Peak uranium

Uranium mining is the process of extraction of uranium ore from the ground. Over 50 thousand tons of uranium were produced in 2019. Kazakhstan, Canada, and Australia were the top three uranium producers, respectively, and together account for 68% of world production. Other countries producing more than 1,000 tons per year included Namibia, Niger, Uzbekistan, the United States, and China. Nearly all of the world's mined uranium is used to power nuclear power plants. Historically uranium was also used in applications such as uranium glass or ferrouranium but those applications have declined due to the radioactivity of uranium and are nowadays mostly supplied with a plentiful cheap supply of depleted uranium which is also used in uranium ammunition. In addition to being cheaper, depleted uranium is also less radioactive due to a lower content of short-lived and than natural uranium.

Uranium is mined by in-situ leaching (57% of world production) or by conventional underground or open-pit mining of ores (43% of production). During in-situ mining, a leaching solution is pumped down drill holes into the uranium ore deposit where it dissolves the ore minerals. The uranium-rich fluid is then pumped back to the surface and processed to extract the uranium compounds from solution. In conventional mining, ores are processed by grinding the ore materials to a uniform particle size and then treating the ore to extract the uranium by chemical leaching. The milling process commonly yields dry powder-form material consisting of natural uranium, " yellowcake," which is nowadays commonly sold on the uranium market as U₃O₈. While some nuclear power plants - most notably heavy water reactors like the CANDU - can operate with natural uranium (usually in the form of uranium dioxide), the vast majority of commercial nuclear power plants and many research reactors require uranium enrichment, which raises the content of from the natural 0.72% to 3-5% (for use in light water reactors) or even higher, depending on the application. Enrichment requires conversion of the yellowcake into uranium hexafluoride and production of the fuel (again usually uranium dioxide, but sometimes uranium carbide, uranium hydride or uranium nitride) from that feedstock.

History

Early uranium mining

Uranium minerals were noticed by miners for a long time prior to the discovery of uranium in 1789. The uranium mineral pitchblende, also known as uraninite, was reported from the Erzgebirge (Ore Mountains), Saxony, as early as 1565. Other early reports of pitchblende date from 1727 in Jáchymov and 1763 in Schwarzwald. The suffix "-blende" applied by Ore Mountain miners to the mineral long before the discovery of the element uranium indicates a mineral that ''looks'' like it contains some usable metal but (according to then available knowledge) doesn't. Terms for minerals later identified to contain cobalt (c.f. "Kobold" the modern standard German word for goblin) nickel or "Wolfram" (the standard German term for tungsten) were similarly derived from superstitious belief that some sort of "mountain gnome" had somehow "hexed" the minerals to trick (c.f. The German use of the term "blenden" cognate of "blind" for "tricking") the miners. Thus examining old documents about the presence of "worthless" -blende type minerals allowed easier exploration, once the true nature of these ores had been discovered.

In the early 19th century, uranium ore was recovered as a byproduct of mining in Saxony, Bohemia, and Cornwall. The first deliberate mining of radioactive ores took place in Joachimsthal, a silver-mining city now in the Czech Republic and origin of the word T(h)aler and from there dollar. Marie Skłodowska-Curie used pitchblende ore from Joachimsthal to isolate the element radium, a decay product of uranium. This discovery earned her her first Nobel Prize and represents an important step in the history of nuclear physics. Until World War II, uranium was mined primarily for its radium content; some carnotite deposits were mined primarily for the vanadium content. Sources for radium, contained in the uranium ore, were sought for use as luminous paint for watch dials and other instruments, as well as for health-related applications, some of which in retrospect were certainly harmful and some of which must be regarded as nuclear quackery even from a contemporary standpoint. Given that the half life of is almost 2.8 million times longer than that of , tons of uranium had to be processed to derive a few grams of radium, leaving large amounts of uranium with little economic uses. The byproduct uranium was used mostly as a yellow pigment. Ferrouranium started to be used by the Central Powers of World War I as a substitute for materials they could no longer import due to the British naval blockade. At the time both sides of the Ore Mountains were contained in territory controlled by the Central Powers, as the northern flank belonged to the German Empire whereas the southern flank belonged to Austria-Hungary. Given that uranium was mostly seen as a "waste product" in radium-mining at the time, a plentiful supply was available even without scaling up mining. While radium has legitimate evidence based applications in nuclear medicine, the availability of other radionuclides with more desirable properties has all but eliminated the market for radium.

In the United States, the first radium/uranium ore was discovered in 1871 in gold mines near Central City, Colorado. This district produced about 50 tons of high grade ore between 1871 and 1895. Most American uranium ore before World War II came from vanadium deposits on the Colorado Plateau of Utah and Colorado.

In Cornwall, England, the South Terras Mine near St. Stephen opened for uranium production in 1873, and produced about 175 tons of ore before 1900. Other early uranium mining occurred in Autunois in France's Massif Central (whence the name Autunite for a uranium-bearing mineral once mined in the area), Oberpfalz in Bavaria, and Billingen in Sweden.

