Beyond the Three Mines - In Situ Uranium Leaching Proposals in South Australia


Research Paper 12 1997-98

Paul Kay
Science, Technology, Environment and Resources Group
12 May 1998

Contents

Major Issues Summary

Introduction

South Australian Proposals

Geology

Technology of Leaching Systems

Environmental Considerations

In Situ Leaching Impacts upon Aquifers

Marketing of Uranium

Conclusions

Acronyms

Endnotes

List of Figures

Figure 1. Locality map for the Beverley and Honeymoon proposals 4

Figure 2. Cross section of a sandstone hosted roll front type uranium deposit 6

Figure 3. Generalised cross section of the In Situ Leaching Process

Major Issues Summary

  • The change of Commonwealth Government in March 1996 meant that the 'three mine policy' of the Labor Party was no longer in place. The Coalition policy prior to the election was to approve new uranium mines subject to environmental and other obligations. Companies have further considered the opening of additional uranium mines following this change.
  • Where geological and other conditions are suitable, In Situ Leaching (ISL) can be used to mine uranium. Mining by ISL technology is proposed and field-testing has commenced at the Beverley and Honeymoon deposits, both in South Australia.
  • ISL technology is used widely for the mining of uranium and offers some advantages over conventional mining methods depending upon the mineral deposit. Uranium from ISL mining accounted for 13 per cent of global mine production of uranium in 1996, mainly from the USA, Uzbekistan and Kazakhstan.
  • Conventional mining methods have greater infrastructure, ground disturbance and materials handling requirements than ISL mining; thus the impact from ISL is comparatively less for an equivalent amount of production. Similarly, ISL mining reduces the risks to workers from exposure to radiation, particularly when compared to conventional underground mines.
  • Water and aquifer management must be carefully considered in the design of ISL mining operations for economic and environmental reasons. Groundwater in the confined aquifers at both proposed Australian mines is saline, radioactive and not suitable for human consumption or general use.
  • Prior to the commencement of mining in South Australia, approval under the relevant legislation is required. Both Beverley and Honeymoon have received approval from the South Australian Government for the commencement of test leaching, with production approval pending on the test results. Furthermore, the export of uranium requires Commonwealth approval under regulations of the Customs Act 1901 and the Environment Protection (Impact of Proposals) Act 1974.
  • Issues with the ISL mining of Beverley and Honeymoon include potential impact on aquifers such as the Great Artesian Basin, and broader concerns over uranium as a commodity. Australia's involvement in the production and export of uranium is likely to produce the most vocal opposition to ISL mining. Paradoxically, demand for uranium and nuclear power generation may increase in signatory countries to the Kyoto agreement because nuclear energy generates zero greenhouse gas emissions.

Introduction

South Australia has a history of involvement in the uranium mining industry, dating from the Radium Hill underground mine (1954-62) through to the operating Olympic Dam underground mine. The locality of the Olympic Dam mine is shown in Figure 1. Two proposals for the In Situ Leaching (ISL) of uranium are currently being considered in Australia. Both the deposits, Beverley and Honeymoon, are in the east of South Australia, Beverley is 520 kilometres north of Adelaide and Honeymoon is 75 kilometres directly north-west of Broken Hill. Production was about to commence at Honeymoon, but was abandoned in 1983 following the election of the Commonwealth Labor Government. Plans to mine the geologically similar Beverley deposit were rejected by the South Australian Government in 1983 due to the change in Commonwealth Government and the proposal was dropped.

The Coalition Resources and Energy Policy prior to the 1996 election included a commitment to 'approve new uranium mines and uranium exports subject to strict environmental, heritage and nuclear safeguards obligations'.(1) The change of Commonwealth Government in March 1996 meant that the 'three mine policy' of the Labor Party Platform was no longer in place. Following the implementation of Coalition policy, companies moved to open additional uranium mines.

Southern Cross Ltd plans to commence production at Honeymoon pending relevant approvals, building to 500 tonnes of uranium oxide concentrate (U3O8 or yellowcake) per annum by mid 1999. Heathgate Resources is working towards the commencement of production at Beverley in 1999, pending approval of a new Environmental Impact Statement (EIS). These time frames would be optimistic with conventional mining, but the practicalities of ISL make them possible. The use of ISL methods to exploit Beverley and Honeymoon means the mines will be low cost and likely to remain competitive, despite fluctuations in market conditions.

