About Uranium

Uranium is the chemical element with the symbol U and atomic number 92. A uranium atom has 92 protons, 92 electrons and between 141 and 146 neutrons, establishing six isotopes the most common of which are U238 (146neutrons) and U235 (143 neutrons). All isotopes are unstable and radioactive (slow decay by the emission of alpha particles). Uranium occurs naturally in low concentrations of a few parts per million in soils, rock and water and is commercially extracted from uranium bearing minerals such as uraninite.

The major primary ore mineral is uraninite (basically UO2) or pitchblende (U2O5.UO3, better known as U3O8), though a range of other uranium minerals is found in particular deposits. These include carnotite (uranium potassium vanadate), the davidite-brannerite-absite type uranium titanates, and the euxenite-fergusonite-samarskite group (niobates of uranium and rare earths). 

In nature uranium is found as U238 (99.2742%), U235 (0.7204%) and a very small amount of U234 (0.0054%) and is mined and processed to produce U3O8 (uranium oxide more commonly known as “yellow cake”). The U235 is the desired isotope in natural uranium and it varies by as much as 0.1% depending on the source. 0.711% has been adopted by the US DOE (USA Department of Energy) as the official percentage of U235 in natural uranium.

U235 has the distinction of being the only naturally occurring fissile isotope. The dominate interest in U235 is for military purposes (weapons) and nuclear power generation. It is able to release abundant concentrated energy. 

Production

According to the World Nuclear Association the world production of uranium in 2009 was 50,772 tonne (or 59,875 tonne of U3O8). It has been gradually rising since 1993. The forecast production for 2010 is estimated to have been about 55,000 tonne of U mainly due to increases in production in Kazakhstan and Namibia. Following is a break down of the 2009 production by country: 

• Kazakhstan: 14,020 tonne
• Canada: 10,173 tonne
• Australia: 7,982 tonne
• Namibia: 4,626tonne
• Russia: 3,564 tonne
• Niger: 3,243 tonne
• Uzbekistan: 2,249 tonne
• USA: 1,453 tonne
• Other: 3,462 tonne

The 2009 production was from conventional under ground and open pit mining (57%), in situ leach (ISL) 36% and by-product from Olympic Dam, Australia (7%). The biggest change has been in the in situ leach, due mainly to Kazakhstan.

Uranium is of great importance as a nuclear fuel and U235 is the key. To be used as a nuclear fuel natural uranium needs to be concentrated mainly by gaseous centrifuge (this is newer and more efficient technology) and gaseous diffusion processes from 0.71% U235 (as it occurs in natural uranium) to between 3.2% or 3.6% U235 and is then used directly as nuclear fuel. One kg of this fuel has the same fuel value as 3,300 tonne of coal.

Uses

U238 can be used to produce fissionable plutonium and this may also be used as a nuclear fuel. However because this process may be used to produce material for nuclear warheads this path is discouraged by the International Community and not used. All other uses for uranium are minor.

The enrichment of natural uranium (U3O8) into nuclear fuel is a significant component of the final cost. The process is very capital intensive and restricted to a limited number of countries. Accurate cost and actual recovery information is not available for political and commercial reasons. The efficiency of the enrichment process is measured by the amount of U235 in the tails (also referred to as waste stream or residue) and is recycling dependent (more efficient with more recycling but at a lower rate). 

The amount of U235 in the tails is typically about 0.3 % (starting from 0.711%). The amount of enrichment that is most economical is dependent on various factors, including the capacity and cost of the enrichment equipment and the current price of U3O8. This in turn will determine the amount of U3O8 required in the supply demand equation. For instance, higher U3O8 prices would lead to value in more enrichment therefore requiring less U3O8. Conversely with lower prices enrichments costs may be reduced by increasing enrichment through put at the expense of higher “tail assays”. In this instance more yellow cake (natural U3O8) would be required to produce the same amount of nuclear fuel.

Also reprocessing of stockpiles of old residue having high “tail assays” may become economical, especially with the installation of more efficient centrifuge enrichment equipment and the availability of spare capacity.

Down blending is the blending of weapons grade or highly enriched uranium (known as HEU, which has been built up since World War II and over the cold war period and is now surplus to requirements) with natural uranium to produce nuclear fuel. Most is from Russian and USA nuclear weapon stockpiles. Presently some of this is supplied by Russia under contract (due to expire in 2013) to the USA. This source presently provides the major difference between actual demand and supply from normal mining production.

Markets and Growth

The world’s power reactors, with combined capacity of some 375 GWe (Giga Watts estimated), require about 68,000 tonne of uranium from mines or elsewhere each year.  While this capacity is being run more productively, with higher capacity factors and reactor power levels, the uranium fuel requirement is increasing, but not necessarily at the same rate.  The factors increasing fuel demand are offset by a trend for higher burn-up of fuel and other efficiencies, so demand is steady (Over the years 1980 to 2008 the electricity generated by nuclear power increased 3.6-fold while uranium used increased by a factor of only 2.5).

Reducing the tails assay in enrichment reduces the amount of natural uranium required for a given amount of fuel.  Reprocessing of used fuel from conventional light water reactors also utilises present resources more efficiently, by a factor of about 1.3 overall.

Today's reactor fuel requirements are met from primary supply (direct mine output - 78% in 2009) and secondary sources: commercial stockpiles, nuclear weapons stockpiles, recycled plutonium and uranium from reprocessing used fuel, and some from re-enrichment of depleted uranium tails (left over from original enrichment).

As of January 2011 and according to the WNA (World Nuclear Association) the status of world nuclear capacity and generation was as follows:

Current position: 443 reactors for a capacity of approx. 375 GWe requiring approx. 68,000 tonne of U (or 178,000,000 lbs of U3O8) per annum.

Under construction (commissioned over the next 5 years): 62 reactors for a capacity of approx. 64.6 GWe requiring another 8,300 tonne of U per annum based on improved fuel and efficiency utilization of 30%.  

Planned (as much as 20 years before possible commissioning): 156 reactors for a capacity of approx. 175 GWe requiring another 22,000 tonne of U per annum, also based on improved fuel and efficiency utilization of 30%.

WNA reference scenario projects world demand for uranium in 2015 will be about 77,000 tonne of U per annum and that this will need to come directly from mines.

Useful Links

Australian Uranium Association (http://www.aua.org.au); International Atomic Energy Agency (http://www.iaea.or.at); Nuclear Energy Institute (http://www.nei.org); Uranium Information Centre (http://www.uic.com.au); Canadian Nuclear Association (http://www.cna.ca); Cameco Corporation (http://www.cameco.com); Paladin Energy (http://www.paladinenergy.com.au); Areva (http://www.areva.com); Kazatomprom (http://www.kazatomprom.kz).