Patent Number: 052251144
Section: description

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS As shown in FIG. 1 of the drawing, the claimed apparatus is a multipurpose container 10 that comprises a polymeric inner container 12 disposed within a concrete outer shell 14. The polymeric inner container 12 is preferably composed of linear polyethylene, i.e., high density polyethylene in which the polyethylene chains are relatively straight and closely aligned. The polymeric inner container 12 has, in general, an inner surface 16 and an outer surface 18. The polymeric inner container has a primary lid, 20, also composed of polymer. The primary lid 20 contains an opening 22. The primary lid 20 is fastened to the polymeric inner container by heat welding, a well-known process. A smaller secondary lid, 24, is used to cover the opening 22. Also contained in the primary lid 20 is a high efficiency particulate filter, or HEPA filter 26, which allows gases to vent into and out of the container, while shutting in radioactive particles. The concrete outer shell 14 also has a lid 28, an inner surface 30, and an outer surface 32. The polymeric inner container 12 is typically manufactured in any of a number of manners, such as by injection molding, or by heat welding individual sheets of polyethylene together. Preferably, however, the polymeric inner container is manufactured by a rotomolding process. The concrete outer shell 14 is typically made through a precasting process, and is metal reinforced. The concrete may be reinforced with epoxy coated wire mesh or reinforcement bar. The concrete may also have various additives admixed into it during the concrete blending procedure. Such additives may include various high range water reducing agents, or pozzolanic materials such as fly ash and silica fume. The concrete may also be a reinforced, for instance, with amorphous metal fibers obtained from SOGEFIBRE of France. Such fibers are generally produced by quenching a liquid metal jet onto a cooled wheel that is rotating at a high speed. The resulting metal fibers are noncrystalline in structure, and thus highly corrosion resistant. Various hooks and lifting pins can be embedded into the concrete outer shell during its casting. For instance, body lift pins 34 can be provided in order to allow the container to be lifted. Lid lift pins 36 can similarly be cast into the lid 28. A pair of forklift notches 38 and 40 are preferably cast into the bottom of the concrete outer shell, into which the forks of a forklift can be inserted in order to allow the container to be safely lifted. Finally, in order to provide protection from radiation, shielding 42 (not shown) can be placed within the container 10, for instance between each outer surface 18 of the inner container 12 and the adjacent inner surface 30 of the outer shell 14. This shielding 42 can be fabricated from steel, iron, lead, high density concrete, or combinations thereof. An alternative embodiment of the claimed apparatus, differing only in that its shape is cylindrical, is shown in FIG. 2. Turning now to FIG. 3, the claimed multipurpose container is seen as it exists during the first stage of the claimed process, the processing and storage stage. Prior to shipment of the multipurpose container to the processing location, various processing devices (not shown) are placed into the inner container 12. These devices may include mixers or filter elements that are used in order to further treat low-level radioactive waste once it is introduced into the container. Such treatment may include mixing the waste within the container while adding chemical conditioners in order to form a stabilized waste form, or suctioning through a filter element in order to evacuate water from the container while leaving the radioactive waste behind. Such treatment devices and procedures are generally known. After the processing devices are positioned inside of the container, the lid 20 is heat welded into place. With this step, the processing devices are essentially sealed into the container, where they remain. The secondary lid 24, however, is not yet sealed into place over the opening 22. At the processing location, a fillhead 44 is placed into the opening 22 in the secondary lid 20. The fillhead 44 is supported by a process lid 45, which rests on the top of the concrete outer shell 14. The fillhead serves several purposes. First, waste material is introduced through the fillhead into the inner container 12. Additives, such as those used to condition the waste for stabilization, may also be added through the fillhead into the inner container. The fillhead also provides the necessary connections to the various processing devices that are located within the inner container 12. For instance, suction lines that run from a dewatering pump into the fillhead are connected at the fillhead onto pipes inside of the inner container, which are in turn connected to the various filter elements. After the waste has been introduced into the container and processed, the fillhead 44 is withdrawn from the opening 22, which is then covered and sealed with the secondary lid 24. The sealing of the lid is typically carried out at the processing location. In order to simplify the attachment of the secondary lid 24 onto the lid 20, a wire, coated with polyethylene, may be positioned around the outer edge of the secondary lid 24. After the secondary lid 24 is positioned in place over the opening 22, the ends of the wire are connected to an electrical current. This causes the wire to heat up, melting the polyethylene coating, and welding the secondary lid 24 onto the lid 20. The waste is now fully sealed within the inner container 12. Turning now to FIG. 4, the lid 28 is now positioned onto the concrete shell 14, resting on a lip 46, also shown in FIG. 1. The lid 28 can be grouted into place at this time by inserting grout into the gap 29 between the lid 28 and the outer shell 14. Alternatively, the lid can be left ungrouted, if it is likely that it will be removed at some future time, for instance if a final inspection of the inner container is to be conducted immediately prior to disposal. The multipurpose container is now in condition to be either stored on site, or to be transported to another location for disposal. Turning now to FIG. 5, a manner of securing the filled multipurpose container 10 onto a flatbed vehicle 48 is shown. The filled container 10 is place onto the bed 50 of the vehicle 48, being held generally in place by a number of chocks 52. A beam 54 is passed through each forklift notch 38 and 40, extending slightly out of the notch. An impact limiter 56 is placed over the top of the container 10, and is held in place by a number of cables 58, each of which passes from the impact limiter to one of the beams 54. A container restraining band 60, preferably made of performed steel, is placed around the multipurpose container, with its ends bolted together tightly. A number of tie-down cables 62 extend from the container restraining band 60 to the bed 50 of the vehicle. The cables 58 and 62 are each provided with a tensioning apparatus 64, such as a ratchet binder. After the filled container has been transported to the disposal site, it is disposed of in any of the known manners. The multipurpose container is appropriate for burial, for storage in warehouses, or for any of a number of other methods for storing or disposing of low-level radioactive waste. In light of the above disclosed process, it is readily apparent that it is not necessary to remove the inner container 12 from the outer concrete shell 14 at any time during the process. Thus, the concrete shell, either alone or in combination with a radiation shield, can be relied upon at all times to provide structural support for the polyethylene inner container. As a result, the inner container can be constructed with thinner walls than would be required if it had to removed from the outer shell at any time. Thus, while a freestanding polyethylene container full of liquid waste would typically have a wall thickness of at least one half inch, the inner container of the present multipurpose container can be as thin as one quarter inch. Furthermore, since there is typically very little gap between the inner container and the outer shell of the multipurpose container, the amount of waste that can be contained within a given stored volume is considerably greater than for a typical container that is placed inside of a concrete overpack prior to disposal, in which a considerable gap is left between the container and overpack. While the preferred embodiments of the claimed method and apparatus have been described, and various alternative embodiments have been suggested, it should be understood that other embodiments could be devised based upon the principles of the claimed method and apparatus of this invention that would remain within the spirit of the invention and the scope of the appended claims.