When uranium deposits are located near the surface, open pit (or open cast) mining is one of the safest, cheapest, and most reliable methods. The process involves:
- Delineation drilling to accurately characterise the ore body.
- Removal of topsoil (kept for later rehabilitation).
- Progressive blasting to form levels or “benches” with side slopes of approximately 0.75:1 gradient. Ammonium nitrate explosives are used — 1 kg of explosive breaks approximately 3 tonnes of rock.
- Continuous surveys during excavation to identify the highest uranium concentrations. Lower-grade “overburden” rock is stockpiled for potential later leaching.
- Ore extraction using front-loader trucks and large excavators (weighing up to 250 tonnes, with 25-tonne scoops) loading into hauling trucks carrying up to 135 tonnes per load.
- Site rehabilitation after mining is complete: the pit is backfilled with leached overburden, topsoil is replaced, and in many cases the pit is filled with water to create an artificial lake.
Radiation safety: Open pit mining has the lowest radiological hazard of the conventional mining methods. Workers receive external gamma exposure and may inhale radon gas and uranium-bearing dust. Doses are controlled through personal dosimetry and dust suppression measures.