Traditional mining methods rely on the relocation of large volumes of mineralised and waste rock. Thus, underground cavities, open pits and waste rock or tailings repositories are left after mining. Where geological conditions are appropriate, mineral deposits (including uranium and other metals) can be mined by ISL. Known also as solution mining, ISL mining utilises liquids moving through mineralised rock to recover uranium. Chemically treated water is delivered underground where uranium minerals are dissolved or leached into solution, forming pregnant liquor. The pregnant liquids are then pumped back to the surface for extraction of uranium.

ISL technology has been proven at a number of localities around the world, extracting a variety of metals including uranium, gold and copper. Economic advantages with ISL mining are clear, costs being generally much lower than for conventional mining. Low-grade orebodies, which are sub-economic by conventional techniques, may be mineable by ISL methods. About 13 per cent of global mine production of uranium in 1996 was recovered using ISL techniques mainly in the United States, Uzbekistan and Kazakhstan. ISL mining has a number of relative environmental benefits, for example, less ground disturbance and materials handling. A significant risk of groundwater contamination can result with ISL mining if strict benchmark techniques are not followed. Contamination of groundwater and surface water in Bohemia in the Czech Republic has been identified as a result of ISL mining. Similarly, the contamination of aquifers has occurred in Kazakhstan and Uzbekistan.(2)

Provided that appropriate precautions are observed, mining of Beverley and Honeymoon deposits by ISL offers reduced environmental impact relative to conventional methods. Infrastructure requirements for ISL are less than for conventional mining methods. Underground or large scale surface materials handling is not required for ISL, thus employees at ISL operations are exposed to lower dust levels and face lower safety risks generally. The exposure of workers to radon gas or other radionuclides in underground workings is eliminated.

Water management, both on the surface and in production aquifers is inherent in the design of an ISL mine. The risk of contaminating aquifers through ISL mining must be considered, but can be avoided by appropriate design and monitoring. Any loss of treated water from the ISL system represents both an economic cost to the mine (through lost treatment chemicals, uranium or both), in addition to an environmental risk. The groundwater at both the proposed Australian mines is of low quality, both in terms of salinity and radionuclides, and is not suitable for consumption or general use.

The mining of Beverley and Honeymoon will raise issues associated with uranium in general, as well as the relatively new ISL mining method. Concerns are likely to be voiced over the risks associated with nuclear materials and groundwater resources in this arid part of Australia. However, approval to commence mining will be required from the South Australian Government and Commonwealth Legislation requires that approval be granted under the Customs Act 1901 for the export of uranium. Commonwealth approval under the Environment Protection (Impact of Proposals) Act 1974 is also required for the Honeymoon and Beverley proposals.

South Australian Proposals

The two ISL uranium-mining projects currently under consideration in South Australia are Beverley and Honeymoon; both are located in the remote arid east of the state as shown in Figure 1. Broken Hill (population 23 500) in western NSW is the nearest major settlement. One of the two operating uranium mines in Australia, Olympic Dam, is in South Australia. The other is Ranger in the Northern Territory shown in Figure 1. The Jabiluka uranium mine some 20 kilometres north of Ranger has received approval, and construction is planned to commence in May 1998. The Beverley and Honeymoon proposals were moving toward production, when in March 1983 the Federal Labor Government revoked all negotiating licences of uranium companies.(3) Despite the long history of both the Honeymoon and Beverley proposals, these remain the only ISL uranium mining proposals in Australia.

The proximity of Honeymoon to Broken Hill has meant that in the development phase, workers have driven 120 kilometres each way between the town and the deposit.(4) The nearby Kalkaroo deposit at Yarramba was discovered in 1970, then Honeymoon was located in 1971. The Honeymoon deposit is at a depth of 100 to 120 metres below the surface. The MIM Ltd and CSR Ltd proposal in 1983 at Honeymoon was to produce 450 tonnes per annum of U3O8 by ISL mining. This proposal was developed through the 1970s at a cost of about $12 million.(5) Gutteridge, Haskins & Davey produced draft and Final Environmental Impact Statements in 1980 for the MIM and CSR proposal. An Assessment of the Environmental Impact of the Honeymoon Project carried out by the South Australian Department for the Environment was completed in May 1981. The assessment made several recommendations regarding 'excursions', that is, unplanned or inappropriate flows of fluids.

