Nuclear+Fusion+Energy

Christine Chung, Bernice Go, Karen Chu


 * Nuclear Fusion Energy **

**Introduction** Nuclear fusion is the process by which lighter nuclei combine to form a heavier nucleus. Nuclear fusion is the main energy source that fuels stars, such as our own sun. The opposite of a fusion reaction is a fission reaction, in which an atom is divided.


 * History **

The research of nuclear fusion originated from the discoveries of the structures of atoms. In 1920, Arthur Eddington, a British astrophysicist, was the first to suggest that stars gained their energy from nuclear fusion of hydrogen to helium. In 1939, Hans A. Bethe, a physicist from Germany, noticed that fusion reactions released energy when combining hydrogen nuclei and deuterium. He also proposed that the sun's main source of energy was nuclear fusion.

In the 1950s, the first man-made nuclear reaction was made by Americans by adding deuterium and tritium to a fission reaction. This was the basis for the hydrogen bomb. In 1952, the United States detonated the first nuclear weapon, the hydrogen bomb. It released as much energy as 10 million tons of TNT with a fireball 3 miles wide. In 1968, a device was designed by Philo T. Farnsworth to create nuclear fusion. In 1978, the conditions of fusion were produced in a fusion reactor in scale model for the first time. In 1989, two scientists were able to create nuclear fusion at roomtemperature. In 2002, US government scientist Rusi Taleyarkhan claimed that he had created nuclear fusion with sound waves. In 2005, American scientists found that they could create fusion energy with a small change in temperature of a crystal. They were developing a small, handheld fusion device that would generate fusion energy when warmed in the palm of one's hand or placed in ice cold water. This new crystal fusion method would not be useful for generating energy, but rather to fuse deuterium to generate neutrons which can be used to detect land mines, oil, explosives and nuclear materials.

In order for a nuclear fusion reaction to occur, several conditions must be met. First of all, nuclear fusion can only occur at very high temperatures, explaining why nuclear fusion can occur on the sun. The second condition is that the substances particip ating in the nuclear reaction must be in the plasma state. The plasma state is usually a gas with ionized molecules or atoms. There are two types of nuclear fusion. One type maintains the number of protons and neutrons, while the other types involves conversions between protons and neutrons. If two positively-charged substances were to be brought together, they would eventually repel each other due to the similar charges. However, this is overcome in nuclear fusion as the energy in the fast bombarding of the two nuclei overcomes the repulsion. A heavier nucleus will yield more nuclear energy. However, if the elements of nuclear fusion are too heavy, the reaction will instead use up energy rather than releasing it. The energy that is released in nuclear fusion is called the binding energy.
 * Explanation **

As seen in the image on the right, deuterium and tritium are "fused" together, which results in a release of energy, as well as a helium atom (which has a heavier nucleus) and a single neutron.

There are two methods of harnessing nuclear energy: magnetic confinement and inertial confinement. Tokamak, which is the magnetic confinement method, was first developed in the USSR. It is a ring-shaped fusion reactor that prevents little energy loss. The plasma does not touch the walls of the chamber because of the magnetic force, which acts as a barrier field. This field also helps heat up the plasma. Nuclear fusion by method can be self-sustaining; however, it has not been achieved and it probably will not be possible for the near future.

The second method is "laser fusion", which is inertial confinement. Laser beams compress a fuel "pellet" to increase particle density and temperature. Inertial confinement deals with higher particle densities and shorter periods of time than magnetic confinement. Though laser fusion is a possible implementation of nuclear fusion on Earth, it has not been demonstrated successfully yet. Critical Analysis

Advantages ** Deuterium, one of the main components of nuclear reactions, is much cheaper than the materials required for nuclear fission. This is because it is a "limitless" source of fuel, as in, it is abundant in the ocean. It would potentially be the permanent solution to the problem of the present rapid depletion of chemically valuable fossil fuels. Also, deuterium is used instead of uranium is because it does not produce radioactive waste, which means that there is no worry about constructing buildings to house the waste.

Using nuclear fusion will not produce CO2 or other emissions, which means that it will not cause acid rain, further damage ozone layer or increase the speed of global warming. Also, it has lower land use and environmental impact than many other forms of renewable en ergy, as large amounts of energy can be produced from smaller amounts of fuel. The possibility of a reactor accident is minimal, as the amount of fuel in the system is very small to cause much damage. As well, nuclear power is not very expensive to produce and costs the same amount as coal production. Disadvantages ** Nuclear fusion can only happen under very high temperatures (10 to 15 million Kelvin). Thus, man-made nuclear reactions are very difficult to achieve. Even if nuclear fusion were to occur, there is currently no material that can withstand such high temperatures. Attempts at nuclear fusion at room temperature (called "cold fusion" - combining deuteron during the electrolysis of water) have been proven unsuccessful thus far. Scientists would also have to consider the amount of output energy to be greater than the input energy used to control the temperature of the fusion process. Benefits must outweigh the costs, or else nuclear fusion will not be beneficial or efficient.

​As well, energy created in nuclear fusion cannot be used directly in everyday lives. Instead, the energy must be converted into other types of useful energy, such as electrical energy, adding an extra step that could be eliminated using other sources of energy. There are also economic issues regarding nuclear fusion, as it is hard to predict how it can compete with other energy sources in the future. It is estimated that direct fusion electricity will be very expensive because it relies heavily on the availability of plants and the amount of time each plant is shut down for maintenance or component replacements. Compared to current sources of energy, fusion electricity will be much more expensive because of the cost of fusion plant investments. As well, some analysts think that fusion energy would not be of much use to third world countries because of the large costs and lack of advanced infrastructure and base knowledge.

//An Experiment to Save the World.// Web. 21 May 2010. .
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