Patent Number: 
Section: claims

1. An apparatus for transporting and/or storing high level radioactive waste comprising:an overpack body having an outer surface and an inner surface forming an internal cavity about a longitudinal axis;a base enclosing a bottom end of the cavity;a plurality of inlet ducts in a bottom of the overpack body, each of the inlet ducts extending from an opening in the outer surface of the overpack body to an opening in the inner surface of the overpack body so as to form a passageway from an external atmosphere to a bottom portion of the cavity;a columnar structure located within each of the inlet ducts, the columnar structures dividing each of the passageways of the inlet ducts into first and second channels that converge at the openings in the inner and outer surfaces of the overpack body, wherein for each inlet duct a line of sight does not exist between the opening in the inner surface of the overpack body and the opening in the outer surface of the overpack body;a lid enclosing a top end of the cavity; anda plurality of outlet ducts, each of the outlet ducts forming a passageway from a top portion of the cavity to the external atmosphere. 2. The apparatus of claim 1 wherein the lid comprises the outlet ducts, each of the outlet ducts extending from an opening in the inner surface of the lid to an opening in the outer surface of the lid. 3. The apparatus of claim 1 wherein the columnar structures have a longitudinal axis, wherein the longitudinal axis of the columnar structures are substantially parallel with the longitudinal axis of the overpack body. 4. The apparatus of claim 1 wherein for each inlet duct, the opening in the inner surface of the overpack body is aligned with the opening in the outer surface of the overpack body so that: (i) a first reference plane that is perpendicular to the longitudinal axis of the overpack body intersects both the opening in the inner surface of the overpack body and the opening in the outer surface of the overpack body; and (ii) a second reference plane that is parallel with and includes the longitudinal axis of the overpack body intersects both the opening in the inner surface of the overpack body and the opening in the outer surface of the overpack body. 5. The apparatus of claim 1 wherein the columnar structures have a longitudinal axis, the first and second channels collectively surrounding a circumference of the longitudinal axis of the columnar structures. 6. The apparatus of claim 5 wherein the longitudinal axis of the columnar structures are substantially parallel with the longitudinal axis of the overpack body. 7. The apparatus of claim 1 wherein the first and second channels are curved. 8. The apparatus of claim 1 wherein the overpack body comprises an inner shell and an outer shell concentrically arranged so that a gap exists between the inner and outer shells, the gap filled with a radiation shielding material. 9. The apparatus of claim 1 wherein for each inlet duct, the opening in the inner surface of the overpack body is aligned with the opening in the outer surface of the overpack. body so that a first reference plane that is perpendicular to the longitudinal axis of the overpack body intersects both the opening in the inner surface of the overpack body and the opening in the outer surface of the overpack body. 10. The apparatus of claim 9 further comprising a hermetically sealed canister for containing high level radioactive waste positioned within the cavity so that the first reference plane also intersects the canister. 11. The apparatus of claim 1 further comprising a hermetically sealed canister for containing high level radioactive waste positioned within the cavity so that a bottom surface of the canister is in surface contact with a top surface of the base. 12. The apparatus of claim 11 wherein the cavity has a transverse cross-section that accommodates no more than one of the canisters. 13. The apparatus of claim 1 wherein the inlet ducts have a width and a height that is at least three times the width. 14. The apparatus of claim 1 wherein the base is a baseplate connected to the overpack body. 15. The apparatus of claim 1 wherein the overpack body comprises at least six of the inlet vents arranged in a circumferentially spaced and axi-symmetric manner.