Spent nuclear fuel pool



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

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

Basic physical considerations of uranium

An atom 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 electric charge and is neutral.

The positive charges of the protons try to push violently outwards. What prevents them from separating is a new kind of force: an immensely powerful short-range attraction force, acting indistinctly 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 positive charges on protons. In this way, neutrons act as & ldquo; nuclear cement. & Quot ;.

Characteristics of uranium, an unstable element

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

Atoms of the same element may belong to different isotopes depending on the number of neutrons they contain.

If there are 146 neutrons in the nucleus of the uranium atom, it is in an unstable state. This form of uranium containing 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 minus neutrons: uranium-235. The atoms with these lighter nuclei make up about 0.7% of the naturally occurring uranium.

Both cases are 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 rupture; A stray neutron approaching it can break it completely.

For nuclear fission reactions we are interested in this combination of protons and neutrons that is so on the verge of overcoming the nuclear force. Thus, by simply 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.

Enriched uranium and depleted uranium

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

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

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

Applications of uranium

Uranium is very important in the nuclear power industry as a nuclear fuel. Specifically, nuclear ractures 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 makes depleted uranium an optimal element for applications such as:

  • Counterweight in helicopter rotors and parts of aircraft
  • Protective shield against ionizing radiation
  • Component of ammunition so that they can more easily penetrate the armored vehicles of the enemy.
  • Shielding in military vehicles.


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    Last review: August 29, 2017