Airborne gamma survey of the upper South Alligator River valley: Second Report

Environment Australia, 2001

Internal Report 377
Pfitzner K, Martin P & Ryan B
Supervising Scientist Division

About the report

During a routine inspection of the Gunlom area in 1999, a staff member of OSS discovered evidence of tailings that had become partially exposed as a result of wet season rains. The tailings are from uranium mining and milling operations that took place in the 1950s and 1960s. To help identify where the tailings were located, an airborne gamma survey was flown over the upper South Alligator River area in October 2000. This type of survey is done from an aeroplane with an instrument onboard called a "gamma ray spectrometer". The gamma ray spectrometer measures the emissions from the decay of three radioactive signals in surface material. The signals are called the "potassium signal" (K), the "thorium signal" (Th), and the "uranium signal" (U). These signals give measures of the abundance of the elements in the ground over which the aeroplane flies. From this survey, eriss is preparing images of the radioactivity levels around the valley area. eriss have also carried out other measurements in the area, and will continue this work throughout 2001. This is being done to help Parks Australia North (PAN) prepare a management plan for old uranium mine and mill sites in the area.