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. See Wikipedia: Nuclear fusion.

Energy options for the future

There exist a wide consensus that the current methods for energy production are unsatisfactory in the long term, due to contamination, the greenhouse effect, diminishing resources, etc. In order to decide what energy generation methods should be used, the pros and contras of each method should be considered carefully. Thus, 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.

In any case, the choice for any specific energy generation options should not be considered in isolation from other global issues, such as the exhaustion of natural resources, poverty, and overpopulation, but rather as an element in the general framework of sustainable development, since all these issues must be addressed to guarantee the establishment of a stable and livable society. In particular, it is important to be aware that any technological solution to the energy problem (as well as to, e.g., agricultural production levels) will only mean temporary relief if population growth is not controlled. The latter issue should therefore receive top priority in any effort to attain sustainable development.

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

Fusion as an energy option

Fusion undoubtedly offers some important advantages. Once operative, energy supply would be virtually limitless; greenhouse gas exhaust would be zero; nuclear waste and the danger of nuclear accidents would be strongly reduced (with respect to fission power plants), and nuclear proliferation problems would be small or inexistent. On the other hand, there are complications due to the very complex technology required and the radioactive activation of the reactor vessel components. A significant part of the latter complications are due to the projected use of D-T fuels (deuterium-tritium) in the first-generation fusion power plants, which is the fuel that is easiest to ignite, but which leads to intense neutron radiation. One may speculate that, if successful, a second generation of fusion power plants can be developed that runs on aneutronic fuels (such as D-D), leading to a strong reduction of the problems associated with radioactivity.

As compared to other energy options, fusion has 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 fusion reactor

The fusion reaction that is easiest to obtain is the deuterium-tritium (DT) reaction. A fusion power reactor delivering 1 GW of electric power to the network would approximately consume 200 kg of Tritium a year. The current world reserves are about 29 kg of tritium. Thus, a nuclear fusion reactor must provide its own fuel. This is achieved using so-called breeders. Tritium breeders capture the neutrons originating from nuclear fusion reactions, generating tritium that can be used as fuel for the reactor. For more information: TECNO_FUS.

The need for new materials for Fusion

A fusion power reactor delivering 1GW of electric power to the network would generate 1.3 × 10²¹ neutrons per second. This flux will make any conventional iron become brittle in less than a year. For this reason, a program for testing materials under intense neutron fluxes has been launched. The aim of the IFMIF program is to develop a fast neutron generation facility.

Also in Spain, a program for material testing has been launched recently: TechnoFusión.

See also

• Timeline of nuclear fusion
• The ITER project