Patent Number: 
Section: claims

1. A system for storing high level radioactive waste comprising:an overpack body having an outer surface and a cavity for storing high level radioactive waste, the overpack body comprising an air inlet vent for introducing cool air into a bottom portion of the cavity;a plurality of plates disposed within a portion of the air inlet vent in a spaced apart manner, each of the plates extending from a first end proximate the outer surface of the overpack body to a second end, adjacent ones of the plates spaced apart a first distance at the first ends of the plates and a second distance at the second ends of the plates, the first distance being greater than the second distance; andan overpack lid comprising an air outlet vent enclosing a top end of the cavity. 2. The system of claim 1 wherein a line connecting the first ends of the plates forms a first reference circle having a first diameter and a line connecting the second ends of the plates forms a second reference circle having a second diameter, the first diameter being greater than the second diameter. 3. The system of claim 1 wherein the distance between the adjacent ones of the plurality of plates continuously decreases from the first ends of the plates to the second ends of the plates. 4. The system of claim 1 wherein the air inlet vent comprises an air inlet plenum in the spaces between the plurality of plates and an air inlet passageway that extends from the air inlet plenum to an opening in a floor of the cavity. 5. The system of claim 4 wherein the air inlet plenum extends substantially horizontally from an opening in the outer surface of the overpack body to a terminal end and wherein the air inlet passageway extends upwardly from the air inlet plenum to the opening in the floor at an oblique angle relative to a vertical axis of the overpack body. 6. The system of claim 5 wherein the air inlet passageway circumferentially surrounds the vertical axis of the overpack body. 7. The system of claim 1 wherein the air inlet vent comprises an air inlet plenum that extends substantially horizontally from an opening in the outer surface of the overpack body and an air inlet passageway that extends obliquely from the air inlet plenum in a direction away from a vertical axis of the overpack body. 8. The system of claim 7 wherein the overpack body extends along a first vertical axis, and wherein a second vertical axis that is parallel to the first vertical axis intersects both the air inlet plenum and the air inlet passageway. 9. The system of claim 1 wherein each of the plurality of plates is formed of steel. 10. A system for storing high level radioactive waste comprising:an overpack body extending along a vertical axis and having an outer surface and a cavity for storing high level radioactive waste, the cavity having an open top end and a floor;an air inlet vent for introducing cool air into the cavity, the air inlet vent configured so that aerodynamic performance of the air inlet vent is substantially independent of an angular direction of a horizontal component of an air-stream applied to the outer surface of the overpack body; andan overpack lid positioned atop the overpack body to enclose the open top end of the cavity, an air outlet vent in the overpack lid for removing warmed air from the cavity, the air outlet vent configured so that aerodynamic performance of the air outlet vent is substantially independent of an angular direction of a horizontal component of an air-stream applied to the outer surface of the overpack body. 11. The system of claim 10 further comprising a plurality of plates disposed within a portion of the air inlet vent, each of the plates extending along a reference line that is tangent to a first reference circle having a center point coincident with the vertical axis of the overpack body. 12. The system of claim 10 further comprising a plurality of plates disposed within a portion of the air inlet vent in a spaced apart manner, each of the plates extending from a first end proximate the outer surface of the overpack body to a second end, adjacent ones of the plates spaced apart a first distance at the first ends of the plates and a second distance at the second ends of the plates, the first distance being greater than the second distance. 13. The system of claim 12 wherein a line connecting the first ends of the plates forms a first reference circle having a first diameter and a line connecting the second ends of the plates forms a second reference circle having a second diameter, the first diameter being greater than the second diameter. 14. The system of claim 12 wherein the distance between the adjacent ones of the plurality of plates continuously decreases from the first ends of the plates to the second ends of the plates. 15. The system of claim 12 wherein the air inlet vent comprises an air inlet plenum in the spaces between the plurality of plates and an air inlet passageway that extends from the air inlet plenum to an opening in the floor of the cavity. 16. The system of claim 14 wherein the air inlet plenum extends substantially horizontally from an opening in the outer surface of the overpack body to a terminal end and wherein the air inlet passageway extends upwardly from the air inlet plenum at an oblique angle away from the vertical axis of the overpack body.