Chem230 Wiki
Advertisement

Uranium_-_Periodic_Table_of_Videos

Uranium - Periodic Table of Videos

Uranium is more plentiful than tin, cadmium, mercury, or silver, and it is about as abundant as arsenic or molybdenum.

Uranium: What is it?[]

Today, uranium is obtained from uranium ores such as [1]

· pitchblende (UO3·UO2·PbO)

Uranium Ore

· uraninite (UO2)

· carnotite (K2(UO2)2VO4·1-3H2O)

· autunite (Ca(UO2)2(PO4)2·10H2O)

· phosphate rock (Ca3(PO4)2)

· lignite (brown coal)

· monazite sand ((Ce, La, Th, Nd, Y)PO4)

· sodium diuranate (Na2U2O7·6H2O), also known as yellow cake, or triuranium octoxide (U3O8)

Uranium: Where is It?[]

Where.gif

Uranium can be found and is mined in the US, but it is mostly found and mined in Canada. However the most abundant source of Uranium comes from the ocean and the Earth’s crust.[2]


  • Estimated Crustal Abundance: 2.7 milligrams per kilogram

    Mining Table

  • Estimated Oceanic Abundance: 3.2×10-3 milligrams per liter


Production Table

The largest-producing uranium mines in 2011 were Canada, Australia and Niger. More information on this can be found in the Mining Table. The largest producers of Uranium were Kazakhstan, Canada, and Australia. More information on the producers past and current can be seen in the Production Table.



Uranium: How to Get it ?[]

Uranium resources can be extracted from the ground in three ways: open pit, underground, and in-situ leach (ISL).

Open Pit Mining[]

Open pit mining, also known as strip mining, is the removal of surficial soils and uneconomic rock to get at the ore below. Ore grades are normally less than 0.5%. This is type of mining is only possible if the uranium ore is near the surface (normally less than 400 ft). The Jackpile Mine on Laguna Pueblo was once the world's largest open pit uranium mine.

Image42.jpg

Underground Mining[]

Underground mining is used to get at higher concentrations of uranium that are too deep to get at from open-pit. The ore is drilled, then blasted to create debris which is then transported to the surface, then on to a mill.

Milling[]

For both traditional underground and open pit mining, the rocks may have only a few percent (normally <0.3%) uranium in them. The uranium then has to be removed from the rock and concentrated. The milling process involves crushing and pulverizing the rock into very fine fragments and adding water to create a slurry. This slurry is then mixed with sulfuric acid or an alkaline solution to release the uranium from the host rock. Normally approximately 95 - 98% of the uranium can be recovered from the host rock. From this acid or alkaline solution, uranium oxide or yellowcake is precipitated. This is still not the purest form, and the uranium has to be sent to another plant to enrich it. The remaining rock slurry is pumped to a tailings dam. These tailings are exposed to the surface and heavy metals can be released into the environment.[3]


Isolation_of_Uranium_Yellowcake_from_Ore-0

Isolation of Uranium Yellowcake from Ore-0

In-situ Recover (ISR) Mining (also known as In-situ Leach or ISL)[]

How_Is_Uranium_Mining_Conducted_in_the_United_States?-0

How Is Uranium Mining Conducted in the United States?-0

Why Do We Seek Out Uranium?[]

As many of us know, the primary use of uranium is for energy production. For energy production, the U-238 isotope found in nature is enriched in large gas diffusion plants to roughly 3% U-235, a more fissile form of uranium.

The nucleus of the U-235 atom comprises 92 protons and 143 neutrons (92 + 143 = 235). When the nucleus of a U-235 atom captures a moving neutron it splits in two (fissions) and releases some energy in the form of heat, also two or three additional neutrons are thrown off. If enough of these expelled neutrons cause the nuclei of other U-235 atoms to split, releasing further neutrons, a fission 'chain reaction' can be achieved. When this happens over and over again, many millions of times, a very large amount of heat is produced from a relatively small amount of uranium.[4]

Figure 1: Representation of Nuclear Fission


Representation of Nuclear Fission[5]


The heat generated from the nuclear fission is used to turn water into high-pressure steam, which is then used in a turbine to generate electricity. The diagram below shows a very simple model of a light water nuclear reactor, one of the most common types of reactors used in the industry today. Light water refers to the type of cooling water used: light water is regular water with the normal isotope of hydrogen, and heavy water with the deuterium isotope of hydrogen.

