DETERMINATION OF TC-99 IN NUCLEAR SAMPLES BY INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY

Different approaches for the determination of Tc-99 in various nuclear samples are described. Technetium has been determined in leachates of spent fuel and vitrified highly active waste using the elemental response curve of the instrument. It has been observed that Tc is preferentially leached-from spent fuel under oxidizing conditions (30% H2O2) indicating that the pertecnectate ion should be the leached species. It has also been determined in spent fuel dissolver solutions by the method of standard additions using other elements present in the sample as internal standards. Zirconium, Mo and Ru showed to be adequate internal standards for the determination of Tc in those samples. The formation of several polyatomic ions containing Tc was observed at high Tc concentrations. Peaks at m/z 115, 131 and 147 were assigned to TcO+, TcO2+ and TcO3+, the TcO2+ being the predominant polyatomic ion. The ratios of the polyatomic ion to the main Tc-99 peak were estimated with the help of Ph as internal standard. The influence of plasma operating conditions on the relative abundance of those polyatomic ions has been studied. It was also observed that Tc suffers from a long and persistent memory effect.