Uranium mining

Picture of uranium ore.

Uranium mining is the process of extracting uranium ore from the ground. Generally speaking, uranium mining is no different from other kinds of mining unless the ore is of a high grade. In the case of high-grade uranium mining, there are specific safety and handling techniques, which have to be employed to limit worker radiation exposure and to ensure the safety of the general public and the environment. A majority of uranium is mined as the primary product; in many cases, uranium is recovered as a by-product from mining other ores, such as copper, gold, or phosphate. Often, the concentration of the uranium recovered is quite low, but it can still be recovered at a competitive cost.

Uranium is mined mostly for use in generating electricity through nuclear reactors, while a small proportion of mined uranium is used to produce medical isotopes and in marine propulsion. Uranium is not a rare element on Earth, occurring in 2.8 parts per million in the Earth's crusts, and occurring in fairly large quantities in various geological settings. It is more abundant than gold, silver, or mercury, has a similar abundance to tin, and is slightly less abundant than cobalt, lead, or molybdenum. Uranium also occurs in the oceans of the world, though it tends to be in low concentration and, therefore, is not considered to be worth recovering in those areas.

Example of where Uranium tends to occur.

Ore deposits of uranium are graded depending on the percentage of uranium. For example, most common uranium mines have ore grades in excess of 0.10 percent or greater than 1000 parts per million. Previously, for example, in the 1960s, this grade would have been seen as respectable. However, more recently, uranium mines in Canada have large amounts of ore of up to 20 percent uranium. Other mines continue to successfully operate with very low grades, down to about 0.02 percent uranium. While uranium mines operate in around 20 countries, over 55 percent of the world's production in 2022 came from just ten mines in five countries.

The global demand for uranium in 2023 was 65,650 tonnes and is expected to continue to rise to 83,840 tonnes by 2030. It has the potential to rise to 130,000 tonnes by 2040, especially as nuclear energy-producing technologies are expected to become more popular as states look for emissions-free energy production. A small amount of the demand continues to be used for naval propulsion and for medical and research purposes. About 46 percent of uranium comes from conventional (open-pit and underground) mines, while 50 percent comes from in situ leach, while the remaining percentage is recovered as a by-product from other mineral extraction.

Secondary supplies of uranium have accounted for around 12,000 tonnes of uranium per year. This can change rapidly, as a significant portion of the secondary supply of uranium is provided by the decommissioning of nuclear warheads, or they come from government and utility stockpiles or from depleted uranium left over from historic enrichment (which can be re-enriched with newer processes), and a small amount comes from recycled uranium which can be reprocessed and used as fuel. Rapid changes in supply have come when states have declined to decommission warheads, such as in 2014, when Russian supplies of blended-down high-enriched uranium—often exported to the United States—ceased.

There are several aspects of consideration when it comes to the economics of uranium mining. The first such consideration is where the orebody is located, the grade of the orebody, the nature of the ore, the depth of the ore, and other related infrastructure issues. Countries where the orebody is located will come with different risks, which affect their attractiveness for mining investment, different royalty and tax regimes, and different availability of skilled workers. These factors will heavily influence mineral exploitation long before an orebody is identified.

Otherwise, the main economic consideration is the quantity, geological character, grade, hardness, and depth of the orebody as that will determine the required capital investment. Other infrastructure issues include engineering and workforce, especially as a mine at a remote site will cost more. This comes down to a set of considerations which are usually broken down into conventional categories: capital costs, operating costs, and indirect costs.

These costs include the cost of site preparation, construction, manufacture of a plant, and commissioning and financing of both the mine and associated mill. Building a large-scale mine takes workers, large amounts of steel and concrete, thousands of components and systems to provide electricity, a ventilation system (if underground), information systems, and control and communication systems. The expenditure required to commit to a mine project may or may not be capitalized, as capital costs can be reported with the financing costs included or excluded. If financing costs are included, then the capital costs change materially in proportion to the construction of the project and with the interest rate or the mode of financing employed. Upfront capital expenditure and ongoing capital expenditure to sustain the operation are involved in the long term.

The operating costs of a mine include the cost of removing the ore from the ground, concentrating it for sale, the reagents, energy, labor, environmental management, administration, freight, marketing, and eventual decommissioning and disposal of wastes. These costs can include royalty payments to the owner of the minerals, which are normally expressed as relative to the unit of output. Operating costs, especially the ongoing costs for production, both variable and fixed, are sometimes reported as the "cash cost" of a mining operation per unit of output.

The indirect costs of a uranium mining operation include depreciation and amortization of the assets, interest on loans, extraordinary costs, and sustaining costs of related exploration and mine development in the case that these are not capitalized. Indirect costs may be hard to quantify for reporting since they include non-cash items and servicing capital over the life of mine. While the cash cost of production is a short-term metric, including the indirect costs gives a life-of-mine perspective.

