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These deposits are usually low to medium grade varying from 0.05 to 0.4% U3O8 . The main minerals are uraninite

and coffinite. In recent years, production from these low-grade deposits has been enhanced by ISL methods of

extraction

Intrusive breccia complex deposits

These deposits occur in brecciated settings believed to have formed in near surface sub-volcanic environments, with

tectonic faulting, fracturing and gravity collapse causing brecciation. The mineralization occurs on the flanks of

localized diatreme structures with large zones of hydrothermal alteration with hematite-rich breccias hosting the

copper-uranium mineralization. . Uranium and base metal mineralization occurs mainly as disseminated and fracture

controlled zones spatially associated with intense alteration and tectonism.

PaleoplacerQuartz-pebble conglomerate deposits

These deposits occur in Archean-Paleaoproterozoic . Uranium and often associated gold in these deposits, occurs in

coarse grained sediments within paleochannels along the base of Proterozoic sedimentary basins. Grades in these

deposits can vary from 0.01% U3O8 to as much as 0.15%,

HOW IS URANIUM EXTRACTED AND PROCESSED?

Uranium ore is mined in several ways, depending on the geological conditions: by open pit,

underground, in-situ leaching, and borehole mining.Uranium ore is crushed and rendered into a fine

powder and then leached with either an acid or alkali. The leachate is subjected to one of several

sequences of precipitation, solvent extraction, and ion exchange. The resulting enriched mixture, called

yellowcake, contains at least 75 percent uranium oxides. Yellowcake is then calcined to remove

impurities from the milling process before refining and conversion.

Uranium ore can be mined by underground or open-cut methods, depending on the depth of the mineralization and

grade. After mining, the ore is crushed and ground, and the oxide ore is treated with sulphuric acid to produce

uranium oxide or yellowcake. In the case of the extremely high-grade ores in the Athabasca basin at McArthur River,

mining is carried out using remote control underground mining methods, followed by processing underground where

the ore is thickened and pumped as slurry to the surface. It is then placed into special containers for transportation to

the mill at Key Lake.

In some circumstances, especially for lower-grade ores, the uranium may be mined by ISL, where uranium is

dissolved from the orebody in place. The uranium is extracted through a system of wells drilled into the orebody and

into which solution is injected to strip the uranium from the host rock and is then transported to the surface in solution.A production well then transfers the uranium-bearing solution to a processing plant where the uranium is recovered.

ISL technology was developed nearly 25 years ago and features safe operations and minimal environmental impact,

with low capital and operating costs. ISL mining accounted for approximately 16% of the worlds uranium produc tion

in 2002. The end product of the mining and milling stages, or of ISL, is uranium oxide concentrate (U3O8). This is the

form in which uranium is sold.

HOW IS URANIUM COVERTED TO USEABLE FUEL?

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Airborne gamma-ray spectrometry is now the accepted leading technique for uraniumprospecting with worldwide applications for geological mapping, mineral exploration &environmental monitoring.

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 thedeposit. Uranium reserves are the amounts of ore that are estimated to be recoverable at statedcosts.

[edit] Mining techniques

As with other types ofhard rock miningthere are several methods of extraction. The mainmethods of mining arebox cutmining,open pitmining andIn-situ leaching(ISL).

[edit]Open pit

Rssingopen pit uranium mine, Namibia

In open pit mining,overburdenis removed by drilling and blasting to expose the ore body, whichis then mined by blasting and excavation using loaders and dump trucks. Workers spend muchtime in enclosed cabins thus limiting exposure to radiation. Water is extensively used to suppressairborne dust levels.

[edit]Underground uranium mining

If the uranium is too far below the surface for open pit mining, an underground mine might beused with tunnels and shafts dug to access and remove uranium ore. There is less waste materialremoved from underground mines than open pit mines, however this type of mining exposesunderground workers to the highest levels of radon gas.

Underground uranium mining is in principle no different to any otherhard rock miningand otherores are often mined in association (e.g., copper, gold, silver). Once the ore body has beenidentified a shaft is sunk in the vicinity of the ore veins, and crosscuts are driven horizontally tothe veins at various levels, usually every 100 to 150 metres. Similar tunnels, known as drifts, aredriven 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

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from level to level. Raises are subsequently used to develop the stopes where the ore is minedfrom the veins.

