Did You Know?
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Dr. Bertram Brockhouse shared the 1994 Nobel Prize in Physics for work he did at the NRX reactor at Chalk River. For more information, see: For a lesson about this topic, see: |
Fusion is the energy source of the Sun and all of the stars in the universe. In nuclear fusion, the nuclei (protons and neutrons) of two atoms are forced together to form a heavier nucleus. In fission you remember, the nucleus of an atom is split in two making two lighter isotopes.
In order for nuclear fusion to occur, the nuclei must be brought close together so that the nuclear force of attraction between the protons and neutrons overcomes the electric force of repulsion of the protons. Since the nuclear force acts only over small distances, it requires considerable energy to do this. For this reason, fusion occurs mostly in high temperature environments, where the particles are close together and fast moving. When smaller atoms, such as hydrogen and helium, are fused, more energy is released than is required. Larger atoms (larger than iron) generally do not fuse because they are less stable than iron.
The fusion process shown in the animation involves deuterium (hydrogen-2) and tritium (hydrogen-3) fusing to give helium and a neutron which is ejected from the atom at a high speed. The energy released in this reaction goes into the kinetic energy of the helium and the neutron. Fusion occurs in a star because the massive gravity of the star creates pressures so intense light elements such hydrogen are fused together to make deuterium. In this process, a positron and a neutrino are released (due to the conversion of a proton into a neutron). Fusion can also be achieved using extreme temperatures which also occur in stars.
All life on Earth is dependant on nuclear fusion. It is the energy source that warms our planet and gives us light. Here on Earth scientists have only been able to achieve fusion reactions lasting a few seconds but around the world there has been research into using nuclear fusion as an energy source. If successful, nuclear fusion could possibly result in a limitless supply of clean energy.