Abstract:
An end support system is applied to each end of a container for shipping nuclear fuel assemblies in an inner box within the container. The end support system includes a rectilinear metal end frame, a crosspiece with a reinforcing channel along an inside surface of the crosspiece and four arms projecting in a perpendicular direction from the metal end frame for straddling the sides of the container end. By screwing the metal end support system into the wooden framing elements of the container, the integrity of the container ends is maintained during hypothetical accident conditions specified in licensing regulations.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a container for shipping nuclear fuel assemblies and particularly relates to an end support system for the outer wooden container for the nuclear fuel assemblies. 
     Containers are conventionally used to ship nuclear fuel assemblies. Typically, each container includes an inner metal box with two separate channels, each of which carries a single nuclear fuel assembly. Normally, a pair of such nuclear fuel assemblies are arranged in side-by-side relation within the inner metal box. The inner box with the fuel assemblies is typically packaged for shipment within an outer container formed of wooden framing elements, panels interconnecting the framing elements and fillers to prevent movement of the inner box relative to the outer container. The outer container is sealed with metal bolts and is also banded with metal straps. 
     It has become significant for meeting both domestic and international licensing requirements that the integrity of the outer container not be compromised as a result of certain drop and fire tests required by various licensing agencies. For example, licensing regulations require 4-foot and 30-foot drop tests in which the inner metal box must be completely contained within the wooden outer container during the drop tests. Recent drop tests have demonstrated failure of certain prior outer wooden containers to meet the requirements of these drop tests. Specifically, the inner metal box must not break out of or breach the outer wooden container during the drop tests. In preliminary tests, however, it has been observed that the ends of the wooden outer container do break out and no longer provide containment for the inner metal box actually containing the nuclear fuel assemblies. The wooden end frames at the ends of the wooden outer container appear particularly vulnerable to damage and, in certain cases, have broken away from the wooden container, exposing the inner metal box. Accordingly, there is a need for end support systems for nuclear fuel shipping containers which can absorb energy during the drop tests and contain damage to the container ends such that the shipping containers comply with various regulatory licensing requirements. 
     BRIEF SUMMARY OF THE INVENTION 
     In accordance with a preferred embodiment of the present invention, there is provided an end support system for a nuclear fuel assembly shipping container which sufficiently maintains the integrity of the wooden container ends to meet the requirements of licensing regulations. To accomplish the foregoing, each end support system includes a metal end frame for overlying the wooden framing elements forming the ends of the wooden shipping container. It will be appreciated that the ends of the wooden container comprise rectilinear end frames formed of wooden framing elements, typically 2×4s, each having a panel secured to the inside surface of the end frame. The end panels are conventionally formed of plywood. The wooden end frame is secured to longitudinally extending wooden structural framing elements formed along the sides, top and bottom of the container. Each end support system hereof includes a metal end frame formed of top, bottom and side metal plates secured to one another forming a rectilinear frame. A metal crosspiece extends between opposed plates, e.g., the side plates, and carries a reinforcing member engageable with the end panel of the container to reinforce the panel. Additionally, opposite ends of the reinforcing member engage the edges of the wooden framing members at opposite sides of the wooden end frames. With each metal end frame overlying the wooden end framing elements and secured thereto, for example, by a plurality of metal screws, the wooden end frame is substantially reinforced. 
     Additionally, at least four arms formed of metal plates are secured to the metal end frame. The arms extend in a perpendicular direction from the metal end frame for overlying opposite sides of the container along the longitudinally extending wooden structural framing elements. The arms, like the end frame, are secured to the wooden framing elements, for example, by a plurality of metal screws. The metal end frame and lateral support arms thus constitute an end support system for each of the opposite ends of the wooden container. Each end support system reinforces a container end ensuring its integrity and prevents breach of the container end sufficiently to comply with licensing regulations. 
     In a preferred embodiment according to the present invention, there is provided an end support system for a container for shipping nuclear fuel, comprising first and second elongated metal plates generally parallel to and spaced from one another and third and fourth metal plates generally parallel to and spaced from one another, the third plate being secured at opposite ends to ends of the first and second plates and the fourth plate being secured at opposite ends to opposite ends of the first and second plates thereby forming a generally rectilinear metal end frame, an elongated metal cross-plate secured at opposite ends to the third and fourth plates, respectively, at locations intermediate ends of the third and fourth plates, the cross-plate extending generally parallel to the first and second plates and lying generally in a plane defined by the metal end frame, a metal reinforcing member secured to the cross-plate and projecting from one side thereof and generally out of the plane, the member being located intermediate the opposite ends of the cross-plate and inwardly of the third and fourth plates and at least a pair of metal supports connected to the metal end frame and extending generally perpendicular to the end frame along opposite sides of the metal end frame for securement to the container. 
