Nuclear Energy

NUCLEAR ENERGY (URANIUM) ENERGY FROM ATOMS Nuclear Energy is Energy from Atoms Nuclear Fuel- Uranium Nuclear Power Plants Generate Electricity Types of Reactors Nuclear Power and the Environment links page recent statistics NUCLEAR ENERGY IS ENERGY FROM ATOMS Nuclear energy is energy in the nucleus (core) of an atom. Atoms are tiny particles that make up every object in the universe. There is enormous energy in the bonds that hold atoms together. Nuclear energy can be used to make electricity. But first the energy must be released. It can be released from atoms in two ways: nuclear fusion and nuclear fission. In nuclear fusion, energy is released when atoms are combined or fused together to form a larger atom. This is how the sun produces energy. In nuclear fission, atoms are split apart to form smaller atoms, releasing energy. Nuclear power plants use nuclear fission to produce electricity. NUCLEAR FUEL - URANIUM The fuel most widely used by nuclear plants for nuclear fission is uranium. Uranium is nonrenewable, though it is a common metal found in rocks all over the world. Nuclear plants use a certain kind of uranium, U-235, as fuel because its atoms are easily split apart. Though uranium is quite common, about 100 times more common than silver, U-235 is relatively rare. Most U.S. uranium is mined, in the Western United States. Once uranium is mined the U-235 must be extracted and processed before it can be used as a fuel. During nuclear fission, a small particle called a neutron hits the uranium atom and it splits, releasing a great amount of energy as heat and radiation. More neutrons are also released. These

neutrons go on to bombard other uranium atoms, and the process repeats itself over and over again. This is called a chain reaction.

NUCLEAR POWER PLANTS GENERATE ELECTRICITY Nuclear power accounts for about 19 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 2005, there were 66 nuclear power plants(composed of 104 licensed nuclear reactors) throughout the United States. Most power plants burn fuel to produce electricity, but not nuclear power plants. Instead, nuclear plants use the heat given off during fission as fuel. Fission takes place inside the reactor of a nuclear power plant. At the center of the reactor is the core, which contains the uranium fuel. The uranium fuel is formed into ceramic pellets. The pellets are about the size of your fingertip, but each one produces the same amount of energy as 150 gallons of oil. These energy-rich pellets are stacked end-to-end in 12-foot metal fuel rods. A bundle of fuel rods is called a fuel assembly. Fission generates heat in a reactor just as coal generates heat in a boiler. The heat is used to boil water into steam. The steam turns huge turbine blades. As they turn, they drive generators that make electricity. Afterward, the steam is changed back into water and cooled in a separate structure at the power plant called a cooling tower. The water can be used again and again. TYPES OF REACTORS Just as there are different approaches to designing and building airplanes and automobiles, engineers have developed different types of nuclear power plants. Two types are used in the United States: boiling-water reactors (BWRs), and pressurized-water reactors (PWRs). In the BWR, the water heated by the reactor core turns directly into steam in the reactor vessel and is then used to power the turbine-generator. In a PWR, the water passing through the reactor core is kept under pressure so that it does not turn to steam at all -- it remains liquid. Steam to drive the turbine is generated in a separate piece of equipment called a steam generator. A steam generator is a giant cylinder with thousands of tubes in it through which the hot radioactive water can flow. Outside the tubes in the steam generator, nonradioactive water (or clean water) boils and eventually turns to steam. The clean water may come from one of several sources: oceans, lakes or rivers. The radioactive water flows

back to the reactor core, where it is reheated, only to flow back to the steam generator. Roughly seventy percent of the reactors operating in the U.S. are PWR. Nuclear reactors are basically machines that contain and control chain reactions, while releasing heat at a controlled rate. In electric power plants, the reactors supply the heat to turn water into steam, which drives the turbine-generators. The electricity travels through high voltage transmission lines and low voltage distribution lines to homes, schools, hospitals, factories, office buildings, rail systems and other users.

NUCLEAR POWER AND THE ENVIRONMENT Like all industrial processes, nuclear power generation has by-product wastes: spent (used) fuels, other radioactive waste, and heat. Because nuclear generated electricity does not emit carbon dioxide into the atmosphere, nuclear power plants in the U.S. prevent emissions of about 700 million metric tons of carbon dioxide. This is nearly as much carbon dioxide as is released from all U.S. passenger cars combined. Spent 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 regulation that govern their disposal so they will not come in contact with the outside environment. On the other hand, the spent fuel assemblies are highly radioactive and must initially be stored in specially designed pools resembling large swimming pools (water cools the fuel and acts as a radiation shield) or in specially designed dry storage containers. An increasing number of reactor operators now store their

older and less spent fuel in dry storage facilities using special outdoor concrete or steel containers with air cooling. The United States Department of Energy's long range plan is for this spent fuel to be stored deep in the earth in a geologic repository, at Yucca Mountain, Nevada.

Last Revised: November 2006 Sources: Energy Information Administration, Annual Energy Review 2005, July 2006, Energy Information Administration, Office of Coal, Nuclear, Electric, and Alternative Fuels, October 2005.

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Nuclear Fission: Nuclear fission is when an atomic nucleus splits into two or more pieces creating the energy for nuclear power plants or weaponry. This splitting is often triggered by the absorption of a neutron travelling at high speed. Uranium-235 and Plutonium-239 are readily fissile and can release lots of energy. When they split they will release more neutrons, a property that allows for neutron chain reactions. Since Plutonium-239 tends to occur artificially from Uranium-235 it is less common. Neutron Chain Reactions: Neutron chain reactions are required to produce sufficient energy for nuclear weaponry and power. When a readily fissile material (e.g. Uranium-235, Plutonium-239) undergoes fission it produces more neutrons. The neutrons produced are supposed to cause more atoms to undergo fission. With enough of these atoms present enough energy can be produced to power nuclear reactors and even weapons.

