Australia's Uranium Mines
There are three operating uranium mines in Australia, Ranger in NT, Olympic Dam and Beverley in South Australia. A fourth is expected to start operation in 2009: Honeymoon, in South Australia, but a new mine on the Four Mile deposit close to Beverley may be in production before Honeymoon.
See also companion paper on Australia's Uranium Deposits and Prospective Mines .
The Ranger mine and associated town of Jabiru is about 230 kilometres east of Darwin, surrounded by the Kakadu National Park, a major tourist attraction. This is a monsoonal part of Australia, with pronounced wet season from December to April. The first orebody is now mined out and the second one (#3) adjacent is now being mined. In the longer term the Jabiluka orebody, 20km away, may be more significant.
History: In 1969 the Ranger orebody was discovered by a Joint Venture of Peko Wallsend Operations Ltd (Peko) and The Electrolytic Zinc Company of Australia Limited (EZ). In 1974 an agreement set up a joint venture consisting of Peko, EZ and the Australian Atomic Energy Commission (AAEC).
In 1978, following a wide ranging public inquiry (the Ranger Uranium Environmental Inquiry) and publication of its two reports (the Fox reports), agreement to mine was reached between the Commonwealth Government and the Northern Land Council, acting on behalf of the traditional Aboriginal land owners. The terms of the joint venture were then finalised and Ranger Uranium Mines Pty Ltd was appointed as manager of the project.
In August 1979 the Commonwealth Government announced its intention to sell its interest in the Ranger project. As a result of this, Energy Resources of Australia Ltd (ERA) was set up with 25% equity holding by overseas customers. In establishing the company in 1980 the AAEC interest was bought out for $125 million (plus project costs) and Peko and EZ became the major shareholders. Several customers held 25% of the equity in non-tradable shares. Ranger Uranium Mines Pty Ltd became a subsidiary of ERA. During 1987-8 EZ's interest in ERA was taken over by North Broken Hill Holdings Ltd and that company merged with Peko. Consequently ERA became a 68% subsidiary of North Limited, and this holding was taken over by Rio Tinto Ltd in 2000. In 1998 Cameco took over Uranerz, eventually giving it 6.69% of ERA, and Cogema took over other customer shares, giving it 7.76%.
Late in 2005 there was a rearrangement of ERA shares which meant that Cameco, Cogema and a holding company (JAURD) representing Japanese utilities lost their special unlisted status and their shares became tradable. The three companies then sold their shares, raising the level of public shareholding to 31.61%.
Production and Sales: The mine started operating in 1980. Full production was in October 1981 at a rate of about 3300 tonnes per year of uranium oxide concentrate. A $53 million program to increase mill capacity to handle almost 2 million tonnes of ore per year, corresponding to output of 5000 tonnes U3O8 per year from Ranger ore was completed in mid 1997. Since 1996 production has been over 4000 tonnes per year.
Mining at Ranger #1 was by open pit, and from 1992-5 this was on a campaign basis, with mining occurring for six months of the year during the dry season and the treatment plant being run for the other six months. In January 1996 there was a return to year-round milling, using stockpiled ore.
Mining at Ranger #3 commenced in June 1997. This orebody was included in initial environmental approvals for Ranger and an intensive program is under way to define extensions to it. It is on the right of the 1998 photo above. (In the photo the original pit for # 1 orebody is beyond the treatment plant and partly full of water and tailings, the main tailings dam is beyond that.)
Uranium recovery is about 91.5%, and ranges up to 93%.
Until 1990 all ERA sales of uranium concentrate were from Ranger production. Over several years the spot price of uranium concentrates was below the cost of production at Ranger, which made it advantageous over 1990-97 for ERA to purchase supplies from third parties. Consequently the amount of such material in overall sales rose to the 1994 level of 1510 tonnes, just exceeding that year's mine production. Further purchases were made 2001-05. The third party concentrates concerned mostly came from Kazakhstan. ERA sales are mostly under contracts with customers who are prepared to pay a price premium for long-term security of supply.
In 2008 production at Ranger was 5339 tonnes of U3O8 (4527 tU) and sales were 5272 tonnes. (NB ERA reports drummed production, whereas Rio Tinto reports Ranger figures on a slightly different basis.)
