Nuclear Fuel Cycle - Mining and Milling
Sources of Radiation Nuclear Fuel Cycle - Mining and Milling Day 4 Lecture 5 (2) Mining Mining is the first step in the process of providing the natural uranium feed material for use as a fuel. Mining Techniques Excavation Open Pit Underground Mines
In Situ Leaching Both excavation and in situ techniques are used to recover uranium. Excavation may be underground or open pit mining. Open Pit (Surface) Mining
In general, open pit mining is used where deposits are close to the surface.Open pit mines require large holes on the surface, larger than the size of the ore deposit, since the walls of the pit must be sloped to prevent collapse. As a result, the quantity of material that must be removed in order to access the ore may be large. Underground Mines underground mining is used for deep deposits, typically greater than 120 m deep. Underground mines have relatively small surface disturbance and the quantity of material that must be removed to access the ore is considerably less than in the case of an open pit mine. In the case of underground uranium mines, special precautions, consisting primarily of increased ventilation, are required to protect against airborne radiation exposure. Typically greater than 120 m deep .. Ventilation issues Uranium Ore Uranium ore sand
The appearance of uranium ore differs depending on its origin. Uranium ore sand In Situ Leach Production Facility Injection Well Head
An increasing proportion of the worlds uranium now comes from in situ leaching (ISL), where oxygenated groundwater is circulated through a very porous orebody to dissolve the uranium and bring it to the surface. ISL may be conducted with slightly acid or with alkaline solutions to keep the uranium in solution. The uranium is then recovered from the solution as in a conventional mill. Injection Well Field in situ leaching (ISL), where oxygenated groundwater is circulated through a very porous ore body to dissolve the uranium and bring it to the surface Uranium Mining Methods
Method World Production (%) Underground28 Open Pit20 In Situ Leach (ISL)45 By-Product7 Total100 The decision as to which mining method to use for a particular deposit is governed by the nature of the orebody, safety and economic considerations. Source:World Nuclear Association (WNA) percentage of world demand*
Uranium Mine Production Country 2005 2006 2007 2008 2009 2010 2011 2012 Kazakhstan 4357 5279 6637 8521 14020 17803 19451 21317 Canada 11628 9862 9476 9000 10173 9783 9145 8999 Australia 9516 7593 8611 8430 7982 5900 5983 6991 Niger (est) 3093 3434 3153 3032 3243 4198 4351 4667 Namibia 3147 3067 2879 4366 4626 4496 3258 4495 Russia 3431 3262 3413 3521 3564 3562 2993 2872 Uzbekistan 2300 2260 2320 2338 2429 2400 2500 USA 1039 1672 1654 1430 1453 1660 1537 1596 China (est) 750 712 769 827 885 1500 Malawi 104 670 846 1101 Ukraine (est) 800 840 850 890 960 South Africa 674 534 539 655 563 583 582 465 India (est) 230 177 270 271 290 400 385 Brazil 110 190 299 330 345 148 265 231 Czech Republic 408 359 306 263 258 254 229 228 Romania (est) 90 77 75 Germany 94 65 41 8 51 50 Pakistan (est) 45 France 7 5 4 6 3 total world 41 719 39 444 41 282 43 764 50 772 53 671 53 493 58 394 tonnes U3O8 49 199 46 516 48 683 51 611 59 875 63 295 63 084 68 864 percentage of world demand* 65% 63% 64% 68% 78% 85% 86% Source:World Nuclear Association (WNA) The largest-producing uranium mines in 2011
Country Main owner Type Production (tU) % of world McArthur River Canada Cameco underground 7686 14 Olympic Dam Australia BHP Billiton by-product/ underground 3353 6 Arlit Niger Somair/ Areva open pit 2726 5 Tortkuduk Kazakhstan Katco JV/ Areva ISL 2608 Ranger ERA (Rio Tinto 68%) 2240 4 Kraznokamensk Russia ARMZ 2191 Budenovskoye 2 Karatau JV/Kazatomprom-Uranium One 2175 Rossing Namibia Rio Tinto (69%) 1822 3 Inkai Inkai JV/Cameco 1602 South Inkai Betpak Dala JV/ Uranium One 1548 Top 10 total 27,951 52% Source:World Nuclear Association (WNA) Milling Milling, which is generally carried out close to a uranium mine, extracts the uranium from the ore. Milling, which is generally carried out close to a uranium mine, extracts the uranium from the ore. Ore Processing At the mill the ore is crushed and