What Is a Fission Chain Reaction?

Fission

• Nuclear fission, as opposed to nuclear fusion, is a process that takes place at the atomic level of matter. The term "fission" refers to the splitting of an atom, which produces energy. This process is the opposite of nuclear fusion, in which two atoms are fused together, which requires vastly more amounts of energy than fission, and is the process that powers our sun. In the process of nuclear fission, heavy radioactive atoms, like Uranium or Plutonium, are bombarded with light atoms, such as Barium, in a chamber, which cause the dense and unstable atoms to break apart.

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• The structure of an atom is composed of a central nucleus orbited by an energetic cloud of electrons. Electrons are very light in comparison to the subatomic particles that make up a nucleus. The nucleus is made up of a like number of protons and neutrons, both of which make up the majority of the mass of an atom. Isotopes are atoms that have a varying amount of neutrons in comparison to the number of protons of an atom.

Uranium-235

• The element Uranium, for example, has an atomic number of 92, which means it has 92 protons, and should have the same number of neutrons. Uranium-235 is an isotope of the element, and has more than the usual amount of neutrons. Uranium-235 is also radioactive, meaning it is unstable in its natural state and emits particles and gamma rays. Uranium-235 and Uranium-238 used in nuclear fission because, when it is hit with a Barium atom, it breaks apart in a characteristic manner leaving the element Krypton and a few free neutrons. These neutrons are required to produce a chain reaction.

Chain Reaction

• A chain reaction in fission requires a catalyst to begin. When the heavy, unstable radioactive atoms are hit with a blast of the lighter atoms and split, the force of the atoms splitting sends sub atomic particles flying throughout the chamber in which the reaction occurs. These high-energy particles then crash into more of the radioactive atoms in the reaction chamber, in a process that continues producing enormous amounts of energy, as the radioactive material is annihilated by flying atomic fragments. At least one neutron from each broken uranium atom must strike another uranium atom for the chain reaction to continue.