Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

Accelerator Mass Spectrometry (AMS) provides a high-sensitivity method for detection of long-lived radioisotopes. New facilities at ANSTO’s Centre for Accelerator Science are enabling us to detect plutonium by AMS with unprecedented level of sensitivity. We can now detect traces of the isotope 244Pu (half-life 80 million years) which arrive on earth on interstellar dust. However, the predominant source of plutonium on earth’s surface is from human activities, in particular from atmospheric nuclear testing of the 1950-1960’s. In Australia, the radiological residues originating from the British tests at the Montebello Islands, WA, occur in distinct isotopic and morphologic forms. The three tests had slightly different Pu isotopic signatures. Today, aided by the high sensitivity of AMS, their distinct 240/239Pu atom ratios can be differentiated in biological samples, such as failed sea turtles eggs gathered from beaches. Local fish tend to reflect a mixture of all three tests due to the movement of the fish and transport of Pu by water currents. On a larger scale, the 240/239Pu atom ratios in all samples (median ratio 0.04) are distinct from worldwide fallout (0.17-0.18) and can be used as a tracer for migrating species. The Pu exists in the environment in the form of ‘hot’ particles; the mobility of these particles and their availability for uptake into living organisms depends on their physical and chemical characteristics, which we are currently studying using a range of methods including synchrotron-based X-ray fluorescence microscopy (XFM).