Mitsubishi Nuclear Fuel Co., Ltd.

Mitsubishi Heavy Industries Limited

Mitsubishi Materials Corporation

Other

Eiji Yoneda

Akio Sando

Takeshi Isobe

Yoshiharu Mae

Yoshitaka Suda

Toshimichi Takahashi

Yasuhisa Asano

Mitsuteru Sugano

Minoru Murata

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.

X-ray fluorescence inspection apparatus

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.

Method for producing a fuel rod

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.

Fuel rod for light water reactor and method for manufacturing the same

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.

Method for welding and apparatus therefor

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.

A method is disclosed for welding an end plug to an open end of a surface-coated tube in order to provide a control rod. First, the end plug is brought into pressed abutment with the open end of the surface-coated tube. Then, resistance welding is performed in order to join the end plug with the open end of the surface-coated tube by applying electric current between the surface-coated tube and the end plug to heat the same while keeping the end plug pressed in abutment with the open end of the surface-coated tube. With these procedures, even when a surface-coated tube having a hard coating formed over its entire length is employed, the coating material is prevented from dissolving into the welded portion and therefore ensures an excellent welding quality, and the resulting control rod exhibits excellent characteristics over its entire length.

Method for welding of end plug of control rod

A resistance welding method for a fuel rod is presented in which the gas seal opening is closed with a sealing material of the same composition as the end plug material. The method enable to perform welding stably in a pressurized welding chamber, and the process is amenable to automation. The sealing material body is made of a wire, and is pressed against the conical shaped opening provided on the end plug. The welding method avoids contaminating the weld with undesirable impurities from the electrode material, and the welding operations is designed so that there is no need to reshape the end of the electrode or adjust the gap between the sealing material and the seal opening.

Method for welding of fuel rod

A welding apparatus for welding an end plug on the end of a pellet filled nuclear fuel rod includes a holding mechanism, an abutting member, a torch and a pressing mechanism. The holding mechanism is for holding the external periphery of the fuel rod with the end plug attached thereto. The abutting member is disposed opposite to the holding mechanism, and the end plug of the fuel rod butts up against the abutting member. The torch is disposed between the holding mechanism and the abutting member, and is placed diametrically opposite to the external surface of the fuel rod. The holding mechanism and the abutting member are made so that the distance therebetween can be adjusted, and the pressing mechanism is provided on one of the holding mechanism or the abutting member, and operates to move the holding mechanism and the abutting member to approach each other. In a welding apparatus of such a design, the fuel rod is held by the holding mechanism, and the pressing mechanism pushes the holding mechanism toward the abutting member, and while retaining such a position at a constant compressive force, welding of the end plug is performed. Therefore, the welding is performed without being affected by the variations in the compressive force caused by welding heat distortions, thereby providing a weld of high integrity and quality.

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Naka-gun, Japan

Eiji Yoneda