The Shinkolobwe deposit in Katanga, Belgian Congo (now Shaba Province, Democratic Republic of the Congo (DRC)), was discovered in 1913, and exploited by the Union Minière du Haut Katanga. Other important deposits mined early in the history of uranium mining include Port Radium, near Great Bear Lake, Canada, discovered in 1931; along with Beira Province, Portugal; Tyuya Muyun, Uzbekistan (whence Tyuyamunite); and Radium Hill, Australia.

Atomic age

Because of the need for the uranium for bomb research during World War II, the Manhattan Project used a variety of sources for the element. The Manhattan Project initially purchased uranium ore from the Belgian Congo, through the Union Minière du Haut Katanga. Later the project contracted with vanadium mining companies in the American Southwest. Purchases were also made from the Eldorado Mining and Refining Limited company in Canada. This company had large stocks of uranium as waste from its radium refining activities.

The smaller scale German nuclear program likewise tried to acquire uranium, putting the Berlin based Auergesellschaft, which had been taken from previous Jewish-German owners, in charge of acquisition. A substantial amount of uranium from the Belgian Congo (and thus the same source as the one used by the Americans) fell into German hands when the Wehrmacht conquered Belgium. Another important source was mining in the Ore Mountains (mostly on the Czech side, which had been annexed after the Munich treaty of 1938). While incompetence, bad luck, lack of resources and infighting kept the Germans from ever assembling enough uranium and neutron moderator in a single " pile" to achieve criticality, by the end of the war more than enough uranium had been in German hands to theoretically allow for the construction of a crude reactor on the scale of Chicago Pile-1 or the Soviet F-1 (nuclear reactor) if it had all been assembled in a single place. The Haigerloch research reactor ( :de:Forschungsreaktor Haigerloch) assembled months before the end of the war in Southwestern Germany was an extremely subcritical assembly which lacked both sufficient uranium and sufficient moderator to produce significant amounts of plutonium, let alone heat. A uranium cube thought to have belonged to Werner Heisenberg was analyzed decades later, confirming that the Germans were nowhere near plutonium production.

American uranium ores mined in Colorado were mixed ores of vanadium and uranium, but because of wartime secrecy, the Manhattan Project would publicly admit only to purchasing the vanadium, and did not pay the uranium miners for the uranium content. In a much later lawsuit, many miners were able to reclaim lost profits from the U.S. government. American ores had much lower uranium concentrations than the ore from the Belgian Congo, but they were pursued vigorously to ensure nuclear self-sufficiency. Similar efforts were undertaken in the Soviet Union, which did not have native stocks of uranium when it started developing its own atomic weapons program.

While the Soviet Republics of Kazakhstan and the RSFSR would later become some of the leading uranium producers in the world, immediately after the end of World War II the availability of large uranium deposits in the USSR wasn't yet known and thus the Soviets developed immense mining operations in their satellite states East Germany and Czechoslovakia which had known uranium deposits in the Ore Mountains. The deliberately opaquely named SDAG Wismut (the German term "Wismut" for Bismuth should give the illusion of prospection for a metal the Soviets definitely ''weren't'' after) became the biggest employer in the Saxon Ore Mountains and remote mining towns like Johanngeorgenstadt swelled to ten times their population in a few years. The mining cost immense amounts of money and miners were on the one hand subject to heavier repression and surveillance but on the other hand allowed more generous supply with consumer goods than other East Germans. While production was never able to compete with global uranium market prices, the dual use nature of the mined material as well as the possibility to pay miners in soft currency but sell uranium for hard currency or substitute imports which would've had to be paid for in hard currency tipped the scales in favor of continuing mining operations throughout the Cold War. After German reunification, mining was wound down and the arduous task of rehabilitating the land impacted by mining was begun. In the course of this, some remaining deposits had to be mined to reduce the potential harm from material leaching into groundwater, but this has since ceased as well, making the area in which uranium had been discovered two centuries prior entirely devoid of uranium mining.

In the 20th century, the United States was the world's largest uranium producer. Grants Uranium District in northwestern New Mexico was the largest United States uranium producer. The Gas Hills Uranium District was the second largest uranium producer. The famous Lucky Mc Mine is located in the Gas Hills near Riverton, Wyoming. Canada has since surpassed the United States as the cumulative largest producer in the world. In 1990, 55% of world production came from underground mines, but this shrank to 33% by 1999. From 2000, new Canadian mines again increased the proportion of underground mining, and with Olympic Dam it is now 37%. In situ leach (ISL, or ISR) mining has been steadily increasing its share of the total, mainly due to Kazakhstan. Unlike with coal, particularly lignite, where the biggest producers tend to also be the biggest consumers, the biggest uranium producers, Kazakhstan, Australia and Canada contain only one nation – Canada – who derives a significant proportion of electricity from nuclear power. On the other hand, big users of nuclear power like France, South Korea, India or Japan import most or all of the uranium used in their power plants as they have no or negligible domestic uranium resources. India in particular has been interested in the Thorium fuel cycle for decades, as India has much larger thorium reserves than it does uranium reserves. France historically derived significant shares of its uranium needs from its African colonies and continues to be politically and economically active in those African countries to ensure its uranium supply.

