Abstract: Apparatus for attenuating vibration of a tube includes a cable disposed in the tube and spaced-apart attenuating assemblies mounted on the cable for frictionally engaging the wall of the tube in order to damp vibration of the tube. The assemblies also add rigidity to the tube in order to stabilize the tube against vibration. Each attenuating assembly comprises two spaced-apart end fittings mounted on the cable. A heat vaporizable insert is interposed between the end fittings for maintaining the end fittings in their spaced-apart relationship until the insert vaporizes. A preloaded coiled spring, which interconnects the end fittings and surrounds the insert, biases the end fittings towards each other after the insert vaporizes. A tubular, flexible and braided sheath, which is interposed between the end fittings, surrounds the spring and has respective ends thereof attached to the end fittings. When the insert vaporizes, the spring biases the end fittings closer together, thereby axially shortening the sheath.

Abstract: Vibration dampener and stiffener apparatus and method for increasing the dampening and the stiffness of a tube subjected to large amplitude flow-induced vibration. The preferred embodiment of the apparatus includes a plurality of flexible braided cables capable of being disposed in the tube for dissipating the vibration energy of the tube as the tube vibrates, the cables having a first end portion and a second end portion. Enclosing the first end portion of the plurality of flexible cables is a rigid cable tip member and enclosing the second end portion of each cable is a rigid cable end fitting. As the tube vibrates due to flow-induced vibration, the vibration energy will be transferred to the cables which will rub together creating frictional heat energy that will radiate from the cables. In this manner, the vibration amplitude of the tube is decreased. Moreover, as the tube vibrates, the rigid cable tip member and the rigid cable end fittings will tend to stiffen the tube.

Abstract: A positioning and locking device for fuel pin to grid attachment provides an inexpensive means of positively positioning and locking the individual fuel pins which make up the driver fuel assemblies used in nuclear reactors. The device can be adapted for use with a currently used attachment grid assembly design and insures that the pins remain in their proper position throughout the in-reactor life of the assembly. This device also simplifies fuel bundle assembly in that a complete row of fuel pins can be added to the bundle during each step of assembly.