• Question: how is nuclear energy created ?

    Asked by anon-201743 to Sophia, Sarah, Meirin, George, Emily, Andy on 13 Mar 2019.
    • Photo: Emily Lewis

      Emily Lewis answered on 13 Mar 2019:

      Nuclear energy is created in nuclear fission when you get a really heavy nucleus like uranium and you fire a neutron at it to make it split apart.
      The two split parts are called daughter nuclei, and if you weighed them compared to the uranium nucleus at the beginning you’d see that even the both of them together are lighter than what you started with. So some of your mass has gone missing, where has it gone?!
      It has been converted into energy! By einsteins equation E=mc ^2 (energy = mass x speed of light squared), the missing mass is converted into the kinetic energy of the new nuclei and some gamma rays released. Because the c squared term is so big, there is loads of energy.
      We convert this energy into electricity and use it to power our homes 🙂

    • Photo: Andy Buckley

      Andy Buckley answered on 13 Mar 2019:

      Most of our ways of generating power — apart from renewables, which don’t have enough energy density to do it — involve boiling water to run huge, efficient steam-turbine electrical generators. That’s the same for nuclear fission, and will be the case for nuclear fusion if we can make it work.

      Fundamentally, these methods are about releasing energy bound up in materials by turning them into other materials. This is the case when we burn fossil fuels, which are molecular systems with lots of binding energy and the transformation is through chemical reactions, and for nuclear fuels where we’re instead transforming between nuclei with high and low binding energies. Nuclear fission goes from heavy nuclei to less-heavy nuclei, and fusion from light to less-light ones, but in both cases it’s about releasing some of that binding energy.

      It turns out that small sizes are sort-of equivalent to high-energies, so the fact that nuclei are a million times smaller than atoms means that nuclear binding energies are around a million times higher than chemical ones. So we can get the same energy with far less fuel… but have to work harder to make sure that huge energy is released in a controlled way.

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