Patent Number: 
Section: claims

1. A system for storing high level radioactive waste comprising:an overpack body extending along a vertical axis and having a cavity for storing high level radioactive waste, the cavity having an open top end and a floor;an overpack lid positioned atop the overpack body to enclose the open top end of the cavity;an air inlet vent for introducing cool air into the cavity, the air inlet vent extending from an opening in an outer surface of the overpack body to an opening in the floor, the opening in the outer surface of the overpack body extending about an entirety of a circumference of the outer surface of the overpack body; andan air outlet vent extending from an opening in a bottom surface of the overpack lid to an opening in an outer sidewall surface of the overpack lid for removing warmed air from the cavity. 2. The system of claim 1 wherein the air inlet vent comprises an air inlet plenum that extends substantially horizontally from the opening in the outer surface of the overpack body to a terminal end and an air inlet passageway that extends from an opening in a top surface of the air inlet plenum to the opening in the floor. 3. The system of claim 2 wherein the air inlet plenum extends substantially horizontally from the outer surface of the overpack body at an axial height below the floor, and the air inlet passageway extends upwardly from the air inlet plenum to the opening in the floor at an oblique angle relative to the vertical axis. 4. The system of claim 2 wherein the opening in the floor is located a first distance from the outer surface of the overpack body and the opening in the top surface of the air inlet plenum is located a second distance from the outer surface of the overpack body, the second distance being greater than the first distance. 5. The system of claim 1 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. 6. The system of claim 1 wherein the air outlet vent comprises a substantially vertical section that extends from the opening in the bottom surface of the overpack lid to a terminal end and a substantially horizontal section that extends from the terminal end of the substantially vertical section to the opening in the outer sidewall surface of the overpack lid. 7. The system of claim 6 wherein the opening in the bottom surface of the overpack lid and the opening in the outer sidewall surface of the overpack lid are annular openings. 8. The system of claim 1 further comprising a hermetically sealed canister for containing the high level radioactive waste positioned within the cavity, an annular gap existing between an outer surface of the canister and an inner wall surface of the overpack body, the annular gap forming an air flow passageway between the air inlet vent and the air outlet vent. 9. The system of claim 8 wherein the opening in the floor is aligned with the canister such that a plane extending parallel with the vertical axis intersects both the opening in the floor and the hermetically sealed canister. 10. A system for storing high level radioactive waste comprising:an overpack body extending along a vertical axis and having a cavity for storing high level radioactive waste, the cavity having an open top end and a floor;an overpack lid positioned atop the overpack body to enclose the open top end of the cavity;an air inlet vent for introducing cool air into the cavity, the air inlet vent extending from an opening in an outer surface of the overpack body to an opening in the floor, the opening in the outer surface of the overpack body extending about an entirety of a circumference of the outer surface of the overpack body;an air outlet vent in the overpack lid for removing warmed air from the cavity; andwherein the overpack body comprises a cylindrical wall, a bottom block disposed within the cylindrical wall, and a base structure at a bottom end of the cylindrical wall, the base structure comprising a base plate and an annular plate arranged in a spaced relation to the base plate to form a first section of the air inlet vent therebetween, the bottom block comprising a columnar portion that extends through a central hole of the annular plate and rests atop the base plate, a second section of the air inlet vent formed within the bottom block and circumferentially surrounding the columnar portion. 11. A system for storing high level radioactive waste comprising:an overpack body extending along a vertical axis and having a cavity for storing high level radioactive waste, the cavity having an open top end and a floor, 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 along a reference line that is tangent to a third reference circle having a center point coincident with the vertical axis; andan overpack lid positioned atop the overpack body to enclose the open top end of the cavity, the overpack lid comprising an air outlet vent for removing warmed air from the cavity. 12. The system of claim 11 wherein each of the plurality of plates extends from a first end that is located proximate to an outer surface of the overpack body to a second end, a line connecting the first ends of the plates forming a first reference circle having a first diameter and a line connecting the second ends of the plates forming a second reference circle having a second diameter, the first diameter being greater than the second diameter. 13. The system of claim 12 where adjacent ones of the plurality of plates are spaced apart by a first distance at the first ends and by a second distance at the second ends, the first distance being greater than the second distance. 14. The system of claim 13 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 11 wherein the air inlet vent comprises an air inlet plenum that extends substantially horizontally from an opening in an outer surface of the overpack body to a terminal end and an air inlet passageway that extends from the air inlet plenum to an opening in the floor, the plurality of plates positioned within the air inlet plenum. 16. The system of claim 15 wherein the air inlet plenum extends substantially horizontally from the opening in the outer surface of the overpack body to the 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 to the vertical axis, the air inlet passageway circumferentially surrounding the vertical axis. 17. A system for storing high level radioactive waste comprising:an overpack body extending along a vertical axis and having a cavity for storing high level radioactive waste, the cavity having an open top end and a floor, the overpack body comprising an air inlet vent for introducing cool air into a bottom portion of the cavity;an overpack lid positioned atop the overpack body to enclose the open top end of the cavity, the overpack lid comprising an air outlet vent for removing warmed air from a top portion of the cavity; andthe air inlet vent comprising a first section that extends substantially horizontally from an outer surface of the overpack body to a terminal end and a second section extending from the first section to an opening in the floor at an oblique angle relative to the vertical axis. 18. The system of claim 17 wherein the second section of the air inlet vent extends from the first section of the air inlet vent to the opening in the floor in a direction away from the vertical axis. 19. The system of claim 17 wherein the opening in the floor is located a first distance from the vertical axis and the terminal end of the first section of the air inlet vent is located at a second distance from the vertical axis, the first distance being greater than the second distance.