Plutonium measurements by accelerator mass spectrometry at LLNL

Abstract

Mass spectrometric methods provide sensitive, routine, and cost-effective analyses of long-lived radionuclides. Here we report on the status of work at Lawrence Livermore National Laboratory (LLNL) to develop a capability for actinide measurements by accelerator mass spectrometry (AMS) to take advantage of the high potential of AMS for rejection of interferences. This work demonstrates that the LLNL AMS spectrometer is well-suited for providing high sensitivity, robust, high throughput measurements of plutonium concentrations and isotope ratios. Present backgrounds are ∼2 × 10 7 atoms per sample for environmental samples prepared using standard alpha spectrometry protocols. Recent measurements of 239 + 240 Pu and 241Pu activities and 240Pu/ 239Pu isotope ratios in IAEA reference materials agree well with IAEA reference values and with alpha spectrometry and recently published inductively coupled plasma–mass spectrometry (ICP–MS) results. Ongoing upgrades of the AMS spectrometer are expected to reduce backgrounds below 1×10 6 atoms per sample while allowing simplifications of the sample preparation chemistry. These simplifications will lead to lower per-sample costs, higher throughput, faster turn around and, ultimately, to larger and more robust data sets.