Cask assembly for transporting radioactive material of different intensities

An improved cask assembly for forming a cask that is adapted to transport radioactive materials of a particular activity is disclosed herein. The cask assembly comprises an outer container having an opening leading to its interior, and a plurality of inner shield inserts, each of which includes an inner wall whose shape is substantially complementary to the shape of the interior of the outer container and which is insertable therein to form a cask. The exterior walls of the inner shield inserts are formed from different shielding compositions, such as depleted uranium or lead, and are also of different thicknesses. The particular shield inserted within the interior of the outer container is chosen to match the intensity and type of radiation emitted by the waste to be transported so that the assembled cask hold a maximum amount of the particular material to be transported without exceeding a surface radiation of 200 millirems at any point. To facilitate the insertion and removal of the shield inserts, the closure opening is at least as wide as the width of its interior. Either a screw-type closure means of a breech-lock closure means is used to seal the container opening.