What is uranium?
Uranium metal is silver coloured with a grey surface and is almost as strong as steel.
Natural uranium is a mixture of three types or isotopes called U-234 (234U), U-235 (235U) and U-238 (238U). All three are the same chemical but have different radioactive properties.
In soil it is found in typical concentrations of a few parts per million (ppm). Certain rocks contain concentrations of uranium high enough to be mined.
The rocks are taken to a chemical plant where the uranium is removed and converted into uranium chemicals or metal.
The residue that remains is called mill tailings. Tailings contain large amounts of chemicals and radioactive substances that were not removed, such as radium and thorium.
Definition of uranium
The chemical element of symbol U, atomic number 92 and atomic weight 238.03. The melting point is 1132ºC (2070ºF), and the boiling point is 3818ºC (6904ºF). Uranium is one of the actinides.
The main characteristic of uranium is its weight: it is the element that has the highest atomic weight among those that can be found in nature.
Uranium is a very dense metal, strongly electropositive and reactive, ductile and malleable, but a poor conductor of electricity.
Many uranium alloys are of great interest in nuclear technology, as pure metal is chemically active and anisotropic and has poor mechanical properties.
However, cylindrical rods of pure uranium coated with silicon and stored in aluminum tubes (ingots) are used in nuclear reactors.
Uranium alloys are useful in the dilution of reactor-enriched uranium and in the supply of liquid fuels. Depleted uranium from the fissile isotope 235U has been used to shield containers for the storage and transport of radioactive materials.
Whoever discovered Uranium
Discovered by the German chemist Martin Heinrich Klaproth in 1789, uranium is found at very low levels in living things, water and rocks. Its origin is in supernovae (star explosions).
There are currently a number of techniques that allow uranium to be extracted and concentrated.
Enriched uranium is the result of a process applied to natural uranium to obtain a specific isotope. This process, in turn, generates a by-product known as depleted uranium.
Among the most common isotopes of uranium are uranium-238 (which has 146 neutrons) and uranium-235 (with 143 neutrons).
Uranium, whose chemical symbol is “U”, has a silver-greyish colour and an atomic number of 92. It has the highest atomic weight among all the elements found in nature.
It is a very dense metal, approximately 70% denser than lead, although less dense than gold or tungsten, strongly electropositive and reactive, ductile and malleable, but poorly conductive to electricity.
It’s slightly radioactive. The abundance of uranium in the earth’s crust is 0.0004%, it occurs mainly in rocks, soils, and water (uranium in the form of complex uranium salts and carbonates can also be found in the sea). In living beings, it is found in very low concentrations.
In its natural state, uranium is composed of three radioactive isotopes: uranium-238 (U238) with 99.2739%, uranium-235 (U235) with 0.7205% and uranium-234 (U234) with 0.0056%.
The isotope U235 is the cause of the great importance of this element since it is the valid fissile isotope, the only fissile isotope found in nature and the only element naturally found with this characteristic being uranium.
Properties of Uranium
One of the radioactive properties of uranium is half-life or the time it takes half the isotope to emit its radiation and transform into another substance.
Half-lives are very long (about 200,000 years for 234U, 700 million years for 235U, and 5 billion years for 238U).
This is why uranium still exists in nature and has not completely declined.
The 235U isotope is useful as a fuel in power plants and weapons.
To produce fuel, the natural uranium is separated into two portions. The fuel portion has more than 235U of fuel than normal and is called enriched uranium.
The remaining portion with less than 235U than normal is called depleted uranium. Natural, enriched or depleted uranium is chemically identical.
Depleted uranium is the least radioactive, enriched uranium the most radioactive.
These decaying elements produce other forms of radiation, beta, and gamma, which can penetrate the human body, causing tremendous damage.
They destroy and kill the cells, causing radiation poisoning.
They can also disrupt cell function.
Although the human body can often repair itself, damaged cells proliferate wildly (what happens in cancer) or cause genetic mutations that we pass on to our children.
Marie Curie was never fully aware of the health risks of radiation. On the contrary, it is said that he slept with a bright vial of radioactive isotopes by the bedside.
But she and many of her colleagues died of diseases related to radiation exposure.
Radiation can be dangerous, but every time a radioactive atom fires one of those tiny missiles, it generates a potentially very useful by-product (other than helium): heat.
Health Effects of Uranium
People are always exposed to a certain amount of uranium in food, air, soil, and water because it is naturally present in them.
Food, such as vegetables, and water will provide us with small amounts of natural uranium and we will breathe minimal concentrations of uranium into the air.
