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.

A treatment process for a zirconium alloy is provided. The process includes the following steps: a zirconium alloy ingot is prepared, the composition of which is: 0.40%Nb1.05%; tracesSn2%; (0.5Nb0.25) %Fe0.50%; tracesNi0.10%; traces(Cr+V) %0.50%; tracesS35 ppm; 600 ppmO2000 ppm, preferably 1200 ppmO1600 ppm; tracesSi120 ppm; tracesC150 ppm; the remaining being Zr and unavoidable impurities; the ingot undergoes at least one reheating and hot shaping step, and possibly a reheating and quenching step following a hot shaping step; optionally the hot-shaped ingot undergoes an annealing; the hot-shaped and possibly annealed ingot undergoes at least one cycle of cold rolling-annealing steps; the annealing of at least one of the cold rolling-annealing steps being performed at a temperature comprised between 600 C. and the lowest of either 700 C. or (71020Nb %) C., and the annealings of the other cold rolling-annealing steps, if any, being performed at a temperature not higher than 600 C. Also provided are a Zr alloy so obtained, and part of a fuel assembly for a light water nuclear reactor made of it.

A treatment process for a zirconium alloy is provided. The process includes the following steps: a zirconium alloy ingot is prepared, the composition of which is: 0.40%Nb1.05%; tracesSn2%; (0.5Nb0.25) %Fe0.50%; tracesNi0.10%; traces(Cr+V) %0.50%; tracesS35 ppm; 600 ppmO2000 ppm, preferably 1200 ppmO1600 ppm; tracesSi120 ppm; tracesC150 ppm; the remaining being Zr and unavoidable impurities; the ingot undergoes at least one reheating and hot shaping step, and possibly a reheating and quenching step following a hot shaping step; optionally the hot-shaped ingot undergoes an annealing; the hot-shaped and possibly annealed ingot undergoes at least one cycle of cold rolling-annealing steps; the annealing of at least one of the cold rolling-annealing steps being performed at a temperature comprised between 600 C. and the lowest of either 700 C. or (71020Nb %) C., and the annealings of the other cold rolling-annealing steps, if any, being performed at a temperature not higher than 600 C. Also provided are a Zr alloy so obtained, and part of a fuel assembly for a light water nuclear reactor made of it.

A method for determining positions of elements of fuel assemblies arranged in a nuclear vessel is described herein. According to an implementation, the method involves capturing a plurality of images of a nuclear vessel and using the plurality of images to estimate a first set of positions of S-holes of a fuel assembly of the nuclear vessel. The method further involves determining a value representative of differences between: (a) the distances from the estimated set of positions to a location on a face of the fuel assembly and (b) known actual distances between the S-holes and the location on the face of the fuel assembly.

A method for determining positions of elements of fuel assemblies arranged in a nuclear vessel is described herein. According to an implementation, the method involves capturing a plurality of images of a nuclear vessel and using the plurality of images to estimate a first set of positions of S-holes of a fuel assembly of the nuclear vessel. The method further involves determining a value representative of differences between: (a) the distances from the estimated set of positions to a location on a face of the fuel assembly and (b) known actual distances between the S-holes and the location on the face of the fuel assembly.

A nuclear fuel assembly for a nuclear reactor core including at least one fuel cartridge having a lattice structure including an outer wall defining an interior volume, at least one flow channel extending through the interior volume of the lattice structure, at least one lattice site disposed in the interior of the lattice structure; and at least one fuel compact disposed within a corresponding one of the at least one lattice site. A cross-sectional shape of the at least one fuel compact is the same as a cross-sectional shape of the corresponding one of the at least one lattice site.

According to an embodiment, a design method for a light-water reactor fuel assembly comprises: accumulating a determined fuel data, showing that each of a combination of p.Math.n/N and e is feasible as the core or not, wherein N is a number of the fuel rods in the fuel assembly, n is a number of the fuel rods containing the burnable poison, p is a ratio wt % of the burnable poison in the fuel, and e is an enrichment wt % of the uranium 235 contained in the fuel assembly; formulating a criterion formula which determines whether a combination of p.Math.n/N and e is feasible as a core or not and is formulated based on the determined fuel data; and determining whether a temporarily set composition of the fuel assembly is approved as a core or not based on the criterion formula.

According to an embodiment, a design method for a light-water reactor fuel assembly comprises: accumulating a determined fuel data, showing that each of a combination of p.Math.n/N and e is feasible as the core or not, wherein N is a number of the fuel rods in the fuel assembly, n is a number of the fuel rods containing the burnable poison, p is a ratio wt % of the burnable poison in the fuel, and e is an enrichment wt % of the uranium 235 contained in the fuel assembly; formulating a criterion formula which determines whether a combination of p.Math.n/N and e is feasible as a core or not and is formulated based on the determined fuel data; and determining whether a temporarily set composition of the fuel assembly is approved as a core or not based on the criterion formula.

A fuel rod for a nuclear fission reactor is disclosed and claimed. The fuel rod includes an elongate hollow cladding configured to retain a nuclear fuel therein. The cladding includes an elongate hollow tube. Fiber layers are positioned around the outside surface of the tube or within the tube forming an integral part thereof. Both the tube and the fibers are formed of a ceramic material. A fuel assembly including a plurality of such fuel rods is also disclosed and claimed.

A portable nuclear fuel cartridge comprising a unitary support structure and a plurality of nuclear fuel assemblies that collectively form a nuclear fuel core. The nuclear fuel core is integrated into the unitary support structure to collectively form a self-supporting assemblage than can be lifted as a single unit. In another aspect, the invention is a method of fueling and/or defueling a nuclear reactor utilizing a nuclear fuel cartridge that is loaded and/or unloaded from the nuclear reactor as a single unit. In another aspect, a nuclear reactor core is provided that comprises a nuclear fuel core comprising: a plurality of first nuclear fuel assemblies, each of the plurality of first nuclear fuel assemblies having a first transverse cross-sectional configuration; and a plurality of second nuclear fuel assemblies, each of the plurality of second nuclear fuel assemblies having a second transverse cross-sectional configuration that is different than the first transverse cross-sectional configuration.