Extraction of technetium-99 by complexation with ammonium tetramethylenedithiocarbamate into chloroform and its application to the determination of technetium-99 in low-level radioactive wastes

A feasibility study concerning the extraction of carrier-free 99mTcO4- from HCl solution by chelating with ammonium tetramethy-lenedithiocarbamate (ammonium pyrrolidinedithiocarbamate; APDC) into chloroform was carried out. Extraction parameters such as the effect of acidity in the aqueous phase on extraction efficiency, concentration of APDC, shaking time, volume ratio of the aqueous to organic solutions, back-extraction, electrical charge study of 99mTc ion in dilute HCl, lipophilicity and the stability complex and the extraction of numerous interfering radionuclides were studied. The optimum conditions found were applied in the development of a procedure for the determination of 99Tc in low-level radioactive wastes. Using 99mTc as an internal tracer for the evaluation, the recoveries of 99Tc in various types of low-level radioactive waste samples were higher than 90%. The extraction factors for most of the accompanying radionuclides were higher than 105. The detection limit for 99Tc in a sample of 0.005 kg is 4.2 Bq kg-1 (0.11 pCi g-1) for a 100-min counting interval. (author). 27 refs.; 8 figs