Development of a Normal-temperature Dry Magnetic Separation System for Classifying Soil Contaminated with Radioactive Cesium and Reducing its Volume

The tsunami triggered by the Great East Japan Earthquake in March 2011 caused an accident at the Fukushima Daiichi Nuclear Power Station of the Tokyo Electric Power Company. Radioactive species released from the power station caused extensive environmental pollution. After the accident, surface soil removal and other decontamination activities were carried out that generated large amounts of contaminated waste soil. The total amounts of such soil are estimated to be 14 to 20 million cubic meters. This paper reports the results of our development of a normal-temperature dry magnetic separation system intended to reduce the volume of contaminated waste soil. The authors focused on the tendency of soil with smaller particle sizes to be more contaminated with radioactive species. Conventional technologies, such as wet classification, have problems with the treatment and management of wastewater containing radioactive species and other contaminants. To solve these problems, we designed a dry classification system, which has the function of magnetically classifying soil that has been treated with dry treatment and adsorption of functional magnetic iron powder under dry conditions. To evaluate the classification characteristics of the developed magnetic classification system, we studied soil characteristics of contaminated waste soil and conducted a classification test by using samples collected from different sites. The test results indicated that the system successfully classified soil regardless of where it was sampled from, its capability of the system to reduce the volumes of polluted soil under dry conditions.