South Australian and Commonwealth approval for Honeymoon was granted for exploitation of the Honeymoon deposit at 450 tonnes of U3O8 per annum in 1981.(6) Single well tests and environmental monitoring was performed and a 110 tonne per annum, $3.5 million pilot plant constructed.

MIM acquired CSR's 34.3 per cent of the project after 1983, and held the retention leases over the area. Sedimentary Holdings NL acquired the Honeymoon and Yarramba projects from MIM in February 1996, with funding from Canadian company Southern Cross Resources. The deposit remains under the control of Sedimentary Holding NL, through Southern Cross Resources, which plans to commence production once appropriate approval is given.(7)

Figure 1. Locality map for the Beverley and Honeymoon proposals, including the operating Olympic Dam mine. The Great Artesian Basin is indicated by the light grey shading and groundwater flow directions in the basin are indicated by arrows.(8)

Figure 1. Locality map for the Beverley and Honeymoon proposals, including the operating Olympic Dam mine

The ancient river channel in which the Honeymoon deposit exists is known as the Yarramba paleochannel. This sandstone channel is confined from the surface by a 60 metre thick sequence of clays and silts above the aquifer system. In February 1997, a resource of 6812 tonnes of U3O8 at 0.15 per cent was defined at Honeymoon with further inferred resources at Yarramba. The South Australian Government made the Declaration of Environmental Factors for Honeymoon, a preliminary phase in the Environmental Impact Statement process in March 1998. A twelve-month field trial of the ISL mining method at Honeymoon commenced following the declaration. The South Australian Minister for Primary Industries, Natural Resources and Regional Development, Mr Rob Kerin has indicated that 'our preliminary environmental impact statement will be out by early June with the final EIS by September'.(9) Southern Cross Resources plans to commence commercial production of 500 tonnes of U3O8 at Honeymoon by mid-1999.(10)

Beverley is located north-west of Honeymoon, about 350 kilometres north-east of Port Augusta or 520 kilometres north of Adelaide. Geologically similar to Honeymoon, Beverley is also a sandstone-type paleochannel deposit. Composed of three ore lenses, Beverley is at a depth of 110 to 140 metres below the surface. About 11 500 tonnes of U3O8 at 0.27 per cent are considered recoverable from Beverley according to published estimates, making it a relatively large ISL prospect. More recently, following geological re-evaluation, estimates put the Beverley deposit at 21 000 tonnes of uranium. Plans to mine the deposit by ISL at 900 tonnes of U3O8 per annum were abandoned in 1983 when the South Australian Government refused to grant permission for the project to proceed due to the ALP's three mine policy.(11) An affiliate of General Atomics Corporation of the US, Heathgate Resources currently owns Beverley.

Heathgate undertook hydrogeological tests and the operation of a continuous field leach trial in 1997-98 with the approval of the South Australian Government. The field leach trial consisted of one production well and four injection wells on a 25 metre grid spacing. Testing yielded around 75 kg of U3O8 per day from the pilot plant, confirming that commercial production rates would be around 900 tonnes of U3O8 per annum. Work on the Environmental Impact Statement for Beverley is proceeding and Heathgate Resources is working towards the commencement of production by mid-1999.(12)

Geology

Uranium ore bodies suitable for ISL occur exclusively as sandstone hosted roll front deposit type. These deposits are formed in ancient river channels covered by more recent sediments. The ancient river channels are composed of porous, permeable sandstones which are bound above and below by impermeable clays and mudstones. The uranium occurs within the porous, permeable sandstones, generally as flat lying bodies with rolled fronts.

