Patent Number: 
Section: claims

1. A dry storage cask for safely storing hazardous nuclear material when one or more air inlets have been fully or partially blocked to an extent that insufficient air flows into the air inlets and through the cask for adequate cooling of the hazardous nuclear material, the cask comprising:a cylindrical metal canister having a top, bottom, and sidewall, the canister containing hazardous nuclear material;a cylindrical concrete overpack containing the metal canister with the hazardous nuclear material, the overpack having a top, bottom, and sidewall, the overpack having an inside surface that is spaced from an outer surface of the canister to create an annular region that permits flow of air between the surfaces;an overpack air inlet near the bottom of the overpack that can communicate air from an outside environment into the annular region;an overpack outlet vent near the top of the overpack that can communicate air from the annular region to the outside environment; anda thermal divider insert extending through the outlet vent and through the annular region, the thermal divider insert configured to: (a) permit two separate air flows upwardly through the annular region and outwardly through the respective vent; and (b) permit two separate and opposite air flows through the respective vent and the annular region, the two air flows including an inward air flow into the vent and then into the annular region and an outward air flow out of the annular region and then out of the vent;wherein the thermal divider insert comprises:a planar horizontal radial plate extending through the overpack outlet vent, the radial plate having a curvature along its inside and outside edges that corresponds to a curvature associated with the overpack outlet vent, the plate establishing a lower air flow region and an upper air flow region within the overpack outlet vent, the lower air flow region for inward air flow from the outside environment, the upper air flow region for outward air flow to the outside environment; anda curved vertical plate extending downwardly at a right angle from the inside edge of the radial plate, the curved vertical plate having a curvature that corresponds to a curvature associated with the annular region, the curved vertical plate establishing an outer annular region and an inner annular region, the outer annular region enabling the inward air flow from the lower air flow region within the vent, the inner annual region enabling the outward air flow to the upper air flow region of the vent. 2. The cask of claim 1, wherein the curved vertical plate extends a substantial vertical distance through the annular region, the substantial distance being at least half of the vertical length of the annular region. 3. The cask of claim 1, wherein a first air flow is vertically below a second air flow in the outlet vent. 4. The cask of claim 1, wherein the thermal divider insert is substantially made of metal. 5. A cask for safely storing hazardous nuclear material when one or more air inlets have been fully or partially blocked to an extent that insufficient air flows into the air inlets and through the cask for adequate cooling of the hazardous nuclear material, the cask comprising:a cylindrical metal canister having a top, bottom, and sidewall, the canister containing hazardous nuclear material;a cylindrical concrete overpack containing the metal canister with the hazardous nuclear material, the overpack having a top, bottom, and sidewall, the overpack having an inside surface that is spaced from an outer surface of the canister to create an annular region that permits flow of air between the surfaces;an overpack air inlet near the bottom of the overpack that can communicate air from an outside environment into the annular region;an overpack outlet vent near the top of the overpack that can communicate air from the annular region to the outside environment; anda thermal divider insert, the thermal divider insert comprising:a planar horizontal radial plate extending through the overpack outlet vent, the radial plate having a curvature along its inside and outside edges that corresponds to a curvature associated with the overpack outlet vent, the plate establishing a lower air flow region and an upper air flow region within the overpack outlet vent, the lower and upper air flow regions for outward air flow to the outside environment when the air inlet is not blocked, the lower air flow region for inward air flow from the outside environment and the upper air flow region for outward air flow to the outside environment when the air inlet is blocked; anda curved vertical plate extending downwardly at a right angle from the inside edge of the radial plate, the curved vertical plate having a curvature that corresponds to a curvature associated with the annular region, the curved vertical plate establishing an outer annular region and an inner annular region, the outer and inner annular regions enabling upward air flow into the lower and upper air flow regions respectively within the vent when the air inlet is not blocked, the inner annual region enabling upward air flow to the upper air flow region of the vent and the outer annular region enabling inward air flow from the lower air flow region within the vent when the air inlet is blocked. 6. The cask of claim 5, wherein the thermal divider insert is substantially made of metal. 7. The cask of claim 5, wherein the curved vertical plate extends a substantial vertical distance through the annular region, the substantial distance being at least half of the vertical length of the annular region. 8. A cask for storing hazardous nuclear material, comprising:a canister having a top, bottom, and sidewall, the canister containing hazardous nuclear material;a concrete overpack comprising:the canister with the hazardous nuclear material, the overpack having a top, bottom, and sidewall, the overpack having an inside surface that is spaced from an outer surface of the canister to create an annular region that permits flow of air between the surfaces;an overpack air inlet near the bottom of the overpack that can communicate air from an outside environment into the annular region;an overpack outlet vent near the top of the overpack that can communicate air from the annular region to the outside environment; anda thermal divider means for establishing: (a) when the air inlet is unblocked, two separate air flows upwardly through the annular region and outwardly from the respective vent; and (b) when the air inlet is blocked, two separate and opposite air flows through the respective vent and the annular region, the two air flows including an inward air flow into the vent and then into the annular region and an outward air flow out of the annular region and then out of the vent;wherein the thermal divider means comprises in structure:a planar horizontal radial plate extending through the overpack outlet vent, the radial plate having a curvature along its inside and outside edges that corresponds to a curvature associated with the overpack outlet vent, the plate establishing a lower air flow region and an upper air flow region within the overpack outlet vent, the lower and upper air flow regions for outward air flow to the outside environment when the air inlet is not blocked, the lower air flow region for inward air flow from the outside environment and the upper air flow region for outward air flow to the outside environment when the air inlet is blocked; anda curved vertical plate extending downwardly at a right angle from the inside edge of the radial plate, the curved vertical plate having a curvature that corresponds to a curvature associated with the annular region, the curved vertical plate establishing an outer annular region and an inner annular region, the outer and inner annular regions enabling upward air flow into the lower and upper air flow regions respectively within the vent when the air inlet is not blocked, the inner annual region enabling upward air flow to the upper air flow region of the vent and the outer annular region enabling inward air flow from the lower air flow region within the vent when the air inlet is blocked. 9. The cask of claim 8, wherein the canister and thermal divider means are substantially made of metal and wherein the overpack is substantially made of concrete. 10. The cask of claim 8, wherein the sidewall associated with the canister and the overpack is generally cylindrical in shape. 11. The cask of claim 8, wherein the cask comprises a plurality of air inlets, a plurality of air vents, and a plurality of thermal divider means corresponding respectively to the plurality of air vents.