The chemical spill at Ranger Uranium Mine last weekend was the second such incident in a week for the mine's parent company, Rio Tinto, placing further scrutiny on the company's uranium mining operations.

Processing at the Ranger site, in Kakadu National Park, was suspended by the federal government on Tuesday. Environment Minister Greg Hunt ordered ''an immediate investigation'' into the incident in which a leach tank burst, spilling about 1 million litres of highly acidic uranium slurry.

Rio Tinto's Ranger uranium mine in the Northern Territory. Credit:Glenn Campbell

It has since emerged that a virtually identical incident occurred just days before, at Rossing, Rio Tinto's other uranium mine, in Namibia. On December 3, one of the 12 leach tanks at Rossing had a ''catastrophic structural failure'', spilling a large quantity of radioactive slurry.

''This is obviously a very serious incident, which is currently under investigation,'' the mine's general manager of operations, Ben De Vries, was quoted as saying.