Patent Number: 
Section: description

The overpack and internal components of the nuclear fuel product containment and transport system of this invention is illustrated in FIG. 1. A tubular container or shell 26 constructed from a material such as aluminum houses a nuclear fuel assembly and is suspended over a V-shaped groove 32 in the overpack 12, supported on shock mounts 28 that are affixed in a recess 30 in an upper wall section of the groove 32 and spaced along the axial length of the lower overpack section 16. The shock mounts can be those identified by part no. J-3424-21, which can be purchased from Lord Corporation having offices in Cambridge Springs, Pa. Angle irons 24 can be used at the corners of the tubular container to spread the load on the container walls. The number and resiliency of the shock mounts are chosen to match the weight of the container, which depends upon the nuclear product being transported within the container 26. The orientation of the lower section 16 of the overpack 12 is fixed by the legs 18 so that the weight of the container 26 holds the container centered in the groove 32. One capped end 22 forms part of the lower overpack support section 16 while a second capped end 20 is formed as an integral part of the top cover 14. The end 20 of the upper overpack segment 14 seals against the lip 21 in the lower support section 16. Similarly, though not shown, the end 22 formed as an integral part of the lower support section 16 seals against a corresponding lip on the upper overpack section 14 in the same manner. Keys 50 on each side of the upper section 14 of the overpack 12 fit in complementary keyways in the lower overpack support section 16 as can be better appreciated from the frontal view shown in FIG. 2. FIG. 2 shows a frontal view of the shipping container system 10 of this invention with the endplate 20 removed. Both the top segment 14 and bottom segment 16 of the overpack 12 are formed from a hollow stainless steel sheet 34, for example, an 11 gauge stainless steel shell filled with polyurethane can be employed. Preferably, in this embodiment the polyurethane has a minimum 3 inch (7.62 cm) thickness. In the preferred embodiment, the hollow channel in the overpack 37 is shaped to substantially conform to the outer profile of the tubular container 26 and the walls of the hollow channel 37 can be lined with a neutron-absorbing material such as a half-inch (1.27 cm) of borosilicate. Alternately, the outer surface of the tubular canister 26 can be lined with a neutron-absorbable material such as an eighth inch (0.318 cm) thick layer of borosilicate or a combination of neutron-absorbing material on the walls of the tubular container 26 and the walls of the hollow channel 37 can be employed. FIG. 2 provides a better view of the recess 30 that the shock mounts 28 are mounted in than can be derived from FIG. 1. Similarly, the keys 50 and keyways 48 that aid in positioning the top Section 14 on the lower support member 16 of the overpack 12 are shown more clearly in FIG. 2. FIG. 3 illustrates an alternative embodiment to that shown in FIG. 2, which omits the layer of neutron-absorbing material 42 on the hollow channel 37 illustrated in FIG. 2 and shows instead the four sides of the tubular container 26 having a eighth inch (0.318 cm) layer of neutron-absorbing material on all four sides. Additionally, the embodiment shown in FIG. 3 includes an approximately half inch (1.27 cm) layer of thermal insulation interposed between the stainless steel shell 34 and the polyurethane 36. In this embodiment, the polyurethane will have a minimum thickness of approximately 2,xc2xd inches (6.35 cm). The top segment 14 of the overpack is latched to the bottom support segment 16 in the preferred embodiment using the latch assembly illustrated in FIG. 4. Both the lip 53 on the upper overpack section 14 and the lip 55 on the lower overpack section 16 include a plurality of axially spaced slots. A latch bar is affixed to either the upper lip 53 or the lower lip 55 in a manner to permit the clamp arm 54 to slide within a corresponding slot in the lip. For example, with the latchbar 56 coupled to the lower lip 55, the clamp arm 54 would protrude through the corresponding slot in a downward direction and have an enlarged protruding end to anchor the latch bar 56 to the lower lip 55. The upper clamp arm 54 can have an L-shape as shown in FIG. 4 so that when the lip 53 is seated over its corresponding clamp arm 54, the latchbar 56 can be moved in a direction into the figure to lock the upper section 14 to the lower section 16 of the overpack 12. The clamp arm 54 can then be secured in that locked position. An external lever can be used to slide the latchbar to an open and closed position with an approximate four-inch stroke desirable. To facilitate the locking and unlocking action, a low friction coating can be applied to the sliding surface. FIG. 5 illustrates a perspective view of an open tubular container 26 with a fuel assembly 74 positioned therein. The fuel assembly 74 is made up of a parallel spaced array of fuel elements 76 that are maintained in space relationship