• Question: Is nuclear fusion really unlimited? If not how long will it last us?

    Asked by 562xmasen23 to Saiful, Piers, Paul, Olivia, Oli, Meggi, Jawwad, Iain, Hannah, James, Chris, Javier, Laurence, Thomas on 10 Jan 2017. This question was also asked by ModShane, pho3b3.
    • Photo: Piers Barnes

      Piers Barnes answered on 10 Jan 2017:


      Strictly speaking, the fuel needed for nuclear fusion is limited because the Earth has a finite size. However, the simplest fuel that can be used is deuterium, which is the same as hydrogen except that the nucleus contains both a proton and a neutron instead of just a proton. On Earth deuterium can be found in about 0.015% of water molecules. Even though this is a small percentage, there is a lot of water on Earth. If industrial fusion reactors can be made to yield more energy than they consume to run them, then a large reactor would probably consume on the order of around a kilogram of fuel per day. Given there are more than a trillion kilograms of deuterium on Earth it would take a very long time to consume it all, and additionally some of the reaction products could also be used as fuel.

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