A method of fabricating metallic fuel from surplus plutonium may include combining plutonium oxide powder and uranium oxide powder to obtain a mixed powder with reduced proliferation potential. The mixed powder may be electroreduced in a bath of molten salt so as to convert the mixed powder to a first alloy. The first alloy may be pressed to remove a majority of the molten salt adhered to the first alloy to form a pressed alloy-salt mixture. The first alloy may be isolated from the salt by melting the pressed alloy-salt mixture. The first alloy may be further processed to fabricate a fuel rod. Accordingly, the metallic fuel produced may be used in a fast reactor system, such as a Power Reactor Innovative Small Module (PRISM).

A method of fabricating metallic fuel from surplus plutonium may include combining plutonium oxide powder and uranium oxide powder to obtain a mixed powder with reduced proliferation potential. The mixed powder may be electroreduced in a bath of molten salt so as to convert the mixed powder to a first alloy. The first alloy may be pressed to remove a majority of the molten salt adhered to the first alloy to form a pressed alloy-salt mixture. The first alloy may be isolated from the salt by melting the pressed alloy-salt mixture. The first alloy may be further processed to fabricate a fuel rod. Accordingly, the metallic fuel produced may be used in a fast reactor system, such as a Power Reactor Innovative Small Module (PRISM).

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.

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.

The method described herein uses a ceramic precursors and controlled temperature rises for forming a stiffened ceramic composite fiber matrix to form a ceramic composite fuel cladding tube of the desired geometry and for removing a mandrel about which the composite fiber matrix was formed. The method described herein allows the manufacture of elongated ceramic composite claddings where the mandrel used to define the geometry of the cladding is easily removed without damaging the ceramic composite cladding. The method includes covering ceramic fibers with a mixture comprising at least one precursor of a ceramic material, wrapping the precursor covered fibers around a mandrel, heating the precursor covered fibers to the decomposition temperature of the precursor to convert the precursor to the ceramic material, and heating the mandrel to at least the melting point thereof to remove the mandrel.

The method described herein uses a ceramic precursors and controlled temperature rises for forming a stiffened ceramic composite fiber matrix to form a ceramic composite fuel cladding tube of the desired geometry and for removing a mandrel about which the composite fiber matrix was formed. The method described herein allows the manufacture of elongated ceramic composite claddings where the mandrel used to define the geometry of the cladding is easily removed without damaging the ceramic composite cladding. The method includes covering ceramic fibers with a mixture comprising at least one precursor of a ceramic material, wrapping the precursor covered fibers around a mandrel, heating the precursor covered fibers to the decomposition temperature of the precursor to convert the precursor to the ceramic material, and heating the mandrel to at least the melting point thereof to remove the mandrel.

This invention provides a nuclear reactor design that can enable automated or semi-automated manufacturing of a small reactor in a mechanized factory. This is possible by following a layered approach to combine simple plate geometries with the use of diffusion bonding and computer aided manufacturing techniques that integrate all the fuel, axial reflectors, axial gamma and neutron shields, fuel gas plenum, heat removal mechanism, primary heat exchangers and moderator all in one block or component. The final assembled block has no welds and limits or eliminates manual operations. This design has the potential to reduce the fabrication time of an entire nuclear reactor to just a few days.

A method for preparing a UO.sub.2 mixture powder for nuclear fuel manufacturing, comprises the steps of: (a) weighing and sieving, by means of an automatic injection device, a UO.sub.2 powder, a porogen and a lubricant, and injecting same into a UC container; and (b) mixing the UO.sub.2 powder, the porogen and the lubricant by means of an IBC blender. According to a method for preparing a UO.sub.2 mixture powder for nuclear fuel manufacturing, mixing time is short, and degrees of mixing and homogeneity of a prepared UO.sub.2 mixture powder are excellent.

A method for preparing a UO.sub.2 mixture powder for nuclear fuel manufacturing, comprises the steps of: (a) weighing and sieving, by means of an automatic injection device, a UO.sub.2 powder, a porogen and a lubricant, and injecting same into a UC container; and (b) mixing the UO.sub.2 powder, the porogen and the lubricant by means of an IBC blender. According to a method for preparing a UO.sub.2 mixture powder for nuclear fuel manufacturing, mixing time is short, and degrees of mixing and homogeneity of a prepared UO.sub.2 mixture powder are excellent.

A layer protecting the surface of zirconium alloys used as materials for nuclear reactors is formed by a homogenous polycrystalline diamond layer prepared by chemical vapor deposition method. This diamond layer is 100 nm to 50 m thick and the size of the crystalline cores in the layer ranges from 10 nm to 500 nm. Maximum content of non-diamond carbon is 25 mol %, total content of non-carbon impurities is maximum up to 0.5 mol %, RMS surface roughness of the polycrystalline diamond layer has a value less than 40 nm and thermal conductivity of the layer ranges from 1000 to 1900 Wm.sup.1K.sup.1. Coating of the zirconium alloys surface with the described polycrystalline diamond layer serves as a zirconium alloys surface protection against undesirable changes and processes in the nuclear reactor environment.