The uranium concentration or grade of the ore bodies depends upon the processes of formation and the amount of naturally occurring dissolved uranium available in the groundwater. Uranium ore bodies may also be C shaped or merely occur as widespread low-grade mineralisation within the permeable sandstone. The economic mineralisation was formed by the movement of groundwater-bearing oxidised uranium minerals through the permeable sandstone as a confined aquifer, with precipitation of the uranium minerals occurring at the oxidation-reduction interface. The sandstones have relatively high background levels of uranium (and other metals), which are mobilised by oxidised (surface) water. Where contact with oxygen-poor (reducing) water occurs, the uranium precipitates. A generalised interpretation of a sandstone hosted roll front deposit is shown in Figure 2. The uranium minerals are generally uraninite (UO2) or coffinite (USiO4) coatings on individual sand grains. The ore minerals are often associated with pyritic and humic components in the porous, permeable sandstone matrix. Both the Beverley and Honeymoon deposits in South Australia fit these criteria.

Figure 2. Generalised cross section of a sandstone hosted roll front type uranium deposit.(13)

Figure 2. Generalised cross section of a sandstone hosted roll front type uranium deposit.(13)

Sandstone hosted roll front uranium ore deposits must be under the water table to be considered for ISL. The ancient river channels (paleochannels) are comprised of porous permeable sandstones bounded by impermeable mudstone; as such the water table associated with the deposit may be limited to that channel. Ore formation occurs through uranium-bearing groundwater being focussed through the paleochannel to a chemical boundary. The uranium minerals such as coffinite and uraninite precipitate over geological time to form mineralised ore bodies. The ISL process is essentially a reversal of the ore formation process, dissolving the uranium minerals through reduction using treated water injected around the ore.

Technology of Leaching Systems

ISL uranium mining was first trialed in Wyoming during the early 1960s, and put into production in the 1970s. Twelve ISL projects are licensed to operate in the United States (US) today, in Wyoming, Nebraska and Texas. The mines provide some 85 per cent of US uranium production, yet most of the mines are less than 10 years old.(14) ISL mining contributed a larger proportion of historical uranium production in the Former Soviet Union (FSU) than it did in the US, but the FSU only released information on this recently. The timing of ISL in the FSU was similar to that in the US, with testing in the Chelyabinsk region in 1960. Mining using ISL commenced in Uzbekistan, Ukraine and Kazakhstan during the 1960s. Full scale ISL mining began in the Czech Republic and Bulgaria in 1970-71.(15) Significant environmental issues, such as ground water contamination and surface pollution, have become apparent where ISL mining has been applied in these FSU countries following the collapse of the Soviet Union.

ISL utilises a chemical solution injected below the water table to oxidise uranium minerals such as coffinite and uraninite. When oxidised, the uranium mobilises into the leach solution forming uranium-bearing pregnant liquor. The solution is then brought to the surface for processing. Only the leaching part of the ISL process is unique; once the uranium is in solution the recovery and processing phases are carried out using conventional uranium processing technology on the surface.

The leach solution is prepared by the addition of chemicals (oxidising, alkaline and acidic, depending upon the process) to water pumped from the aquifer containing the uranium deposit. Once pumped back into the aquifer, groundwater flow moves the leach solution within the deposit and allows control of the solution during operation. By drawing more groundwater from the aquifer than is pumped back in, what is known as a 'cone of depression' is achieved in the water table, providing control over the groundwater flow in the aquifer. Following mining, the restoration of the natural state of aquifer mechanics is achieved by plugging the inlet and outlet wells. The time taken for full restoration depends upon the leachate used, up to about 20 years.

Figure 3 shows a generalised ISL operation applied to a sandstone hosted roll front uranium deposit. The wells are cased with PVC and grouted with concrete to ensure the flow of leach solution only to and from the ore zone, so that unintended aquifer impacts are avoided. Typically the ISL production wells are sited on a grid spaced at 15 to 30 metres. The leachate solution is pumped into the aquifer through the injection wells into the zone of the cone of depression. The cone of depression results in a consistent flow back towards the retrieval wells. As the leachate flows through the porous, permeable sandstone, uranium mobilises due to the leachate chemistry and is pumped back to the surface, through the retrieval wells. Monitoring wells are situated throughout and surrounding the operation, to ascertain any unanticipated flows. This ensures economic and environmental standards are realised.

