By far the greatest component of nuclear fuel cycle waste is low level waste from the mining and milling of uranium ores. The most significant wastes are tailings (finely crushed, solid residues from ore processing), liquid waste from processing the ore, and radon gas.
After mining ceases, uranium tailings retain about 80% of the radioactivity of the original ore body. Tailings emit radioactivity to the environment for tens of thousands of years. Before mining the radioactive elements are generally locked in an impervious rock cocoon so little radioactivity reaches the wider environment. After mining, radioactive elements can escape into waterways and the atmosphere. Tailings are finely ground and the radon escapes many thousands of times faster than it otherwise would from the ore body. Wind and water provide a variety of pathways for the spread of this waste.
Tailings dams have a poor track record with many recorded examples of leaks, spills and dam collapses (WISE, 2010).
Tailings are stored above ground at the Olympic Dam (Roxby Downs) copper/uranium mine in South Australia. The tailings dump amounts to about 100 million tonnes, growing at 10 million tonnes annually. If the mine expansion proceeds as planned, tailings production will increase to 68 million tonnes annually. BHP Billiton plans a tailings ‘storage’ facility that would cover an area of up to 44 square kms to a height of up to 65 metres.
Serious questions over the long-term management of these tailings remain unanswered. On March 10, 2006, The Australian newspaper reported on documents obtained under Freedom of Information legislation. The documents, written by scientific consultants to BHP, state that the mine needs urgent improvements in radioactive waste management and monitoring. They call on government regulators to “encourage” changes to the tailings management, noting that radioactive slurry was deposited “partially off” a lined area of a storage pond thereby contributing to greater seepage and rising ground water levels.
In 2009, an Olympic Dam mine worker provided the media with photos of multiple leaks in a tailings dam at Olympic Dam. BHP Billiton’s response was to threaten “disciplinary action” against any worker caught taking photos of the mine site. The Olympic Dam mine is not required to fully comply with the SA Freedom of Information Act.
(More information: <www.foe.org.au/anti-nuclear/issues/oz/u/roxby>)
The Ranger uranium mine in the Northern Territory (NT) is operated by Energy Resources of Australia (ERA), majority owned by Rio Tinto. Since it was established in the 1980s, the mine has been plagued with recurring water and tailings management problems. Contaminated water regularly leaks into Kakadu National Park. Hundreds of spills, leaks and license breaches have been recorded. A recent Australian Government report indicated that the Ranger tailings dam is probably seeping at a rate of 150,000 litres daily. In April 2010, contaminated water was detected downstream of the mine in Magela Creek near where 40 people live. ERA acknowledged that mine was the source of the contamination. In December 2008, a dam burst sending six million litres of contaminated water into the National Park.
Ranger is located in an excised area amongst Kakadu’s extensive wetlands − a system of floodplains, swamps, estuaries, mangroves and mudflats. Seasonal flooding underlines concerns about leaks and spills into waterways still used as a traditional food source. In the 1998-99 wet season, high uranium concentrations in water discharged into the Coonjimba and Magela Creeks was discovered. Contaminated water was released into the creeks for three subsequent seasons before the problem was addressed.
ERA is developing plans to expand its Ranger operations by introducing heap leach mining, which involves spraying sulphuric acid onto piles of low grade ore and collecting the slurry for processing to extract the uranium. Mirarr Traditional Owners are fighting to prevent the expansion of the mine (www.mirarr.net).
Beverley − in-situ leach (ISL) mining
ISL uranium mining is used at the Beverley uranium mine in South Australia and it is the mining method proposed for Beverley Four Mile, Oban and Honeymoon.
ISL mining involves pumping an acidic solution into an aquifer, dissolving the uranium and other heavy metals and pumping the solution back to the surface. After the uranium has been separated, liquid radioactive waste is simply dumped in the aquifer. This liquid waste contains radioactive materials, heavy metals and acid.
Isolation and containment of the pollutants would not be difficult or expensive, but mining companies take the cheaper option of polluting groundwater. Proponents of ISL mining claim that “attenuation” will occur over time − that the groundwater will return to its pre-mining state. However, there is considerable scientific uncertainty about the future of ISL-polluted groundwater. A 2003 Senate References and Legislation Committee report recommended banning the discharge of radioactive liquid mine waste to groundwater.
Spills and leaks are common at ISL mines. The SA Department of Primary Industry and Resources lists 59 spills at Beverley from 1998 to 2007, some involving many thousands of litres of liquid radioactive waste.