Deposit types

Many different types of uranium deposits have been discovered and mined.
There are mainly three types of uranium deposits including unconformity-type deposits, namely paleoplacer deposits and sandstone-type also known as roll front type deposits.

Uranium deposits are classified into 15 categories according to their geological setting and the type of rock in which they are found. This geological classification system is determined by the International Atomic Energy Agency (IAEA).

Uranium is also contained in seawater but at present prices on the uranium market, costs would have to be lowered by a factor of 3–6 to make its recovery economical.

Sedimentary

Uranium deposits in sedimentary rocks include those in sandstone (in Canada and the western US),
Precambrian unconformities (in Canada), phosphate, Precambrian quartz-pebble conglomerate, collapse breccia pipes (see Arizona breccia pipe uranium mineralization),
and calcrete

Sandstone uranium deposits are generally of two types. ''Roll-front'' type deposits occur at the boundary between the up dip and oxidized part of a sandstone body and the deeper down dip reduced part of a sandstone body. ''Peneconcordant'' sandstone uranium deposits, also called ''Colorado Plateau''-type deposits, most often occur within generally oxidized sandstone bodies, often in localized reduced zones, such as in association with carbonized wood in the sandstone.

Precambrian quartz-pebble conglomerate-type uranium deposits occur only in rocks older than two billion years old. The conglomerates also contain pyrite. These deposits have been mined in the Blind River-Elliot Lake district of Ontario, Canada, and from the gold-bearing Witwatersrand conglomerates of South Africa.

Unconformity-type deposits make up about 33% of the World Outside Centrally Planned Economies Areas (WOCA)'s uranium deposits.

Igneous or hydrothermal

Hydrothermal uranium deposits encompass the vein-type uranium ores. Vein-type hydrothermal uranium deposits represent epigenetic concentrations of uranium minerals that typically fill breccias, fractures, and shear zones. Many studies have sought to identify the source of uranium with hydrothermal vein-type deposits and the potential sources still remains a mystery, but are thought to include preexisting rocks that have been broken down by weathering and force that come from areas of long-term sediment build up. The South Chine Block is an example of a region that has been relying on vein-type hydrothermal uranium deposit demand for the past half century. Igneous deposits include nepheline syenite intrusives at Ilimaussaq, Greenland; the disseminated uranium deposit at Rossing, Namibia; uranium-bearing pegmatites, and the Aurora crater lake deposit of the McDermitt Caldera in Oregon. Disseminated deposits are also found in the states of Washington and Alaska in the US.

Breccia

Breccia uranium deposits are found in rocks that have been broken due to tectonic fracturing, or weathering. Breccia uranium deposits are most common in India, Australia and the United States. A large mass of breccia is called a breccia pipe or chimney and is composed of the rock forming an irregular and almost cylinder like shape. The origin of breccia pipe is uncertain but it is thought that they form on intersections and faults.  When the formations are found solid in ground host rock called rock flour, it usually is often a site for copper or uranium mining. Copper Creek, Arizona is home to approximately 500 mineralized breccia pipes and Cripple Creek, Colorado also is a site that contains breccia pipe ore deposits that is associated with a volcanic pipe.

Olympic Dam mine, the world's largest uranium deposit, was discovered by Western Mining Corporation in 1975 and is owned by BHP.

Exploration

Uranium prospecting is similar to other forms of mineral exploration with the exception of some specialized instruments for detecting the presence of radioactive isotopes.

The Geiger counter was the original radiation detector, recording the total count rate from all energy levels of radiation. Ionization chambers and Geiger counters were first adapted for field use in the 1930s. The first transportable Geiger–Müller counter (weighing 25 kg) was constructed at the University of British Columbia in 1932. H.V. Ellsworth of the GSC built a lighter weight, more practical unit in 1934. Subsequent models were the principal instruments used for uranium prospecting for many years, until geiger counters were replaced by scintillation counters.

The use of airborne detectors to prospect for radioactive minerals was first proposed by G.C. Ridland, a geophysicist working at Port Radium in 1943. In 1947, the earliest recorded trial of airborne radiation detectors (ionization chambers and Geiger counters) was conducted by Eldorado Mining and Refining Limited. (a Canadian Crown Corporation since sold to become Cameco Corporation). The first patent for a portable gamma-ray spectrometer was filed by Professors Pringle, Roulston & Brownell of the University of Manitoba.

Airborne gamma-ray spectrometry is now the accepted leading technique for uranium prospecting with worldwide applications for geological mapping, mineral exploration & environmental monitoring. Airborne gamma-ray spectrometry used specifically for uranium measurement and prospecting must account for a number of factors like the distance between the source and the detector and the scattering of radiation through the minerals, surrounding earth and even in the air. In Australia, a Weathering Intensity Index has been developed to help prospectors based on the Shuttle Radar Topography Mission (SRTM) elevation and airborne gamma-ray spectrometry images.

