Improvements in actinide and fission product analysis by AMS - Raising the bar and lowering detection limits in heavy element analysis

High sensitivity analyses of fission products and actinides have important applications in monitoring environmental radioactivity and in nuclear safeguards. In particular, the isotopic ratios of actinides are key signatures of nuclear activities and their measurement is a significant part of the environmental sampling program undertaken by the IAEA. Accelerator Mass Spectrometry (AMS) offers unparalleled abundance sensitivity in isotope ratio measurements. For example when used for the detection of the fission product 129I, 129I/127I ratios can be measured down to the 1x10-14 level. A range of other rare long-lived radioisotopes can also be measured despite the presence of high abundance isotopes of similar mass. In addition, AMS can be used for ultra-high sensitivity detection of actinides with several isotopes of interest, such as plutonium. Several plutonium isotopes can be measured in the same sample at the femtogram level (1x10-15 g). The high ‘abundance sensitivity’ of AMS is useful in this case for reducing possible interference from uranium, which may be present in the sample at the nanogram level. In this paper we present a discussion of our most recent achievements in the development of AMS as an ultra-trace analysis instrument for plutonium and other nuclear signatures in environmental materials. We will also highlight current development work aimed at further increasing our instrument's sensitivity.