THE SEPARATION OF ~(99)Tc FROM LOW AND MEDIUM-LEVEL RADIOACTIVE WASTES AND ITS DETERMINATION BY INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY

摘要

A chemical separation method has been developed for the determination of Tc in various types of radioactive wastes. Such a method includes (i) fusion with NaOH, (ii) extraction in a column containing methyltrioctylammonium chloride, (iii) extraction by solvent with N-benzoyl-N-phenymydrox-ylamine and, (iv) measurement by inductively-coupled plasma mass spectrometry (ICP-MS). From the performance standpoint, the recovery of TC, using Tc as a yield tracer, is higher than 70%. This analytical method, asdeveloped, ensures effective decontamination with respect to the radionuclides, insofar the decontamination factors are greater than 10~(+5), whenever the residual activity may be measured. Taking into account a 3σ counting error, the detection limit obtained with the ICP-MS technique is 1.9 mBq/ml; the method enabling hence to detect activities as low as 0.3 Bq/g, with analysed samples of 0.2 g and a radiochemical yield of 70%. Studies have been dedicated to the ~(99)Tc measurement, using the electrothermal vaporization ICP-MS technique, which lowers the detection limit by a factor 10, with the standard solution (0.3 pg/ml), compared with the previous ICP-MS technique.