Abstract: A fuel rod for a nuclear reactor includes the fuel rod having a first axial zone positioned proximate to a bottom end, a second axial zone positioned adjacent to the first axial zone in the intermediate region, and a third axial zone positioned proximate to a top end. The first axial zone has an enrichment greater than the second axial zone and the second axial zone has an enrichment greater than or equal to the third axial zone. Also includes fuel assemblies having a plurality of fuel rods and methods of designing and manufacturing of fuel rods and fuel assemblies.

Abstract: A fuel rod for a nuclear reactor includes the fuel rod having a first axial zone positioned proximate to a bottom end, a second axial zone positioned adjacent to the first axial zone in the intermediate region, and a third axial zone positioned proximate to a top end. The first axial zone has an enrichment greater than the second axial zone and the second axial zone has an enrichment greater than or equal to the third axial zone. Also includes fuel assemblies having a plurality of fuel rods and methods of designing and manufacturing of fuel rods and fuel assemblies.

Abstract: A high pressure laser welding method and apparatus enables seam welding of a nuclear fuel rod at hyperbaric pressure. In an automatic process, a loaded fuel rod and an upper end plug are mated within a sealable weld box. A pressure within the weld box is controlled relative to a pressure within the fuel rod, and a laser assembly welds the seam at hyperbaric pressure. Helium flowing through a laser window nozzle during welding prevents soot contamination of the laser window glass and prevents formation of ionic plasma. The upper end plug fuel rod welding operation is thus reduced to a single step and eliminates inspection related tasks with respect to a sealed hole.

Abstract: End plugs for nuclear fuel rods are provided with a spot weld along the interior end face of the end plugs to seal any streamer openings or passages along the axis of the end plugs, thereby maintaining the fuel rods sealed at its opposite ends. The spot welds are applied by an automated laser welding system in which pallets of end plugs are supported on X-Y positioning tables below a laser movable in a vertical direction. By successively locating the end plugs in the pallet below the laser, the spot welds are formed along the axis of the end plugs and along the interior faces thereof sealing the end plugs.

Abstract: A TIG welding system for controlling the weld shape for the seal welding of a small pressurization hole in the end plug of nuclear fuel rods. The controlled shape of the seal weld enables improved ultrasonic detection capabilities. The system achieves the desired weld shape by controlling the pressure differential between the interior and exterior volumes of the fuel rod. The weld box pressure is decreased in accordance with Boyle's law while the weld material for sealing the hole is molten. The system uses an output from the weld electronics as an input to a programmable logic controller ("PLC"). After a programmed time delay, the PLC outputs a signal to a solenoid valve to open a "ballast" volume. The expansion of gas from the weld box into the ballast volume causes a sudden drop in pressure to a level below the pressure inside the fuel rod. As a result of this pressure differential, the molten weld material forms a concave weld upon solidification.

Abstract: In an automated final weld apparatus, a transporter conveys nuclear fuel-loaded cladding tubes successively to a check station to verify the presence of a plenum spring in the open end of each cladding tube, a reader station where a unique first end plug serial number is read, an evacuation/backfill station where the cladding tube is backfilled with helium, a seam welding station where a final end plug is welded to the cladding tube open end, and a seal weld station where the tube is pressurized with helium through a pressurization hole in the final end plug, whereupon the pressurization hole is welded closed. After checking for helium leakage, the seam weld is inspected in a succession of inspection stations, and, depending on inspection results, the finished nuclear fuel rods are sorted into accepted and rejected lots.

Abstract: A TIG welding system for controlling the weld shape for the seal welding of a small pressurization hole in the end plug of nuclear fuel rods. The controlled shape of the seal weld enables improved ultrasonic detection capabilities. The system achieves the desired weld shape by controlling the pressure differential between the interior and exterior volumes of the fuel rod. The weld box pressure is decreased in accordance with Boyle's law while the weld material for sealing the hole is molten. The system uses an output from the weld electronics as an input to a programmable logic controller ("PLC"). After a programmed time delay, the PLC outputs a signal to a solenoid valve to open a "ballast" volume. The expansion of gas from the weld box into the ballast volume causes a sudden drop in pressure to a level below the pressure inside the fuel rod. As a result of this pressure differential, the molten weld material forms a concave weld upon solidification.

Abstract: In an automated first weld apparatus, a transporter conveys nuclear fuel cladding tubes successively to a welding station where a separate end plug is welded to an open end of each tube. Thereafter, the transporter indexes the tubes successsively through a cooldown station where the weld is cooled, to a reader station where a unique end plug serial number is read, and then to a succession of inspection stations where the internal and external weld characteristics are automatically examined. The resulting inspection data is correlated with the associated serial number for record purposes and tested against quality assurance standards pursuant to sorting the tubes into accepted and rejected lots.