The process of nuclear fusion - evident in stars, including the Sun - releases enormous amounts of energy. It occurs when the nuclei of lighter elements (such as hydrogen) are fused together at extremely high temperatures and pressures to form heavier elements (such as helium). Three known isotopes of hydrogen are: hydrogen (H), deuterium (D), and tritium (T). The nuclei of all three contain one proton, which characterizes them as forms of the element hydrogen. The deuterium nucleus has one neutron and the tritium nucleus has two neutrons. In each case, the neutral atom has one electron outside the nucleus to balance the charge of the single proton. Since the nuclei carry positive charges, they normally repel one another. The higher the temperature, the faster the atoms or nuclei move. When they collide at these high speeds, they overcome the force of repulsion of the positive charges, and the nuclei fuse causing a release of energy. The difficulty in producing fusion energy has been to develop a device that can heat the D-T fuel to a high enough temperature and confine it for a long enough time so that more energy is released through fusion reactions than is used for heating.
Fusion energy is an important, long-range element of the nation's energy strategy because of its many potential advantages as an energy resource. Fusion energy technologies in the 21st century could help to enhance the Nation's energy, provide an environmentally acceptable alternative to fossil fuel combustion, and help ensure continued economic growth through reliable electricity supply. Advanced research and development in fusion energy could provide high-technology spin-offs in such areas as superconducting magnets; high speed computing; high power lasers; electronic diagnostic equipment; and high power, high frequency radio sources.
Advantages of Fusion Energy
Factors of a Controlled Fusion Reaction
The major fuel for a fusion reactor, deuterium, can be extracted from ordinary water which contains more than 10 million tons of deuterium. Tritium is produced from lithium, which is available from land deposits or from seawater. This fuel could satisfy the world's power requirements for thousands of years.
In order to release energy for production of electricity, the deuterium-tritium fuel must be heated to about 100 million degrees Celsius. This high temperature is more than six times hotter than the interior of the sun, which is estimated to be 15 million degrees Celsius.
The problem with creating high temperatures is confining the deuterium and tritium under such extreme conditions. Charged particles in the high-temperature plasma are confined by a magnetic field preventing them from striking the vessel walls and forcing them to follow spiral paths along the field lines. Without a magnetic field, the charged particles move in straight lines and in random directions striking the walls of a containment vessel - cooling the plasma and interrupting fusion reactions.
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