When a nucleus fissions into two smaller ones, the total binding energy pr. nucleus is increased. Somewhat similarily when two nucleus fusion into one larger nucleus the binding energy is increased. Thus both fusion and fission are exothermic processes. This is the explaination I get in my school book for where the energy comes from in fusion and fission. The book seems to forget that all though the processes are exothermic, the energy created is in the shape of binding energy in the nucleus! How can we profit from this energy? How do they do it at nuclear power plants? Is binding energy the same as the kinetic energy of the atoms?