Abstract: A method for manufacturing a nuclear fuel compact is provided. The method includes forming an additive structure, consolidating a fuel matrix around the additive structure, and thermally processing the fuel matrix to form a fuel compact in which the additive structure is encapsulated therein. The additive structure optionally includes a vertical segment and a plurality of arm segments that extend generally radially from the vertical segment for conducting heat outwardly toward an exterior of the fuel compact. In addition to improving heat transfer, the additive structure may function as burnable absorbers, and may provide fission product trapping.

Abstract: The present invention relates to a nuclear reactor, in particular a pool-type nuclear reactor cooled with liquid metal (for example, a heavy metal such as lead or lead-bismuth eutectic) or with sodium or molten salts, having a core formed by a bundle of fuel elements and immersed in a primary fluid circulating between the core and at least one heat exchanger; the fuel elements extend along respective parallel longitudinal axes and have respective bottom active parts immersed in the primary fluid to constitute the core, and respective service parts that extend at the top from the active parts and emerge from the primary fluid; the fuel elements are mechanically supported via respective top end heads anchored to supporting structures and can be operated via handling machines.

Abstract: A nuclear fuel assembly bottom nozzle, of the type including a perforated plate to allow water to pass through it, the nozzle having lateral faces, and at least one anti-debris element positioned on a lateral face to block out debris likely to infiltrate between the bottom nozzle and another adjacent bottom nozzle, characterized in that, in the free state, the or each anti-debris element permanently projects from the lateral face on which it is positioned, the or each anti-debris element being elastically deformable so as to retract towards the lateral face in the event of a force being exerted on the anti-debris element towards the lateral face.

Abstract: Fuel elements are supported by fuel assemblies configured for use in land-based nuclear reactors such as the VVER-1000. The fuel elements include a kernel having a multi-lobed profile that forms spiral ribs that include fissionable material (e.g., uranium or plutonium), a central metal displacer extending along a longitudinal axis of the kernel, and a metal cladding (e.g., zirconium and/or other refractory metals) enclosing the kernel. The fuel element may be fabricated by joint extrusion of the displacer, kernel, and cladding through a die to metallurgically bond the kernel and cladding.

Abstract: Example embodiments are directed to methods and apparatuses for generating desired isotopes within water rods of nuclear fuel assemblies. Example methods may include selecting a desired irradiation target based on the target's properties, loading the target into a target rod based on irradiation target and fuel assembly properties, exposing the target rod to neutron flux, and/or harvesting isotopes produced from the irradiation target from the target rod. Example embodiment target rods may house one or more irradiation targets of varying types and phases. Example embodiment securing devices include a ledge collar and/or bushing that support target rods within a water rod and permit moderator/coolant flow through the water rod. Other example embodiment securing devices include one or more washers with one or more apertures drilled therein to hold one or more example embodiment target rods in a water rod while permitting coolant/moderator to flow through the water rod.

Abstract: Example embodiments are directed to tiered tie plates and fuel bundles that use tiered tie plates. Example embodiment tie plates may include upper and lower tiered tie plates. Example embodiment tiered tie plates may have a plurality of bosses divided into groups, or tiers, having differing vertical (axial) displacement. Example embodiment fuel bundles may use tiered tie plates such that fuel rods in example bundles may originate and terminate at different vertical displacements, based upon the vertical displacement of the bosses receiving the fuel rods into the tiered tie plates. Optionally, shanks may be used to further vary fuel rod axial displacement and diameter.

Abstract: A fuel assembly is charged in a reactor core of a nuclear reactor using a liquid metal as a coolant, and includes a wrapper tube storing a plurality of fuel pins and including an entrance nozzle for introducing the coolant and an operation handling head, grids disposed in the wrapper tube to support the fuel pins in the radial direction of the wrapper tube, liner tubes inserted in the wrapper tube to fixedly hold the respective grids in the axial direction of the wrapper tube, and a fixing device for fixing the grids and the liner tubes in the radial direction of the wrapper tube.