Open-pit mining, also known as strip mining, is the removal of surface soil and uneconomic rock to get to ore deposits. Ore grades are generally less than 0.5 in these types of mines, and these types of mines are only possible if the uranium ore is near the surface. Near the surface is usually defined as no lower than 400 feet. In this mine type, waste rock or overburden (which is the material removed to get at the ore of interest) is stored near the open pit. These pits are also structured around a series of benches or steps, which are cut into to make the removal of ore easier and can include one or more roads to allow earth and ore haulers to navigate the areas. Depending on the level of water in a pit, pumps can be used to remove the water.

Open-pit mining tends to be less expensive than underground mining, with better ventilation (which can be important for uranium mining), and with newer mines subject to stricter environmental, safety, and health guidelines, the impact of open-pit mines has been limited. New open-pit mines are required, in many jurisdictions, to be reclaimed at the end of the mine's life. Tailings piles have to be built to different standards, depending on the waste, with lower subgrades, synthetic liners, leak detection wells, and a maximum size of 40 acres. Newer mines often require dust control to limit workers and environmental exposure to radon.

These mines also have the largest footprints of any mining operation. They generate a massive amount of waste rock, and the waste rock—if not considered economic to be effectively mined—can become hazardous to the environment once exposed to the atmosphere. Further, remediation of these mines is incredibly costly and time-consuming, especially when considering groundwater restoration, which can impact a mine's overall economic efficiency. And mine workers' health can be compromised due to dust and exposure, and nearby communities' health can be impacted based on the dust, noise, and other potential issues of open-pit mining.

Underground mining is used to get at higher concentrations of uranium that are too deep to get at from an open-pit mine. The ore is drilled and blasted to create debris, which can be transported to the surface and then to a mill. An underground mine is established only if the amount and quality of the uranium at a site is considered sufficient to accept the cost. Once a site survey is complete, a large vertical shaft is dug to the depth of the ore. Once done, horizontal tunnels, ramps, and chambers are built to allow for the mining of uranium.

Underground uranium mine schematic from McArthur River, Canada.

Underground mining tends to be achieved using one of two main methods: the raisebore method, which uses a revolving tool to dig into a uranium deposit, and the mined uranium falls into a truck below the drill; or the jet bore mining method, which uses pressurized water to remove ore, which can then be pumped to the surface. These mines tend to have a smaller footprint than an open-pit mine and create less waste rock. Further, with advances in ventilation, robotic mining, and monitoring technology, underground mines are getting safer for mine workers.

However, these mines do tend to be expensive, have a potential to negatively impact local aquifers, and can be more expensive than open-pit mines to remediate. In older underground mines, dust, radon, and diesel fumes have been a serious threat to the health of the miners. In jurisdictions with poor safety regulations in terms of miners' health and mine ventilation or dust control, the mines can be incredibly damaging to miner health and the local environment.

Example of an in situ leach uranium mine.

In this method, the ore is generally fairly deep and cannot be mined with open pits and may be (based on any number of factors) more practical than other underground mining methods. These methods leave little environmental disturbance at the ground surface level and do not generate tailings or waste rock. The method involves recovering uranium ore by dissolving it from uranium-bearing minerals by injecting a carbonated solution or mild acid and pumping the leached uranium in a pregnant solution to the surface, where it can be recovered.

Uranium ISL tends to use native groundwater in the orebody fortified with a complexing agent (depending on the region, this is either an alkaline solution or a weak sulfuric acid), and in some cases, is mixed with an oxidant. It is then pumped through the underground orebody to recover the uranium by leaching. The pregnant solution is returned to the surface, and the uranium is recovered in the same way as any other uranium processing plant. ISR requires that an ore deposit rock structure be permeable and have an underlying impermeable confining layer beneath the mineralization.

Above-ground view of an in situ leaching uranium mine.

ISL mining can accomplish the removal of uranium without any major ground disturbance. The leaching solution dissolves the uranium before being pumped to the surface treatment plant, where the uranium is recovered. The leaching method uses either an acid or alkali solution, depending on the acidity of the groundwater and what regional regulations and restrictions allow for, and the leach is pumped through an aquifer through a series of injection wells, which migrates the aquifer and the leach with uranium to an extraction well where the liquid is pumped to the surface for processing. The method uses either a satellite or a central processing plant. This allows it to be used for relatively small deposits to make them viable, where other mining methods may make mining a small deposit uneconomical.

Some of the potential negatives of ISR/ISL include the possible contamination of local aquifers (although in some regions, there are environmental regulations to prevent this from happening, including the use of non-toxic and neutral solutions to leach uranium), waters have to be pumped and monitored, even after active extraction has stopped, and wastewater has to be disposed of responsibly, reducing environmental impact and the potential impact on nearby human settlements. The public fears associated with this method—and uranium mining in general—can also have a negative impact on ISL/ISR methods.

