Use of Airborne γ-Ray Spectrometry for Environmental Assessment of the Rehabilitated Nabarlek Uranium Mine, Australia

Abstract

This article describes an airborne gamma survey of a 7 x 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 gamma radiation over large areas of the site to be derived. For the fenced minesite area this estimate was 0.31 micro Gy 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.

Geographic Variability in Radon Exhalation at a Rehabilitated Uranium Mine in the Northern Territory, Australia

“…Hence, the above estimate for the post-mining flux can be reasonably compared with the upper and lower limits for the pre-mining case, and clearly indicate that the post-mining radon flux from the Nabarlek site is unlikely to be higher than the pre-mining flux. Total areas of the different locations on the mine from Martin et al (2005) and Hancock et al (2005). Unmeasured areas (77 ha) are assumed to exhibit background radon flux densities of 31 mBq·m −2 ·s −1 .…”

Airborne gamma survey of the historic Sleisbeck mine area in the Northern Territory, Australia, and its use for site rehabilitation planning

“…To estimate the terrestrial background gamma dose rate, a histogram of the AGS data was plotted. Assuming that the maximum of the distribution reflects the airborne counts detected over natural background areas (as most of the area surveyed is undisturbed) the resulting background amounts to 0.10-0.14 mGy h À1 , similar to terrestrial background gamma dose rates measured elsewhere in the region, such as Nabarlek (w0.10 mGy h À1 , Martin et al, 2006) or the South Alligator River Valley (0.06-0.15 mGy h À1 , Tims et al, 2000;Waggit, 2004).…”

“…Whereas previous AGS studies used a flight line spacing of 50-100 m (Pfitzner et al, 2001a, b;Martin et al, 2006), a flight line spacing of 25 m at a flying height of 40 m was chosen for this study, due to the small size of the study area. Such flying specifications are close to the technological limit of airborne survey work and result in an unusually high spatial resolution, or sharpness, of the airborne gamma image.…”

“…However, several recent studies have shown their usefulness for abandoned mine site characterization (e.g. Winkelmann et al, 2001;Pfitzner et al, 2001a,b;Martin et al, 2006). In particular, for sites in remote areas, AGS data can provide a radiation perspective at the landscape scale and enable anomalously high radiation areas to be identified for subsequent detailed field-based studies.…”

Comparison of airborne and terrestrial gamma spectrometry measurements - evaluation of three areas in southern Sweden

“…Cresswell and Sanderson Airborne gamma spectrometry (AGS) is a swift and effective technique when broad geographic regions must be surveyed. Its applications include mineral exploration (Smith, 1985), geological mapping (Zhang et al, 1998), environmental assessment and assessment of uranium mine site rehabilitation (Bollhöfer et al, 2008;Martin et al, 2006), fallout mapping (Mellander, 1998) and radioactive source search (Cresswell and Sanderson, 2009;Ulvsand et al 2003). If the survey area is small, ground based mobile gamma spectrometry can be a good alternative or complement to AGS.…”