Technetium Measurements by Accelerator Mass Spectrometry at LLNL

Technetium-99 is a long-lived, high-abundance fission product which has been widely distributed in the environment through atmospheric testing, the nuclear fuel cycle, and nuclear medicine. It has a high potential for migration in the environment as the pertechnetate anion. At the Center for Accelerator Mass Spectrometry, methods are being developed for the detection of this radionuclide by accelerator mass spectrometry (AMS), including extraction from environmental samples, concentration and purification of the Tc, conversion to a form appropriate for AMS analysis, and quantification by AMS. Besides interference from the stable (though relatively rare) atomic isobar Ru, the detection of Tc by AMS presents some technical challenges which are not present for the other radionuclides typically measured by AMS. These challenges are related to the lack of a stable Tc isotope. Here we present the status of our Tc methods including discussion of interferences and sensitivity, and recent results for environmental samples and the IAEA reference material IAEA-381, Irish Sea water. Sensitivity is presently ~10 μBq (~1×10 atoms) per sample, limited primarily by Ru introduced from process chemicals, and precision/reproducibility is ~15-25%. Submitted to Nuclear Instruments and Methods B, as part of the proceedings of the 8th International Conference on Accelerator Mass Spectrometry, Vienna, 1999.