Nuclear fusion

Nuclear fusion is the process by which multiple like-charged atomic nuclei join together to form a heavier nucleus. It is accompanied by the release or absorption of energy.

An energy option for the future?

Nuclear fusion is one of the energy options for the future. As all other energy generation options, it has its pros and contras. Making a policy choice in favour of one or the other energy option requires defining one's stance on:

• The importance of climate change and the impact of the burning of fossil fuels
• Quantitative estimates of the energy generation potential of each of the available energy options
• Estimates of global population growth and expectations regarding future energy demand, taking into account the rapidly rising energy needs of emerging economies
• The relative importance of the environmental impact of each of the energy options
• Social threats associated with each energy option: e.g., nuclear proliferation, or the threats associated with politically unstable energy supply regions
• The social acceptability of each energy option
• The relative economic cost of each of the energy options (contemplating the complete energy generation trajectory, including environmental damage and clean-up)
• Opportunities offered by the energy options in terms of, e.g., economic stimulation and employment

Making the correct choice requires studying each of these complex issues and somehow balancing the risks and opportunities involved. For some of them, the future evolution can be predicted with some confidence, but for others the predictions are hotly debated.

Most likely, energy generation in the near future will be based on a mix of many options, that will vary in accord with local economic, environmental, and social conditions.

In the case of fusion, there is an additional complication due to the fact that its implementation is not immediate, and that its eventual implementation is subject to the solution of a number of technical problems. The current consensus it that while the technical challenges are formidable, they can be overcome. Thus, the main discussion regarding fusion as an energy option is not about its technical feasibility, but about the timescales for implementation. While increased investment and improved focus of the current research efforts can certainly help to speed up progress, even under optimal conditions the time needed to achieve the first delivery of fusion-produced energy to the electricity grid is considerable, and it is unlikely that fusion can contribute to solving the short-term energy crisis (in the coming decades). Fusion must therefore be considered an energy option for the medium to long term.

A Nuclear Fusion reactor

The nuclear reaction that is easier to obtain is based on the deuterium-tritium (DT) reaction. A nuclear power reactor delivering 1GW of electric power to the network would aproximately consume 200 kg of Tritium a year. The current world reserves are of about 29 kg of tritium. Then, a nuclear fusion reactor must provide its own fuel. This is obtained using the so called breeders. Tritium breeders capture the neutrons comming from the nuclear fusion reactions and generate tritium that can be used as fuel for the reactor. The breeding reaction is based on transmutation of Lithium, according to the reaction

n + Li_6 -> T + He n + Li_7 -> T + He + n

http://www-fusion.ciemat.es/fusionwiki/index.php/TECNO_FUS

The need for new materials for Fusion

A nuclear power reactor delivering 1GW of electric power to the network would generate 1.3e21 neutrons per second. This flux will destroy any conventional iron in less than a year. For this reason, a programm for material testing under heavy neutron flux has been launched. The programm, called IFMIF, aims to the development of fast neutron generation facility.

http://www-fusion.ciemat.es/fusionwiki/index.php/TechnoFusi%C3%B3n

See also

• Timeline of nuclear fusion