A deposit of uranium, discovered by geophysical techniques, is evaluated and sampled to determine the amounts of uranium materials that are extractable at specified costs from the deposit. Uranium reserves are the amounts of ore that are estimated to be recoverable at stated costs. As prices rise or technology allows for lower cost of recovery of known, previously uneconomic, deposits, reserves increase. For uranium this effect is particularly pronounced as the biggest currently uneconomic reserve – uranium extraction from seawater – is bigger than all known land based resources of uranium combined.

Mining techniques

As with other types of hard rock mining there are several methods of extraction. In 2016, the percentage of the mined uranium produced by each mining method was: in-situ leach (49.7 percent), underground mining (30.8 percent), open pit (12.9 percent), heap leaching (0.4 percent), co-product/by-product (6.1%). The remaining 0,1% was derived as miscellaneous recovery.

Open pit

In open pit mining, overburden is removed by drilling and blasting to expose the ore body, which is then mined by blasting and excavation using loaders and dump trucks. Workers spend much time in enclosed cabins thus limiting exposure to radiation. Water is extensively used to suppress airborne dust levels. Groundwater is an issue in all types of mining, but in open pit mining, the usual way of dealing with it - i.e. when the target mineral is found below the natural water table - is to lower the water table by pumping off the water. The ground may settle considerably when groundwater is removed and may again move unpredictably when groundwater is allowed to rise again after mining is concluded. Land reclamation after mining takes different routes, depending on the amount of material removed. Due to the high energy density of uranium, it is often sufficient to fill in the former mine with the overburden, but in case of a mass deficit exceeding the height difference between the previous surface level and the natural water table, artificial lakes develop when groundwater removal ceases. If sulfites, sulfides or sulfates are present in the now-exposed rocks acid mine drainage can be a concern for those newly developing bodies of water. Mining companies are now required by law to establish a fund for future reclamation while mining is ongoing and those funds are usually deposited in such a way as to be unaffected by bankruptcy of the mining company.

Underground

If the uranium is too far below the surface for open pit mining, an underground mine might be used with tunnels and shafts dug to access and remove uranium ore.

Underground uranium mining is in principle no different from any other hard rock mining and other ores are often mined in association (e.g., copper, gold, silver). Once the ore body has been identified a shaft is sunk in the vicinity of the ore veins, and crosscuts are driven horizontally to the veins at various levels, usually every 100 to 150 metres. Similar tunnels, known as drifts, are driven along the ore veins from the crosscut. To extract the ore, the next step is to drive tunnels, known as raises when driven upwards and winzes when driven downwards, through the deposit from level to level. Raises are subsequently used to develop the stopes where the ore is mined from the veins.

The stope, which is the workshop of the mine, is the excavation from which the ore is extracted. Three methods of stope mining are commonly used. In the "cut and fill" or "open stoping" method, the space remaining following removal of ore after blasting is filled with waste rock and cement. In the "shrinkage" method, only sufficient broken ore is removed via the chutes below to allow miners working from the top of the pile to drill and blast the next layer to be broken off, eventually leaving a large hole. The method known as "room and pillar" is used for thinner, flatter ore bodies. In this method the ore body is first divided into blocks by intersecting drives, removing ore while so doing, and then systematically removing the blocks, leaving enough ore for roof support.

The health effects discovered from radon exposure in unventilated uranium mining prompted the switch away from uranium mining via tunnel mining towards open cut and in-situ leaching technology, a method of extraction that does not produce the same occupational hazards, or mine tailings, as conventional mining.

With regulations in place to ensure the use of high volume ventilation technology if any confined space uranium mining is occurring, occupational exposure and mining deaths can be largely eliminated. The Olympic Dam and Canadian underground mines are ventilated with powerful fans with radon levels being kept at a very low to practically "safe level" in uranium mines. Naturally occurring radon in other, non-uranium mines, also may need control by ventilation.

Heap leaching

Heap leaching is an extraction process by which chemicals (usually sulfuric acid) are used to extract the economic element from ore which has been mined and placed in piles on the surface. Heap leaching is generally economically feasible only for oxide ore deposits. Oxidation of sulfide deposits occurs during the geological process called weathering. Therefore, oxide ore deposits are typically found close to the surface. If there are no other economic elements within the ore a mine might choose to extract the uranium using a leaching agent, usually a low molar sulfuric acid.

If the economic and geological conditions are right, the mining company will level large areas of land with a small gradient, layering it with thick plastic (usually HDPE or LLDPE), sometimes with clay, silt or sand beneath the plastic liner. The extracted ore will typically be run through a crusher and placed in heaps atop the plastic. The leaching agent will then be sprayed on the ore for 30–90 days. As the leaching agent filters through the heap, the uranium will break its bonds with the oxide rock and enter the solution. The solution will then filter along the gradient into collecting pools which will then be pumped to on-site plants for further processing. Only some of the uranium (commonly about 70%) is actually extracted.

