Methods for forming particulates that are highly consistent with regard to shape, size, and content are described. Particulates are suitable for use as reference materials. Methods can incorporate actinides and/or lanthanides, e.g., uranium, and can be used for forming certified reference materials for use in the nuclear industry. Methods include formation of an aerosol from an oxalate salt solution, in-line diagnostics, and collection of particles of the aerosol either in a liquid impinger or on a solid surface.

Carbide-based fuel assembly includes outer structural member of ceramic matrix composite material (e.g., SiC—SiC composite), insulation layer of porous refractory ceramic material (e.g., zirconium carbide with open-cell foam structure or fibrous zirconium carbide), and interior structural member of refractory ceramic-graphite composite material (e.g., zirconium carbide-graphite or niobium carbide-graphite). Spacer structures between various layers provide a defined and controlled spacing relationship. A fuel element bundle positioned between support meshes includes a plurality of distributively arranged fuel elements or a solid, unitary fuel element with coolant channels, each having a fuel composition including high assay, low enriched uranium (HALEU). Fuel assemblies are distributively arranged in a moderator block and the upper end of the outer structural member is attached to a metallic inlet tube for hydrogen propellant and the lower end of the outer structural member is interfaced with a support plate, forming a nuclear thermal propulsion reactor.

Nuclear fuel structures and methods for fabricating are disclosed herein. The nuclear fuel structure includes a plurality of fibers arranged in the structure and a multilayer fuel region within at least one fiber of the plurality of fibers. The multilayer fuel region includes an inner layer region made of a nuclear fuel material, and an outer layer region encasing the nuclear fuel material. A plurality of discrete multilayer fuel regions may be formed over a core region along the at least one fiber, the plurality of discrete multilayer fuel regions having a respective inner layer region of nuclear fuel material and a respective outer layer region encasing the nuclear fuel material. The plurality of fibers may be wrapped around an inner rod or tube structure or inside an outer tube structure of the nuclear fuel structure, providing both structural support and the nuclear fuel material of the nuclear fuel structure.

The present invention relates to a method for preparing a fully ceramic capsulated nuclear fuel material containing three-layer-structured isotropic nuclear fuel particles coated with a ceramic having a composition which has a higher shrinkage than a matrix in order to prevent cracking of ceramic nuclear fuel, wherein the three-layer-structured nuclear fuel particles before coating is included in the range of between 5 and 40 fractions by volume based on after sintering. More specifically, the present invention provides a composition for preparing a fully ceramic capsulated nuclear fuel containing three-layer-structured isotropic particles coated with the substance which includes, as a main ingredient, a silicon carbine derived from a precursor of the silicon carbide wherein a condition of ΔL.sub.c>ΔL.sub.m at normal pressure sintering is created, where the sintering shrinkage of the coating layer of the three-layer-structured isotropic nuclear fuel particles is ΔL.sub.c and the sintering shrinkage of the silicon carbide matrix is ΔL.sub.m; material produced therefrom; and a method for manufacturing the material. The residual porosity of the fully ceramic capsulated nuclear fuel material is 4% or less.

The present invention relates to a method for preparing a fully ceramic capsulated nuclear fuel material containing three-layer-structured isotropic nuclear fuel particles coated with a ceramic having a composition which has a higher shrinkage than a matrix in order to prevent cracking of ceramic nuclear fuel, wherein the three-layer-structured nuclear fuel particles before coating is included in the range of between 5 and 40 fractions by volume based on after sintering. More specifically, the present invention provides a composition for preparing a fully ceramic capsulated nuclear fuel containing three-layer-structured isotropic particles coated with the substance which includes, as a main ingredient, a silicon carbine derived from a precursor of the silicon carbide wherein a condition of ΔL.sub.c>ΔL.sub.m at normal pressure sintering is created, where the sintering shrinkage of the coating layer of the three-layer-structured isotropic nuclear fuel particles is ΔL.sub.c and the sintering shrinkage of the silicon carbide matrix is ΔL.sub.m; material produced therefrom; and a method for manufacturing the material. The residual porosity of the fully ceramic capsulated nuclear fuel material is 4% or less.

A method for preparing a powder comprising an intimate mixture of U.sub.3O.sub.8 particles and PuO.sub.2 particles and which may further comprise particles of ThO.sub.2 or NpO.sub.2. The method comprises: preparing, via oxalic precipitations, an aqueous suspension S.sub.1 of particles of uranium(IV) oxalate and an aqueous suspension S.sub.2 of particles of plutonium(IV) oxalate; mixing the aqueous suspension S.sub.1 with the aqueous suspension S.sub.2 to obtain an aqueous suspension S.sub.1+2; separating the aqueous suspension S.sub.1+2 into an aqueous phase and a solid phase comprising the particles of uranium(IV) oxalate and the particles of plutonium(IV) oxalate; and calcining the solid phase to convert (1) the particles of uranium(IV) oxalate to particles of triuranium octoxide and (2) the particles of plutonium(IV) oxalate to particles of plutonium(IV) dioxide, whereby the powder is obtained.

Composite structures are provided whose composite matrix is a fully-dense (greater than 95%) magnesium oxide-containing phase and whose entrained phase, by virtue of its' decomposition temperature or chemical reactivity, would otherwise not be fabricable. Notably, a methodology is provided whereby a range of composite structures are formed by applying an advanced manufacturing technique and a blend of ceramic powder whose sintering is enhanced by small amounts of a metal halide sintering aid. This methodology and process significantly lowers the processing temperature of refractory ceramics such as magnesium oxide allowing formation of ceramic bodies incorporating phases such as metal hydrides, fragile ceramic phases, and highly reactive species such as beryllides. In all cases, the final product is substantially-free, or even devoid, of the metal halide sintering aid, resulting in a phase-pure ceramic matrix composed of the host phase and the entrained phase.

The invention relates to the field of nuclear technologies, in particular to an oxide-based uranium-plutonium nuclear fuel for an atomic power station with thermal neutron reactors. The technical result of the invention is the development of a REMIX-type fuel composition formulation making it possible, in the nuclear fuel cycle, to involve fissile nuclear materials regenerated from spent nuclear fuel with the simultaneous use of enriched natural uranium, and also moreover providing a solution to the problems of separately using previously isolated plutonium (including weapons-grade plutonium), of reducing the quantity of spent nuclear fuel by recycling fissile materials from spent nuclear fuel during the lifespan of a nuclear reactor (up to 5 recyclings), of economizing on natural uranium for manufacturing fuel and, as a result, of making the nuclear fuel cycle self-sustainable. The invention makes it possible to use REMIX fuel for solving an entire range of problems which a closed nuclear fuel cycle may face, taking into account the number of reactors, availability of natural uranium and the amount of stored spent nuclear fuel.

A nuclear fuel element includes a core comprising a fissile element and an additional element. A protective structure surrounds the core and comprises at least a first material surrounding the nuclear fuel. The first material comprises the fissile element and the additional element and comprises a greater than stoichiometric amount of the additional element. An outer portion of the nuclear fuel element comprises a metal. Related nuclear fuel elements, and related methods are also disclosed.

Disclosed are a nuclear fuel pellet having enhanced thermal conductivity and a method of manufacturing the same, the method including (a) a step of manufacturing a mixture including a nuclear fuel oxide powder and a thermally conductive plate-shaped metal powder; and (b) a step of molding and then heat-treating the thermally conductive plate-shaped metal powder to have an orientation in a horizontal direction in the mixture, thereby forming a pellet.