Example of a heap leach project in Africa.

Some uranium, generally very low-grade uranium, is treated by heap leaching. In heap leaching, the ore is broken and stacked about 5 to 30 meters high on an impermeable pad and irrigated with acid (sometimes an alkaline) solution over many weeks. The resulting liquor is collected and treated to recover the uranium, usually using ion exchange. Once yields of significant uranium cease, the liquor is removed and replaced with fresh ore. Recoveries are typically of 50 to 80 percent of material. And the resulting depleted material, which has the potential to cause pollution, is required in most jurisdictions to be emplaced securely to not affect surface or ground water; this typically occurs in mined-out pits.

Example of the workflow of mining uranium.

Conventional mines will include a mill where ore is crushed and ground to liberate mineral particles, which are then leached in tanks with sulfuric acid to dissolve the uranium oxides. The resulting solution is further processed to recover the uranium. In some cases, such as in South African gold mines, the tailings require a pressure leach to recover the uranium. In some cases, a physical beneficiation process is used to further concentrate the ore before chemical treatment. These processes can include radiometric sorting, screening or gravity sorting, or a process known as ablation.

Most of the ore is barren rock or other minerals which, after the leaching process, remain undissolved. These solids or "tailings" are separated from the uranium-rich solution. The separation is usually achieved by allowing them to settle out of the solution. The solution is filtered and the uranium is recovered, often in some form of ion exchange or solvent extraction. The uranium is stripped from this resulting liquor and precipitated, and the final chemical precipitate is filtered and dried to recover the uranium.

From open-cut mines, there are substantial volumes of rock and overburden waste. These waste products are generally placed near the open pit to be used either in the rehabilitation of the mine or shaped and revegetated where they are placed. Uranium is associated with radioactive elements, such as radium and radon, which arise from the radioactive decay of uranium over a few million years; therefore, although uranium is not highly radioactive, the ore has to be handled with care for occupational health and safety reasons.

The management of tailings, run-off, and specific mining methods are all subject to government regulations and inspection. For example, in Australia, according to the Code of Practice and Safety Guide: Radiation Protection and Radioactive Waste Management in Mining and Mineral Processing was published in 2005 and updated in 2015 and determines throughout its terms how these waste products and mines are managed. Other jurisdictions have similar regulations.

Example of a tailings management site.

Solid waste products from the milling operation are called tailings. These range in character from slimes to coarse sounds and comprise the original ore and contain most of the radioactivity in it. Often these tailings of uranium mines contain all the radium from the original ore. In underground mines, these tailings may first be cycloned to separate coarse materials, which can then be used for underground fill, while the balance is pumped as a slurry to a tailings dam. Often tailings dams are worked-out pit mines or an engineered structure.

One of the products of uranium mining, and more specifically the decay of radium, is radon gas. Radon and its decay products are radioactive and measured with tailings (where, as noted, much of— if not all—the radium remains) has to deal with the emission of radon gas and its decay products. Many jurisdictions have a "zero discharge" policy for any radon or related pollutants, and this usually means a tailings dam is covered by water to reduce radon emission and surface radioactivity. The water needs to be recycled or evaporated, as the radium in the water is radioactive and relatively soluble.

Overhead look of the rehabilitation of the Ranger mine in Australia.

Once a mining operation is complete, the tailings dam is typically covered by a few meters of clay and topsoil with enough rock to resist erosion. This covering is intended to reduce gamma radiation levels and radon emanation rates to those levels normally experienced in the region of an orebody, and are used to help establish a vegetation cover. Further, open-pit and underground mines have their tailings returned to them to rehabilitate the mine—essentially helping to fill the underground shafts or the large open pits.

Example of a mine rehabilitation site in jeopardy at Rum Jungle in Australia.

At established ISL/ISR operations, after mining is completed the groundwater is expected to be restored to a baseline standard determined prior to the start of the mining operation. This is usually potable water or stock water (often determined by less than 500 ppm of total dissolved solids). And it requires contaminated water drawn from an aquifer to be evaporated or treated prior to reinjection. However, in some regions, especially in Australia, the groundwater can be of poor quality to start with. For example, at the Beverley ISL site, the original groundwater in the orebody was fairly saline and orders of magnitude too high in radionuclides for any permitted use. The water in one of these types of sites is typically returned to groundwater in better condition than found, but the water quality will revert to its original condition over time.

Further, upon the decommission of the ISL/ISR mine, the wells are sealed or capped, process facilities are removed, and any evaporation pond is revegetated to help the land revert to its previous uses. Mining is generally considered a temporary land use, which requires the mined land to be rehabilitated to be suitable for its original use, or left fit for other uses. In various jurisdictions, governments hold bonds to ensure proper rehabilitation in the event of corporate insolvency.

