| 摘要 |
1,196,269. Shielded containers. NATIONAL LEAD CO. 8 Sept., 1967 [9 Sept., 1966], No. 41161/67. Heading B4Q. A shipping container for radio-active material has a non-circular cross-section cavity 137, shown as a square cross-section, defined by stainless steel plates 130, 132, 134, 136 disposed within a stainless steel cylindrical inner shell 94. The space between the cavity 137 and the shell 94 is filled with primary shielding material consisting of corner shield means 140 and shielding 142. To unify the shielding effect the corner shield means 140 are of a more dense material than that of the shielding 142 and, as shown, the means 140 are of cast uranium and the shielding 142 is of lead. Safety shielding 96 is provided in the space between the shell 94 and an outer shell 22 of stainless steel having cooling fins 28. The shielding 96 comprises a series of spaced cylindrical sheets of steel with the intervening spaces filled with a shielding material having a lower melting point than that of the primary shielding, the preferred material being a lead antimony alloy. Normally, the series of spaced cylindrical sheets serves to improve the thermal conduction to facilitate removal of the radio-active decay heat. In the event of an external fire, however, the lead antimony alloy escapes through relief plug means 100 and the reflecting surfaces of the series of cylindrical sheets forms a barrier to the radiant heat. Each end of the container is closed by closure means, one such closure 240 being shown in Fig. 6. This closure comprises lead shielding 238 and safety shielding 244 similar to the shielding 96. A relief valve 270 is connected through a conduit 262, 260 to the cavity 137. |