All ERA uranium oxide sales are to energy utilities in Japan, South Korea, China, UK, France, Germany, Spain, Sweden and the United States under international and bilateral safeguards regulations. ERA supplies about 12% of the world's uranium production. Asia is a particularly important market, with most of the company's premium priced contracts there supplied from Ranger.
In 2008, sales revenue of A$ 692 million yielded earnings before interest and tax of $318 million. After tax profit was $222 million.
In 2008 total energy consumption was 1457 TJ, for production of uranium 2264 PJ (@ 500 TJ/t used in conventional reactor), ie 0.064% of output. CO2 equivalent greenhouse gas emissions were 155,0000 t.
Ranger treatment plant, with mine pit beyond
Process: Following crushing, the ore is ground and processed through a sulfuric acid leach to recover the uranium. The pregnant liquor is then separated from the barren tailings and in the solvent extraction plant the uranium is removed using kerosene with an amine as a solvent. The solvent is then stripped, using an ammonium sulphate solution and injected gaseous ammonia. Yellow ammonium diuranate is then precipitated from the loaded strip solution by raising the pH (increasing the alkalinity), and removed by centrifuge. In a furnace the diuranate is converted to uranium oxide product (U3O8).
Reserves & Resources:The Ranger 1 orebody, which was mined out in December 1995, started off with 17 million tonnes of ore some of which is still stockpiled. The Ranger 3 nearby is slightly larger, and open pit mining of it commenced in 1997. In 2007 it was decided to extend the pit to access further ore (included in the resource figures below).
In 1991 ERA bought from Pancontinental Mining Ltd the richer Jabiluka orebody (briefly known as North Ranger), 20 km to the north of the processing plant and with a lease adjoining the Ranger lease. ERA was proposing initially to produce 1000 t/yr from Jabiluka concurrently with Ranger 3. The preferred option involved trucking the Jabiluka ore to the existing Ranger mill, rather than setting up a new plant, tailings and waste water system to treat it on site as envisaged in an original EIS approved in 1979. However, all these plans are now superseded.
In the second half of 2008 a $44 million processing plant was commissioned to treat 1.6 million tonnes of stockpiled lateritic ore with too high a clay content to be used without this pre-treatment. Following initial treatment the treated ore is fed into the main plant, contributing 400 t/yr U3O8 production for seven years. A new $19 million radiometric ore sorter was commissioned at the same time, to upgrade low-grade ore and bring it to sufficient head grade to go through the mill. It will add about 1100 tones to production over the life of the mine.
A feasibility study into a major heap leach operation for 10 Mt/yr of low-grade ore is under way, with the prospect of recovering up to 20,000 t U3O8 in total. Column leach trials have been encouraging, yielding extractions of greater than 70% at low rates of acid consumption. The facility will consist of fully lined heaps of material about 5m high and covering about 60-70 ha. These will be built and removed on a regular cycle and the residues stored appropriately after leaching is completed. The acid leach solutions will be treated in a process similar to that used in the existing Ranger plant and recycled after the uranium is removed from the pregnant liquor. ERA has applied for government (including environmental) approval for the project.
In 2006 the projected operating life of the Ranger plant was extended to 2020 due to an improvement in the market price enabling treatment of lower grade ores, and in 2007 a decision to extend the operating pit at a cost of $57 million means that mining would continue to at least 2012. Studies on a further possible mine extension, notably the Ranger 3 Deeps Project, are proceeding into 2009.
By November 2008 ERA had defined the Ranger 3 Deeps exploration mineralisation target in the range of 15 to 20 million tonnes, and this has been confirmed as containing 34,000 tonnes of uranium oxide reported in the December 2008 figures above. The mineralised zone has a strike length so far identified of about 1.2 kilometres between 250 metres and 550 metres from the surface, immediately east of the pit, and remains open to the north.
Occupational Health & Safety: Radiation doses received by employees are all well below recommended limits. The designated employees (most exposed to radiation) received an average dose of 1.3 millisieverts per year above natural background in 2008 compared with the recommended annual limit of 20 mSv averaged over 5 years. In first half of 2007 the maximum dose to any person was 3.9 mSv, hence less than 8 mSv/yr.
