Patent Number: 
Section: description

The overpack and internal components of the fuel assembly containment and transport system of this invention is illustrated in FIG. 1. A fuel assembly 24 is figuratively shown closely surrounded by the elongated inner liner 18. The inner liner 18 is shown separated into two halves 22 and 20 so the inner liner can more easily be positioned around the fuel assembly prior to loading into the overpack 10. Though the liner 18 is shown in a clamshell design, preferably split in two equal half sections 20 and 22, it should be appreciated that the liner 18 can be separated into two or more sections of equal or unequal circumferential lengths without departing from the scope of this invention. Desirably, the mating interfaces of the interior liner sections 20 and 22 include complementary keyways to facilitate the positioning of the liner sections 20 and 22 around the fuel assembly 24. The liner 18 is preferably constructed from stainless steel with an external circumferential shape and size that is designed to be closely received within the tubular overpack 10. The interior of the liner 18 is either stamped or machined to closely conform to the outer envelope of the fuel assembly 24. A boron sleeve 16 is inserted between the inner liner 18 and the overpack 10 prior to loading of the inner liner. Alternately, the exterior surface of the inner liner 18 can be coated with boron, e.g., through flame deposition or other coating techniques. As another alternate or supplement to the boron sleeve 16, boron-silicate can be poured into a void space in the inner liner 18 between the inner wall of the liner 18 that mates with the outer surface of the fuel assembly 24 and the outer surface of the liner 18 that is closely received within the overpack 10. Still another alternate is to attach plates formed () out of boron-silicate or borated stainless steel to the inside of the inner liner 18. The overpack 10 is an elongated tubular member whose walls are preferably formed from two coaxially positioned stainless steel shells of approximately xe2x85x9 inch thickness. Other wall thicknesses can be employed that will satisfy the strength requirements. However, greater wall thickness will add to the weight of the overpack 10. Preferably, each shell is welded or otherwise manufactured to have a continuous, seamless circumference. In this embodiment, as an example without intending to be limited, a three inch thick layer of close cell polyurethane is interposed between the shells in a closely packed arrangement and preferably the inside shell is formed from a stainless steel sheet impregnated with boron, though it should be appreciated that both shells can be formed from boron impregnated stainless steel or another moderator other than boron can be employed for this purpose. Though the overpack is shown with a circular cross-section, other geometries can be used, e.g., an oval or rectangular geometry, though a circular geometry has some structural advantages. The overpack is fitted with a number of axially spaced circumferential ribs 12 which add circumferential rigidity to the shells that form the walls of the overpack 10. Separate shockmount attachments points 14 can be provided along an external axial rail 28 or the shockmount attachment points can be provided directly on the circumferential ribs 12. Ball bearings 26 are figuratively shown in dotted form and represent a friction reducing mechanism that is employed to assist loading of the inner liner 18 into the overpack 10. The friction reducing mechanisms can be ball bearings on either the interior surface of the overpack 10 or the exterior surface of the liner 18 or a telescoping railing arrangement that can be fixedly built into the interior wall of the overpack 10 and detachably connected to the liner 18. It should also be noted that the sections 20 and 22 of the liner 18 can be clamped together once they are positioned around the fuel assembly 24. FIG. 2 illustrates the overpack 10 enclosed by two endcaps 36 which can be affixed by bolts or a quick hinge and wingnut attachment once the inner liner containing the fuel assembly is loaded. The overpack 10 is shown supported within a birdcage-like frame 30 that is formed from a plurality of axially-spaced circumferential straps 32 that are fixedly connected, such as by welding, to circumferentially-spaced and axially oriented rails 34. The end locations 38 are formed from angle straps. In this arrangement, the external frame is shown with a square cross-section though it should be appreciated that other geometries, such as a circular cross-section can be employed. The overpack 10 is supported within the frame 30 by at least one shock absorber mechanisms 40. The shock absorber support can be, for example, part number J-5735-64, supplied by Lord Corporation, Mechanical Products Division, 2000 West Grandview Boulevard, Erie, Pa. 16514. FIGS. 4A-4E illustrate different support arrangements within the birdcage frame 30 that can be used to support the overpack 10. In FIG. 4A, the overpack 10 is suspended from the midpoint of the sidewalls of the birdcage frame 30 on diametrically opposite sides of the overpack 10. In FIG. 4B, a single slightly different shockmount support secures the overpack 10 to one sidewall of the birdcage frame 30. In FIG. 4C, four shockmount supports respectively suspend the overpack 10 from the midpoints of the sidewalls of the birdcage frame 30. In FIG. 4D, three shockmount supports 40 suspend the overpack 10 from the midpoint of three of the sidewalls of the birdcage frame 30, and in FIG. 4E, the overpack 10 is suspended from four shockmounts 40 respectively attached to the intersection points of the sidewalls of the birdcage frame 30. Thus, it can be appreciated that other support arrangements can be configured without departing from the scope of this invention. FIG. 3 illustrates a car transport 42 that can be used to load the liner 18 into the overpack 10 once the liner 18 has been positioned over the fuel assembly. The sidewalls 46 of the car 42 are aligned with the outer frame 30 which aligns the cradle 44 holding the liner 18 with the axis of the overpack 10. The liner 18 can then be translated axially over rollers in the base of the loading car 42 into the overpack 10 where the frame 30 and car 42 are supported in the horizontal position. Alternatively, the frame 30 can be oriented in a vertical position and a winch 50 can control the cable 48 which is tied to the end of the car 42 to slowly lower the liner 18 into the interior of the overpack 10. Different fuel assembly configurations can be accommodated by supplying liners with different interior geometries to be complementary with the envelope of the fuel assemblies. In its basic form, the invention is a clamshell type fuel assembly package that is inserted in an overpack tube container. An external suspension system and birdcage frame then support the tube overpack. This design allows for a very simple, low cost, lightweight replacement to current fuel transport casks. The overpack provides the versatility to carry many different pressurized water reactor fuel designs as well as many fuel types. The overpack can carry clamshells configured for boiling water reactor fuel assemblies and other nuclear products. While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular embodiments disclosed are meant to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof.