Patent Number: 049873130
Section: summary

FIELD OF THE INVENTION Our present invention relates to a method of storing radioactive waste and to an apparatus or plant for this purpose. More particularly, the invention relates to the improved shielding radioactive waste container described in the aforementioned copending application and apparatus associated therewith as well as a waste storage method utilizing that container. BACKGROUND OF THE INVENTION A lost concrete shielding container for the retention, storage and disposal of liquid radioactive wastes for a nuclear plant generating electric power is known. The container comprises a vessel having unitary walls and a floor. A lid sealingly closes an open mouth of the vessel and, like the walls and the floor, can be composed of concrete. The container can be filled with radioactive waste which can be mixed with cement or concrete can be poured into the partly filled container to seal the latter. A shield container of this type generally stores the radioactive waste without reduction of volume by vacuum or heating. It is also known to transport and store spent fuel elements in cast iron or steel containers having a wall thickness of at least about 40 centimeters and sufficient, therefore, to provide a substantial shield effect. Generally these containers have heat exchange ribs and are closed by a casting of the same metal as forms the remainder of the container. Such containers have the advantage that they can be used to treat the waste, e.g. by heating them while exhausting vapors generated in them by the heat. In this manner wet but somewhat solid matter filtered from the cooling circuits of a nuclear-power plant can be dried out for permanent disposal in such containers. OBJECTS OF THE INVENTION It is the principal object of the present invention to provide an improved method of and apparatus for the disposal of liquid radioactive wastes which extend the principles of the above-mentioned application. Another object of this invention is to provide a method of and apparatus for the disposal of radioactive waste which utilizes the container of the aforementioned application in a particularly effective and advantageous manner. SUMMARY OF THE INVENTION As has been alluded to above, an important component of the present invention is the shielded container of the above-mentioned copending application. That container can be used for the treatment of radioactive waste, according to the invention and is an upwardly cast-iron vessel having a closed bottom, solid walls unitary therewith and an upwardly open mouth which can be closed by a cast-iron lid which is formed with separate vertically throughgoing intake and outlet passages. Screwthread formations either provided directly on the lid and vessel, or fasteners engaged between them hermetically secure the lid over the mouth. Advantageously, both the lid and the upper rim of the vessel are stepped and interfitted for this purpose. An important element of the shielded container of the invention is a flow deflector aligned inside the vessel underneath the outlet passage and which is formed as a baffle plate so that aspirated gases do not entrain liquid or solid particles from the vessel. A single cover is held by appropriate screwthread formations on the cover over the passages. The vessel of the invention can be relatively thin cast iron, e.g. of a thickness of 8 centimeters, 12 centimeters, or 18 centimeters, for example, so that it is possible to treat the contents of the vessel. The exterior of the vertical wall of the vessel may be free from rib formations and the like so that it can be closely surrounded by a heating mantel or jacket. For drying radioactive wastes, it is merely necessary to heat the outside of the container while applying suction to the outlet passage. The subatmospheric pressure thus created in the vessel allows the water to vaporize at well below 100.degree. C., thereby drying the material with minimal energy and likelihood that potentially radioactive constituents will be evolved and entrained in a vapor state. The flow deflector is preferably a generally horizontal plate underlying and spaced below the outlet passage although the plate can be slightly frustoconical with an upward convergence. The plate is preferably supported by posts from the underside of the lid. The system may also be provided with a tube connected to and extending downwardly in the vessel and forming a downward extension thereof. This is particularly useful when an ion exchange resin is to be introduced into the container in the form of lumps or particles. For maximum shielding the cast-iron vessel is provided with a lead lining. This makes the vessel capable of shielding as much radioactivity as far heavier all-iron vessels. In addition, the overall container weight is not excessive. The method of the invention can comprise the steps of: (a) providing an upwardly open cast-iron vessel having a closed bottom, a solid wall unitary therewith and an upwardly open mouth; (b) closing the mouth by sealingly engaging a cast-iron lid thereof, the lid being formed with separate vertically throughgoing intake and outlet passages and providing in the vessel at least one flow deflector aligned beneath the outlet passage; (c) surrounding the vessel with a heating jacket; (d) introducing into the vessel through the intake passage a radioactive liquid; (e) evacuating the vessel through the outlet passage and simultaneously heating the vessel with the jacket to evaporate liquid from the vessel and form vapors which are withdrawn past the deflector through the outlet passage; and (f) upon completion of filling of the vessel with a residue resulting from the evaporation of liquid from the contents of the vessel, hermetically engaging a cover over the passages. The related apparatus can comprise: a metering vessel receiving radioactive liquid material from a nuclear power plant; at least one treating and storage container connectable to the vessel for receiving the material therefrom, the container being composed of cast iron and having a lid traversed by an inlet passage connectable to the vessel and an outlet passage, and a generally horizontal baffle disposed directly below the inlet passage; a condenser connected to the outlet passage for condensing condensate received therefrom; a suction pump connected to the condenser for evacuating the container through the condenser; and a heating jacket on the container for heating same simultaneously with evacuation of vapors therefrom.