Fusion is the process that powers the sun and the stars. Since the 1950s, scientists and engineers in the United States and around the world have been conducting fusion research in pursuit of the creation of a new energy source for our planet and to further our understanding and control of plasma, the fourth state of matter that dominates the known universe. Generating power through nuclear fusion holds the tantalizing promise of unlimited supplies of clean energy. By the middle of the next century, the world's population will double, and energy demand will triple. This will be due in large part to the industrialization and economic growth of developing nations. The continued use of fossil fuels (coal, oil, and natural gas) will rapidly deplete these limited and localized natural resources. Fusion is perhaps the only option for a truly sustainable, long-term energy source. The fuel is virtually inexhaustible and readily available throughout the world.
The primary fuel used in fusion reactions is a form of hydrogen, which is easily extracted from ordinary water. Researchers claim that the hydrogen isotopes in one gallon of water would yield the equivalent energy of three hundred gallons of gasoline. Solar and renewable energy technologies will also play a role in our energy future. Although they are inherently safe and feature an unlimited fuel supply, they are geographically limited, climate dependent, and unable to meet the energy demands of a populous and industrialized world. Fusion energy would complement renewable energy technologies, which are environmentally attractive but probably do not have the capacity to power large cities and industries. Fusion power would not contribute to global warming, acid rain, or other forms of air pollution, nor would it create long-lived radioactive waste. The taming of fusion energy, however, is proving to be a formidable task. Steady progress has been made, but there are still scientific and technological advances that have to be made before the dream of commercial electricity production will become a reality.
What is Fusion
Fusion is the power source of the sun and the stars. It is the reaction in which two atoms of hydrogen combine together, or fuse, to form an atom of helium. In the process, some of the mass of the hydrogen is converted into energy. This is a nuclear reaction and results in the release of large amounts of energy. In a fusion reaction, the total mass of the resultant nuclei is slightly less than the total mass of the original particles. This difference is converted to energy as described by Einstein's famous equation, E = [mc.sup.2]. The easiest fusion reaction to make happen is to combine deuterium (heavy hydrogen) with tritium (heavy-heavy hydrogen) to make helium and a neutron. See Figure 1.
[FIGURE 1 OMITTED]
Deuterium and tritium are both isotopes of hydrogen. An isotope is a form of an atomic element that has a different mass from the normal element because of a different number of neutrons in the atomic nucleus. Deuterium and Tritium are considered heavy isotopes of hydrogen because they have one electron and one proton, but one and two neutrons, respectively (Internet Plasma, 2004). Deuterium is abundant in ordinary water. Tritium can be produced by combining the fusion neutron with the abundant light metal lithium, which is found in the earth's crust. The result is fusion energy that is virtually inexhaustible (General Atomics, 2004).
How Does Fusion Work?
To make fusion happen, the atoms of hydrogen must be heated to very high temperatures (100 million degrees) so that they become ionized (forming a plasma) and have sufficient energy to fuse and then be held together (confined) long enough for fusion to occur. These simultaneous conditions are represented by a fourth state of matter known as plasma. In a plasma, electrons are stripped from their nuclei. A plasma therefore consists of charged particles, ions, and electrons (Internet Plasma, 2004). …