Abstract: One object of the present invention is to provide a production method for a nuclear fuel assembly support grid that improves the corrosion resistance of welded parts without impairing the characteristics of the support grid so as to be able adequately withstand highly efficient operation. In order to achieve the object, the present invention provide a production method for a nuclear fuel assembly support grid comprising the steps of: assembling a plurality of straps in a grid form; welding intersections of each strap; and carrying out annealing thereafter to precipitate an intermetallic compound on the welded parts.

Abstract: A foreign matter filter provided between a DFBN and a lower grid has two adjacent thin straps assembled into a lattice. The straps are equipped on the front and back sides with axially continuous protrusions.

Abstract: A foreign matter filter provided between a DFBN and a lower grid has two adjacent thin straps assembled into a lattice. The straps are equipped on the front and back sides with axially continuous protrusions.

Abstract: One object of the present invention is to provide a production method for a nuclear fuel assembly support grid that improves the corrosion resistance of welded parts without impairing the characteristics of the support grid so as to be able adequately withstand highly efficient operation. In order to achieve the object, the present invention provide a production method for a nuclear fuel assembly support grid comprising the steps of: assembling a plurality of straps in a grid form; welding intersections of each strap; and carrying out annealing thereafter to precipitate an intermetallic compound on the welded parts.

Abstract: A supporting grid welding apparatus including a welding chamber configured to encase a supporting grid, at least one laser device disposed outside of the welding chamber, and a drive device configured to move the welding chamber independently from said supporting grid.

Abstract: Welding operations on a grid support 1 housed in a welding chamber 23 is carried out using a laser welding apparatus placed outside the welding chamber. In the interior space of the chamber, a pair of supply nozzles 44 are disposed on each of the mutually orthogonal edge sections of two top and bottom glass surfaces 27a, 27b of the roughly cubic chamber 23. An inert gas is ejected in a planar stream from the blast slot openings 45 provided on each supply nozzle 44 along the top and bottom glass surfaces and side glass surfaces. The glass surfaces 27a, 27b that face many welding sections of the grid support are shielded by the sweeping action in two directions, and the glass surfaces 27c that oppose lesser number of welding sections are shielded by the sweeping action in one direction with the inert gas. Fumes and plasmas produced from welding sections are thus swept away before they can reach the glass surfaces, and are discharged with the spent inert gas.

Abstract: The apparatus enables measurement of the amount of contaminant in a welded portion to high accuracy and in a short time, using an X-ray fluorescence inspection apparatus. The end portion of a fuel rod having a bead portion on an end surface of an end plug is covered with an approximately cylindrical cap, with the bead portion exposed via a central aperture. The material of the cap is preferably titanium. With titanium the fluorescent X-ray radiation has a different wavelength from that of tungsten and zircaloy, and the amount of fluorescent X-ray radiation detected by a detector at a diffraction angle of the spectrum W-L &agr; of fluorescent X-ray radiation for tungsten is less than those for tungsten and zircaloy. Therefore, while the fluorescent X-ray radiation of the cap which covers the end surface of the end plug around the bead portion results in noise, the amount of this fluorescent X-ray radiation measured by the detector is much smaller than for the tungsten and the zircaloy of the bead portion.

Abstract: The process of the present invention comprises the steps of (a) a step of dissolving a condensed tannin powder in an aqueous alkaline solution, (b) a step of admixing an aqueous aldehyde solution with the aqueous solution obtained in the step (a), (c) a step of adding the aqueous solution obtained by the above step (b) to a hydrophobic solvent containing a polyether type nonionic surfactant under heating and stirring to disperse the aqueous solution in the form of droplets in said hydrophobic solvent and (d) evaporating water components from the above-mentioned droplets to form a spherical and gelled insoluble tannins. Water content of the gel can be widely controlled as 5 to 90% as compared with the conventional adsorbent and the network structure and molecular space are changed depending on the size of the metal ion to be adsorbed so that a gelled insoluble tannin which can increase an adsorption capacity of metals can be obtained.

Abstract: A method for manufacturing a fuel rod of the present invention includes a welding step of welding a cladding tube of said fuel rod to a plug by arc discharge; and a post welding step of subsequently discharging an arc to a welded portion by a predetermined arc current lower than that of the welding step. In the welding step and in the post welding step, the cladding tube and the plug are rotated with respect to an electrode for discharging the arc. The rotation speed of the cladding tube and the plug in the post welding step is higher than that in the welding step.

Abstract: A fuel rod for a light water reactor comprises a cladding tube which comprises a zirconium alloy having a composition including 0.6 to 2.0% by weight of Nb, 0.5 to 1.5% by weight of Sn, 0.05 to 0.3% by weight of Fe, and the balance being Zr and incidental impurities; uranium oxide fuel pellets packed in the cladding tube; and end plugs comprising a zirconium alloy and closing both ends of the cladding tube. The cladding tube is sealed by TIG welding with the end plugs. Grain boundaries in each heat affected zone of the cladding tube, which are adjacent to a bead formed by TIG welding, have structural compositions including 4 to 30% by weight of Nb, and 0.9 to 20% by weight of Fe.

Abstract: A fuel rod for a light water reactor comprises a cladding tube which comprises a zirconium alloy having a composition including 0.6 to 2.0% by weight of Nb, 0.5 to 1.5% by weight of Sn, 0.05 to 0.3% by weight of Fe, and the balance being Zr and incidental impurities; uranium oxide fuel pellets packed in the cladding tube; and end plugs closing both ends of the cladding tube. The cladding tube is sealed by TIG welding with the end plugs. Precipitates having grain diameters of 0.01 to 0.5 .mu.m and comprise intermetallic compounds containing Zr, Nb and Fe are present at grain boundaries in the structure of heat affected zones of the cladding tube, the heat affected zone being adjacent to a bead formed by TIG welding.

Abstract: A zirconium alloy for use in spacer grids for nuclear reactor fuel claddings, which consists essentially of, on a weight percent basis,2.5 to 10% Nb,0.01 to 1.5% of one or more components selected from the group consisting of Y and rare earth elements and oxides thereof,0.05 to 1% of one or more optional element selected from the group consisting of Fe, Cr, Mo and V, andthe remainder Zr and incidental impurities.

Abstract: A process for manufacturing uranium oxide powder from UF.sub.6 which comprises converting UF.sub.6 to UO.sub.2 F.sub.2 by its reaction with excess alcohol in gas phase and further converting the formed UO.sub.2 F.sub.2 to uranium oxide by combusting hydrocarbon formed in the gas phase reaction and the excessive part of alcohol with oxygen containing gas supplied separately and supplying a regulated amount of steam separately to the combustion reaction zone.

Abstract: A method and system for enclosing a gas at a preselected pressure in a nuclear reactor fuel rod having two ends open to its interior. Hermetically enclose each end in a separate airtight chamber. Introduce the gas into the first chamber and open the second chamber to purge the fuel rod interior and both chambers of residual atmosphere. After purging close the open second chamber and determine the gas pressure in the fuel rod interior. When the pressure reaches the preselected value, hermetically seal each fuel rod end while in its respective chamber. After sealing, remove the fuel rod from the chambers.

Abstract: A process for manufacturing uranium dioxide powder which comprises forming fine uranium dioxide powder having a high sinterability and coarse uranium dioxide powder having a low sinterability continuously in one process by changing periodically the precipitation condition of the ammonium diuranate under the same condition of calcining and reducing of the ammonium diuranate. The thus obtained mixture of these uranium dioxide powders is suitable for uranium dioxide pellet which is a fuel of nuclear power reactor.