A typical wellfield has a production life of less than three years. Most of the uranium is recovered in the first six months of operation and total recovery may be around 80 per cent. Over time, production flows decrease as clay and silt are trapped in the permeable sediments. Reversal of the flow between injection and production wells can reduce this effect.

The solution with dissolved uranium from ISL mining is pumped to the treatment plant, where the uranium is removed by conventional treatment technologies, such as ion exchange or solvent extraction. Most of the solution is returned to the injection wells, but some is bled off as waste water. As this water is contaminated with radium, arsenic and iron, barium chloride is added to precipitate the radium, prior to disposal in evaporation basins (radium is removed due to safety considerations). The wastewater bleed ensures that there is a steady flow of groundwater into the wellfield from the surrounding aquifer, as a consequence of the cone of depression in the water table. This prevents both the loss of uranium to the mine and the contamination of the surrounding aquifer system, addressing environmental and economic considerations.

Two alternative leaching systems are employed. Alkaline systems, developed in the US, use oxygen and carbon dioxide dissolved in groundwater and have a pH of 6.8 to 7.5. ISL uranium miners in the US exclusively use the alkaline system. A system utilising an acid leachate was developed in the FSU, and uses sulphuric acid dissolved in groundwater to form a solution with a pH of 2.0 to 2.8 (around that of household vinegar). (16)Both systems have advantages depending upon the geological environment in which the uranium ore occurs.

Figure 3. Generalised cross section of In Situ Leaching Process applied to a sandstone hosted roll front type uranium deposit.(17)

Figure 3. Generalised cross section of In Situ Leaching Process applied to a sandstone hosted roll front type uranium deposit.(17)

The acid method is proposed for the Australian deposits. Acid leaching is often the more effective technique, but the requirement for acid resistant pipes and pumps adds significantly to costs. The acid method is not employed in the US largely due to the occurrence in that country of heavy metals, such as cadmium, in the ore bodies. The acid method leaches out these heavy metals, wasting leachate and creating disposal issues, adding to operational costs. This problem is not present in the Australian proposals, the sands hosting the ore bodies being devoid of heavy metals.(18) Testing of the alkaline method at the Australian proposals showed that clay swelling in the sands chokes off the aquifer. The alkaline method is rendered ineffective at the Beverley and Honeymoon deposits by the restricted leachate flows. Testing of the acid method has not resulted in the same degree of clay swelling and aquifer blockage.

The alkaline method can have a lower impact on the aquifer and host rock in which the ore body occurs relative to the acid technique. Restoration of aquifers following ISL by the alkaline method can be quicker than where the acid method is used, which is a key advantage of the alkaline method. Restoration of the Beverley and Honeymoon aquifers to potable water however, would be an unreasonable standard, as the pre-mining condition is salty and radionuclide contaminated. Both methods are considered appropriate for the Beverley and Honeymoon proposals in terms of restoration; the considerations above (especially the clay-swelling problem) preclude the use of the alkaline methods.

ISL mining employing the acid technology for non-uranium minerals has occurred in Australia. The Gunpowder mine, north of Mount Isa in Queensland has used ISL technology to extract copper. Leaching or solvent extraction of broken ground (fragmented through blasting) at Gunpowder commenced in the early 1990s when Adelaide Brighton owned the mine. The current owners of the mine (Aberfoyle) are scaling back the sulphuric acid leach operations for economic reasons. Due to the lack of confining strata (the system is not sealed by impermeable clay units), the treatment liquor tends to be lost to the somewhat alkaline surrounding rock, which in turn neutralises the acid. Also the blasting tends to be inconsistent leading to variable particle size, thus inadequate or inconsistent surface area is exposed for leaching. In contrast naturally occurring sandstones such as those at Beverley and Honeymoon have fairly consistent particle size distribution. Environmental issues have not arisen as a consequence of the acid leaching operation at Gunpowder. However, problems with stormwater drainage from the mine have been documented, where contaminated water has resulted in the deaths of fish and crocodiles.(19)

Environmental Considerations

The Australian uranium industry generates significant differences of opinion as reflected in the political arena. Arguments against the mining and export of uranium are based on economic, social, biological, genetic, safety and environmental grounds. Furthermore, community disquiet exists over the nuclear industry in general.(20) The emergence of climate change as an issue and the recent international agreement in Kyoto to introduce binding carbon dioxide emission growth reduction targets, means that pressures exist to increase non-fossil fuel power sources in signatory countries. Nuclear power by definition generates zero greenhouse gas emissions, although minor emissions result from transport and construction. The implementation of carbon taxation, for example, would reduce any price advantage of fossil fuels over nuclear power. Depending upon emission reduction strategies used, the proportion of nuclear power may increase in signatory countries to the Kyoto agreement. Analysis of these issues in full is beyond the scope of this paper, but they may affect developments in the uranium market and play some part in the decisions related to the commencement of ISL uranium mining.

