The present invention concerns a fuel assembly for a nuclear power boiling water reactor. The fuel assembly comprises fuel rods. At least 95% of the fuel rods comprise nuclear fuel material in the form of U enriched in 235U. At least 20% of the fuel rods belong to a first set of fuel rods. The fuel rods in this first set comprise both U enriched in 235U and Th. The first set comprises a first and a second subset of fuel rods. The ratio, with regard to weight, between Th and U, in each fuel rod of said first subset, is higher than the ratio, with regard to weight, between Th and U, in each fuel rod of said second subset. The invention also concerns a nuclear power boiling water reactor and a manner of operating such a reactor.

Disclosed are a sintered nuclear fuel pellet, a fuel rod, a fuel assembly and a method of manufacturing the nuclear fuel pellet. The pellet comprises a matrix of UO.sub.2 and particles dispersed in the matrix. The particles comprises a uranium-containing material. Each of the particles is encapsulated by a metallic coating. The uranium-containing material has a uranium density that is higher than the uranium density of UO.sub.2. The metallic coating consists of at least one metal chosen from the group of Mo, W, Cr, V and Nb.

The application discloses a preparation method of monocrystal uranium dioxide nuclear fuel pellets, comprising: granulating and pelleting UO.sub.2 powder to obtain UO.sub.2 pellets; then coating surfaces of the UO.sub.2 pellets with monocrystal growth additive micro powder to form core-shell structure particles; and activated-sintering the core-shell structure particles at high temperature, liquefying the monocrystal growth additive on the surface of the core-shell structure particle at high temperature and then diffusing into UO.sub.2 pellets, dissolving the UO.sub.3 in the liquid monocrystal growth additive, and recrystallizing the UO.sub.2 to form the monocrystal UO.sub.2 nuclear fuel pellets.

An improved nuclear fuel that has enhanced oxidation resistance and a process for making it are disclosed. The fuel comprises a composite of U235 enriched U.sub.3Si.sub.2 particles and an amount less than 30% by weight of UO.sub.2 particles positioned along the surface of the U.sub.3Si.sub.2 particles. The composite may be compressed into a pellet form. The process comprises forming a layer of UO.sub.2 on the surface of U.sub.3Si.sub.2 particles, either by exposing U.sub.3Si.sub.2 particles to an atmosphere of up to 15% oxygen by volume dispersed in an inert gas for a period of time and at a temperature sufficient to form UO.sub.2 at the U.sub.3Si.sub.2 particle surface, or by mixing U.sub.3Si.sub.2 particles with an amount up to 30% by weight of UO.sub.2 particles.

A method of forming one or more structures by additive manufacturing comprises introducing a first layer of a powder mixture comprising graphite and a fuel on a surface of a substrate. The first layer is at least partially compacted and then exposed to laser radiation to form a first layer of material comprising the fuel dispersed within a graphite matrix material. At least a second layer of the powder mixture is provided over the first layer of material and exposed to laser radiation to form inter-granular bonds between the second layer and the first layer. Related structures and methods of forming one or more structures are also disclosed.

Embodiments of the disclosure relate to a treatment method and a treatment apparatus for a UF.sub.6 heel, using a gas phase reaction. A specific treatment method includes (1) vaporizing the UF.sub.6 heel, (2) manufacturing solid phase UO.sub.2F.sub.2 by using UF.sub.6 gas vaporized at step (1), (3) separating the solid phase UO.sub.2F.sub.2 and by-product gas from each other, and (4) separating hydrogen fluoride from the by-product gas. According to the disclosure, stabilization of a reconversion process and the quality of UO.sub.2 powder may be improved by manufacturing the solid phase UO.sub.2F.sub.2, which is an intermediate of the UO.sub.2 powder, through the UF.sub.6 heel treatment, and the high cost of radioactive waste disposal is reduced by minimizing the UF.sub.6 heel to be less than 0.5 kg.

The invention is related to nuclear technologies, in particular, to the technology of producing nuclear oxide fuel for fuel elements, this oxide fuel can be used for manufacturing palletized nuclear fuel from uranium dioxide to be consumed by NPPs. The essence of the invention: this method of producing palletized nuclear fuel from uranium dioxide involves preparation of uranium dioxide moulding powder with/without uranium oxide, at this point powdered uranium dioxide is used as a raw material for preparation of moulding powder. Powdered uranium dioxide should be in the following proportion: O/U=2.370.04, it is obtained using a renowned methodby air heating of powdered uranium dioxide (ceramic grade) with the following proportion O/U=2.012.15. The technical result of the invention is increased mechanical strength of sintered pellets and a larger grain size of sintered pellets. 3 appendices, 1 diagram, 2 figures

A modular nuclear reactor comprises a plurality of sections arranged in a pattern and a side reflector material surrounding the plurality of sections. Each section includes a tank comprising a front plate, a back plate, side plates, a top plate, and a bottom plate. A plurality of grid plates are located within the tank. Each grid plate comprises a plurality of apertures and is vertically separated from an adjacent grid plate. The tank further includes a plurality of fuel elements extending through each grid plate. A plurality of heat pipes extend through each grid plate, the top plate, and an upper reflector. Methods of forming the modular nuclear reactor are also disclosed.

A method of forming a fuel rod for a nuclear reactor comprises disposing a powder comprising particles of a fuel material on a substrate, exposing the powder to energy from an energy source to form a first layer of a nuclear fuel, the first layer comprising inter-granular bonds between the particles of the fuel material, disposing additional powder comprising particles of the fuel material over the first layer of the nuclear fuel, and exposing the additional powder to energy from the energy source to form a second layer of the nuclear fuel and to form the nuclear fuel to have a void fraction greater than about 0.20, the second layer comprising inter-granular bonds between the additional powder and the first layer of the nuclear fuel. Related nuclear fuels comprising a porous structure, fuel rods, nuclear reactors, and methods are 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.