• Progress in Superconductivity and Cryogenics
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• v.26 no.3
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• pp.9-16
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• 2024

A large amount of cesium-contaminated soil was generated as a result of the decontamination work following the accident at the Fukushima Daiichi Nuclear Power Plant. To reduce the final disposal volume of contaminated soil, it is necessary to separate the contaminated soil into low- and high-dose soil components and reuse the low-dose soil under 8000 Bq/kg. We have investigated a magnetic separation technique to reduce the volume of the contaminated soil. Magnetic separation is a volume reduction technology that utilizes these differences in magnetic properties. However, the high-gradient magnetic separation technique (HGMS) we have been studied has problems such as clogging of filters and low separation accuracy due to the passage of 2:1 type clay minerals with small particle diameters. In this study, we propose a new separation method using a cyclone-type magnetic separator that focuses not only on magnetic susceptibility but also on differences in particle size. The cyclone-type magnetic separator can separate 2:1 type clay minerals from 1:1 type clay minerals by inducing 1:1 type clay minerals with large particle diameters to the outside of the cylinder and 2:1 type clay minerals with small and large particle diameters to the inside of the cylinder through the difference in the combined magnetic and centrifugal forces acting on soil particles. Separation accuracy was evaluated using simulated soil consisting of vermiculite and kaolinite. Based on these results, the reduction rate of the radioactivity concentration was estimated, and the design guidelines of the device for practical use were discussed.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.3
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• pp.363-372
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• 2020

Anionic radionuclides pose one of the highest risks to the long-term safety assessments of disposal repositories. Therefore, techniques to immobilize and separate such anionic radionuclides are of crucial importance from the viewpoints of safety and waste volume reduction. The main objective of this study is to design a separator with minimum pressure disturbance, based on the concept of a conventional cyclone separator. We hypothesize that the anionic radionuclides can be immobilized onto a nanomaterial-based substrate and that the particles generated in the process can flow via water. These particles are denser than water; hence, they can be trapped within the cyclone-type separator because of its design. We conducted particle tracking analysis using computational fluid dynamics (CFD) for the conventional cyclone separator and studied the effects due to the morphology of the separator. The proposed sandglass-like design of the separator shows promising results (i.e., only one out of 10,000 particles escaped to the outlet from the separation zone). To validate the design, we manufactured a laboratory-scale prototype separator and tested it for iron particles; the efficiency was ca. 99%. Furthermore, using an additional magnetic effect with the separator, we could effectively separate particles with ~100% efficiency. The proposed sandglass-like separator can thus be used for effective separation and recovery of immobilized anionic radionuclides.