Nuclear reactor fuel assembly comprising fuel elements installed in a frame having guide channels and spacer grids; a bottom nozzle; and a removable head. The head comprising collet tubes, an upper shell, a support element in the form of a tube, and springs. The collet tubes comprise two coaxially arranged tubes that are movable relative to each other and that each have stops on their side surfaces. The stops interact with each other to select the length of the collet tubes. The upper shell has a tube with a rigidly fixed plate interacting with the springs. The plate has plural holes having a shape corresponding to a shape of a respective boss of the support element. The clearance in plan view between a respective hole and a respective boss being at least the mounting clearance between the tube of the support element and the tube of the upper shell.

Nuclear reactor fuel assembly comprising fuel elements installed in a frame having guide channels and spacer grids; a bottom nozzle; and a removable head. The head comprising collet tubes, an upper shell, a support element in the form of a tube, and springs. The collet tubes comprise two coaxially arranged tubes that are movable relative to each other and that each have stops on their side surfaces. The stops interact with each other to select the length of the collet tubes. The upper shell has a tube with a rigidly fixed plate interacting with the springs. The plate has plural holes having a shape corresponding to a shape of a respective boss of the support element. The clearance in plan view between a respective hole and a respective boss being at least the mounting clearance between the tube of the support element and the tube of the upper shell.

A damping area or “dash pot” on the upper ends of control rods absorb energy from dropped control rod assemblies without narrowing the diameter of guide tubes. As a result, coolant can freely flow through the guide tubes reducing boiling water issues. The dampening area reduces a separation distance between an outside surface of the control rod and an inside surface of the guide tubes decelerating the control rods when entering a top end of the guide tubes. In another example, the dampening area may be located on a drive shaft. The dampening area may have a larger diameter than an opening in a drive shaft support member that decelerates the drive shaft when dropped by a drive mechanism.

A damping area or “dash pot” on the upper ends of control rods absorb energy from dropped control rod assemblies without narrowing the diameter of guide tubes. As a result, coolant can freely flow through the guide tubes reducing boiling water issues. The dampening area reduces a separation distance between an outside surface of the control rod and an inside surface of the guide tubes decelerating the control rods when entering a top end of the guide tubes. In another example, the dampening area may be located on a drive shaft. The dampening area may have a larger diameter than an opening in a drive shaft support member that decelerates the drive shaft when dropped by a drive mechanism.

A damping area or “dash pot” on the upper ends of control rods absorb energy from dropped control rod assemblies without narrowing the diameter of guide tubes. As a result, coolant can freely flow through the guide tubes reducing boiling water issues. The dampening area reduces a separation distance between an outside surface of the control rod and an inside surface of the guide tubes decelerating the control rods when entering a top end of the guide tubes. In another example, the dampening area may be located on a drive shaft. The dampening area may have a larger diameter than an opening in a drive shaft support member that decelerates the drive shaft when dropped by a drive mechanism.

A damping area or “dash pot” on the upper ends of control rods absorb energy from dropped control rod assemblies without narrowing the diameter of guide tubes. As a result, coolant can freely flow through the guide tubes reducing boiling water issues. The dampening area reduces a separation distance between an outside surface of the control rod and an inside surface of the guide tubes decelerating the control rods when entering a top end of the guide tubes. In another example, the dampening area may be located on a drive shaft. The dampening area may have a larger diameter than an opening in a drive shaft support member that decelerates the drive shaft when dropped by a drive mechanism.

An anti-seismic apparatus for control element drive mechanisms of a nuclear reactor includes: an anti-seismic support plate including a plurality of insertion holes in which the control element drive mechanisms are respectively inserted; and bushings inserted between outer surfaces of the control element drive mechanisms and inner surfaces of the insertion holes. The support plate includes an upper support plate comprising a plurality of first insertion holes, a lower support plate comprising a plurality of second insertion holes at positions corresponding to the first insertion holes, and a connection part connecting the upper support plate and the lower support plate. The connection part includes a support beam vertically extending from an end portion of the lower support plate, an inner flange extending inward from an upper end portion of the support beam, and an outer flange extending outward from the upper end portion of the support beam.

An anti-seismic apparatus for control element drive mechanisms of a nuclear reactor includes: an anti-seismic support plate including a plurality of insertion holes in which the control element drive mechanisms are respectively inserted; and bushings inserted between outer surfaces of the control element drive mechanisms and inner surfaces of the insertion holes. The support plate includes an upper support plate comprising a plurality of first insertion holes, a lower support plate comprising a plurality of second insertion holes at positions corresponding to the first insertion holes, and a connection part connecting the upper support plate and the lower support plate. The connection part includes a support beam vertically extending from an end portion of the lower support plate, an inner flange extending inward from an upper end portion of the support beam, and an outer flange extending outward from the upper end portion of the support beam.

A control drum assembly may include a control drum and a control assembly coupled to the control drum through a drive shaft. The control drum assembly may also include a cage assembly. The cage assembly may include one or more structural supports and one or more modular platforms coupled to the one or more structural supports. The one or more modular platforms may be configured to support one or more components of the control assembly. The cage assembly may also include a base configured to be coupled to a surface of a core and to locate the cage assembly relative to the core.

An elongated control rod guide thimble for a nuclear reactor having a tube-in-tube dashpot design that has circumferential slots in the dashpot walls that align with spaced openings in the guide thimble sheath. The dashpot tube has an end plug with a threaded opening extending axially therethrough which is captured by a thimble screw that extend through an opening in the bottom nozzle and sandwiches an end plug attached to the guide thimble sheath between the dashpot tube end plug and the bottom nozzle.