Patent Number: 
Section: description

FIG. 1 illustrates an embodiment of the system of the present invention, a below grade cask transfer facility (xe2x80x9cCTFxe2x80x9d) 2. As used herein, the term xe2x80x9cbelow gradexe2x80x9d means elevationally below ground surface level 6. Generally, CTF 2 comprises below grade opening 3, circular platform, and at least two jacks 5. In the illustrated embodiment, there are three high-capacity jacks 5 (only two are visible in the illustration). While jacks 5 are used to vertically move circular platform 4, circular platform 4 can be vertically moved by any type of pneumatic or mechanical lifting device capable of lifting the applied load. Referring to FIG. 2, CTF 2 is constructed so that receiving cask 9 having lid 22, top surface 12 (FIG. 5) and base 13 can be placed on and supported by platform 4. Receiving cask 9 can be a storage cask or a transport cask. Receiving cask 9 is placed on platform 4 when platform 4 is in a fully raised position. When platform 4 is in the fully raised position, top surface 8 (FIG. 1) of platform 4 is below grade. When receiving cask 9 is placed thereon, base 13 of receiving cask 9 is also below grade, preferably about 40 inches. Platform 4 is capable of vertical movement, including lowering receiving cask 9 into opening 3. Referring to FIGS. 3 and 4, platform 4 can be lowered to a fully lowered position while supporting receiving cask 9. CTF 2 is designed so that when platform 4 is supporting receiving cask 9 and in the fully lowered position, receiving cask 9 is in a position wherein a majority of its height is below grade. Preferably, all of receiving cask 9 will be below grade except about 30 inches. When all but about 30 inches of receiving cask 9 is below grade, top surface 12 (FIG. 5) of receiving cask 9 is at an ergonomic height to facilitate cask operations. Referring to FIGS. 1 and 2, in the illustrated embodiment, CTF 2 further comprises a shell 15 that forms the walls of opening 3. In constructing CTF 2, shell 15 is placed in an oversized hole in the ground 6 and leveled approximately flush with the ground surface 6. The area surrounding shell 15 can be backfilled with soil and/or concrete to secure shell 15 in the ground 6 and to provide extra radiation shielding. As such, shell 15 establishes the inner form for a concrete pour. The bottom of shell 15 may be open-bottomed to allow the inside bottom to be filled with concrete and leveled or equipped with setdown structure 16. In the illustrated embodiment, shell 15, opening 3, and receiving cask 9 are cylindrical. However, shell 15, opening 3, and receiving cask 9 can be made to be any shape or size. Preferably, shell 15 has a cross-section that is shaped and sized so that there is a tight clearance between shell 15 and receiving cask 9 when receiving cask 9 is resting on platform 4. Having a tight clearance between shell 15 and receiving cask 9 provides a safeguard against receiving cask 9 tipping over during a seismic event. When there is a tight clearance between shell 15 and receiving cask 9, receiving cask 9 can not tip over during a seismic event when receiving cask 9 is resting on platform 4 in the fully lowered position. When receiving cask 9 is resting on platform 4 in the fully raised position, base 13 of receiving cask 9 is below grade. Thus, a portion of receiving cask 9 forms a tight clearance with shell 15, providing seismic stabilization and decreasing the chance that receiving cask 9 will tip over during a seismic event. Additionally, shell 15 is designed to have a plurality of extension spaces 17 for mounting jacks 5. Extension spaces 17 provide space outside the main circumference of shell 15 so that jacks 5 do not contact or interfere with receiving cask 9 when it is lowered. Because jacks 5 are mounted to shell 15, shell 15 provides the support for jacks 5 during lifting and lowering of platform 4 (and any applied load). Shell 15 also provides lateral support of platform 4 during operations. While in the illustrated embodiment, shell 15 is used to form the walls of opening 3, CTF 2 can be constructed without employing shell 15. In such a situation, opening 3 is formed by digging a hole in ground 6 that approximates the desired size of opening 3. In FIG. 1, platform 4 is a circular platform having hole 7. Hole 7 provides personnel access to the underside of the circular platform. Alternatively, platform 4 can be a frame or other structure capable of supporting receiving cask 9 containing loaded canister 11. As illustrated, platform 4 has top surface 8 with cask positioning plates 14 located thereon. Cask positioning plates 14 act as key ways to help center receiving cask 9 on platform 4 and within opening 3. Platform 4 is designed to approximate the shape and size of receiving cask 9, with projections 16. Platform 4 is a rugged steel weldment that provides support for receiving cask 9 and transmits lateral loads to shell 15 during seismic events. Platform 4 also transmits the lifting and controlled lowering forces supplied by jacks 5 to receiving cask 9. This is accomplished by projections 16 that form lifting locations for jacks 5. Projections 16 ride inside extension spaces 17. Jacks 5 are located