Environmental Monitoring and Assessment (2006) 115: 531–553 DOI: 10.1007/s10661-006-7244-y c Springer 2006 USE OF AIRBORNE γ-RAY SPECTROMETRY FOR ENVIRONMENTAL ASSESSMENT OF THE REHABILITATED NABARLEK URANIUM MINE, AUSTRALIA PAUL MARTIN1,2,∗, STEPHEN TIMS1,3, ANTHONY MCGILL4, BRUCE RYAN1 and KIRRILLY PFITZNER1 1Environmental Research Institute of the Supervising Scientist (eriss), Darwin, NT, Australia; 2Agency’s Laboratories Seibersdorf, International Atomic Energy Agency, Vienna, Austria; 3Department of Nuclear Physics, Australian National University, Canberra, ACT, Australia; 4Northern Territory Department of Business, Industry & Resource Development, Darwin, NT, Australia (∗author for correspondence, e-mail:
[email protected]) (Received 16 May 2004; accepted 12 May 2005) Abstract. This article describes an airborne γ survey of a 7 × 5 km region around the rehabilitated Nabarlek uranium mine in northern Australia. An unusually tight line spacing (100 m) and low aircraft height (50 m) were used, enabling the survey to distinguish man-made structures such as ponds and accommodation areas, as well as creek lines. Positive correlations between airborne data and ground- based readings enabled an estimation of the average absorbed dose rate arising from terrestrial γ radiation over large areas of the site to be derived. For the fenced minesite area this estimate was 0.31 μGy hr−1. The airborne survey data were found to be invaluable in helping to plan further ground-level investigations and showed promise as an assessment tool for rehabilitated minesites. Keywords: airborne gamma survey, dose rate estimation, Nabarlek, radiological assessment, reha- bilitation, uranium mining 1. Introduction Airborne γ radiometric surveys have been used extensively over several decades for mineral exploration and geological mapping purposes (Galbraith and Saunders, 1983; Smith, 1985; Zhang et al., 1998).