Spent nuclear fuel pool

Uranium: What It Is, Types, Isotopes, and Examples of Uses

Uranium: what it is, types, isotopes, and examples of uses

Uranium ore is a chemical element that is used mainly as fuel for nuclear reactors to generate electricity in nuclear power plants. It is a naturally occurring element that can be found in the earth's crust where the average uranium concentration is 4 parts per million.

In any case, in order to use it in a nuclear reactor and generate a nuclear chain reaction, it must undergo special treatment.

What Is Uranium Used For?

Its main applications are related to nuclear energy. However, its great hardness and high density make it an ideal material for other applications.

Below we list the main uses of uranium:

  • As nuclear fuel in nuclear power plants, even in breeder reactors: in this case, the ore must first undergo an enrichment process. Uranium oxide is the major component of fuel rods in nuclear reactors.

  • For the manufacture of nuclear weapons such as the atomic bomb.

  • Counterweight in helicopter rotors and aircraft parts.

  • Protective shield against ionizing radiation.

  • Component used in the production of armor-piercing ammunition and high resistance armor

  • Armor in military vehicles.

  • Estimate the Earth's age from its half-life of several hundred million years.

What Is a Uranium Atom Like?

An atom consists of a nucleus and electrons surrounding this nucleus. In turn, a nucleus consists of protons and neutrons. A proton has a positive charge. A neutron has no electrical charge and is neutral.

The positive charges on the protons try to force themselves outward. What prevents them from being separated is a new kind of force: an immensely powerful short-range attractive force acting interchangeably between protons and neutrons (which are all nucleons from this point of view).

The short-range nuclear force holds them together, opposing the repulsive effect of the positive charges on the protons. In this way, neutrons act as “nuclear cement”.

Uranium on the Periodic Table

We can find uranium in the periodic table with the atomic number 92 with the symbol "U". It is in the actinide group.

The nucleus contains 92 protons. Under these conditions the repulsive force between the protons is about to overcome the nuclear force.

Atoms of the same element can belong to different isotopes depending on the number of neutrons it contains.

If there are 146 neutrons present in the nucleus of the uranium atom, it is in an unstable situation. This form, which contains a total of 238 nucleons (92 protons and 146 neutrons), is called uranium-238 (U-238).

The next most likely arrangement is a uranium nucleus containing three fewer neutrons: U-235. Atoms with these lighter nuclei make up about 0.7% of the naturally occurring uranium.

Both cases are about the same element since it has 92 protons. However, they belong to different isotopes because one has 238 neutrons and the other 235.

The uranium-235 nucleus is already under stress close to internal rupture; a stray neutron coming close to it can break it completely.

For nuclear fission reactions we are interested in this combination between protons and neutrons that is so close to defeating the nuclear force. In this way, just by adding a neutron to the atom, it explodes and divides, generating other neutrons that can collide with other uranium atoms that are also at the limit.

Isotopes of Uranium

Uranium can occur in different compositions in its nucleus, that is, in different isotopes. Although uranium occurs naturally, most of it is found in a configuration that is not ideal for generating nuclear reactions.

Naturally occurring uranium consists of three isotopes: uranium-234, uranium-235 and uranium-238. Although all three isotopes are radioactive, only uranium-235 is a fissionable material that can be used for nuclear power.

Although all these isotopes are radioactive elements, only uranium-235 (U-235) is a fissionable material that can be used for nuclear power.

For this reason, the atoms of this element are artificially altered to convert them into other, more unstable isotopes. These new isotopes will favor the generation of chain nuclear fission reactions.

Other isotopes are as follows

  • U-232 of synthetic origin.

  • U-233 of synthetic origin.

  • U-234 is present in 0.0054% in nature.

  • U-235 is present in 0.7204% in nature.

  • U-236 of synthetic origin.

  • U-238 is a radioactive isotope present in 99.2742% in nature.

In nuclear physics , a decay product is the nuclide remaining from a radioactive decay. Often this decay comes from a sequence of steps called a decay chain. For example, uranium 238 ( 238 U) decays to thorium 234 ( 234 Th), which in turn decays to protactinium 234m ( 234m Pa), which also decays, and so on, up to lead 206 ( 206 Pb, which is stable).
During the decay, these particles also emit ionizing radiation, including alpha particles, beta particles, and gamma rays.

What Are the Types of Uranium?

Uranium can be natural, enriched, or depleted.


Depleted uranium is a mixture of the same three uranium isotopes except it has very little 234U and 235U. It is less radioactive than natural uranium.


Enriched uranium is another mix of isotopes that has more 234U and 235U than natural uranium. The enriched one is more radioactive than the natural one and more unstable, which makes it ideal for generating nuclear chain reactions.


Natural uranium is used to make enriched uranium ; the surplus product is depleted.


    Published: April 8, 2014
    Last review: December 2, 2022