The uranium concentrations within the solution are very important for the efficient separation of pure uranium from the acid. As different heaps will yield different concentrations, the solution is pumped to a mixing plant that is carefully monitored. The properly balanced solution is then pumped into a processing plant where the uranium is separated from the sulfuric acid.

Heap leach is significantly cheaper than traditional milling processes. The low costs allow for lower grade ore to be economically feasible (given that it is the right type of ore body). US environmental law requires that the surrounding ground water is continually monitored for possible contamination. The mine will also have to have continued monitoring even after the shutdown of the mine. In the past mining companies would sometimes go bankrupt, leaving the responsibility of mine reclamation to the public. 21st century additions to US mining law require that companies set aside the money for reclamation before the beginning of the project. The money will be held by the public to insure adherence to environmental standards if the company were to ever go bankrupt.

''In-situ'' leaching

In-situ leaching (ISL), also known as solution mining, or in-situ recovery (ISR) in North America, involves leaving the ore where it is in the ground, and recovering the minerals from it by dissolving them and pumping the pregnant solution to the surface where the minerals can be recovered. Consequently, there is little surface disturbance and no tailings or waste rock generated. However, the orebody needs to be permeable to the liquids used, and located so that they do not contaminate ground water away from the orebody.

Uranium ISL uses the native groundwater in the orebody which is fortified with a complexing agent and in most cases an oxidant. It is then pumped through the underground orebody to recover the minerals in it by leaching. Once the pregnant solution is returned to the surface, the uranium is recovered in much the same way as in any other uranium plant (mill).

In Australian ISL mines (Beverley, Four Mile and Honeymoon Mine) the oxidant used is hydrogen peroxide and the complexing agent sulfuric acid. Kazakh ISL mines generally do not employ an oxidant but use much higher acid concentrations in the circulating solutions. ISL mines in the USA use an alkali leach due to the presence of significant quantities of acid-consuming minerals such as gypsum and limestone in the host aquifers. Any more than a few percent carbonate minerals means that alkali leach must be used in preference to the more efficient acid leach.

The Australian government has published a best practice guide for in situ leach mining of uranium, which is being revised to take account of international differences.

Seawater recovery

The uranium concentration in sea water is low, approximately 3.3 parts per billion or 3.3 micrograms per liter of seawater. But the quantity of this resource is gigantic and some scientists believe this resource is practically limitless with respect to world-wide demand. That is to say, if even a portion of the uranium in seawater could be used the entire world's nuclear power generation fuel could be provided over a long time period. Some anti-nuclear proponents claim this statistic is exaggerated. Although research and development for recovery of this low-concentration element by inorganic adsorbents such as titanium oxide compounds has occurred since the 1960s in the United Kingdom, France, Germany, and Japan, this research was halted due to low recovery efficiency.

At the Takasaki Radiation Chemistry Research Establishment of the Japan Atomic Energy Research Institute (JAERI Takasaki Research Establishment), research and development has continued culminating in the production of adsorbent by irradiation of polymer fiber. Adsorbents have been synthesized that have a functional group (amidoxime group) that selectively adsorbs heavy metals, and the performance of such adsorbents has been improved. Uranium adsorption capacity of the polymer fiber adsorbent is high, approximately tenfold greater in comparison to the conventional titanium oxide adsorbent.

One method of extracting uranium from seawater is using a uranium-specific nonwoven fabric as an adsorbent. The total amount of uranium recovered from three collection boxes containing 350 kg of fabric was >1 kg of yellowcake after 240 days of submersion in the ocean. The experiment by Seko ''et al.'' was repeated by Tamada et al. in 2006. They found that the cost varied from ¥15,000 to ¥88,000 depending on assumptions and "The lowest cost attainable now is ¥25,000 with 4g-U/kg-adsorbent used in the sea area of Okinawa, with 18 repetitionuses." With the May, 2008 exchange rate, this was about $240/kg-U.

In 2012, ORNL researchers announced the successful development of a new adsorbent material dubbed "HiCap", which vastly outperforms previous best adsorbents, which perform surface retention of solid or gas molecules, atoms or ions. "We have shown that our adsorbents can extract five to seven times more uranium at uptake rates seven times faster than the world's best adsorbents," said Chris Janke, one of the inventors and a member of ORNL's Materials Science and Technology Division. HiCap also effectively removes toxic metals from water, according to results verified by researchers at Pacific Northwest National Laboratory.

In 2012 it was estimated that this fuel source could be extracted at 10 times the current price of uranium.
In 2014, with the advances made in the efficiency of seawater uranium extraction, it was suggested that it would be economically competitive to produce fuel for light water reactors from seawater if the process was implemented at large scale. Uranium extracted on an industrial scale from seawater would constantly be replenished by both river erosion of rocks and the natural process of uranium dissolved from the surface area of the ocean floor, both of which maintain the solubility equilibria of seawater concentration at a stable level. Some commentators have argued that this strengthens the case for nuclear power to be considered a renewable energy.

