Chemical interface controlled dispersion and high-speed shearing water washing tests were implemented for the purpose of optimization of processing conditions with highly radioactive contaminated soils of over 570,000 Bq/kg in Fukushima and the following results were obtained. (1) Dispersion and miniaturization of the radioactive contaminated soil over 570,000 Bq/kg was enhanced in alkalized washing solution and optimization of pH control is required according to soil characteristic. From these results, it is recommended that pH 10.5, 10.7 and 11 are optimized pH for soil B, C and A, respectively. (2) Refinement of contaminated soils was also promoted by collision of contaminated soil particles toward washing machine walls and inter-particle collision during soil washing process and remarkable washing performance was achieved under the combination of dispersion and high-speed shearing washing condition with 50% (maximum) solid density in wash solution and for 1 h operation at least. (3) Remarkable well-ordered structural refinement and accumulation of the contaminated soil particle group with strong FP confinement were observed at the particle size under 10 mu m after crack/washing process.