Patent Number: 
Section: abstract

A system, method and apparatus for providing additional radiation shielding to a ventilated cask for holding high level radioactive materials. The invention utilizes a tubular shell that is ancillary to the ventilated cask that circumscribes the ventilated cask to add radiation shielding protection while improving heat removal by natural convective air flow. Because the tubular shell and cask are non-unitary and slidably separable from one another, crane lifting capacity is not affected. In one aspect, the invention is an apparatus for providing additional radiation shielding to a cask holding high level radioactive materials comprising: a tubular shell extending from an open bottom end to an open top end, the tubular shell having an inner surface that forms a cavity about a longitudinal axis; a plurality of primary apertures forming passageways through the tubular shell and circumferentially arranged in a spaced-apart manner about the tubular shell; a plurality of secondary apertures forming passageways through the tubular shell and circumferentially arranged in a spaced-apart manner about the tubular shell; and an annular seal coupled to the tubular shell and extending from the inner surface of the tubular shell; wherein the secondary apertures are located at an axial height above the annular seal and the primary apertures are located at an axial height below the annular seal.