Fairfax: ERA considering options after Ranger toxic mine leak
27th March 2014
By Peter Ker
A change to lower grade ores at the Ranger uranium mine was the catalyst that lead to a spill of radioactive material in December, according to the Rio Tinto subsidiary in charge of the mine.
Energy Resources of Australia confirmed that investigations into the December 7 spill - which have halted processing at the mine ever since - had been completed
The probe showed that two protective layers inside a leach tank failed before the steel tank itself was eaten through by the toxic mix of acids and uranium particles.
ERA has traced the problem back to 2009, when the company switched from high grade uranium ore to lower grade laterite ores, and duly had to make changes to its processing equipment.
A ''high powered agitator" was installed in the tank in a bid to help with leaching the new ores, but the agitator appears to have displaced a piece of protective equipment, which duly damaged the rubber lining designed to protect the tank.
"The damaged rubber lining allowed acidic slurry mixture to come into contact with the tank's steel wall, which subsequently corroded and lead to the failure of the tank," the company said today in a statement.
A search of five other leach tanks on site found that similar, but less extensive stress, was evident in one other tank, and ERA said it would take advantage of the current shutdown and properly refit all six of its leach tanks.
On top of that, ERA said an investigation of its entire operations had found seven "critical" issues that needed to be addressed before restart, with most relating to the state of tanks used in the processing stage
The leak angered environmentalists given the mine's close proximity to Kakadu National Park, and mine will not be able to restart processing until approvals are gained from the federal and Northern Territory governments.
ERA - which is 68 per cent owned by Rio Tinto - has always said it has enough stockpiles to meet its uranium sale contracts for the first half of calendar year 2014.
But the company said for the first time today that it is considering options for how it meets its uranium sales contracts in the second half, indicating that the shutdown could last several more months.
Under that scenario, ERA may be forced to buy uranium from another miner and deliver that to its customers, in a bid to avoid a breach of contract.
The mine's future remains uncertain in the wake of the spill, with local indigenous groups and environmentalists unconvinced about the merits of operating such a mine in such an environmentally sensitive and high rainfall area.
It is also unclear whether Ranger still has enough uranium to warrant continued mining, with ERA conducting an underground exploration campaign.
Any future mining on site will depend on exploration success.
ERA shares were 2¢ lower at $1.325.