     In a further preferred embodiment according to the present invention, there is provided a container for shipping nuclear fuel, comprising an elongated container body having sides, a top and bottom and opposite ends, a metal end frame for reinforcing each of the opposite ends of the container body, each metal end frame comprising first and second elongated metal plates generally parallel to and spaced from one another and third and fourth metal plates generally parallel to and spaced from one another, the third plate being secured at opposite ends to ends of the first and second plates and the fourth plate being secured at opposite ends to opposite ends of the first and second plates thereby forming the metal end frame in a generally rectilinear configuration, an elongated metal cross-plate secured at opposite ends to the third and fourth plates, respectively, and at locations intermediate ends of the third and fourth plates, the cross-plate extending generally parallel to the first and second plates and lying generally in a plane defined by the metal end frame, a metal reinforcing member secured to the cross-plate and projecting from one side thereof and generally out of the plane, the member being located intermediate the opposite ends of the cross-plate and inwardly of the third and fourth plates, at least a pair of supports connected to the metal end frame and extending generally perpendicular to the end frame along opposite sides of the metal end frame for securement to the container, the metal end frames being secured, preferably by a plurality of metal screws, to the container body ends, respectively, with the supports straddling opposite sides of the container body ends. 
     In a still further preferred embodiment according to the present invention, there is provided a container for shipping nuclear fuel, comprising an elongated container body having sides, a top and bottom and opposite ends, a metal end frame for overlying and reinforcing each of the opposite ends of the container body and lying in a plane, the ends and the sides of the container body being formed at least in part of wooden framing elements, a reinforcing member secured to the metal end frame and projecting from one side of the metal end frame and generally out of the plane, the member being located intermediate opposite edges of the metal end frame, at least a pair of metal supports connected to the metal end frame and extending generally perpendicular to the metal end frame along opposite sides of the metal end frame for securement to the container, each of the metal end frame and supports being secured to the wood framing elements along the ends and sides of the container body, respectively, with the supports straddling opposite sides of the container body ends, the reinforcing member engaging at least a portion of the container body to reinforce the container body. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of a shipping container for nuclear fuel assemblies having end support systems constructed in accordance with a preferred embodiment of the present invention applied to opposite ends of the container; 
     FIG. 2 is a perspective view thereof; 
     FIG. 3 is a view similar to FIG. 2 with portions broken out illustrating in part the interior of the wooden outer container and illustrating an end support system hereof broken out from the end of the container; and 
     FIG. 4 is a perspective view of an end support system constructed in accordance with a preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, particularly of FIGS. 1 and 3, there is illustrated a container, generally designated  10 , for shipping unclear fuel assemblies. Container  10  includes a container body  11  containing an interior metal box, not shown, in which a pair of fuel assemblies (also not shown), each including fuel rods and mechanical hardware, are disposed in side-by-side relation to one another. The inner metal box is confined within container  10 . The top and sides of the container body  11  include panels  12  and  14 , preferably formed of plywood, and a bottom  16  (FIG.  3 ). The top, bottom and sides are lined along the interior of container  10  by honeycomb structures  18  and foam pads  20  to confine the inner metal box within container  10 . Container  10  also includes exterior structural wooden framing elements. For example, elongated wooden 2×4s  22  and  24  are provided along the top and sides, respectively, of the container. Wooden planks  26  preferably form the bottom  16  of the container. Skids  27  (FIGS. 2 and 3) are also located below the container bottom to facilitate lifting the container, e.g., by a forklift. 
     The ends of container  10  also include rectilinear end frames  29  (FIG. 3) formed of wooden framing elements. For example, each rectilinear end frame  29  is preferably formed of a pair of vertical wooden 2×4s  30  spaced from one another and a pair of horizontal 2×4s  32  forming the top and bottom framing elements of the wooden end frame. Additionally, a panel, for example, a plywood panel  34  is secured to the wooden end frame  29  along the inside end surface of the wooden elements  30  and  32 . The construction of the container  10  as illustrated including the wooden framing elements, plywood panels, strapping, honeycomb and foam panels and wooden end frames is conventional except for the container end support system which will now be described. 
