Uranium is a metallic element, which was discovered in 1789, by a German chemist Martin Heinrich Klaproth. For a century and a half, people didn’t really understand the significance of this discovery.
In the Roman Empire, it was used to colour the ceramic glazes into yellow. Until 1938, people didn’t know the full capability of this element. Otto Hahn along with Lisa Meitner introduced Nuclear fission.
What is Nuclear fission?
Nuclear fission is a nuclear reaction or radioactive decay process which results in the splitting of atoms into smaller and lighter nuclei. This process produces gamma photons and releases a huge amount of energy.
The Use of Nuclear Power
Uranium soon became a powerful fuel for nuclear power plants using a process of controlled fission. That allows us to extract a large amount of energy from a small amount of fuel. For example, one kilogram of uranium can produce the same energy as 1500 tons of coal.
It was also used for chemical warfare such as bombs and other nuclear weapons. Its uses in medicine were under shadow until Irène Joliot-Curie (daughter of Marie Curie) and her husband, Frédéric Joliot-Curie discovered artificially produced radionuclides. This was one of the crucial steps toward the modern-day X-ray.
How is it made?
Uranium is found in small amounts in rocks and in seawater. However, in large quantities, it is dug up from the mines mostly from Kazakhstan, Canada, Australia, Namibia, Niger and Russia.
The mining process before was much more complicated, while today they can be accomplished without major ground disturbance. To extract this material, water injected with oxygen is circulated through the uranium ore. Then, the solution of uranium can be pumped to the surface.
The solution is then separated, filtered and dried to produce a clean uranium oxide concentrate which is called ‘Yellowcake’ because of its bright yellow appearance.
The majority of nuclear power plants use enriched uranium which increases the uranium-235 concentration from 0.7% (the natural form) to 3-5%. A small number of reactors which are mostly in Canada, use natural uranium which doesn’t need additional enrichment.
The enrichment process requires it to be in gas form, which is a gas at relatively low temperatures. This gas is then fed to centrifuges, which have rapidly spinning vertical tubes which separate 235 from 238 uranium isotope, as 238 is a bit heavier.
Nuclear Fuel Making
The enriched mixture is sent to a fuel fabrication plant and converted to uranium dioxide powder. This is pressed into small fuel pellets which are heated and converted into hard ceramic material. Pellets are inserted into thin tubes (fuel rods), which are grouped together to form fuel assemblies.
The number of these rods can range from 90 to 200, depending on the type of reactor they are shipped to. Fuel can stay in the reactor core for several years after this process.