Radiological assessment for bauxite mining and alumina refining

Area of Science:

• Radiological Science
• Environmental Science
• Occupational Health

Background:

• Naturally Occurring Radioactive Material (NORM) management is crucial in mining and processing.
• International benchmarks (1 Bq/g activity, 1 mSv/year exposure) guide regulatory exclusion and exemption.
• Alcoa of Australia Limited (Alcoa) has a history of radiological evaluations for Darling Range bauxite operations.

Purpose of the Study:

• To assess occupational radiological doses from bauxite mining and processing against regulatory benchmarks.
• To evaluate the effectiveness of the Alcoa NORM Quality Assurance System (NQAS) in managing NORM.
• To determine compliance with the 1 mSv/year exemption level for worker exposure.

Main Methods:

• Whole-of-year monitoring of occupational radiological doses (gamma, radon) over 12 months (2008/2009).
• Positional monitoring to establish accurate natural background levels and assess exposure potentials.
• Personal monitoring to characterize exposures within Similar Exposure Groups (SEGs).

Main Results:

• Natural background radiation levels were consistent with literature and global data.
• Above-background dose estimates correlated with local geochemistry, with slight elevations in mining pits.
• Total incremental composite doses for workers were below 1.0 mSv/year, even with activity concentrations above 1 Bq/g.

Conclusions:

• Bauxite mining, refining, and residue operations comply with the 1 mSv/year exemption level.
• Results align with previous monitoring and demonstrate effective NORM management.
• Findings are relevant for global bauxite and alumina industries.