Co-product/by-product

Uranium can be recovered as a by-product along with other co-products such as molybdenum, vanadium, nickel, zinc and petroleum products. Uranium is also often found in phosphate minerals, where it has to be removed because phosphate is mostly used for fertilizers. Phosphogypsum is a waste product from phosphate mining that can contain significant amounts of uranium and radium. Coal fly ash also contains significant amounts of uranium and has been suggested as a source for uranium extraction.

Resources

Uranium occurs naturally in many rocks, and even in seawater. However, like other metals, it is seldom sufficiently concentrated to be economically recoverable.
Like any resource, uranium cannot be mined at any desired concentration. No matter the technology, at some point it is too costly to mine lower grade ores.
Mining companies usually consider concentrations greater than 0.075% (750 ppm) as ore, or rock economical to mine at current uranium market prices.
There is around 40 trillion tons of uranium in Earth's crust, but most is distributed at low parts per million trace concentration over its mass.American Geophysical Union, Fall Meeting 2007, abstract #V33A-1161
Mass and Composition of the Continental Crust
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Estimates of the amount concentrated into ores affordable to extract for under $130 per kg can be less than a millionth of that total.

Uranium-235, the fissile isotope of uranium used in nuclear reactors, makes up about 0.7% of uranium from ore. It is the only naturally occurring isotope capable of directly generating nuclear power.
While Uranium-235 can be "bred" from , a natural decay product of present at 55 ppm in all natural uranium samples, Uranium-235 is ultimately a finite non-renewable resource.
Due to the currently low price of uranium, the majority of commercial light water reactors operate on a "once through fuel cycle" which leaves virtually all the energy contained in the original - which makes up over 99% of natural uranium - unused. Nuclear reprocessing can recover part of that energy by producing MOX fuel or Remix Fuel for use in conventional power generating light water reactors. This technology is currently used at industrial scale in France, Russia and Japan. However, at current uranium prices, this is widely deemed uneconomical if only the "input" side is considered.

Breeder reactor technology could allow the current reserves of uranium to provide power for humanity for billions of years, thus making nuclear power a sustainable energy.

Reserves

Reserves are the most readily available resources.
About 96% of the global uranium reserves are found in these ten countries: Australia, Canada, Kazakhstan, South Africa, Brazil, Namibia, Uzbekistan, the United States, Niger, and Russia.

The known uranium resources represent a higher level of assured resources than is normal for most minerals. Further exploration and higher prices will certainly, on the basis of present geological knowledge, yield further resources as present ones are used up. There was very little uranium exploration between 1985 and 2005, so the significant increase in exploration effort that we are now seeing could readily double the known economic resources. On the basis of analogies with other metal minerals, a doubling of price from price levels in 2007 could be expected to create about a tenfold increase in measured resources, over time.

Known conventional resources

Known conventional resources are resources that are known to exist and easy to mine.
In 2006, there were about 4 million tons of conventional resources.
In 2011, this increased to 7 million tonnes.
Exploration for uranium has increased: from 1981 to 2007, annual exploration expenditures grew modestly, from US$4 million to US$7 million. This increased to US$11 million in 2011.

The world's largest deposits of uranium are found in three countries.
Australia has just over 30% of the world's reasonably assured resources and inferred resources of uranium – about .
Kazakhstan has about 12% of the world's reserves, or about .
Canada has of uranium, representing about 9%.

Undiscovered conventional resources

Undiscovered conventional resources are resources that are thought to exist but have not been mined.
It will take a significant exploration and development effort to locate the remaining deposits and begin mining them. However, since the entire earth's geography has not been explored for uranium at this time, there is still the potential to discover exploitable resources.
The OECD Redbook cites areas still open to exploration throughout the world. Many countries are conducting complete aeromagnetic gradiometer radiometric surveys to get an estimate the size of their undiscovered mineral resources. Combined with a gamma-ray survey, these methods can locate undiscovered uranium and thorium deposits.
The U.S. Department of Energy conducted the first and only national uranium assessment in 1980 – the National Uranium Resource Evaluation (NURE) program.

Secondary resources

Secondary resources are essentially recovered uranium from other sources such as nuclear weapons, inventories, reprocessing and re-enrichment. Since secondary resources have exceedingly low discovery costs and very low production costs, they may have displaced a significant portion of primary production. Secondary uranium was and is available essentially instantly. However, new primary production will not be. Essentially, secondary supply is a "one-time" finite supply, with the exception of the re-processed fuel.
In 2017, about 7% of uranium demand was met from secondary resources.

Due to reduction in nuclear weapons stockpiles, a large amount of former weapons uranium was released for use in civilian nuclear reactors. As a result, starting in 1990, a significant portion of uranium nuclear power requirements were supplied by former weapons uranium, rather than newly mined uranium. In 2002, mined uranium supplied only 54 percent of nuclear power requirements. But as the supply of former weapons uranium has been used up, mining has increased, so that in 2012, mining provided 95 percent of reactor requirements, and the OCED Nuclear Energy Agency and the International Atomic Energy Agency projected that the gap in supply would be completely erased in 2013.

Inventories

Inventories are kept by a variety of organizations – government, commercial and others.