and in position by gridstraps 78, a bottom nozzle 77 and a top nozzle which is not shown. The gridstraps are constructed in an eggcrate design to maintain the spacing between the fuel elements 76 that form flow channels for the reactor coolant to flow through during reactor operation. The fuel assembly 74 is seated on a neoprene or cork rubber bottom pad 72, which is affixed to the bottom 68 of the tubular container 26. The neoprene or cork rubber pad 72 supports and cushions the fuel assembly 74. A similar arrangement is provided above the fuel assembly 74 supported by the top end 70 (shown in FIG. 6) of the tubular container 26. The tubular container 26 has two stationary sides 59 and 62 which are affixed to the bottom 68 and top 70 of the container. The container 26 has two moveable sides 62 and 64 which are hinged to the adjacent edges of the stationary sides 58 and 60 through hinges 66 that rotate around a kingpin 67 (shown in FIG. 6). The two moveable sides are in turn connected, when latched, by similar hinges 66, with the insertion of the kingpin in the hinge forming the latch. In this way, the moveable sides 62 and 64 can be opened from any of the hinged seams to provide access to the interior of the tubular container 26 from a number of different directions to facilitate loading and unloading in different environments that may present obstructions. The tubular container 26 is preferably constructed out of aluminum of a thickness, for example, of 0.375 inches (0.9525 cm) The interior walls of the sides 58, 60, 62 and 64 are covered with an iron ferrite composite sheet, 88 and neoprene or cork rubber pads with magnetic backing 82 are attached and affixed by the magnetic force at the grid elevations to seat the neoprene or cork rubber side of the pads against the outside straps of the grid at the grid elevations. The magnetic coupling on the pads makes them adjustable to accommodate different nuclear fuel component designs. The neoprene or cork rubber pads are not as hard as the material that the grids are constructed of and secures the grids in position when the sides 62 and 64 are in the closed position without damaging the grids and cushions the fuel assembly during transport. The inside of the tubular container 26 can be used to transport other fuel components such as fuel rods separately by employing inserts within the tubular container 26 that will hold those components securely. FIG. 6 provides a better view of the iron ferrite composite sheet 80 and hinged locations. Alternately, clips on the backs of the neoprene or cork rubber pads can be supported in slots at multiple elevations on the interior walls of the sides 58, 60, 62 and 64. Axial adjustment of the pads can be made by moving the pads from slot to slot. FIG. 7 shows a simplified top view of a hexagonal tubular container 26 for transporting hexagonal fuel such as that employed in Russian designed VVER reactors. In this case, there are four stationary sides 58, 59, 60 and 61 with two moveable sides arranged and hingably connected as previously described. In all other respects, the embodiment of the tubular container 26, shown in FIG. 7, is the same as that shown in FIGS. 5 and 6. With the fuel assembly or other nuclear fuel component loaded within the tubular container 26, the moveable sides 62 and 64 can be closed and secured with the kingpins 67 and the tubular member 26 loaded within the V-channel 32 of the lower overpack support section 16. The upper overpack section 14 then can be lowered into engagement with the lower section 16 and the latch 52 can be secured. In this way, the nuclear fuel product can be shipped in the horizontal position in a secure and safe manner. The overpack provides the versatility to carry many different types of fuel components. FIGS. 9 and 10 illustrate another embodiment of the overpack 12. The lower section 16 of the overpack 12 is the same in most respects as that illustrated in FIG. 1, except for the keying of the upper section to the lower section and the front closure 20 shown in FIG. 1. The legs 18 are also different as shown. The upper section 14, shown in the embodiment illustrated in FIGS. 8 and 9, is split into sections 84 and 86 with each section hinged to the lower section 16. When the sections 86 and 84 are closed, the mating surfaces 88 and 90 intersect along their keyway and can be latched. The front closure 92 is generally rectangular and formed as an integral part of one of the top half sections 84. When closed, the front closure 92 seats within a sealing groove 94 in the front of the lower section 16. Lifting lugs 96 are provided for transferring the cask to and from a transport vessel. The swinging top sections 84 and 86 of the embodiment illustrated in FIGS. 8 and 9 make it easier to open and close the overpack 12 and load the tubular container 26. FIG. 10 shows the overpack 12 as illustrated in FIGS. 8 and 9 with a hexagonal tubular container or member 26xe2x80x2 for transporting a hexagonal fuel assembly. In all other respects, the overpack 12 and tubular container are the same as described above. 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.