Accelerator Mass Spectrometry for Safeguards Applications

Shortly after the discovery of the Iraqi clandestine nuclear weapons development activities, the International Atomic Energy Agency (Agency) Board of Governors reaffirmed the Agency’s right to verify both the correctness and completeness of the nuclear material declarations made by member States. In addition, it was recognized that strengthening measures were also needed. The Model Additional Protocol granted the Agency additional legal authority to implement the needed strengthening measures. The Additional Protocol is an integral part of the strengthened safeguards system and provides the Agency broader access rights as well as an opportunity to enhance the effectiveness of safeguards technology through the application of advanced technology such as accelerated mass spectrometry. Accelerator mass spectrometry (AMS) is a recently developed technology that enables the quantitative measurement of radionuclides by counting atoms, rather than counting decays. For many radionuclides this technique represents a quantum improvement in sensitivity.At the LLNL Center for Accelerator Mass Spectrometry (CAMS) many radionuclides are routinely measured: 3H, 7Be, 10Be, 14C, 26Al, 36Cl, 41Ca, 63Ni, 129I, and 239Pu. In addition to these radionuclides, others, i.e. 32Si, 53Mn, 59Ni, and 99Tc, are in principle detectable but need additional development.These all have a common property; the ratio of the radionuclide to a stable isotope of the same element is exceedingly low, in many instances < 10-12.AMS is able to measure these isotopic ratios through the use of stripping, which suppresses otherwise unresolvable molecular interferences, multiple stages of momentum and energy analysis, and dE/dx detectors, which reduces backgrounds from isobaric interferences. By way of an example, LLNL was a key participant in an inter-laboratory comparison exercise for 129I in support of the International Atomic Energy Agency’s implementation of environmental monitoring, sampling and analysis. Since that time, LLNL has continued its work in evaluating the use of AMS for high sensitivity analysis for the detection of undeclared nuclear activities. LLNL has examined the suitability and effectiveness of AMS for measurement of 129I and other radionuclides as part of an environmental sampling program that could provide indicators of nuclear activities. Results and discussion of LLNL’s work with 129I as well as our evaluation of AMS for the measurement and analysis of other indicators such as plutonium and uranium will be presented.