Olympic Dam, South Australia
This EOE article is adapted from an information paper published by the World Nuclear Association (WNA). WNA information papers are frequently updated, so for greater detail or more up to date numbers, please see the latest version on WNA website (link at end of article).
Olympic Dam (30°26'44.30" S, 136°52' 06.31"E), a copper-uranium mine located approximately 570 km north of Adelaide, South Australia, contains the world's largest uranium resource, the fourth-largest copper resource, and sizeable quantities of gold and silver. Minerals at the site include medium-grained chalcopyrite, bornite and chalcocite, fine-grained disseminated pitchblende, and other rare earth minerals in a hematite breccia complex.
The deposits were discovered in 1975 by Western Mining Corporation Ltd, but the mine was not opened until 1988; it is now wholly-owned and operated by WMC (Olympic Dam Operations) Pty Ltd., a subsidiary of BHP Billiton Limited. In 1999, the mine underwent a $1.94 billion expansion, increasing the capacity to 200,000 tons/year of copper and 4,600 tons/year of uranium.
Contents
Production, and expansion plans
After fires in the solvent extraction plant, production recovered in 2004 and 2005 (at 4,370 & 4,335 tonnes oxide (U3O8) respectively). 2008 production was 3943 tonnes U3O8 (3978 t UOC, 3344 tU). (The company reports publicly in terms of uranium oxide concentrate – UOC.) Uranium recovery has been about 72%, due to about half of the uranium being in the form of refractory brannerite, and this is a focus for improvement, with 72.8% being achieved in 2008.
Olympic Dam has enormous reserves of ore, with 285,000 tonnes of contained uranium oxide. The overall resource contains some 2.3 million tonnes of uranium oxide in a hematite breccia complex. While the grade of the uranium ore is lower than that from many mines or potential mines which have the benefit of open cut operation, the fact that copper (Cu) is a co-product with uranium from that same ore (at 2.1% Cu in the proved and 1.8% Cu in the probable reserves) means that such grades are viable.
Before the mid-2005 takeover by BHP Billiton, WMC Resources committed 90 million Australian dollars (A$) (approximately 68 million US$) over two years to assess the potential for doubling the size of Olympic Dam, and in particular to take the resource categorization of the southern orebody through to proven reserves and thus demonstrate the viability of a much-expanded operation - up to 15,000 t/yr U3O8 (with 500,000 t/yr copper). The capital cost involved would be A$5 billion. The pre-feasibility study to decide among the development options, with the environmental impact study, will be completed by the end of 2007. A feasibility study to define the options will be complete in early 2009, and construction of the expanded operations is envisaged for 2009-13.
In mid 2007 BHP Billiton proposed an alternative treatment strategy, which is now part of the base case. This involves exporting some product as copper concentrate rather than only refined copper, and hence exporting some uranium still contained in the copper concentrate. Because the Olympic Dam ore contains copper, uranium, silver and gold in close association, the common procedure of simply selling a copper concentrate with precious metals has not been viable, since some uranium would be in it, creating both processing and safeguards complications for the smelter operator. Most of the uranium is removed at the flotation stage when the copper sulfide is separated from the remainder of the ore, which is then tailings, and the main uranium recovery is from acid leaching of these tailings. Secondary uranium recovery is from acid leaching the copper concentrate, which then goes on to be smelted, containing about 45% copper and 0.01 to 0.15% uranium. At present smelting is done at Olympic Dam, followed by electro refining, and the further traces of uranium are recovered at these stages.
The proposal now is to export much of the copper concentrate with enough uranium still present to require the application of safeguards, so that it is all accounted for. Hence smelting can only be undertaken in one of 36 countries with which Australia has a bilateral safeguards agreement, plus the heavy industry infrastructure required. China is the prime destination and could build dedicated facilities.
With eventually two thirds of the copper concentrate from the expanded Olympic Dam operation being exported as concentrate, up to 3000 tonnes of uranium will be involved. The major part of the uranium – about 13,000 tU/yr, would be recovered and processed as at present (see below). This copper concentrate export strategy for the expanded production from Olympic Dam will diminish the investment cost of the expansion, since smelting and refining for most of the copper increment will not be required. The infrastructure needed at Olympic Dam to operate it - notably electricity - will also be less. A new smelter in China will be lower cost.
Plans for expansion of the mine will mean that 800,000 t/yr of copper concentrate is smelted at site to produce just over half of the copper product, and 1.6 million tonnes is exported to be smelted in China. This lower-grade portion (mostly chalcopyrite – CuFeS2) will have about 2000 t of uranium in it (less than 20% of total U) to be recovered there. Total uranium production would then be 16,000 tU (19,000 t U3O8) per year - with 730,000 tonnes of copper and 25 tonnes of gold.
In October 2008, five stages of this expansion were defined, without specific timeline:
1. By 2013 optimise existing operation, taking ore treatment to 12 Mt/yr from underground and uranium production to 4500 t/yr U3O8.
