Abstract: Provided is a fuel assembly 1 for a PWR nuclear reactor capable of stably creating transverse flows of coolant for pressing and securing control rods so as to restrain vibration of the control rods in order to restrain the outer surfaces of the control rods and the inner surfaces of control rod guide tubes from being worn, wherein an upper nozzle arranged above the fuel assembly comprises an adapter plate 6 constituting the lower structure of the upper nozzle, a side wall extended along the periphery of the adapter plate, an overhang projected into a space above the adapter plate from the upper part of the side wall, and apertures for attaching control guide tubes and passage holes, which are formed in the passage surface of the adapter plate, and wherein those 15A, 15B, 15C of the passage holes which are located at positions where the coolant impinges upon the overhang are generally arranged, line-symmetric with respect to diagonal lines of the passage surface serving as symmetric axes Q, and ligaments 21, 2

Abstract: Provided is a fuel assembly 1 for a PWR nuclear reactor capable of stably creating transverse flows of coolant for pressing and securing control rods so as to restrain vibration of the control rods in order to restrain the outer surfaces of the control rods and the inner surfaces of control rod guide tubes from being worn, wherein an upper nozzle arranged above the fuel assembly comprises an adapter plate 6 constituting the lower structure of the upper nozzle, a side wall extended along the periphery of the adapter plate, an overhang projected into a space above the adapter plate from the upper part of the side wall, and apertures for attaching control guide tubes and passage holes, which are formed in the passage surface of the adapter plate, and wherein those 15A, 15B, 15C of the passage holes which are located at positions where the coolant impinges upon the overhang are generally arranged, line-symmetric with respect to diagonal lines of the passage surface serving as symmetric axes Q, and ligaments 21, 2

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: 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 grid structure is presented in which grid cells are formed by orthogonally intersecting straps prefitted in the longitudinal direction with a plurality of slitted spring frame members. Therefore, when the straps are assembled, the spring frame members are also orthogonally intersected. The spring frame members are made of Inconel and provided with welding tabs while the straps are made of zircalloy and provided with their own welding tabs. Therefore, welding can be performed to firmly join the spring frame members to each other while the straps can also be welded firmly to weld the like metals. The spring sections are thus firmly joined and attached to the straps which are firmly joined. The grid of this configuration thus provides an excellent service life without the losing The fuel rod retaining power, which would result from neutron radiation and thermal damages on holding devices made of zircalloy.