Investigation as radioactive leak leaves Ranger uranium mine under a cloud The Ranger uranium mine in Kakadu. The future of Australia's oldest uranium mine is under renewed scrutiny, after a tank holding more than a million litres of radioactive slurry burst at the weekend, sparking a federal investigation. The accident prompted traditional land owners to describe the Ranger uranium mine as a "hillbilly operation" with too little regulation. The mine has a history of safety breaches and unions have raised concerns about maintenance standards at the 33-year-old operation. Energy Resources of Australia will launch its own investigation into the incident. But the Environment Department said the surrounding Kakadu National Park was not damaged by the incident as the spill was contained within the mine site. "The supervising scientist made a thorough inspection of the site today and will be discussing the incident response with the regulator, which is the Northern Territory Government," a departmental spokeswoman said on Sunday. The Supervising Scientist Division is an arm of the federal Environment Department that monitors the impact of mining operations in the Northern Territory. The Rio Tinto subsidiary in charge of the mine - Energy Resources of Australia - insisted the cocktail of radioactive uranium and industrial acids had not leaked into the neighbouring Kakadu park, but Environment Minister Greg Hunt declared the incident "unacceptable" and called for an investigation. "At this stage, all the advice I have is that the spill has been entirely contained within the retaining walls," he said on Sunday. The Australian Conservation Foundation and Environment Centre NT called for an immediate halt and no further expansion at Ranger. A protest at ERA's Darwin offices was planned for Monday morning. Uranium supplies at Ranger mine have nearly been exhausted, and ERA has been counting on a new underground expansion to keep the mine going. But it must get approval from the traditional owners of the area, the Mirarr people, for the expansion. The chief executive of the Gundjeihmi Aboriginal Corporation, which represents the Mirarr, said people no longer felt safe living near Ranger mine. "This is nothing but a hillbilly operation, run by a hillbilly miner with hillbilly regulators," Justin O'Brien said. Based on the woefully inadequate government response to the previous incident, we have no confidence that this will be taken seriously enough. A 20-year-old steel tank burst on Saturday morning, damaging heavy machinery and spilling acid and uranium over containment lines. No injuries were reported at the Ranger mine, where up to 1000 people work, but work stopped while the spill was cleaned up. There were still three other 20-year-old tanks holding acid at the Ranger mine, with unions concerned these too could burst. ERA later confirmed it would launch its own investigation but was "confident that Kakadu National Park will not be impacted as a result of this incident" and all water tests had returned normal readings. The Australian Manufacturing Workers Union's Northern Territory organiser, Bryan Wilkins, called for a full independent inquiry into ERA's maintenance program at the mine site. "Obviously there has been a failure in their maintenance program and that has put the workers at that mine site at risk," Mr Wilkins said. People well acquainted with Ranger said the incident did not reflect well on maintenance standards at the mine, which should have ensured that the acids in the tank were not able to cause such significant amounts of corrosion to cause a leak.