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 comprising an annular air inlet plenum and an annular air inlet passageway, the annular air inlet plenum extending radially inward from an outer surface of the overpack body to the annular air inlet passageway, the annular air inlet passageway extending upward from the annular air inlet plenum to an opening in the floor; andan air outlet vent in the overpack lid for removing warmed air from the cavity. 2. The system of claim 1 wherein the annular air inlet passageway has an inverted truncated cone-shape. 3. The system of claim 1 wherein the annular air inlet plenum circumferentially surrounds the axis. 4. The system of claim 1 wherein the annular air inlet plenum extends horizontally from the outer surface of the overpack body at an axial height below the floor, the annular air inlet passageway extending upward from the air inlet plenum to the opening in the floor at an oblique angle to the vertical axis. 5. The system of claim 1 further comprising a plurality of plates disposed within the annular air inlet plenum, 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 annular air inlet plenum extends from a substantially 360° opening in the outer surface of the overpack body. 7. The system of claim 1 wherein the air inlet vent is 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. 8. The system of claim 7 wherein the air outlet vent is 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. 9. The system of claim 8 wherein the air outlet vent comprises an annular passageway extending from an annular opening in a bottom surface of the overpack lid to an annular opening in an outer sidewall surface of the overpack lid. 10. The system of claim 1 wherein 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 the annular air inlet plenum therebetween, the bottom block comprising a columnar portion that extends through a central hole of the annular plate and rests atop the base plate, the annular air inlet passageway formed within the bottom block and circumferentially surrounding the columnar portion. 11. 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 wail surface of the overpack body, the annular gap forming an annular air flow passageway between the annular air inlet passageway and the air outlet vent. 12. The system of claim 1 wherein the annular air inlet passageway extends from a first end located a first radial distance from the vertical axis to a second end located a second radial distance from the vertical axis, wherein the second radial distance is greater than the first radial distance. 13. 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, the air inlet vent comprising a substantially horizontal annular air inlet plenum that circumferentially surrounds the vertical axis, the substantially horizontal annular air inlet plenum extending radially inward from a substantially 360° opening in an outer surface of the overpack body;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 the cavity; andthe 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. 14. The system of claim 13 wherein the air outlet vent is configured so that aerodynamic performance of the air outlet vent is substantially independent of an angular direction of a horizontal component of an airstream applied to the outer surface of the overpack body. 15. The system of claim 13 wherein the air inlet vent further comprises an oblique annular air inlet passageway and the substantially horizontal annular air inlet plenum is located at an axial height below the floor, the oblique annular air inlet passageway circumferentially surrounding the vertical axis and extending upward from the substantially horizontal annular air inlet plenum to an opening in the floor. 16. 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 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; 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 the annular air inlet plenum therebetween, the bottom block comprising a columnar portion that extends through a central hole of the annular plate and rests atop the base plate, the annular air inlet passageway formed within the bottom block and circumferentially surrounding the columnar portion. 17. The system of claim 13 wherein the air inlet vent and the air outlet vent are substantially axisymmetric. 18. 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 extending from an outer surface of the overpack body to a first radial distance from the vertical axis and a second section extending, from the first radial distance to an opening in the floor at a second radial distance from the vertical axis, the second radial distance being greater than the first radial distance. 19. The system of claim 18 wherein the first section of the air inlet vent is an annular plenum that extends substantially horizontal and the second section is an annular passageway that extends oblique to the vertical axis. 20. The system of claim 19 wherein 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 the annular plenum therebetween, the bottom block comprising a columnar portion that extends through a central hole of the annular plate and rests atop the base plate, the annular passageway formed within the bottom block and circumferentially surrounding the columnar portion.