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Nuclear fission
Intermediate
Heavy nuclei split releasing energy.
A heavy nucleus such as U-235, hit by a neutron, splits into two medium nuclei plus 2–3 neutrons and about 200 MeV of energy.
1 kg of U-235 releases 8×10¹³ J, like 20,000 tonnes of TNT.
Most energy appears as kinetic energy of fragments.
In more detail
In nuclear fission, a heavy nucleus such as uranium-235 splits into two lighter nuclei, releasing neutrons and a large amount of energy. The released neutrons can cause further fissions.
Real-world uses
- Nuclear power plants generate electricity by controlled fission.
- Nuclear weapons use uncontrolled fission chain reactions.
- Nuclear power stations use fission of uranium-235 to produce heat, which drives steam turbines to make electricity.
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Frequently asked questions
Why is energy released?
Because the products have higher binding energy per nucleon, so mass is converted to energy.
How much energy is released?
About 200 MeV per fission event.
Why does fission release so much energy?
The fission products have higher binding energy per nucleon than the original heavy nucleus, so the difference is released.
Related topics in Atomic & Nuclear Physics
Carbon dating · Nuclear reactions · Q-value · Chain reaction · Nuclear reactors · Nuclear weapons