If the nucleus of a heavy atom–such as Uranium–absorbs a neutron, the nucleus can become unstable and split. This is called nuclear fission. Fission releases energy in the form of heat. Although fission can occur naturally, fission as encountered in the modern world is usually a deliberate man-made nuclear reaction.
Have you ever played with marbles?
Imagine about 100 marbles lying on a flat surface and roughly forming a circle. What would happen if you took another marble and threw it at them? They would fly all around in different directions and groups. That is exactly what happens in nuclear fission. The filled circle is like an atom’s nucleus. The marble being thrown is like a “neutron bullet”.
|Nuclear Fission||Nuclear Fusion|
|Definition:||Fission is the splitting of a large atom into two or more smaller ones.||Fusion is the fusing of two or more lighter atoms into a larger one.|
|Natural occurrence of the process:||Oklo’s Natural Fission Reactors||Fusion occurs in stars, such as the sun.|
|Byproducts of the reaction:||Fission produces many highly radioactive particles.||Few radioactive particles are produced by fusion reaction, but if a fission “trigger” is used, radioactive particles will result from that.|
|Conditions:||Critical mass of the substance and high-speed neutrons are required.||High density, high temperature environment is required.|
|Energy Requirement:||Takes little energy to split two atoms in a fission reaction.||Extremely high energy is required to bring two or more protons close enough that nuclear forces overcome their electrostatic repulsion.|
|Energy Released:||The energy released by fission is a million times greater than that released in chemical reactions; but lower than the energy released by nuclear fusion.Fission U235 + n is a total of 236 amu then 180MeV/236 =0.763MeV per nucleon||The energy released by fusion is three to four times greater than the energy released by fission.Fusion D+T releases 17.6MeV
D=2 atomic mass units (amu) and T =3 so total is 5, then 17.6MeV/5=3.52MeV per nucleon
Center for Nuclear Science and Technology Information of the American Nuclear Society
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