Plutonium measurements by accelerator mass spectrometry at LLNL

Mass spectrometric methods provide sensitive, routine, and cost-effective a nalyses of long-lived radionuclides. Here we report on the status of work a t Lawrence Livermore National Laboratory (LLNL) to develop a capability for actinide measurements by accelerator mass spectrometry (AMS) to take advan tage of the high potential of AMS for rejection of interferences. This work demonstrates that the LLNL AMS spectrometer is well-suited for providing h igh sensitivity, robust, high throughput measurements of plutonium concentr ations and isotope ratios. Present backgrounds are similar to2 x 10(7) atom s per sample for environmental samples prepared using standard alpha spectr ometry protocols. Recent measurements of Pu239+240 and Pu-241 activities an d Pu-240/Pu-239 isotope ratios in IAEA reference materials agree well with IAEA reference values and with alpha spectrometry and recently published in ductively coupled plasma-mass spectrometry (ICP-MS) results. Ongoing upgrad es of the AMS spectrometer are expected to reduce backgrounds below 1 x 10( 6) atoms per sample while allowing simplifications of the sample preparatio n chemistry. These simplifications will lead to lower per-sample costs, hig her throughput, faster turn around and, ultimately, to larger and more robu st data sets. (C) 2000 Elsevier Science B.V. All rights reserved.