Accelerator mass spectrometry measurements of U in groundwater, soil and vegetation at a legacy radioactive waste site.

Low-level radioactive wastes were disposed at the Little Forest Legacy Site (LFLS) near Sydney, Australia between 1960 and 1968. According to the disposal records, U contributes a significant portion of the inventory of actinide activity buried in the LFLS trenches. Although the presence of U in environmental samples from LFLS has been previously inferred from alpha-spectrometry measurements, it has been difficult to quantify because the U and U α-peaks are superimposed. Therefore, the amounts of U in groundwaters, soils and vegetation from the vicinity of the LFLS were measured using accelerator mass spectrometry (AMS). The AMS results show the presence of U in numerous environmental samples, particularly those obtained within, and in the immediate vicinity of, the trenched area. There is evidence for dispersion of U in groundwater (possibly mobilised by co-disposed organic liquids), and the data also suggest other sources of U contamination in addition to the trench wastes. These may include leakages and spills from waste drums as well as waste burnings, which also occurred at the site. The AMS results confirm the historic information regarding disposal of U in the LFLS trenches. The AMS technique has been valuable to ascertain the distribution and environmental behaviour of U at the LFLS and the results demonstrate the applicability of AMS for evaluating contamination of U at other radioactive waste sites.