A passive nuclear reactor control device. The passive nuclear reactor control device comprises a sealed chamber, which comprises a reservoir and a tube in fluid communication with the reservoir. A molten salt is within the sealed chamber, the molten salt being a eutectic mixture of a monovalent metal halide, and a fluoride or chloride of one or more lanthanides and/or a luoride or chloride of hafnium. A gas is within the sealed chamber, and the gas does not react with the molten salt.

A passive nuclear reactor control device. The passive nuclear reactor control device comprises a sealed chamber, which comprises a reservoir and a tube in fluid communication with the reservoir. A molten salt is within the sealed chamber, the molten salt being a eutectic mixture of a monovalent metal halide, and a fluoride or chloride of one or more lanthanides and/or a luoride or chloride of hafnium. A gas is within the sealed chamber, and the gas does not react with the molten salt.

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.

The method includes configuring a nuclear reactor to at least partially mitigate liquid metal coolant backflow in the nuclear reactor in response to an at least partial failure of a primary electromagnetic pump (EMP) within a reactor pressure vessel of the nuclear reactor, the nuclear reactor being liquid metal-cooled, the primary EMP configured to circulate liquid metal coolant through at least a reactor core of the nuclear reactor, the configuring including, installing a backflow EMP within the reactor pressure vessel, such that when selectively activated, the backflow EMP at least partially mitigates liquid metal coolant backflow through the primary EMP.

The method includes configuring a nuclear reactor to at least partially mitigate liquid metal coolant backflow in the nuclear reactor in response to an at least partial failure of a primary electromagnetic pump (EMP) within a reactor pressure vessel of the nuclear reactor, the nuclear reactor being liquid metal-cooled, the primary EMP configured to circulate liquid metal coolant through at least a reactor core of the nuclear reactor, the configuring including, installing a backflow EMP within the reactor pressure vessel, such that when selectively activated, the backflow EMP at least partially mitigates liquid metal coolant backflow through the primary EMP.

A nuclear reactor is configured with an intermediate coolant loop for transferring thermal energy from the reactor core for a useful purpose. The intermediate coolant loop includes a bypass flowpath with an air heat exchanger for dumping reactor heat during startup and/or shutdown. A fluidic diode along the bypass flowpath asymmetrically restricts flow across the bypass flowpath, inhibiting flow in a first flow direction during a full power operating condition and allowing a relatively uninhibited flow in a second direction during a startup and/or shut down low power operating condition.

One or more embodiments of the present invention relate to a pump/heat exchanger assembly of a nuclear reactor, in particular a liquid metal cooled nuclear reactor, the pump being characterized in that the shaft for driving the impeller is inserted in an shell inside the heat exchanger and has a smaller cross section at the bottom part of the tube bundle of the heat exchanger and a cross section that gradually increases up to a widest cross section at the top part of the tube bundle of the heat exchanger. The resulting axial profile of the impeller's shaft is, at the same time, designed to uniformly distribute the flow of the primary fluid inside the tube bundle of the heat exchanger and to provide high mechanical inertia to the pump.

One or more embodiments of the present invention relate to a pump/heat exchanger assembly of a nuclear reactor, in particular a liquid metal cooled nuclear reactor, the pump being characterized in that the shaft for driving the impeller is inserted in an shell inside the heat exchanger and has a smaller cross section at the bottom part of the tube bundle of the heat exchanger and a cross section that gradually increases up to a widest cross section at the top part of the tube bundle of the heat exchanger. The resulting axial profile of the impeller's shaft is, at the same time, designed to uniformly distribute the flow of the primary fluid inside the tube bundle of the heat exchanger and to provide high mechanical inertia to the pump.

A printed circuit heat exchanger for use in a reactor includes a core formed from a stack of plates diffusion bonded together. The core has: a top face, a bottom face disposed opposite the top face, a first side face extending between the top face and the bottom face, and a second side face disposed opposite the first side face. The printed circuit heat exchanger includes: a plurality of primary channels defined in the core, each of the primary channels extending from a primary inlet defined in the first side face to a primary outlet defined in the second side face; and a plurality of secondary channels defined in the core, each of the secondary channels extending among at least some of the primary channels from a secondary inlet defined in the top face to a secondary outlet defined in the top face.

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.