The concentration of uranium in shellfish is normally so low that it can be quietly ignored.
People who live near hazardous substance landfills or mines, those who work in the phosphate industry, those who eat crops that grew on contaminated soil, or those who drink water from a uranium landfill site may experience higher exposure than other people.
Uranium glasses are banned, but some artists who still use them for glass work will experience greater than normal exposure.
Because uranium is a radioactive substance, its effects on health have been investigated. Scientists have not detected any harmful effects on radiation from natural uranium levels.
However, chemical effects may occur after large amounts of uranium are taken and may cause effects such as liver disease.
When people are exposed to uranium radionuclides that are formed during radioactive decay over a long period of time, they can develop cancer.
The chances of getting cancer are much higher when people are exposed to enriched uranium because it is a more radioactive form of uranium.
This form of uranium emits harmful radiation, which can cause people to develop cancer within a few years. Enriched uranium can cause reproductive effects during accidents at nuclear power plants.
Whether uranium can have effects on human reproduction or is not currently unknown.
Environmental effects of uranium
Uranium can be found in the environment naturally in very small amounts in rocks, soil, air, and water. Humans add uranium metals and compounds because they are eliminated during mining and textile processes.
Uranium is a radioactive material that is highly reactive. As a result, it cannot be found in the environment in its elemental form.
The uranium compounds that have formed during the uranium reaction with other elements and substances dissolve in water.
The water solubility of a uranium compound determines its mobility in the environment as well as its toxicity.
In the air, uranium concentrations are very low. Even at higher than normal concentrations in the air, so little uranium is present per cubic metre that less than one atom is transformed every day.
Uranium in the air exists as dust that will fall into surface water, plants or soils through sedimentation or rainwater. It will then sink into the sediments or lower soil layers, where it will mix with the uranium that is already present.
In water, most of the uranium is dissolved uranium that is derived from the rocks and soil on which the water flows. Some of the uranium is in suspension so that the water takes on a muddy texture.
Only a very small amount of uranium in water sediments from the air. The amounts of uranium in drinking water are generally very low.
Water containing low amounts of uranium is normally safe to drink. Due to its nature, fish or vegetables are unlikely to accumulate and the uranium that is absorbed will be quickly eliminated through urine and feces.
In 1942, an American team from the Manhattan Project, led by Italian physicist Enrico Fermi, built the first nuclear reactor on the floor of a squash court on the campus of the University of Chicago.
Fermi showed that even natural uranium, with a very low proportion of fissile material, could be used to create a chain reaction. The trick was to use graphite as the “moderator”.
Moderators cause chain reactions more easily by slowing neutrons down, making it more likely that they can split other cores.
Fermi’s nuclear reactor offered an alternative route to the bomb.
When a neutron strikes one of the non-fissile nuclei of uranium-238, it can convert it into a new element, plutonium.
The success of the Manhattan Project was horribly marked by the launch of the two atomic bombs, one uranium, the other plutonium.
What followed was a long stalemate. For decades, the world was trapped by the Cold War.
New uses for Uranium
In the 1950s, a new branch of nuclear research began investigating the possibility of developing nuclear reactors specifically for generating electricity.
Today, about 10% of the world’s electricity is generated from the fission of uranium atoms.
The elementary and most important use of uranium is in the field of nuclear power, as fuel for nuclear reactors that generate heat producing 17% of the world’s electricity.
Although it is the main use, it is not the only one; uranium also has applications in various fields:
Industrial applications: for analysis and process control purposes.
Medical applications: in diagnosis and therapy of diseases.
Agri-food applications: in the production of new species, food preservation treatments, insect pest control, and vaccine preparation.
Environmental applications: in the determination of significant quantities of pollutants in the natural environment.
Other applications: such as dating, which uses the properties of carbon-14 fixation to bones, wood or organic waste, determining its chronological age.
Uses in Geophysics and Geochemistry, which take advantage of the existence of natural radioactive materials to fix the dates of rock, coal or oil deposits; it can also be useful to estimate the age of the Earth due to the semi-disintegration period of U238 which is approximately 4,470 million years and U235 which is 704 million years.
Uranium is very important in the nuclear power industry as a nuclear fuel. In particular, nuclear reactors often use enriched uranium. Even so, there are other applications of depleted uranium.
Uranium is almost as hard as steel and much denser than lead. This feature turns depleted uranium into an optimal element for certain applications such as, for example:
- Counterweight on helicopter rotors and aircraft parts.
- Protective shield against ionizing radiation.
- Ammunition component to make it easier to penetrate enemy armoured vehicles.
- Shielding in military vehicles.