ERA’s occupational safety and health management systems are certified to AS4801. In 1994 ERA was the first Australian mine to be awarded a 5-star rating by the National Safety Council, putting it in the top 5% of all industry occupational health and safety performance.
Infrastructure:Along with building other infrastructure used by the public, the Company set up the town of Jabiru nearby. While it was initially envisaged that this would be solely a mining town, it has become an important regional centre for tourism and government services, including management of the National Park. Some 200 000 tourists visit the area each year.
Environmental Management
ERA has been recognised for its world-class environmental management, achieving ISO 14001 certification in 2003.
Until 1996 tailings from the treatment plant were emplaced in an engineered dam on the lease, but they are now being deposited into the worked out #1 pit. No process or other contaminated water is released from the site.
The Ranger mine is on a 7860 hectare lease which is surrounded by the World Heritage listed Kakadu National Park of 1.98 million hectares. About 500 hectares is actually disturbed by the mining and milling activities (0.025% of the total area).
Rainfall is monsoonal, with 700-2200 mm (average 1540 mm) falling in the wet season. The vegetation at Ranger is tropical open eucalypt forest, similar to much of the National Park.
The project area is leased from the Aboriginal traditional owners, title to the land being held by the Kakadu Land Trust. The Company contributes 4.25% of its gross sales revenue (the major part of its royalties of 5.5%) to NT aboriginal groups plus an annual rental of $200 000 for the use of the land. Ranger has paid a total of $226 million in nominal terms in royalties since the project began in 1980. The money is paid to the Commonwealth Government and then distributed to Northern Territory-based Aboriginal groups, including 30% to the Gundjeihmi Aboriginal Corporation (representing Traditional Owners), under the 1979 terms of the Commonwealth's Aboriginal Land Rights (NT) Act of 1976. Additional payments of over $7 million are on account of Jabiluka. The balance of royalty (1.25% of revenue) is paid to the NT government by the Commonwealth Government.
The Company has a substantial environmental division, employing about 30 people and with an annual budget of nearly A $3 million. Part of this environmental effort is directed to land management issues of relevance not simply to Ranger, but to the surrounding National Park and World Heritage area. These include maintenance of biodiversity, fire management including control burning (which is very important and contentious in the region), terrestrial and aquatic weed control, feral animal control, mycorrhizal establishment, and rehabilitation of disturbed areas (including rock waste dumps, etc). Ranger is possibly the first mining operation deliberately to burn its own revegetated areas to assist the development of an appropriate vegetation community (Eucalypts and Grevilleas instead of Acacia dominance). Related issues being studied include artificial wetland filters, soil formation from waste rock, and hydrology.
Among Ranger's long term research priorities are projects which are relevant to eventual use of the land by its aboriginal owners.
ERA's success in environmental management has given rise to a consultancy, Earth Water Life Sciences, which is gaining significant business based on Ranger's environmental reputation.
Notwithstanding any results that may come from the ongoing exploration program, the company has developed its plans for mine closure. A mine closure model has been prepared, and circulated to stakeholders, resulting in an estimate of the technical, environmental, social and other costs, through to final closure on both the Ranger project area and surrounds. This closure model is now the subject of review and refinement internally and with stakeholders.
This model, which will be progressively refined over the coming years, has been used as the basis for calculating the financial provision required for eventual closure at the end of mine life. At the end of 2005 the net present value of the closure model for the Ranger project area and surrounds was estimated at A$186 million, fully provided for in the balance sheet.
ERA, separately, is obliged to secure funds for certain costs of rehabilitation in case of any need for premature closure. An annually amended plan is submitted to government outlining this provision, which is reviewed by an independent auditor. Money for this purpose is partly in a trust fund administered by the Commonwealth government and partly covered by bank guarantee. At the end of 2008, security of $149 million was held by the Commonwealth Government in respect to Ranger, and a further $1 million for Jabiluka.
See also ERA web site.
