Patent Number: 
Section: claims

1. A storage capsule for nuclear fuel rods, the capsule comprising:an elongated body defining a vertical centerline axis, the body comprising an open top end, a bottom end, and sidewalls extending between the top and bottom ends;an internal cavity formed within the body;a lid attached to and closing the top end of the body;an array of axially extending fuel rod storage tubes disposed in the cavity;an upper tubesheet and a lower tubesheet, the upper and lower tubesheets supporting a top end and a bottom end of each storage tube;a top plenum formed between the lid and upper tubesheet, and a bottom plenum formed between the lower tubesheet and the bottom end of the capsule; anda central drain tube extending parallel to the vertical centerline axis between the upper and lower tubesheets, the drain tube in fluid communication with the bottom plenum;wherein each storage tube has a transverse cross section configured and dimensioned to hold no more than one fuel rod;wherein the central drain tube is fluidly isolated from the top plenum by a sealing assembly fluidly coupled between a top end of the drain tube and the lid. 2. The capsule according to claim 1, wherein the central drain tube is supported by the upper and lower tubesheets. 3. The capsule according to claim 1, wherein the top ends of the storage tubes are in fluid communication with the top plenum and the bottom ends of the storage tubes are in fluid communication with the bottom plenum. 4. The capsule according to claim 3, wherein the bottom ends of storage tubes extend below the lower tubesheet into the bottom plenum and rest on a bottom interior surface of the capsule. 5. The capsule according to claim 4, further comprising at least one flow opening formed near the bottom ends of each storage tube. 6. A storage capsule for nuclear fuel rods, the capsule comprising:an elongated body defining a vertical centerline axis, the body comprising an open top end, a bottom end, and sidewalls extending between the top and bottom ends;an internal cavity formed within the body;a lid attached to and closing the top end of the body;an array of axially extending fuel rod storage tubes disposed in the cavity;an upper tubesheet and a lower tubesheet, the upper and lower tubesheets supporting a top end and a bottom end of each storage tube;a top plenum formed between the lid and upper tubesheet, and a bottom plenum formed between the lower tubesheet and the bottom end of the capsule; anda central drain tube extending parallel to the vertical centerline axis between the upper and lower tubesheets, the drain tube in fluid communication with the bottom plenum:wherein each storage tube has a transverse cross section configured and dimensioned to hold no more than one fuel rod;wherein the lid has a solid structure that defines a first gas supply flow conduit in fluid communication with the central drain tube and bottom plenum, and a second gas return flow conduit in fluid communication with the top plenum and storage tubes. 7. The capsule according to claim 1, wherein the lid includes a threaded opening for attaching a lifting assembly for moving and transporting the capsule. 8. A fuel storage system for storing nuclear fuel rods, the system comprising:an elongated capsule defining a vertical centerline axis, the capsule comprising a top end, a bottom end, and sidewalls extending between the top and bottom ends;an internal cavity formed within the capsule;a lid attached to the top end of the capsule, the lid including an exposed top surface and a bottom surface;an upper tubesheet and a lower tubesheet disposed in the cavity;a plurality of vertically oriented fuel rod storage tubes extending between the upper and lower tubesheets;a central drain tube extending between the upper and lower tubesheets;wherein each storage tube has a transverse cross section configured and dimensioned to hold no more than one fuel rod;wherein the lid includes a first gas supply flow conduit in fluid communication with a bottom plenum and a second gas return flow conduit in fluid communication with a top plenum. 9. The storage system according to claim 8, further comprising the top plenum formed between the lid and upper tubesheet, and the bottom plenum formed between the lower tubesheet and the bottom end of the capsule. 10. The storage system according to claim 8, wherein the gas supply flow conduit includes a gas supply port formed in the top surface of the lid and a gas supply outlet formed in the bottom surface of the lid. 11. The storage system according to claim 10, further comprising a sealing assembly fluidly coupling the gas supply outlet in the lid to the central drain tube for forming a leak tight connection. 12. The storage system according to claim 11, wherein the sealing assembly included a spring-biased sealing member configured to engage the gas supply outlet in the lid. 13. The storage system according to claim 12, wherein the sealing member is formed of an elastomeric or metallic material. 14. The storage system according to claim 11, further comprising a gas outlet extension tube extending downwards from the bottom surface of the lid, the extension tube fluidly coupled to the sealing assembly. 15. The storage system according to claim 14, wherein the central drain tube and gas extensions tube are coaxially aligned with the vertical centerline axis of the capsule. 16. The storage system according to claim 9, further comprising a peripheral skirt extending around a perimeter of the bottom surface, the skirt resting on the upper tubesheet to define the top plenum when the lid is attached to the capsule. 17. The storage system according to claim 8, wherein the lid includes a gas supply port formed in the top surface of the lid in fluid communication with the gas supply flow conduit, and a gas return port formed in the top surface of the lid in fluid communication with the gas return flow conduit, the gas supply and return ports each configured for mounting a remote valve operating assembly thereto for forced gas dehydration of the fuel rods. 18. The storage system according to claim 8, wherein lid is fully inserted into the top end of the capsule so that the lid does not protrude substantially above the top edge of the capsule.