Abstract: The plugs are used to close the main steam lines of a boiling-water reactor when the reactor is shut down for maintenance, testing and refueling. The plug utilizes an elongated rubber member which is compressed by axial compression in order to form a seal which will hold the plug in place despite the presence in the steam line of substantial isolation valve test pressures which might force the plug out. Preferably, plates covering portions of the rubber are used to provide a long-lasting solid surface to grip the inside wall of the pipe. A device is provided for the remote installation of the plug so as to minimize the exposure of workers to radioactivity in the reactor vessel. The installation device includes remotely controllable structure for compressing the rubber member of the plug. In one embodiment, the compression structure includes a set of impact wrenches for turning a nut on each of several bolts which are used to compress the rubber member of the plug.

Abstract: The method of transferring radioactive material into and out of the cask comprises positioning a tank with an open end in a well. Then a cask having a passage for moving radioactive material into and out of the cask is placed in the tank through the opening in the tank. The tank opening is then sealed to the cask relative to the well without sealing the passage relative to the well to prevent water filled into the well from leaking into the tank. Then the well is filled with water above the seal, and radioactive material is then moved through the water in the well through the passage into the cask. The tank may be filled with demineralized water from a separate source to pressurize the space in the tank on the other side of the seal from the well to prevent water in the well from entering the tank.