The Olympic Dam copper and uranium mine, with the town of Roxby Downs, is located 560 km north of Adelaide, near the opal mining centre of Andamooka. This is an arid part of Australia, receiving only an average of only 160 mm of rain per year, and that rather unreliably. The massive deposit is underground, some 350 metres below the surface, and is the largest known uranium orebody in the world.
History: The deposit was discovered in 1975 by Western Mining Corporation Ltd which was looking for copper in buried sedimentary rocks. After considering geophysical data a drill hole was sunk near a small stock water dam known as Olympic Dam. It struck copper, and later drilling confirmed a resource of more than 2000 million tonnes of ore containing both copper and uranium. From 1979 the deposit was developed as a Joint Venture with British Petroleum Ltd. In 1985 it was decided to proceed with the project, and production commenced in 1988.
WMC (Olympic Dam Corporation) Pty Ltd is the management company, a wholly-owned subsidiary of BHP Billiton Limited, which took over WMC Resources in mid 2005. Initially BP Minerals Ltd was a 49% partner in the enterprise, but WMC took over BP Minerals' share in 1993 for $315 million.
In mid 1996 WMC announced a A$ 1250 million program to more than double annual production by 2001, to 200,000 tonnes copper and 3700 tonnes uranium concentrate. This expansion program was then accelerated, bringing the increased capacity on line in 1999, with the cost eventually rising to A$ 1.94 billion and the uranium capacity to 4600 tonnes U3O8 per year (which later declined to 4100 t/yr with decreasing grades).
OD Expansion
Before the mid 2005 takeover by BHP Billiton, WMC Resources committed A$ 50 million over two years to assess the potential for doubling the size of Olympic Dam and in particular to take the resource categorisation 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 was estimated as at least A$5 billion. Some $4 billion had already been invested in the mine by WMC, including $680 million over 2001-04, and in 2004 the mine generated A$ 1100 million in export income. The WMC study included drilling on the southern deposit and assessing mining options including possibly a massive open pit (3 km wide, 1 km deep) to access the orebody. Up to June 2007 over 2000 km of drilling has been involved in defining the orebody. In 2008 a fresh look was taken at the possibilities on the basis that the previous assessment of market potential was too conservative. A BHP Billiton pre-feasibility study to decide among the development options, and a 4600-page draft environmental impact study, were completed in 2009. See also BHP Billiton pre-feasibility study
The EIS (summary p20) states: "Drilling of the ore body undertaken by BHP Billiton since 2005 has more than doubled the resource estimate from 3.98 billion tonnes of total mineral resource to 8.34 billion tonnes. At the same time, the expected demand and prices for the minerals means underground mining is no longer the preferred option for such a large ore body. Consequently, open pit mining has become the most feasible option for mining more of the resource. Underground mining can extract only about 25% of the ore containing recoverable quantities of copper, uranium, gold and silver, while an open pit would extract up to 98% as large zones of lower-grade mineralisation that were uneconomical for underground mining can be profitably bulk mined."
In mid 2007 BHP Billiton proposed an alternative treatment strategy, which became 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 of the 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, as could Japan.
With eventually two thirds of the copper concentrate from the expanded Olympic Dam operation being exported as concentrate, some 1700 tonnes of uranium will be involved. The major part of the uranium - about 14,400 t/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 or Japan 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 or Japan. This lower-grade portion (mostly chalcopyrite – CuFeS2) will have up to 2000 t of uranium in it (less than 15% of total U) to be recovered there. Total uranium production would then be 16,100 tU (19,000 t U3O8) per year - with 750,000 tonnes of copper and 25 tonnes of gold.
In October 2008, five stages of this expansion were defined, without specific timeline, and in May 2009 the time span of progressive development was estimated as about 11 years from 2010. The open pit would be developed over five years, removing overburden to expose the first part of the main orebody, Mining from it would then commence mid 2016, and the pit would continue to be developed.
The main metallurgical plant (concentrator) would be developed in three successive 20 Mt/yr stages from 2012. A new hydrometallurgical plant to treat the tailings from this would be developed in conjunction. The existing electro-refinery and smelter would be upgraded to continue processing ore from either the existing (and continuing) underground operation or the open pit.
