The science behind fusion
To produce fusion, hydrogen isotopes (deuterium and tritium) must be heated to very high temperatures and the resulting hydrogen plasma must be confined by using powerful magnets. The most successful devices developed to achieve this are called tokamaks (a Russian word for a torus-shaped magnetic chamber).
Since coming into operation in 1983, the JET tokamak has established itself as the world’s foremost fusion experiment. The pinnacle of its achievements has been experiments which produced up to 16MW of fusion power for a few seconds. Together with other devices in Europe and internationally, JET is now defining the operational parameters and refining the configuration for a tokamak line of future fusion power stations.
Certain key high-tech components – such as large superconducting coils to generate strong electromagnet fields – are necessary to confine the 150 million degrees Celsius hot plasma needed to produce fusion power. Key components have been designed and tested and are now ready for production for the next step in fusion, ITER.
Other systems required for the continuous operation of fusion reactors include systems to extract helium ‘ash’ and impurities from the reactor plasma. Refuelling systems, robust diagnostics and control systems are also required for the safe and accurate control of the reactor.
The future demonstration reactor capable of generating electricity (DEMO) requires the development of a ‘breeding blanket’ and of specific materials:
- The role of the blanket, which will surround the burn chamber in a future fusion reactor, is to breed tritium through a reaction of fusion neutrons with lithium compounds. This tritium can then be directly fuelled in the reactor thereby removing the need to transport radioactive materials. The testing of breeding blanket modules in ITER is foreseen.
- Low activation and radiation resistant materials are needed for internal components of future reactors. A specific neutron source, such as the International Fusion Materials Irradiation Facility (IFMIF), which is currently being studied within the IEA framework, is also required to qualify these materials.
Safe and socially acceptable In parallel with the technical aspects of this research, extensive safety and socioeconomic studies have comprehensively examined the impact of fusion energy. This work suggests that future fusion power stations are safe to operate and will pose neither major risks to the population nor significant long-term environmental burdens.
Given the positive initiatives to date to reduce greenhouse gas emissions, it is possible that fusion power plants could be introduced by the middle of this century and could grow towards a significant share of electricity generation during the second half. The external (such as environmental) costs of fusion power systems are low and compare well with the projected external costs of other renewable technologies.