Migration of radionuclides Sr-85, Cs-137 and Co-60 in unsaturated Chinese loess - A laboratory simulation experiment

As part of a co-operative research project on safety assessment method for shallow land disposal of low level radioactive wastes between the China Ins titute for Radiation Protection (CIRP) and the Japan Atomic Energy Research Institute (JAERI), a laboratory simulation experiment was performed with a n undisturbed soil column 1,340 mm long and 280 mm in diameter under artifi cial sprinkling condition with a rainfall density of 2,907 mm/a to investig ate the migration behaviour of radionuclides Sr-85, Cs-137 and Co-60 in uns aturated Chinese loess. During the simulation experiment, the vertical conc entration distributions of radionuclides Sr-85, Cs-137 and Co-60 were detec ted with a gamma detector by rotating the column slowly. When the experimen t was completed, the vertical concentration distributions of these radionuc lides were determined with a destructive determination method. Comparison of the concentration distribution figures obtained with non-dest ructive detection method and destructive measurement indicates that the non -destructive detection result can only be used as a guidance to the destruc tive measurement. The result of the 1 year laboratory simulation experiment indicates that under the simulation experimental condition, most of 85Sr i ntroduced moved down to a depth of 6.0 to 12.0 cm, while both Cs-137 and Co -60 remained within 1 cm from their origins.