The US DOE keeps inventories for security of supply in order to cover for emergencies where uranium is not available at any price.

Decommissioning nuclear weapons

Both the US and Russia have committed to recycle their nuclear weapons into fuel for electricity production. This program is known as the Megatons to Megawatts Program.
Down blending of Russian weapons high enriched uranium (HEU) will result in about of low enriched uranium (LEU) over 20 years. This is equivalent to about of natural U, or just over twice annual world demand. Since 2000, of military HEU is displacing about of uranium oxide mine production per year which represents some 13% of world reactor requirements.
The Megatons to Megawatts program came to an end in 2013.

Plutonium recovered from nuclear weapons or other sources can be blended with uranium fuel to produce a mixed-oxide fuel. In June 2000, the US and Russia agreed to dispose of each of weapons-grade plutonium by 2014. The US undertook to pursue a self-funded dual track program (immobilization and MOX). The G-7 nations provided US$1 billion to set up Russia's program. The latter was initially MOX specifically designed for VVER reactors, the Russian version of the Pressurized Water Reactor (PWR), the high cost being because this was not part of Russia's fuel cycle policy. This MOX fuel for both countries is equivalent to about of natural uranium.
The U.S. also has commitments to dispose of of non-waste HEU.

Reprocessing and recycling

Nuclear reprocessing (or recycling) can increase the supply of uranium by separating the uranium from spent nuclear fuel.
Spent nuclear fuel is primarily composed of uranium, with a typical concentration of around 96% by mass.
The composition of reprocessed uranium depends on the time the fuel has been in the reactor, but it is mostly uranium-238, with about 1% uranium-235, 1% uranium-236 and smaller amounts of other isotopes including uranium-232.

Currently, there are eleven reprocessing plants in the world. Of these, two are large-scale commercially operated plants for the reprocessing of spent fuel elements from light water reactors with throughputs of more than of uranium per year. These are La Hague, France with a capacity of per year and Sellafield, England at uranium per year.
The rest are small experimental plants.
The two large-scale commercial reprocessing plants together can reprocess 2,800 tonnes of uranium waste annually.
The United States had reprocessing plants in the past but banned reprocessing in the late 1970s due to the high costs and the risk of nuclear proliferation via plutonium.

The main problems with uranium reprocessing are the cost of mined uranium compared to the cost of reprocessing,
At present, reprocessing and the use of plutonium as reactor fuel is far more expensive than using uranium fuel and disposing of the spent fuel directly – even if the fuel is only reprocessed once.
Reprocessing is most useful as part of a nuclear fuel cycle using fast-neutron reactors since reprocessed uranium and reactor-grade plutonium both have isotopic compositions not optimal for use in today's thermal-neutron reactors.

Unconventional resources

Unconventional resources are occurrences that require novel technologies for their exploitation and/or use. Often unconventional resources occur in low-concentration. The exploitation of unconventional uranium requires additional research and development efforts for which there is no imminent economic need, given the large conventional resource base and the option of reprocessing spent fuel.
Phosphates, seawater, uraniferous coal ash, and some type of oil shales are examples of unconventional uranium resources.

Phosphates

Uranium occurs at concentrations of 50 to 200 parts per million (ppm) in phosphate-laden earth or phosphate rock. As uranium prices increase, there has been interest in extraction of uranium from phosphate rock, which is normally used as the basis of phosphate fertilizers.
There are 22 million tons of uranium in phosphate deposits. Recovery of uranium from phosphates is a mature technology; it has been utilized in Belgium and the United States, but high recovery costs limit the utilization of these resources, with estimated production costs in the range of US$60–100/kgU including capital investment, according to a 2003 OECD report for a new 100 tU/year project.
Historical operating costs for the uranium recovery from phosphoric acid range from $48–$119/kg U₃O₈.
In 2011, the average price paid for U₃O₈ in the United States was $122.66/kg.

Worldwide, approximately 400 wet-process phosphoric acid plants were in operation. Assuming an average recoverable content of 100 ppm of uranium, and that uranium prices do not increase so that the main use of the phosphates are for fertilizers, this scenario would result in a maximum theoretical annual output of U₃O₈.

Seawater

Unconventional uranium resources include up to of uranium contained in sea water. Several technologies to extract uranium from sea water have been demonstrated at the laboratory scale.
According to the OECD, uranium may be extracted from seawater for about US$300/kgU.

In 2012, ORNL researchers announced the successful development of a new absorbent material dubbed HiCap, which vastly outperforms previous best adsorbents, which perform surface retention of solid or gas molecules, atoms or ions. "We have shown that our adsorbents can extract five to seven times more uranium at uptake rates seven times faster than the world's best adsorbents", said Chris Janke, one of the inventors and a member of ORNL's Materials Science and Technology Division. HiCap also effectively removes toxic metals from water, according to results verified by researchers at Pacific Northwest National Laboratory.

Uraniferous coal ash

According to a study by Oak Ridge National Laboratory, the theoretical maximum energy potential (when used in breeder reactors) of trace uranium and thorium in coal actually exceeds the energy released by burning the coal itself. This is despite very low concentration of uranium in coal of only several parts per million average before combustion.

