Abstract
This article discusses an ion-chromatographic process that reduces the final amount of radioactive materials being disposed of by one-thousandth of the initial 137Cs-contaminated waste that had been stored in interim storage facilities since the Fukushima Daiichi Nuclear Power Plant accident. The process is composed of four successive processes: 1) transferring Cs from the original waste to fly ash by pyroprocessing decontamination; 2) transferring Cs from the fly ash to water by washing; 3) transferring Cs from the water to a Cs adsorbent by ion-chromatography; and 4) converting the spent adsorbent to its final radioactive disposal state by solidification/stabilization of the adsorbent. Since the ion-chromatographic process plays a major role in the volume-reduction process, based on the physicochemical analysis of the ion exchange process between Cs＋ ions and Cs adsorbents, the mechanism of the selective Cs adsorption of transition metal ferrocyanide is chosen as a Cs adsorbent. The method for calculating the maximum amount of Cs adsorption from the ionic composition of the water used for washing the ash, and the method for designing the ion chromatography are presented as well. Other methods for converting spent Cs adsorbent to its final radioactive disposal state through cement solidification, geopolymer solidification, and phosphate glass are also given.