Prior to any mining of uranium or other commodities in South Australia, an Environmental Impact Assessment (EIA) process is required. Commonwealth export controls on uranium mean that approval will be required from the Commonwealth for both the Beverley and Honeymoon deposits. Commonwealth export controls on bauxite and alumina, mineral sands, coal, and Liquid Natural Gas were abolished on 29 May 1997, and controls were left only on uranium. While the requirement for export approval does not necessarily trigger the requirement for Commonwealth approval under the Environment Protection (Impact of Proposals) Act 1974 it is usually the case. For example, the initial proposal for the Beverley mine was made to the Assistant Treasurer, due to requirements under the Foreign Investment Review Board. The Minister for Resources and Energy referred the Honeymoon proposal for environmental approval due to export control requirements, as was the case with the Jabiluka proposal in the Northern Territory.

A baseline standard for groundwater quality is established prior to the commencement of ISL mining. At the cessation of mining, rehabilitation efforts are directed at bringing groundwater quality back to pre-mining condition. During mining, groundwater drawn from the aquifer is either bled off and evaporated or chemically treated for further uranium retrieval prior to reinjection. Waste water bleeding during the ISL operation ensures that the groundwater flow is into the wellfield and not out of it into the surrounding aquifer. The baseline groundwater quality at the ISL projects under consideration in Australia is low, and the water is not potable. For example, at Beverley the groundwater is saline and contaminated with radionuclides. The aquifers in question have uranium ore bodies within them so high levels of radionuclides are present naturally. Most issues associated with ISL mining, as opposed to conventional operations, are related to the effect of mining on groundwater. Such concerns are less critical where saline groundwater is involved, or other contaminants such as radionuclides exceed quality standards.

Overseas examples have shown that the chemical and mechanical conditions in the treated aquifers return to near pre-mine conditions in fifteen to twenty years.(21) However, ISL mining using the acid method in Kazahkstan, Uzbekistan, the Czech Republic and other FSU countries has resulted in significant environmental problems, such as contaminated groundwater beyond the mineralised area. These problems are attributed largely to the methods employed in a system where uranium production was the main measurement criteria. Massive head pressures were employed in these ISL operations to force solutions through relatively impermeable aquifers. In one case the solution revolve times were 18 months, as opposed to times in the Australian proposals which are 5 to 7 days. Furthermore, well casing design in the FSU was deficient, resulting in solution leakage into target aquifers. Current technology uses non-corrosive PVC piping with a cement grout to remove problems with leakage. Similarly, the Australian proposals will include monitoring wells; thus problems will be identified at an early stage allowing appropriate remedial action.

Mining through ISL methods means that no human contact with the ore body occurs. The ore is accessed remotely through drill holes, similar to extraction through oil wells. Roads, diamond drill holes, processing plants and evaporation ponds need to be created, but underground or surface materials handling is not required. Capital costs are less for ISL mining than they are for conventional mining methods; similarly the requirement to import equipment is reduced. ISL reduces the exposure of workers to conventional industrial and radiological risks, relative to underground mines and to a lesser degree open cut mines. Radon is a radioactive decay product of uranium, a colourless odourless gas. Miners exposed to high doses of radon at the Radium Hill mine in the 1950s and 1960s have a high likelihood of contracting lung cancer.(22) While standards in conventional mining operations try to maintain low levels of exposure, ISL mining removes the risks of this type of exposure, although the usual radiation safeguards apply. The ore rock remains underground and no workers enter the ore zone; there is no trapped radon gas and no ore dust. Employee numbers are limited compared to conventional mining operations. The monitoring of employees for radiation is ongoing, through the use of personnel dosimeters, along with routine monitoring of air, dust and surface contamination. (23)

