What is uranium enrichment, where does uranium come from and what is it used for?
Here's what you need to know about the metal
IRAN has said it will recommence its uranium enrichment programme at "industrial levels" following President Donald Trump's withdrawal from the Iran nuclear deal.
But what exactly is uranium, what is it used for and what is uranium enrichment? Here's what you need to know.
What is uranium?
Uranium is a chemical element of the periodic table and is a hard, dense, malleable, ductile, silver-white, radioactive metal.
Its chemical symbol is U and atomic number is 92.
It is the principle fuel for nuclear reactors, fuelling nuclear power plants to generate electricity.
Uranium can also be used in the manufacture of nuclear weapons, as well as a high density penetrators in the military.
It can primarily be found in resources in Australia, Russia, Canada, Kazakhstan and Iran.
Where does uranium come from?
Uranium can be found in rocks and seawater but like other metals it is rarely found in sufficient concentrations.
According to , it's reported Australia's known resources are over 1.6million tonnes of uranium, Kazakhstan has over 700,000 tonnes of uranium and Canada and Russia have over 500,000 tonnes.
Iran is believed to have the tenth largest uranium resource in the world, with large reserves to use as nuclear fuel in Bandar Abbas, Yazd, North Khorasan and Iranian Azerbaijan.
Several other countries have significant uranium resources, including South Africa, Niger, Brazil, China, Namibia, Mongolia, Uzbekistan and Ukraine.
What is it used for?
Enriched uranium can be used for both military and civilian purposes.
In the military it is used in high-density penetrators, an ammunition consisting of depleted uranium and other elements, such as titanium or molybdenum.
At high impact speed, the density, hardness and pyrophoricity of the projectile enable the destruction of heavily armoured targets.
Depleted uranium, an ‘enriched’ form of the metal, can also be used to harden tank and vehicle armour, and as a shielding material in some containers used to store and transport radioactive materials.
The high density of depleted uranium makes it more effective than lead in halting radiation.
Other uses include counterweights for aircraft control surfaces, as ballast for missile re-entry vehicles and as a shielding material.
Two were developed by the US during World War II: a uranium-based device called "Little Boy" whose fissile material was highly enriched uranium; and a plutonium-based device whose plutonium was derived from uranium-238.
The uranium-based Little Boy device became the first nuclear weapon used in war when it was detonated over the Japanese city of Hiroshima on August 6, 1945.
Exploding with a yield equivalent to 12,500 tonnes of TNT, the blast and thermal wave of the bomb destroyed nearly 50,000 buildings and killed approximately 75,000 people.
Initially it was believed that uranium was relatively rare, and that nuclear proliferation could be avoided by simply buying up all known uranium stocks, but within a decade large deposits of it were discovered in many places around the world.
In civilian uses, radioactive uranium is used to fuel nuclear power plants as one kilogram of uranium-235 can produce as much energy as 1,500 tonnes of coal.
However, prior to the discovery of the metal's radioactivity properties, uranium was used in small amounts for yellow glass and pottery glazes, such as uranium glass and in Fiestaware.
What is uranium enrichment?
Uranium as it is taken directly from the Earth is not suitable as fuel for most nuclear reactors and requires enrichment to make it viable.
Enriched uranium is a type of uranium in which the composition of uranium-235 has been increased through the process of isotope separation and - in this form - is a critical component for both civil nuclear power generation and military nuclear weapons.
Uranium ore can be mined by underground or open-cut methods and after mining the ore is crushed and ground, before being treated with acid to dissolve the uranium, which is recovered from solution.
The end product of the mining and milling stages is uranium oxide concentrate, the form in which uranium is sold.
The uranium oxide is then converted into uranium hexafluoride gas which enables it to be enriched. as it allows greater technical efficiency
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After enrichment, the gas is converted to uranium dioxide which is formed into fuel pellets, which are placed inside thin metal tubes, then known as fuel rods, which are assembled in bundles to become the fuel elements or assemblies for the core of the reactor.
In a typical large power reactor there might be 51,000 fuel rods with over 18 million pellets.
When the uranium fuel has been in the reactor for about three years, the used fuel is removed, stored, and then either reprocessed or disposed of underground.
The International Atomic Energy Agency attempts to monitor and control enriched uranium supplies and processes in its efforts to ensure nuclear power generation safety and curb nuclear weapons proliferation.
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