Abstract: A fuel support for a nuclear reactor may include: a plurality of fuel support apertures, each fuel support aperture dimensioned for receiving a lower tie plate of a fuel assembly; and a plurality of lumens, each lumen being coupled to a different fuel support aperture. At least one lumen may be configured for attenuating a fluid flow differently than the fluid flow in at least one other of the lumen.

Abstract: A terminal end-piece for a fuel assembly of a pressurized water nuclear reactor, the assembly having fuel rods and a skeleton for supporting the fuel rods, the fuel rods extending in a longitudinal direction and being arranged at the nodes of a substantially regular network, the support skeleton comprising two terminal end-pieces and guide tubes that connect the terminal end-pieces, the fuel rods being arranged longitudinally between the terminal end-pieces, characterized in that the end-piece comprises noses for orientating the flow of a coolant fluid of the reactor along the adjacent longitudinal ends of the fuel rods, the noses being arranged in nodes of the substantially regular network in order to be positioned in a longitudinal continuation of at least some of the fuel rods and/or at least some of the guide tubes of the support skeleton.

Abstract: The present invention relates to a nuclear reactor, in particular a pool-type nuclear reactor cooled with liquid metal (for example, a heavy metal such as lead or lead-bismuth eutectic) or with sodium or molten salts, having a core formed by a bundle of fuel elements and immersed in a primary fluid circulating between the core and at least one heat exchanger; the fuel elements extend along respective parallel longitudinal axes and have respective bottom active parts immersed in the primary fluid to constitute the core, and respective service parts that extend at the top from the active parts and emerge from the primary fluid; the fuel elements are mechanically supported via respective top end heads anchored to supporting structures and can be operated via handling machines.

Abstract: A fuel channel for housing a fuel rod bundle in a boiling water nuclear reactor includes an expanded section to create an increased flow area at a top of the fuel channel and thereby reduce a pressure drop through the fuel channel. The expanded section eliminates a need for channel spacers and a fastener guard.

Abstract: A resilient bush for frictionally engaging a centering pin of the fuel assembly is fixed in each of the through-holes of at least one of the end-pieces of the fuel assembly. The resilient bush comprises an annular member which has a portion for fixing in the hole of the end-piece and resilient arms which are separated by apertures. The flexible arms of the resilient bush comprise, in a free end portion, a supporting surface which projects radially inside the bush whose diameter is smaller than the diameter of a centering pin of the fuel assembly.

Abstract: Fuel supports for a nuclear reactor and methods of modifying fluid flow in a reactor using a fuel support. The fuel supports include a plurality of lumens and a plurality of fuel support apertures with each fuel support aperture being dimensioned for receiving a lower tie plate of a fuel assembly. Each lumen is fluidly coupled to a different fuel support aperture. At least one lumen is configured for attenuating a fluid flow differently than the fluid flow in at least one other of the lumen.

Abstract: Assemblies and methods for mounting a fuel assembly in a nuclear reactor include a fuel assembly includes fuel rods within the fuel assembly and a lower tie plate with a fuel assembly mating fixture. A fuel support includes a fuel support mating fixture that is constructed to selectively engage the fuel assembly mating fixture during installation of the fuel assembly onto the fuel support. The fuel support mating fixture and the fuel assembly mating fixture provides for a predefined orientation of the fuel assembly to the fuel support upon mating.

Abstract: A fuel channel fastener having a body with a hole, a bolt inserted into the hole, at least two anti-rotation supports attached to the body, a spring configured to attach to the body and to extend away from the body down the sides of a fuel assembly fuel channel, and at least two spring anti-rotation pads connected to the body.

Abstract: A fuel element for a pressurized water reactor has fuel rods guided through a number of axially spaced spacers. The spacers form a square grid with mesh openings arranged in rows and columns. Support tubes that do not contain fuel pass through a number of the mesh holes and are joined to the meshes . The support tubes are spread out in positions within the grid with a predetermined number of support tubes and a distribution thereof within the grid, which is rotationally symmetric about 90° with regard to a rotation about the central axis of the spacer, the central axis is perpendicular to the grid plane, the number of rows and columns that do not contain any support tubes is minimal. Optionally, remaining inner rows and columns that do not contain any support tubes are not situated next to one another.