     An end support system, generally designated  36 , is applied in accordance with the present invention to the opposite ends of the container  10  to reinforce the container ends and to ensure sufficient structural integrity to meet the required drop tests of the licensing regulations. Referring to FIGS. 3 and 4, each end support system  36  comprises a metal end member or frame  38  including first and second metal plates  40  and  42  extending generally parallel to and spaced from one another. Each metal end frame  38  also includes third and fourth metal plates  44  and  46  which are generally parallel to and spaced from one another. Plates  44  and  46  are secured at their opposite ends to the metal plates  40  and  42 . For example, the third plate  44  may be welded at its ends to the ends of the first and second plates  40  and  42 , respectively. The fourth plate  46  may be welded to the opposite ends of the first and second plates  40  and  42 , respectively, forming a generally rectilinear end frame lying in a plane. As illustrated, the plates  40  and  42  are horizontal for extending along the top of the container at its end face, while plates  44  and  46  are vertical for extending along the opposite sides of the container  10  at its end face. 
     A metal crosspiece  48  also extends between the two side plates  44  and  46 . The metal crosspiece  48  overlies the side plates  44  and  46  and is preferably welded thereto. A reinforcing member  50 , preferably in the form of a channel, is secured along the inside face of crosspiece  48  and terminates short of the ends of crosspiece  46 , for purposes described hereafter. 
     Metal supports extend in a generally perpendicular direction to said metal end frame for securing said metal end frame to said container end. At least two supports extend along opposite sides of container  10  for this purpose and, preferably, each such support comprises a pair of support arms. For example, four support arms  52 ,  54 ,  56  and  58  extend from the corners of the metal end frame  36  in a direction generally perpendicular to the plane of the end support frame. The arms comprise metal plates for extending along the sides of the container  10  in overlying relation to the wooden framing elements forming the sides of container  10 . The arms lie in planes parallel to the container sides. As illustrated in FIG. 4, the metal plates  40 ,  42 ,  44  and  46  and arms  52 ,  54 ,  56  and  58  have a plurality of preformed holes, for example, holes  60 , for receiving screws to screw the end support system  36  to the wooden end frames  24 ,  26 ,  29 ,  30  and  32  of the wooden container  10  as illustrated in FIG.  3 . 
     To apply an end support system  36  to an end of the container  10 , the system  36  is disposed on the container end with the plates  40  and  42  overlying the wooden top and bottom framing elements  32  and plates  44  and  46  overlying the wooden side framing elements  30 . The arms  52 ,  54 ,  56  and  58  extend along opposite sides of the container overlying portions of the elongated wooden framing elements  16  and  24 . Note (in FIG. 2) that the upper edge of the end support assembly  36 , i.e., the metal plate  40 , lies below the cover for the outer container  10 . Additionally, it will be appreciated that the arms  52 ,  54 ,  56  and  58  straddle the sides of container  10 . 
     With the end support assembly  36  applied to the end of the container, a series of screws are passed through the openings  60  of the metal end support  36  to secure it to the container end. The screws are preferably flathead 8×80 mm screws with ribs under the screw head. It will be appreciated that the screw openings  60 , as illustrated in FIG. 4, along arms  52 ,  54 ,  56  and  58 , are formed in an alternating pattern of a pair of openings followed by a single opening along the lengths of the arms. This minimizes any tendency to split the wooden framing elements and affords a securement to the wood. 
     Upon review of FIG. 2, it will be appreciated that, in final securement, the reinforcing member  50 , i.e., the channel, is disposed between the wooden side framing elements  30  with its opposite ends butting against the inside edges of framing elements  30  to reinforce elements  30 . Additionally, the channel has a depth, in the longitudinally direction of the container, the bear against the end panel  34 . The channel thus affords reinforcement to both the side wooden framing elements  30  and to the panel  34 . Because of the structural relationship of the plates, crosspeice and arms and the plurality of metal screws used to secure the plates and arms of the metal end frame to the end of the container, structural integrity of the end of the container is maintained and assured within the requirements of the drop tests mandated by nuclear regulatory licensing requirements. As illustrated, container  10  not only has the end support assemblies at opposite ends but is banded, e.g., by bands  28 , at longitudinally spaced intervals which also assists in maintaining the integrity of the outer container. 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.