Nuclear Energy The sun and stars are seemingly inexhaustible sources of energy. That energy is the result of nuclear reactions, in which matter is converted to energy. We have been able to harness that mechanism and regularly use it to generate power. Presently, nuclear energy provides for approximately 16% of the world's electricity. Unlike the stars, the nuclear reactors that we have today work on the principle of nuclear fission. Scientists are working like madmen to make fusion reactors which have the potential of providing more energy with fewer disadvantages than fission reactors. Production

Changes can occur in the structure of the nuclei of atoms. These changes are called nuclear reactions. Energy created in a nuclear reaction is called nuclear energy, or atomic energy. Nuclear energy is produced naturally and in man-made operations under human control. 

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Naturally: Some nuclear energy is produced naturally. For example, the Sun and other stars make heat and light by nuclear reactions. Man-Made: Nuclear energy can be man-made too. Machines called nuclear reactors, parts of nuclear power plants, provide electricity for many cities. Man-made nuclear reactions also occur in the explosion of atomic and hydrogen bombs.

Nuclear energy is produced in two different ways, in one, large nuclei are split to release energy. In the other method, small nuclei are combined to release energy. For a more detailed look at nuclear fission and nuclear fusion, consult the nuclear physics page.

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Nuclear Fission: In nuclear fission, the nuclei of atoms are split, causing energy to be released. The atomic bomb and nuclear reactors work by fission. The element uranium is the main fuel used to undergo nuclear fission to produce energy since it has many favorable properties. Uranium nuclei can be easily split by shooting neutrons at them. Also, once a uranium nucleus is split, multiple neutrons are released which are used to split other uranium nuclei. This phenomenon is known as a chain reaction.

Fission of uranium 235 nucleus. Adapted from Nuclear Energy. Nuclear Waste*. 

Nuclear Fusion: In nuclear fusion, the nuclei of atoms are joined together, or fused. This happens only under very hot conditions. The Sun, like all other stars, creates heat and light through nuclear fusion. In the Sun, hydrogen nuclei fuse to make helium. The hydrogen bomb, humanity's most powerful and destructive weapon, also works by fusion. The heat required to start the fusion reaction is so great that an atomic bomb is used to provide it. Hydrogen nuclei fuse to form helium and in the process release huge amounts of energy thus producing a huge explosion.

Milestones in the History of Nuclear Energy

Amore in depth and detailed history of nuclear energy is on the nuclear past page. 

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December 2, 1942: The Nuclear Age began at the University of Chicago when Enrico Fermi made a chain reaction in a pile of uranium. August 6, 1945: The United States dropped an atomic bomb on Hiroshima, Japan, killing over 100,000.

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August 9, 1945: The United States dropped an atomic bomb on Nagasaki, Japan, killing over 40,000. November 1, 1952: The first large version of the hydrogen bomb (thousands of times more powerful than the atomic bomb) was exploded by the United States for testing purposes. February 21, 1956: The first major nuclear power plant opened in England.

Advantages of Nuclear Energy 

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The Earth has limited supplies of coal and oil. Nuclear power plants could still produce electricity after coal and oil become scarce. Nuclear power plants need less fuel than ones which burn fossil fuels. One ton of uranium produces more energy than is produced by several million tons of coal or several million barrels of oil. Coal and oil burning plants pollute the air. Well-operated nuclear power plants do not release contaminants into the environment.

Disadvantages of Nuclear Energy

The nations of the world now have more than enough nuclear bombs to kill every person on Earth. The two most powerful nations -- Russia and the United States -- have about 50,000 nuclear weapons between them. What if there were to be a nuclear war? What if terrorists got their hands on nuclear weapons? Or what if nuclear weapons were launched by accident? 

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Nuclear explosions produce radiation. The nuclear radiation harms the cells of the body which can make people sick or even kill them. Illness can strike people years after their exposure to nuclear radiation. One possible type of reactor disaster is known as a meltdown. In such an accident, the fission reaction goes out of control, leading to a nuclear explosion and the emission of great amounts of radiation.  In 1979, the cooling system failed at the Three Mile Island nuclear reactor near Harrisburg, Pennsylvania.

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Radiation leaked, forcing tens of thousands of people to flee. The problem was solved minutes before a total meltdown would have occurred. Fortunately, there were no deaths.  In 1986, a much worse disaster struck Russia's Chernobyl nuclear power plant. In this incident, a large amount of radiation escaped from the reactor. Hundreds of thousands of people were exposed to the radiation. Several dozen died within a few days. In the years to come, thousands more may die of cancers induced by the radiation. Nuclear reactors also have waste disposal problems. Reactors produce nuclear waste products which emit dangerous radiation. Because they could kill people who touch them, they cannot be thrown away like ordinary garbage. Currently, many nuclear wastes are stored in special cooling pools at the nuclear reactors.  The United States plans to move its nuclear waste to a remote underground dump by the year 2010.  In 1957, at a dump site in Russia's Ural Mountains, several hundred miles from Moscow, buried nuclear wastes mysteriously exploded, killing dozens of people. Nuclear reactors only last for about forty to fifty years.

The Future of Nuclear Energy

Some people think that nuclear energy is here to stay and we must learn to live with it. Others say that we should get rid of all nuclear weapons and power plants. Both sides have their cases as there are advantages and disadvantages to nuclear energy. Still others have opinions that fall somewhere in between. What do you think we should do? After reviewing the pros and cons, it is up to you to formulate your own opinion. Read more about the politics of the issues or go to the forum to share your own opinions and see what others think.

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