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 fuel assembly (1) for a nuclear power plant includes at least one hollow rod (9, 9a,9b, 9c). The hollow rod is a control rod guide tube (9) of the fuel assembly (1) for the control rod assembly or an instrumentation tube. Each rod (9) is adapted to be filled with one or more containers (38) filled with material to be activated. The fuel assembly further comprises a damping element (36, 36a, 36b, 36c) at the lower end (32) of the hollow rod (9, 9a,9b, 9c).

A fuel assembly (1) for a nuclear power plant includes at least one hollow rod (9, 9a,9b, 9c). The hollow rod is a control rod guide tube (9) of the fuel assembly (1) for the control rod assembly or an instrumentation tube. Each rod (9) is adapted to be filled with one or more containers (38) filled with material to be activated. The fuel assembly further comprises a damping element (36, 36a, 36b, 36c) at the lower end (32) of the hollow rod (9, 9a,9b, 9c).