RADIOCHEMICAL DETERMINATION OF TC-99 IN LLW BY CHELATION WITH SODIUM DIETHYL DITHIOCARBAMATE (NADDC) AND EXTRACTION WITH CHLOROFORM

A radiochemical method has been developed for the determination of Tc-99 in low-level radioactive waste from nuclear facilities, using Tc-99m as an internal tracer. Radioactive contaminants were removed by carrier hydroxide precipitation and chelating extraction with NaDDC/CHCl3 system at pH 4. The final technetium was chelated with NaDDC in 3N HCl solution and extracted selectively into chloroform. The average of radiochemical recovery for various types of LLW sample is about 90%. The decontamination factors for most radioactive nuclides are higher than 10(5). The detection limit for Tc-99 in a sample of about 10 g is 0.17 pCi/g (6.5 Bq . kg-1) for a 100-minute count.