Liquid sodium sulfate waste and spent powdery ion-exchange resin are the major wet low level wastes (LLWs) currently generated at BWR nuclear power stations in Taiwan. They are solidified by cement producing about 1,100 drums (200L/drum) of solidified wastes in 2000 constituting the major portion of the LLWs generation. It is known that cement solidification of the wastes results in a significant volume increase of the wastes. Therefore, a new process for the co-solidification of the wastes with high loading was developed. In the new process, the liquid sodium sulfate waste and the spent powdery resin are solidified together; the mobile sodium sulfate is converted into the very stable barium sulfate and sodium hydroxide by reacting barium hydroxide, and the solidification agent is uniquely formulated for immobilizing sodium hydroxide. For implementing the present process, a pilot system for solidifying wastes in 200L drums was established. The pilot study showed that solidified wastes produced by the process have a volume about 1/3 of that produced by cementation. The solidified product was also shown to have good homogeneity and quality. The co-solidification of the wastes not only results in a volume reduction but also a simpler operation.
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