Production would be 350,000 t/yr of refined copper at site from 800,000 tonnes of concentrate derived for the higher-grade ore, plus about 1.6 Mt/yr of copper concentrate from lower-grade ore and containing some uranium and precious metals. This would yield about 400,000 tonnes of refined copper at an overseas smelter and refinery. Uranium would be recovered: 14,400 tU from the hydrometallurgical plant on site and 1700 tU from the exported concentrates, total about 16,100 tU/yr.
The pit will eventually be 4.1 x 3.5 km, and 1000 m deep, and the waste rock storage about 67 square km to a height of 150 m. Tailings storage would extend the existing facility to about 40 sq km and 65 m high to take 58 Mt/yr.
Required infrastructure will include a 280 ML/day desalination plant (reverse osmosis) on Spencer Gulf, supplying 200 ML/day to the operation; much increased power provision by 650 MWe; a 105 km rail spur; a new airport; accommodation expansion at and near Roxby Downs. Some of the power increment - about 250 MWe - could eventually be met by a cogeneration plant harnessing waste heat from burning sulfur at the acid plant. Most of it would need to come either from the grid or a 600 MWe combined cycle gas turbine plant at Olympic Dam.
A draft Environmental Impact Study was released on 1 May 2009. Following feedback, a Supplementary EIS will be submitted in February 2010 and a government decision on the proposal is expected in mid 2010.
Production and Sales: Olympic Dam is an underground mine. . Some 10 million tonnes of ore is mined each year by open stoping, and this is set to expand to 12 Mt by 2013. Plans outlined above envisage a very large open pit, eventually almost 7km x 4.5 km and 1.2 km deep.
On 6 October 2009, the haulage system in the mine's Clark Shaft was damaged. While hoisting continues at the secondary Whenan Shaft, capacity is reduced to about 25% until full production resumes, now estimated to be in March 2010.
In 2001 the plant suffered a fire in the solvent extraction plant and production remained low for two years. 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 65-70%, 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.
Sulfur dioxide from the copper minerals is made into acid and used in uranium processing.
Sales of uranium concentrate are made under long-term contracts to electric utilities in Canada, USA, Japan, South Korea, China, Finland, Sweden, Belgium, France and the United Kingdom.
Process: Following primary crushing underground, the ore is ground and treated in a copper sulphide flotation plant. About 80% of the uranium minerals remain in the tailings from the flotation cells, from which they are recovered by acid leaching. The copper concentrate is also processed through an acid leach to recover most of the other 20% of the uranium. The pregnant liquor is then separated from the barren tailings and in the solvent extraction plant the uranium is removed using kerosene with an amine as a solvent. The solvent is then stripped, using an ammonium sulphate solution and injected gaseous ammonia. Yellow ammonium diuranate is then precipitated from the loaded strip solution by raising the pH, and removed by centrifuge. In a furnace the diuranate is converted to uranium oxide product, U3O8.
Ore: The deposit occurs in the basement rocks of the Stuart Shelf geological province in the north of South Australia. Mineralisation consists of medium-grained chalcopyrite (CuFeS2), bornite (Cu5FeS4) and chalcocite (Cu2S), fine-grained disseminated pitchblende and brannerite (U minerals), gold, silver and rare earth minerals that occur in a magnetic hydrothermal breccia complex beneath 350m of overburden. The ore occurs in distinct zones that determine the mine access and layout. (mining-technology.com & infomine)
Reserves & Resources: Olympic Dam has enormous reserves of ore, with 347,000 tonnes of contained uranium oxide. The overall resource contains some 2.45 million tonnes of uranium oxide in a hematite breccia complex. While the grade of the uranium ore is lower than many mines or potential mines which have the benefit of open cut operation, the fact that copper is a co-product with uranium from that same ore (at 1.8% Cu in the reserves) means that such grades are viable.
Occupational Health & Safety:The mine is well ventilated with powerful fans so that radiation exposure from radon daughters is very low. Exposure from gamma radiation is also minimal, due to the low grade of uranium mineralisation. The average annual radiation exposure level (over the 1.5 mSv/yr background) for all designated underground workers in 1999-2000 was 1.7 millisieverts (ranging up to 9.9 mSv). These levels compare very favourably with the annual limit of 20 mSv/yr averaged over five years.
