Abstract: A locking ring holds a control rod drive housing tube of a nuclear power plant when a pressure chamber having a contact wall is pressurized. The contact wall faces the control rod drive housing tube presses against it when the pressure chamber is pressurized. The locking ring can lock a threaded nut after it has been screwed onto the control rod drive housing tube. In a method for securing a threaded nut of a control rod drive housing tube of a nuclear power plant in the vicinity of the threaded nut, a body is attached to the control rod drive housing tube, as a result of a contact surface of the body engaging the control rod drive housing tube. A contact surface of the pressure chamber is pressed onto the control rod drive housing tube when the pressure chamber is pressurized.

Abstract: A tube plug for closing a defective heat exchanger tube includes a hollow conical portion having a closed free end and a hollow cylindrical portion merging fluidly with the hollow conical portion without a step. The hollow cylindrical portion has an outer surface with an outside diameter being smaller than the inside diameter of the heat exchanger tube to be closed. The outer surface of the hollow cylindrical portion has a roughened region to be expanded into sealing contact with the inner surface of the heat exchanger tube. The roughened region has a peak-to-valley height of substantially between 0.05 and 0.2 mm. A device is disposed in the hollow cylindrical portion and/or the hollow conical portion for positioning and locking a pulling tool.

Abstract: A twist-proof mechanical connecting assembly includes first and second components. The first component has a recess formed therein with a groove in the form of at least one pocket. A connecting element in the form of a bolt penetrates the first component and is secured to the second component for interconnecting the components. The bolt has a polygonal head including a safety cup embedded in the recess. At least part of the safety cup is outwardly bent into the at least one pocket for locking the safety cup to the first component and securing the connecting element against loosening.