Preparation of zeolite geopolymer monolith and their application to the fixation of nuclear power plant decommissioning waste

This paper reported zeolite formation using sodium aluminate and silica fume. As the application of the solidified body of zeolite polymer, it also reported the results of studies on the solidification of zeolite geopolymers as the secondary radioactive waste composed of zeolite, which has been produced in large quantity in the nuclear power plant decommissioning operation, and carbonate slurry. The authors examined the preparation conditions of the solidified zeolite using the geopolymer method, and found the conditions to be able to prepare it in a short time at a low temperature. The cause of zeolite formation in such a short time is the formation of the aluminosilicate amorphous phase as a precursor. It is considered that this phase reduced the nucleation activation energy of zeolite crystal growth, and zeolite crystals were formed in a short time at a low temperature. As the application of the solidified zeolite geopolymer, the authors examined fixation of the radioactive secondary waste associated with the decommissioning of nuclear power plant using simulated waste. As a result, it was clarified that the zeolite geopolymer produced in the two steps composed of the heating step of about 60 deg C and the curing step of 60 deg C or higher did not deteriorate in strength even in a long-term exposure test and did not deteriorate in strength even after immersion in water. (A.O.)