Accelerator mass spectrometry for the detection of ultra-low levels of plutonium in urine, including that excreted after the ingestion of Irish sea sediments

Currently, most methods for the quantitative assessment of Pu-239 have mini mum detection levels (25 mu Bq for alpha-particle spectrometry) that are mu ch higher than the levels of this isotope in many human bioassay and enviro nmental samples. Accordingly, a priority has existed to develop methods tha t are more sensitive. Fission-track and ICP-MS methods have been used, but these can suffer either from an uncertain level of removal and/or recovery of uranium or from isobaric mass interferences. Accelerator mass spectromet ry (AMS) has no such disadvantages, and its demonstrated detection limits f or plutonium isotopes approach levels of attograms, equivalent to about 500 nBq for Pu-239. This paper describes the application of AMS to the measure ment of Pu-239 in urine produced by youths living in London (3.5 mu Bq day( -1)) and by adults (similar to 2-260 mu Bq day(-1)), some of whom were expo sed occupationally. In addition, an experiment was undertaken to measure th e fasted absorbed fraction of ingested plutonium after the ingestion of 15 g of Irish Sea sediment by a volunteer. The measured absorbed fraction was 4.5 x 10(-5). It is concluded that accelerator mass spectrometry is a suita ble method for the ultra-trace detection of plutonium. (C) 1999 by Radiatio n Research Society.