HOW DOES NUCLEAR REACTION HAPPEN?

Nuclear reactions occur when neutrons are fired at closely packed atoms with heavy nuclei (uranium or plutonium isotopes). These heavy nuclei break apart into lighter nuclei when hit by a neutron, in turn generating more neutrons which bombard other nuclei, creating a chain reaction. This process is known as fission. (Another process known as fusion releases energy by fusing together nuclei rather than breaking them apart.) By breaking down the nuclei themselves rather than releasing energy through a conventional chemical reaction, atom bombs can release more than 80 terajoules of energy per kilogram (TJ/kg).