Renewable Energy

How are nuclear fission and nuclear fusion different?
Answered by Craig C. Freudenrich and Discovery Channel
  • Craig C. Freudenrich

    Craig C. Freudenrich

  • Discovery Channel

    Discovery Channel

  1. Nuclear power plants use a process called nuclear fission to create heat energy for making electricity. It's not to be confused with the term only one letter off -- nuclear fusion. Although both of these processes can create energy, they're very different. For one, nuclear fusion does not produce radioactive wastes, which has been one of the criticisms of nuclear fission and the reason many people oppose nuclear power [source: University of Texas at Austin].

    In nuclear fission, a neutron splits a heavy atom of uranium into two lighter ones. The split is accompanied by a large amount of heat energy and more neutrons. The neutrons go on to split nearby uranium atoms in a chain reaction. The rate of fission in this chain reaction is controlled by the nuclear reactor's control rods. The lighter atoms are the radioactive wastes that cannot be harnessed for more energy. The downside is toxic waste that hangs around for centuries and has to be disposed of somewhere.

    In contrast, nuclear fusion combines lighter atoms to form heavier ones. Specifically, isotopes of hydrogen combine to form helium isotopes and energy. It's much more similar to how stars -- including the sun -- create energy and heat in their cores.

    It's not easy to get hydrogen isotopes close enough to fuse in a controlled environment here on Earth. It takes intense heat and pressure to overcome the repulsive forces between their atoms. Nuclear fusion reactors are being developed that use high-intensity magnetic fields or high-intensity laser beams to bring the isotopes together for fusion to occur.

    Although nuclear fission-powered plants have been in use since the 1950s, prototype nuclear fusion reactors are still not practical or economical for commercial use.  Nuclear fission plants also carry the danger of meltdowns such as those that occurred recently in the Fukushima-Daiichi nuclear power plant in Japan, which was damaged by an earthquake and tsunami in March 2011. As a result of this accident, many nations are reevaluating their use of nuclear fission power.


    Nuclear Fusion Qa3
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  2. Nuclear fission splits atoms to create energy, whereas nuclear fusion combines them. The safety of using nuclear fusion relies on the types of isotopes used in the process. For example, by performing nuclear fission using deuterium and tritium -- two hydrogen isotopes -- unsafe levels of radioactive neutrons are released. Replacing the tritium isotope with the correct amount of heated helium-3 isotopes can produce vast amounts of energy without the radioactive side effects.

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