Proposed is an internal electrode insertion device for transferring the internal electrode to a welding position in order to weld a skeleton of a nuclear fuel assembly, the device including: a table; a plurality of internal electrode bars disposed in parallel in a plurality of rows on a top portion of the table; guide members provided on the table and configured to guide a horizontal movement of the internal electrode bars; guide rails provided in parallel with an alignment direction of the internal electrode bars on the top portion of the table; a driving unit provided with a servomotor thereon, thereby performing horizontal movement driving along the guide rails; and a control unit for controlling driving of the servomotor based on a preset position of each of the internal electrodes.

Proposed is a spacer grid of a nuclear fuel assembly that may be manufactured using 3D printing with a high degree of design freedom, excluding sheet metal processing and welding processing. The spacer grid of the nuclear fuel assembly has hollow grid cells (110) having inner walls (111) arranged in a square lattice structure and connected to each other by being circumscribed, each of the grid cells including: a plurality of elastic support portions (112) protrudingly provided by being curved inwardly from the inner walls (111) and elastically supporting a fuel rod (10) in a state in which at least three elastic support portions are disposed at equal angles; and a plurality of inner mixing vanes (113) protrudingly provided while each upper tip portion thereof spirally turns along an associated one of the inner walls above the elastic support portions (112).

A method comprises inserting the fuel rod (4) through the spacer grids (14) aligned along an assembling axis (A) with passing the fuel rod (4) through a lubrication chamber (30) aligned with the spacer grids (14) such that the lubrication chamber (30) is passed through by the fuel rod (4) before the insertion of the fuel rod (4) through one of the spacer grids (14), and circulating a lubrication fluid containing a gas and a lubricant in gaseous phase and/or mist form in the lubrication chamber (30). The lubrication fluid is injected in the lubrication chamber (30) at a temperature strictly higher than ambient temperature, such that lubricant deposits or condensates in liquid phase with forming a lubricant film on an external surface of the fuel rod (4) that is being inserted through said one of the spacer grids (14).

A holding fixture for assisting in assembly of a support grid for nuclear fuel rods and including a plurality of straps each having a plurality of slots extending approximately half a height of the straps and tabs formed beside or between the slots. The holding fixture includes an actuation plate, a support plate having a plurality of receiving members structured to receive therein straps of the support grid and having a plurality of cells, and a plurality of cam assemblies structured to move to deflect every other tab of the straps received in the plurality of receiving members. The cam assemblies are disposed in every other cell of the support plate.

A process is described that includes forming a metal alloy component having a pre-specified three dimensional geometry for use in a nuclear reactor by an additive manufacturing process followed by annealing the formed component at a first annealing temperature within the alpha temperature range of the phase diagram for the metal alloy. A second annealing step at a second annealing temperature lower than the first annealing temperature may be added. Alternatively, annealing may be at an annealing temperature in the alpha+beta temperature range of a phase diagram for the metal alloy, followed by a second anneal in the alpha temperature range of the phase diagram for the metal alloy.

A method is for manufacturing a nuclear fuel assembly (2) comprising nuclear fuel rods (4) arranged in a bundle and a skeleton (6) supporting the fuel rods (4). The method comprise the steps of inserting fuel rods (4) into the skeleton (6) to obtain a fuel assembly (2) and packaging the fuel assembly (2) in view of transportation. The steps are being performed in a same nuclear fuel assembly manufacturing plant (20), preferably in a same nuclear fuel assembly manufacturing building (60).

A method is for manufacturing a nuclear fuel assembly (2) comprising nuclear fuel rods (4) arranged in a bundle and a skeleton (6) supporting the fuel rods (4). The method comprise the steps of inserting fuel rods (4) into the skeleton (6) to obtain a fuel assembly (2) and packaging the fuel assembly (2) in view of transportation. The steps are being performed in a same nuclear fuel assembly manufacturing plant (20), preferably in a same nuclear fuel assembly manufacturing building (60).

A spacer grid of a nuclear fuel assembly having a simple shape structure is proposed. The spacer grid includes square grid cells having respective inner walls and constituting a square lattice structure. Each of the grid cells includes a plurality of springs for elastically supporting a fuel rod. Each of the plurality of the springs has a fixed end along a vertical direction on each of the inner walls and a free end curvedly provided in a horizontal direction from the fixed end. The grid cells also include a plurality of flow channels each provided in the vertical direction to each of the grid cells and a plurality of mixing vanes each protrudingly provided in a downstream direction of cooling water flow at end parts of each of the grid cells.

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 holding fixture for assisting in assembly of a support grid for nuclear fuel rods and including a plurality of straps each having a plurality of slots extending approximately half a height of the straps and tabs formed beside or between the slots. The holding fixture includes an actuation plate, a support plate having a plurality of receiving members structured to receive therein straps of the support grid and having a plurality of cells, and a plurality of cam assemblies structured to move to deflect every other tab of the straps received in the plurality of receiving members. The cam assemblies are disposed in every other cell of the support plate.