The site has implemented a Safety Management System which is compliant to Level 3 Exempt Status under the state occupational safety organisation, and this has been officially recognised.
Infrastructure:Expansion of the mine will bring major infrastructure challenges. The present 12 GL/yr water consumption (met from the Great Artesian Basin) will grow, possibly to 70 GL/yr, requiring a coastal desalination plant with pipeline to Olympic Dam. The operation now uses 10% of the state's base-load power (870 GWh/yr) and the expansion will add demand for another 650 MWe and 4400 GWh/yr, the source of which remains to be determined. The CO2 output from power generation attributable to the operation is likely to grow from 0.9 to some 4.7 Mt/yr.
The mine lease of 18,000 hectares is managed by BHP Billiton Olympic Dam. The mine, smelter and infrastructure occupy about 7.5% of the lease area. Environmental management activities account for approximately one third of expenditure from the overall environmental budget, which is in excess of A$ 2 million. In February 2005, Olympic Dam was successful in obtaining ISO14001 certification for the site Environmental Management System.
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.
Rock waste and the coarse fraction of tailings are used as mine backfill. Fine tailings material, still containing potentially valuable minerals (rare earths etc.) is emplaced in tailings dams on the lease covering about 400 hectares.
During 1994 seepage of contaminated water from the tailings dams was identified. This was of concern to the company, the regulators and the public because of the perceived threat to the quality of groundwater immediately below the tailings dams. Studies undertaken demonstrated that the pollutants in the seepage were quickly adsorbed on to clays and limestone in the soil and rock under the tailings dams, and, due to the low permeability and transmissivity of the rock, that there was no potential harm to the groundwater resource. The level of the groundwater under the tailings dams is monitored and modelled on a quarterly basis.
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 annual Sustainability Report is on the webhttp://bhpbilliton.com/bb/sustainableDevelopment/reports.jsp
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 (ie 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.
The Beverley uranium deposit is 520 kilometres north of Adelaide, on the plains north-west of Lake Frome and 25 kilometres north east of the Arkaroola Resort in the northern Flinders Ranges. It is a relatively young sandstone deposit with uranium mineralisation leached from the Mount Painter region, and was the basis of Australia's first commercial in situ leach (ISL) operation. In 2008 a major mine lease extension was obtained so that the lease is now contiguous with the Four Mile East lease.
History and Background: Beverley was discovered in 1969 by the OTP Group (Oilmin NL, Transoil NL, & Petromin NL). A draft EIS was produced in 1982 but plans to mine it by in situ leaching (ISL) were abandoned in 1983 when a newly-elected South Australian Government made it clear that mining leases would not be approved. The deposit was sold to Heathgate Resources Pty Ltd, an affiliate of General Atomics of USA, in 1990.
The deposit consists of three mineralised zones (north, central and south) in a buried palaeochannel (the Beverley aquifer) in tertiary sediments of the Frome basin. Groundwater salinity ranges from 3000 mg/L total dissolved solids in the north to 12,000 mg/L TDS in the south. The aquifer is isolated from other groundwater, notably the Great Artesian Basin about 150 metres below it and small aquifers in the Willawortina Formation above, which are used for stock watering.
A field leach trial in 1998 was outstandingly successful, with performance three times better than similar deposits in USA, and it established the commercial viability of the project.
A new draft EIS was released for public comment in July 1998 and the Supplement in October, with environmental approval being given in March 1999. Other approvals were in April 1999. Mine construction started in 1999, including processing plant, camp, airstrip, 4.0 MWe gas-fired power station and two wellfields.
A royalty equivalent to 2% of gross sales was negotiated with four Aboriginal Native Title Claimant groups, and the first payments totalling more than $100,000 were made to trust accounts in mid 2000. The agreements also provide for training, employment, community payments and administration payments.
See also web site.
Production and Sales: Production, licensed to reach 1180 t/yr U3O8 equivalent, commenced from the north mineralised zone in November 2000 though no product was drummed until 2001, when production totalled 546 tonnes U3O8. Exports commenced in 2001. Production for 2004 reached 1084 tonnes U3O8 but has steadily dropped since. In 2008, 659 tonnes was produced. Sales contracts are with power utilities in USA. From 2009 production is projected to increase to 1500 t/yr.
