Patent Number: 044477309
Section: description

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, a transportation and/or storage container embodying this invention comprises mainly a thick-wall container body 12 of metallic material for containing therein and shielding gamma radiation of radioactive material. Such a container is described in the copending application of Botzem et al, Ser. No. 282,015 filed July 10, 1981, and assigned to the same assignee as this application. The disclosure of that application is incorporated by reference herein. The material of the body 12 desirably is made of cast iron, preferably spherical graphite cast iron. The container body 12 preferably is cylindrical and is provided with a plurality of preferably equally-spaced exterior cooling ribs 62 which may be arranged longitudinally, as shown, or circumferentially. These ribs 62 may be either cast integrally with the body 12 or welded thereto. Extending transversely to and between the ribs 62 and secured to the latter and to the exterior of the container body 12 are bridges or flanges 64 of a height less than that of the cooling ribs. These flanges 64 preferably are cast integrally with the body 12 and ribs 62, or they may be welded in place. The presence of the flanges 64 insures that in the event of the breaking off or cracking off of a cooling rib 62, the line of fracture of such rib is not located at its base but at a distance above such base. This minimizes the possibility that the breaking off or cracking off of a rib 62, which may occur in the event the container is dropped, will extend the fracture into the container body 12, i.e., insures against the continuation of such a crack into the container body. The safe distance of such a rib crack from the container body 12 itself can be insured by the judicious selection of relative heights of the flanges 64 and the ribs 62. Theoretical calculations, and also experiments, have shown that it is desirable to proportion the parts such that the height of the flanges 64 is no more than about two-thirds of the height of the cooling ribs 62 and that the spacing between flanges is no more than about ten times their height. In connection with the foregoing provision for inhibiting the extension of rib fracture cracks into the body 12 of the container, it has been found to be advantageous to provide notches 66 in the cooling ribs 62 in the area of intersection therewith of the flanges 64, as shown in FIG. 4. This construction even better insures against continuation of a rib crack into the body 12 of the container. The bottom of the notches 66 is no deeper than the tops of the flanges 64. Notches 66 of lesser depths are effective for their intended purpose, however, depending upon the specific design and material of the ribs 62 and the flanges 64. Such notches 66 may be molded by a casting operation or formed by a machining operation. In a working example, a cast body container for irradiated nuclear fuel elements taken from a pressurized water reactor, the container having cast on longitudinal cooling ribs and circumferential flanges, may have a flange spacing of the order of about 440 mm and a flange height of about 70 mm. The cooling ribs may have a height of about 240 mm with notches therein, at the location of intersection of the flanges, of a depth of the order of about 95 mm. With these dimensions, potential cracks in the container body 12, occasioned by damage to the cooling ribs, will be avoided. Neutron shielding material (not shown) desirably covers the cylindrical outer surface of the container body 12, preferably being disposed between the cooling ribs 62 in the spaces between the flanges 64 and the ribs.