Patent Number: 
Section: claims

1. A system for transferring a radioactive payload comprising:a first shielding container comprising a first cavity and a removable shielding lid, the radioactive payload located within the first cavity:a shield-gate apparatus comprising a body, a passageway extending along an axis through the body from a first opening in a top surface of the body to a second opening in a bottom surface of the body, and one or more movable shielding gates, the one or more shielding gates movable between: (1) a closed state in which the one or more shielding gates block the passageway; and (2) an open state in which the one or more shielding gates do not obstruct the passageway;the shield-gate apparatus positioned atop the first shielding container, the removable shielding lid having a bottom portion having a transverse cross-section that substantially corresponds to a transverse cross-section of the opening in the top surface of the body of the shield-gate apparatus in both size and shape. 2. The system of claim 1 wherein the shield-gate apparatus comprises first and second shielding gates, the first and second shielding gates are slid in opposite transverse directions during movement between the open and closed states. 3. The system of claim 1 wherein the shield-gate apparatus comprises a top plate comprising the first opening, a bottom plate comprising the second opening, and first and second wall plates connecting the top and bottom plates to form a gate chamber in which the one or more gates are mounted. 4. The system of claim 1 wherein the shield-gate apparatus further comprises one or more flanges extending from the body for securing the shield-gate apparatus to the first container. 5. The system of claim 1 wherein the removable shielding lid is movable through the passageway between: (1) a first position in which the removable shielding lid is below the shield-gate apparatus and encloses an opening of the first cavity; and (2) a second position in which a bottom surface of the removable shielding lid is located within the passageway at a height above the one or more shield gates. 6. The system of claim 1 further comprising a shielding block, positioned atop the body of the shield-gate apparatus to enclose the first opening. 7. The system of claim 6 further comprising:the shielding block having a central axis that is substantially coaxial with the axis of the passageway; anda retaining feature that prevents relative transverse movement between the shielding block and the shield-gate apparatus while allowing relative rotation between the shielding block and the shield-gate apparatus about the central axis. 8. The system of claim 7 wherein the retaining feature comprises an inner side wall of a retaining ring that protrudes from the top surface of the body, the inner side wall of the retaining ring circumferentially surrounding the first opening of the body, the top surface of the body comprising an annular ledge that extends from the first opening to the inner side wall of the retaining ring, the shielding block in surface contact with and supported by the annular ledge. 9. The system of claim 7 wherein the shielding block comprises one or more tool ports extending through the shielding block and a removable shielding plug disposed within each of the one or more ports, and wherein at least one of the one or more tool ports is offset from the central axis of the shielding block. 10. The system of claim 9 wherein at least one of the one or more tool ports is aligned with the central axis of the shielding block. 11. The system of claim 9 further comprising:a pressure vessel positioned in the first cavity, the pressure vessel comprising a pressure vessel body and a removable pressure vessel lid secured to the pressure vessel body by a plurality of fasteners that are offset from a central axis of the pressure vessel, the radioactive payload disposed within the pressure vessel, the central axis of the pressure vessel substantially coaxial with the axis of the passageway;the plurality of fasteners spaced from the central axis of he pressure vessel by a first radial distance; andthe at least one of the one or more tool ports offset from the central axis of the shielding block by a second radial distance that is substantially equal to the first radial distance. 12. The system of claim 1 further comprising:a transfer cask comprising a transfer cask shield-gate and a structure protruding from a bottom surface of the transfer cask shield-gate; andthe shield-gate apparatus comprising a retaining feature that interacts with the structure to prevent relative transverse movement between the transfer cask and the shield-gate apparatus. 13. A system for facilitating work within a cavity of a first shielding container containing a radioactive payload, the system comprising:a shield-gate apparatus comprising a body, a passageway extending along an axis through the body from a first opening in a top surface of the body to a second opening in a bottom surface of the body, and one or more movable shielding gates, the one or more shielding gates movable between: (1) a closed state in which the one or more gates block the passageway; and (2) an open state in which the one or more gates do not obstruct the passageway, the shield-gate apparatus positioned atop the first shielding container;a shielding block positioned atop the body of the shield-gate apparatus to enclose the first opening; anda retaining feature that prevents relative transverse movement between the shielding block and the shield-gate apparatus while allowing relative rotation between the shielding block and the shield-gate apparatus about a central axis of the shielding, block. 14. The system of claim 13 wherein the shielding block comprises one or more tool ports extending through the shielding block and a removable shielding plug disposed within each of the one or more ports, and wherein at least one of the one or more tool ports is offset from the central axis of the shielding block. 15. The system of claim 14 further comprising a tool extending through the at least one of the one or more tool ports that is offset from the central axis of the shielding block. 16. The system of claim 15 further comprising means for rotating the shielding block about the central axis while the shielding block remains in surface contact with the shield-gate apparatus. 17. The system of claim 14 further comprising:a pressure vessel positioned in the first cavity, the pressure vessel comprising a pressure vessel body and a removable pressure vessel lid secured to the pressure vessel body by a plurality of fasteners that are offset from a central axis of the pressure vessel, the radioactive payload disposed within the pressure vessel, the central axis of the pressure vessel substantially coaxial with the central axis of the shielding block;the plurality of fasteners spaced from the central axis of the pressure vessel by a first radial distance; andthe at least one of the one or more tool ports offset from the central axis of the shielding block by a second radial distance that is substantially equal to the first radial distance. 18. The system of claim 14 wherein at least one of the one or more tool ports is aligned with the central axis of the shielding block. 19. The system of claim 13 wherein the retaining feature comprises an inner side wall of a retaining ring, that protrudes from the top surface of the body of the shield-gate apparatus, the inner side wall of the retaining ring circumferentially surrounding the first opening of the body, the top surface of the body comprising an annular ledge that extends from the first opening to the inner side wall of the retaining ring, the shielding block in surface contact with and supported by the annular ledge. 20. The system of claim 13 wherein the retaining feature comprises a side wall circumferentially surrounding the first opening of the body, an annular ledge extending from the first opening to the side wall, the shielding block in surface contact with and supported by the annular ledge.