Which is better a nuclear hook up or the break up? In other words, is Nuclear Fusion better or is Nuclear Fission? The thing these two have in common is nuclear energy. Nuclear energy is the energy released during fission or fusion, and then we harness the energy to generate electricity. When comparing fission and fusion, nuclear fusion seems to be somewhat safe and the most reliable energy source between the two. Nuclear fission has been under a larger study as well as having a more successful outcome than nuclear fusion, but nuclear fusion seems to give off more energy and has better environmental benefits. Nuclear fission is when a heavy nucleus, like uranium, splits into smaller fragments or nuclei. This occurs because of the large amount