Abstract: Methods of installing an external dashpot tube around a control rod guide tube in a nuclear reactor fuel assembly are disclosed herein. The nuclear reactor fuel assembly may include a top nozzle, a bottom nozzle, and a plurality of grids. The various methods may comprise inserting a guide tube into a skeleton of the nuclear reactor fuel assembly to a lower middle grid, the lower middle grid being second closest grid to the bottom nozzle of the plurality of grids. The various methods may also include installing an external dashpot tube over the guide tube after it has been inserted to the lower middle grid; inserting the guide tube with the installed external dashpot tube to the bottom nozzle; attaching the guide tube to the skeleton; and bulging the guide tube onto the external dashpot tube.

Abstract: A nuclear fuel assembly comprising a plurality of control rod guide assemblies. At least one of the control rod guide assemblies includes a guide tube having an axial dimension, the guide tube being supported by the plurality of grids and extending axially between the top nozzle and the bottom nozzle, the guide tube having an upper portion having a first radius and a lower portion having a second radius less than the first radius, and an external dashpot tube disposed around a portion of the lower portion in an area beginning at the bottom grid and extending toward the top nozzle.

Abstract: A nuclear fuel assembly comprising a plurality of control rod guide assemblies. At least one of the control rod guide assemblies includes a guide tube having an axial dimension, the guide tube being supported by the plurality of grids and extending axially between the top nozzle and the bottom nozzle, the guide tube having an upper portion having a first radius and a lower portion having a second radius less than the first radius, and an external dashpot tube disposed around a portion of the lower portion in an area beginning at the bottom grid and extending toward the top nozzle.

Abstract: A nuclear fuel assembly comprising a plurality of control rod guide assemblies. At least one of the control rod guide assemblies includes a guide tube having an axial dimension, the guide tube being supported by the plurality of grids and extending axially between the top nozzle and the bottom nozzle, the guide tube having an upper portion having a first radius and a lower portion having a second radius less than the first radius, and an external dashpot tube disposed around a portion of the lower portion in an area beginning at the bottom grid and extending toward the top nozzle.

Abstract: The present invention relates generally to nuclear reactors, and more particularly, to nuclear reactors having fuel assemblies that employ support grids. A method of reducing friction and physical contact between a fuel rod and support grid in a nuclear fuel assembly is provided. The method includes applying a lubricant composition to the outer surface of the fuel rod during fuel assembly fabrication and removing the lubricant composition afterward.

Abstract: The present invention relates generally to nuclear reactors, and more particularly, to nuclear reactors having fuel assemblies that employ support grids. A method of reducing friction and physical contact between a fuel rod and support grid in a nuclear fuel assembly is provided. The method includes applying a lubricant composition to the outer surface of the fuel rod during fuel assembly fabrication and removing the lubricant composition afterward.

Abstract: A secure connection between the bottom nozzle of a nuclear fuel assembly and the control rod guide thimbles having two or four crimped pockets in the side wall of a bottom nozzle leg counterbore which are formed by drilling two or four blind holes through the top surface of the bottom nozzle. After attaching the bottom nozzle to the fuel assembly with a crimp bolt a pneumatic tool is then inserted into a flanged cup feature on the crimp bolt head and the flanged portion of the cup feature of the crimp bolt is deformed into the crimp pockets. The crimp pockets are contained within the leg counterbore and prevent the screw from rotating or falling out of the assembly in the event of preload loss or screw fracture.

Abstract: A secure connection between the bottom nozzle of a nuclear fuel assembly and the control rod guide thimbles having two or four crimped pockets in the side wall of a bottom nozzle leg counterbore which are formed by drilling two or four blind holes through the top surface of the bottom nozzle. After attaching the bottom nozzle to the fuel assembly with a crimp bolt a pneumatic tool is then inserted into a flanged cup feature on the crimp bolt head and the flanged portion of the cup feature of the crimp bolt is deformed into the crimp pockets. The crimp pockets are contained within the leg counterbore and prevent the screw from rotating or falling out of the assembly in the event of preload loss or screw fracture.