Abstract: Nuclear propulsion fission reactor structure has an active core region including fuel element structures, a reflector with rotatable neutron absorber structures (such as drum absorbers), and a core former conformal mating the outer surface of the fuel element structures to the reflector. Fuel element structures are arranged abutting nearest neighbor fuel element structures in a tri-pitch design. Cladding bodies defining coolant channels are inserted into and joined to lower and upper core plates to from a continuous structure that is a first portion of the containment structure. The body of the fuel element has a structure with a shape corresponding to a mathematically-based periodic solid, such as a triply periodic minimal surface (TPMS) in a gyroid structure. The nuclear propulsion fission reactor structure can be incorporated into a nuclear thermal propulsion engine for propulsion applications, such as space propulsion.

Abstract: A method of mass producing nuclear fuel elements may include: forming a graphite base portion of the fuel elements; repeatedly performing a sequence of operations comprising depositing a uniform graphite layer over a previous layer, depositing a layer of particles on the uniform graphite layer within a fuel zone diameter, so that the particles are spaced apart in a predefined pattern, and applying a binder using additive manufacturing methods to bind each layer with successively increasing and then decreasing diameters to form a central portion of fuel elements including a fuel-containing fuel zone; and repeatedly performing a sequence of operations comprising forming a uniform graphite layer on a previous layer and applying a binder using additive manufacturing methods to bind each layer with successively decreasing diameters to form a cap portion of fuel elements. The particles may include one or more of a nuclear fuel material, burnable poison material, or breeder material.

Abstract: An isotope production target rod for a power generating nuclear reactor is provided. The isotope production target rod can include at least one rod central body including an outer shell that defines an internal cavity and a plurality of irradiation targets within the internal cavity. The irradiation targets can be positioned in a spatial arrangement utilizing a low nuclear cross-section separating medium to maintain the spatial arrangement.

Abstract: A nuclear fuel composition includes a nuclear fissile material and a neutron-absorption material that adjoins the nuclear fissile material. The nuclear fuel composition may be used in a nuclear reactor, such as a thermal reactor.

Abstract: A compressed powder composite (CPC) material for absorbing neutrons emitted from spent nuclear fuel thereby preventing the initiation of a chain reaction. The CPC material is typically provided as a substantially insoluble cylindrical pellet that is highly resistant to corrosion and is not subject to the failure modes associated with the alloy materials typically used in neutron absorption materials. The pellet preferably includes a dendritic nickel powder substantially uniformly mixed with a neutron absorber powder material, preferably boron carbide. Tubes filled with CPC materials, such tubes for replacing control roads so that a spent nuclear fuel assembly may be disposed of substantially indefinitely.

Abstract: A nuclear fuel composition includes a nuclear fissile material and a neutron-absorption material that adjoins the nuclear fissile material. The nuclear fuel composition may be used in a nuclear reactor, such as a thermal reactor.

Abstract: A nuclear fuel composition includes a transuranic fuel and a neutron moderator mixed with transuranic fuel. The neutron moderator includes at least one of hafnium or zirconium.

Abstract: A nuclear fuel composition includes a transuranic fuel and a neutron moderator mixed with transuranic fuel. The neutron moderator includes at least one of hafnium or zirconium.

Abstract: A fast reactor 1 controlled with a reflector comprises: a reactor vessel 7 accommodating therein a coolant 5; a reactor core 2 disposed in the reactor vessel 7 and immersed in the coolant 5; and a reflector 4 that vertically moves for adjusting leakage of neutrons generated from the reactor core 2 to control a reactivity of the reactor core 2, the reflector 4 including a neutron reflecting part 4a disposed on an outside of the reactor core 2 in a vertically movable manner, the neutron reflecting part 4a having a neutron reflecting ability higher than that of the coolant 5, and a cavity part 4b positioned above the neutron reflecting part 4a, the cavity part 4b having a neutron reflecting ability lower than that of the coolant 5. The neutron reflecting part 4a is formed of a plurality of metal plates 37 that are stacked on each other. Each of the metal plates 37 has a plurality of coolant channels 36 through which the coolant 5 flows.