Process: The mine consists of wellfields which are progressively established over the orebody as uranium is depleted from sections of the orebody immediately underneath. Wellfield design is on a grid with alternating extraction and injection wells, each of identical design and typical of normal water bores. The spacing between injection wells is about 30 metres with each pattern of four having a central extraction well. A series of monitor wells are situated around each mineralised zone to detect any movement of mining fluids outside the mining area.
Beverley wellfield
Submersible electric pumps initially extract native groundwater from the host aquifer prior to the addition of uranium complexing reagents (acid) and an oxidant (hydrogen peroxide or oxygen) before injection into the wellfield. The wells are cased to ensure that liquors only flow to and from the ore zone and do not affect any overlying aquifers. They are pressure tested before use. The leach liquors pass through the ore to oxidise and dissolve the uranium minerals in situ. The pregnant solution from the production wells is pumped to the treatment plant where the uranium is recovered in a resin ion exchange (IX) system.
The uranium is then stripped from the ion exchange resin, and precipitated with hydrogen peroxide. The uranium slurry is dewatered and dried to give hydrated uranium peroxide (UO4.2H2O) product. From 2010 it is expected that the plant will also treat loaded resin trucked in from the Four Mile project adjacent.
Before the remaining process solution is reinjected, it is oxygenated and if necessary recharged with sulfuric acid to maintain a pH of about 2.0 to 3.0. Most of the solution is returned to the injection wells, but a very small flow (about 0.5%) is bled off to maintain a pressure gradient in the wellfield and this, with some solutions from surface processing, is treated as waste. It contains various dissolved minerals such as radium, arsenic and iron from the orebody and is reinjected into approved disposal wells in a depleted portion of the orebody. This bleed of process solution ensures that there is a steady flow into the wellfield from the surrounding aquifer, and serves to restrict the flow of mining solutions away from the mining area.
Beverley ISL processing plant
Reserves: Three ore lenses in unconsolidated sands lie at a depth of 100-130 metres, over some 4 km of palaeochannel. They contain at least 21 000 tonnes of uranium oxide at 0.18% grade, much of which is recoverable by in situ leaching, making it the largest Australian ISL deposit. In November 2006 the company applied to extend the mine lease to take in contiguous ground with further ore.
Occupational Health and Safety: The usual radiation protection measures are applied, despite the fact that most of the orebody¹s radioactivity remains well underground and there is hence minimal increase in radon release and no ore dust. Designated employees wear personal dosimeters to measure exposure to gamma radiation and radon daughter concentration is measured regularly in the plant area. Routine monitoring of air, dust and surface contamination is also undertaken.
Environmental Management: An Environmental Management and Monitoring Plan (EMMP) has been developed with the regulating authorities, who determined the requirements of it, including those for radiation protection. The Plan provides for ongoing management of every aspect of the operation. Monitoring to detect possible horizontal excursions from the mining zone or any vertical leakage into other aquifers is a fundamental facet of mine operations.
In contrast to the main ISL operations in USA extracting uranium from aquifers with potable water, the groundwater quality at Beverley is very low, being fairly saline and orders of magnitude too high in radionuclides for any permitted use to start with. Fluids from mined areas are progressively moved to new mining areas, thus reducing the overall effect on the aquifer. After completion of mining, when oxygen input and leaching are discontinued, the groundwater reverts to about pH 4.5, and then over time to its original condition at about pH 7.
Heathgate bought the 2350 sq km Wooltana pastoral lease, from which the 13.5 sq km project area is fenced off and destocked. This area, mainly Mitchell grass plain, will be allowed to rehabilitate naturally to guide later revegetation of mined areas.
Upon decommissioning a wellfield, wells are sealed and capped, pipes are removed and the surface revegetated progressively. At the end of the mine's life, process facilities will be removed and after discussion with the stakeholders the land can revert to its previous uses. Heathgate has provided financial guarantees to the state government in respect to ongoing mine site rehabilitation up to the final completion of mining.