Patent Number: 048511552
Section: summary

BACKGROUND OF THE INVENTION This invention relates to an apparatus for treating radioactive materials by solidifying them, and more particularly to a solidification processing apparatus for solidifying radioactive waste materials in powdery, granular or indefinite forms in a treating vessel to form stable solidified bodies suitable for keeping, storing or disposing. Various kinds of radioactive waste materials produced in nuclear power installations such as nuclear power stations are usually stored in the respective installations. Various kinds of solidification processing methods have been proposed or actually used for reducing volume of the waste materials and ensuring their stability in consideration of saving storage spaces as well as safety, transportation and future disposal of the waste materials. There have been known solidification processing methods for the radioactive waste materials, such as solidifying them with cement or solidifying them by mixing with melted asphalt or plastic material or the like. As an improved method of the above methods, it has been recently proposed to melt radioactive waste materials so as to be solidified in glass or together with melted glass or to solidify radioactive waste materials by cement glass. In the method of solidifying radioactive waste materials with cement, asphalt or plastic material, however, it is necessary to knead the radioactive waste materials with the solidifying agent such as the cement, asphalt or plastic material after the waste materials have been crushed or pulverized. In the solidification method by the cement glass, moreover, it is necessary to make the radioactive waste materials into pellet forms or to knead the materials with the solidifying agent after crushing or pulverizing the materials. These operations are not preferable as handling operations for the radioactive waste materials, because for example crushers, kneading extruders or pellet forming machines are needed. In the method of solidifying the radioactive waste materials together with glass, the materials are once melted and solidified in glass, or the materials are mixed with melted glass and then solidified together with the glass. Therefore, melting installations required for melting the materials and the glass are very expensive in operation. Moreover, in the case of waste material apt to thermally decompose, an additional installation is needed for treating gases produced in the decomposition. SUMMARY OF THE INVENTION It is a principal object of the invention to provide a solidification processing apparatus for radioactive waste materials, which eliminates all the disadvantages of the prior art and which is able to simply solidify radioactive waste materials in a vessel such as a drum can without any pretreatment by pouring a solidifying agent into the materials and heating and curing the materials at low temperatures. In order to achieve the object the solidification processing apparatus for radioactive waste materials according to the invention comprises a tank for a solidifying agent for solidifying the radioactive waste materials, a waste material vessel connected to said tank for the radioactive waste materials, pouring control means for controlling pouring of said solidifying agent into said vessel, and a heating and curing chamber for heating said vessel by indirect heating means after pouring said solidifying agent onto said waste materials in said vessel to polymerize and set said solidifying agent, thereby solidifying said radioactive waste materials. With this arrangement, the solidifying agent superior in impregnation is poured into a vessel filled with radioactive waste materials, whose poured amount is controlled by the pouring control means. After completion of pouring the solidifying agent into the vessel, it is heated indirectly by indirect heating means in order to avoid deflagration if the solidifying agent is combustible. The solidifying agent is polymerized and set in a relatively short time by promoting the polymerization reaction of the agent to solidify the radioactive waste materials with stability. In a preferred embodiment, the pouring control means comprises valve means provided in a pipe connecting the tank and the vessel, and a vacuum deaerating unit connected to the vessel for promoting the pouring of the solidifying agent. With this arrangement, the pouring of the solidfying agent into the vessel is controlled by the valve means, while gases in the vessel are removed by the vacuum deaerating unit to bring the vessel into a negative pressure, thereby enabling the solidifying agent to be poured into the vessel with high efficiency. The pouring control means preferably comprises impregnation detecting means for controlling the valve means in response to signals from a sensor in the vessel. In this manner, the amount of the solidifying agent impregnated in the radioactive waste materials in the vessel is able to be detected. At a moment when a predetermined amount of the solidifying agent has been impregnated, the valve means is closed to stop the pouring of the solidifying agent. In another embodiment, the apparatus further comprises a recovery unit for recovering gases exhausted from the tank for the solidifying agent, the vacuum deaerating unit and the heating and curing chamber to recover vaporized solidifying agent in the gases, and a filter for purifying gases after recovering the vaporized solidifying agent. With the arrangement, the vaporized solidifying agent is adsorbed and condensed in the recovery unit for reuse, thereby reducing the running cost and preventing the contamination of environment due to exhausted agent. In a further embodiment, the indirect heating means comprises control means for controlling polymerization reaction by controlling heating temperature in response to detected temperatures of outer surfaces of the vessel and in the heating and curing chamber. The atmosphere for heating and curing is controlled in a substantially constant condition. Moreover, the condition of the polymerization reaction of the solidifying agent in the vessel is detected from the outside of the apparatus. The invention will be more fully understood by referring to the following detailed specification and claims taken in connection with the appended drawings.