Abstract: A core of a light water reactor having a plurality of fuel assemblies, which are loaded in said core, having nuclear fuel material containing a plurality of isotopes of transuranium nuclides, an upper blanket zone, a lower blanket zone, and a fissile zone, in which the transuranium nuclides are contained, disposed between the upper blanket zone and the lower blanket zone; wherein a ratio of Pu-239 in all the transuranium nuclides contained in the loaded fuel assembly is in a range of 40 to 60% when burnup of the fuel assembly is 0; sum of a height of the lower blanket zone and a height of the upper blanket zone is in a range of 250 to 600 mm; and the height of said lower blanket zone is in a range of 1.6 to 12 times the height of the upper blanket zone.

Abstract: The present invention provides a nuclear fuel assembly, where a boron-containing compound is used as a burnable poison and is distributed in a majority of the rods in the assembly. The assembly comprises a plurality of fuel rods, each fuel rod containing a plurality of nuclear fuel pellets, wherein at least one fuel pellet in more than 50% of the fuel rods in the fuel assembly comprises a sintered admixture of a metal oxide, metal carbide or metal nitride and a boron-containing compound.

Abstract: Aluminum powder, neutron absorber, and third particle composed of oxide, nitride, carbide or boride are mixed, and preformed by cold isostatic pressing (CIP). Successively, by canning the preformed material, this preformed material is sintered by hot isostatic pressing (HIP). After sintering, the can outside and end face are machined by grinding, and the billet is taken out. Square pipes are formed by extruding this billet.

Abstract: A new transmutation assembly permits an efficient transmutation of a long-lived radioactive material (long-lived FP nuclides such as technetium-99 or iodine-129) which was produced in the nuclear reactor. Wire-type members of a long-lived radioactive material comprised of metals, alloys or compounds including long-lived FP nuclides are surrounded by a moderator material and installed in cladding tubes to form FP pins. The FP pins, and nothing else, are housed in a wrapper tube to form a transmutation assembly. The wire-type members can be replaced by thin ring-type members. The transmutation assemblies can be selectively and at least partly loaded into a core region, a blanket region or a shield region of a reactor core in a fast reactor. From a viewpoint of reducing the influence on the reactor core characteristics, it is optimal to load the transmutation assemblies into the blanket region.

Abstract: In a fuel bundle for a boiling water nuclear reactor comprising a plurality of fuel rods (20) secured within an array and extending between upper and lower tie plates (24, 22), and including at least one additional partial length fuel rod (20') extending from said lower tie plate (22) but terminating short of said upper tie plate (24), an improvement in the form of a removable extension rod (32) secured to said at least one additional fuel rod (20') and extending substantially to said upper tie plate (24). The removable extension rod (32) also permits variance in the reactivity of the partial length fuel rod (20') particularly in the two phase region of the bundle (10).

Abstract: A nuclear propulsion reactor. A pressure vessel is provided with a reactor core that is surrounded by a radial reflector. Nuclear fuel elements in the core are formed from a hexagonal housing made from a high performance moderator and having a plurality of axial bores that extend the full length of the housing. A stack of nuclear fuel compacts having axial bores for coolant flow is received in the central axial bore of the housing. Hollow lithium hydride slugs are received in the bores at the corners of the housing. A rocket nozzle is attached to one end of the pressure vessel. Coolant/propellant flows into a passageway around the rocket nozzle for cooling thereof, upward through bores in the reflector and through the hexagonal housings of the fuel elements, downward through the bores in the nuclear fuel compacts and then out the rocket nozzle where propulsive thrust is produced.

Abstract: The present invention provides improved nuclear fuel pellets having high thermal conductivity for use in an LWR. This can be achieved by creating a continuous deposition phase of high-thermal conductivity substances in the grain boundaries in the pellets. As a result, the temperature in the center of the fuel rod can be significantly reduced, and the discharge amount of gases generated on the nuclear fission can be efficiently reduced.The present invention also provides a method of manufacturing the above-described nuclear fuel pellets.

Abstract: A core of a light-water reactor comprises a plurality of fuel assemblies each including a number of fuel rods. The fuel rod is provided with at least one area interposed between fuel areas in a clad of the fuel rod. The interposed area contains extremely reduced or substantially no fissile nuclide. At least two areas or layers with high enrichment of the fissile nuclide are formed in the axial direction of the reactor by the location of the interposed areas throughout the whole fuel assemblies arranged in the light-water reactor core.

