Uranium

uranium is a silvery-grayish metallic chemical element of the actinide series, its chemical symbol is U and its atomic number is 92 . For this reason, it has 92 protons and 92 electrons, with a valence of 6. Its nucleus can contain between 140 and 146 neutrons. Its most abundant isotopes are ²³⁸U, which has 146 neutrons, and ^235. U with 143 neutrons. Uranium has the highest atomic weight of all the elements found in nature. Uranium is about 70% more dense than lead, although less dense than gold or tungsten. It is slightly radioactive. It was discovered as an oxide in 1789 by M. H. Klaproth who named it after the planet Uranus that had just been discovered in 1781.

Features

In nature it occurs in very low concentrations (a few parts per million or ppm) in rocks, soil, water and living things. For its use, uranium must be extracted and concentrated from minerals that contain it, such as uraninite (see uranium mining). The rocks are chemically treated to separate the uranium, converting it into chemical uranium compounds. The residue is called sterile. These wastes contain the same radioactive substances that the original ore had and that were not separated, such as radium, thorium or potassium.

Natural uranium is made up of three types of isotopes: uranium-238 (²³⁸U), uranium-235 (²³⁵U) and uranium-234 (²³⁴U). Of each gram of natural uranium 99.284% by mass is uranium-238, 0.711% uranium-235, and 0.0085% uranium-234. The uranium-238/uranium-235 ratio is constant in the earth's crust, with some exceptions, such as the Oklo deposits where there is evidence that natural nuclear reactors were produced some 2 billion years ago.

Uranium decays very slowly, giving off an alpha particle. The half-life of uranium-238 is approximately 4.47 billion years and that of uranium-235 is 704 million years, making them useful for estimating the age of the Earth (uranium-thorium dating and uranium-lead dating).). Many contemporary uses of uranium make use of these unique nuclear properties. Uranium-235 is distinguished by being the only element found in nature that is a fissile isotope. Uranium-238 is fissile by fast neutrons, and is also a fertile material (which can be transmuted in a nuclear reactor into plutonium-239 which is fissile). It is possible to produce the artificial fissile isotope, uranium-233, from naturally occurring thorium, playing an important role in nuclear technology. While uranium-238 has a small probability of fission spontaneously or when bombarded by fast neutrons, uranium-235 has a higher probability of fission when bombarded by thermal neutrons, making it the main reaction responsible for the generation of heat in a nuclear reactor, and is the main source of fissile material for nuclear weapons. Both uses are made possible by uranium's ability to sustain a nuclear chain reaction.

Uranium, mainly U-238, plays a fundamental role in conserving the Earth's magnetic field.

Depleted uranium (uranium-238) is used in kinetic energy penetrators and shields for armored vehicles.

²³⁵U is used as fuel in nuclear power plants and in some nuclear weapon designs. To produce fuel, natural uranium is separated into two parts. The combustible portion has more ²³⁵U than normal, called enriched uranium, while the excess portion, with less U²³⁵ than normal, is called depleted uranium. Natural, enriched or depleted uranium is chemically identical. Depleted uranium is the least radioactive and enriched uranium is the most radioactive.

In 2009, the Japanese SELENE probe discovered traces of uranium on the Moon for the first time.

Origin

Along with all elements with atomic weights greater than iron, uranium forms naturally during supernovae explosions. The determining physical process in the collapse of a supernova is gravity. The very high gravity values that occur in supernovae are what generate the neutron captures that give rise to heavier atoms, including uranium and protactinium.

Uranium Reserves

World uranium production in 2009 was 50,572 tons, of which 27.3% was mined in Kazakhstan, 20.1% in Canada, 15.7% in Australia, 9, 1% in Namibia, 7% in Russia, and 6.4% in Niger.

The OECD and the IAEA periodically publish a report called Uranium: Resources, Production and Demand, known as the "Red Book", where an estimate of world reserves is made of uranium by country. The major producers are Canada, Australia, Kazakhstan, Russia, Niger, the Democratic Republic of the Congo, Namibia and Brazil. There are also prospecting and uranium deposits in different countries such as Colombia (in the Perijá mountain range, on the shared border with Venezuela), Peru (in the province of Carabaya in the Puno region), Argentina (with confirmed mines throughout the country.) and Spain, among other areas.

According to this report, the world's uranium resources are sufficient to meet current needs for up to eighty-five years. It is estimated that the total amount of conventional uranium stocks, which can be mined for less than USD 130 per kg, is about 4.7 million tons, which would meet the uranium demand for nuclear electricity generation for 85 years. However, the world's total uranium resources are considered much higher. Based on geological evidence and knowledge of uranium phosphates, the study considers more than 35 million tons available for exploitation.

World production

Global production by 2020, in tons per year

1.	Kazakhstan Kazakhstan	19477
2.	Australia	6203
3.	NamibiaNamibia	5413
4.	CanadaCanada	3885
5.	UzbekistanUzbekistan	3500
6.	NigerNiger	2991
7.	Russia Russia	2846
8.	ChinaChina	1885
9.	Ukraine Ukraine	744
10.	United States	6

Source: World Nuclear.

