Development of a Washing System for Soil Contaminated with Radionuclides Around TRIGA Reactors

Abstract

The purpose of this study was to develop a soil washing system, and to define the most suitable ex- perimental conditions for operation of its individual components, for decontaminating the radioactive soil around a TRIGA (Training, Research, Isotope, General Atomic) reactor in Korea. Analysis results indicated that the main radionuclides were Cs 137 and Co 60 , the soil particle size ranged from 0.063 to 1.0 mm, and the ra- dioactive concentration was the strongest in soil particles smaller than 0.063 mm, as predicted. Meanwhile, ox- alic acid was found to be the most efficient chemical agent for washing, especially for the removal of cobalt. A scrubbing time of 4 h was optimal for obtaining a removal efficiency of more than 75 % for 137 Cs and 60 Co. A mixing ratio of the soil weight to the volume of the oxalic acid solution of 1:10 was observed to be best for washing, and it was estimated to be reasonable for two scrubbing cycles with 1.0 M oxalic acid to avoid the generation of excessive amounts of waste solution. The removal efficiency with hydro-cyclone was 30 % high- er than that without hydro-cyclone. Vertical plates and alum acted as important factors to reduce the sed- imentation time. The waste-solution could be reused after passing it through a column of strong acid resin up to five times.