Patent Number: 042788927
Section: description

SPECIFIC DESCRIPTION The drawing shows a radiation-shielding transport or storage receptacle 1 for radioactive wastes, especially for irradiated nuclear reactor fuel elements, which comprises a receptacle shell 2, a bottom 3 and a shielding cover 4. The receptacle shell 2 and the bottom 3 are formed unitarily from cast iron, especially spherolitic cast iron, of cast steel or the like. The shielding cover 4 is provided with a flange which is bolted to a shoulder inset in the mouth of the receptacle. The shell 2 comprises at least one cast-in-place conduit or passage 5 which communicates with the interior of the vessel close to the bottom thereof so that a fluid can be introduced or removed from a fitting 5' at the upper end of the vessel. In the embodiment illustrated and in the best-mode embodiment of the invention, a further passage or conduit 7 is cast in place in the thick wall 2 of the vessel. This conduit 7 opens into the upper end of the interior of the vessel and terminates in a chamber 8 in which a valve 9 is received or into which a valve 9 can be introduced. The conduits 7 and 5 and their valve or valves can be used for circulating a fluid through the interior of the vessel. The valve 9 can also be a pressure-relief valve to which a hose or length of tubing can be connected. As has especially been shown in FIG. 2, the passages 5 and 7 are located in the inner half of the thickness of the wall 2. This permits further passages 10 to be formed in the outer half of the thickness of the wall, the passages 10 extending the full length of the receptacle and along the bottom so that they can be filled with a material of higher radiation-adsorbing cross section, i.e. a so-called moderating material. This has been found to be especially advantageous when the container receives nuclear wastes having a high neutron activity. The passages 10, like the passages 5 and 7, can be closed at the top of the vessel by a safety cover 6 which overlies the shielding cover 4 and is applied after the shielding cover 4 has been bolted in place. The shielding cover 4 has the configuration of a plug to provide the necessary thickness for limiting the passage of radiation out of the interior of the vessel. As is also apparent from the drawing, the exterior of the shell 2 of the vessel is provided with cooling ribs 11 which can run parallel to the generatrix of the vessel wall. The individual cooling ribs 11 are cast unitarily with the wall and can be provided with gaps 12 along their lengths for expansion and contraction. The gaps 12, therefore, subdivide the cooling ribs 11 into elongated sections. According to the present invention, at the upper edge of the vessel wall 2, a continuous upstanding annular welding lip 13 is formed by an upwardly open groove 13' while the safety cover 6 is provided with a corresponding upstanding welding lip 15 along its outer periphery by an upwardly open groove 15'. The lips 13 and 15 are parallel to one another and terminate in a common plane P below the plane P' of the upper surface of the receptacle. The lips 13 and 14 define a welding crevice in which a bead of weldment 17 can be deposited to form the hermetic seal. The lip 13 with the shoulder 13" of the vessel wall 2 provides an annular space 14 in which the cover 6 is received. In the embodiment shown in the drawing, moreover, the weld seam 17 is located outwardly of the fitting 5' and the chamber 8 so that it hermetically seals the passages 5 and 7 as well as the passages 10 if the latter are similarly disposed within the perimeter of this weld seam. Prior to insertion of the cover 4 and the emplacement of the cover 6, water filling the interior of the vessel can be evacuated by the conduit 5. The conduit 5 can, however, be used for other purposes as well. For instance, it can be employed for introducing liquid radioactive wastes into the vessel or for supplying or circulating special coolants to the vessel or for passing a coolant through the vessel to abstract heat from the radioactive wastes contained therein. Any other passages or conduits required for this purpose can also be cast in place within the body of the vessel and closed similarly. As has been shown in FIGS. 1 and 4, the safety cover 6 can be provided with a bore 16 into which can be force-fitted a plug 16' or which can be welded shut. This bore can receive, once the plug 16' or the weldment is removed, a suction line to enable a gas detector to analyze withdrawn gases. When the interior of the vessel is pressurized with helium, the escape of helium into the space below the cover 6 and detected by withdrawal from the passage 16 indicates a failure of the seal between the shielding cover 4 and the remainder of the vessel. As the seal between the shielding cover 4 and the body of the vessel is monitored, any leakage can be detected so that replacement of the shielding cover 4 can be effected or repair of the seal ensured. To this end, the bead 17 of weldment can be simply burned off and the cover 6 removed to effect repair. With replacement of the cover 6, the hermetic seal by the formation of another deposit weld can be re-instituted.