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: The bar-code printing method of the present invention comprises a step of irradiating the circumferential surface of a metal tube with laser beams so as to make at least one group of thin elementary lines arranged in parallel with each other at intervals. The width of the intervals is determined so that each group of elementary lines can be detected as one of the thick lines contained in the bar-code.

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: The present invention relates to a method for welding comprising the steps of: contacting a plurality of workpieces to be welded having different heat capacities so as to form a boundary portion therebetween; placing a welding electrode in proximity to the boundary portion; generating an arc discharge between the welding electrode and the boundary portion; and supplying gas to the boundary portion, wherein more gas being supplied to one of the workpieces having a lower heat capacity than another workpiece having a higher heat capacity.

Abstract: An interior image receiving apparatus which includes an image receiver positioned facing an opening of a hollow object. Also included is a reflecting mirror positioned between the image receiver and the opening, in which the image receiver receives an image of the inner surface of the object reflected by the mirror.

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 nuclear fuel green compact is produced by sintering in an atmosphere of reducing gas. A mixed gas of hydrogen and nitrogen to which water vapor is added is used as the reducing gas. By establishing the amount of water vapor added to the mixed gas of hydrogen and nitrogen so that dew point as an indicator is -15.degree. C. or more, the nitrogen content of the produced pellets can be controlled to be equal to or less than 0.0075 wt %.

Abstract: The present invention relates to a cylindrical body inspection apparatus characterized in comprising: a) rotating mechanism for supporting and rotating a cylindrical body; b) sensor comprising a light emitting unit for irradiating light onto a surface to be inspected of a cylindrical body, and a light detecting unit for detecting incoming light reflected from the surface to be inspected; this sensor detects displacement information corresponding to a displacement of distance from the surface to be inspected to the light detecting unit, and information regarding the quantity of incoming light corresponding to quantity of reflected light from the surface to be inspected; c) computing unit for computing surface information and external form formation based on the above displacement information and information regarding quantity of incoming light from the sensor; and d) discriminating unit for discriminating the presence or absence of defects relating to shape of the cylindrical body based on the surface informat

Abstract: An arrangement of fuel rod support members having dimples and springs is presented to prevent abrasive wear of the fuel rods caused by bouncing of the fuel rods against the supporting members caused by vibrations in a diagonal direction of the support grids. The supporting members are disposed such that dimples are respectively provided on one pair of adjacent walls located on one side of the vibrational direction while springs are respectively provided on adjacent walls located on the opposite side of the vibrational direction.

Abstract: A method of forming a nuclear fuel assembly grid, as well as the resulting grid itself, are disclosed. In the formation of the grid, formed straps having slits are prepared, arranged into a grid form by intersecting the straps with each other through the slits, and the intersections of the associated straps are brazed. Prior to the step of arranging the straps, those portions to be brazed are subjected to a pretreatment, in which an paste, prepared of a mixture of a filler metal and a vehicle, is applied to the portions to be brazed to form a thin film thereon.

Abstract: A fuel assembly is presented in which a plurality of support grids are disposed along the longitudinal direction of the fuel rods. The straps forming the grid cells of the support grids are provided with mixing vanes for generating turbulent flow of the cooling water passing through the grid cells. In a plan view of the support girds, each of the mixing vanes protrudes inwardly of the grid cells and is disposed along a positive diagonal direction and a negative diagonal direction. This configuration of the mixing vanes are effective in preventing the generation of systematic vibrations in the fuel assembly by canceling the effects of the turbulent flows of the cooling water. The direction of protrusion of the mixing vanes can be in two diagonal directions within one support grid, or it can be unidirectional along either diagonal direction within one support grid.

Abstract: A method of assembling a fuel assembly is presented so as to reduce radiation exposure to the assembly workers and to simplify the assembly procedure. Sleeves are pre-attached to an upper nozzle, and the guide pipes are inserted into respective grid cells through the sleeves of the upper nozzle and through the sleeves of the grids. The guide pipes are fixed in place to the sleeves of the upper nozzle and of the grids by bulging. There is no welding step necessary to join any of the assembly components while the assembly is in a semi-assembled condition. Therefore, the method is simple and efficient, and reduces the risk of radiation exposure to the assembly workers.