From 1965 to 1967 Union Carbide operated a mill in North Dakota, United States, burning uraniferous lignite and extracting uranium from the ash. The plant produced about 150 metric tons of U₃O₈ before shutting down.

An international consortium has set out to explore the commercial extraction of uranium from uraniferous coal ash from coal power stations located in Yunnan province, China. The first laboratory scale amount of yellowcake uranium recovered from uraniferous coal ash was announced in 2007. The three coal power stations at Xiaolongtang, Dalongtang and Kaiyuan have piled up their waste ash. Initial tests from the Xiaolongtang ash pile indicate that the material contains (160–180 parts per million uranium), suggesting a total of U₃O₈ could be recovered from that ash pile alone.

Oil shales

Some oil shales contain uranium, which may be recovered as a byproduct. Between 1946 and 1952, a marine type of Dictyonema shale was used for uranium production in Sillamäe, Estonia, and between 1950 and 1989 alum shale was used in Sweden for the same purpose.

Breeding

A breeder reactor produces more nuclear fuel than it consumes and thus can extend the uranium supply. It typically turns the dominant isotope in natural uranium, uranium-238, into fissile plutonium-239. This results in hundredfold increase in the amount of energy to be produced per mass unit of uranium, because U-238, which constitute 99.3% of natural uranium, is not used in conventional reactors which instead use U-235 which only represent 0.7% of natural uranium. In 1983, physicist Bernard Cohen proposed that the world supply of uranium is effectively inexhaustible, and could therefore be considered a form of renewable energy.
He claims that fast breeder reactors, fueled by naturally-replenished uranium-238 extracted from seawater, could supply energy at least as long as the sun's expected remaining lifespan of five billion years.

There are two types of breeders: Fast breeders and thermal breeders.
Efforts at commercializing breeder reactors have been largely unsuccessful, due to higher costs and complexity compared to LWR, as well as political opposition.
A few commercial breeder reactors exists. In 2016, the Russian BN-800 fast-neutron breeder reactor started producing commercially at full power (800 MWe), joining the previous BN-600. , the Chinese CFR-600 is under construction after the success of the China Experimental Fast Reactor, based on the BN-800. These reactors are currently generating mostly electricity rather than new fuel because the abundance and low price of mined and reprocessed uranium oxide makes breeding uneconomical, but they can switch to breed new fuel and close the cycle as needed.
The CANDU reactor, which was designed to be fueled with natural uranium, is capable of using spent fuel from Light Water Reactors as fuel, since it contains more fissile material than natural uranium. Research into "DUPIC" - direct use of PWR spent fuel in CANDU type reactors - is ongoing and could increase the usability of fuel without the need for reprocessing.

Fast breeder

A fast breeder, in addition to consuming U-235, converts fertile U-238 into Pu-239, a fissile fuel. Fast breeder reactors are more expensive to build and operate, including the reprocessing, and could only be justified economically if uranium prices were to rise to pre-1980 values in real terms. In addition to considerably extending the exploitable fuel supply, these reactors have an advantage in that they produce less long-lived transuranic wastes, and can consume nuclear waste from current light water reactors, generating energy in the process.

Uranium turned out to be far more plentiful than anticipated, and the price of uranium declined rapidly (with an upward blip in the 1970s). This is why the United States halted their use in 1977, and the UK abandoned the idea in 1994.
Significant technical and materials problems were encountered with FBRs, and geological exploration showed that scarcity of uranium was not going to be a concern for some time. By the 1980s, due to both factors, it was clear that FBRs would not be commercially competitive with existing light water reactors. The economics of FBRs still depend on the value of the plutonium fuel which is bred, relative to the cost of fresh uranium.

At higher uranium prices breeder reactors may be economically justified. Many nations have ongoing breeder research programs. China, India, and Japan plan large scale utilization of breeder reactors during the coming decades. 300 reactor-years experience has been gained in operating them.

Thermal breeder

Fissile uranium can be produced from thorium in thermal breeder reactors. Thorium is three times more plentiful than uranium. Thorium-232 is in itself not fissile, but it can be made into fissile uranium-233 in a breeder reactor. In turn, the uranium-233 can be fissioned, with the advantage that smaller amounts of transuranics are produced by neutron capture, compared to uranium-235 and especially compared to plutonium-239.

Despite the thorium fuel cycle having a number of attractive features, development on a large scale can run into difficulties, mainly due to the complexity of fuel separation and reprocessing.
Advocates for liquid core and molten salt reactors such as LFTR claim that these technologies negate the above-mentioned thorium's disadvantages present in solid-fueled reactors.

The first successful commercial reactor at the Indian Point Energy Center in Buchanan, New York (Indian Point Unit 1) ran on thorium. The first core did not live up to expectations.

Production

The world's top uranium producers are Kazakhstan (39% of world production), Canada (22%) and Australia (10%). Other major producers include Namibia (6.7%), Niger

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