Engineered surfaces, such as surfaces having nano- and/or micro-scale features, may provide an enhanced flow boiling Critical Heat Flux (CHF) at ambient or higher pressures, which may enhance cooling. Enhancing flow boiling CHF may be desirable for nuclear reactors, where heat is generated by a heater such as a nuclear reactor core. Enhanced flow boiling CHF may provide larger safety margins and/or better economics of nuclear reactors, for example, because reactor power rating may be increased as cooling is enhanced.

Nuclear fuel assemblies include fuel elements that are sintered or cast into billets and co-extruded into a spiral, multi-lobed shape. The fuel kernel may be a metal alloy of metal fuel material and a metal-non-fuel material, or ceramic fuel in a metal non-fuel matrix. The fuel elements may use more highly enriched fissile material while maintaining safe operating temperatures. Such fuel elements according to one or more embodiments may provide more power at a safer, lower temperature than possible with conventional uranium oxide fuel rods. The fuel assembly may also include a plurality of conventional UO.sub.2 fuel rods, which may help the fuel assembly to conform to the space requirements of conventional nuclear reactors.

Nuclear fuel assemblies include fuel elements that are sintered or cast into billets and co-extruded into a spiral, multi-lobed shape. The fuel kernel may be a metal alloy of metal fuel material and a metal-non-fuel material, or ceramic fuel in a metal non-fuel matrix. The fuel elements may use more highly enriched fissile material while maintaining safe operating temperatures. Such fuel elements according to one or more embodiments may provide more power at a safer, lower temperature than possible with conventional uranium oxide fuel rods. The fuel assembly may also include a plurality of conventional UO.sub.2 fuel rods, which may help the fuel assembly to conform to the space requirements of conventional nuclear reactors.

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.

A honeycomb-shaped fuel assembly cooled by liquid chloride salt adopts a honeycomb-shaped structure. A fuel coolant is a mixture of liquid three-phase chloride salt NaClKClMgCl.sub.2. Fuel is U.sub.3Si.sub.2 with an enrichment of 19.75% or 16.0%. The fuel assembly includes: fuel coolant channel pipelines which vertically penetrate and laterally merge, a fuel coolant contained in the fuel coolant channel pipelines, a fuel zone, upper and lower endcap, a top gas plenum, and upper and lower endcap. A reflector assembly adopts a honeycomb-shaped structure, including: reflector coolant pipes which are vertically penetrating; a reflector coolant contained in the reflector coolant pipes; a titanium reflector; and upper and lower endcaps. A control assembly and a safety assembly adopt a rod bundle structure using B.sub.4C with a natural enrichment of .sup.10B as absorbers.

A honeycomb-shaped fuel assembly cooled by liquid chloride salt adopts a honeycomb-shaped structure. A fuel coolant is a mixture of liquid three-phase chloride salt NaClKClMgCl.sub.2. Fuel is U.sub.3Si.sub.2 with an enrichment of 19.75% or 16.0%. The fuel assembly includes: fuel coolant channel pipelines which vertically penetrate and laterally merge, a fuel coolant contained in the fuel coolant channel pipelines, a fuel zone, upper and lower endcap, a top gas plenum, and upper and lower endcap. A reflector assembly adopts a honeycomb-shaped structure, including: reflector coolant pipes which are vertically penetrating; a reflector coolant contained in the reflector coolant pipes; a titanium reflector; and upper and lower endcaps. A control assembly and a safety assembly adopt a rod bundle structure using B.sub.4C with a natural enrichment of .sup.10B as absorbers.

Systems for controlling and protecting nuclear reactors. A drive of an emergency safety rod of a nuclear reactor includes an electric drive, a reduction gear, and a rack-and-pinion gear. The electric drive contains a contactless electric motor based on permanent magnets, which is installed in the housing of the electric drive with a motor rotor position sensor, and a reduction gear for changing the rate of rotation of the electric drive. A toothed rack is installed along the axis of the rack-and-pinion gear in order to provide for the reciprocating motion of a system absorber rod connected thereto. A toothed electromagnetic clutch having a contactless current supply is installed on an inner shaft of the rack-and-pinion gear, enabling the rigid and simultaneous mechanical coupling of half-couplings, and the drive contains a reverse-motion coupling, a rack-separation spring and toothed rack position sensors.

Systems for controlling and protecting nuclear reactors. A drive of an emergency safety rod of a nuclear reactor includes an electric drive, a reduction gear, and a rack-and-pinion gear. The electric drive contains a contactless electric motor based on permanent magnets, which is installed in the housing of the electric drive with a motor rotor position sensor, and a reduction gear for changing the rate of rotation of the electric drive. A toothed rack is installed along the axis of the rack-and-pinion gear in order to provide for the reciprocating motion of a system absorber rod connected thereto. A toothed electromagnetic clutch having a contactless current supply is installed on an inner shaft of the rack-and-pinion gear, enabling the rigid and simultaneous mechanical coupling of half-couplings, and the drive contains a reverse-motion coupling, a rack-separation spring and toothed rack position sensors.

A heat pipe fuel element includes an evaporation section, a condensing section, a capillary section connecting the evaporation section to the condensing section, and a primary coolant. In a cross-section in a plane perpendicular to a longitudinal axis of the evaporation section, the heat pipe fuel element includes a cladding layer enclosing an interior area including a fuel body formed of a fissionable fuel composition and that has an outer surface oriented toward the cladding layer and an inner surface defining a periphery of a vaporization space of the evaporation section. The fuel body has a structure with a shape corresponding to a mathematically-based periodic solid, such as a triply periodic minimal surface (TPMS), and the evaporation sections of a plurality of heat pipe fuel elements are arranged in a phyllotaxis pattern (as seen in a cross-section in a plane perpendicular to a longitudinal axis of the active core region).