ground to a fine slurry. The uranium is extracted from the crushed and groundup ore by leaching, in which either a strong acid or a strong alkaline solution is used to dissolve the uranium from the waste rock. Uranium is then recovered from solution and precipitated as uranium oxide (U308) concentrate sometimes known as "yellowcake" At the mill the ore is crushed and ground to a fine slurry.The uranium is extracted from the crushed and groundup ore by leaching, in which either a strong acid or a strong alkaline solution is used to dissolve the uranium from the waste rock. It is then recovered from solution and precipitated as uranium oxide (U308) concentrate sometimes known as "yellowcake" Ore Processing At the mill the ore is crushed and ground to a fine slurry.The uranium is extracted from the crushed and groundup ore by leaching, in which either a strong acid or a strong alkaline solution is used to dissolve the uranium from the waste rock. It is then recovered from solution and precipitated as uranium oxide (U308) concentrate sometimes known as "yellowcake" Yellowcake Yellowcake is shipped from the mills in a granular solid form . Themixture of uranium oxides that is not really yellow but almost black olive green. 'yellowcake' generally contains more than 80% uranium. The original ore may contains as little as 0.1% uranium. About 200 tonnes of U3O8 is required to keep a large (1000 MWe) nuclear power reactor generating electricity for one year. Yellowcake is really a mixture of uranium oxides that is not really yellow but almost black olive green and shipped from the mills in a granular solid form that varies in color from yellowish to an almost black olive green, depending on the mineral it was found in and the processing (most notably, the calcination temperature). 'yellowcake' generally contains more than 80% uranium. The original ore may contains as little as 0.1% uranium.After drying and usually heating it is packed in 200litre drums as a concentrate. About 200 tonnes of U3O8 is required to keep a large (1000 MWe) nuclear power reactor generating electricity for one year. Yellowcake Yellowcake is really a mixture of uranium oxides that is hardly ever yellow any more.It is shipped from the mills in a granular solid form that varies in color from yellowish to an almost black olive green, depending on the mineral it was found in and the processing (most notably, the calcination temperature). 'yellowcake' generally contains more than 80% uranium. The original ore may contains as little as 0.1% uranium.After drying and usually heating it is packed in 200litre drums as a concentrate. About 200 tonnes of U3O8 is required to keep a large (1000 MWe) nuclear power reactor generating electricity for one year. Uranium Mill Tailings The remainder of the ore, containing most of the radioactivity and nearly all the rock material, becomes tailings, which are emplaced in engineered facilities near the mine (often in a mined-out pit). Tailings contain longlived radioactive materials in low concentrations and toxic materials such as heavy metals; however, the total quantity of radioactive elements is less than in the original ore, and their collective radioactivity will be much shorterlived. These materials need to be isolated from the environment.Radon emanation from mill tailings is a major concern. For example, if mill tailings were to be used in the construction industry, elevated levels of radon emission would result in the structures built.A variation of this actually occurred in the US some time ago when residue from the phosphate industry was used to refill the excavation.Homes were constructed on top resulting in elevated radon levels. Radiological Hazards of U Milling
Ore dust and radon emissions from ore crushing, sorting, and storage Yellowcake dust from drying and packaging area Windblown particulates and radon emission from the tailings disposal area Reference World Nuclear Association (WNA)
Cycle/Mining-of-Uranium/World-Uranium-Mining-Production/ of-uranium/uranium-mining-overview/ International Atomic Energy Agency, Postgraduate Educational Course in Radiation Protection and the Safety of Radiation Sources (PGEC), Training Course Series 18, IAEA, Vienna (2002)