Determining a pre-mining radiological baseline from historic airborne gamma surveys: a case study

Area of Science:

• Environmental Science
• Radiological Science
• Geoscience

Background:

• Establishing baseline radioactivity is crucial for uranium mine rehabilitation and radiation protection.
• Natural background radiation levels are considered 'controllable' for regulatory purposes.
• Accurate pre-mining radiological data informs environmental impact assessments.

Observation:

• A 1976 airborne gamma survey near the Ranger mine was groundtruthed using 2007-2009 measurements.
• Measurements included radium-226 soil activity and radon-222 exhalation at a uranium-enriched site.
• Geographic Information System (GIS) and linear correlation models were used to upscale and compare data.

Findings:

• The developed method successfully estimated pre-mining gamma dose rates, radium-226 soil activity, and radon-222 exhalation.
• Modelled pre-mining levels aligned with historical measurements at Ranger Orebodies and regional environmental sites.
• Contemporary groundtruthing of historic airborne gamma surveys is a viable method for determining baseline radiation.

Implications:

• This approach provides a benchmark for uranium mine rehabilitation and closure criteria.
• It is applicable to industrial sites with historical airborne gamma data and suitable radiological analogues.
• The method enhances radiation protection strategies by defining controllable versus natural background doses.