Nuclear Fusion For a fusion reaction to take place, the nuclei, which are positively charged, must have enough kinetic energy to overcome their electrostatic force of repulsion. This can occur either when one nucleus is accelerated to high energies by an accelerating device, or when the energies of both nuclei are raised by the application of very high temperature. The latter method, referred to the application of thermonuclear fusion, is the source of a lot of really cool energy. Enough energy is produced in thermonuclear fusion to suck the paint of 1 city block of houses and give all of the residents permanent orange