Uranium is a naturally-occurring element in the Earth’s crust. It is the raw material that is used for nuclear fuel. Traces of it occur almost everywhere on the planet. However, uranium mining only takes place where it is naturally concentrated. In order to make nuclear fuel from uranium, it must first be extracted from the rock in which it is found, then enriched before it is made into pellets that are then loaded into assemblies of nuclear fuel rods.
Uranium is removed from the ground in three ways: open pit, underground, and in-situ leach (ISL). The way it is done depends on a variety of factors including the geological and geotechnical characteristics of the uranium deposit, its mineralogy and rock type, as well a number of other factors.
Once it is taken from the ground, uranium production continues with the milling process. This is done close to the mine and requires the rock to be crushed and then chemically treated in order to separate out the uranium. A slurry is produced and the uranium is suspended in water. It is treated with Sulphuric acid in order to dissolve the uranium oxides and leave the remaining rock and other minerals behind as mine tailings.
However, since many businesses have shifted to in situ leaching. This is because it can be accomplished without any major ground disturbance. Instead, groundwater, with a lot of oxygen, is injected into the mine and is circulated through the rock in order to extract the uranium. The solution with dissolved uranium is then pumped to the surface. Either way, a liquid with uranium dissolved in it is produced.
Uranium mining companies then separate it out through an ion exchange. It is precipitated from the solution, filtered, and dried. It produces a uranium oxide concentrate which is bright yellow in color. It is then sealed in drums and enriched because most of the nuclear power reactors require ‘enriched’ uranium fuel. However, the enrichment process needs to have the uranium in gaseous form. It creates two streams of the gas, one that is enriched and the other that is depleted and has little immediate use.
The enriched uranium is then transported to a fuel fabrication plant where it is converted to a uranium dioxide powder. It is then pressed in order to form small fuel pellets. The pellets are then heated in order to make a ceramic material which is then inserted into thin tubes and forms fuel rods. The fuel rods are then grouped together and form fuel assemblies and can be several meters long. The number of fuel rods used to make each fuel assembly depends on the type of reactor and can be anywhere from around one hundred to around one thousand.
The International Atomic Energy Agency or IAEA sets safety standards and provides guidelines and advice in order to foster sustainable uranium production cycle activities. It also works alongside the World Nuclear Association whose mission is “to promote a wider understanding of nuclear energy among key international influencers by producing authoritative information, developing common industry positions, and contributing to the energy debate.”