IB Physics E4 Notes

Now that you have learned the basics of atoms and radiation, you need to understand how energy is produced in nuclear reactors. There are two types of nuclear reactions:

1. Fusion - the joining of two nuclei to form a larger nucleus, releasing lots of energy. 

   An example is the fusion of H-2 and H-3 to form He-4 and one neutron. This is the process that occurs in the sun.

2. Fission - the splitting of a large nucleus into two smaller nuclei, releasing less energy, although still a large amount. 

   An example is the fission of a U-235 nucleus by a neutron into Ba-141, Kr-92 and 3 neutrons. This is the process that occurs in nuclear reactors.

Whilst fusion has a higher energy output, it currently requires a higher energy input to initiate and is thus not industrially viable for now. Thus, fission is the current reaction used in nuclear reactors.