Vol.9 No.3 2017

Research paper : Radioactive cesium decontamination technology for ash (T. Kawamoto et al.)−141−Synthesiology - English edition Vol.9 No.3 (2017) outline of the technology is depicted in Fig. 3. The vegetal materials contaminated by radioactive cesium would be produced in large amounts because of forest contamination. If such combustible contaminants are not treated appropriately, then they might be heated by fermentation or other processes and then ignite. Therefore, appropriate incineration is necessary. However, because radioactive cesium elutes from the incinerated ash through contact with water,[39][40] such ash cannot be processed as regular industrial waste. Our approach is washing after incineration of the contaminants, followed by radioactive uptake by the adsorbent, resulting in volume reduction to 1/500–1/3,000 of the ash, or 1/25,000–1/300,000 of the material before incineration.Although similar decontamination technology has been investigated by many organizations,[41]–[44] the advantage of our technology is the high radioactive cesium adsorption capacity of the PB nanoparticles. Nevertheless, it is unrealistic to apply powder or dispersion liquid of the nanoparticles to the decontamination site. R&D is required for various stages of fabrication of the adsorbent and design of the plant facility. The technology flow is portrayed in Fig. 4 for materials, development of the adsorbent, plant design, and demonstration. By developing the whole process from materials to the plant facility based on the PB nanoparticles, we aimed at making the most of the nanomaterial function for contribution to cesium decontamination. During progress from this material to the plant facility, our development involves different scales from atomic size, nanometer, micrometer to meter scales. For example, control of the chemical composition is necessary in materials development, whereas plant design is development of a metric scale. Such integrated development from materials to plant facilities necessitates the development of technologies on various scales.Fig. 3 Outline of volume reduction of vegetal contaminants and incinerated ash using PB nanoparticles[6]DisporsalAsh-washingIncinerationCs-uptakeCs-extractionashDecontaminated ashExtractionManagementIncinerationCesium (Cs)AdsorbentCs-contaminated materialsAsh decontamination/monitoringAdsorbent with PB-NPMass productionDevice/plantAdsorbentMaterialNon-wovenPond decontaminationColumnsMonitoringcmµmnmÅCompositionoptimizationPlant for ashGranulesNanoparticles/dispersibility controlmFig. 4 Technology development for each scale of the decontamination technology development using PB nanoparticles at AIST

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