Fusion energy

How fusion works

In a fusion reaction, energy is released when two light atomic nuclei are fused together to form one heavier atom. This is the process that provides the energy powering the Sun and other stars, where hydrogen nuclei are combined to form helium.

To achieve high enough fusion reaction rates to make fusion useful as an energy source, the fuel (two types of hydrogen – deuterium and tritium) must be heated to temperatures over 100 million degrees Celsius. At these temperatures the fuel becomes a plasma.

This incredibly hot plasma is also extremely thin and fragile, a million times less dense than air. To keep the plasma from being contaminated and cooled by contact with material surfaces it is contained in a magnetic confinement system.

Illustration of the magnetic confinement fusion conceptMagnetic confinement is the approach that Culham and many other laboratories are researching to provide energy from fusion. A plasma of light atomic nuclei is heated and confined in a circular bottle known as a tokamak, where it is controlled with strong magnetic fields.

In a magnetic fusion device, the maximum fusion power is achieved using deuterium and tritium. These fuse to produce helium and high-speed neutrons, releasing 17.6MeV (megaelectron volts) of energy per reaction. This is approximately 10,000,000 times more energy than is released in a typical chemical reaction. A commercial fusion power station will use the energy carried by the neutrons to generate electricity. The neutrons will be slowed down by a blanket of denser material surrounding the machine, and the heat this provides will be converted into steam to drive turbines and put power on to the grid.

Animation of the fusion reaction

(Courtesy of www.euro-fusion.org)