Preamble
The challenge of fusion by magnetic confinement is to produce a large quantity of energy in complete safety using very little fuel.
In theory, the fusion of less than a kilogram a day of deuterium and tritium would produce the heat needed to generate 1,000 MW of electricity continuously, equivalent to what is produced today in a thermal power station using around 5,000 tonnes of fossil fuels1. In theory, the fusion of less than one kilogram of deuterium and tritium per day would produce the heat needed to generate 1,000 MW of continuous electricity, equivalent to what is produced today in a thermal power station using around 5,000 tonnes of fossil fuels1. The fuel for fusion is abundant and evenly distributed across the planet; it could be produced from seawater.
The fusion of deuterium and tritium (D-T) produces a helium nucleus and a neutron, and releases energy. In a tokamak, the helium nucleus remains confined in the plasma where it releases its energy by collision. Around 80% of the energy produced by the reaction is carried out of the plasma by the neutron. It is absorbed by the walls of the tokamak, transforming it into heat. This heat can be recovered to produce electricity.
Nuclear fission and fusion
The nucleus of an atom is made up of neutrons and protons, which are held together by nature’s most intense force: the strong interaction, responsible for ‘nuclear binding energy’. This energy can be released in two ways:
- or by breaking heavy nuclei → this is known as nuclear fission;
- or by fusing light nuclei → this is known as nuclear fusion.
1. A 1,000 MW PWR (pressurised water reactor) nuclear reactor consumes around 25 tonnes of fuel per year.