The fuel assembly includes at least one fuel rod and an outer channel with four sidewalls surrounding the fuel rod, the outer channel having a configuration based on a position of the fuel assembly within a core of the nuclear reactor, wherein at least a first select sidewall, of the four sidewalls of the outer channel, is a reinforced sidewall, the remaining sidewalls of the outer channel, other than the at least a first select sidewall, are non-reinforced sidewalls, the at least a first select sidewall being in a controlled location that faces and is directly adjacent to a control blade that is to be utilized in the nuclear reactor, wherein an entirety of the reinforced sidewall as a whole is at least one of thicker and made from a material that is more resistant to radiation-induced deformation as compared to an entirety of the non-reinforced sidewalls.

Carbide-based fuel assembly includes outer structural member of ceramic matrix composite material, the interior surface of which is lined in higher temperature regions with an insulation layer of porous refractory ceramic material. Continuous insulation layer extends the length of the fuel assembly or separate insulation layer sections have a thickness increasing step-wise along the length of the fuel assembly from upper (inlet) section towards bottom (outlet) section. A fuel element positioned inward of the insulation layer and between support meshes has a fuel composition including HALEU and the form of a plurality of individual elongated fuel bodies or one or more fuel monolith bodies containing coolant flow channels. Fuel assemblies are distributively arranged in a moderator block, with upper end of the outer structural member attached to an inlet for propellant and lower end of the outer structural member operatively interfaced with a nozzle forming a nuclear thermal propulsion reactor.

A fuel assembly for a pressure-tube nuclear reactor includes a fuel channel assembly. The fuel channel assembly has an outer conduit and an inner conduit received within the outer conduit. The conduits define an annular fuel bundle chamber for receiving a flow of a coolant in one direction. The inner conduit includes a central flow passage for receiving a flow of the coolant in an opposite direction. A fuel bundle positioned within the fuel bundle chamber consists of fuel elements arranged to form an inner ring surrounding the inner conduit, and an outer ring surrounding the inner ring. The coolant may be light water, and geometries of the fuel assembly may be selected so moderation by the volume of coolant promotes generally uniform power distribution in the fuel elements.

A fuel assembly for a pressure-tube nuclear reactor includes a fuel channel assembly. The fuel channel assembly has an outer conduit and an inner conduit received within the outer conduit. The conduits define an annular fuel bundle chamber for receiving a flow of a coolant in one direction. The inner conduit includes a central flow passage for receiving a flow of the coolant in an opposite direction. A fuel bundle positioned within the fuel bundle chamber consists of fuel elements arranged to form an inner ring surrounding the inner conduit, and an outer ring surrounding the inner ring. The coolant may be light water, and geometries of the fuel assembly may be selected so moderation by the volume of coolant promotes generally uniform power distribution in the fuel elements.

Carbide-based fuel assembly includes outer structural member of ceramic matrix composite material, the interior surface of which is lined in higher temperature regions with an insulation layer of porous refractory ceramic material. A continuous insulation layer extends the length of the fuel assembly or separate insulation layer sections have a thickness increasing step-wise along the length of the fuel assembly from upper (inlet) section towards bottom (outlet) section. Fuel element positioned inward of the insulation layer and between support meshes has a fuel composition including HALEU and the form of a plurality of individual elongated fuel bodies or one or more fuel monolith bodies containing coolant flow channels. Fuel assemblies are distributively arranged in a moderator block, with upper end of the outer structural member attached to an inlet for propellant and lower end of the outer structural member operatively interfaced with a nozzle forming a nuclear thermal propulsion reactor.

A method for the manufacture of a three-dimensional object using a refractory matrix material is provided. The method includes the additive manufacture of a green body from a powder-based refractory matrix material followed by densification via chemical vapor infiltration (CVI). The refractory matrix material can be a refractory ceramic (e.g., silicon carbide, zirconium carbide, or graphite) or a refractory metal (e.g., molybdenum or tungsten). In one embodiment, the matrix material is deposited according to a binder-jet printing process to produce a green body having a complex geometry. The CVI process increases its density, provides a hermetic seal, and yields an object with mechanical integrity. The residual binder content dissociates and is removed from the green body prior to the start of the CVI process as temperatures increase in the CVI reactor. The CVI process selective deposits a fully dense coating on all internal and external surfaces of the finished object.

A method for the manufacture of a three-dimensional object using a refractory matrix material is provided. The method includes the additive manufacture of a green body from a powder-based refractory matrix material followed by densification via chemical vapor infiltration (CVI). The refractory matrix material can be a refractory ceramic (e.g., silicon carbide, zirconium carbide, or graphite) or a refractory metal (e.g., molybdenum or tungsten). In one embodiment, the matrix material is deposited according to a binder-jet printing process to produce a green body having a complex geometry. The CVI process increases its density, provides a hermetic seal, and yields an object with mechanical integrity. The residual binder content dissociates and is removed from the green body prior to the start of the CVI process as temperatures increase in the CVI reactor. The CVI process selective deposits a fully dense coating on all internal and external surfaces of the finished object.

A channel box has a hollow cylindrical portion and accommodates a plurality of nuclear reactor fuel rods inside the hollow cylindrical portion, wherein the hollow cylindrical portion is constituted by a plurality types of silicon carbide composite materials. The channel box has a shape that can be achieved by applying the silicon carbide composite material and can increase earthquake resistance and improve functions and performance as a fuel assembly.

A channel box has a hollow cylindrical portion and accommodates a plurality of nuclear reactor fuel rods inside the hollow cylindrical portion, wherein the hollow cylindrical portion is constituted by a plurality types of silicon carbide composite materials. The channel box has a shape that can be achieved by applying the silicon carbide composite material and can increase earthquake resistance and improve functions and performance as a fuel assembly.

Disclosed embodiments include fuel ducts, fuel assemblies, methods of making fuel ducts, methods of making a fuel assembly, and methods of using a fuel assembly. An inner hollow structure has a first geometry and an outer hollow structure has a second geometry different from the first geometry. The first hollow structure is configured to expand in at least one dimension under stress and cause the first hollow structure to contact the second hollow structure. The second hollow structure distributes at least a portion of the stress of the first hollow structure.