Use of IsoProbe for Uranium and Plutonium Analysis in Environmental Samples

Abstract

The ability to detect and isotopically characterize uranium and plutonium in environmental samples is of primary importance in the search for nuclear proliferation. The utility of isotope ratio measurements for environmental monitoring is limited by sample preparation costs, measurement precision, and sensitivity. This is particularly true for wide-area monitoring where the number of samples required varies inversely with obtainable precision and sensitivity. This report summarizes an initial evaluation of the applicability of a new technique, magnetic-sector, multicollector, inductively-coupled-plasma mass spectrometry, to environmental sample analysis. This technique is embodied at Lawrence Livermore National Laboratory in the form of a commercially available instrument, the IsoProbe, manufactured by micromass, LTD. (United Kingdom). This is the second of the current generation of such instruments installed in the United States and the first within the Department of Energy complex. Inductively-coupled plasma mass spectrometry (ICPMS) using quadrupole mass filters has existed for roughly 15 years. Magnet sector instruments have also existed for about half that time and multicollector instruments have existed for nearly as long. Among the things that make the new generation of instruments, and the IsoProbe in particular, unique are (1) the use of a gas-collision cell to reduce the energy spread of themore » ions and to remove ions associated with the plasma gas and (2) the introduction of multiple electron-multiplier detection systems. The net effect of these features is to increase sensitivity and precision. Historically uranium and plutonium isotopic compositions have been determined by thermal ionization mass spectrometry (TIMS). While requiring extensive sample preparation, no other technique matched its precision and sensitivity for such measurements. The purposes of this project are to evaluate whether the IsoProbe can replace TIMS for environmental monitoring analyses, whether it can extend the state-of-the-art to higher precision, and whether costs savings can be achieved at the same time.« less