A nuclear power system includes a reactor vessel that includes a reactor core that includes nuclear fuel assemblies configured to generate a nuclear fission reaction; a riser positioned above the reactor core; a primary coolant flow path that extends from a bottom portion of the volume through the reactor core and through an annulus between the riser and the reactor vessel; a primary coolant that circulates through the primary coolant flow path to receive heat from the nuclear fission reaction and release the heat to generate electric power in a power generation system; and a control rod assembly system positioned in the reactor vessel and configured to position control rods in only two discrete positions.

A nuclear power system includes a reactor vessel that includes a reactor core mounted therein. The reactor core includes nuclear fuel assemblies configured to generate a nuclear fission reaction. The reaction vessel does not include any control rod assemblies therein. The nuclear power system further includes a riser positioned above the reactor core, a primary coolant flow path, a primary coolant that circulates through the primary coolant flow path to receive heat from the nuclear fission reaction and release the received heat to generate electric power in a power generation, and a control system communicably coupled to the power generation system and configured to control a power output of the nuclear fission reaction independent of any control rod assemblies.

A nuclear power system includes a reactor vessel that includes a reactor core that includes nuclear fuel assemblies configured to generate a nuclear fission reaction. A representative nuclear power system further includes a riser positioned above the reactor core and a primary coolant flow path that extends from a bottom portion of the reactor vessel, through the reactor core, and through an annulus between the riser and the reactor vessel. A primary coolant circulates through the primary coolant flow path to receive heat from the nuclear fission reaction and release the heat to a power generation system configured to generate electric power. The nuclear power system further includes a control rod assembly system positioned in the reactor vessel and configured to position control rods in only two discrete positions.

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.

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.

A nuclear reactor is configured with a primary coolant loop for transferring heat away from the nuclear reactor core. In a shutdown event, the primary coolant pump may stop pumping primary coolant through the reactor core, resulting in decay heat buildup within the reactor core. An inertial energy coast down system can store kinetic energy while the nuclear reactor is operating and then release the stored kinetic energy to cause the primary coolant to continue to flow through the nuclear reactor core to remove decay heat. The inertial energy coast down system may include an impeller and a flywheel having a mass. During normal reactor operation, the flowing primary coolant spins up the impeller and flywheel, and upon a shutdown event where the primary coolant pump stops pumping, the flywheel and impeller can cause the primary coolant to continue to flow during a coast down of the flywheel and impeller.

The modular lower moving system for nuclear fuel handling includes: a lower reactor vessel assembly including nuclear fuel loaded therein; a carrier having a space allowing the lower reactor vessel assembly to be accommodated therein; a rail extending from a reactor area to a fuel handling area; a transfer cart horizontally movable along the rail; a lifting device installed at the transfer cart, movable upward or downward with respect to the transfer cart; and a drive device configured to supply power to the transfer cart and the lifting device. The method of refueling nuclear fuel using the modular lower moving system includes a carrier lifting process, a lower reactor vessel assembly detachment process, a process of accommodating the lower reactor vessel assembly in the carrier, a carrier lowering process, a transfer cart movement process, a nuclear fuel offloading process, and a nuclear fuel loading process.

Cover gas control systems include a reservoir and injection path for direct injection into fuel transfer machinery. If seals in the fuel handling machinery leak, cover gas is provided from the reservoir to flow to the leak without contamination from a reactor to which the fuel transfer machinery is joined. This providing cover gas may be passive or automatic in response to a detected low pressure level, detected ambient air ingress, low volume level of cover gas, or manually actuated through an operator. The cover gas may be injected from below the leak but above the reactor. A limitation in the injection path keeps cover gas injection at rates sufficient to allow operator reaction and sealing before the reservoir is depleted. A pressure pulse transmitter, blowout preventer, and transfer port plug are useable in the systems, which can be implemented in fuel handling machinery for reactors using a cover gas.

The application relates to nuclear technology for preparing fuel rods and fuel assemblies for the cores of fast-neutron reactors utilizing a liquid-metal coolant to reduce the amount of metal consumed per fuel rod. A fast-neutron reactor fuel rod having nuclear fuel disposed is in a sealed housing having a thin-walled tubular steel shell. A spacer element is wound in a coil with a large pitch on the outside surface of the shell and fastened to ends of the fuel rod on an end part of the housing. The spacer element is in the form of a metallic band twisted around its longitudinal axis, the width of the band being approximately equal to the minimum distance between adjacent fuel rods in a fuel assembly of the nuclear reactor, the cross-sectional area of the band within a range from 0.1 to 0.5 times the area of a circle described around the section.

The fuel element of the present invention includes a cladding tube and a metal fuel contained in the cladding tube, in which a gas plenum region is formed above the metal fuel and inside the cladding tube and has a small-diameter portion in the gas plenum region. Further, the fuel assembly of the present invention includes the fuel element of the present invention and a wrapper tube surrounding the fuel element, in which a coolant material passage is formed between the fuel element and the fuel element. Further, the core of the present invention includes an inner core fuel region loaded with the fuel assembly according to the present invention, and an outer core fuel region loaded with the fuel assembly of the present invention.