Abstract: An fuel assembly with a connection between a fuel channel and a lower tie plate to allow the fuel channel to be removed from an internal fuel rod assembly without the necessity of moving interior fuel rods during removal of the fuel channel.

Abstract: A fuel element for a nuclear reactor has fuel rods with nuclear fuel guided through spacers. The spacers are equipped with devices that exert a swirling impulse upon a coolant flowing along the fuel rods. In order to present as little flow resistance as possible for the coolant, these swirl-introducing devices have the form of a vane with a spoonlike or bladelike shape and they extend into the coolant flow. Owing to the shape—here the vane is curved in the longitudinal and in the transverse directions—practically all cross sections of the vane have such a high geometrical moment of inertia that even a vane made of a thin sheet metal is sufficiently rigid. Fuel elements configured according to the invention are particularly suitable for use in boiling water nuclear reactors.

Abstract: A spacer grid for PWR assemblies is characterized by curved flow channels between adjacent fuel rods and straight, essentially flat strips connecting opposite side plates of the spacer. The latter strips prevent bowing-out of the side plates during fuel assembly fabrication and during operation in the reactor. Additionally, the spacer grid allows accurate positioning of the fuel rods on a square lattice with a precisely defined pitch, and support of the rods in their spacer cells is such that rod bow will be minimized. The direction of the nozzles on the flow channels has been chosen to promote cross-flow of the coolant through the assembly.

Abstract: Flow of mercury from a liquid-heavy-metal inflow port toward an inner forward end of a container body is rectified by a plurality of incoming-passage guide vanes in a liquid-heavy-metal incoming passage. Flow of the mercury from the forward end of the container body toward a liquid-heavy-metal outflow port is rectified by a plurality of return-passage guide vanes in a liquid-heavy-metal return passage. As a result, occurrence of stagnation and/or recirculation flows of the mercury in the container body is suppressed and a steady and highly uniform stream of the mercury is formed throughout in the container body. The container body is covered with a container outer shell to prevent any leakage of the mercury to outside due to a damage of the container body.

Abstract: The present invention relates to a fuel assembly for a light-water reactor with a substantially square cross section wherein the fuel assembly comprises a plurality of fuel rods (4). The fuel rods (4) extend between a bottom tie plate (5) and a top tie plate (6) and a coolant is adapted to flow upwards through the fuel assembly. At least one of the top tie plates (6) or the bottom tie plates (5) comprises flow openings (22, 22a, 22b) for the passage of the coolant and side supports (17) for supporting the fuel rods (4) in the lateral direction. The side supports (17) are designed in one and the same sheet-metal piece as the flow openings (22, 22a, 22b) and the side supports (17) are folded substantially 90° in relation to the other structure of the top tie plate (6) or the bottom tie plate (5).

Abstract: A fuel assembly for a boiling water reactor comprising at least one rotary cell (13a-13d) which has fuel rods (4) arranged in a number of concentric rings with a substantially circular shape, and a steam conducting channel (17a-17d) arranged in the centre of the concentric rings through which steam flows upwards through the fuel assembly. At least certain of the fuel rods in the rings are arranged such that their upper ends are displaced in relation to their lower ends in the tangential direction such that water and steam are brought to rotate around the steam conducting channel.

Abstract: A holder for fuel elements in a reactor, in particular in a boiling water reactor, is provided, as well as a method for repairing such a holder. A core grid is demounted from a core shroud and replaced by a new forged core grid for the purpose of repairing the holder. An adapter ring is to be inserted between the new core grid and the core shroud. There is provision for connecting the adapter ring to the core grid without a welding operation, for example by shrink fitting.

Abstract: The present invention relates to a fuel assembly with a substantially square cross section for a light-water reactor. The light-water reactor comprises a plurality of fuel rods extending between a top tie plate and a bottom tie plate. A fuel rod comprises a cladding tube which surrounds a column with fissionable material. According to one aspect of the invention, at least one fuel rod is provided with an axial gap in the fissionable material. Around this axial gap, the mass of the material is greater than the mass of the material in the main part of the cladding tube.

