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What Is Uranium? Types and Characteristics

What is Uranium? Types and characteristics

Uranium is a chemical element that is used as a nuclear fuel. It is the most widely used fuel in nuclear fission reactions. It is a natural element that can be found in nature. However, to be able to use uranium in a nuclear reactor it must undergo a certain treatment.

To know the peculiarities that make uranium so different from other substances, we must first consider some basic nuclear physics.

Basic Physical Considerations of Uranium

An atom of a nucleus and electrons that surround 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 separating is a new kind of force: an immensely powerful, short-range attractive force acts interchangeably between protons and neutrons (which from this point of view are all nucleons). The short-range nuclear force holds them together, opposing the repulsive effect of the positive charges of the protons. In this way, the neutrons act as "nuclear cement".

Characteristics of Uranium, an Unstable Element

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

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

The atoms of the same element can belong to different isotopes depending on the number of neutrons they contain.

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

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

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

The uranium-235 core is already under stress close to internal failure; a stray neutron approaching it can completely break it.

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

What Are the Types of Uranium?

Uranium can be natural, enriched, depleted.

Depleted Uranium

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

Enriched Uranium

Enriched uranium is another isotope mixture that has more 234U and 235U than natural uranium. Enriched uranium is more radioactive than natural uranium.

Natural Uranium

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

What Is Uranium For?

Uranium is very important in the nuclear power industry as a nuclear fuel. Specifically, nuclear plants often use enriched uranium. Still, there are other applications for depleted uranium.

Uranium is almost as hard as steel and much denser than lead. This characteristic makes depleted uranium an optimal element for which applications such as:

  • Counterweight in helicopter rotors and in aircraft parts
  • Protective shield against ionizing radiation
  • Ammunition component so that they more easily penetrate enemy armored vehicles.
  • Armor in military vehicles.

Uranium Isotopes

Uranium can be present in different compositions in its nucleus, that is, in different isotopes. Although uranium can be found in nature, most of it is in a configuration that is not the most suitable for generating nuclear reactions. For this reason, uranium atoms are artificially altered to become other, more unstable isotopes. These new isotopes of uranium will favor the generation of nuclear fission chain reactions.

Uranium-235 (235U) is the only fissile isotope, that is, with the capacity to cause a chain reaction of nuclear fission, present in nature. It is a characteristic that not even uranium-238, the most common of this element, possesses.

Other isotopes of uranium are as follows

  • Uranium-232 of synthetic origin.
  • Uranium-233 of synthetic origin.
  • Uranium-234 present in 0.0054% in nature.
  • Uranium-235 present in 0.7204% in nature.
  • Uranium-236 of synthetic origin.

Uranium-238 present in 99.2742% in nature.


    Published: April 8, 2014
    Last review: November 19, 2019