An Assessment of the ENMOS Airborne Gamma-Ray Spectrometer and Technology

Abstract

WGC carried out the survey of Rum Jungle in July 1996 following discussion with ANSTO staff. The images produced by WGC clearly show elevated count-rates around the Rum Jungle mine site, Rum Jungle South Mine and the East Branch of the Finniss River downstream from the confluence with Old Tailings Creek. Elevated uranium daughter concentrations in the East Branch of the Finniss river is probably due to accumulation of weathering products from before mining, or tailings washed into the river during operation of the mine. WGC used the count rates from the various radionuclides to derive the dose rates in nGy/h at ground level. The map (figure 1 in the hard copy report) shows that the dose rates at the site are comparable to the natural activity at many locations in the region. Evidence of the effectiveness of the image reconstruction algorithms is seen in the Rum Jungle maps. Figure 3 superimposes the dose rate contours onto an aerial photograph of the Rum Jungle site taken in April 1988 after the completion of the rehabilitation project. There is no significant 'shadowing' away from known features, and the shape of the features on the survey shows a good match to features on the aerial photograph. In particular the two water filled open cuts (appear dark grey to black on the aerial photo) are well delineated as having very low dose rates on the derived dose rate contours. Figure 3 also shows that the areas subject to remediation, the Old Tailings Dam, Intermediate Overburden Heap, Whites Overburden Heap, Dysons Opencut (now filled with tailings and covered) and Dysons Overburden Heap all show relatively low dose rates. (Figure 4 is a plan of the Rum Jungle site after rehabilitation showing the locations of the various features). Higher dose rates occur over the Acid Dam, and unrehabilitated areas such as that between White?s and Dysons opencuts. Some of these areas are covered with vegetation. The higher dose rates in these area is either due to the original geological anomaly or to dispersion of material during the mining and processing operations. The dose rates in these areas are comparable with the natural background radiation over a large area east of the Rum Jungle mine site.