Abstract: The vessel of the nuclear reactor includes at least three assemblies (22) distributed around the periphery of the core support plate (25), each comprising a key (26) fixed to the inner surface of the wall (21) of the vessel at the core support plate (25) and a cut-out (29) in the external edge of the core support plate (25) and open towards the outside in order to receive, with a clearance, an end part (30) of the key (26). The cut-out (29) includes an upper surface (29d) perpendicular to the axis of the wall (21) of the vessel and of the lower internals (23), which is machined in the core support plate (25) in order to retain the internals (23) in the event of a drop. A keyhole slot (28) is fixed inside the cut-out (29). In order to carry out the adjustment of the dimensions of the keyhole slot (28), a standard keyhole slot may be used, equipped with distance measurement sensors in order to obtain the desired clearances between the key (26) and the keyhole slot (28).

Abstract: A low pressure drop easy load fuel assembly rod end cap 40 for pressurized water reactor fuel assembly rods 10 has a solid Zircaloy radiused tip 42. The tip 42 blends into a longitudinal profile defined by a smooth convex curve 44,46 which blends into a substantially cylindrical surface portion 48 of a diameter substantially equal to the diameter of the fuel cladding tube or other shank 50.

Abstract: A removable and reusable cap for fuel rod ends to prevent grid damage during loading permits fuel end configurations to match utility's special tooling for fuel assembly repair and reconstitution. The elastomeric transitory fuel rod guidance ends expand over a flange and temporarily snap into place in a groove in the fuel rod end to provide a tapered guiding surface.

Abstract: An improved spacer is disclosed which contains an Inconel grid and a Zircaloy surrounding band. The Inconel grid can be fabricated from the extremely thin and highly elastic spring metal utilizing a modification of a prior art cell construction that includes paired inwardly bent vertical spring legs with cantilevered and rod encircling upper and lower arm pairs. The spring legs extend at spaced apart locations between the upper and lower arm pairs and have a medial spring rod contacting portion for biasing the rods into stops on the rod encircling arm pairs. The springs at the upper and lower ends are provided with spring dimple stops to prevent over stressing of the spring during assembly or handling of the fuel bundle into which the spacer is incorporated. The rod encircling arm pairs have an offset from center where the two arms meet at their distal ends to complete encirclement of the rods. This offset from center enables the cells to be fastened in cell pairs at their respective embracing arms.

Abstract: A nuclear fuel element for use in power-producing nuclear reactors, comprising a circular metal cladding tube containing sintered cylindrical oxide fuel pellets, the tube being formed internally with a substantially cylindrical inner surface having a plurality of longitudinal ribs forming axially extending channels. The fuel pellets have chamfered endfaces creating toroidal spaces at the adjoining ends of the fuel pellets, the ratio of axial channel to toroidal space volumes including any pellet dishing being at most about one (1);a process for the manufacture of such fuel element.

Abstract: An integral nuclear fuel element assembly utilizes longitudinally finned fuel pins. The continuous or interrupted fins of the fuel pins are brazed to fins of juxtaposed fuel pins or directly to the juxtaposed fuel pins or both. The integrally brazed fuel assembly is designed to satisfy the thermal and hydraulic requirements of a fuel assembly lattice having moderator to fuel atom ratios required to achieve high conversion and breeding ratios.

Abstract: In a nuclear fuel assembly having a coolant conducting or water tube which also retains the spacers in axial position, the fuel rods experience greater axial growth with exposure than the water tube creating a risk that the water tube might become disengaged from the supporting tie plates. An arrangement for preventing such disengagement is described including lengthened end plug shanks for the water tube, a protective boss surrounding the lower end plug shank to protect it from flow induced vibration, a conical seat for the lower end plug and an arrangement for limiting upward movement of the water tube.

Abstract: A fuel pin for a liquid metal nuclear reactor is provided. The fuel pin includes a generally cylindrical cladding member with metallic fuel material disposed therein. At least a portion of the fuel material extends radially outwardly to the inner diameter of the cladding member to promote efficient transfer of heat to the reactor coolant system. The fuel material defines at least one void space therein to facilitate swelling of the fuel material during fission.