, a conduit structure connected to the nozzle structure, and a restraint device attached around a portion of the conduit structure. The restraint device includes collar parts that have cross sections corresponding to respective segments of a periphery of the portion of the conduit structure, brackets attached to the nozzle structure, and rods connecting the brackets to the collar parts. The collar parts are connected end-to-end to each other such that a cross section of the collar parts connected to each other corresponds to the periphery of the portion of the conduit structure. The collar parts are pinned to each other. The brackets spaced apart from each other around a periphery of the nozzle structure.

A housing assembly configured to house a reactor is disclosed. The housing assembly includes a plurality of modular walls configured to surround the reactor and a passive temperature control system. The plurality of modular walls includes a first modular wall. The passive temperature control system is coupled to the first modular wall. The passive temperature control system is configured to transfer heat between the reactor and an area around the housing assembly.