Figure 2: Common Light Water Nuclear Reactor

Figure 2: Common Light Water Nuclear Reactor[6]












Energy Conversion: Typical Heat Values of Various Fuels[7]

Firewood (dry)

16 MJ/kg

Brown coal (lignite)

10 MJ/kg

Black coal (low quality)

13-23 MJ/kg

Black coal (hard)

24-30 MJ/kg

Natural Gas

38 MJ/m3

Crude Oil

45-46 MJ/kg

Uranium - in typical reactor

500,000 MJ/kg (of natural U)


Why Use Uranium instead of Coal?[]

World resources of coal are, in theory, large enough to produce the electricity we shall need for more than a hundred years. However, it is likely that more and more of the coal mined in the future will be converted into the more valuable liquid fuels rather than being available for electricity generation. There are also environmental and other problems associated with the increased mining and burning of coal.[8]

Bhty.gif









Any means of producing electricity involves some wastes and environmental hazard. The nuclear industry is unique in that it is the only energy-producing industry that takes full responsibility for the management and disposal of all its wastes and meets the full cost of doing so. Nuclear energy today saves the emission of about 2.6 billion tonnes of carbon dioxide each year (compared with about 10 billion tonnes per year actually emitted from fossil fuel electricity generation).[9]

Other Uses of Uranium[]

Uranium is used as:[10]

  • armor on certain military tanks due to its high density.
  • as a high density penetrator tank ammunition.
  • as a shield for the radiation from even more radiative materials
  • in older-type nuclear fission bombs
  • as a glaze in pottery for its glowing properties
  • as an additive to glass so that it glows green under UV light
  • in radiometric dating of rocks

Vaselineuv.jpg










The global impact of new technologies, particularly to people groups.[]

Uranium plays a huge role in modern day's electricity. “Over 13% of the world's electricity is generated from uranium in nuclear reactors. This amounts to over 2500 billion kWh each year, as much as from all sources of electricity worldwide in 1960”.[11] The Earth has a substantial amount of uranium, so if the demands increase, then there will plenty of uranium to meet up with the needs.

Demand.png












World mine production is about 60,000 tonnes per year, but a lot of the market is being supplied from secondary sources such as stockpiles, including material from dismantled nuclear weapons. Uranium is a very practical use for electricity.The graph below shows that uranium is more than 11,000 times more efficient in energy conversion than crude oil.[12]

The uranium comes from some 440 nuclear reactors with a total output capacity of about 377 000 megawatts (MWe) operating in 30 countries.  Belgium, Bulgaria, Czech Republic, Finland, France, Hungary, Japan, South Korea, Slovakia, Slovenia, Sweden, Switzerland and Ukraine all get 30% or more of their electricity from nuclear reactors. The USA has over 100 reactors operating, supplying 20% of its electricity. France gets three quarters of its electricity from uranium.

Potential long-range outcomes.[]

Nuclear power is expected to become cost competitive against coal and natural gas in the near future and as a result a large increase in the demand for uranium is anticipated. The cost of coal and natural gas to generate electricity is expected to grow as a result of constraints placed on the market in regards to carbon emissions. As well, the demand for uranium will increase as China increases it's energy consumption.[13]

For nuclear energy to maintain its current role in electricity generation in the US and around the world, a large number of new reactors will be needed. As well, to have a noticeable effect on carbon emissions and a cleaner environment, the existing reactor fleet will have to grow dramatically.

A lack of mining investment due to over supply and low commodity prices has left the world with a resounding shortfall in uranium. The gap between supply and demand, and the resulting price increase of uranium, has now led to a resurgence of uranium exploration.[14]

Interesting Facts about Uranium:[]

  • Uranium was discovered in 1789 by Martin Klaproth, a German chemist, who isolated an oxide of uranium while analyzing pitchblende samples from the Joachimsal silver mines in the former Kingdom of Bohemia located in the present day Czech Republic
  • It took until 1938 to discover that uranium could be split to release energy, that is fission. This was accomplished by Otto Hahn and Fritz Strassman
  • Henri Antoine Becquerel discovered that uranium was radioactive in 1896. Friend of Pierre and Marie Curie
  • One ton of natural uranium can produce more than 40 million kilowatt-hours of electricity. This is equivalent to burning 16,000 tons of coal or 80,000 barrels of oil
  • Uranium was named after the planet Uranus, discovered only eight years earlier in 1791
  • One pound of uranium will make a ball only 1.3 inches in diameter
  • A major league baseball weighs about 5.25 ounces. A uranium baseball would weigh over 8.5 pounds
  • While a gallon of milk weighs about 8 pounds, a gallon container of uranium would weigh about 150 pounds
  • Uranium has been used to color glass for almost 2 millennia
  • Uranium boils at about 3,818 degrees Celsius (about 6,904 degrees Fahrenheit)
  • Every human has about .0001 mg uranium inside their body
Advertisement