• Question: Why is fusion power not sustainable at the present moment?

    Asked by Harry Oo to Connor, Jillian, Lidunka, Sarah, Steven on 21 Jun 2015.
    • Photo: Steven Thomson

      Steven Thomson answered on 21 Jun 2015:

      To get it working, fusion has to become a chain reaction – every pair of atoms that fuses has to cause another fusion reaction afterwards. This can be done by using the energy from one fusion reaction to heat up the fuel (the un-fused atoms) so they have enough energy to smash into each other and fuse together.

      In the current best experiments, lasers are used to provide enough heat to kickstart the fusion reaction. Keeping the laser switched on would use more power than the fusion reaction generates, so it has to be switched off quickly. Once the laser is switched off, though, there isn’t enough energy released to keep the reaction burning. It cools down too quickly and fusion stops. The problem right now is how to retain this heat long enough for fusion to keep happening.

      There’s some exciting news out there though – Lockheed Martin announced last year that they expect to have a working fusion reactor prototype by 2017, and a commercial product by 2022. I’m a little sceptical, but if it works, it’ll be amazing!

    • Photo: Connor Macrae

      Connor Macrae answered on 23 Jun 2015:

      The key problem right now is turbulence, that is basically a loss of energy from any fusion experiments. A funny form of turbulence called the rayleigh taylor instability causes mixing of layers in fusion experiments using lasers, whilst experiments using tokomaks (big rings filled with plasma!) suffer loss of confinement at points in the induced magnetic fields. These are issues scientists are working to minimise with the hope of building a stable reactor that produces more energy than is required to power it.