Application

The main use of uranium today is as fuel for nuclear reactors that produce 3% of the world's human-generated power.^{[citation needed]} For this, the uranium is enriched by increasing the proportion of the isotope U²³⁵ from the 0.71% that it presents in nature to values in the range 3-5%. It should be noted that to achieve a nuclear explosion, a proportion of 90% of U²³⁵ is needed, this means that nuclear reactors cannot explode nuclearly, although physical or chemical explosions can occur.

Depleted uranium (with a proportion of U-235 lower than natural), produced as a waste product after the use of uranium in nuclear power plants, is used in the production of armor-piercing ammunition and high-resistance armor; mainly due to its high density (about 19 g/cm³), its fragmentation into sharp pieces and above all because it is pyrophoric (it spontaneously combusts when it comes into contact with air at approximately 600 °C). Its use also entails the dispersal of radioactive contamination, as occurred during the First Gulf War.

Other uses include:

• Due to its high density, uranium is used in the construction of aircraft stabilizers, artificial satellites and sailboats (balasts/knifes).
• Uranium has been used as an aggregate for the creation of green or yellow fluorescent tones crystals.
• The long period of semi-disintegration of the isotope ²³⁸U is used to estimate the age of the Earth.
• The ²³⁸U becomes plutonium in the breeding reactors. Plutonium can be used in reactors or nuclear weapons.
• Some light fixtures use uranium, just like some photographic chemicals (uranium nitrate).
• His high atomic weight makes the ²³⁸U can be used as an effective shielding against high penetration radiation.
• Metal uranium is used for X-ray targets, to make high-energy X-rays.
• Depleted uranium is used as shielding in modern combat tanks, and missiles also carry depleted uranium in their spur.
• Phosphate fertilizers often contain high content of natural uranium, because the mineral from which they are made is typically high in uranium.

Human exposure

A person can be exposed to uranium (or its radioactive descendants such as radon) by breathing in airborne dust or by ingesting contaminated food and water. The amount of uranium in the air is very small, however, people who work in phosphate or fertilizer processing factories, or who live near nuclear weapons testing facilities, live or work near a field of modern battlefield where depleted uranium has been used, or who live or work near the exposure of a coal-fired power plant, uranium ore mining facility, or uranium enrichment facility for fuel, may have increased exposure to uranium. Houses or structures that are on top of uranium deposits (natural or man-made slag deposits) may have an increased incidence of radon gas exposure.

Most ingested uranium is excreted naturally. Only 0.5% is absorbed when insoluble forms of uranium, such as oxide, are ingested, while the absorption of the more soluble ones, such as uranyl ions, can be as much as 5%. However, soluble uranium compounds tend to to pass rapidly through the entire body while insoluble uranium compounds, especially when dust is inhaled into the lungs, pose a more serious exposure risk. After entering the bloodstream, absorbed uranium tends to bioaccumulate and remain for many years in bone tissues due to uranium's affinity for phosphates. Uranium is not absorbed through the skin, and particles alpha released by uranium cannot penetrate the skin.

Mutogenic genotoxics from uranium exposure can be treated with chelation therapy or by other means soon after exposure. Assimilated uranium is converted to uranyl ions, which accumulate in bone, liver, brain, and lungs. kidneys and reproductive tissues. Uranium can be decontaminated from steel surfaces and aquifers.

Effects

The normal functioning of the kidney, brain, liver, heart, and other systems can be affected by uranium exposure, because, in addition to being weakly radioactive, uranium is a highly toxic metal even in small amounts. Uranium is also toxic to reproduction. Radiological effects are generally local as alpha radiation, the main form of decay of U-238, has a very short range and does not penetrate the skin. Uranium compounds, in general, are poorly absorbed by the lining of the lungs and may remain a radiological hazard indefinitely. ^{[citation required]}. Uranyl ions UO₂⁺, such as those from uranium trioxide or uranyl uranium nitrate, have been shown to cause birth defects and damage to the immune system in breeding animals. laboratory, while the CDC has released a study saying that no cancer has been proven in humans resulting from exposure to natural disasters. Exposure to uranium and its decay products, especially radon, is widely known as well as health threats. Exposure to strontium-90, iodine-131, and other fission products is not related to uranium exposure, but may result from medical procedures or exposure to spent nuclear fuel or fallout. of the use of nuclear weapons.

Although accidental inhalation exposure to a high concentration of uranium hexafluoride has caused deaths, those deaths were associated with the generation of highly toxic hydrofluoric acid and uranyl fluoride and not the uranium itself. Finely divided metal presents a fire hazard because the small particles can ignite spontaneously in air at room temperature.

Nuclear power plants do not pollute the atmosphere, however, they do generate a certain amount of radioactive waste. These residues are harmful to health and the environment, therefore, they must be stored in special areas for a certain time, some a few years and others thousands of years. Efforts are currently focused on recycling this waste with notable successes such as the BN-800 reactor and MOX fuels. In the future it is expected to abandon uranium and replace it with nuclear fuels that generate less waste or negligible amounts.