2. Develop 20 Mt/yr open pit ore supply, build new copper concentrator and uranium leach plant, with increment of copper concentrate being sold to China and processed there at a dedicated new smelter. Uranium production to 9000 t/yr U3O8.
3. Expand existing copper smelter on site for high-grade concentrate. Uranium production 9000 t/yr U3O8.
4. (concurrent with 3) Expand open pit ore supply to 40 Mt/yr, and new copper concentrator and uranium leach capacity accordingly. Low-grade copper concentrate sold to China smelter. Uranium production to 14,000 t/yr U3O8.
5. Expand open pit ore supply to 60 Mt/yr, and build new copper concentrator and uranium leach capacity accordingly. Low-grade copper concentrate sold to China smelter. Uranium production to 19,000 t/yr U3O8.
Eventually the pit will swallow up the present treatment complex.
Environmental protection
The mine is designed with many environmental protection systems including storage facilities for waste products and the ability to return any spillage of ore, concentrate, or process slurries to the process circuit. It also includes comprehensive air pollution and radiation control equipment, that monitor air emissions, noise, and personnel and environmental radiation exposure.
In 1994, a leak of contaminated water was detected under the Tailings Retention System (TRS). Although there were concerns about the highly acidic liquid seeping into the aquifer, any radioactive pollutants in the seepage were filtered out by clay liner at the base of the TRS and the acidity of the water was removed when it reacted with limestone beneath the TRS. The remaining water was of similar quality to the local groundwater, hence no environmental harm nor health impacts on the population of the adjacent mining town of Roxby Downs resulted.
BHP Billiton Olympic Dam submits an Environmental Management and Monitoring report annually to the Department of Primary Industries and Resources South Australia (PIRSA) and the Environment Protection Authority (EPA). This comprehensive report covers all areas of potential environmental impact, including air emissions, site groundwater management, water supply and management of the Great Artesian Basin, flora and fauna monitoring, and annual radiation dose to members of the public. Reporting on progress with action items identified in the Environmental Management Program is provided, as well as involvement with community activities.
The mine lease and the adjacent 11,000 hectare municipal lease have been destocked (of sheep and cattle) since 1986. Following the release of rabbit haemorrhagic disease (RHD), rabbit numbers in the region dropped significantly, and are currently at approximately 40 per square kilometre, compared with plague numbers of up to 600 /km2 in the late 1980s. Red Kangaroo numbers on the mine lease are about 20 per square kilometre, which is slightly higher than surrounding areas because of the access to water. In order to discourage wildlife from entering the tailings storage facility, alternative waterholes have been provided and deterrents installed on the dams and ponds. The evaporation ponds have been fenced with fine mesh to exclude small mammals and reptiles. Foxes and cats are controlled on the lease by shooting and trapping.
BHP Billiton Olympic Dam manages four pastoral stations in the area surrounding the mine and municipal leases with a total area of 1,136,000 hectares. These properties are conservatively stocked to maximise protection of sites of environmental or cultural significance.
The Arid Recovery project, which covers an area of 8,600 hectares, is situated largely on the mine lease and BHP Billiton-operated pastoral stations, with the remaining area (6 hectares) donated by local pastoralists. Arid Recovery is an ecosystem restoration initiative working to restore Australia's arid lands. The program is a partnership between BHP Billiton, the South Australian Department for Environment and Heritage, the University of Adelaide and the community group Friends of Arid Recovery. The reserve is surrounded by a unique cat, rabbit and fox-proof fence. Five locally extinct species have been reintroduced into the reserve.
Before clearing is undertaken for any development work or exploration on the mine and municipal leases, an Environmental/Indigenous Heritage Clearance Permit is required. During this process, all significant slow-growing trees and shrubs and areas of cultural significance are identified. Efforts are made to minimise disturbance caused by operational activity on the leases, and rehabilitation is undertaken afterwards where practical. Considerable attention has been given to rehabilitation of the hundreds of drill pads, some dating from initial exploration, so that many are now scarcely visible even on aerial photos.
Olympic Dam has a Rehabilitation and Closure Plan covering cost estimate basis, summary of closure requirements (for the metallurgical facilities, pilot plant, mine, tailings dams, wellfields, exploration areas, town facilities, power line corridor and miscellaneous facilities), community consultation requirements, closure strategy (including post operational land use objective and completion criteria) and closure plan review requirements. The plan provides a breakdown for each area to be decommissioned, including engineering works required (i.e., demolition and cleaning), environmental works (removal of contaminated material and rehabilitation), specific closure obligations for each area of plant, final land use objectives, closure assumptions, closure material sources, waste disposal sites, cost saving opportunities and liabilities/risks/hazards.
Demolition costs are budgeted based on quotations from a specialist demolition contractor and rehabilitation costs are estimated based on a quotation from a mining contractor with extensive rehabilitation experience. Progressive closure costs have been estimated for each year until actual closure of the site. The financial provision - A$244 million at mid-2006 - is calculated in line with BHP Billiton Accounting Standards.
Further reading
- WNA paper on Australian Uranium Mines
- BHP Billiton web site
