Fission power plants take advantage of the dependence of the binding energy per nucleon binding energy per nucleon on the mass of nuclei. The binding energy of uranium is about 7.5 MeV/nucleon, that of the fission products is about 8.5 MeV/nucleon. Since the fission products are more tightly bound, they have a smaller mass per nucleon. The fission of a uranium nucleus, therefore, liberates a mass equivalent of 1 MeV/nucleon.