Abstract: A fuel assembly for a boiling water nuclear reactor is provided comprising an elongated central water channel including wall members that define an enclosed fluid flow path therethrough, the channel includes a lower opening for receiving water and allowing water to flow through the fluid flow path and at least one outlet opening. At least one partial water rod is provided that is coupled to a partial fuel rod so as to be disposed axially above the partial fuel rod. The partial water rod includes an inlet opening in fluid communication with the outlet opening of the central water channel so as to allow water to flow from the water channel into an interior of the partial water rod.

Abstract: A fuel assembly including a channel box, upper and lower tie plates, fuel rods inserted in the channel box and held at upper and lower end portions by the upper and lower tie plates, a water rod disposed among the fuel rods and spacers for keeping the fuel rods and the water rod spaced from one another. The water rod has a diameter larger than that of each of the fuel rods and the upper end of the water rod has a height substantially as high as an upper end of an effective enriched fuel section of each fuel rod.

Abstract: A burnable, thermal neutron absorber element is provided with a zirconium alloy elongate container having sealed therein both a burnable absorber and the solid moderator material, zirconium hydride. The zirconium hydride is in a concentration and position to enhance the neutron capture efficiency of said thermal neutron absorber in a light water reactor neutron irradiation environment.

Abstract: A burnable poison rod for use in a nuclear reactor comprises a metallic tube with upper and lower closure means, a neutron absorber positioned within the cladding, and a neutron moderating spacer means positioning the neutron absorber in spaced relation to the lower closure means. The neutron moderating spacing means can comprise a solid neutron moderating material, or a liquid coolant moderator contained within the lower section of the cladding with a sealing plug positioned between the neutron absorber and the liquid coolant moderator.

Abstract: A segmented fuel and moderator rod and fuel assembly for a BWR. The segmented rod has a lower fuel region and an upper moderator region for passing coolant having a void fraction of between about 0-20% through the upper portion of the BWR core which is normally undermoderated. The segmented rod displaces one or more conventional fuel rods in the fuel bundle. A method of moderating a BWR core is also disclosed.

Abstract: The invention provides a fuel assembly comprising a plurality of fuel rods containing a fissionable material and a plurality of moderator rods filled with a burnable poison and a metal hydride as a solid moderator material. All of the burnable poison in the fuel assembly is filled in the moderator rods, and number of the moderator rods is at least 4 and not more than 15% of total number of the fuel rods and the moderator rods.

Abstract: A fuel bundle for a boiling water reactor contains a plurality of fuel rods, some of which contain a moderating material rather than nuclear fuel or contain nuclear fuel in the lower section of the fuel rod and moderating material in the upper section thereof, for improving both the axial and radial power shapes of the fuel bundle. The moderating material in the upper section of the fuel rods increases the neutron moderation in this section of the bundle, thereby compensating for the poor water moderation of the boiling water in this section, increasing the power generated in this section and flattening the axial power shape of the bundle. Fuel rods in the interior section of the bundle contain moderating material which also flattens the radial power shape. Caps containing moderating material are also placed on the upper end of each fuel rod in order to reflect neutrons thereby reducing the top axial fast-neutron leakage.

Abstract: A nuclear fuel includes uranium dispersed within a thorium hydride matrix. The uranium may be in the form of particles including fissile and non-fissile isotopes. Various hydrogen to thorium ratios may be included in the matrix. The matrix with the fissile dispersion may be used as a complete fuel for a metal hydride reactor or may be combined with other fuels.

Abstract: The production of a novel nuclear fuel utilizing clean uranium 233 in combination with other nuclear materials is made possible by utilization of an equally novel reactor configuration and method of operation. Clean uranium 233 is produced from thorium in a light water reactor while utilizing discrete separation of the thorium being irradiated from the fissile fuel. This clean uranium 233 is then incorporated directly as fissile isotope enrichment into a new nuclear fuel which may be done without encountering the usual difficulties and hazards in the handling of uranium 233 or the expense and delays associated with gaseous diffusion enrichment. The thorium from this process may be directly reprocessed for reactor charging without radiation hazard also.

Abstract: A fuel element for a high temperature gas cooled nuclear reactor which aims at reducing the temperature difference between the fuel center and the coolant has a reduced thickness of heat transfer path and means for eliminating discontinuities therein. The fuel element has flat plates each having a inner fuel bearing sheet of coated nuclear fuel particles dispersed in a carbonaceous matrix material clad by preformed relatively thin artefacts of unfuelled carbonaceous material which have been platen pressed on to the external surfaces of the fuel sheet while both the fuel sheet and the artefacts are in the green state.