Uranium is the heaviest naturally-occurring element on Earth, with 92 protons in its nucleus. It is essentially composed of two isotopes:
Uranium is an abundant source of concentrated energy. Unlike fossil fuels which are combined with oxygen during burning to release heat, uranium atoms can be made to split or fission to release heat. A kilogram of natural uranium produces as much heat as 20 tonnes of coal. This heat can be harnessed to make steam and generate power.
Uranium is found in more than 200 different minerals; which are mostly prevalent in granite and sedimentary rocks. It is common in the Earth's crust and is found in a wide variety of geological settings. The Earth’s crust is estimated to contain an average of between 1 and 4 parts per million (ppm) of uranium. Uranium also occurs in seawater, with seawater estimated to contain an average of .003 ppm, and can be recovered from the oceans.
Uranium ore can be mined by underground or open-cut methods, depending on its depth. After mining, the ore is crushed and ground. It is then treated with acid to dissolve the uranium, which is recovered from solution. Uranium may also be mined by in situ leaching (ISL), where it is dissolved in situ from a porous underground ore body and pumped to the surface. The end product of the mining and milling stages, or of ISL, is uranium oxide concentrate (U3O8). This is the form in which uranium is sold.
Uranium is mainly used as fuel in nuclear power reactors for electricity generation. Beyond providing about 14% of the world’s electricity, there are many major other uses of uranium through the production of radio-isotopes, including: