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Natural Uranium: Is Uranium Element Man-made or Natural?

Natural uranium is an element that has long been a contentious topic. On one side, there is the belief that it is a naturally-occurring element found in the Earth's crust and can be mined safely; on the other side, there are those who believe that uranium is artificial and its mining poses severe risks to human health.

Natural uranium: Is uranium element man-made or natural?

In a broad sense, natural uranium refers to natural uranium resources (including uranium ore and uranium contained in seawater) and those with the same isotopic composition as natural uranium.

It strictly refers to metallic uranium and its compounds (oxides, fluorides, carbides, nitrides). When used in comparison to enriched uranium and depleted uranium, it is used in this limited sense.

Natural uranium extracted from uranium contains an approximate proportion of 99.3% of isotope 238 and 0.7% of isotope 235. Of these, uranium 235 radioisotopes can be used as nuclear fuel in a nuclear reactor.

At the beginning of the 21st century, the power reactor most used to generate electricity in the world was the light water nuclear reactor. The extracted natural uranium is converted to enriched uranium by increasing the proportion of uranium 235 in uranium enrichment plants for use in light water reactors.

Non-concentrated uranium is called natural uranium.

What Is Uranium?

Uranium is a heavy metal found in small amounts in most rocks, soil, and water. However, it is more abundant in some places than others and can be mined from the ground.

Martin Heinrich Klaproth, a German chemist, discovered it in 1789. It was named after the planet Uranus, found eight years earlier.

It is a radioactive element, meaning it emits radiation as it decays. For example, the half-life of uranium-238 (the most common isotope) is 4.468 billion years, meaning it takes that long for half of a sample of uranium-238 to decay into lead-206.

This chemical element is used in nuclear weapons and reactors because of its unique properties. When uranium atoms are bombarded with neutrons, they split apart (fission), releasing energy and more neutrons. This chain reaction can be used to generate electricity or create an explosion.

It appears in the modern periodic table with the atomic number 92.

Is Uranium Man-made or Natural?

Uranium is a radioactive metal that occurs naturally. The United States, Russia, and France have the most uranium reserves.

Natural uranium is found in small amounts in all rocks, soil, and water. These minerals are more common in some types of rocks than others. Uranium ore deposits are found in many countries around the world. Australia, Canada, Kazakhstan, and Niger have the largest reserves of uranium ore.

The United States uses about one-fifth of all the uranium mined each year. Most of this uranium is used as fuel for nuclear reactors to generate electricity.

Where Does Uranium Come From?

Uranium is found in nature in small amounts. In fact, nearly all rocks and soils contain some uranium. However, only a tiny fraction of this uranium is found in concentrations high enough to be mined for commercial use.

It occurs naturally in the Earth as the result of the decay of radionuclides that are present in rocks and soil. The Earth's crust contains an average uranium concentration of 2 to 4 parts per million (ppm). For perspective, this is about the same concentration as tin or molybdenum. The top 15 feet (4.6 meters) of the Earth's surface has more than 99% of the world's known reserves of uranium ore.

While most uranium deposits are found in stable continental crustal rocks, some important deposits occur in sedimentary basins associated with ancient mountain belts. In addition, deposits related to mountain belts tend to be older and tend to have higher grades than other types of deposits.

Origin and Formation of Natural Uranium

Like other elements with an atomic number higher than iron, uranium atoms formed in supernovae. The primary uranium isotopes were 235-U, 238-U, and 236-U, which had transformed entirely into Thorium due to the short half-life.

When planet Earth formed, the rate of the 235-U isotope was close to 3% compared to the current 0.711%. Therefore, a higher initial concentration of 235 U could trigger a fission chain reaction under appropriate conditions. In this way, one of the few natural nuclear reactors located in Gabon, Africa, was created in the Oklo uranium deposit.

Where Is Uranium Found in Nature?

Uranium is widely distributed in the earth's crust and seawater and is estimated to be 40 times more than silver and tin. Among them, proven recoverable reserves are estimated at 5.47 million tons.

The major nations with uranium resources are Australia, Kazakhstan, Canada, South Africa, and the United States, in descending order of reserves. In addition, it is possible that the Democratic People's Republic of Korea (Republic of Korea, Japan Atomic Energy Industry Council), with an estimated 4 million tons of mineable reserves, may exceed Australia's proven number one reserve.

What Are the Different Forms of Uranium?

This element is found in nature in several different forms. The most common form is U-238, which makes up more than 99% of natural uranium. Other naturally occurring forms of uranium include U-235 (0.7%), U-234 (0.006%), and a tiny amount of U-236 (less than 0.001%).

U-235 is the form of uranium used in nuclear reactors and weapons. It is relatively rare, making up less than 1% of natural uranium.

U-234 is also present in minimal amounts in nature, but it is not used in reactors or weapons.

U-238 is the most common form of this element, making up more than 99% of natural uranium. It cannot be used in nuclear weapons or nuclear power plants because it is not radioactive enough. However, it can be converted into plutonium, which can be used in these uses. It decays by emitting an alpha particle.

Uranium as a Nuclear Fuel in Nuclear Power Plants

Nuclear power plants use uranium as a nuclear fuel to produce electricity. It can be found on the ground all over the world. It is mined and refined to create reactor fuel.

Mining and milling is a complex process that involves extracting uranium ore from the ground, processing it to remove impurities, and then enriching it to increase its uranium content.

Once the uranium has been mined and processed, it must be enriched before being used as fuel in a nuclear reactor. Enrichment involves increasing the percentage of uranium-235 in the uranium sample. This is done by separating the lighter isotopes of uranium from the heavier ones through centrifugation.

Enrichment is critical in making nuclear fuel because only uranium with a high percentage of uranium-235 will undergo fission when hit by a neutron, releasing energy that can be harnessed to generate electricity.

After enrichment, the enriched uranium is formed into pellets stacked inside metal rods called fuel assemblies in the form of uranium dioxide. These fuel assemblies are then placed inside the reactor core, where they will undergo nuclear fission and heat to produce steam, which drives turbines to generate electricity.

Uranium Hexafluoride is the heaviest gas known. Thanks to the heaviness of its molecules, it is possible to use centrifugation to separate the isotopes 235 U and 238 U, thus obtaining enriched uranium.

Uranium Decays

Uranium is a radioactive element that decays over time, emitting alpha. The half-life of uranium is 4.5 billion years, meaning it takes that long for half of the uranium atoms in a sample to decay. This decay product is used to date rocks and other nuclear materials.


In conclusion, natural uranium is found naturally in the environment and can be mined for use in various industries and nuclear energy applications. However, it is essential to note that natural uranium must undergo a refining process before it can be used safely in those applications; this process involves enriching or purifying the uranium from its other isotopes.

While natural uranium does occur naturally, there are also man-made sources of enriched or purified uranium available for use. Ultimately, whether you need to source your supply of natural or artificial enriched uranium depends on your specific needs and requirements.


Published: January 21, 2020
Last review: January 21, 2020