Accidents in conventional mining operations are often industrial as much as 'mine' related, stemming from the large amounts of material moved and the scale of equipment involved. Materials-handling risks with ISL mining are limited to drums of product; no waste rock (overburden or tailings) or ore handling is required. As no conventional blasting or earth moving occurs using ISL there is minimal surface disturbance and the site may be readily restored to pre-mining conditions. Avoiding the crushing of ore-bearing rock through ISL means that there are no tailings (crushed waste rock) left over following mining. Water use relative to conventional mining is limited and there is little dewatering of aquifers using the ISL technique as it requires a nearly complete water table to be effective. (24)At the cessation of mining, ISL wells are sealed or capped and process facilities are removed. Roads, building sites and any evaporation basins can then be revegetated or capped, and the land can revert to its previous uses.

In Situ Leaching Impacts upon Aquifers

The impact of ISL upon aquifers depends upon the technique used. Where the alkaline extraction method is used, such as in the US, experience has shown that aquifers can be routinely restored to pre-mine quality. The US Nuclear Regulatory Commission concluded that for alkaline leach mining, 'based upon the accumulation of operation data and information, it has become apparent that ISL operations pose no significant environmental impacts'.(25) Information on the use of acid leaching, the method employed in the FSU and proposed for Australia, is less detailed. Non uranium acid leach proposals have been licensed in the US, for example BHP Copper's Florence acid ISL mining project in Arizona.

Documented cases where acid leaching was applied show that the aquifer has returned to baseline conditions within twenty years. Post leach monitoring suggests that the movement of elevated levels of substances extends only a few hundred metres from the boundary of the leached area.(26) Significant aquifer damage in FSU countries as a consequence of acid ISL mining has been documented. Groundwater contamination has been identified in Bulgaria, the Czech Republic, Kazakhstan, and Uzbekistan. For the Czech Republic acid ISL mining has resulted in the contamination of groundwater in Bohemia, in water resources known as the Cenomanian and Turonian. Naturally occurring groundwater in Kazakhstan exceeds local drinking water standards due to presence of uranium.(27) ISL mining has been used in Uzbekistan for more than thirty years, and during the earlier phases the environment and aquifer quality were not given high priorities relative to the maintenance of uranium production. Aquifer impact from acid ISL mining in Uzbekistan has occurred in the Navoi area, where authorities are working with other specialists from the FSU and international organisations towards reclamation and restoration.

Both the Beverley and Honeymoon deposits in South Australia are in the vicinity of the Arrowie sub-Basin of the Great Artesian Basin (GAB). The deposits exist in the southern extremity of the basin, where flows are generally out of the basin to the south. The confined and perched aquifers of the Beverley deposit lie above GAB sediments and the Cadinowie aquifer formation. The water-bearing aquifers of the GAB end about 60 kilometres north of the Honeymoon deposit, as shown in Figure 1.(28) The majority of GAB recharge occurs on the western slopes of Great Dividing Range in Queensland and NSW.

Marketing of Uranium

During the initial years of the uranium market, its importance in weapons programs and as a strategic resource led to a frenetic, government-dominated market where prices were bid far beyond the cost of production. The situation changed in the 1980s and the uranium market has increasingly resembled that for other commodities. Except where production is subsidised for national security reasons, high cost producers have been driven from the market. Ore bodies of the sandstone hosted roll front type and one other known as the unconformity type are generally the cheapest to mine. Unconformity type deposits exist only in Australia and Canada, while the sandstone deposits are more common. Sandstone deposits that can be mined by ISL maintain a significant economic advantage. Also relatively lower grades of uranium may be extracted relative to conventional mines. ISL mining requires low capital and labour input, and provides production flexibility. The cost of ISL mining increases with depth; in the US a maximum depth of 300 metres is used and in Kazakhstan 550 metres. Both the Australian deposits are at around 100 metres, placing them at an advantage over deeper deposits. Due to the relative economic advantages of ISL mining over conventional alternatives, the mining of Beverley and Honeymoon is likely to survive even severe market downturns.(29)

