New Combination Washing Approach of Chemical Interface Controlled Dispersion and High-Speed Shearing Washing Techniques for Radioactive Contaminated Soil (First Report of Field Test in Fukushima)

Abstract

Contaminated soil washing test was implemented in Fukushima for the purpose of performance verification and set-up of engineering database for construction of contaminated soil washing plant. Chemical interface controlled dispersion approach and high-speed shearing washing techniques were applied to wash the contaminated soil over 10,000 Bq/kg and the following results were obtained in this first field test. (1) Dispersion of the radioactive contaminated soil over 10,000 Bq/kg was enhanced in alkalized washing solution at base equilibrium point of pH=10.1～10.5. (2) Remarkable washing performance was achieved under the combination of dispersion and high-speed shearing washing conditions with bead cracking technique in the particle grain size over 0.5 mm and enhanced by ceramic bead addition. (3) Rapid and slow clearing process for surface locking over the coarse grain soil caused by clean-up of very fine contaminated soil particle and strong affinity particles were observed in the relationship between washing rate and operation time. (4) Remarkable well-ordered structural refinement and cumulation of the contaminated soil particle groups with strong FP confinement were observed at the particle size of 0.5～10 μm after washing the contaminated soil particle grain size under 0.5 mm, and sieve classification technique can be applied for elective elimination of this soil particle groups. (5) Filter pressing technique is effective for solidification of the eliminated high ordered contamination soil groups. (6) No contamination in washing solution and machines applied in present field test was observed after these operation.