An improved retention and alignment system for nuclear fuel rods includes an upper nozzle plate and a lower nozzle plate, nuclear fuel rods, each having an upper end and a lower end and extending axially between the upper and lower nozzle plates, a first precision magnet incorporated onto the lower end of the fuel rod, and a plurality of second precision magnets incorporated onto the lower nozzle plate in positions confronting the first precision magnets on the fuel rods. Each first precision magnet has at least one of a magnetic north or south polarity and the second precision magnet has at least one of a magnetic south or north polarity opposite the polarity of the confronting first precision magnet to effect magnetic attraction between the confronting first and second precision magnets. Grids between the upper and lower nozzle plates form cells through which the fuel rods pass. Precision magnets of the same polarity may be positioned laterally along the fuel rods and grid walls in positions confronting each other to repel the fuel rods from the grid walls to maintain fuel rod alignment and prevent contact between the fuel rods and the grids.

Fuel assemblies of nuclear reactors that increase the efficiency of a filter for retention of foreign objects in the coolant while maintaining the hydraulic resistance of the fuel assembly at the same level. The nuclear reactor's fuel assembly comprises a head, a fuel elements bundle, spacer grids and the filter for retention of the foreign objects. The filter is installed in the bottom nozzle of a fuel assembly and is made in the form of rectilinear plates' groups, located in the cross section of the bottom nozzle.

An apparatus including a lower end fitting having a top planar surface, a bottom planar surface, a counterbore defined therebetween, an opening extending from the counterbore to the top planar surface, and a lock recess that extends both radially outwardly from the counterbore and extends inwardly into the lower end fitting from the bottom planar surface. The apparatus includes a guide tube having a lower end and an end plug configured to connect with the lower end of the guide tube. The end plug has a threaded shaft sized to pass through the opening of the lower end fitting, and a female lock nut has a deformable side wall configured to be swaged into the recess of the lower end fitting. The lock recess remains visible as viewed from the bottom planar surface of the lower end fitting when the female lock nut is fully disposed in the counterbore.

A nuclear fuel assembly having lateral support provided by a bimetallic spring that extends from a side of the fuel assembly under certain core conditions to pressure against an adjacent component and withdraws under other core conditions, such as shutdown, to enable the nuclear fuel assembly to be aligned or withdrawn from the core and repositioned.

Apparatuses, systems, and methods of filtering debris from the bottom nozzle of a nuclear reactor while minimizing loss coefficients are disclosed herein, including a debris filter bottom nozzle with a plate-like body, a plurality of flow passages, and a filter positioned within at least one flow passage, wherein the at least one flow passage has a dimension based at least in part on a predetermined loss coefficient of the at least one flow passage and a predetermined filtration capability of the filter.

A debris filtering skirt configured for use with a flow plate of a bottom nozzle of a nuclear reactor is disclosed herein. The debris filtering skirt includes a base portion defining an opening between a bottom edge and a reactor vessel lower core plate, and the opening includes a dimension configured to position the bottom nozzle a predetermined distance away from the reactor vessel lower core plate. The debris filtering skirt also includes a plurality of holes, and at least one hole of the plurality of holes includes a dimension determined based, at least in part, on a predetermined size of debris capable of traversing through the inlet and the outlet. The dimension of the opening and the dimension of the at least one hole are determined based, at least in part, on a predetermined loss coefficient of the bottom nozzle.

A nuclear reactor has a core installed on a lower core plate and formed from multiple fuel assemblies, each fuel assembly including a structural cage assembly. The structural cage assembly has an upper end fitting, mid grids, and a lower end fitting (LEF). The LEF positions the fuel assembly using four locating pins located at each corner of the LEF. The pins position the fuel assembly laterally by mating with receiving holes in the lower core plate. The locating pins have a chamfered tip with a flat end. The chamfered tip allows for a greater positioning margin when installing the fuel assembly in the core by guiding the pins into holes in the lower core plate, and the flat tip provides strength and stability in case the assembly is inadvertently rested on the tip of the pin instead of the LEF pads.

Methods of installing an external dashpot tube around a control rod guide tube in a nuclear reactor fuel assembly are disclosed herein. The nuclear reactor fuel assembly may include a top nozzle, a bottom nozzle, and a plurality of grids. The various methods may comprise inserting a guide tube into a skeleton of the nuclear reactor fuel assembly to a lower middle grid, the lower middle grid being second closest grid to the bottom nozzle of the plurality of grids. The various methods may also include installing an external dashpot tube over the guide tube after it has been inserted to the lower middle grid; inserting the guide tube with the installed external dashpot tube to the bottom nozzle; attaching the guide tube to the skeleton; and bulging the guide tube onto the external dashpot tube.

Embodiments of a bottom nozzle of a nuclear fuel assembly provided with flow holes by utilizing a layered aircraft airfoil structure are provided. The bottom nozzle not only increases efficiency of filtering foreign substances by minimizing a size of the flow holes by constituting a shape of flow holes into cross stripes but also prevents coolant water flow velocity drop through prevention of coolant water pressure drop by constituting a lateral sectional shape of the grid frames constituting the cross stripes into an aircraft airfoil type.

Debris filters fit in fuel assembly lower tie plates and filter fluids passing therethrough. Filters use a series of adjacent plates with aligned peaks and valleys to create several channels. The plates have small excisions in diamond, triangle, or other debris-catching shapes, such as near a lower portion of the filter where fluid enters the filter. Excisions may alternate around each channel, such as four alternating cut-outs in 90-degree intervals about a channel circumference. Excisions may be sized to entrap smaller debris common in reactor coolant flow and liable for fretting damage to fuel cladding. Multiple vertical stages can be used in filters, with different channels for each stage. Ligaments may hold each stage to the next, potentially with a gap between stages for intermixing. Plates, peaks, valleys, ligaments, and excisions may all be formed in a single stamping operation to eliminate excess or overlapping pieces or extensions.