Technetium measurements by accelerator mass spectrometry at LLNL

Technetium-99 is a long-lived, high-abundance fission product which has bee n widely distributed in the environment through atmospheric testing, the nu clear fuel cycle, and nuclear medicine. It has a high potential for migrati on in the environment as the pertechnetate anion. At the Center for Acceler ator Mass Spectrometry, methods are being developed for the detection of th is radionuclide by accelerator mass spectrometry (AMS), including extractio n from environmental samples, concentration and purification of the Tc-99, conversion to a form appropriate for AMS analysis, and quantification by AM S. Besides interference from the stable (though relatively rare) atomic iso bar Ru-99, the detection of Tc-99 by AMS presents some technical challenges which are not present for the other radionuclides typically measured by AM S. These challenges are related to the lack of a stable Tc isotope. Here we present the status of our Tc-99 methods including discussion of interferen ces and sensitivity, and recent results for environmental samples and the I AEA reference material IAEA-381, Irish Sea Water. Sensitivity is presently similar to 10 mu Bq (similar to 1 x 10(8) atoms) per sample, limited primar ily by 99Ru introduced from process chemicals, and precision/reproducibilit y is similar to 15-25%. (C) 2000 Elsevier Science B.V. All rights reserved.