Example of safety equipment worn by uranium miners.

One of the challenges of mining uranium comes with the traditional challenges of mining for workers complicated by the radioactive elements associated with uranium. Depending on the jurisdiction, there can be comprehensive guidelines and regulations that stipulate the conditions in which miners are allowed to work. For example, in Australia, the Code of Practice and Safety Guide for Radiation Protection and Radioactive Waste Management in Mining and Mineral Processing outlines the conditions under which miners are allowed to work, and those conditions that are considered unacceptable. This includes setting strict health standards for radiation and radon gas exposure for workers and for members of the public.

Often the regulations are around the ventilation of mines. Radon, a radioactive inert gas, is released in small quantities when uranium is mined and crushed. The radon gas is present in most rocks and minute traces are present in the atmosphere and part of the natural radiation all humans receive daily. However, in the case of mining, the release of radon reaches unsafe levels without proper ventilation, and, therefore, mines require proper ventilation for the safety of their workers. Underground mines can use powerful fans that work to keep radon levels at very low and safe levels; while open-cut mines are naturally well-ventilated.

Gamma radiation is another hazard to those working close to high-grade ores. The radiation comes principally from uranium decay products, and exposure to this is regulated as required. Dust, in these cases, is suppressed as the dust represents the main potential exposure to alpha radiation and gamma radiation hazard. Other precautions taken to limit the potential health hazards of the radiation associated with uranium mining include the following:

• Forced ventilation systems to ensure exposure to radon gas and radioactive daughter products is as low as possible and does not exceed established safety levels.
• Efficient dust control as dust potentially contains radioactive constituents or emits radon gas.
• Limit the radiation exposure of workers in mines, mills, and tailings areas so that it does not exceed the allowable limits set by authorities. In some mines, this includes mining of very high-grade ore undertaken by autonomous or remote-control vehicles and fully containing the ore where practical.
• The use of radiation detection equipment in all mines and plants, including personal dose badges.
• Imposition of strict personal hygiene standards for workers handling uranium oxide concentrate.

Example of a radiation dosage badge.

To keep workers safe, the workers most likely to be exposed to radiation and radioactive materials are monitored for alpha radiation contamination and are often required to wear personal dosimeters to measure exposure to gamma radiation. Part of this includes the routine monitoring of air, dust, and surface contamination. For ISL mines, the precautions taken are similar to those in a lead smelter, which includes hygiene precautions, and the same radiation protection procedures, despite the fact that most of the orebody's radioactivity remains well underground with minimal increase in radon release and no ore dust.

There are strict controls and conditions related to the use of uranium in various countries, notably Australia and Canada, which are among the largest uranium exporting countries. These safeguards are intended to ensure that the exported uranium is used for peaceful purposes and is at no point diverted for use in military purposes, such as munitions or the proliferation of nuclear weapons. Bilateral agreements to this effect between various governments and countries exist where the countries wish to import uranium and are required to reach such an agreement before sales contracts can be completed.

As explored above, one of the main concerns with working uranium mines is the toxic and radioactive profile of uranium and the associated decay products—radium and radon. Uranium, as a heavy metal, has the potential to cause a spectrum of adverse health effects ranging from renal failure and diminished bone growth to damaging an individual's DNA. Meanwhile, the radioactivity of uranium and its decay products, which is more commonly understood, can cause cancer, shorten life, and cause subtle changes in fertility or the viability of offspring.

Worse, the effects are sometimes delayed for decades or for generations and are not always detected. This leads to many of the regulations for workers' health and those related to public concerns over the potential of the toxicity and radioactivity affecting nearby human settlements due to poor mine controls and the delayed onset of these effects.

With the mining of uranium, there are environmental concerns from radiological and heavy-metal contamination, which can imperil local species and cause human-health impacts, especially if the pollution occurs on public lands or in underground water tables. Pollutants from uranium mining have been shown to contaminate aquatic ecosystems, with pollution that lasts for hundreds of years and threatens downstream communities as well as the fish and wildlife, which rely on these waterways. Fish are especially harmed by these pollutants, which can cause deformities and reproductive problems, which can further be passed through the food chain.

However, to counter these concerns, regulations such as those imposed by the Nuclear Regulatory Commission and Environmental Protection Agency in the United States work to protect the environment and human settlements. This includes mandates of cleanups of accidental uranium waste releases, regulations on abandoned uranium processing sites, and ensuring stored uranium waste is constructed with a 1,000-year compliance period to ensure they can withstand leakage for that period of time. In most respects, conventional mining of uranium is the same as mining any other metalliferous ore, which includes well-established environmental constraints to avoid any off-site pollution. However, due to the radioactive elements associated with uranium, there is further care, which has to be taken during the mining and in the retirement of a uranium mine.