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and withdraws under other core conditions, such as shutdown, to enable the nuclear fuel assembly to be aligned or withdrawn from the core and repositioned.

A fuel assembly design for nuclear reactors that is used in fast neutron reactor cores to provide more reliable spacing of a fuel element bundle in a fuel assembly and reduced local stress in the cladding of the fuel elements in the region where the elements are in contact with spacing elements. The fuel assembly has a top nozzle and a bottom nozzle which are connected to one another by a jacket. A bundle of rod-type fuel is elements arranged in the fuel assembly with the aid of a grid and spiral spacer elements wrapped around the cladding of each fuel element. At least the peripheral fuel elements in the bundle are provided with spacer elements in the form of thin-walled tubes with longitudinal through slots, wherein the elements have a substantially oval cross section in the regions where they are in contact with the jacket.

A nuclear fuel assembly comprising a plurality of control rod guide assemblies. At least one of the control rod guide assemblies includes a guide tube having an axial dimension, the guide tube being supported by the plurality of grids and extending axially between the top nozzle and the bottom nozzle, the guide tube having an upper portion having a first radius and a lower portion having a second radius less than the first radius, and an external dashpot tube disposed around a portion of the lower portion in an area beginning at the bottom grid and extending toward the top nozzle.

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and withdraws under other core conditions, such as shutdown, to enable the nuclear fuel assembly to be aligned or withdrawn from the core and repositioned.

A spacer grid includes interlocked straps comprising metal sheets or plates welded together to define a spacer grid having a top and bottom. The interlocked straps define a plurality of cells comprising vertical passages connecting the top and bottom of the spacer grid. The cells include: upper dimples proximate to the top of the spacer grid and distal from the mid-plane of the spacer grid; lower dimples proximate to the bottom of the spacer grid and distal from the mid-plane of the spacer grid; cantilevered upper springs having fuel rod engagement surfaces proximate to the top of the spacer grid and distal from the mid-plane of the spacer grid; and cantilevered lower springs having fuel rod engagement surfaces proximate to the bottom of the spacer grid and distal from the mid-plane of the spacer grid.

A spacer grid includes interlocked straps comprising metal sheets or plates welded together to define a spacer grid having a top and bottom. The interlocked straps define a plurality of cells comprising vertical passages connecting the top and bottom of the spacer grid. The cells include: upper dimples proximate to the top of the spacer grid and distal from the mid-plane of the spacer grid; lower dimples proximate to the bottom of the spacer grid and distal from the mid-plane of the spacer grid; cantilevered upper springs having fuel rod engagement surfaces proximate to the top of the spacer grid and distal from the mid-plane of the spacer grid; and cantilevered lower springs having fuel rod engagement surfaces proximate to the bottom of the spacer grid and distal from the mid-plane of the spacer grid.

Provided is a laser welding apparatus for spacer grid of nuclear fuel assembly comprising a base frame in which a chamber installment hole is formed horizontally to the center in a way that the hole penetrates the chamber and a guide rail is installed along the chamber installment hole; a welding chamber unit assembled with the base frame in guidance by the guide rail and equipped with an operable door in front and a glass window at the top to be airtight; a laser welding unit mounted on the base frame for radiating laser through the glass window to weld spacer grid in the welding chamber; and a locking member for fixing the welding chamber on the base frame.

A basket assembly for receiving a plurality of fuel assemblies includes a basket having a grid defining spacing between fuel assembly compartments, the grid defining a first compartment for receiving a first fuel assembly and a second compartment for receiving a second fuel assembly, wherein the cross-sectional area of the second compartment is larger than the cross-sectional area of the first compartment. The basket assembly is configured to receive in the first compartment a first fuel assembly, the first fuel assembly being a regular fuel assembly, and the basket assembly configured to receive in the second compartment a second fuel assembly, the second fuel assembly being an irregular fuel assembly, wherein the irregular fuel assembly includes at least one irregular fuel rod.

Nuclear fuel assemblies include non-symmetrical fuel elements with reduced lateral dimensions on their outer lateral sides that facilitate fitting the fuel assembly into the predefined envelope size and guide tube position and pattern of a conventional nuclear reactor. Nuclear fuel assemblies alternatively comprise a mixed grid pattern that positions generally similar fuel elements in a compact arrangement that facilitates fitting of the assembly into the conventional nuclear reactor.

Nuclear fuel assemblies include non-symmetrical fuel elements with reduced lateral dimensions on their outer lateral sides that facilitate fitting the fuel assembly into the predefined envelope size and guide tube position and pattern of a conventional nuclear reactor. Nuclear fuel assemblies alternatively comprise a mixed grid pattern that positions generally similar fuel elements in a compact arrangement that facilitates fitting of the assembly into the conventional nuclear reactor.