[en] Simultaneous processing of cesium decontamination and volume reduction for radioactive waste has been developed by applying subcritical hydrothermal blasting technology. The plant of a nominal capacity of 5 ton/day was proved to be sufficient for the intermediate treatment of the MOE-specified off-site waste. The plant verification test results shows that both rates of the cesium removal and the waste weight reduction reached more than 80% by a single path treatment using simulated soil containing non-radioactive cesium. The multipath treatment raised the cesium removal rate to over 95 %. The plant processing was demonstrated to provoke neither re-dispersion of radioactive cesium to the surrounding environment nor radioactive contamination of the plant itself. Based on the trial operations of the plant, Japan Atomic Energy Agency entrusted with the technical estimation of radioactive decontamination methods by Japanese government officially announced that the subcritical hydrothermal blasting technology was expected to be effective for decontamination of cesium adsorbed on soil. (author)