Patent Number: 
Section: claims

1. A storage capsule for storing and drying 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 peripheral sidewalls extending between the top and bottom ends;an internal cavity formed within the body;a lid attached to the top end of the body;an array of axially extending fuel rod storage tubes disposed in the cavity and extending between the lid and bottom end of the body, each storage tube having a transverse cross section configured and dimensioned to hold no more than one fuel rod;a gas supply flow conduit and a gas return flow conduit each extending internally through the lid between top and bottom surfaces of the lid;wherein the cavity and the gas supply and return flow conduits collectively form a closed gas flow loop configured for circulating gas through the storage tubes;an upper tubesheet and a lower tubesheet, the storage tubes each extending in parallel between the upper and lower tubesheets;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 fluidly coupled at its top end to the gas supply flow conduit in the lid;wherein the central drain tube is fluidly isolated from the top plenum and in fluid communication with the bottom plenum. 2. The capsule according to claim 1, wherein the gas supply and return flow conduits each follow a separate and fluidly isolated multi-directional path through the lid configured with no straight line of sight between respective inlets and outlets of each flow conduit to prevent neutron streaming. 3. The capsule according to claim 2, wherein each of the gas supply and return flow conduits each follow a rectilinear flow path through the lid and include at least one horizontal section and at least one vertical section. 4. The capsule according to claim 1, wherein the top plenum is in fluid communication with the gas return flow conduit in the lid and the bottom plenum is in fluid communication with the gas supply flow conduit in the lid. 5. The capsule according to claim 4, wherein the top plenum is fluidly isolated from gas supply flow conduit. 6. The capsule according to claim 1, wherein the top plenum is fluidly isolated from the bottom flow plenum. 7. The capsule according to claim 1, wherein bottom ends of each storage tube extend below the lower tubesheet into the bottom plenum and rest on an interior surface at the bottom end of the capsule body, and further comprising at least one flow opening formed near the bottom ends of each storage tube. 8. The capsule according to claim 1, wherein bottom ends of each storage tube extend below the lower tubesheet and top ends of each storage tube terminate at the upper tubesheet. 9. The capsule according to claim 8, wherein the bottom ends of each storage tube rest on an interior surface at a bottom end of the cavity of the capsule body. 10. The capsule according to claim 9, further comprising at least one flow opening formed adjacent to the bottom ends of each storage tube. 11. The capsule according to claim 1, wherein the lid has a solid structure between opposing top and bottom surfaces of the lid with an internal configuration that defines the gas supply flow conduit and the gas return flow conduit which extend therebetween.