All about uranium
Uranium is a quite common natural metal found in soil, rock and water all over the Earth. Its natural radioactivity is the principal source of heat that prevents the Earth’s mantle from cooling. Owing to this property, uranium has become the main material used by the nuclear industry for the production of electricity.
The uranium content of natural uranium ore varies about from 0.01% to over 40%. Uranium occurs widely on Earth.
- In the Earth’s crust, uranium is quite common with a bulk grade of about 3g/metric ton. This grade varies strongly depending on the type of rocks. This adds up to about one trillion metric tons of uranium in the Earth’s crust alone, not including that found in the mantle.
- Seawater contains approximately 3mg/cubic meter, making a total of about 4.5 billion metric tons of uranium dissolved in the seas and oceans. Uranium is also often found in fresh water in varying concentrations.
- The Human body also contains between 90 to 150 micro grams of uranium.
The uranium atom
Uranium is the heaviest of all naturally occurring chemical elements, with 92 protons in each atom. It exists in 3 different forms or isotopes that differ from one another according to the number of neutrons in each atom. These isotopes are identified by atomic weight, which is simply the total number of protons and neutrons forming its atomic nucleus.
The uranium found in the Earth’s crust is primarily a mixture of two isotopes:
- uranium 238 (U238)
- uranium 235 (U235)
The U238 isotope is a very stable form that makes up about 99.28% of all naturally occurring uranium. Most of the rest is U235 (0,71%), which is the only natural fissile uranium that can produce a lot of energy under controlled circumstances. The third isotope found in a very small amount (0,006%) is uranium-234.
Uranium 235’s most useful property is that its atomic structure can be changed in a process that releases energy in the form of heat. Inside a nuclear reactor, this heat is harnessed to generate electricity without producing greenhouse gases. This natural fissile property makes it possible to use it in other sectors.
Uses of radioactivity
Generating electricity is not uranium’s only use. Uranium and other nuclear materials are also used in space exploration, food safety or medicine fields:
- Healthcare: radiodiagnosis is used to explore the human body and to diagnose certain disease: identifying the location of tumors, the cancer stages as well as the stages of cardiovascular disease, identifying hidden bone injuries (sports injuries) or respiratory system injuries in burn patients, diagnosing kidney disease. Radiation therapy uses the energy from ionizing radiation to destroy cancer cells.
- Ionization detectors: detecting the presence of various gases in the atmosphere. They have multiple uses, including fire detectors and firedamp concentration detectors in mines.
- Industrial radiography: used to X-ray metallic parts and to check welds. Gamma radiography of this type is widely used in metallurgy and in aeronautics.
- Industrial irradiation: allowing development of more resistant and lighter materials. It has many uses in medicine and industry, including lighter prostheses and stronger electric cables.
- Energy: operating nuclear power stations; operating nuclear-powered ships, submarines, spaceships and satellites.
- Other: determining the age of the geological formations and the age of rare archeological or historical artifacts.
Uranium formation in Eastern Gobi, Mongolia
- Nature has worked for millions of years to form the uranium deposits in the Dornogobi region. Over time, the rainwater has seeped into the sedimentary layers of the Earth and dissolved the natural uranium contained in the rock.
- These sedimentary layers are made up of alternating strata of impermeable clay and more permeable sandstone. Water carrying the dissolved uranium circulates through the sandstone layers. When the water encounters a natural environment with a specific chemical composition, the uranium precipitates. An uranium mineralized body is starting and might continue to enrich if the process is long lasting.
- In this way, large quantities of uranium naturally accumulate at particular trap locations, and it can become economically feasible to mine these concentrations of the mineral. The geologists at COGEGOBI look for such areas where uranium has been deposited and assess them to determine whether the uranium can become an economic resource.
Discovery of uranium
Uranium was discovered in 1789 by the Prussian chemist Martin Heinrich Klaproth while examining a piece of rock brought to him from a mine at Saint Joachimsthal. The rock was made of pitchblende (UO2), a type of uranium mineral also called uraninite. Klaproth named the compound he had found uranerz in reference to the planet Uranus, which had been discovered eight years earlier by William Herschel.
It was not until 1841 that the French chemist Eugène-Melchior Péligot determined that uraninite was composed of two atoms of oxygen and one of a metal that he isolated and named uranium.
Radioactivity was discovered much later, in 1896 by Frenchman Henri Becquerel, who observed that photographic plates were blackened by the spontaneous emission of invisible rays by uranium. This was the manifestation of a hitherto unknown phenomenon: natural radioactivity.