The excess inventory of uranium that has supplied the market with low price uranium for a number of years is near exhaustion. A need is anticipated for new low cost uranium production centres in the next few years.(30) The value of Australian uranium exports is likely to increase up to 2003, with stronger prices and a doubling of production.(31) The main markets for Australia are Japan, South Korea, the European Union and the United States. Potential new markets are developing in Taiwan and China.(32)

Conclusions

ISL mining is a relatively inexpensive method of uranium production. Solvent extraction mining is already in use in Australia for copper at the Gunpowder mine in Queensland. Traditional forms of mining, both underground and surface, require massive amounts of materials-handling with inherent risks to employees and significant localised environmental impact. ISL mining offers relatively limited environmental impact. Only roads, diamond drill holes, processing plants and evaporation ponds need to be created. The reduced amount of materials-handling offers significant safety benefits for employees, along with reduced dust and water management concerns. The ISL mining process draws groundwater into the aquifer rather than sending it out into the water-bearing strata, for both environmental and resource recovery reasons. Where the process is managed properly and monitored, aquifer risks are limited. ISL offers a relatively cheap mining method, allowing producers to occupy the lower cost segment of a flooded market, should this occur.

The commodity being mined, rather than the mining process, remains the major problem and contentious issue with ISL mining of uranium. Mining of uranium in Australia has a long history of public debate and government intervention. Policy making on the part of governments since the discovery of uranium in Australia has been ad hoc.(33) Development of Beverley and Honeymoon will further test policy considerations. Opposition to uranium mining and the nuclear industry in general is likely to generate concern over these mines. In turn criticism of the mining technique is likely to appear. These perceptions are likely to impact upon the Honeymoon and Beverley development proposals; to what degree remains to be seen.

Acronyms

BHP

Broken Hill Proprietary Company Limited

CSR

Colonial Sugar Refining Company Limited

EIA

Environmental Impact Assessment

EIS

Environmental Impact Statement

FSU

Former Soviet Union

GAB

Great Artesian Basin

ISL

In Situ Leaching

MIM

Mount Isa Mines Limited

NSW

New South Wales

PVC

Poly Vinyl Chloride

US

United States

Endnotes

  1. Resources and Energy Policy, The Liberal and National Parties, 17 February 1996.

  2. Uranium [Red Book], 1995 Resources, Production and Demand, OECD and IAEA, Paris 1996.

  3. Panter R. & Kay P., Chronology of ALP Uranium Policy 1950-1994, Parliamentary Research Service, Canberra, 12 September 1994.

  4. Innes S., Honeymoon over - now work begins, Adelaide Advertiser, 21 February 1998.

  5. In Situ Leach Mining of Uranium, Nuclear Issues Briefing Paper 40, Uranium Information Centre Ltd, Melbourne, January 1998.

  6. Australia, House of Representatives 1981, Debates, vol. HR125, p. 2676, 1981.

  7. Register of Australian Mining 1997/98, Resource Information Unit, Perth.

  8. Adapted from http://www.dnr.qld.gov.au/water/artesian_basin/basin.html.

  9. Moodie D., Uranium mine go-ahead, Adelaide Advertiser, 18 March 1998.

  10. Honeymoon Cleared for Field Trials, UIC Newsletter, March-April 1998, Uranium Information Centre, Melbourne.

  11. In Situ Leach Mining of Uranium, Nuclear Issues Briefing Paper 40, Uranium Information Centre Ltd, Melbourne, January 1998.

  12. Beverley Resources upgraded, UIC Newsletter, March-April 1998, Uranium Information Centre, Melbourne.

  13. Adapted from, Underhill D., In situ leach uranium mining - current practice, potential and environmental aspects, ABARE Outlook 98 Conference, Canberra, February 1998.

  14. In Situ Leach Mining of Uranium, Nuclear Issues Briefing Paper 40, Uranium Information Centre Ltd, Melbourne, January 1998.

  15. Underhill D., In situ leach uranium mining - current practice, potential and environmental aspects, ABARE Outlook 98 Conference, Canberra, February 1998.

  16. In Situ Leach Mining of Uranium, Nuclear Issues Briefing Paper 40, Uranium Information Centre Ltd, Melbourne, January 1998.

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