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.