just outside the main diameter of the shell 15 in extension spaces 17. Jacks 5 are supported at their top end in extension spaces 17. Jacks 5 comprise guide rods 25 that guide the movement of platform 4. Because jacks 5 are connected to shell 15 only at their top, vertical guide rods 25 are in constant tension under loading conditions, which eliminates the danger of xe2x80x9cbuckling.xe2x80x9d When jacks 5 lower platform 4 and any load supported thereby to the fully lowered position, platform 4 contacts and rests on setdown structure 16. At this position, setdown structure 16 bears the entire load of platform 4 (and any load supported thereby), freeing jacks 5 and vertical guide rods 25 from supporting the applied load (FIG. 3). Jacks 5 are coupled mechanically or electronically to keep platform 4 level during lifting operations. Jacks 5 provide sufficient lift force to raise the platform 4 when loaded with receiving cask 9 and are overrated to provide an extra safety margin. Jacks 5 contact the underside of projections 16 of platform 4 in extension spaces 17. All parts of jacks 5 and their drives 18 are located below grade to prevent interference with delivery of transfer cask. Jacks 5 and their drives 18 are situated in shallow steel or concrete-lined trenches and covered with removable, recessed covers 19. Drives 18 and their control system provide the power and control for jacks 5. An electronic feedback system monitors the position of each jack 5 to maintain synchronous movement of platform 4. Redundant position switches (not illustrated) limit the travel beyond established points (independent of the drive and control system). Level monitoring switches independently monitor the platform level and shut off jack drives 18 if an out-of-level condition is detected. The control station is located near CTF 2 but is sufficiently far away for the operator to oversee the movement operations. Power and control wires going from the control station to drives 18 are located underground to prevent interference and damage during cask operations. CTF 2 is used to facilitate the transfer of a canister of spent nuclear fuel from a transfer cask to a receiving cask in a more safe, efficient, and cost effective manner. Referring to FIGS. 1 and 2, in utilizing CTF 2 for the transfer, empty receiving cask 9 is placed on platform 4 when platform 4 is in the fully raised position. As receiving cask 9 is placed on platform 4, cask positioning plates 14, located on the top surface 8 of platform 4, act as key ways to help center receiving cask 9 in CTF 2. Referring to FIGS. 3 and 4, platform 4 (with receiving cask 9 positioned thereon) is then lowered to a fully lowered position, leaving top surface 12 (FIG. 5) of receiving cask 9 approximately 30 inches above ground surface level 6. A set of lateral restraints 20 can then be installed between receiving cask 9 and shell 15 for sites that are prone to severe earthquakes. Lateral restraints 20 act like hard bumpers to limit the radial movement of receiving cask 9 during a seismic event. Referring to FIGS. 5 and 6, lid 22 (FIG. 4) of receiving cask 9 is then removed. In the illustrated embodiment, mating device 21 is then attached to top surface 12 of receiving cask 9. Mating device 21 provides the connection between transfer cask 10 and receiving cask 9. While in the illustrated embodiment, mating device 21 is used to provide a connection between transfer cask 10 and receiving cask 9 (FIG. 7), it is possible to connect transfer cask 10 directly to receiving cask 9. The method of connection is dictated by the specific designs of the transfer cask and receiving cask used and does not affect the scope of the present invention. Referring to FIG. 7, in the illustrated embodiment, transfer cask 10, containing a loaded and sealed canister 11, is then raised, placed into, and rigidly secured to mating device 21. Base 23 (shown partially in section) of transfer cask 10 is removed using mating device 21, leaving an unobstructed pathway for canister 11 to be lowered into receiving cask 9. Referring to FIG. 8, canister 11, using slings 24 attached to top surface 27 of canister 11, is then fully lowered into receiving cask 9 until canister 11 contacts bottom 26 of receiving cask 9. Slings 24 are disconnected and empty transfer cask 10 and mating device 21 are removed (not illustrated). Lid 22 is then placed back on and secured to receiving cask 9. Receiving cask 9 is then raised by platform 4 of CTF 2 to the fully raised position. Receiving cask 9 is then lifted and removed from CTF 2 by cask transporter 28 (FIG. 9) or some other lifting device such as a crane. The loading operations for transferring a loaded canister from a transfer cask to a receiving cask summarized above aid in understanding the operations of CTF 2. Actual operations and cask-specific equipment at a particular nuclear site may vary from those described herein. The foregoing discussion discloses and describes merely exemplary embodiments of the present invention. As will be understood by those skilled in this art, the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the disclosure of the present invention is intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.