Getting the Energy from Atoms
Nuclear energy has many uses (one of the best known uses is to make electricity), but first the energy must be released from the atom. It can be released in two ways: nuclear fusion and nuclear fission.
In nuclear fusion, energy is released when atoms combine, or fuse, together to form a larger atom. The sun produces nuclear energy through fusion.
In nuclear fission, scientists use a nuclear reactor to shoot a neutron into a uranium atom and split it and release its energy as heat and radiation. As the atom breaks open, more neutrons are released. These neutrons bump into and break open other uranium atoms. The process in the nuclear reactor is called a “chain reaction” because it repeats itself many times.
Nuclear reactors are machines that control chain reactions and capture the heat that is released. In nuclear power (electric) plants, the reactors supply the heat to boil water into steam. The steam then turns huge turbine blades. As they turn, they drive generators that make electricity.
After the steam passes through the turbine blades, it changes back to water as it cools. The warm water is cooled more in a structure called a “cooling tower” at the power plant. The water is recycled and used again and again.
Engineers have developed different types of nuclear plants to produce electricity. In the United States, the two types of nuclear power plants are called “boiling-water reactors” (BWRs), and “pressurized-water reactors” (PWRs).
Nuclear power accounts for about 20 percent of the total net electricity generated in the United States, about as much as the electricity used in California, Texas and New York, the three states with the most people. In 2006, the United States had 66 nuclear power plants (35 boiling water reactors, 69 pressurized water reactors) comprising 104 licensed nuclear reactors in 31 states.
Compared to electricity generated by burning fossil fuels, nuclear energy is clean. Nuclear power plants produce no air pollution or carbon dioxide, but a small amount of emissions result from processing the uranium that is used in nuclear reactors. Like all industrial processes, nuclear power generation has by-product wastes: used fuels, other radioactive waste, and heat.
Used fuels and other radioactive wastes are the principal environmental concern for nuclear power. Most nuclear waste is low-level radioactive waste. It consists of ordinary tools, protective clothing, wiping cloths, and disposable items that have been contaminated with small amounts of radioactive dust or particles. These materials are subject to special regulations that govern their disposal to prevent them from coming in contact with the outside environment.
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