The stope, which is the workshop of the mine, is the excavation from which the ore is extracted.Two 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 allowminers working from the top of the pile to drill and blast the next layer to be broken off,eventually leaving a large hole. Another 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 orefor roof support.

[edit]Heap leaching

Heap leachingis an extraction process by which chemicals (usuallysulfuric 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 only economically feasible only for oxide ore deposits. Oxidation ofsulfide deposits occur during the geological process called weatherization. Therefore oxide oredeposits are typically found close to the surface. If there are no other economic elements withinthe ore a mine might choose to extract the uranium using a leaching agent, usually a low molarsulfuric acid.

If the economic and geological conditions are right, the mining company will level large areas ofland with a small gradient, layering it with thick plastic (usuallyHDPEorLLDPE), sometimeswith clay, silt or sand beneath the plastic liner. The extracted ore will typically be run through acrusher 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 bondswith the oxide rock and enter the solution. The solution will then filter along the gradient intocollecting pools which will then be pumped to on-site plants for further processing. Only some ofthe uranium (commonly about 70%) is actually extracted.

The uranium concentrations within the solution are very important for the efficient separation ofpure uranium from the acid. As different heaps will yield different concentrations the solution ispumped to a mixing plant that is carefully monitored. The properly balanced solution is thenpumped 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).Environmental law requires that the surrounding ground water is continually monitored forpossible contamination. The mine will also have to have continued monitoring even after theshutdown of the mine. In the past mining companies would sometimes go bankrupt, leaving theresponsibility of mine reclamation to the public. Recent additions to the mining law require thatcompanies set aside the money for reclamation before the beginning of the project. The moneywill be held by the public to insure adherence to environmental standards if the company were toever go bankrupt.

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Another very similar mining technique is called in situ, or in place mining where the ore doesn'teven need extracting.

[edit]I n-situleaching

Trial well field for in-situ recovery at Honeymoon, South Australia

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

Uranium ISL uses the native groundwater in the orebody which is fortified with a complexingagent and in most cases an oxidant. It is then pumped through the underground orebody torecover 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 (Beverleyand the soon to be openedHoneymoon Mine)the oxidantused is hydrogen peroxide and the complexing agent sulfuric acid. Kazakh ISL mines generallydo 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 fewpercent carbonate minerals means that alkali leach must be used in preference to the moreefficient 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.

[5]

[edit]Recovery from seawater

The uranium concentration of sea water is low, approximately 3.3 mg percubic meterofseawater. But the quantity of this resource is gigantic and some scientists believe this resource ispractically limitless with respect to world-wide demand. That is to say, if even a portion of theuranium in seawater could be used the entire world's nuclear power generation fuel could be

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provided over a long time period.[6]Some anti-nuclear proponents[7]claim this statistic isexaggerated. Although research and development for recovery of this low-concentration elementby inorganic adsorbents such astitanium oxidecompounds has occurred since the 1960s in theUnited Kingdom, France, Germany, and Japan, this research was halted due to low recoveryefficiency.

At the Takasaki Radiation Chemistry Research Establishment of the Japan Atomic EnergyResearch Institute (JAERI Takasaki Research Establishment), research and development hascontinued culminating in the production of adsorbent by irradiation of polymer fiber. Adsorbentshave been synthesized that have a functional group (amidoxime group)that selectively adsorbsheavy metals, and the performance of such adsorbents has been improved. Uranium adsorptioncapacity of thepolymer fiber adsorbentis high, approximately tenfold greater in comparison tothe conventional titanium oxide adsorbent.

One method of extracting uranium from seawater is using a uranium-specific nonwoven fabric asan absorbent. The total amount of uranium recovered from three collection boxes containing 350

kg of fabric was >1 kg ofyellowcakeafter 240 days of submersion in the ocean.

[8]

According tothe OECD, uranium may be extracted from seawater using this method for about $300/kg-U.[9]The experiment by Seko et al.was repeated by Tamada et al. in 2006. They found that the costvaried from 15,000 to 88,000 (Yen) depending on assumptions and "The lowest cost attainablenow is 25,000 with 4g-U/kg-adsorbent used in the sea area of Okinawa, with 18 repetitionuses[sic]." With the May, 2008 exchange rate, this was about $240/kg-U.[10]

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